Study On The Preparation Process Of The Rigid Low-Foamed Surface Crusting PVC

The rigid low-foamed surface crusting PVC (polyvinyl chloride), reputed as composite wood, was developping speedly in the world meterials market in the last few years. There are some basic chemicophysics problems about the foaming extrusion processing to be studied and clarified. The relationship between the formula, the processing condition, the apparatus parameter setting and the density, the physicomechanical properties, rheological property, were researched in detail in this artical, according to the extrusion process of PVC in the rheometer.The influence of formula on the properties of low-foamed PVC product was studied and the optimal formula of processing low-foamed PVC was determined, by differential scanning calorimeter (DSC) and scanning electron microscope (SEM). The results shown that the using of compound foaming agent AC/NaHCO3 could reduce heat release, which was benefited to the plasticizing of PVC resin and the forming of homogeneous structure cell. The density of low-foamed PVC product decreased with the foaming agent usage increasing, and when its usage was over 0.8 phr the PVC product density could decreased, so the suitable usage of the foaming agent was 0.6~0.8 phr. The density and tensile strength of low-foamed PVC product decreased and the cell structure become homogeneous with ZB530 usage increasing, and the suitable usage of ZB530 was about 0.8 phr. The addition of a small amount calcium carbonate could promote the fusion and plastication of PVC resin. The density of low-foamed PVC product decreased at first and then increased with the screw rotation rate increasing. When the screw rotation rate was too high, the fusion and plastication of PVC resin could be nonuniformity and some gas escaped, which made the product density increased. The viscosity of PVC resin flux was low and prone to flowing, which was benefited to the gas expansion and small density product was obtained. At last, the best apparatus...