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Title: The effects of contamination upon mechanical properties and re-processing stability of recycled poly(vinyl chloride)
Author: Maund, B.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1997
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Recycled Polyvinyl Chloride derived from post-consumer bottle products has been investigated to find the effects of contamination upon mechanical and re-processing properties. Aspects of recycling technology, structure-property relationships of PVC and the materials reaction to thermal degradation are also reviewed in dissertation form. Tensile, fatigue and environmental stress cracking properties of two recycled PVC materials (of a pulverised and flake raw form), from different stages of the recycling process, were tested in relation to those of two group PVC bottle materials. Generally, mechanical results displayed an inferiority of the recycled materials compared to the performance of the purer grades, although the pulverised recycled grade (RP) did not show a large drop. Scanning electron microscopy (SEM) of fracture surfaces from tensile and fatigue specimens, revealed that recyclate materials were pervaded with impure particles that served to interfere with stress transfer mechanics and altered their yielding characteristics. Molecular weight analysis (Gel Permeation Chromatography, GPC), of the all four materials tested, showed the molecular weight of the recycled materials was not significantly affected by the recycling process used. Separation of impurities by selective dissolution of the PVC matrix showed a contamination of 0.31%wt insolubles. Infrared analyses of solution cast films and insolubles were then performed, revealing a definite presence of polyethylene Terephthalate (PET) with polystyrene and polyethylene present in minor proportions. Batches of the two recyclates and a bottle flake (BF) material were subjected to simulated multiple recycling using a torque rheometer. Molecular weight and Infrared analyses were performed to assess the amount of degradation occurring during re-processing. Results from both analysis techniques were in agreement with a rapid degradation of the two recycled grades when compared with the BF material. Further multiple recycling was then performed on BF mixed with a small proportion of polyethylene which showed that this contamination accelerated degradation processes. Re-processing of BF material with additions of new material at each recycled pass indicated the existence of a threshold proportion of new material that provided a surrogate stability to the melt.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available