OPTIMIZATION OF CURING CONDITIONS FOR NANOCELLULOSE REINFORCED BIOBASED UNSATURATED POLYESTER RESIN

Abstract

Emerging efforts in the field of biocomposites established novel combinations of biobased matrix materials and reinforcements, as well as the optimization of curing conditions, to enhance their properties and expand their range of applications. The curing conditions of nanocellulose

reinforced biobased unsaturated polyester resin (UPR) based on itaconic acid and it derivatives’

were examined within this work. Since the curing process of biobased UPR requires the presence of both an initiator and an activator, the optimization was conducted in two phases. The first phase investigated the effect of different concentrations of an activator, cobalt octoate, (0.5, 1.0 and 1.5 mass%) with a constant concentration of an initiator, a mixture of dibenzoyl peroxide (DBP) and methyl ethyl ketone peroxide (MEKP) (DBP to MEKP ratio 1.5:1.0; 2.5 mass% total). The ratios of DBP and MEKP were varied in the second phase of experiments in the following manner: 2.5:0,1.75:0.75, 0.75:1.75 and 0:2.5 (keeping the total initiator mass% of 2.5). The effect of the different curing conditions on the UPR properties was monitored via the gel content analysis and the uniaxial tensile test. It was shown that the increase in activator concentration led to the decrease in gel content, tensile strength and elongation at the break. On the other hand, the increase in dibenzoyl peroxide concentration in the initiator mixture revealed enhanced overall mechanical properties. The optimal curing conditions were found to be 0.5 mass% of activator, and 1.75:0.75 DBP to MEKP ratio in the initiator mixture. Thereby obtained UPR biocomposite showed a significant increase in elastic attributes suggesting that these materials can be used where high elasticity is needed.