Synergistic action of initiator and accelerator on curing thermodynamics and kinetics of chopped carbon fiber-reinforced low-density unsaturated polyester resin with rapid polymerization

Facile preparation of chopped carbon fiber-reinforced low-density unsaturated polyester resin (CCFR-LDUPR) composite samples were realized under the synergistic action of initiator and accelerator at a low temperature of 58.0 ℃ and with NH4HCO3 as the foaming agent. CCFR-LDUPR composite sample presented excellent properties of ρ being 0.58 ± 0.02 g cm−3 and Ps being 53.56 ± 0.83 MPa g−1 cm3. Curing thermodynamics analysis revealed that the crosslinking spontaneity and curing tendency of unsaturated polyester resin did not be influenced by the synergistic effects of initiator and accelerator. The crosslinking of unsaturated polyester resin was retarded by the decomposition of NH4HCO3 and the steric retardant of chopped carbon fibers. Curing kinetics results illustrated that under the synergistic action of initiator and accelerator, the steric retardant of chopped carbon fibers to unsaturated polyester resin cross-linking was weakened, values of E and ΔG were both reduced, and the crosslinking of unsaturated polyester resin was accelerated, which was different from that with the only presence of initiator. Under such specific curing thermodynamics, the specific curing kinetics, and proper content of chopped carbon fibers, unique “plate microstructure” emerged layer by layer in resin matrix and regular “dimples” distributed in fine lines adhered to chopped carbon fibers. CCFR-LDUPR composite samples exhibited excellent compressive strength and specific compressive strength under the rapid curing process of unsaturated polyester resin; however, the curing reaction enthalpy (ΔH) was almost the same as that of slow curing process of unsaturated polyester resin.