What is a TPO and what factors affect adhesion to TPOs?
TPO is a general abbreviation for thermoplastic polyolefin. Thermoplastic polyolefin generally describes that family of plastics made of polypropylene modified with an impact modifier. Common impact modifiers used are ethylene-propylene diene monomer (EPDM), plastomers, and low molecular weight polyolefin. The level of impact modifier may be as high as 40% in some TPOs that use EPDM or as low as 5%–8% using the other impact modifiers. The flexural modulus (stiffness) of TPOs varies widely and as a general rule obtaining paint adhesion to those with higher flexural modulus is more difficult. This answer/suggestion/or other is based on intuitive interpretation of related data and experience and as such has no direct substantive supporting data. You should therefore be guided in your evaluation of the sufficiency of this answer by making your own independent evaluation as to what will or not work for solving the problem facing you.
