Rheological properties of polypropylene during multiple extrusion

• Published in: Polymer testing Vol. 24; no. 1; pp. 86 - 93
• Main Authors: da Costa, Helson M., Ramos, Valéria D., Rocha, Marisa C.G.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2005; Elsevier
• Subjects: Applied sciences; Degradation; Exact sciences and technology; Extrusion moulding; Machinery and processing; Moulding; Plastics; Polymer industry, paints, wood; Polypropylene; Rheological properties; Statistical experimental design; Technology of polymers; Degradation; Polypropylene; Statistical experimental design; Rheological properties; Viscosity; Propylene polymer; Temperature effect; Processability; Experimental study; Melt index; Property processing relationship; Extrusion molding; Investigation method; Mechanical degradation; Olefin polymer; Recycling; Thermal degradation
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2004.06.006

Polypropylene (PP) degradation during multiple extrusion at different temperatures was studied by following changes in rheological properties. Dynamic and transient experiments were carried out in a rheometer with parallel plate geometry. In addition, a statistical experimental design (2 2, with replicates) was employed using die zone temperature ( X 1) and number of extrusion cycles ( X 2) varying at two levels. The system degradation was modeled using melt flow index (MFI) as a control variable. A rapid increase of chain scissions of the PP macromolecules and, consequently, a molecular weight reduction, was observed through abrupt increase of MFI and reduction of properties such as complex viscosity ( η*) and elasticity of the molten polymer.