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Effects of water sorption on the physical properties of PET, PBT, and their long fibers composites
Author(s) -
Bastioli C.,
Guanella I.,
Romano G.
Publication year - 1990
Publication title -
polymer composites
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.577
H-Index - 82
eISSN - 1548-0569
pISSN - 0272-8397
DOI - 10.1002/pc.750110102
Subject(s) - materials science , composite material , crystallinity , izod impact strength test , fracture toughness , glass transition , sorption , activation energy , fracture (geology) , toughness , diffusion , polymer , ultimate tensile strength , chemistry , thermodynamics , physics , organic chemistry , adsorption
The behavior of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) on water aging has been studied above and below the glass transition temperature ( T g ). The aging process is caused by: degradation of the matrix and an increase in crystallinity above T g , and microcavitation at the amorphous/crystalline interface below T g . Such behavior well explains the deviation of the sorption kinetics from the Fickian model. The apparent water diffusion coefficients and the transport activation energies of PET and PBT have been calculated at temperatures above and below T g . The mechanical behavior of the two polymers on water aging has been measured by means of fracture mechanics and Izod impact tests at different stress concentration factors. An increase of toughness of PET at short aging times has been shown by mechanical tests and SEM analysis fracture surfaces of differently aged samples. Izod tests of PET and PBT composites reinforced by long glass fibers have shown the contribution of fibers to the total fracture energy.