Thermoplastic silicone elastomer lubricant in extrusion of polypropylene wood flour composites

Abstract A possibility of using a thermoplastic silicone elastomer (TPSE) for reduction of surface defects in the extrusion of wood‐filled metallocene polypropylene (mPP) has been investigated in this work. A capillary rheometer and a single‐screw extruder have been utilized to study the effect of the additive on the extrudate distortions. Maleated syndiotactic metallocene polypropylene was also used as an adhesion promoter in mPP/wood flour composites. At loadings of 50 wt% wood flour in the mPP, the extrudates come out of the die with significant tearing and surface roughness. The surface rupture mechanism is similar to that of sharkskin in neat polymers; however, the defect is much more exaggerated in the case of wood fiber‐filled composites. It was found that TPSE at low concentrations (1 wt%) was able to reduce or even completely eliminate extrudate surface tearing. Increasing the extrusion speed yielded better results. Addition of a coupling agent also provides improvement in the extrudate appearance. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:100–108, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/adv.20090