A novel biobased prepreg from flax and thermosetting poly(lactic acid): Synthesis, curing and processing

Flax fiber-reinforced thermosetting poly (lactic acid) (PLA) composites, a fully degradable plant fiber-reinforced composites, were prepared by hot-melt pre-impregnation, which consists of two processes, the preparation and curing of the prepreg. Firstly, thermosetting PLA with intrinsic flame-retardancy was synthesized and its molecular structure was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy. The non-isothermal viscosity of the thermosetting PLA resin system was investigated to determine the film-formation temperature (55 degrees C) and the impregnation temperature (65 degrees C) during the preparation of the prepreg. On this basis, novel flax fiber-reinforced thermosetting PLA prepreg was prepared and its curing kinetics was investigated using differential scanning calorimetry (DSC). A curing simulation model of the prepreg was developed using the finite difference method, which was used to design and optimize the curing cycle of the flax fiber-reinforced thermosetting PLA prepreg. Finally, the flax fiber-reinforced thermosetting PLA composites with different lay-ups were prepared using the optimal curing cycles and their mechanical and flame retardant properties were investigated, with tensile and flexural strengths up to 128 MPa and 98.8 MPa, and flame retardant ratings up to UL-94 V-1. Overall, the results of this study can provide an important basis for expanding the application of flax fiber reinforced thermosetting PLA composites.