Paint formulation and drying conditions have a strong influence on the final performances of the coating, yet there are few measurable variables between the formulation stage to the final film performance. The fast drying of thin films of paint, such as those used in automotive coatings, results in higher potential for fluid instabilities that often lead to defect formation in the final coating. The rheological properties of paint prior to and during drying is key in understanding the transition from a fluid coating to a solid film and is necessary for defining the connection between formulation and drying conditions, defect formation, and consequently the final paint performance. Two recently studies will be highlighted to demonstrate the power of optical characterization within these films as they dry. In the first study, tracking the Brownian diffusion of tracer particles in the fluid is used to characterize the properties of coating formulations in both quiescent liquids and during drying.

This technique, known as microrheology, is especially challenging when the evaporative flux causes partitioning and strong Marangoni stresses that result in internal convection. These fundamental investigations reveal the time-evolved rheological properties of a drying film. In the second study, particles such as pigments within the formulation themselves contribute to the evolving rheology and final microstructure of the dried film. Their rheological contribution changes drastically when the particles whether they are repulsive and stable or attractive and form aggregates within the solution. We use high speed laser scanning confocal microscopy to determine the particle positions with nanoscale precision that gives simulation-like detail of the microstructure evolution. A clear difference in microstructure evolution between the drying of stable vs. aggregated suspensions is apparent, leading to different properties of the final dried film.

The coating industry is increasingly aware of the need to protect the environment and is constantly striving to ensure the safety of the industry and the health of consumers, which demands environmentally friendly coatings. Different from conventional polyurethanes, non- isocyanate polyurethane (NIPU) is the polyurethane produced from the isocyanate-free route. In addition, waterborne polyurethane (WPU) is in demand in the market coming from the pressure on reducing the usage of volatile organic components in coatings.

Combining the features of NIPU and WPU, waterborne non-isocyanate polyurethane has been developed and studied. This presentation will introduce 2K and 1K waterborne NIPU epoxy hybrid coatings that are recently developed at Dr. Zhou’s group at The University of Akron.

The 2K waterborne NIPU epoxy hybrid coatings were prepared from waterborne amine- terminated NIPU and waterborne epoxy chain extender. The waterborne amine-terminated NIPU were derived from diglycerol decarbonate, 3,3’-diamino-N-methyldipropylamine, and fatty acid diamine. The waterborne epoxy chain extender was synthesized from diethanolamine and trimethylolpropane triglycidyl ether. The 1K waterborne epoxy hybrid coatings were synthesized from 3, 3’-diamino-N-methyldipropylamine, fatty acid diamine, cyclic carbonate, and two epoxy resins including bisphenol A diglycidyl ether and trimethylolpropane triglycidyl ether.

Different formulations of the waterborne NIPU epoxy hybrid coatings were designed including different ratios of soft and hard segments, different urethane contents, and different functionalities and structures of the hybridized epoxy. The coatings can achieve a broad range of thermal and mechanical properties and exhibit excellent general coating properties in hardness, adhesion, and chemical resistance, which reveal similar performance with the conventional isocyanate-based waterborne polyurethanes.

For last few decades industry is looking for new oleochemical materials as an alternative to crude oil-based counterparts. Since the early 90s renewable raw materials, most commonly vegetable oils, became increasingly attractive for making oleo-based materials, particularly biobased polymers.

At North Dakota State University, one-step method that converts fatty acid esters of plant/vegetable oils into plant oil-based acrylic monomers (POBMs) for free radical polymerization was recently developed. Currently exemplified for more than ten oils (including soybean, linseed, corn, sunflower, canola, high linoleic soybean oil, high oleic soybean oil, camelina, olive oil etc.) POBMs can be applied in the production of latexes that utilize acrylic counterparts and other polymers. POBMs offer unique functionality due to nature of double bonds, which allows “on-demand’ cross-linking.

POBMs fragments provide internal plasticization, hydrophobization, balance thermomechanical properties to allow polymeric materials with essentially different viscoelastic behavior, also enhance polymer adhesion and biodegradability of polymeric materials. Depending on the plant oil(s) (chemical structure, fatty acids composition) used, properties can be tailored based on behavior of the fatty acid side chains, and their amount of unsaturation.

It is expected that plant oil-based polymer emulsions can broaden an opportunity to substitute synthetic petroleum-based polymers in materials, and enhance materials performance without additional costs. Based on the obtained results, up to 70 wt% of POBM can be incorporated into copolymerization with commodity petroleum-based counterparts, while maintaining a required high level of latex performance.

Synthesis of highly renewable latexes based entirely on biobased comonomers including POBMs has been already demonstrated as well. POBMs performance opens wide opportunities in tailoring commercially valuable products Their potential for use in coatings, adhesives, bioplastics, personal care products is being investigated.    

A challenge of broad interest both academically and industrially is the small length scale characterization of coatings, their interfaces with air, and their interfaces with underlying substrates. The presentation will briefly introduce a few examples of what can be achieved with innovative X-ray and neutron scattering techniques. Both X-rays and neutrons can penetrate inside coatings and reach the buried interface with the substrate.

In one example, the uniformity with depth of structure and crosslinking density in plasma polymerized coatings are quantified using neutron reflectometry. The measurements show that the structures of films at the air and substrate interfaces are different than the structure in the middle of the coating, with the interfacial structures having lower crosslink density. A second example demonstrates the ability of both X-ray reflectometry and X-ray off-specular scattering to provide information on how water penetrates through a coating.

A third example considers X-ray scattering measurements that follow how the interface between metal and an epoxy coating change with exposure to salt solution during early stages of corrosion before any degradation is evident from outside the coating.

The National Science Foundation (NSF) recently funded the Center for Bioplastics and Biocomposites (CB2) for a Phase II Industry University Cooperative Research Center (I/UCRC). The Center has four sites, North Dakota State University (the lead site), University of Georgia, Iowa State University, and Washington State University.

All sites receive some funding from NSF; however, the research is solely driven and funded by the approximately 30 member companies including, among others, Sherwin-Williams, BASF, 3M, AkzoNobel, Amazon, Ford Motor Company, Hexion, Evonik, Hyundai, Kimberly-Clark, and John Deere. These companies develop and select project concepts, as well as guide the research at the four sites.

While Center projects cover the broad areas of bioplastics and Biocomposites, the Center has funded projects focused on aspects of sustainable coatings since its launch in 2015. Projects have included work on developing novel tools for life-cycle assessment of bio-based coatings and their raw materials and novel plant-oil based latexes. Other projects have focused on transparent waterborne coatings, zero-VOC powder coatings, new bio-based monomers for durable coatings and the use of chitin nano fibers for coating enhancement.

Shark Solutions has partnered with ChemQuest Technology Institute (CQTI) to perform a blind study in order to evaluate interior architectural wall paint formulations with binder systems composed of or containing recycled polyvinyl butyral (PVB).  PVB is recycled from laminated glass from windshields and building glass and upcycled into Water Borne dispersions offering superior properties based on their chemistry. Dispersions from recycled PVB also allow for low (down to <1 g/L) VOC paint formulations that do not need to rely on coalescing agents.  Testing covered for 8 samples: Rheology stability, pH, wet scrub-resistance, color properties, wet and dry opacity, adhesion to wallboard, dry time, gloss, hardness, minimum film formation temperature, blocking and stain resistance.  These PVB based dispersions are shown to perform competitively against a control as well as 2 commercially available off-the-shelf paints using binders composed of Styrene Acrylic and pure Acrylic chemistries. 

Produced from agricultural waste, derivatives of levulinic acid such as butyl levulinate, ethylhexyl levulinate, and isoamyl levulinate can be used as sustainable alternatives to materials such as 2,2,4-trimethyl-1,3-pentanediol diisobutyrate and dipropylene glycol n-butyl ether for water-based emulsions. Their limited water solubility assists in demonstrating a high level of effectiveness in lowering the MFFT as well as frequently enhancing properties of the film, notably the hardness. In many resin systems this technology improves the overall coalescing efficiency to the extent that reduced loadings can be used to achieve equivalent performance. The demonstrated performance, along with the resultant lower use level, address industry needs to reach targeted cost-performance criteria with sustainable chemistry. Levulinates have an excellent health, safety, and environmental profile and contain up to 100% bio-based carbon, facilitating replacement of traditional petrochemical coalescing agents. This paper will provide a detailed discussion of the technology, application case studies, and environmental impacts.

Lignin is the most abundant aromatic natural polymer in the world, with the potential to replace petrochemicals in polymeric resin formulations. Lignin is currently produced/isolated from wood and agricultural residues (as a byproduct) during chemical pulping and lignocellulosic ethanol productions. The complex polyphenolic structure of lignin makes it a great candidate to substitute fossil-fuel-based raw materials in resins. This talk is focused on our recent results in replacing 100% of phenol in phenolic resins, 85-100% of polyol in polyurethane resins (both in solvent-based and water-based formulations), and 100% of bisphenol-A in epoxy resins using unmodified lignins. Depending on the biomass source and isolation method, the properties of lignin vary significantly. We characterized a wide range of technical lignins and chose the most suitable ones for each specific application. The performances of developed lignin-based resins (phenolic, PU, and epoxy) were measured and compared with commercially available resins in the market.  

In becoming responsible corporate citizens, industries are retooling how products impact the environment. The first iteration of this restructuring was “going green,” which often was simply making more environmentally friendly decisions. “Green” philanthropic programs have morphed into “sustainable” business models, evolving from an option into a commitment. With this in mind, the U. S. Department of Agriculture created the BioPreferred® Program, designed to reduce reliance on petroleum, and increase use of renewable materials. Manufacturers with aggressive sustainability goals are now seeking solutions to meet the BioPreferred® Program’s standards. To address this need, Arkema developed a 97%+ bio-content polymer. This presentation will discuss developing high performance, high bio-content coatings, utilizing this novel technology. This technology is straightforward to use and, when compared to other approaches, offers a quick path to market. Blending with a sustainably-sourced, high bio-content alkyd is a viable way to introduce bio-content, while maintaining performance.

Market development in Non-Isocyanate (“NISO”) coatings has increased over the past few years due to the health and safety concerns associated with isocyanates. Use of isocyanates in spray coatings can cause allergic skin reactions and irritation of the respiratory system in workers, and the risks need to be mitigated by using expensive personal protection equipment and training. Challenges persist, though, in meeting required performance standards in a variety of applications. Nagase Specialty Materials NA LLC set out to develop preliminary formulations using a specific subset of the Denacol™ aliphatic epoxy product line as ambient crosslinking agents in NISO coatings used in outdoor applications which require a high degree of weather resistance. Panels made using these preliminary formulations were then put through a battery of optical, physical, and chemical tests. Suitability of formulations to specific market applications based on results and possible areas of improvement to the preliminary formulations were reviewed.

The characterization of the microscopic dynamics of coatings materials and polymer films is a very important step in every new development or quality control. We use a dynamic light scattering technique (Diffusing Wave Spectroscopy) to investigate the microstructure evolution (evaporation, packing, coalescence…) of a large panoply of materials between RT-250°C and with humidity control. This technology allows to detect the characteristic steps (Curing/drying time, phase transition…) with a very handy sampling protocol on any substrate and a very high sensitivity. We offer a new in-situ, non-invasive and handy method to better understand your different materials, allowing to:
-  Monitor and know precisely the curing and drying kinetics
-  Determine the characteristic times of the film forming process
-  Analyse from room temperature up to 250°C with humidity control
-  Evaluate the impact of the formulation and time and temperature parameters on the formation of materials
-  Optimize the manufacturing protocol chemistries. 

One of the multifunctional surfactants used for the physical and chemical characteristics improvement of polymer films, papers, and cosmetics is surfactant cation copolymer containing hydroxyethylcellulose and dimethydiallyl-amonium chloride (Polyquaternium-4; PQ4). However, the concentration of the salts on the film is very low and it has become a challenge for scientists to develop a practical and rapid method for the determination of the coating. In this study, the Pyrolysis-GC/MS is used for such analysis. The method requires very little sample preparation. The multi-mode micro-furnace pyrolyzer with different modes of operations including evolve gas analysis (EGA), flash pyrolysis, thermal desorption, heart cutting allows users to choose among the techniques for their analysis purposes. The first step is to perform an EGA using temperature programs. Based on EGA thermogram, Heart cutting is then utilized for the trace determination of PQ4 surfactant on the film. The result obtained proves the reproducibility of the technique.

Non-Isocyanate Polyurethane (NIPU) coatings are increasingly important due to their low toxicity and sustainable attributes. While several alternative routes for the synthesis of NIPU have been established, their successful exploitation in advanced water-based, UV-cure, or high-solid coating technologies requires customization of their polymer structure, morphology, and crosslinking functionalities. Building on our previous work on NIPUs derived from cyclic carbonate/amine route, this presentation will discuss how NIPUs are selectively functionalized for UV-curable (-acrylate), moisture-curable (-silane), and ambient temperature curable (-acetoacetate – click-chemistry) coating systems. By optimizing chemical structures and functionalities of NIPU and incorporating dual-cure mechanisms, coatings with an outstanding balance of application and performance properties have been achieved. Such coatings have the potential to replace conventional PU coatings for many end-use industrial applications.

TiO2 pigments are known to have several effects on paint durability.  As a strong UV light absorber, TiO2 protects underlying resin from direct interactions with the UV component of sunlight.  However, TiO2 can convert some of the UV light energy into chemical energy in the form of radicals, which can then attack the binder.  In addition to the inherent photoactivity of the TiO2 pigment, which can be partially modified through a surface coating, the degree of TiO2 dispersion can also affect paint durability.  While it would be very useful to the formulator to understand the relative importance of these two effects on paint durability, they are typically quite difficult to identify/separate.  Here we present a technique to make this separation and show how this information can be used to optimize paint durability.

Bisphenol-A based materials are getting phased-out in various applications including in metal packaging coatings. Simultaneously, steel packaging manufacturer, can makers, and coating formulators are wrestling with simultaneous challenge coming from shifting regulatory pressures driving substrate replacement towards Chromium-free passivation alternative (CFPA) to comply with legislative moves in various territories. Eastman Chemical is actively participating in the development of next generation polyester Bisphenol-A non-intent (BPA-NI) resins technology that can deliver improved resistance to food sterilization, long-term shelf stability, with balanced flexibility and toughness critical to withstanding aggressive canning process while adapting to this new challenge associated with substrate development. Here, we employ accelerated pack test, electrochemical impedance spectroscopy (EIS), and fitness-for-use testing to understand and analyze suitability and performances of several BPA-NI solutions on conventional substrate and new CFPA substrate. This work will provide understanding of compatibility, benefits and limitations of various BPA-NI solutions.