Abstract
UV curable PUA resin was successfully synthesized from polyol based on sustainable resource originated from itaconic acid (IA), isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate (HEMA). A polyol was synthesized by condensation reaction of IA with 16-hexanediol in the presence of p-Toluenesulfonic acid (pTSA). The synthesized PUA resin was characterized for its structural elucidation by using Fourier Transform Infrared Spectrophotometer (FTIR), 1H and 13C NMR spectroscopy. The synthesized UV curable PUA resin was incorporated in varying concentrations in conventional PUA coating system. The effects of varying concentration of synthesized UV curable PUA resin on rheology, crystallinity, thermal and coating properties were evaluated. The rheological behavior of the resins were evaluated at variable stress and result showed decrease in viscosity of resin as concentration of synthesized UV curable PUA resin increases in conventional PUA resin. The cured coatings have been evaluated for glass transition temperature (Tg) and thermal behavior by differential scanning calorimeter and thermogravimetric analysis respectively. The degree of crystallinity of the coatings was determined from X-ray diffraction patterns using the PFM program. It was found that increase in the mass proportion of IA based PUA in coatings, the coating becomes more rigid and crystalline. The synthesized UV curable PUA coatings showed interesting mechanical, chemical, solvent and thermal properties as compared to the conventional PUA. Further, cured coatings were also evaluated for gel content and water absorption.
Highlights
The coatings are widely used for various purposes such as decoration, protection, and some specific functions
The UV curable polyurethane acrylate (PUA) resin is successfully synthesized from bio-based itaconic acid (IA) by simple condensation reaction in presence of p-Toluenesulfonic acid (pTSA) catalyst
The IA based UV curable PUA resin synthesis is characterized by physicochemical analysis and further confirmed by Fourier Transform Infrared Spectrophotometer (FTIR), 1H and 13C-nuclear magnetic resonance (NMR) spectroscopy
Summary
The coatings are widely used for various purposes such as decoration, protection, and some specific functions. To gain the application viscosity volatile organic chemicals (VOCs) are added in most coating formulations, which can be evaporated, and transport to atmosphere at ambient conditions Such materials have been making many pollution risks such as: their ability to forming undesired photochemical ozone smog, and the potential to cause carcinogenic and mutagenic.[1,2] Environmental concerns and health related issue have stimulated researcher to develop environment friendly coatings with low or no VOC content.[3] To fulfill these requirements, researcher developed various type of coating such as high solid, water dispersible,[4] powder,[5] radiation (UV/EB) curing coatings.[6,7] Among them, UV-curing technology has been commonly used in various industrial sectors to achieve an ultrafast hardening of protective coatings, printing inks, adhesives, varnishes and composites. PUA resins are usually prepared by the reaction of a polyol with a diisocyanates to yield an isocyanate terminated oligomer and subsequently isocyanate terminated groups utilized to react with hydroxyl functional acrylic monomers incorporated the unsaturation at the end of the polymer backbone.[10]
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