Statistical aspects of diffusive adhesion between polymers with drastically different molecular mobility: Weibull’s and normal probability analysis

A comprehensive statistical analysis of the distributions of the lap-shear strength (σ) originated during the contact of the specimens of dissimilar miscible entangled amorphous polymers with drastically different bulk glass transition temperatures (Tgb) has been carried out in the vicinity of the Tgb of one polymer but well below the Tgb of the other. For this purpose, polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were chosen. To form mechanically durable PS-PPO adhesive joints (AJ) via the chain interdiffusion mechanism, the specimens of PS (Tgb = 103°C) and PPO (Tgb = 216°C) were kept in contact for a period of time (t) of 2 min to 96 h at a constant bonding temperature (T) in the vicinity of the PS Tgb but, at the same time, well below (even by 126°C) the PPO Tgb. The AJs formed were shear fractured in tension at ambient temperature. Totally, 21 σ datasets measured have been analyzed using Weibull's and normal probability models. By using proposed two dimensionless statistical parameters, the reciprocal Weibull's modulus (1/m) and the standard deviation (SD) reduced to the average σ value (σav), SD/σav, the data scatter estimated in the two methods have been compared.