Coatings of Polymers and Plastics part 13 pps

F IG .3 In-mold process sequence. (From Ref. 7.) 289 290 Kakarala and Pickett trimmed, placed in an injection mold, and “back injected” with a thermoplastic material. The film has met the colorfastness, UV weathering, gloss, abrasion resistance, water jet, car wash, crosshatch, and gravelometer tests required by automobile manufacturers (9). This technology is used for the roof of the Euro- pean “Smart Car” subcompact (10). There exists advantages of films compared to coating. There is easier color matching between different production sites. Allows for rapid color changes. It eliminates the cost and maintenance of a paint line. It is environmentally friendly. 5.8 Extrusion Compression Molding with Film Inserts A film is placed in a compression mold. Plastic is extruded onto the film. Often times a reinforcing layer such as glass fiber matt is added. The mold is closed. The heat from the extruded plastic will heat the film for forming. The film provides a class A surface part. Films such as polyvinalinedifloride/acrylic, polyester, ionomer, and ASA have been used. The Valyi SFC, Surface Finishing/Compression Molding (SFC) process, has demonstrated the capability to manufacture large structural panels such as automotive roof tops, hoods, and trunk deck lids (11). The SFC process can be used to manufacture large class A exterior finishes parts at a low clamp force. The precolor matched films offer the part appearance in the mold, thus eliminat- ing painting. 5.9 Thermoform Coextruded Sheets A coextruded multilayer sheet is thermoformed. As with films, each layer of the sheet has a specific function. The top layer provides the weathering and UV resistance, scratch-and-mar resistance, hardness, and the gloss. The color layer provides the coloring, additional UV resistance, and adhesion. The base layer provides the structural support. During the coextrusion process, the materials are merged using an adapter system and are shaped by a slit die into sheets of varying thickness (12). Different thermoplastic materials can be combined using this process. Also, the regrind from the thermoforming offcuts can be recycled. After the sheets are coextruded, they are cut to size. The sheet is then heated, thermoformed, and cooled. During thermoforming, the sheet is drawn against the thermoform mold by a vacuum. The surface quality of the thermoformed sheet can equal that of painted panels (12). It must be noted that the surface roughness increases with the depth of thermoforming (12). A thinner residual wall thickness will result in a rougher surface. This will lower the gloss of the finished part. Also, for metallic colors, the greater the number and size of the particles, the rougher the surface (12). This technology is limited to parts that can be thermoformed. Thermoform Alternatives to Coatings for Automotive Plastics 291 tooling is inexpensive. Achieving a high-gloss level is difficult with the thermo- forming process. Body panels made of PMMA/ABS have a proven track record on the Ligier small vehicles in Europe (12). Also, the Hotzenblitz, an electric car in Germany, and the PIVCO, a Norway electric car, have body panels from PMMA/ABS without painting (9). The PMMA provides the UV and weather- resistant outer layer. The impact strength at low-temperature is provided by the ABS layer. The finished body panels are mounted to a steel framework. The plastic body panels provide a weight savings compared to steel body panels (12). 5.10 Mold-In Color with Clearcoat General Electric Xenoy PC/PBT with clearcoat polyurethane (PUR) is used to mold body panels for the European “Smart Car.” The clearcoat offers the UV and scratch-and-mar protection. Smart Car colors are offered in red, yellow, black, and white straight shades. This process still uses a coating, clearcoat. However, it eliminates the primer and basecoat. 6 AUTOMOTIVE APPLICATIONS WITH ADVANCES IN PROCESS TECHNOLOGY Advances in the extrusion and coextrusion process have resulted in mold-in- color exterior and interior automotive plastic trim parts. For example, extrusion process is commonly used for mold-in-color body side moldings. Mold-in-color fascias, claddings, exterior and interior trim parts are manufactured by injection molding and co-injection molding. Advancement in both film technology and processing has allowed the manufacture of parts ranging from applique ´ sto whole body panels on vehicles. 7 CONCLUSION Alternatives to coating automotive plastics have received increased attention in developing new materials and process technologies to meet the demands of the automotive industry. These advances have been used successfully in a number of automotive applications. For example, advances in development of new col- orants and additives has allowed mold-in color to be used in more applications such as mold-in accent color, mold-in straight shade body color, and mold-in- body-color metallics. In addition, development of extrusion, injection molding, thermoforming, and insert molding of films processes has allowed OEMs alter- natives to coatings for automotive plastic applications. Challenges still remain. For example, color matching is a real concern with mold-in-color plastics both initially and after weathering. In the future, continuous advances in both materi- als and process technologies will allow alternatives to coatings to make further inroads into the automotive plastic applications that are currently coated. 292 Kakarala and Pickett REFERENCES 1. A Grefenstein. Coextrusion of PMMA-coated plastic sheets and films as an alterna- tive to painting of plastic body panels. IBEC ’97 Automotive Body Painting, pp 89–91. 2. CJ Reilly. Light stabilizers. Modern Plastics Encyclopedia ’97, 73(12):C-24, 1996. 3. J Cafferty. Colorants. Modern Plastics Encyclopedia ’97, 73(12):C-20, 1996. 4. General Motors, U.S., 1993 (Thomas Pickett, et al.). Patent number 5,264,164. 5. General Motors, U.S., 1985 (Fred Schmidt, et al.). 6. L DeBow. Honda picks dry paint film for civic side moldings. Automotive Plastics 18: February 2001. 7. The alternative to painting: economical and ecologically friendly. The Senoplast In-Mold Film Brochure, 1997. 8. Alliance develops paintless film systems for auto exterior parts. European Plastics News 25(9):30, 1998. 9. Senotop in-mold films as paint-replacement for injection molded car body parts and car body parts made of fiberglass-reinforced polyurethane. The Senoplast In- Mold Film Brochure, 1997. 10. BASF aktiengesellschaft: paintless film molding. Modern Plastics 70, April 1999. 11. S McCarthy, Q. Guan, C. Makadia, T. Ellison. Class A thermoplastic automotive part production without painting. ANTEC 2654, 2000. 12. H Kappacher. Car bodies made of PMMA/ABS. Piesendorf/Austria. 9 Trends in Coatings for Automotive Plastics and Rubber in North America and Europe Robert Eller Robert Eller Associates, Inc., Akron, Ohio, U.S.A., and Bordeaux, France 1 INTRODUCTION AND OBJECTIVES In this chapter we examine the forces driving the selection of coatings and associated process technology for the modification of plastics and rubber sur- faces. Primary emphasis is on the North American auto industry. Where the technology and trends are applicable to (or derived from) nonauto markets, we have so indicated. 1.1 Geographic Coverage The need to be competitive in the global marketplace has made the barriers to technology transfer quite transparent. We have therefore indicated and, in some cases, quantified material substitution trends in Japan or Europe likely to affect North American coating technologies and the associated demand. 1.2 Trends We have sought to present a view of the future as seen from the perspective of our recent work in the automotive sector. Where the current implication of fu- ture trends is not clear we have so indicated and sought to define the decisive factors. 1.3 Substrate Type Coatings for both plastics and thermoset rubber are included. Because the inter- face between thermoset rubber and plastics is becoming blurred by the use of 293 294 Eller thermoplastic elastomers (TPEs), we have included these materials in the scope of the automotive polymers to be coated. 1.4 Definitions We have used the term coating to include not only liquid coatings and paints but also skins, textiles, and other materials designed to modify the surface prop- erties and characteristics of automotive polymers in interior soft trim and exte- rior applications. A summary of the abbreviations used and a list of references is given in the glossary at the end of the chapter. Non-English terms (usually German or French) are commonly used without translation to characterize sur- face qualities. Their definitions are also included in this chapter’s glossary. 2 THE DYNAMICS OF COATING SELECTION 2.1 Functions Coatings on the polymer substrate provide some or all of the functions described in Table 1. T ABLE 1 Functions of Coatings for Automotive Polymers Function Note/Example Color Competes with molded-in color Introduce texture Usually with textiles, skins, coated fabrics Introduce pattern Recently molded-in patterns Dry films (e.g., wood grain) Gloss control Needed for polyolefin-based skins Scratch/mar resistance Needed for polyolefin substrates Elimination is major research and development objective “Touch” modification Haptik in German UV protection Requirements increased with longer warranty Mold release Adhesion of flocking For thermoset rubbers in window channels Control surface friction For movable windows Eliminate ice adhesion Body/glazing seals Modify surface acoustics Gaining importance in interior surfaces EMI shielding Will grow with electronics content, telematics Acoustic modification Applies to all surfaces Wear surfaces e.g., noncarpet flooring Source: Robert Eller Associates, Inc., 2001. Trends in Coatings for Automotive Plastics and Rubber 295 2.2 The Plastic Processor’s Perspective For the plastics processor, the application of coatings to the surface of molded parts adds cost, the uncertainties of adding liquids and the associated “wet chem- istry,” and an additional operation that increases capital investment and broadens the quality control requirements. Some (usually large) plastic processors have turned this burden into a competitive advantage by installing high-volume, highly automated, closely controlled spray booths, which contribute to profitability and provide an entry barrier against smaller competitors. (Bumper fascia fabricators are an example of such large volume molder/coatings suppliers.) Roll goods manufacturers apply coatings to skins or coated fabrics using spray or reverse roll coating. 2.3 The Automotive Coatings Market Liquid coating materials, process technologies, and performance requirements are reviewed in other chapters of this book. The dynamics and economics of plastic and rubber parts manufacturing require that the design engineer examine alternatives to liquid coatings such as: • Molded-in color (see Chapter 1); • Surface skins, textiles, and coated fabrics applied off-line (see follow- ing discussion); and • In-mold decoration using films, carpet, textiles (see following discus- sion). The auto polymer coatings market has been (1) defined in terms of sub- strate type (hard/soft), substrate material (polymer type), and module (instru- ment panel [IP], door trim [DT], floor). A summary of the applications that use liquid coatings and the alternatives is presented in Figure 1. The target zones in interiors and exteriors for coatings are summarized in Table 2. 2.4 The Measurement Problem The driver typically spends 40,000 hours at the steering (2) wheel facing the instrument panel. The choice of surface treatment (hard, soft, textile, patterned, colored, etc.) is therefore critical to the auto original equipment manufacturer (OEM). Physical and chemical tests quantify technical performance (scratch/mar, ultraviolet (UV) resistance, oil resistance, color shift, etc.). Despite the eco- nomic importance of surface treatment selection, techniques for the quantifica- tion of sensorial attributes of the interior surface to measure their importance to the consumer have not been developed. Renault and other OEMs (3,4) have employed techniques derived from methods used in the agro-business sector to 296 Eller F IG .1 Automotive plastic coating alternatives. Note: (*) indicates liquid coatings opportunity target. (Courtesy of Robert Eller Associates, Inc., 2001.) identify and quantify the sensorial attributes and their perception by humans. The techniques are in the early stages of development and only vaguely quantified, but appear to represent a starting point to the response to such questions as: • What is the perceived value to justify the cost penalty for substituting a skin for hard substrate? • Do the customers care about exact grain matching as much as the interior trim designer? • What is the role of color and pattern matching between modules? • What is the value of the utility function (e.g., washable, noncarpet floor module surfaces)? • What is the value of touch (“haptik”) in consumer quality perception? • What is the role of olfactory perceptions (some OEMs are seeking zero smell interiors)? Trends in Coatings for Automotive Plastics and Rubber 297 T ABLE 2 Target Zones and Alternatives to Coatings on Automotive Polymers Liquid coating competitor Sub Typical Location type form Example IMD MIC 2SHT SKINS TEX CF CPT LTHR COEX Exterior Flex Fascia X X X b Rigid Trim a XX X b Interior Rigid Instrument panel X X X X X Door trim X X X X X X X X Flex Skins Instrument panel X X X e XX c Coat fab Seating X X X X Textile Headliner X d X Sheet Flooring ? X X X Interior/ Flex Glaze seal X X X exterior Body seal X X X interface Rigid Glaze seal X X X Body seal X X X a For example rocker panel, cowl vent, rear panel, pickup truck box. b Two-shot sandwich molding for rocker panel (TPE on ETP) starting in Europe. Two shot (side by side) is often used in fascia molding. c Leather used on some European high-end IP models in Europe. d Skin usage for headliners has essentially declined to zero except in some heavy truck applications. e Two-shot molding for instrument panels started in mid-1990s. Will likely grow. Source: Robert Eller Associates, Inc., 2001. 298 Eller 2.5 Requirements for Interiors and Exteriors Liquid coating technologies used on interior and exterior plastic surfaces are somewhat similar. The range of nonliquid coating surface treatments and perfor- mance requirements for interior and exterior automotive surfaces is considerably different as shown in Table 3. 3 DRIVING FORCES AND TRENDS IN COATING USAGE The macro-economic, automotive technology and module fabrication technol- ogy driving forces and trends affecting coating use and intercoating competition are reviewed in Table 4 (1). T ABLE 3 Interior/Exterior Coating Requirements/Opportunities Parameter Interior Exterior Note Soft trim X Skins opportunities Accurate grain X Decreased requirement reproduction for grain matching Acoustics X Requirements increased by growth of telematics Liquid coating on X soft trim Substrate type Hard/soft Hard Soft: rubber, TPE, skins Zero smell X requirements Scratch/mar X X Different requirement levels Match painted body X (Some X metal applications) Tactile requirement X Fluid resistance X X Different fluids Dominant substrate ETP, PP (solid/foam), TPO (fascia), TPE, skins, coat thermosets, ETPs fabrics NVH requirements Important Not important Surface parts X (More X (Highly integrated) integration opportunities) Wood grain X Brushed metal X X Metallic pigments X (Minor) X (Major) Coated fabrics X Liquid coating opportunity Skin/foam/substrate X Source: Robert Eller Associates, Inc., 2001. [...]... Focus) has not gained much momentum to date 3.5 Role of the Interior Soft Trim Fabrication Process Soft interior trim typically consists of a three-layer sandwich of skin (or textile), foam, and substrate Off-line processes that combine these three layers to produce interior soft trim are complex, multistep, wasteful, and labor intensive The rate of change of interior module fabrication processes during... penetration points for TPEs and associated coatings in body, glazing seals, and acoustic systems Note: (A) acoustic opportunity (Courtesy of Robert Eller Associates, Inc., 2001.) Trends in Coatings for Automotive Plastics and Rubber 311 FIG 6 Cross-sections of body seals (Courtesy of Robert Eller Associates, Inc., 2001.) 4.5.3 Role of Colors The use of high concentrations of carbon black as the reactive... signs of a trend toward printed patterns on skin surfaces and the coordination of patterns between instrument panel, door trim, flooring, and seating The Trends in Coatings for Automotive Plastics and Rubber 313 utilization of highly patterned seating began in the European market in the mid1990s This trend has accompanied the growth of TPO skins on several modules (IP, DT, floor) The development of patterns... implications of the revised German legislation on interior substitution have been reviewed by the author (7) Ryntz reviewed recycling implications on coatings in Chapter 7 of this book 3.2 Economics as Coating Substitution Driver The high capital investment and operating cost burden of coatings can double the cost of molded parts (e.g., bumper fascia and IP substrates) Substitutes for coatings thus... Based on 2001 model year Cast and gelled from PVC plastisol; often called unsupported expanded vinyl (UEV) c Both thermoset (e.g., spray) and thermoplastic (e.g., TPU slush) b Source: Robert Eller Associates, Inc U.S., Europe Multiclient Studies Trends in Coatings for Automotive Plastics and Rubber 303 FIG 2 Interior skin materials and process options for instrument panel and door trim Notes: (*) indicates... newer generation of TPOs based on metallocene catalysis may have the capability of enhancing the competitive position of the TPOs in this growth sector for injection molded acoustic barriers 310 Eller 4.5 Body and Glazing Seals 4.5.1 Markets Automotive body and glazing seals represent a market potential of approximately 120,000–140,000 tons in each of Europe and North America (6) and have the potential... seek profitable material substitutions 3.3 Acoustics Acoustic performance has often been an afterthought rather than an integral part of the initial vehicle design A broad range of acoustic materials is used (8) This has often resulted in messy solutions with high systems costs (e.g., asphaltbased floor module acoustic barriers) Increased use of telematics, improved acoustic profiling techniques, and. .. percent of fleet in Europe —Surface skins/textiles —Substrate structure —Originate in German OEMs (e.g., Audi) —Unfavorable for TPO skins —Favors non-PVC skins/coated fabrics —Adjustment of spray PU and TPU formulas —Favors in-mold processes —Favors non-“itch” surface treatments TABLE 4 Driving Forces and Trends Affecting Coatings for Automotive Polymers Trends in Coatings for Automotive Plastics and Rubber... Increased telematics Reduction of liquid coatings Hydrocarbon emission reduction Elimination of off-line skin forming Reduction of NVH Energy management Match to painted metal Interior, exterior trim Retro look For example, offered by Collins & Aikman, Lear, Reiter, others Source: Robert Eller Associates, Inc., 2001 a Interior Interior soft trim Acoustic control Interior soft trim exterior in-mold Injection... usage 4.5.2 Incumbents and Challengers Body seals are the stronghold of EPDM extruded profiles A range of incumbents (PVC, EPDM, PU-RIM) is used in glazing seals (12,14) Some of the vehicle positions in which these applications are used are illustrated in Figure 5 Some of these are in close proximity and are becoming integrated with interior panels The belt line molding at the base of the movable door . the surface prop- erties and characteristics of automotive polymers in interior soft trim and exte- rior applications. A summary of the abbreviations used and a list of references is given in. 2001. Trends in Coatings for Automotive Plastics and Rubber 295 2.2 The Plastic Processor’s Perspective For the plastics processor, the application of coatings to the surface of molded parts adds. momentum to date. 3.5 Role of the Interior Soft Trim Fabrication Process Soft interior trim typically consists of a three-layer sandwich of skin (or textile), foam, and substrate. Off-line processes