Weibull statistics of the lap-shear strength of a symmetric interface of amorphous poly(ethylene terephthalate)

For the first time, the distribution of the lap-shear strength (sigma) developed upon the contact of two amorphous bulk samples of poly(ethylene terephthalate) (PET) in the surroundings of the PET bulk glass transition temperature has been analysed as a function of healing temperature and healing time by using a Weibull statistical model. The Weibull parameters, Weibull modulus (m) and scale factor (sigma(0)) of partially self-healed symmetric amorphous PET-PET interface have been estimated by analysing some tens of the lap-shear strength experimental data sets. It has been found that the sigma(0)values are very close to the corresponding mean sigma values averaged for each test series, meaning that the Weibull analysis gives physically meaningful results. It has been shown that the majority of the sigma experimental data sets can be described properly with the standard Weibull distribution function proposed for brittle solids. Themvalues for the PET-PET interface have been compared with those reported recently for the polymer-polymer interfaces of non-crystallizable amorphous polymers. The impact of the potential ability of an amorphous polymer to crystallize on the scatter in the measured interface lap-shear strength has been discussed.