Extrusion Foaming Of Pp And Its Blend With Ps And Its Nanocomposite With Nano-mmt

Polypropylene (PP) foams are widely used in the automotive and packaging industry, due to their advantages of light weight, recyclable, thermal resistance, chemical resistance, and oil resistance. The formability of PP is poor because PP is a semi-crystalline and has low melt strength and elongational viscosity, and it is difficult to get excellent foams for cell wall rupturing and coalescence. Research efforts have been made to improve the formability of PP. This work aims to improve the formability of PP by improving its melt strength. PP and polystyrene (PS) were batch foamed under low temperature conditions. PP, PP/PS blend and PP/MMT nanocomposite foams were prepared by twin screw extruder. The deeper investigation was performed on the rheological properties of materials.The PP/PS blends were batch foamed under low temperature conditions. The results showed that the formability of PP was improved by addition of PS. PS acted as storage for storing Sc-CO2 in the foaming. Cells mostly were located in PS domain or the interface between PP and PS. It was difficult to obtain uniform cell structure at low temperature.PP/PS blend and PP/MMT nanocomposite were prepared by a twin screw extruder. The high-pressure rheometer and rotational rheometer were used to measure the rheological properties. The results showed that the shear viscosity, storage modulus, melt strength, and elongational viscosity of PP were increased by addition of PS and nano-MMT.PP, PP/PS, and PP/nano-MMT foams were prepared by a twin screw extruder and foaming die. Effects of die temperature on foam morphology were investigated. The results showed that it could got good foams for pure PP at 135℃. Because of poor compatibility between PP and PS, it is difficult to obtain good foams of PP/PS at this temperature. The formability of PP was improved by the addition of nano-MMT. Nano-MMT could act as nucleation and increased the melt strength of PP. The average cell sizes of all PP/nano-MMT foams were below 145μm, and its cell density were above 1.6×105cells/cm3.The relationship among the rheological properties of materials, the cell structure and appearance of foams was built in this paper.