Abstract
The tear resistance behaviour of semicrystalline polymeric networks is characterized by noted variations from the behaviour of amorphous polymers, due to the existence of crosslinks and crystallites. A theoretical analysis and experimental investigation of this phenomenon was undertaken using crystalline poly(vinyl alcohol) hydrogels which were prepared by electron beam irradiation of aqueous PVA solutions followed by a two-stage dehydration—annealing process. The tear propagation resistance depended on the time—temperature history, the crosslinking density and the crystallinity of the hydrogels; the values varied between 700 and 1400 J/m 2 (4–8 ppi) depending on the above parameters. A relationship between tear resistance and degree of crystallinity was obtained, within the range of experimentation of this work. The tearing energy of the same films was a function of the crosslinking density; a theory for prediction of the tearing energy was established. Typical values for semicrystalline networks were higher (up to 1500 J/m 2) than those reported for amorphous networks, mainly due to the crystallites introduced in the network after annealing.
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