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Hydrostatic extrusion of polypropylene and properties of extrudates
Author(s) -
Yoon H. N.,
Pae K. D.,
Sauer J. A.
Publication year - 1976
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760160808
Subject(s) - extrusion , materials science , die swell , polypropylene , composite material , hydrostatic pressure , differential scanning calorimetry , ultimate tensile strength , yield (engineering) , thermodynamics , physics
The solid‐state extrusion of polypropylene by hydrostatic pressure has been investigated at four different temperatures: 25, 50, 75, and 100°C. The pressure to effect extrusion was found to be essentially a linear function of the extrusion ratio at each temperature, while the magnitude of the extrusion pressure, for any given extrusion ratio, decreased appreciably with increasing temperature. With increase in extrusion‐ratio, the polypropylene extrudates became increasingly transparent. After passing through the extrusion dies; the Sample showed some elastic recovery. The amount of this recovery decreased with increasing extrusion ratio, X‐Ray diffraction measurements taken before and after extrusion showed reduction in sharpness of the crystalline Peaks. Differential, scanning calorimetric measurements, on the other hand, indicate that the relative heat of fusion of the extrudates increases with the extrusion ratio at each extrusion temperature. It also increases with extrusion temperature for a given ratio. Tensile stress‐strain tests were made at various hydrostatic pressure levels on the extrudates obtained at 25°C and the extrusion ratio of 2.8. Unlike on the virgin sample of polypropylene, ho yield maximum was observed on the extrudate sample at all pressures investigated. However, the effects of pressure on the relative increase in the yield stress‐and the modulus of the extrudate are comparable to those of original, unoriented samples.