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Title: Structure-property relationships in biaxially stretched amorphous PET applicable to thermoforming and stretch blow moulding
Author: Mohamed, Raja Roslan Raja
ISNI:       0000 0004 6499 9407
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2017
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In thermoforming and Injection stretch blow moulding, amorphous Polyethylene terephthalate (aPET) is stretched to form products. While stretching, the microstructures change and have influence on final product properties. Therefore, the main aim of this work was to provide a fundamental understanding of microstructures evolvement during biaxial stretching of aPET in conditions applicable to thermoforming and injection stretch blow moulding as well as their effect on thermal and mechanical properties. Specimens were cut out from a commercial grade extruded aPET sheets which has a similar intrinsic viscosity to injection stretch blow moulding (ISBM) aPET and stretched using Queen's Biaxial Stretching machine under various sets of parameters namely temperature, strain rate, stretch ratio and mode of stretching, whilst mimicking the industrial processing conditions. The stress-strain behaviour during stretching was then analysed. The stretched specimens were then characterised employing a Fourier Transform Infrared with Attenuated Total Reflectance (FTIR-ATR) for gauche and trans conformers, a Differential Scanning Calorimeter for heat-crystallisable content, crystallinity and thermal properties, FTIR-ATR with polariser for orientation parameters, and a tensometer for mechanical properties. Statistical tools were also employed to determine the significance of changes and correlate the structural changes as well as the thermal and mechanical properties. The onset of strain hardening that impedes viscous flow during stretching can be attributed to the intermolecular attractions between the aligning and orientating chain. This is a new perspective on what may cause strain hardening. The structural changes may have good linear correlation between each other, depending on the stretching parameters employed. The heat-crystallisable region was found to be the determining factor in strain induced crystallisation as well as the stretching parameters. The relationship between the properties, thermal and mechanical, is determined by complex interactions between the measured structural characteristics.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available