THE EFFECT OF SURFACE CHARACTERISTICS OF POLYMERIC MATERIALS ON THE STRENGTH OF BONDED JOINTS

The degree of roughness and the linear direction of the abrasion proce ss operated over the adherend surface are two important design factors for the adhesive joint. Thus, in the first part of this study, the su rface roughness was varied by means of different grades of abrasive pa per and its effect on the joint strength was studied. An investigation involving changing the linear direction with respect to the loading d irection was also carried out. These experiments were done to determin e the effectiveness of the abrasion process for the pretreatment of th e adherend. A significant increase in joint strength was found for the abrasion treatment. However, it was shown that different linear direc tions did not have any significant effect on the joint strength. In th e second part of this study, thermodynamic analysis of the bonding of dissimilar polymeric materials using different adhesives in terms of t heir surface tension, critical surface tension, and joint strength was carried out. The aim of the study was to determine the thermodynamic criteria for maximum joint strength in bonding dissimilar materials. T he results showed that the joint strength was dictated by the adherend with the lower critical surface tension. Maximum joint strength for b onding dissimilar materials is attained when the surface tension of th e adhesive used is close to that of the adherend with the lower critic al surface tension.