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In this study, poly(vinyl chloride) (PVC) and silica (SiO 2 ) microcomposites and nanocomposites were prepared by melt mixing in a Haake torque rheometer. The fusion and rheological behaviors of PVC/SiO 2 composites were evaluated by means of torque data recorded during processing to investigate the influence of the SiO 2 particle size on these behaviors. It was found that the fusion time and the fusion temperature decreased with the decreasing of SiO 2 particle size, whereas the fusion torque increased with the decreasing of particle size. The PVC/Si-25-nm nanocomposite (PVC including the 25 nm of SiO 2 ) showed the highest apparent viscosity among the PVC/SiO 2 microcomposites and nanocomposites prepared in this study. Scanning electron microscopy results demonstrated that some aggregates, whose sizes about 60-90 nm, were formed when the 25 nm of SiO 2 was used as filler. POLYM. ENG. SCI., 51:1574-

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The compaction process involves stress transmission via rigid or flexible (die) walls and the propagation of stresses within a powder mass. The particles that comprise the powder distribute the stress by a variety of kinematic processes that involve sliding, rotation, particle deformation, and rupture. In practice the “particles” are often agglomerates of finer particles that have a range of properties. All of these factors must be considered in developing a comprehensive predictive model for compaction.The modeling of powder-compaction processes has a significant history that has been greatly advanced by the relatively recent general availability of powerful computers and their peripherals as well as by appropriate softwares. Compaction modeling may attempt to provide a basis for machine-loading specifications, or it may provide guidelines to help minimize “capping” defects where failure cracks form at the top of the green compact. It may also provide “green-body heterogeneity” through predicted stress and density distributions within a compact. Likewise compaction models may be combined with binder burnout and sintering models to predict internal microstructural features such as grain size and porosity, and the external shape of the sintered product. This article will deal only with the modeling of the compaction process; important elements such as powder flow for die filling and subsequent processing steps such as sintering and net shape predictions are not directly addressed.

In clinical use, wetting the repair surfaces may result in stronger repairs. The use of bonding agent in VLC resin repairs in combination with wetting agent results in improved flexural properties.