Photocrosslinking of an Acrylated Epoxidized Linseed Oil: Kinetics and its Application for Optimized Wood Coatings

Abstract

Over the past few decades, the industry developed an increasing interest in using renewable, bio-based thermosetting polymers as matrix systems for composites and coating systems. In the present paper an acrylated epoxidized linseed oil (AELO) was synthesized from epoxidized linseed oil (ELO) through ring opening of the oxirane group using acrylic acid as the ring opening agent. The synthesized AELO was mixed with three different photoinitiators and cured under monochromatic conditions (λ = 365 nm) at different light intensities and at different temperatures. The concentration of the initiators was aligned that all initiators absorb at 365 nm the same amount of light. The evolution of cure was monitored by using real-time infrared spectroscopy with a heated attenuated total reflection unit. The decrease of absorption in the measured spectra at 1,406 cm−1 was used to calculate the conversion of acrylic double bonds with increasing time of UV light exposure to get information about the cure kinetics for each AELO mixture at different light intensities and different temperatures. Wood substrates were coated in a preliminary work with the AELO mixtures and after UV-curing some technological coating properties like gloss, scratch resistance, adhesion, and solvent resistance were tested. In combination with the information about the cure kinetics in the present work the coating properties were correlated with the cure evolution and the final degree of double bond conversion. The found correlation can be used in the future to find optimized coating conditions for the AELO mixtures on wood substrates.