No abstract

Bio-composites consisting of poly(butylene adipate-co-terephthalate) (PBAT), poly(propylene carbonate) (PPC) and epoxy chain extender ADR 4468 were fabricated via melt blending using a torque rheometer. The relationship of the torque, melt viscosity, and molecular weight of the bio-composites was established via polymeric liquid theory to estimate the real-time chain extension reaction rate under different ADR contents. At the meantime, rheological behavior, thermal and mechanical properties, morphologies, gas barrier properties of the PBAT/PPC/ADR bio-composites were systematically characterized. The corresponding results revealed that the water vapor transmission rate (WVTR) reduced by 50% under 30 phr (parts per hundreds of resin) PPC content. The addition of ADR is beneficial to improve the mechanical properties, thermal stability and phase dispersion of PBAT/PPC without affecting the water barrier property. With 3 phr ADR, the tensile stress and elongation at break were increased from 19.5 MPa and 1184% to 26.9 MPa and 1443%, respectively. In addition, the data of the torque rheometer revealed that the chain extension reaction rate and the melt viscosity was increased with the increasing ADR content, but the reaction rate was reduced with the excessive viscosity.

In this study, epoxy molding compounds (EMCs) with aluminosilicate (AlS) and aluminum oxide (AlO) were fabricated as fillers by a twin-screw-extruder (TSE) and shaped to plate samples using injection molding. AlS and AlO, electrical insulating mineral materials, were used as fillers to improve the thermal conductivity (λ c ) of composites. Composites with different filler particle sizes, filler contents and filler geometry were fabricated and the influence of these variables on the λ c was studied. The λ c of composites was measured with the hot-disk method. The distribution of fillers in composites was observed using scanning electron microscopy (SEM). Using the Lewis-Nielsen equation, experimental values of λ c were compared with those predicted. The predicted results fit the experimental values well. The result showed that λ c increases significantly when the filler content of composites is approximately over 50 vol %.

The work presented herein focuses on simulating the compounding process via a torque rheometer, as well as the relationship between the melt viscosity and the polymer molecular weight (MW). We aim to predict the plasticization of polylactic acid (PLA) using polypropylene glycol (PPG) with different MWs. The rheological properties of the PLA/PPG composites containing PPG with different MWs were systematically studied by capillary rheometry and torque rheometry. The initial degradation of PLA/PPG composites during melt processing was monitored in real time. The results indicate that PPG can significantly reduce the melt viscosity of PLA/PPG composites, leading to obvious pseudoplastic fluid behavior. The lower the MW of PPG, the lower the viscosity of the PLA/PPG composite. The addition of PPG was favorable for the degradation of PLA during processing, and the degradation degree of the composite materials increased as the MW of PPG was decreased.

In this research, the influences of filler content and filler particle size on the flow-hardening behavior were investigated by a measuring mixer. In order to more reliably assess the observed rheological behavior, isothermal differential scanning calorimetry (DSC) measurements were employed to study the curing kinetics of the compounds. The measured data can be fitted well with Kamal-Sourour’s model modified by the diffusion correlation according to Chern and Poehlein. After that, the influence of filler content and size on the kinetic parameters are presented discussed. The results show that the ultimate glass transition temperature is significantly lower for pure epoxy resin (EP) than for compounds filled with surface-treated glass beads, which have an essential effect on the diffusion-controlled reaction at different curing temperatures. For the surface-treated glass beads used in this study, the reaction speed in the early curing stage is accelerated by increasing filler content or decreasing of filler size. In the later curing stage, the reaction speeds of compounds with higher filler content or smaller fillers reduce more quickly. The study of reaction kinetics indicates that the activation energy Ea1, Ea2, the reaction order m, and n are affected differently by varying filler content and size.