Premium
Biaxial orientation of polypropylene by hydrostatic solid state extrusion. Part II: Morphology and properties
Author(s) -
Pan S. J.,
Tang H. I.,
Hiltner A.,
Baer E.
Publication year - 1987
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.760271202
Subject(s) - materials science , lamellar structure , necking , extrusion , composite material , ultimate tensile strength , breakup , polypropylene , recrystallization (geology) , deformation (meteorology) , mechanics , physics , biology , paleontology
Changes in the lamellar structure of polypropylene during biaxial orientation by hydrostatic extrusion have been examined. Examination of etched surfaces in the transmission electron microscope has revealed that up to a draw ratio of about 1.5 × 1.5 the primary mechanism is lamellar rotation into the plane of orientation, At higher draw ratios breakup of the lamellae is observed with formation of a granular structure. Thermal measurements suggest that localized melting and recrystallization may accompany the process of lamellar breakup. These morphological observations confirm the previous interpretation of SAXS and permit a more detailed model of the hierarchical structure to be proposed. Stress strain measurements show a gradual change from sharp necking to uniform deformation as the draw ratio is increased. On the other hand, the structural change at a draw ratio of about 1.5 × 1.5 Is accompanied by a large increase in the tensile impact strength.