No abstract

In order to increase the applicability of wollastonite (Wo) in polycarbonate (PC) polymer, surface modification of Wo was carried out using different modifiers containing silane coupling agent KH570, stearic acid (SA), and sodium dodecylbenzene sulfonate. The physical, physic-chemical, and application properties of modified Wo were evaluated. Results showed that KH570 modified Wo had narrower particle size distribution, higher absolute zeta potential and were more evenly distributed. Scanning electron microscope study confirmed their changes in morphology and aspect ratio during the modification process. The tensile strength of Wo/PC composites, in which KH570-modified Wo was used were superior to those in which original Wo or other modifiers modified samples were used. The maximum tensile strength of 65 ± 1 MPa was obtained by adding 15 wt% KH570-modified Wo. Thermal analysis indicated that adding Wo to the polycarbonate increased the residue content but decreased the thermal decomposition temperature and glass transition temperature slightly, regardless of unmodified or modified Wo. These results indicated that the well-modified Wo mineral had the potential to replace expensive carbon and glass fibers as fillers in polycarbonate products.

Vinyl chloride-diallyl phthalate (VC-DAP) suspension copolymerization was carried out in a 5-L autoclave and 200-mL stainless steel vessel at 45°C. The apparent reactivity ratios of VC-DAP suspension copolymerization system were calculated as r VC ϭ 0.77 and r DAP ϭ 0.37. It shows that VC-DAP copolymer contains no gel when the feed concentration of DAP ( f 2 0 ) is lower than a critical concentration ( f cr , inside the range of 0.466 -0.493 mmol/mol VC at 80 -85% conversion), the polymerization degree (DP) of copolymer increases with the increase of f 2 0 and conversion. VC-DAP copolymer is composed of gel and sol fractions when f 2 0 is larger than f cr . The DP of sol fraction decreases as f 2 0 increases, but the gel content and the crosslinking density of gel increase. The gel content also increases as conversion increases. The results also show that the index of polydispersity of molecular weight of sol changes with f 2 0 , a maximum value appears when f 2 0 is close to f cr .