Part 2 – Application Areas
The coatings industry is moving towards greener and more sustainable technologies. Initial investigations demonstrate the potential for achieving the same level (or better) performance with bio renewable monomers than is currently achievable with oil-based equivalents. 2-OA and IBOMA have been used for coating applications. This is a very interesting approach because they are more hydrophobic than their traditional oil-based counterparts (BA and MMA, respectively). Hydrophobicity is a much-desired quality for many applications, but especially for coatings, as the water resistance plays a key role. This makes these monomers interesting beyond their greener origin, as the performance can be better. Gonzalez et al. used the IBOMA/2-OA pair to produce coatings by mini-emulsion polymerization with excellent anti-corrosive properties.
Commercial viability, however, ultimately depends on how “real” the interest is in such sustainable raw materials within the industry itself.
Part 1 Biobased polymers for sustainable coatings and related applications
Expectations of new monomers
From a polymerization viewpoint, new monomers must be easily processed and give clean, fully converted reactions. In an end application, the new monomers must offer comparable performance to current oil-based systems although, of course, if application properties were enhanced then this would be still more advantageous.
The new monomers must be readily available – initially perhaps not in large quantities, but there must be a clear plan to upscale new raw materials to meaningful quantities and within a defined timescale.
Finally, the price must be relatively close – or projected to be relatively close as the volume increases – to that of current oil-based equivalents. It is likely that these biobased monomers will, however, continue to increase in volume and so eventually reduce in cost towards that of mainstream monomers.
Decorative Coatings
In one study, oil-based acrylates were substituted by 2-OA in three alternative monomer systems. In all cases the polymerization proceeded smoothly to give clean, low-coagulum, low free-monomer systems and with consistent particle size. In general, it was found that direct w/w substitution of BA by 2OA gave slightly higher MFFT/Tg results (due to the difference in the theoretical values for BA (-55 °C) and 2-OA (@-44 °C). This can be adjusted by a modest increase in the level of 2OA (such as in the samples ST3 and PA3 described below).
Industrial Wood Coatings
2OA shows proven compatibility with a variety of monomers and stabilizing systems. Resultant products polymerize smoothly and give clean, fully converted polymers. Application results suggested there are no significant drawbacks in using 2OA and, indeed, in many systems the more hydrophobic nature of the monomer could be of benefit in terms of better blanch resistance, lower water uptake, higher response to HEUR thickeners. IBOMA, however, may subtly change the reaction/morphology (of a multiphase polymer) and this then affects the end properties. Further investigation/refinement of the recipes will be required to produce a comparative evaluation against traditional reference materials.
Solvent-based Coatings
Solvent-based coatings polymers containing IBOMA typically have a lower viscosity than those made from other monomers at equal solids levels. This enables lower VOC paint formulations, since higher non-volatile content can be achieved at the same application viscosity. Higher solids coatings have many advantages, including lower solvent evaporation and higher dry film thickness per coat during application. These low VOC coatings also have better durability, because IBOMA increases a polymer’s resistance to breakdown by UV radiation in exterior uses.
Waterborne Coatings
Emulsion polymerization of (meth)acrylic bio-based monomers is a promising method to obtain waterborne coatings with reduced carbon footprint. However, the high hydrophobicity of some bio-based monomers can hinder the straightforward incorporation of such monomers in waterborne dispersions.
IBOMA readily polymerizes with other acrylic and methacrylic functional monomers under the conditions commonly used to manufacture latex polymers for coatings. In these polymers, it offers the same performance enhancements as described above for solvent-borne coatings, that of hardness, scratch and mar and weatherability. Improved adhesion to a variety of substrates, and increased flexibility also result from the incorporation of IBOMA. This improved flexibility and adhesion can, for example, give an exterior architectural coating better resistance to cracking and chipping.
UV Cure Coatings
Common applications for UV-cured coatings include hard coats for automotive headlight lenses. IBOMA is valuable as an ingredient in UV-cured coatings, as it will provide hardness and scratch resistance in the cured film. Excellent photo-stability is another property IBOMA can add. Oligomers containing IBOMA have lower inherent viscosity than comparable molecular weight versions made with other monomer compositions. Monomeric IBOMA can be used as a fast-reacting diluent to lower the viscosity of UV-curable polymer and oligomer solutions which facilitates easier handling and better application of the formulated coating.
Adhesives
Pressure-sensitive adhesives (PSAs) are present in a large variety of applications in science, industries, and every-day life, such as packaging, labels, sticky notes, and plastics wraps. The global PSA market is growing rapidly with an expected market by now of $13 billion. PSAs are usually viscoelastic materials that can stick firmly to a wide range of substrates with the application of a light pressure for a short contact time, and that can be easily removed from the substrate without any residue. They can be produced via hot-melt, solution polymerization and emulsion polymerization techniques. Recently, the latter has attracted much interest, due to its relatively more environmentally friendly process. Hence, the focus of the current study is on latex-based PSAs.
Major materials used in PSA formulations are natural rubber, petroleum-based styrene–butadiene–styrene (SBS), polyisobutylene (PIB), nitrile rubber (NBR), polyurethanes and polyacrylates. Polyacrylates are widely used due to their good stability over a large temperature range, high flexibility and good resistance towards degradation.
Cheg Fang et al have reviewed the replacement of methyl methacrylate by sustainable bio-based isobornyl methacrylate (IBOMA) as a hard monomer in the application of acrylic latex PSA.
The influence of bio-based IBOMA on the viscosity and particle size of the latexes and the gel content, sol molecular weight (Mw, Mn) and adhesive properties (loop tack, peel strength and shear strength) of the PSA copolymers were investigated. Results were compared with those obtained when using traditional petroleum-based hard monomer MMA.
NMR analyses confirm that IBOMA may be successfully introduced into the PSA copolymer through emulsion polymerization.
In the area of pressure sensitive adhesives (PSAs), corona treatment or other preprocessing on the carrier is commonly utilized to enhance the interaction between the adhesive layer and the carrier, with complicated procedures and operations.
One-pot emulsion polymerization using n-butyl acrylate, isobornyl methacrylate (IBOMA), 2-hydroxyethyl acrylate and acrylic acid has been conducted in the presence of a reactive emulsifier SR-20 to obtain a reinforced adhesive tape. It is found that the emulsion has good stability, especially freeze-thaw stability, which is helpful to the fabrication of PSAs. Secondly, IBOMA increases the binding strength between adhesive layer and adherend. Thirdly, the tapes produced using the above emulsion can be removed many times, with no PSAs residue on the adherend even when coated on untreated PP, which showed the potential of recycling and environmental protection. Thus, these properties make the polyacrylate emulsion have great potential for practical applications.
Anti-fouling Resins
Marine biofouling can cause biocorrosion, resulting in degradation and failure of materials and structures. Submerged hull surfaces are highly susceptible to biofouling. Marine fouling organisms attach to the hull surface, grow and propagate, which will lead to the aggravation of surface corrosion, the exacerbation of surface friction resistance, and increase of fuel consumption.
In order to prevent sea creatures from attaching to the surface, in this work, a new environmentally friendly antifouling coating by incorporating antibacterial polymers and natural antifouling agents has been designed and synthesized ((Fig 1 and Table 1). The novel approach employed was synthesis of an environmentally friendly anti-fouling coating based on an antibacterial polymer (such as IBOMA) and a natural antifouling agent (such as camphor). Camphor is a terpene natural organic compound, which can be extracted from the trunk of Cinnamomum camphora and can also be synthesized in large quantities. The study highlights the environmentally friendly antifouling coating as a potential candidate and efficient strategy to prohibit biofouling in seawater. It has been demonstrated that the antifouling polymer can be released slowly in a controlled manner.
|
1 | 2 | 3 | 4 | 5 | |
|
12 | 24 | 36 | 36 | 36 | |
IBOMA | 150 | 150 | 150 | 100 | 50 | |
BMA | 138 | 126 | 114 | 164 | 214 | |
Xylene | 300 | 300 | 300 | 300 | 300 |
Table 1: Compositions of resins prepared by free radical copolymerization. To get sample 3c, 10% rosin is added to sample 3
Figure 1 visualizes surface roughness measurements of anti-fouling resins taken from an ultra-depth-of-field electron microscopy. The contact angle of sample 3c (with extra 10% rosin) decreased most, suggesting that the auxiliary resin itself was hydrophilic, which further enhances the effectiveness of the coating by reducing the chance of foulers being able to attach initially. Source: Ref 3 (Marine biofouling).
References
- IBOMA – The Wonder Monomer Isobornyl Methacrylate https://www.ulprospector.com/knowledge/14503/pc-iboma-the-wonder-monomer-isobornyl-methacrylate/
- Toward replacement of methyl methacrylate by sustainable bio-based isobornyl methacrylate in latex pressure sensitive adhesive
https://www.sciencedirect.com/science/article/abs/pii/S0143749620300865 - Terpolymer resin containing bioinspired borneol and controlled release of camphor: Synthesis and antifouling coating application
https://www.nature.com/articles/s41598-020-67073-8 - Polyacrylate emulsion containing IBOMA for removable pressure sensitive adhesives
https://onlinelibrary.wiley.com/doi/10.1002/app.42886 - Biobased Polymers for Sustainable Coatings
https://www.pcimag.com/articles/103863-biobased-polymers-for-sustainable-coatings
The views, opinions and technical analyses presented here are those of the author or advertiser, and are not necessarily those of ULProspector.com or UL Solutions. The appearance of this content in the UL Prospector Knowledge Center does not constitute an endorsement by UL Solutions or its affiliates.
All content is subject to copyright and may not be reproduced without prior authorization from UL Solutions or the content author.
The content has been made available for informational and educational purposes only. While the editors of this site may verify the accuracy of its content from time to time, we assume no responsibility for errors made by the author, editorial staff or any other contributor.
UL Solutions does not make any representations or warranties with respect to the accuracy, applicability, fitness or completeness of the content. UL Solutions does not warrant the performance, effectiveness or applicability of sites listed or linked to in any content.