Study on Extrusion Foaming of Polypropylene/Polydimethylsiloxane Blends

Foaming process of PP/PDMS blends was investigated using a single extruder foaming system,with supercritical carbon dioxide as the foaming agent.Influences of die temperature and the amount of foaming agent on foam expansion ratio,cell-population density and die pressure were analyzed.Our research showed the curve of the final expansion ratio of PP foam versus temperature showed a typical mountain shape for each formulation,indicating that gas loss and crystallization stiffening of the melt at low temperature were the two governing factors of foam expansion ratio.Again,research also showed the addition of PDMS improved the expansion ratio of PP foamed samples at higher loading(5 wt% and 7 wt%)of foaming agent.For PP/PP-g-MAH/PDMS blends with the formula of 98/1/1,foamed samples with expansion ratio almost as high as 23 were obtained as 5 wt% foaming agent was used.