Study Of Polypropylene Microcellular Foam

In this paper,with dynamic rheometer and capillary rheometer,effect of EPDM and cross-linking on the PP melt were studied;with DSC,decomposition characteristics of heat balance blowing agent(BBA),effect of cross-linking,EPDM and talc on the crystallization were studied;with polarizing microscope, metallographic microscope and SEM,crystallization properties of PP and cellular structure in foamed material were characterizated.(1) Cross-linking increases the melt strength,promotes crystallization,reduces the grain size.an cellular foam with cell density of 9.1×10~5cells/cm~3 and cell size of about 145μm was prepared with cross-liked PP.(2) While the gas/polymer melt experence the state of thermodynamic instability,free volume in EPDM/PP interface acts as nuclate.The impact of EPDM on foaming is related to Mooney viscosity,lower Mooney viscosity can more effectively promote nucleation,and melt strength of EPDM/PP blends,decrease mergering of the bubble.(3) While decompositing,heat balanced blowing agent(BBA) release little heat,but releases gas gently.An cellular foam preparated with BBA as a blowing agent is of even cellular morphology,high cell density and high impact strength.(4) Surface properties of the talc take greatly effect on the nucleation.Talc treated by methyl trimethoxysilane shows the best nucleating capabilities,the microcellular foam made by using that talc as a nuleating agent is of bubble with diameter in 2.8μm and density of 6.25×10~9 cells/cm~3.