Hydrostatic extrusion of solid polymers

Hydrostatic extrusion of a high density polyethylene rod was carried out. Both the process of plastic deformation during hydrostatic extrusion and the changes of properties of the polyethylene with extrusion were studied. Particular attention was paid to the process of molecular orientation and the destruction of the original lamellae. To obtain a better understanding of the deformation process, the lateral dimension of crystallite and the long period were obtained from the X-ray diffraction data. Furthermore, the influence of extrusion conditions on the structure and properties of the extrudate were investigated. The Vickers hardness number and thermal shrinkage of the extrudates were affected considerably by the extrusion conditions, i.e. extrusion temperature and extrusion ratio. In order to determine the relationship between the properties and extrusion conditions, it is necessary to consider not only the molecular orientation but also the crystallinity, fibrosity and the fine-structure of the extrudates.