PP PE BLENDS BY REACTIVE EXTRUSION - PP RHEOLOGICAL BEHAVIOR CHANGES/

The aim of this work was to obtain a polypropylene (PP) with strain ha rdening in elongational flow by a reactive extrusion process. This rhe ological behavior imposes a structural modification of the PP: linear chain to long side branches. Reactive extrusion allows the modificatio n of PP by radical chemistry, but this modification is accompanied by significant degradation of chains: beta-scission. A polyfunctional mon omer (TMPTA) associated with addition of polyethylene (PE) allows us t o limit this degradation and to build a connected structure. Gel perme ation chromatography measurements confirm the presence of high-molecul ar-weight species. With thermal analysis of modified polymers, we show the creation of copolymer PP/PE at the interface of the PE inclusions . Under these conditions, all the reactive blends present strain harde ning. The elongational viscosity of all blends can be described by the Leonov model calculated with viscoelastic data. This model gives a go od description of the viscosity without adjusted parameters. (C) 1997 John Wiley & Sons, Inc.