Attaining durable painted plastic components

• Published in: JCT research Vol. 2; no. 5; pp. 351 - 360
• Main Author: RYNTZ, Rose A
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 2005
• Subjects: Applied sciences; Coating, metallization, dyeing; Coatings. Paints, varnishes and inks; Exact sciences and technology; Machinery and processing; Plastics; Polymer industry, paints, wood; Technology of polymers; Uses; Coating process; scratch resistance; Property processing relationship; Interface properties; Halogenated olefin polymer; Olefin polymer; chip resistance; Chlorine containing polymer; Pretreatment; Rupture strength; Painting process; Adhesivity; gouge resistance; Polymer blends; chlorinated poly(olefin); Propylene polymer; Elastomer; Mechanical properties; Thermoplastic rubber; Durability; Experimental study; Adhesion; Coated material; Surface treatment; plastic; Priming coat; cohesion; thermoplastic olefin
• ISSN: 1547-0091; 2168-8028

Adhesion to thermoplastic olefin (TPO) substrates, blends o f polypropylene (PP) and an elastomer, is often difficult to attain due to the low surface energy, nonpolar nature of the surface. One often specifies, therefore, that the surface of the substrate be pretreated. Pretreatment methods can vary, from oxidation of the surface, e.g., plasma or flame, to diffusion and mechanical interlocking of an applied polymer with the surface. Mechanical interlocking with the nonpolar TPO surface can be achieved through the use of an adhesion promoter, namely a chlorinated poly(olefin) (CPO). The type of CPO utilized, in addition to the types of solvents and heat treatments utilized, can substantially influence the degree of adhesion/cohesion obtained within the CPO/TPO system. This article reviews the factors influencing the adhesion/cohesion of painted TPO substrates. Heat histories, TPO molding variations, CPO types, including solvent and resin variations, and topcoat (basecoat/clearcoat) chemistries are all found to influence the adhesion/cohesion of the painted TPO assembly (herein termed "composite"). Once adhesion o f a topcoat system to the TPO substrate is achieved, however, the durability o f that system to external forces is in question. External forces acting upon the painted composite, e.g., compressive stresses, tensile stresses, and single and/or multiple impact forces, can lead to devastating consequences. Chip or impact resistance and scratch or compressive/tensile ("gouge") damage resistance can be affected by the choice of topcoat chemistries utilized. Topcoat frictional behavior, tensile strengths, and surface hardness were all determined to be influential factors in providing robust damage resistance to the painted composite.