Relationship between the contact time of polymer surfaces and their bond strength

Films of amorphous polystyrene (PS) (mono- and polydisperse polymers) and poly(phenylene oxide) (PPO) were brought into contact at a low pressure (0.8 MPa) under temperatures T-h from 62 to 156degreesC The contact time t was varied from 2 min to 96 h. Partially "healed" PS-PS, PPO-PPO, and PS-PPO contacts were broken at room temperature and the shear strength sigma in the contact zone was measured. The experimental sigma-t curves were analyzed in double logarithmic coordinates. The value of alpha for the three interfaces investigated was within 0.07-0.32 at T-h < T-g, where T-g is the glass transition temperature. In the same way, the data on strength development taken from the literature for a number of polymer-polymer contacts formed both above and below T-g were analyzed, and the range of variations in alpha proved to be roughly the same (0.05-0.35). The results obtained are discussed within the framework of theories of molecular dynamics for the polymer bulk and the interface.