Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 263171
Loughborough University

Loughborough University Institutional Repository

Please use this identifier to cite or link to this item: https://dspace.lboro.ac.uk/2134/6942

Title: Stress relaxation behaviour in compression and some other mechanical properties of thermoplastic-elastomer
Authors: Gordons, Temofebi G.
Keywords: Plastics
Thermoplasrtic elastomers
Stress relaxation
Issue Date: 1990
Publisher: © Temofebi G. Gordons
Abstract: Thermoplastic elastomers have been found to have unsual properties, a consequence of composition and structure. The molecular composition comprises hard thermoplastic blocks which aggregate into domains, and flexible elastomer blocks in a linear or inter-penetrating structure. The mechanical properties such as stress relaxation, tensile strength, elongation, recovery and hardness of some thermopastic elatomers have been studied in some detail. The stress relaxation studies have been made possible with the development of the stress relaxation measuring equipment at the Institute of Polymer Technology. Highly accurate and reproducible results were obtained from the "ideal curve" measurements taken with the equipment, which permits continuous measurements of residual force and instantaneous modulus. It was noted that stress relaxation, while not only dependent on thermoplastic type and/or formulation (as expected) but also depended on the measuring technique (e.g. the strain rate, continuous loading, interrupted loading etc.) which have significant effects on subsequent stress relaxation. Temperature and environment also affect the results. The effect of thermal treatment, lubrication of surfaces and interrupted loading were investigated. An attempt was made to relate the modulus enhancement factor "MEF" to Hysteresis. An attempt was also made to relate the change in "MEF" to the continuous structural re-organization in the material and finally to stress relaxation.The commercial significance of stress relaxation and "MEF" in the performance of seals and gaskets is also explored. Some of the material supplied by industry for this project was prepared by "dynamic vulcanization". Attempt has been made using peroxide cross-linking agent to prepare EPDM/PP blends by this technique to explore structure-property relationship. As expected, the cured samples out-performed the uncured samples. Long term stress relaxation measurement (up to 10,000 hours) revealed the low premanent set and modest stress relaxation associated with thermoplastic elastomers in general.
Description: A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.
URI: https://dspace.lboro.ac.uk/2134/6942
Appears in Collections:PhD Theses (Materials)

Files associated with this item:

File SizeFormat
DX093945.pdf10.14 MBAdobe PDFView/Open


SFX Query

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.