EFFECTS OF COATING SOLVENTS ON THE MORPHOLOGY OF THERMOPLASTIC POLYOLEFINS (TPO)

Adhesion to thermoplastic olefin (TPO) substrates is strongly influenc ed by the type and amount of solvent contained within paint applied. M orphological changes in the TPO substrate are accomplished in the pres ence of solvent from the coating and vary depending on paint bake time s and temperatures, This paper attempts to delineate the influence of paint and paint processes on the adhesion/cohesion and mechanical prop erties of coated TPO parts, Initial adhesion to TPO appears to be a fu nction of polypropylene crystallinity at the surface only as it relate s to the ability of solvents to permeate through and into the rubber-r ich layer beneath it. The amount of swelling of the rubber-rich layer can result in a lowered cohesive integrity of the top TPO layer. One m ust carefully select the correct solvent balance contained within the paints applied to TPO. It is essential to attain swelling within the s ubstrate to afford initial paint adhesion, but the sole,vent must evap orate and the rubber shrink (deswell) to attain cohesive integrity of the substrate once painted.