Show simple item record

Dynamic Mechanical Properties of Oriented Polymers.

dc.contributor.authorHsiao, Cheng
dc.date.accessioned2020-09-09T01:52:12Z
dc.date.available2020-09-09T01:52:12Z
dc.date.issued1985
dc.identifier.urihttps://hdl.handle.net/2027.42/160537
dc.description.abstractThe effects of processing conditions and gamma-ray irradiation on the morphology, melting behavior, and dynamic mechanical properties of oriented linear polyethylene and other semicrystalline polymers were studied. Three different processing methods, including solid-state extrusion (by Capillary Rheometer), shear-crystallization (by Couette Rheometer), and cold drawing (by Instron Tensile Machine) were used to prepare oriented samples. The dynamic mechanical studies of solid state extruded polymers revealed that the a relaxation (which includes two mechanisms: grain boundary movement at low temperatures and intracrystal shear movement at high temperatures) is sensitive to the extrusion temperature while the effect of extrusion rate is negligible. In the case of shear-crystallized linear polyethylene, both shear rate and shear temperature play an important role in determining thermal stability, stiffness, and crystal relaxation in sheared samples. We found that SIC (strain-induced crystallization) crystals can exist in samples held at shear temperature (135(DEGREES)C) for 30 minutes. In the gamma-ray irradiation study, we found that irradiated cold-drawn linear polyethylene shows double melting peaks and dramatic changes in anisotropy of intracrystal shear movement. These phenomena are much less pronounced in annealed cold-drawn samples, and have not been found in the solid-state extruded, and shear-crystallized samples. The present model suggests that in cold-drawn samples, the combination of nematic-like crystal structure and gamma-ray induced crosslinks results in an internal stress which concentrates around the polyethylene crystals. This internal stress causes the crystal to exp and at high temperature, explaining the observed phenomena.
dc.format.extent202 p.
dc.languageEnglish
dc.titleDynamic Mechanical Properties of Oriented Polymers.
dc.typeThesis
dc.description.thesisdegreenamePhDen_US
dc.description.thesisdegreedisciplinePlastics
dc.description.thesisdegreegrantorUniversity of Michigan
dc.subject.hlbtoplevelScience
dc.contributor.affiliationumcampusAnn Arbor
dc.description.bitstreamurlhttp://deepblue.lib.umich.edu/bitstream/2027.42/160537/1/8512433.pdfen_US
dc.owningcollnameDissertations and Theses (Ph.D. and Master's)


Files in this item

Show simple item record

Remediation of Harmful Language

The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.

Accessibility

If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.