Gel Coats and Vinyl Ester Resins

Long-Life Gelcoats and Vinyl Ester Resins with Antimicrobial Protection In addition to Eskim Kimya's broad product range, production capabilities include unsaturated polyester and vinyl ester resins, pigment pastes, thixotropic & acrylic polyesters and high-performance gelcoats backed by extensive technical knowledge. Beyond our Lloyd's Register-approved unsaturated polyester resin products, innovative gelcoats manufactured with antimicrobial technology have been added to our product portfolio.

1. Long-Life Gelcoats with Antimicrobial Protection 1.1. Gelcoats and Applications

Gelcoat is a material applied to the visible surface of a fiber-reinforced composite to provide a quality finish coat. It protects the composite structure against environmental conditions. Gelcoats are frequently used in the production of decorative composite materials. The consumer comes into direct contact with the outer surface (gelcoat). Today, gelcoats are manufactured with different properties for use in numerous industries. They are used in many applications where resistance to chemicals, high temperatures and impact is required [1]. In particular, products such as sinks, bathtubs, kitchen and bathroom countertops can be produced from fiber-reinforced composite materials with their outer surfaces coated with gelcoats to preference. Gelcoat can also be used directly as a raw material in artificial marble production. Gelcoats remain a preferred choice in products where they are used because they provide water absorption resistance, lightweight construction and long service life [2,3]. Sinks, bathtubs and countertops are continuously used fixtures. For this reason, pathogens develop on these items. For example, Escherichia coli is a common pathogen encountered in humans and animals. When humans become infected with this organism, conditions such as diarrhea, urinary tract infection and meningitis can occur. Similarly, S. Aureus is a dangerous pathogen that causes food poisoning in humans. This bacterium multiplies rapidly on surfaces in contact with food and can create a dangerous situation for human health. Kitchen countertops, bathroom sinks and countertops used in homes, offices and food production facilities do not have surfaces exhibiting antibacterial activity. In this context, Eskim Kimya has developed long-life antimicrobial-protected gelcoats [4].

1.2. Effective and Long-Life Antimicrobial Protection

Using this special gelcoat series provides the following highly effective benefits: • Provides long-lasting antibacterial protection against microorganisms without requiring additional processing. • Thus provides protection against microorganisms on the surfaces where it is applied. • Antibacterial efficacy does not shorten shelf life. • Additionally, it is also resistant to washing and abrasion. • Application conditions do not alter antibacterial efficacy.

1.3. Performance of Antimicrobial-Protected Gelcoats

Microorganisms multiply very rapidly on surfaces where they are present, and millions can develop from a single bacterium within 7 hours. Gelcoats protected with antimicrobial technology effectively prevent microorganism proliferation 24/7 from the start. Tests of Eskim long-life antimicrobial gelcoats against bacteria such as Escherichia Coli and Staphylococcus Aureus have been conducted according to ISO 22196 standard and confirmed to be effective up to 99.9% [5].

1.4. Safe and Effective

The performance and safety of the antimicrobial technology have been tested and approved by independent laboratories. The efficacy of Eskim antimicrobial-protected gelcoats has been approved according to ISO 22196 standard.

1.5. Test Results

Our long-life antimicrobial ISO/NPG-based acrylic-modified gelcoats are also Lloyd's Register-approved.

1.6. Industrial Markets and Applications

The applications for Eskim's long-life antimicrobial gelcoats include hospitals, vitreous ware, bathrooms, bathtubs and the food processing industry, among various other sectors, with active domestic and international use continuing [6].

1.7. Extra Protection

The antimicrobial efficacy of Eskim antimicrobial-protected gelcoats is integrated during manufacturing, providing durable protection against bacterial proliferation on the surfaces where it is applied.

2. Vinyl Ester Resins

Vinyl esters are organic compounds containing a vinyl functional group (R') and an ester group R-COO-R'. Therefore, vinyl ester resins can be considered as polyadducts of these simple unsaturated monomers (for example, polyvinyl acetate, polyvinyl benzoate). Vinyl ester resins also refer to polyadducts of diepoxide backbones containing only unsaturated monocarboxylic acids. These multifunctional unsaturated prepolymers can react with other unsaturated species (such as styrene) through radical polymerization on the double bond to produce the final cross-linked vinyl ester polymer [7]. Vinyl ester resins (VERs) are widely used as matrix systems in high-performance fiber-reinforced composites. Generally, they are obtained by reacting methacrylated epoxy systems with styrene in the presence of peroxide initiators and a catalyst. Styrene, as in unsaturated polyesters, acts both as a solvent/diluent to reduce viscosity and improve processability and as a chain extender for vinyl ester monomers. The monomers contain several reactive vinyl end groups that provide extensive cross-linking capability [8,9]. Vinyl esters are the reaction products of epoxy resins with unsaturated carboxylic acids. Simple diepoxide resins such as the diglycidyl ether of bisphenol A or extended high molecular weight homologues of bisphenol A can be used, as well as brominated analogues for flame retardancy or epoxy novolac resins for special properties such as higher heat resistance [10].

2.1. Advantages of Vinyl Ester Resins Over Unsaturated Polyester Resins:

Vinyl ester resins contain fewer C=C double bonds than unsaturated polyesters, resulting in lower cross-link density. This increases the impact resistance, elongation at break and tensile strength of vinyl ester-based materials. Vinyl esters also have improved chemical and hydrolytic stability compared to unsaturated polyester resins. This is because the unsaturated C=C double bonds at the end of the molecular chain are easily accessible during cross-linking, and therefore the conversion is practically complete after curing [11]. Vinyl ester resins generally offer toughness and chemical resistance properties superior to unsaturated polyesters. The epoxy resin backbone used in the manufacture of vinyl ester resins gives these resins durability and greater tensile elongation properties. The superior chemical resistance of vinyl ester resins (compared to unsaturated polyesters) is partly due to the absence of ester bonds in the epoxy backbone where polymer units are connected via phenyl ether bonds. Thus, it is much more resistant to degradation in many chemical environments and particularly in high pH alkaline conditions than ester bonds. Ester bonds in a vinyl ester resin are found only at the end of the molecule, minimizing the number of ester bonds that can be chemically attacked. Additionally, if the vinyl ester resin molecule is terminated with methacrylate groups, the spatially large methyl group attached to the methacrylate group sterically protects the ester bond from chemical attack [12]. Esvin-1020, one of the leading products from Eskim Kimya, is a Bisphenol A-Epoxy-based, medium-reactivity, Lloyd's Register-approved vinyl ester resin. It provides high flexibility with high mechanical strength properties. Therefore, Esvin-1020 reinforced with glass fiber/carbon aramid fiber is used in the production of machinery and electrical components that come into contact with water, such as wind turbines and large ship components. It is also resistant to corrosion even at high temperatures. It can be applied with hand lay-up, fiber spraying, cold press, pultrusion as well as RTM and casting methods.

References

[1] Di Tomasso C, Gombos ZJ, Summerscales J. Styrene emissions during gelcoating of composites. J Clean Prod 2014 ; 83:317–28. [2] Firdosh, S.; Murthy, H.N.N.; Angadi, G.; Raghavendra, N. Investigation of water absorption characteristics of nano-gelcoat for marine application. Prog. Org. Coat. 2018, 114, 173–187. [3] Yuharzi, M.Y.; Haeryip, S.; Muhammad Zaimi, Z.A.; Nilson, G.C.H. A review on gelcoat used in laminated composite structure. Int. J. Res. Eng. Technol. 2015, 4, 49–58. [4] Gascons, T.M. Assesment of Virtual Design and Manufacturing Techniques for Fibre Reinforced Composite Materials. Ph.D. Thesis, Universitat de Girona, Girona, Spain, February 2011. [5] Stoye, D.; Werner, F. Resins for Coatings: Chemistry, Properties and Applications; Carl Hanser Verlag: Cincinnati, OH, USA, 1996; ISBN 3-446-18489-9. [6] Airola, K.; Farm, O.; Mahbub, P.; Valtonen, E. Unsaturated Polyester Resin Compositions. U.S. Patent 6,617,417, 9 September 2003. [7] Bowen RL. U.S. Patent, A Comparatıve Study On The Propertıes Of Fıller-Added Methacrylate Polymers, 3, 066, 112; 1962. [35] Bowen RL. U.S. Patent 3, 179, 623; 1965. [8] Fekete F, Keenan PJ, Plant WJ. U.S. Patent, Curing of acrylated epoxy resin based on bisphenol-S., 3, 221, 043; 1965. [9] Flemming M, Ziegmann G, Roth S. Faserverbundbauweisen Fasern und matrices. Heidelberg, Berlin, NY: Springer; 1995. [10] Scott TF, Cook WD, Forsythe JS. Eur Polym J, Vinyl ester resin: Rheological behaviors, curing kinetics, thermomechanical, and tensile properties, 2002;38:705. [11] Cook WD. Polymer, Reaction behaviour and kinetic constants for photopolymerizations of multi(meth)acrylate monomers, 1992;33:2152. [12] Pritchard G, et al. Thermosetting resins for reinforced plastics. London: Applied Science Publishers; 1982. [13] Andreas Kandelbauer, Gianluca Tondi , Oscar C. Zaske and Sidney H. Goodman, Unsaturated Polyesters and Vinyl Esters, Handbook of Thermoset Plastics (Third Edition), 2014, Pages 111-172. Dr. Semra Özgün Köse Polyester R&D Manager Eskim Kimya