Statistics of strength distribution upon the start of adhesion between glassy polymers

For the first time, the strength distribution upon the bonding onset between the contacting glassy polymer samples has been analysed by employing the Weibull statistics. It has been found that the distribution of the lap-shear strength (σ) developed between the contacting pieces of such representative amorphous polymers as atactic polystyrene (PS) and poly(methyl methacrylate) (PMMA) at the time-temperature healing conditions at which the interface bonding starts follows the Weibull distribution function. It has been shown that the σ distributions for the compatible PS-PS and PMMA-PMMA and incompatible PS-PMMA interfaces are not affected by the factor of thermodynamic compatibility of the PS and PMMA segments. The estimated values of the Weibull modulus m and of the scale parameter σ0 for the weak polymer-polymer interfaces investigated have been compared with those estimated for the tensile strengths of the PS and PMMA monolithic bulk samples which were used for the interface healing experiments and of the ultra-high-strength inorganic quasi-brittle materials reported in the literature.