Influence of initiator on the curing of unsaturated polyester resin at 100 °C

Abstract

Sheet molding compound (SMC) parts are fiber-reinforced unsaturated polyester (UP) composites molded at 140-170 ∘ C under a pressure of 60-100 bar. For economic and ecological reasons, the aim of this research project is to develop new SMC formulations to modify the molding conditions. For this, SMC formulations were modified and optimized to decrease the molding temperature to 100 ∘ C. The strategy was to change the catalytic system (peroxides) in order to obtain highly reactive formulations at 100 ∘ C. First, the temperatures of initiation of the reaction were determined by rheological and DSC measurements for each peroxide. Second, the UP resin crosslinking kinetics were measured for the various peroxides during an isothermal curing at 100 ∘ C. The results obtained with the three experimental methods are compared and discussed. Finally, the laboratory analyses were validated by SMC molding trials.

Low-Density Unsaturated Polyester Resin with the Presence of Dual-Initiator

“…Among different curing processes of UPR at different temperatures, there were three different types of initiators, which were low-temperature (40–70 °C) initiators [ 4 , 12 , 13 , 14 , 15 ], medium-temperature (70–130 °C) initiators [ 16 , 17 , 18 , 19 ], and high-temperature (≥130 °C) initiators [ 20 , 21 , 22 , 23 ]. Regarding commercial low-temperature initiators, there are cyclohexanone peroxide (CYHP), methyl ethyl ketone peroxide (MEKP), and benzoyl peroxide (BPO), which were applied together with accelerators [ 12 , 24 ].…”

“…Regarding medium-temperature initiators, tert-butyl peroxy-2-ethylhexanoate (TBPO) and benzoyl peroxide (BPO) are the two typical examples [ 16 , 18 ]. In the range of high temperatures, tert-butyl peroxybenzoate (TBPB), peroxy ketone peroxide, and peroxy carbonate (BIC) are the three typical commercial initiators [ 23 , 25 ]. Currently, one single initiator is the traditional way to initiate the cross-linking of UPR [ 14 , 18 , 26 ].…”