Do surface pretreatments for adhesives influence the squeeze flow?

Recent adhesive research starts to consider more process oriented problems, in addition to the classical static stress and strength related topics, thus shifting towards a more global view on adhesive bonding. This includes the consideration of adhesive flow during application and joining of the substrates with all the information about initial application pattern and the resulting adhesive distribution contained after joining. Since the surface condition plays a major role and various different pretreatments are commonly used to improve the strength and durability of bonded joints while modifying their surface structure, the question of whether this influences the dynamics of the squeeze flow – or not – is addressed in this paper. In particular the materials glass and steel in combination with two designated surface pretreatments (blasting and flame-treatment) as well as their respective untreated reference surface are considered. For validation purposes the surfaces were characterized by means of roughness R_a and contact angle θ measurements, performed before and after the pretreatment, which resulted in a range of surface parameters for R_a from almost 0 to 3.3 μm and for θ from approximately 0 to 35°. However based on the measured force–displacement behaviour during the squeeze process no statistically significant difference regarding the dynamics of the adhesive flow could be observed between the untreated and pretreated surfaces for all investigated materials.