Chaolu Yin

Effect of Processing Method on Morphological and Rheological Properties of PC/CaCO3 Nanocomposites

The focus of this work is to investigate the effect of different manufacturing methods on nanoparticles dispersion and rheological properties of polycarbonate (PC) filled nano-calcium carbonate (CaCO3) nanocomposites. Two methods were used to prepare the PC/CaCO3 nanocomposites through twin-screw extruder: one was compounding PC with CaCO3 nano-powder, named PC-CP; another was compounding PC with CaCO3 aqueous suspension, named PC-CAS. The relationship between the processing method and the particle dispersion, matrix molecular weight and rheological properties of the nanocomposite was discussed. Morphological observation showed that nanoparticles were dispersed more homogeneously in PC-CAS. Gel permeation chromatography (GPC) test showed that molecular weight drop of PC-CAS was smaller than PC-CP when CaCO3 content under 2.2 wt%. Melt flow rate (MFR) and capillary rheological behavior indicated the change of rheological property of PC-CP was larger than PC-CAS while CaCO3 content under 2.6 wt%. In general, both the dispersion and rheological property of PC-CAS were better than PC-CP under a reasonable CaCO3 content.

Study of the morphology and temperature-resistivity effect of injection-molded iPP/HDPE/CB composites

The relationship between morphology and temperature-resistivity effect of injection-molded isotactic polypropylene/high density polyethylene/carbon black (iPP/HDPE/CB) composites with special orientation structure is investigated in detail. The morphological variation induced by melting, disorientation, crystallization and movement of CB particles is responsible for the change of electrical conductivity of the iPP/HDPE/CB composites during the heating and cooling. The room temperature volume resistivity of the composites reduces markedly after a round of heating and cooling because the network is improved through morphological changes and movement of particles during annealing. The continuity of HDPE/CB phase and the effective concentration of the CB particles in HDPE simultaneously determine the temperature-resistivity effects of the composites. Samples with iPP/HDPE mass ratio of 50/50 achieve a better balance of the two factors, which results in more stable conductive properties varying with temperature.

Isothermal-Treatment-Induced Network Formation of Carbon Black in Isotactic Polypropylene/Carbon Black Composites

The effect of isothermal treatment on network formation of nanoscale dispersed carbon black (CB) particles in mild-compounded isotactic polypropylene (iPP)/CB composite is investigated. Network formation of CB took place in a quiescent melt without any flow and expansion since the isothermal treatment of the composite was carried out under high pressure conditions. TEM was used to inspect the network formation of the well-dispersed CB. Resistivity temperature and dynamic rheological behaviors of samples before and after isothermal treatment were examined to investigate the relationship between fillers’ network formation and electrical conductivity enhancement.

Effect of the Extrusion Process on the Morphology and Electrical Conductivity of Injection-Moulded Polypropylene/HDPE/Carbon Black Composites

In this work, isotactic polypropylene (iPP)/high density polyethylene (HDPE) composites filled with carbon black (CB) were prepared by the mild compounding method and the common melt-mixing method. The selective distribution of CB particles in the immiscible iPP/PE blends was determined by the interfacial tensions, but the morphologies of the polyblends strongly depended on the compounding method. The mild compounding method strongly affected PE phases to form triple phase morphology in the composites, which inhibited effective conductivity network formation in the low CB content range. A skin-core structure of the iPP/HDPE/CB composite, prepared by the common melt-mixing process, was present when an effective conductivity network was obtained, and a co-continuous structure of the iPP/HDPE matrix is not necessary.