Microcellular Foaming Process Of Micropore Shape And Toughness

We chose AC foaming agent used widest current according to the beginning decomposition temperature and its scope , the volume of gas, velocity of decomposition, mechanical properties etc. factors of the different type chemical foaming agents. Its dispersion in polymer matrix was not well, so we studied the foaming aid-activator for the sake of depressing the beginning decomposition temperature of AC foaming agent and improving its dispersion in PP.We discussed the process of AC foaming agent's expansion and cell's growth within PP. The formation of cell structure within PP set three stages: nucleation, expanding, solidifying and shaping . During the process of expanding to solidifying, the gas-fluid system that consisted of the expanded cells and fused PP was unstable, the cell may expand until the final shape or take place the phenomenon of coalescence (conglomeration) and breach and gas escaping.The mechanical properties of microcellular foam materials were tested and analyzed in this paper. The results showed that the strength of notched impact was increased obviously, the tensile strength was reduced a little, the bending strength changed unconspicuously. In order to analyze the cause that strength of notched impact was improved, we studied PP modified of elastic and the hollow glass microsphere respectively , then compared them with microcellular foam materials. There were two main factors that affected the strength of notched impact, one was the microcells changed the crazing's expanding direction, controlled the development of crazing and terminated it in time not went so far as to multiple crackle. The generation and development of lots of crazing and shear zone needed to consume plenty of energy; the other was that the deformation of the microcells and the matrix around them can absorb much energy also.