The growing problem of invasive mussel species in the Great Lakes has prompted researchers to create innovative solutions aimed at preventing their spread to inland lakes and reservoirs. These mussels attach to various surfaces, both in the upper (epilimnion) and deeper (hypolimnion) layers of lakes. During the winter months, mussels will die off, leaving the large structures constructed of their shells on the lakebed. Their colonies recede into the deeper waters where water temperature is warmer than the icy conditions on the surface. In the spring and summer, the mussels return shoreward, recoating the left-behind shell structures and adding layers of shell material to the submerged landscape. Juvenile mussels are released from fish hosts and can migrate or float to nearly any structure or vehicle, with bilge water from ships often transporting them to new locations. Once attached, mussels begin their reproductive cycle, and this adherence is key to their spread. If prevented from attaching, they are forced to relocate, increasing competition for space and resources.

To combat fouling, researchers have developed a clear, tri-cure hybrid silsesquioxane coating that is inexpensive, easy to apply, and safe for aquatic environments. When applied to glass or fiberglass, materials they readily attach to, this coating prevents the bonding of mussel proteins to surfaces, making them resistant to fouling. By coating boat hulls, boat owners can reduce mussel attachment, slowing the spread of invasives, saving on costly maintenance, reducing drag, and contributing to the protection of other aquatic ecosystems.

Introduction

Marine biofouling, which is the undesirable accumulation of microorganisms, plants, and animals on submerged surfaces, poses significant operational and environmental challenges to maritime industries and aquatic infrastructure.^1-3ĚýThe consequences of biofouling are far-reaching. It causes increased hydrodynamic drag on vessel hulls which reduces fuel efficiency and speed, while simultaneously contributing to higher greenhouse gas emissions.^4-7ĚýIn addition, biofouling accelerates the corrosion of submerged metal and concrete surfaces, clogs pipelines in coastal and nuclear facilities, and disrupts water flow and nutrient exchange in aquaculture systems.^8,9

One of the most practical and effective strategies for mitigating biofouling is the use of protective surface coatings or coating additives. These are broadly classified into biocidal and nonbiocidal types. Biocidal coatings rely on the controlled release of toxic agents from a polymer matrix to prevent organism settlement and are considered antifouling coatings.¹⁰ĚýThe efficacy of such coatings is governed by the biocide’s release rate and its environmental compatibility that should ideally combine strong antifouling activity with low toxicity and moderate fresh and sea water solubility. Unfortunately, only a limited number of biocides meet these stringent requirements for safe and sustained marine use.¹¹

Nonbiocidal coatings primarily include fouling-resistant and fouling-release coatings (FRCs). Fouling-resistant coatings are typically based on hydrophilic polymers such as poly(ethylene glycol) (PEG) and zwitterionic materials, which prevent initial organism adhesion.¹²ĚýHowever, their tendency to swell in saline environments leads to poor mechanical performance. In contrast, FRCs utilize hydrophobic, low-surface-energy materials that allow weakly adhered organisms to be easily removed under mild shear forces. Polysiloxanes are commonly used as FRCs and offer excellent thermal and photochemical stability, though their long-term performance is limited by hydrolytic degradation. To overcome these limitations, hybrid organo-silicon coating systems have been developed. These systems integrate organic and inorganic elements to combine durability, antifouling characteristics, and environmental resilience.^13,14ĚýFor instance, R-alkoxysilanes, particularly methoxy and ethoxy variants, have long been employed to consolidate porous substrates like stone by forming crosslinked siloxane networks with the ratio [RSiO_3/2], or silsesquioxanes that also contain organic bridges. When incorporated into coatings, these networks offer benefits such as low thermal conductivity, oxidative resistance, and mechanical integrity.

Among silicon-oxygen-based coating systems derived from alkoxysilanes, tetraethoxysilane (TEOS) is a widely used precursor.^15,16ĚýHowever, its slow curing rate often necessitates acidic or basic catalysts and long reaction times. As an alternative, photocuring methods that utilize photoinitiators to trigger rapid organic polymerization under light have gained popularity for enabling fast curing without complex handling or component separation. Moreover, using R-functional trialkoxysilanes with epoxy, amine, thiol, or fluorocarbon side groups allows tailoring of surface adhesion, hydrophobicity, and internal stress relief within the final silsesquioxane-based coating.¹⁷

Bioinspired approaches have further guided the design of antifouling surfaces. Many plants and insects feature microstructured, waxy coatings that combine hydrophobicity with self-cleaning properties. Mimicking these strategies, coatings with nanoscale surface roughness and low-surface-energy materials (e.g., fluoropolymers) have been developed to enhance water repellency and reduce biological adhesion.

Polyurethane (PU) networks exhibit the outstanding mechanical strength, thermal stability, and solvent resistance that is required for use in high-performance coatings, adhesives, and composites. However, the most common way to form these polymer networks is to use hazardous isocyanate-functional molecules. Moisture-cure urethane silane polymers have recently been used to form hybrid PU networks, thereby mitigating end-user exposure to hazardous isocyanate during application. However, while the applicator is not exposed to isocyanates, they are nonetheless used to synthesize these polymers. High-oleic soybean oil (HOSBO) was chosen for use in hybrid binders to explore potential beneficial properties, mainly enhanced hydrophobicity and reduced viscosity, and as a U.S.-produced renewable chemical, the fatty acid groups offer beneficial properties. For this project, isocyanate-free polyurethane-silane binders were formed by first reacting diethanolamine with HOSBO to form fatty acid diols, followed by transcarbamation reactions to form urethane linkages. The polymers were then end-capped with various secondary aminoalkoxysilanes via subsequent transcarbamation reactions. Reaction of these polymers with atmospheric moisture resulted in crosslinked hybrid networks with siloxane linkages. Surface-free energy (SFE) as well as thermal and mechanical energy were explored.

Introduction

Crosslinked polymer networks are in numerous consumer and industrial products, ranging from coatings for medical devices to foams for seat cushions.^1-4ĚýThe chemistry for these networks typically involves urethane, urea, ether, and thioether chemistries.^5-7ĚýAmong these, polyurethane and polyurea networks remain the most widely studied due to their rapid and efficient formation at room temperature, the ability to modify the backbone structure, as well as their excellent thermal and mechanical properties.^8,9ĚýThe most common way to form polyurethane networks requires the use of hazardous isocyanates.⁸ĚýHowever, isocyanate exposure can lead to a myriad of health issues, including skin and eye irritation, symptoms of asthma, and sensitization upon exposure.^10,11

A way to synthesize crosslinked networks while avoiding isocyanates is to make networks with siloxanes where an alkoxysilane is used as a crosslinker. These urethane-siloxane polymers also have the advantage of producing crosslinked networks with enhanced properties from the sol-gel region.^12-16ĚýFor example, silane-terminated polyurethane and poly(urethaneimide) networks demonstrate improved thermal stability, good adhesion to metals, elastomeric properties, and excellent moisture resistance.^17-20

In addition to avoiding isocyanates, there is interest in the polyurethane field to shift from petrochemical to renewable biobased raw materials, particularly soybean oil.^21,22ĚýPolyurethane networks are not necessarily hydrophobic and often rely upon incorporation of other materials and segments to make hydrophobic material.²³ĚýThe addition of the fatty acid chains is predicted to enhance hydrophobicity. Other benefits from the fatty acid chain include reduced viscosity and, by using the high oleic oil, reduced yellowing with a high content of chains with a single unsaturated group. Hybrid urethane-siloxane vegetable oilbased polymers have even been formed through isocyanates^24-27Ěýand cyclic carbonate chemistry.^28-30ĚýThe isocyanate-based networks have the same toxicity issue of the nonhybrid polyurethane while the cyclic carbonate-based networks form pendant hydroxyl groups, which may limit any enhancement to hydrophobicity. Rather than use these methods, the ester linkages of the oil can be utilized to incorporate other organic functionalities, such as alcohols and diols, which can be further reacted.³¹

Herein, a method is provided to form polyurethane-silane networks that circumvents the use of isocyanates and incorporates renewable biobased materials. In this work, a safer acylation reagent, 1,1′-carbonyldiimidazole (CDI), was used to form the urethane functional groups. These acylating groups were used to attach the fatty acid-based diol, which is based on high-oleic soybean oil (HOSBO), to the alkoxysilane crosslinker and to add chain extenders. These compounds were then used as binders to form clear polyurethane-siloxane networks. To our knowledge, there are no reports of polyurethane-siloxane networks based on HOSBO. This method allows for greater control of structure of the binders. Chain extenders have been explored in the binders. Thermal, mechanical, and surface properties of the resulting crosslinked networks were determined using several analytical techniques and compared with those of a control network.

By Mariia Usiichuk, Vasylyna Kirianchuk, Oleg Shevchuk, Tetiana Shevtsova, and Andriy Voronov

The search for alternatives to petroleum-based materials in the polymer industry, driven by growing environmental concerns and limiting the availability of petroleum-based sources, is becoming increasingly critical. In this context, plant oils, with their renewable, biodegradable, and eco-friendly nature, have proven to be promising raw materials.¹ Recently, various approaches, including acrylation, epoxidation, and transesterification, have been developed to transform the triglycerides present in oils into polymerizable monomers, paving the way for the creation of biobased polymers with properties comparable to their petroleum-based analogs.² The flexibility in chemical modification enhances the potential applications of plant oil-derived monomers in various industries, including coatings.³

Coconut oil, in particular, is an attractive source for biobased monomer synthesis due to its unique composition, rich in medium (6 to 12 carbon atoms) saturated fatty acids such as lauric acid.⁴ This composition makes coconut oil highly valuable for producing additives, such as surfactants, where the shorter-chain fatty acids enhance key performance properties. However, the conversion of hydrogenated oils into surfactants typically involves multiple processing steps, which adds complexity to the overall production process.⁵

Our research group has developed an efficient one-step method to convert triglycerides from plant/vegetable oils into a library of plant oil-based acrylic monomers (POBMs), suitable for free radical polymerization.^6,7,8 It was shown that the incorporation of POBMs made from primarily unsaturated triglycerides provides several benefits to the resulting polymeric materials, including a plasticizing effect and controlled viscoelastic behavior. At the same time, plant oil-based monomeric fragments from saturated fatty acids in the oils facilitate the formation of ordered (crystalline) morphological polymeric domains. Such combination enables tailoring of the thermo-mechanical properties in a broad range and thus advances the performance of POBM-based polymeric materials. In this short communication, we elaborate on the highly saturated triglycerides effect by introducing recently synthesized coconut oil-based acrylic monomer (CCM) to broaden our technology of fabrication of biobased polymeric materials with tunable properties.

Synthesis and Characterization of Coconut Oil-based Acrylic Monomer

The composition of the coconut oil used as raw material was analyzed by mass spectrometry in order to assess the feasibility of monomer synthesis and relate the composition to the characteristics of the resulting polymers. The results indicated that the coconut oil contains over 90% saturated fatty acids (Table 1), which aligns well with existing literature.4 Additionally, the low iodine value 16 g/100 g found by titration confirms the saturated nature of used coconut oil.

The coconut oil was then converted into coconut oil-based acrylic monomer (CCM) using the one-step transesterification method described in our previous publications.6,7,8 As shown in Figure 1, coconut oil was reacted with N-(hydroxyethyl) acrylamide, yielding a mixture of monomers that feature a single acrylic double bond linked to fatty chain residues, where R₁, R₂, and R₃ represent fatty acid fragments corresponding to the oil chemical composition. The resulting product was purified according to the established methodology and then characterized.

FIGURE 1 The mechanism of the transesterification reaction.

The structure of the CCM was confirmed using FTIR and ¹H NMR spectroscopy (Figure 2). The FTIR spectrum indicates the incorporation of fatty acid acyl moieties to the acrylamide fragment. The presence of a strong NH absorption band between 3200 and 3400 cm^–1, along with the carbonyl (amide I) band at 1670 cm^–1 and the NH (amide II) band at 1540 cm^–1, confirms the bonding of the acrylamide group to the fatty acid fragment. Additionally, the presence of strong absorption bands observed at 1740, 1245, and 1180 cm^–1 confirms the ester nature of the CCM (Figure 2A).

According to the 1H-NMR spectrum (Figure 2B) of the CCM, characteristic peaks for the acrylic double bond protons are observed at 5.6-6.6 ppm along with the peaks corresponding to the protons of the ethylene linkage between the amide and ester groups (3.6 ppm and 4.20 ppm), and signals from the fatty acid chains (0.8 and 2.8 ppm), confirming the monomer structure, which includes both acryloylamide and fatty acid moieties.

FIGURE 2 FTIR (A) andĚý¹H-NMR (B) spectra of CCM.

To confirm the structure of CCM, Electrospray Ionization Mass Spectrometry (ESI-MS) was used (Figure 3), and the presence of the predominant [laurate-CCM + Na]⁺ fraction was confirmed, with the highest peak observed at 320 m/z. These results correlate with the fatty acid composition of the coconut oil used for synthesis, where lauric acid fragments comprise approximately 60% by weight. Additionally, the CCM molecules also contain smaller fractions of other fatty acid chains, as indicated by mass peaks at 264, 348, 376, and 402 m/z. Given the diverse fatty acid composition of coconut oil, the CCM is a mixture of monomers, with lauric acid residue being the most prevalent.

FIGURE 3 ESI mass spectra of CCM.

The iodine value of CCM (65 g/100 g) is higher than that of coconut oil due to the presence of acrylamide moiety, yet as it can be expected, this value is significantly lower than that of unsaturated plant oil-based monomers (POBMs) reported previously by our group.⁷

By Kateryna Rudich, Yehor Polunin, Ayda Dadras, Mohiuddin Quadir, and Andriy Voronov

Introduction

The use of polymers as a seed coating is a prevalent agricultural practice because it helps to reduce the overall amount of chemicals needed, promoting more sustainable farming practices. Seed coating is the process of applying a protective layer, typically made of polymers, nutrients, or agrochemicals, to seeds before planting. The primary purposes of seed coatings are to enhance seed performance, protect against pathogens and pests, improve germination rates, and provide essential nutrients during early plant development, all while minimizing the risks associated with conventional seed treatment methods.¹ However, seed coatings mainly involve the use of petroleum-based, non-biodegradable polymers that significantly contribute to microplastic pollution.

This study explores the potential of biomass- and plant oil-based polymers recently developed by our group as a sustainable alternative to be applied in seed coatings. The resulting polymer, consisting of hemicellulose xylan modified by grafted chains made of babassu oil-based monomers (HX-g-BOBM), is designed as a sustainable film-forming material targeting advanced water barrier performance.² HX-g-BOBM is a highly biobased, tough, and processable bioplastic. Being biodegradable, it may offer a renewable alternative to applications of conventional petroleum-based polymers in food packaging. This study evaluates the feasibility of HX-g-BOBM as a seed coating by applying it to corn (Zea mays) seeds and assessing the effect on the seeds’ vigor and viability.

HX-g-BOBM Synthesis

Agricultural wastes such as some lignocellulosic materials and plant oils are excellent renewable resources for the production of sustainable coatings due to their chemical versatility, availability, and often low cost.3-6 HX-g-BOBM is synthesized from hemicellulose xylan and babassu oil, which are believed to be inherently biodegradable or compostable by nature. Babassu oil-based monomer (BOBM) and HX-g-BOBM were synthesized following the procedures described in earlier publications.^1,7,8 The structure of BBM is shown in Figure 1A. A schematic representation of HX-g-BOBM synthesis is presented in Figure 1B. Before polymerization, xylan was reacted with maleic anhydride through an esterification reaction. During this process, an ester bond is formed between the maleic anhydride and hydroxyl groups of xylan, while the vinyl group of maleic anhydride remains intact, providing a reactive site for the attachment of BOBM-based grafted chains. After successful maleinization, the modified xylan was added to the BOBM along with the AIBN initiator (1.5 wt %). Grafting polymerization reaction was conducted in bulk at 80 °C for 8 hours under a nitrogen atmosphere. After purification from unreacted xylan and BOBM, a homogeneous solution of highly branched HX-g-BOBM was obtained. Multiple xylan macromolecules are decorated by BOBM chains, and BOBM homopolymer is also present in the resulting material.

FIGURE 1 The chemical structure of babassu oil-based monomer (BOBM) used in this study. R (x:y) – the structure of the fatty acids (x – the number of carbon atoms in the fatty acid chain, y – the number of double bonds in the fatty acid) (A). Synthetic scheme of HX-g-BOBM grafted polymerization (B).

HX-g-BOBM Emulsification

To simulate an industrial approach, where seeds are typically covered by spraying a water-based slurry containing polymers and additives over the seeds in a rotating drum machine, HX-g-BOBM was emulsified in water. Dodecylbenzenesulfonic acid, which serves as an emulsifying agent, was first dissolved in water, vortexed for 5 min, and ultrasonicated for 20 min. The HX-g-BOBM dispersion was then added dropwise and was vortexed for an additional 5 min and ultrasonicated for 20 min until a stable emulsion with a final polymer content of 15 wt % was achieved. Particle size measurement was conducted using a Malvern Zetasizer Nano-ZS90 (Figure 2A).

The viscosity of the emulsion was measured using an ARES G2 rheometer with 25 mm parallel plate clamps, gap size 0.5 mm, strain 1%, frequency range 1-500 rad/s, and temperature 25 ÂşC. The viscosity of the HX-g-BOBM emulsion exhibits non-Newtonian behavior, with apparent viscosity decreasing as the shear rate increases, indicating shear-thinning behavior. At low shear rates (< 1 rad/s), the emulsion displays high viscosity, suggesting good stability and minimal settling of particles. The apparent viscosity decreased significantly at higher shear rates (> 10 rad/s), indicating that the emulsion would flow more easily during the seed coating process, which is beneficial for uniform coating application in industrial applications (Figure 2B).

FIGURE 2 Particle size (A) and rheological behavior (B) of 15 wt % HX-g-BOBM water emulsion.

Seed Coating Procedure

Seeds were coated manually using a plastic bag with a subsequent transfer of seeds to the sieve and drying at room temperature (25 ±1°C) for 24 hours. In each case, 100 corn seeds were incubated with 2 ml of water-based polymer slurry and manually shaken for 5 minutes to simulate the industrial rotating drum coating procedure. The weight of the seeds was compared before and after the coating procedure. The average weight increase was found to be 2.0 ± 0.3 wt % from the initial mass of seeds.

HX-g-BOBM Coating Water Absorption

The water absorption test was conducted to evaluate the coating’s interactions with water. Coating film samples were submerged in 20 ml of distilled water and kept at room temperature. After immersion, excess water was removed, and the samples were weighed at specific time intervals to quantify the changes in mass. To ensure accuracy and reliability, each test was performed in triplicate. The resulting plot shows the relationship between time and weight gain (Figure 3A). The ability of the coating to swell is advantageous for enhancing water retention, by helping to keep the seeds hydrated after planting.

Images courtesy of BioPowder

The company has been creating particles and powders from , a byproduct of the olive oil industry, to provide an alternative to traditional mineral-based coating additives.

Kathrin Schilling, BioPowder’s founder and director, says the shift toward biobased materials is gaining momentum, especially in the decorative coatings market. While some technical coatings still face challenges in this transition, decorative applications have found new opportunities in plant-based products. Schilling notes that the company’s work with olive stones offers coatings manufacturers a chance to create products that are not only more sustainable but also competitive in terms of performance and cost.

The company says the use of upcycled olive stones, BioPowder’s flagship product, offers benefits in both functionality and environmental impact. Olive stones come from a carbon-neutral ecosystem, where the carbon emissions from food production and byproducts are offset by the olive trees’ carbon absorption. The particles are lightweight, durable, and compatible with a variety of , including biobased epoxy, polyurethane, and acrylic formulations. These properties make them suitable for improving abrasion resistance, durability, and curing times in coatings.

BioPowder has also expanded its offerings to include biobased color particles, allowing coatings manufacturers to customize the appearance of their products. The company says it works closely with manufacturers to adjust particle properties, such as viscosity and texture, for specific applications.

In a recent collaboration, BioPowder partnered with Austrian company F/LIST, known for its luxury coatings used in private jets and residential projects. F/LIST’s R&D division, F/LAB, developed a biobased laminate called F/LAB Aenigma Eco, which incorporates upcycled olive stones alongside other sustainable materials such as plant-based pigments and mother-of-pearl. The laminate is designed for high-end decorative applications, including wall coverings and furniture.

Schilling says the project demonstrates the potential for biobased innovation in the coatings industry, combining traditional craftsmanship with cutting-edge material science. “Our mission is to help companies transition to biobased product lines,” Schilling says. “We aim to solve the challenges that come with reducing environmental impact, and our helps accelerate the design and development of new eco-friendly coatings.”

To learn more about BioPowder and its work with biobased ingredients, visit .

µţ˛âĚýTetiana Shevtsova,ĚýZoriana Demchuk,ĚýOleh Shevchuk,ĚýSergiy Minko, andĚýAndriy Voronov

Cellulose, a linear polysaccharide biopolymer, has applications in various industries including food packaging, personal care products, and construction, due to its unique physico-chemical properties, as well as its biocompatibility and biodegradability. This study introduces a methodology to enhance the hydrophobicity of nanocrystalline (CNC) and microfibrillated (MFC) cellulose, using the covalent attachment (grafting) of copolymers based on plant oils.

Current methodologies for cellulose surface modification are limited in terms of hydrophobizing agents due to both their high cost and the fact that most are not renewable. This study focuses on the surface modification of CNC and MFC by graft copolymers from plant oil-based acrylic monomers (POBMs) developed by this research group.

The grafting and the properties of the resulting copolymers were determined using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) to demonstrate the presence of grafted POBMs and their impact on the characteristics of modified CNC and MFC.

Introduction

Cellulose, one of the most abundant natural polymers, boasts remarkable strength, stiffness, and sustainability. However, there are challenges in applying cellulose to materials fabrication which include high hydrophilicity and, therefore, poor compatibility with most polymer matrices.¹ĚýModification of cellulose to improve the material’s water resistance and compatibility with specific polymer matrices remains a challenge among researchers due to cellulose’s complex chemical structure and extensive hydrogen bonding between macromolecules.

The need for cellulose modification arises mainly from the desire to overcome extensive hydrophilicity to unlock the full potential presented in this abundant biopolymer. The modification process needs to tailor cellulose properties to specific applications to make material applicable in diverse industrial applications. For instance, the hydrophobization of cellulose is important when aiming to create water-resistant materials with improved chemical and mechanical properties.^{2, 3}

In this study, emulsion polymerization was utilized as a versatile and highly effective methodology for hydrophobizing cellulose.⁴ĚýThe approach brings several advantages, including minimized environmental impact, scalability, and the utilization of biobased resources.⁵

Cellulose nanocrystals (CNCs) and microfibrillated cellulose (MFC) already play important roles in biomaterials, providing versatility for sustainable innovations.⁶ĚýModifying the CNCs and MFC with plant oil-based polymers can be a significant undertaking, offering opportunities to tailor properties for specific applications. This article explores the importance of hydrophobizing these cellulosic materials and highlighting their promising properties to be applied as sustainable biomaterials.

Methods

To determine the surface energy and the contact angle of modified cellulose, water and diiodomethane contact angle measurements were carried out by a contact angle/surface tension analyzer using a drop shape analyzer (DSA 100, KRĂśSS, Hamburg, Germany). Reported values were an average of 5 droplets.

The morphology of modified cellulose was observed on a tungsten filament 100 kV transmission electron microscope (TEM) JEOL JEM-100CX II, (JEOL, Peabody, MA). For the TEM measurements, a small amount of modified cellulose diluted with ethanol was placed onto a copper mesh covered with a thin carbon film. The samples were characterized after drying.

Fourier transform infrared spectra were recorded with a Nicolet 8700 FTIR spectrometer (Thermo Scientific) equipped with a Smart iTR attenuated total reflectance (ATR) sampling accessory. FTIR spectra in the range of 400–4000 cm-1 of modified CNC and MFC samples were recorded in reflectance mode, with 64 scans per sample. The analysis of the obtained FTIR spectra was conducted by identifying the chemical bonds in the molecule’s chemical structure according to standardized absorption peaks of functional groups.

The thermogravimetric analysis (TGA) investigated the thermal degradation of CNC and MFC samples. Employing a Discovery TGA 550 thermogravimetric analyzer (TA Instruments), the samples (ranging from 5 to 15 mg) underwent heating from 20 to 650 °C at a rate of 10 °C min^–1Ěýunder a nitrogen atmosphere.

The surface elemental composition of modified CNC and MFC materials was analyzed using a Thermo Scientific™ K-Alpha™ X-ray photoelectron spectroscopy (XPS) instrument. The equipment featured a monochromatic Al Kα (1486.68 eV) X-ray source and an Ar+ ion source (up to 4000 eV). To ensure accurate results, all samples went through an argon ion cleaning process to minimize trace contaminants, such as oxygen and carbon, prior to analysis. The argon cleaning was applied to a 2 mm Ă— 2 mm area of each sample by sputtering with an Ar+ ion cluster beam set to 4000 eV for 120 seconds using the MAGCIS^®Ěýcluster gun. The XPS survey scan focused on the observation of photoemission lines for C1s, O1s, and N1s. The survey scan was an average of 10 scans with a Pass Energy of 200 eV, Dwell Time of 10 ms, and an Energy Step size of 1.0 eV. Spectra were collected at a 90° angle normal to the surface within a 400-ÎĽm area. To maintain optimal conditions, the chamber pressure was kept below 1.5 Ă— 10^–7ĚýTorr, and the analysis was conducted at ambient temperature. The instrument’s software, Avantage, was employed for the quantification of atomic concentrations.

For elemental analysis, a Leco 932 CHNS combustion analyzer was used to determine percentages of carbon, nitrogen, and hydrogen in all samples. Samples of each material were weighed to a target weight of approximately 2 mg. A series of three calibration standard samples were run in the machine followed by the actual test samples. The actual process was as follows:

1. Samples were removed from sample containers and poured into foil sample capsules.
2. The capsules were weighed individually, and these weights were programmed into the machine.
3. The machine then dropped the appropriate sample into its furnace where the sample combusted.
4. After combustion, the percentages of each element were calculated.

The paint and coatings industry gathered May 16–18 at Harrah’s Resort Atlantic City in New Jersey for the very successful 2023 edition of the Eastern Coatings Show. The technical conference and exhibit were hosted by three East Coast paint societies: the Philadelphia Society for Coatings Technology, the Metropolitan New York Coatings Association, and the New England Society for Coatings Technology. With more than 1,300 attendees, the conference had well-attended presentations and robust conversations on the exhibit floor.

The technical conference began on the first day with a coatings short course titled “Fundamentals of Coatings and Sustainable Materials in the Marketplace,” which was presented by James Rawlins and Robson Storey, both professors at the University of Southern Mississippi’s School of Polymer Science and Engineering. The second day started with a packed room for the keynote presentation on “Leading a Business through Challenging Times” by Dan Calkins, CEO and chairman of Benjamin Moore.

The afternoon of day two included an interesting panel discussion. Titled “Where Do We Go from Here? The Future of the Coatings Industry,” the panel included George Pilcher of the ChemQuest Group, Amanda Andrews of Michelman, Professor Dean Webster of North Dakota State University, and Professor Ray Fernando of the California Polytechnic State University. Each provided their unique view on what to watch for in the future and touched on topics such as sustainability, technical staffing, removing substances of concern from raw materials and formulations, raw material sourcing, recycling, and the role of artificial intelligence.

The technical program consisted of 42 technical presentations by industry scientists on a variety of topics, including advances in resins, pigments, additives, testing methods, and coatings formulation. This article examines some highlights and summaries of just a few of the presentations.

Sustainability

Sustainability is an important concern that is getting increased attention in the coatings industry. This includes the decades-long search for products with lower volatile organic content (VOC) and the more recent emphasis on biosourced raw materials, the industry has been interested in sustainable technologies for a long time. More than a buzzword, sustainability is becoming a way of life for the industry.

A full one-third of the presentations referred to sustainability in their abstracts and titles, and one of the concurrent tracks was titled “Driving Sustainable Coatings with Chemistry.” Even the short course presented on the first day of the technical program mentioned sustainable materials in its title.

In a presentation titled “Alkyd Emulsions and Their Contribution to More Sustainable Paint and Coatings Formulations,” Caroline Matthieson of Worlée-Chemie spoke about the use of biosourced raw materials in the production of alkyd resins. By introducing the 17 sustainable development goals set in the United Nations 2030 Agenda for Sustainable Development,^1,2 Matthieson first explained how Worlée is focusing on several of the goals in their own work, such as responsible consumption and production (#12), climate action (#13), and partnerships for goals (#17).

Figure 1. Typical structure of an alkyd resin, which is a polyester resin based on a polyacid (such as isophthalic acid, shown here) and a polyol (such as glycerol, shown here) and modified with a fatty acid.

The presentation then described the use of biosourced fatty acids in the production of alkyd resins. Alkyds are polyester resins, formed by the condensation reaction of polyacids and polyols and modified with fatty acids (Figure 1). The fatty acids used to make alkyds have biobased origins. For example, linseed oil is a common source of fatty acids used in alkyds and is produced from flax seeds. Matthieson explained that, although linseed oil is a great source of renewable and biobased raw materials, its use in coating resins competes with its use in the food supply, where it is employed as a source of alpha-linolenic acid (an omega-3 fatty acid).

Camelina oil was presented as a beneficial alternative to linseed. Table 1 shows a comparison of linseed and camelina oil compositions in terms of the fatty acids available in each. Matthieson explained how camelina oil is a more sustainable choice for Worlée because the camelina plant (Camelina sativa) is grown locally near their production sites in Germany, while flax is not. In addition to regional cultivation, camelina can be grown as a mixed crop with peas or as a secondary crop in temporarily fallow land, and thus, it does not compete with food production. Other advantages include that it provides a food source for pollinators, requires less fertilizer, has good resistance to pests such as aphids, and that the crop’s yield has a lower dependence on the weather.

Although there are limited choices of biobased polyacids for use in alkyd resins, some examples include furandicarboxylic acid and succinic acid. Many choices of biobased polyols exist, so depending on choice of raw materials, Matthieson explained that alkyds can be produced with 85% to almost 100% biobased raw materials. As an example, a waterborne alkyd emulsion with 85% renewable content and based on camelina oil was described as having very similar physical properties and performance compared to one prepared with linseed oil, and with the sustainability advantages of less competition with the food supply and use of regionally produced materials.

Table 1. Fatty Acid Distribution in the Composition of Oils

Another presentation on the topic of sustainable coatings was presented by George Daisey of Dow and was titled “Sustainable Coatings Technology That Works.” Daisey began with an introduction to Dow’s sustainability goals, which include combatting climate change, driving circular economy by designing for circularity, and innovating new materials that offer a more favorable health and environmental profile over their lifecycle. Dow has an ambitious goal of reducing carbon emissions and being carbon-neutral in its operations by 2050. In particular, Daisey described the sustainability benefits of roof coatings, which are defined as thick, white, monolithic, and solar-reflective elastomeric films.

The most important value proposition for maintenance with roof coatings is roof life extension, which lowers the lifecycle cost of the roof and decreases the amount of material associated with replacing a roof that is being sent to landfills. In addition, the use of solar-reflective roof coatings can help lower energy usage associated with air conditioning and reduce the “urban heat island” effect.² Daisey described how an effective roof coating must have both high reflectivity to prevent absorption of solar energy by the building, as well as high emissivity of the energy that is absorbed. According to Daisey, an uncoated roof can reach a surface temperature of approximately 180 °F on a hot summer day, with an effective roof coating dropping the temperature by 60 degrees to 120 °F. He emphasized that the drive for more sustainable roof coatings cannot ignore the other challenges that a roof coating must face, which include the need for resistance to biological growth and dirt pickup and adhesion issues on the varied roofing substrates.

According to Daisey, Dow is thinking about advancing roof coatings via multiple technologies, including delivering biological resistance without biocides, creating faster-setting acrylics to reduce labor and equipment time, enhancing durability, using biosourced raw materials, and developing hybrid technologies. He expanded on the hybrid technologies approach by describing new acrylic-urethane products for two global regions. One is a waterborne acrylic-urethane hybrid polymer designed for liquid-applied waterproofing membranes for flat roofs in the EMEAI markets (Europe, Middle East, Africa, and India). The hybrid polymer is designed to have a superior balance of cold temperature flexibility and traffic-ability at temperatures up to 90 °C. Roof coatings based on the acrylic-urethane hybrid can be formulated as a liquid-applied roofing membrane that meets European CE (ConformitĂ© EuropĂ©ene) marking requirements and passes the strict durability tests for an expected working life of 25 years, as set forth by the European Organisation for Technical Approvals (EOTA) in ETAG 005.³

Today, products meeting the ETAG 005 are mainly solventborne, with one-component (1K) polyurethanes being the most common. The hybrid offers a waterborne alternative in a market dominated by solventborne technology. Daisey presented data showing that the waterborne acrylic-urethane hybrid yields a coating with similar mechanical properties compared with a 1K polyurethane, while contributing to better durability. Tensile strength of the hybrid was close to that of a 1K polyurethane and higher than a standard waterborne acrylic coating. For elongation, after 14 days of thermal aging at 80 °C, the 1K polyurethane coating dropped to 137% from an initial value of 220%, while the hybrid started at 272% and only dropped to 245%, more in line with the performance of the waterborne elastomeric acrylic roof coating. The amount of water swelling exhibited by the hybrid coating (8.9%) was intermediate between the 1K polyurethane (1%) and the waterborne acrylic (16.4%). Accelerated and natural weathering data demonstrated that the hybrid maintains good mechanical properties on extended UV exposure and has improved durability versus the acrylic.

In an interesting presentation titled “Analytical methodologies and challenges for understanding paint emissions,” Michelle Gallagher, Ph.D., of Dow described some of the challenges facing the analytical chemist when attempting to quantify and identify volatile emissions. Emissions testing is becoming more important because health-conscious customers care about indoor air quality and emissions that originate from consumer products such as paint. In addition, Gallagher explained how the growth of green building certifications and their requirements for low VOC and low emission products has increased the industry’s need for such testing. Dow has been growing its emission testing capabilities to simulate the emission rate of paint VOCs after application, as well as to understand how its products affect emissions.

While bulk VOCs are measured on wet paints using ASTM D6886 and reported in units of g/L, emitted VOCs are measured on a paint after application using chamber methods and reported in units of ÎĽg/m³. There are several different certifications and standards dealing with emissions, such as the chamber method described in California Department of Public Health (CDPH) Standard Method v1.2, a widely used standard in North America for measuring emissions from building products such as paints.⁴ A typical chamber is made of stainless steel and has the ability to control humidity and airflow. The paint is applied to a plate and placed under constant airflow (e.g., 0.5 to 1 air exchange per hour). At various times, the emissions are sampled using an absorbent trap, which is then analyzed using GC-MS or HPLC methods.

Gallagher explained that one of the challenges in using these chamber methods is obtaining a clean background prior to testing for emissions. For example, each volatile should be under 2 ÎĽg/m³, and the total VOC should be under 25 ÎĽg/m³ in the CDPH Standard Method v1.2.⁴ Gallagher described how a robust cleaning procedure is required and how gloves should always be worn when working with the chamber and plates and holders. Even a single fingerprint can lead to the detection of volatiles (e.g., hexadecenoic acid) at a level above the threshold allowed for background emissions. Chambers must be cleaned and purged between each study, and the background emissions levels checked before taking a new series of measurements. In addition, Gallagher stressed that absorbent tubes should always be cleaned and background checked before collecting samples.

Other challenges include the choice of substrate specified by the method. While clean stainless steel and glass have very low background emissions, drywall or drywall with the edges taped is sometimes specified. Both the drywall and the edge tapes (such as foil or metallized polymer tape) can lead to contaminant emissions being measured that do not emanate from the coating. Calibration is also critical, and toluene is typically used for that purpose.

Identifying the source of the volatile emissions can also be challenging. Every material used in a paint formulation can have its own unique volatiles, so analyzing raw materials individually with GC-MS can help determine from where emissions originate. Understanding the source of emissions is necessary to better control them through both raw material and coating formulation design. ĚýFinally, it was stressed that it is difficult to predict emissions based on total VOC measurements, because ASTM D6886 measures the total VOC in the wet bulk paint, while emissions testing measures VOCs at various times as the coating dries.

Functional Coating

End-users are continuing to ask for more of their paints and coatings. In addition to their decorative and protective properties, there are numerous coatings that are also designed to provide other functions such as soft-feel haptics, sound damping, thermal insulation, or antimicrobial properties. For example, in a presentation titled “New Thermal Management Raw Materials Platform Gives Flexibility to Develop Next Generation Thermal Insulation Coatings (TIC) with Improved Performance,” Hrishikesh Bhide, Ph.D., of Evonik described new resin and filler materials for use in thermal insulation coatings. Thermal insulation coatings are a type of functional coating designed to provide personnel protection by reducing the surface temperature of hot surfaces and prevent skin burns, as well as to improve energy management. The coatings also provide direct protection of the substrate and lead to a reduced risk of corrosion under insulation (CUI).

Bhide described two new silica granules with low thermal conductivity that can be used in thermal insulation coatings. The first was described as a super-insulating granule (SIG) with a larger particle size (~300 μm) and high hydrophobicity. The SIG particles derive their insulation properties from a passivated amorphous silica composite core and have a thermal conductivity of 24 mW/m·K. The second granule material was described as a SIG synergist, having a particle size of ~30 m and thermal conductivity of 30 mW/m·K. The small particle size synergistic filler reduces the cracking tendency of highly filled insulation coatings and facilitates smoother coatings. When formulated with a waterborne acrylic binder, the combination of the SIG and SIG synergist granules provides a coating with lower thermal conductivity (about 5mW/m·K lower) than when either is used by itself and with little change in thermal conductivity after heat aging.

In addition to the insulating granules, Bhide also introduced a new waterborne silicone resin, which, along with the granules, can be utilized as the sole binder in thermal insulation coatings with higher heat resistance than standard binders such as acrylics. The combination of the silicone binder and the two insulating granules leads to coatings with good fire retardance and low thermal conductivity (57 mW/m·K at 25 °C). The silicone resin can also be blended with other waterborne binders such as acrylics to extend the heat resistance of insulation coatings based on traditional binders such as acrylics. Bhide also described the use of these materials in some field studies within chemical production facilities for condensation control, thermal management, and safe-touch properties.

In another paper titled “High-Touch Coatings with Bactericidal and Virucidal Properties,” Mark Langille, Ph.D., of Corning described a new copper-glass additive for use in antimicrobial coatings with high efficacy towards both bacteria and viruses. Langille began with a discussion of the expected performance of antimicrobial coatings that could be used to improve public health by killing microbes that come in contact with the coating surface. In contrast to liquid disinfecting agents, a dried coating would be expected to provide a surface that is continuously active, provides antimicrobial efficacy between regular cleaning cycles, and addresses a spectrum of real-world germs, including easier-to-kill bacteria and viruses (e.g., SARS-CoV-2) and harder-to-kill viruses such as non-enveloped viruses (e.g., norovirus).

In addition, Langille described how the U.S. Environmental Protection Agency (EPA) formalized guidance in 2022 for products claiming residual efficacy, including test methods for demonstrating both bactericidal and virucidal activity.^5,6 To better simulate real world contamination events, dry test conditions are utilized in which the surface is contaminated with bacteria or virus, allowed to dry, and then analyzed for how effectively it killed the microbes after only 2 hours. It is expected that at least a 3-log reduction occurs, or 99.9% of microbes are killed. In addition, durability of the antimicrobial properties is evaluated by putting the surface through simulated wear/cleaning cycles and then testing for efficacy.

Langille discussed how copper is a powerful, natural antimicrobial and is effective at killing both bacteria and viruses. Copper in the +1 oxidation state (Cu+1) is a particularly potent but less stable form of copper, and the innovation in the new additive is that Corning found a method of stabilizing Cu+1 in glass. Aluminoborosilicate glass and a copper source are melted together to form a glass, which is then milled to give the copper-glass additive, with an average particle size of 4 ÎĽm. The additive is a brown color but can be incorporated into a large variety of paint colors. A typical loading in a paint formulation is approximately 1% by weight of the copper-glass additive.

Data were presented showing results of antimicrobial activity (log kill) after dosing six commercial coating formulations with the copper-glass additive at various levels (0 to 40 g per gallon). Effectiveness at a particular dose varied amongst the coatings because of differences in formulation ingredients, but each coating demonstrated log-3 kill (99.9% kill) of Staphylococcus aureus at levels of approximately 1% additive, and all had log-5 kill (99.999% reduction) at a level of 40 g/gallon or below.

Langille also discussed how challenges in initial or long-term efficacy can occur for coatings that are high in polymer content due to their low porosity, which may prevent access of the Cu+1 in the coating to the microbe at the coating surface. An example presented was a waterborne direct-to-metal coating with 2% copper-glass additive, where efficacy dropped after 3 months. A study of compatibilizers to control the stability and availability of the copper-glass additive identified solutions that enabled long-term efficacy in the system. It was noted that compatibilizers can eliminate the need for significant formulation changes and thus make it easier for current commercial formulations to add antimicrobial functionality via the copper-glass additive.

Additive Technologies

Figure 2. Generic formula of alkyl aryl sulfonic acid salts used as corrosion inhibitors.

Coatings additives are always an important topic of discussion when the coatings industry gets together for technical conferences, and this year’s Eastern Coatings Show was no different, as multiple presentations covered new additives to enhance the performance of paints and coatings. In a presentation titled “Improving Corrosion Resistance of DTM Coatings Using Hydrophobic Alkyl Aryl Sulfonate Additives,” Matthew Gadman of King Industries talked about a class of easy-to-use liquid corrosion inhibitors that can be effective at low dosages of approximately 1 to 3%. Corrosion takes a large economic toll on the economy, to the tune of $2.5 trillion globally (about 3.5% of global gross domestic product), as Gadman described. The corrosion inhibitors he discussed have the generic structure shown in Figure 2 containing a hydrophobic naphthalene ring with alkyl substituents and a polar sulfonate salt group. The counterion can vary with both metal and amine cations being used.

The corrosion inhibitors can be used in both clear and pigmented coatings, including high gloss systems. They are compatible with a range of resins and can also act as catalysts for aminoplast coatings (for X = Zn and Ca). They can also aid in wet adhesion and pigment dispersion. In a coating on metal, the polar portion of the molecule orients toward the metal surface and passivates the surface, preventing the formation of anodic corrosion sites where oxidation reactions occur. The non-polar alkyl-substituted aryl group orients away from the metal surface and prevents water from reaching the surface.

Gadman shared the results of several experiments where the alkyl aryl sulfonate inhibitors were added to coating formulations and evaluated for corrosion resistance. For example, a barium sulfonate salt was incorporated at 1% on total formulation weight into a 1K solventborne acrylic/melamine clear baking finish and was found to aid in preventing blisters and rusting compared with the blank control, which had no inhibitor. In another set of experiments, the sulfonic acid salts were evaluated at 1% on total formulation weight in several pigmented formulations in combination with a variety of anticorrosive pigments. Thermoset and air-dry systems were evaluated, and all showed a synergistic effect on corrosion resistance when using the sulfonate salts with an inorganic anticorrosive pigment. Finally, in a third set of experiments, Gadman demonstrated that the addition of a barium sulfonate salt to aerosol paints improved the corrosion resistance and had no negative effect on appearance.

Helena Wassenius, Ph.D., of Nouryon presented an interesting paper covering a new type of cellulosic rheology modifier in a presentation titled “New Ultra-Low Viscous, Highly Associative Cellulose Ethers for Acrylic-Based Architectural Paints.” Wassenius explained how synthetic HEUR (hydrophobically modified ethoxylated urethane) rheology modifiers have low molecular weight and are highly associative, while HM-CE (hydrophobically modified cellulose ether) thickeners are cellulosic-based materials of high molecular weight and are typically moderately associative. HEUR thickeners provide excellent levelling, while HM-CE thickeners provide good sag resistance. The new cellulosic thickener falls between the two extremes and provides a high level of association.

Results of testing in 30% PVC semigloss architectural paints were detailed. Leveling performance of the formulation containing the new cellulosic ether was similar to one with HEUR thickener and much improved relative to those containing HM-CE thickener. Meanwhile, sag resistance was better than the HEUR and closer to that of an HM-CE thickener. In addition, viscosity loss on tinting, syneresis resistance, and color acceptance were much improved versus a HEUR thickened formulation. The new cellulose ether also shows excellent spatter resistance, and the hiding power, as measured by contrast ratio after roller application, was substantially better than HM-CE and close to that of a pure HEUR system. Finally, Wassenius alluded to significant sustainability benefits, as found in a lifecycle analysis that estimated the contribution of the thickener system to the carbon footprint of one ton of formulated paint is 40% lower for the new cellulose ether thickener compared to a synthetic HEUR thickener.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) offer many performance benefits to paints and coatings, but the industry is actively trying to replace these materials due to their link to serious health effects and persistence in the environment. In a presentation titled “Free of PTFE! New Micronized Wax Additives for Scratch & Scuff Resistance,” Smriti Arora of BYK discussed new wax additives that were developed as replacements for polytetrafluoroethylene (PTFE). PTFE, also known by the tradename Teflon, is a fluoropolymer and a well-known PFAS example. Wax additives based on PTFE are often used in coatings because they impart scuff, scratch, and abrasion resistance.

Figure 3. Orientation of wax additives in a dried coating film. Most wax additives orient to the surface of the film (a), while PTFE-based waxes orient more homogeneously throughout the film (b) due to their higher densities.

Most waxes orient to the paint surface but can be removed from the surface during abrasion. Arora explained that due to their higher density, PTFE-containing waxes orient more evenly throughout the coating film and have a more durable abrasion resistance (Figure 3). Three new PTFE-free additives, based on either polyethylene (PE) or modified PE alloy waxes, were introduced, and the presenter explained that they also provide a homogenous distribution in the coating film. The additives improve both abrasion resistance and scratch resistance and produce a medium-to-strong reduction in coefficient of friction (COF). Due to their small particle size, the additives have minimal impact on gloss. According to Arora, the new additives are also food-contact compliant.

Examples of their effectiveness in Taber and Wazau abrasion resistance was demonstrated for a 1K waterborne acrylic industrial coating, where the new PTFE-free additives showed similar performance to the PTFE-containing controls at 2% loading on total formulation weight. Evaluation in a BPA-free clear can coating showed abrasion results and COF reduction comparable to PE/PTFE controls at 1% loading. For systems with low COF requirements, a combination with a softer wax (e.g., carnuba) or polysiloxane additive was also recommended, and examples of the strategy were shown for an epoxy/phenolic gold lacquer. Results of testing at 4% loading in an architectural interior flat deep base were also shared, and the PTFE-free wax additives had a positive effect on both scuff resistance and scrub resistance. Arora stressed the wide compatibility of the PTFE-free wax additives across waterborne, solventborne, and UV coating systems and their comparable technical performance to PE/PTFE-based wax additives.

Resin Technologies

Several conference presentations covered new resin technologies for both architectural and industrial coatings. One such presentation was titled “New Polyester Dispersion for VOC-Compliant 2-Component Waterborne Coatings,” in which Ashish Zore, Ph.D., of Coim USA described the use of a new waterborne polyester polyol dispersion for use in two-component (2K) polyurethane floor coatings with good light stability and near-zero VOC content. Zore described some of the challenges facing the floor coating industry, including restrictive VOC limits that are under 50 g/L in some regions, the phasing out of exempt solvents, and the continuing demand for higher performance. Floor coating end-users are asking for better light stability, chemical resistance, wear resistance, and weatherability.

The polyester polyol dispersion is supplied at greater than 60% solids in water and contains no co-solvents or surfactants. It can be formulated into 2K waterborne polyurethane coatings utilizing standard hydrophobic polyisocyanates, rather than the hydrophilically-modified polyisocyanates that are often required for waterborne systems. According to Zore, it is suitable for use in various industrial coating applications, including general industrial finishing, protective coatings, and floor coatings.

Zore described testing results comparing a 2K polyurethane coating based on the waterborne polyester polyol dispersion with polyurethanes based on two waterborne acrylic polyols, as well as two high-solids polyaspartic coatings. The coating based on the polyester polyol dispersion had an ultra-low VOC level of under 25 g/L. The gloss of the polyester-based polyurethane was very high, with a 20°/60° gloss of 82/92, comparable to the polyaspartic coatings (88/94) and much higher than the two acrylic-based polyurethanes (8/40 and 39/71). Flexibility of the polyester-based coating was excellent, but both pencil and pendulum hardness were lower than the other systems. Zore noted that hardness could be improved by manipulating the polyol/isocyanate ratio toward more isocyanate and commented that stoichiometries with higher isocyanate also yield better chemical resistance. Finally, the estimated applied cost ($/sq ft) of the waterborne polyester-based formulation was only 75% of the cost of the waterborne acrylic-based polyurethane and approximately one-third of the cost of the high solids polyaspartic system.

In a presentation titled “Enhance Performance of Waterborne Coatings Using Functionalized Binders with Novel Monomers,” Tiffany Chen of Solvay described the use of a functional specialty monomer for acrylic and styrene-acrylic latex polymers. Added during the emulsion polymerization process, with recommended levels of 0.5 to 2% based on total weight of monomer, the monomer offers performance benefits in both architectural and industrial coatings. Chen first described its use in an architectural latex with a BA/MMA backbone. A control latex was made with 2% methacrylic acid (MAA) and compared with a latex containing 1% MAA and 2% specialty monomer. In a semigloss formulation (22% PVC), the functional monomer resulted in improvements in opacity and tint strength, as well as in metal adhesion and the removal of household stains.

In another study, a flat architectural coating (49% PVC) was prepared with a latex containing 1% specialty monomer. The functional latex demonstrated better color acceptance for both initial and heat aged paints compared to a control. Scrub resistance was also better, as was dry and particularly wet adhesion to various substrates (e.g., glass, steel, and aluminum).

The specialty monomer was also evaluated in a styrene-acrylic composition designed for light duty direct-to-metal (DTM) coatings. The control used 2% acrylic acid (AA), while the functional monomer replaced half of the acrylic acid in the experimental latex (1% AA and 1% specialty monomer). Formulated into a gloss DTM coating (18% PVC), the functional monomer led to improvements in corrosion resistance as measured by salt fog exposure (ASTM B117) and blister resistance upon immersion in water. Adhesion over cold-rolled steel was greatly improved versus the control, and in addition the initial gloss was much higher, with a 60° gloss of 63 units compared to the control with a gloss of only 17 units. Overall, the specialty monomer facilitates the improvement in several properties for both architectural and industrial latex coatings.

References

1. United Nations. 2030 Agenda for Sustainable Development. (accessed July 11, 2023).
2. United Nations. The Sustainable Development Goals Report 2022. (accessed July 11, 2023).
3. European Organisation for Technical Approvals. ETAG 005, Guideline for European Technical Approval of Liquid Applied Roof Waterproofing Kits, 2004.
4. California Department of Public Health. Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers, Version 1.2, 2017.
5. US Environmental Protection Agency. Guidance for Products Adding Residual Efficacy Claims. (accessed July 11, 2023).
6. U.S. Environmental Protection Agency. Test Method for Evaluating the Efficacy of Antimicrobial Surface Coatings, SOP Number MB-40-00, revised September 2022.

About the Author

Leo J. Procopio, Ph.D., is president and owner of Paintology Coatings Research LLC. For more information, visitĚýĚýor emailĚýleo.procopio@scienceofpaint.com.

Introduction

Knots—the circular imperfections in the wood grain—often cause issues in coating appearance due to their high concentration of potent extractives that can degrade a coating system over time. Unfortunately, knots are unavoidable in softwood species, such as pine, which is often used for furniture and cabinetry applications.

Knots occur naturally when branches die and become encapsulated as the tree grows. During the encapsulation process, extractives—the tree’s natural resins—seal off the former branch’s location and provide a biological boundary between this area and the rest of the tree. Wood typically contains up to 4 wt % extractives of total weight of the wood. However, in knots, the extractives are concentrated and can reach as high as 40 wt %. When the wood is coated, the knot area is prone to exudate the extractives and bleed through the coating. Combined with the effect of UV radiation oxidizing some of these components, the typical result is brownish discoloration bleeding through the coated surface at the knot area.¹ Figure 1 shows the knots of pinewood, wood extractives, and the resulting knot bleeding effect through the coating.^2,3,4

Knot bleeding effects are a problem in the wood coating industry because they can significantly impact the appearance of the coatings, as shown in Figure 1. In addition, bleeding can compromise coating performance, causing a coating to become brittle, crack, or peel.⁵ The discoloration over the knots is typically not seen immediately but can take months. The time it takes for the discoloration to appear depends on several factors, including the wood species, environment humidity, temperature, and exposure to UV radiation.^6,7,8

Knot bleeding should be differentiated from tannin bleeding, which is another very common defect from extractives causing discoloration. Tannin bleeding is typically a problem for hardwoods such as oak, cedar, or merbau, where knots are not typically an issue.⁹ Figure 2 is an example of coated panels that show tannin bleeding.

Figure 3 shows an overview of different structures of wood extractives. Extractives can be grouped as either hydrophobic extractives, such as terpenes and resin acid, and hydrophilic components, such as tannins. Depending on the wood types and growth conditions, the exact composition of the extractives in the wood can vary.¹⁰

There are a few approaches historically used to prevent knot bleeding through a coating. One solution is to use a solvent-based two-part (2K) coating. These coatings typically have high crosslinking densities, which provide good barrier properties to hinder the extractives from migrating to the surface. However, their solvent emissions and high VOC contents are disadvantages. A second option is to use water-based cationic dispersions; however, this technology is not commonly used for industrial wood coatings, because they can require special equipment or additives.¹¹ A third solution is to use UV primers and topcoats. Like 2K coatings, UV coatings have high crosslinking densities, providing good barrier properties, but UV coatings require special curing equipment, which is often cost-prohibitive.

In this article, a new approach—an anionic acrylic dispersion—is introduced.

Continue reading in the of CoatingsTech.

In the past several years, many in-depth articles have been written across the industry heralding a wide variety of advances suggesting that biobased materials were on the verge of achieving explosive growth.

Some of these coatings manufactured from “natural” or ecofriendly sources are commercial and manufacturing success stories. Yet, many other developments and advancements are still waiting for the right resin, application, or manufacturing opportunity to manifest itself.

In 2019, an in-depth look at the role that academia plays in successfully making coatings “benign by design” hinted that success in mass utilization of biobased coatings must include a several pronged industry-wide approach.¹

Following up on those observations, this article further examines today’s biobased coatings world from the perspective of sustainability, standardization and industry/government/university collaboration as a basis for progress moving forward.

The Coatings Industry Sustainability Challenge

Since the turn of the century, every industry has made efforts to some extent to build sustainability into their product portfolios with varying degrees of success. Recycling was one of the initial movements to gain traction.

Simply put, if things could be reused or reinvented as a new use, less would end up in the burgeoning landfills—sort of like hand-me-downs of previous generations, but on a much wider scale.

Over the past 20 years, sustainability has evolved into a much more complex paradigm with four main pillars encompassing human, social, economic, and environmental interactions. Together, these four pillars intertwine to personify sustainability defined by the Oxford English Dictionary as “the avoidance of the depletion of natural resources in order to maintain an ecological balance.” Merriam-Webster further describes sustainability as “a method of harvesting or using a resource so that the resource is not depleted or permanently damaged.”

The coatings industry first approached sustainability through reductions in manufacturing emissions and commercially successful product developments such as water-based technologies that lowered VOCs.

Lately, the industry has continued sustainable market-wide initiatives by developing a portfolio of biobased coatings. These products attempt to substitute raw materials derived from fossil fuels with products made from plant-based biomass raw materials such as vegetable oils or sugars.

Key components of these initiatives are rooted in the use of renewable raw materials for producing biobased solvents, resins, additives, pigments, colorants, and crosslinkers. Lately, these bio-raw materials have tapped into the Renewable Carbon Initiative. Carbon dioxide that is released from a host of industrial and commercial processes is captured and used as feedstock for producing polymeric building blocks.

chnical successes but are presented and even marketed as niche products. Even today, 100% biobased coatings command only 1-3% of the global market volume. Market share rises to a generously estimated 10% if formulations that contain any amount of biobased raw ingredients are included, no matter how minuscule.

In order for biobased coatings to leap into a more mainstream view and command a larger market share, a number of hurdles still need to be overcome. The availability and price of biomaterials, as well as high technical requirements have had a limiting effect despite regulatory efforts to force the issue.

The fact is that the market for these coatings is still rather small, and production is more complex and more expensive than conventional products. Availability of renewable biomass materials would seem to be an easy challenge to overcome, but the fact remains that even renewable harvests take time to “grow” and can be thwarted by something as mutable as bad weather.

The industry is working on solutions that would be derived from biowaste, recycled content, and cellulose from carbon capture. But these solutions will take time to become practical realities.

The biobased coating market is still in its infancy primarily because the industry (which consists of individual companies trying to maximize market share and profitability) either cannot or is unwilling to invest heavily in biomass development for raw materials and in new manufacturing processes for those materials.

Research staffs across the industry have been slashed to the bare bones over the years. This leaves little time for the innovative, time-consuming, thoughtful development needed to ensure that biobased coatings and raw materials will ultimately achieve the same level of field performance and across-the-board acceptance as traditional products.

In short, the main challenges to large-scale acceptance of bio-coatings are consistent raw-material availability, affordable cost of manufacturing, comparable (or better) performance characteristics, and the time for scientists to innovate in this new dimension.

However, there are forces challenging the status quo within the coatings industry from other directions that have sparked a push to find new ways to address these dilemmas. Consumer awareness around “green” technologies is increasing, and customers are seemingly willing to reward companies that address those concerns by favoring their products.

Health problems emanating from well-publicized scandals such as excess formaldehyde in imported manufactured flooring and improperly constituted drywall that caused unexpected and enormous VOCs in the residential building industry further exacerbated the public’s growing demand for cleaner products.

Regulations are becoming more stringent around the entire paradigm of sustainability, driven in part by consumer demand and government initiatives. However, not all these challenges have resulted in punitive demoralizing actions or results.

Rather, paint companies have begun to approach the challenge differently by taking important smaller steps to develop crucial new molecules that act as “drop-ins” for segments of the paint recipe. This is especially important for balancing performance criteria and pricing competition with well-established petrochemicals.

Using drop-in building blocks provides a faster way to integrate biomass feedstock without the need to make large investments or drastically change high-capital investment production processes.

In addition, many of these monomers require UV light, oxygen, and renewable raw materials, providing more sustainable manufacturing and broader flexibility into a wide variety of markets. Examples of some of the more prominent biobased building blocks for resin synthesis are listed in Table 1.

Polyesters are formed from the reaction product of polyols and a di- or multifunctional acid or carboxylic acid and anhydride for ester linkages in the polymer chain.

Solventborne alkyds have been used in coatings for decades. However, stricter pollution regulations have nudged the development of waterborne alkyds or polyurethane dispersions (PUDs).

PUDs offer improved performance over alkyds due to the robust urethane linkages. They are linear or lightly branched and of relatively high molecular weights dispersed in water. Lower film-forming temperatures at higher glass transition temperatures can be achieved because urethanes bond strongly to water.

Latex particles swell, causing a plasticizing effect. This allows PUDs to have lower VOCs and lower film-formation temperatures together with improved mechanical, chemical-, and corrosion-
resistance properties than waterborne alkyds or conventional latexes.

Some of the more recent biobased resin technologies are low-odor, low or no VOCs, and free from phenolethoxylates (APE). Performance characteristics seem to approach solventborne counterparts, although long-term durability testing is still ongoing. In any event, this is a positive step in manufacturing biobased coatings that does not compromise performance standards.

Continue reading in the May-June 2022 digital issue of CoatingsTech.

The need for green and environmentally safe coatings creates an opportunity for biobased raw materials. Vegetable oil polyols (VOPs) are the major source of biobased raw materials for making polyurethanes¹.

Despite their wide commercial availability, they have not been utilized for making water-based polyurethane (PU) coatings, because, VOPs have no performance-enhancing functional group in the molecular architecture². Therefore, they are unable to meet the stringent corrosion-, UV-, and solvent-resistance performance requirements.

In this short communication, we present a new class of biobased polyol with a crosslinking functional group that is free from toxic chemicals and has superior performance. This is achieved by reacting a keto acid with a glycidyl functional fluids derived from biobased sources. We also present the utilization of the polyol in making water-based polyurethane dispersion (PUD).

SYNTHESIS OF THE POLYOL

In a typical example as shown in Scheme 1, levulinic acid is reacted with glycidol to produce 2,3-dihydroxypropyl levulinate (Levupol-G ).

Any epoxide functional fluid with two or more oxirane groups can be utilized and a myriad of polyol grades can be obtained. For example, the reaction of levulinic acid with epoxidized soybean oil would result in soy polyol with crosslinkable levulinic ester in the final product, as shown in Scheme 2.

As shown inĚýScheme 1ĚýandĚýScheme 2, the polyol has hydroxyl groups that are necessary to react with polyisocyanates to form the polyurethane backbone. It also contains the performance-enhancing keto group that reacts with crosslinkers and provide the high-performance features.

We adopted Green Chemistry Principles³Ěýand the benefits of the polyol are: (a) 100% atom economical as there are no byproducts (b) it does not use any solvents, and (c) the product formed is highly pure, and no additional purification step is required.

The proprietary catalyst employed to make the polyol is highly effective for the epoxide ring opening with carboxylate nucleophiles. As a result, the ring opening reaction is fast, well-controlled, and produces the desirable product in quantitative yield.

There are no undesirable polyethers formed during the synthesis that would have otherwise adversely affected the product performance and cost. It was found the catalyst we used accelerated the product formation significantly compared to commercial control, as shown inĚýFigure 1.

Figure 1