Due to the well-defined mechanical properties and high service temperature, considerable efforts have been devoted to the development of expanded polypropylene bead foams nowadays. A pilot scale batch foaming equipment with volume of 50 L was carried out to produce polypropylene and polypropylene/poly(lactic acid) bead foams with using n-pentane as the physical blowing agent. The resultant bead foams exhibited high expansion ratio up to 44.4, nice ellipse bead foam shape, well-defined cell structure and quite high cell density. Neat PP exhibited a narrow foaming temperature window around 4—5°C. Poly(lactic acid) possessed high n-pentane solubility, and the presence of 20% poly(lactic acid) was verified to obviously broaden the foaming temperature window to 10—15°C and facilitated the foam expansion. In this study, the fundamental issues such as pressure building in autoclave, n-pentane solubility, and various parameters to control bead foams’ expansion and cell morphology are presented.
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