Melt transformation coextrusion of polyethylene and polybutylene measurements of streamline flow and pressure effect on birefringence and interface visualization in the MTCE process
In this investigation of melt transformation coextrusion of polyethylene and polybutylene, two single screw extruders were used, one processing the core polymer, polyethylene, the other, the shell polymer, polybutylene. The main purpose of this investigation using a new streamlined die with glass windows was to measure streamline flow in the converging section of the die, to visualize interface features in the coextrusion process and to characterize the die pressure effect on the orientation of the melt molecules by measuring birefringence and extrudates' thermal and mechanical properties. The results of the study under different conditions ( die pressure and die temperature) showed that streamline flow was reached using this die. A quite steady and clear interface was observed, and pressure had considerable effect on birefringence and further on the extrudates' final thermal and mechanical properties. The samples produced by the coextrusion process exhibited a melting point elevation by about 5 degree celsius at die pressure 5000 psi. When the same core polymer was extruded (single layer extrusion) alone, it had a melting point 1 degree celsius lower than that of coextrusion process at the same die pressure. It was also noted that the coextrudates' yield strength was slightly higher than that of single layer extrudates'.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:melt transformation coextrusion polyethylene polybutylene measurements streamline flow birefringence mtce process
Date of Publication:01/01/1989