Frictional Behavior of Polyethylenes with Respect to Density and Melting Characteristics

Abstract

The frictional behavior of a polymer on a metal surface is an important material characteristic relevant to processing and product usage. In particular, the frictional behavior is the key factor in the solid conveying along extruder screws near the hopper until the feed material starts to melt. Thos chapter focuses on the frictional behavior of 12 polyethylene samples with densities ranging from 0.963 down to 0.870 g/cc on a metal surface was studied. The samples with densities higher than 0.908 g/cc behaved as rigid plastics, sliding on the metal surface. The samples with densities lower than 0.905 g/cc behaved as elastomers, strongly adhering on the metal surface and tearing within the polymer. Melting occurred when the metal was heated to a temperature above the melting range of the sample. The frictional behavior of a polyethylene can be understood in terms of the density and melting temperature range of the sample. The density and melting characteristics of a PE are controlled by the composition and molecular structure. A PE with a higher density has a higher crystalline and rigidity with a melting peak at a higher temperature. The frictional behavior of a PE can be understood by the density and melting characteristics. PEs with a density above about 0.908 glee behave as rigid polymers and exhibit the sliding mechanism, developing lower frictional stresses.