School of Engineering and Materials Science
Research Student Awards
PhD Thesis: Tensile deformation of methacrylate-butadiene-styrene modified poly(vinyl chloride).
Author: LEE, M K
Supervisor(s): Peter Reed
The mechanical behaviours of the methacrylate-butadiene-styrene (MBS) modified poly(vinyl chloride) (PVC) system are studied over a wide range of extension rate and temperature. Rubber modified PVC is used in the blow moulding industry for bottle manufacture to improve impact resistance. The study considers the tensile behaviour of PVC modified with varying amounts of MBS modifier (0%-16% by weight). Tensile testing is performed at extension rates between 0.006% /s to 12000% /s, the latter is corresponding to typical rates sustained on impact, and over a temperature range of -10oC to 70oC.
Different modes of deformation, including shear yielding, crazing and voiding, are found to occur in the rubber modified materials, depending on the test conditions and amount of modifier added. The types of deformation, coupled to electron microscopy studies to elucidate the associated deformation mechanisms, are characterised for the ranges of modifier, temperature and extension rate studied.
Ductile behaviour is found to occur throughout the studies under uniaxial tensile stress using standard tensile specimens. A particular experimental study is made of the variation in yield stress which is then compared with trends predicted by several theoretical models.
Studies are made of the necking profiles associated with yield in these materials which changes with deformation rate and temperature. Theoretical predictions of the necking process previously reported in the literature are found to be unsatisfactory for high rate deformation. Hart's theory of tensile instability is found to be more appropriate at faster deformation rates. An extension of this theory is used to model the observed behaviour.
Inter-relationship between micro-deformation processes and mechanical behaviour are considered.