The following study forms part of a programme of work designed
to produce a commercial moulding material based upon Polyethylene
terephthalate. The work described relates specifically to the
investigation of the impact characteristics of PET, and improvements
that may be obtained in the impact strength by incorporation of
the rubbery phase into the glassy PET matrix. The two phase
systems studied in greatest detail were PET/Ionomer (Surlyn A)
blends. A grafting reaction that was found to occur in the
melt between these two polymers has been investigated in some
detail using a Weissenberg Rheogoniometer.
Also reported are studies of the crazing properties and nature
of the craze structures produced in amorphous PET, together with
a study of the crack velocity profiles obtained during the high
velocity impact fracture of PET mouldings. This latter work led
to a correlation of the topographical features observed on the
fracture surface with the crack velocity. As a result a stick-slip
mechanism of crack propagation was proposed, involving craze formation and fracture.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.