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STRUCTURE-PROPERTY STUDIES IN THE DEFORMATION OF SEMI-CRYSTALLINE POLYMERS (CHAIN-EXTENDED POLYETHYLENE, NYLON, GEL, IODINE COMPLEX)
Abstract
Drawing behavior of a high pressure crystallized chain-extended polyethylene in solid-state extrusion was studied. Because of the reduced trapped entanglements at the fold surfaces and interlamellar links in this morphology, there was insufficient continuity to provide stress transfer for effective orientation. Draw efficiency increases to a maximum of 0.71 when the polyethylene was crystallized at higher undercoolings. Tensile moduli were found to be a unique linear function of molecular draw ratio, measured by thermal shrinkage, independent of the initial morphology, draw temperatures and techniques. Electron microscopy of the fracture surface replicas at low draw showed the coexistence of undeformed, tilted, partially drawn lamellae and the generated fibrillar structure. The observations were consistent with Peterlin's model of plastic deformation. The question of melting and recrystallization during deformation was studied by small-angle X-ray scattering of the drawn chain-extended polyethylene. The results showed that melting and recrystallization did not occur for this morphology. A partially dried Nylon 6 gel in benzyl alcohol was solid-state co-extruded at 150(DEGREES)C up to draw ratio 5.7. Double orientation was observed in this uniaxial drawing with the crystal chain axis oriented parallel and perpendicular to the draw direction. A deformation mechanism was proposed from the studies of birefringence, wide- and small-angle X-ray scatterrings. A new drawing technique for Nylon 6 by reversible plasticization with iodine was proposed. A complex was obtained by imbibing a Nylon 6 film in a KI(,3) solution. It was drawn up to 790% elongation at 55(DEGREES)C and iodine was removed by titration with sodium thiosulfate to generate back a drawn Nylon 6 of controlled crystal form. The complex has a stoichiometry of (Nylon 6)(I(,3)('-))(,0.24)(I(,2))(,0.35). X-ray studies showed that interchain hydrogen bonds in both the crystal and amorphous regions were interrupted. The drawn complex has a new monoclinic crystal structure with iodine intercalated between the hydrogen bond sheets.
Subject Area
Polymers
Recommended Citation
CHUAH, HOE HIN, "STRUCTURE-PROPERTY STUDIES IN THE DEFORMATION OF SEMI-CRYSTALLINE POLYMERS (CHAIN-EXTENDED POLYETHYLENE, NYLON, GEL, IODINE COMPLEX)" (1985). Doctoral Dissertations Available from Proquest. AAI8517089.
https://scholarworks.umass.edu/dissertations/AAI8517089