Cooperative Toughening Of PPS By Nano-SiO₂ And LDPE

At present, it has been an important object to obtain new polymer materials with excellent properties by means of modification of existing polymer materials. As the sixth high performance plastics, poly(phenylene sulfide) (PPS) has been widely used in auto, electronics industry and military field, due to its good combination of properties such as high thermal stability and electrical insulating ability, corrosion resistance and excellent self flame-retardance. But neat PPS has a deadly shortcoming of low impact strength, which limits the further use of it. Blending PPS with other plastics and filling with nanoparticles are most performed to improve the impact strength of PPS. However, conventional blending methods always decrease other properties while gaining the deserved ones. For example, elastomer can weaken the strength, modulus and thermal performances while improve the toughness significantly. Though nanoparticles can enforce and toughen the polymer simultaneously, it increases the toughness limitedly. How to obtain higher tensile or yield strength and thermal behavior as the impact strength increases has been an object hunted for by many PPS studiers on toughening modification.Based on the conventional elastomer toughening theory, thermoplastic low density polyethylene (LDPE) with branch chains and unsaturated double bonds was chosen as the toughening component. The LDPE together with rigid nano-SiO₂ particles is expected to have a synergistic toughening effect on PPS. The relationship between the mechanical performance and microstructure of composites was investigated by FTIR, SEM, DSC, PLM, et al. The toughening mechanism by SiO₂/LDPE composition dispersed phase was also explored and discussed. The main work and results obtained were listed as follows.1. For the first time, flexible LDPE and LDPE-melt-grafted nano-SiO₂ are used simultaneously to toughen and enforce brittle PPS. The impact strength of the composites was improved to 85.1KJ/m², which is 3.7 times of that of pure resin. The tensile and flexural strength was improved 27% and 9%, respectively. The formation of SiO₂-LDPE core-shell encapsulated structure and network structure with good interface adhesion in PPS matrix, and decrease of the size of spherilutes and crystallinity contributed the improvement of PPS.