Abstract
The processing behaviour of poly(ethylene terephthalate) (PET) films containing incompatible polymeric particles has been analysed, with particular reference to the relationship between the particle-matrix interfacial energy and the microvoids that are formed when the composite film is stretched at 90°C. A model was developed to simulate void formation due to interfacial delamination between PET and three types of dispersed incompatible polymer: poly(4-methyl pent-1-ene) (TPX); polypropylene (PP); and polystyrene (PS). Numerical results obtained using the finite element method were compared with experimental data on blends with different particle sizes,for both the internal and sub-surface regions. Experimental measurements showed that increasing the difference in surface energy between PET and the added incompatible polymer is associated with the formation of larger voids. Modelling studies showed that increasing the interfacial energy between the two components of the blend causes a decrease in the critical stress for delamination. Interfacial tension values obtained from the literature 1 related qualitatively to the critical stress for void formation calculated using numerical analysis. Numerical analysis predicted a tendency to form depressions on the surface of the film near sub-surface voids, which was confirmed quantitatively by experiment.
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