Study of modified polypropylene for rotational moulding applications

Abstract

Polypropylene is stiffer than polyethylene, having high heat distortion temperature. It is autoclaveable, offers excellent chemical resistance, environment stress-cracking resistance and surface hardness. It is not possible to produce rotomolded article from injection moulding polypropylene grade because melt flow index (MFI) required for polypropylene rotomoulding is higher. Also, injection moulding grade PP is not suitable to prevent the material from thermo oxidative degradation during long rotomoulding cycles. The reactive extrusion is a promising technique to get higher MFI, which can be used for rotomoulding process with proper additive package. In this paper the polypropylene grade is modified for rotational moulding applications with the help of reactive extrusion. It is done in order to get higher MFI polypropylene. Sintering is observed to be related to zero shear viscosity and directly to MFI. During the experimentation it was observed that, for higher MFI material sintering completed at lower temperature. It is found that as MFI increases the flexural properties of rotomoulded specimen increases, and notched izod impact, tensile strength, and elongation at break decreases. Fine spherulites were observed for low viscosity material. SEM images revealed the coarseness with increased MFI.