Role of Processing Aids in the Extrusion of Molten Polymers
Role of Processing Aids in the Extrusion of Molten Polymers
- Journal of Vinyl & Additive Tecnology, 8, p.7-24, 2002 .
Froduct quality and, in general, processing windows and rates of production in the extrusion of molten polymm are limited by various flow instabilities (mainly melt fi-acture)that are observed at high production rates. While there still are unresolved issues in comprehending these phenomena, industry demands for process optimization dictate the employment of processing aids (PAS)for product quality improvement and energy requirement reduction. In this review paper, most commercially used processing aids (PAS)are discussed, namely, fluoroelastomers. tearates, small amounts of polymers blended with the process polymer, and the newly discovered boron nitxide as pure and in combination with other fluoroelastomers. This paper focuses on the appropriate and optimum usage of the various PAS as well as on the mechanism that underlies their action for flow enhancement and instability elimination. Finally, numerous experimental observations are discussed, and several examples are illustrated.
Froduct quality and, in general, processing windows and rates of production in the extrusion of molten polymm are limited by various flow instabilities (mainly melt fi-acture)that are observed at high production rates. While there still are unresolved issues in comprehending these phenomena, industry demands for process optimization dictate the employment of processing aids (PAS)for product quality improvement and energy requirement reduction. In this review paper, most commercially used processing aids (PAS)are discussed, namely, fluoroelastomers. tearates, small amounts of polymers blended with the process polymer, and the newly discovered boron nitxide as pure and in combination with other fluoroelastomers. This paper focuses on the appropriate and optimum usage of the various PAS as well as on the mechanism that underlies their action for flow enhancement and instability elimination. Finally, numerous experimental observations are discussed, and several examples are illustrated.