Extrusion Processing of Ultra-High Molecular Weight Polyethylene

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) is a unique thermoplastic polymer with excellent performances. It has ultra-high molecular weight and extreme rheological behaviour, which make it a worldwide challenge to process UHMWPE continuously with little or without processing aids. Although the polymer processing technology has been increasingly maturated, it still cannot carry out the industrialized production efficiency by conventional processing methods and apparatus at present. In this chapter, we review the progress of extrusion processing technology for UHMWPE, including ram extrusion, single screw extrusion, twin screw extrusion and novel extrusion technology based on extensional rheology. By summarizing of these processing technologies, a basic framework of the processing principles and methods for UHMWPE is clearly presented. It is helpful for us to understand the processing characteristics and methods for such thermoplastic polymer with ultra-high molecular weight.

União de Termoplásticos Pelo Processo Friction Stir Welding: Influência da Ferramenta e Parâmetros do Processo

“…Assim, pode-se dizer que a FSW de materiais poliméricos não ocorre no estado sólido, e sim no estado "borrachoso". Um caso à parte é o do polietileno de ultra alto peso molecular (PEUAPM), que dado sua alta massa molar, acima de 1.500.000g/mol, mesmo em temperaturas acima da fusão, tem índice de fluidez próximo a zero [31].…”

Melt- vs. Non-Melt Blending of Complexly Processable Ultra-High Molecular Weight Polyethylene/Cellulose Nanofiber Bionanocomposite

“…Viscous flow state of melt UHMWPE is not attainable even with increases in temperature, and it maintains in non-uniform or non-continuous rubberlike state. This is attributed by its higher theoretical viscous flow temperature as compared to its decomposition temperature [ 35 ], as a result of numerous chain entanglements contributed by its extremely high molecular weight. In fact, its melt viscosity could be up to 1 × 10 8 Pa.s which is about 2500 times higher than high density polyethylene (HDPE) [ 36 ].…”

Less Entangled Ultrahigh-Molecular-Weight Polyethylene Produced by Nano-Dispersed Ziegler–Natta Catalyst

“…Owing to an extremely high molecular weight and a strong intermolecular interaction, UHMWPE melt has no viscous flow state. Above its low critical shear rate, the UHMWPE melt undergoes melt fracture in screw extrusion or conventional melt-mixing, while the low mobility of molecular chains restricts re-formation of the continuous melt block . Consequently, bulk products are typically fabricated by compression molding or ram extrusion of reactor powder regardless of their low processing efficiency.…”

“…Above its low critical shear rate, the UHMWPE melt undergoes melt fracture in screw extrusion or conventional melt-mixing, while the low mobility of molecular chains restricts re-formation of the continuous melt block. 6 Consequently, bulk products are typically fabricated by compression molding or ram extrusion of reactor powder regardless of their low processing efficiency. In the forming process, the motion of highly entangled polymer chains is very slow.…”