Carbon black filled polypropylene (PP), ethylene vinyl acetate copolymers (EVA) and their blends.

摘要

Plastics are generally considered as insulating materials. Some well known polymers, such as Polystyrene(PS), Poly(vinyl chloride)(PVC), Polypropylene(PP) and Polyethylene(PE), are almost perfect insulators, but if tiny electrically conductive fillers are compounded into their nonconductive matrices above a critical threshold concentration, they will become semi-conductors or conductors. This is well known as percolation theory, which, in terms of the coalescence of particles to form conducting networks, facilitate the electrical conduction through the composites.; The purpose of the study was to investigate the processibility, mechanical, and electrical properties of carbon black powder filled ethylene-co-vinyl acetate (EVA) with various melt index and vinyl acetate content, and their blends with polypropylene (PP). The goal of the study was to achieve a higher electrical conductivity with lower loading of carbon black as compared to those of homopolymer, PP and copolymer, EVAs.; The results of a systemic study of processability and Direct Current(DC) electrical properties on conductive carbon black filled polymers, PP and ethylene co-vinyl acetate(EVA), and PP/EVA blends are reported. The processability of mixtures of PP, EVA, and PP/EVA blends with carbon black loading ranging from 2.5% to 30% by weight were evaluated by Torque Rheometry. Polymer blends of conductive composites based on PP and EVAs were prepared from conductive composites from a 30% weight of carbon black master blend. Between 3.75% and 8.75% carbon black loading, the percolation thresholds were observed. Both the percolation threshold and applications were strongly dependent on molecular weight and viscosity that dominated the carbon black wettability.; Among three EVAs, the melt index (MI) and vinyl acetate content(VA) play a role in resistivity properties, especially the MI. The effect of mixing technique on electrical resistivity shows that when the mixing time is increased, the dispersion is more uniform based on observations of standard deviations in resistivity tests. Therefore, the twin screw extruder provided better mixing effect than the Haake Torque Rheometer.; The effect of carbon black loading on tensile properties and stiffness showed that the higher the carbon black loading level, the higher the rigidity and stiffness. Parallel plate melt rheology showed that the longer the mixing time the better the mixing.