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Material and design engineers are constantly faced with the task of selecting the best thermoplastic material for interior trim applications. The purpose of this paper is to relate the results of physical property testing and part evaluation to their plastics selection process to allow a more optimized material choice for automotive interior applications. The thermoplastics that were evaluated in this study are the two largest volume plastics used today in interior trim, ABS (acrylonitrile, butadiene, styrene terpolymer) and polypropylene.

Joining dissimilar parts in automotive interior trim applications has been accomplished by utilizing mechanical fasteners, organic and water based adhesives, and more recently, thermoplastic polymers. Recent trends towards reducing solvent emissions and waste management problems, improving the consistency of adhesive application, integrating parts, lowering parts fabrication costs, and designing a specified bond level has increased the use of thermoplastic adhesive films as bonding agents in several applications. Initial efforts began over fifteen years ago with Dow Adhesive Films (DAF) being designed for bonding interior trim fabrics to various substrates. Films have subsequently been designed to improve performance of many interior trim parts in many ways such as: improving water resistance, allowing the part to be molded before installation, imparting a slip surface to a part, and supporting a non-woven fabric.

The construction of most automotive interior headliners requires an adhesive material to bond polyurethane foam-backed fabric to a molded headliner shell. More than ten years ago, The Dow Chemical Company qualified and began supplying a thermoplastic adhesive polymer film for headliner applications which replaced wet adhesive systems at several fabricators. DAF 899 adhesive film has gained acceptance in the industry due to excellent performance, convenience, and cost effectiveness without additional waste handling or volatile organic emission concerns. Recent advancements in headliner design such as additional recessed areas with more demanding contours, new substrate materials and the desire for more efficient operations created an opportunity to design improved adhesive films to meet the emerging industry demands.

Thermoplastic polyurethane/ABS blends are being developed by The Dow Chemical Company to meet the high performance requirements for flexible bumper fascia. Features of these blends include paintability without priming, excellent low temperature impact after painting, good heat resistance, and lower specific gravity than other high performance thermoplastic materials. Thermoplastic polyurethane/ABS blends also have excellent flow properties, which will allow large, complex parts with thin walls to be molded easily.

Novel acoustical materials have been developed. The materials are thermoplastic foams extruded from blends of a polypropylene (PP) resin with an ethylenic polymer resin. One material is an open-cell sheet product made from a blend of a PP resin and a polyolefin elastomer (POE). Another is a large-celled plank foam of substantially closed-cell structure made from a blend of a polypropylene resin and a low density polyethylene (PE) resin. The foam materials are of lightweight, hydrophobic, dust free, recyclable and withstand the temperatures prevailing in automotive uses.

A family of thermoplastic Polyurethane (TPU) blends is being developed to compete in the flexible automotive bumper fascia market. Features of these blends include paintability without adhesion promoter or primer, ease of processing, outstanding low temperature impact strength, good mar resistance, and excellent property retention upon recycling. Laboratory and application performance data indicate that painted TPU/ABS Blend XT2100 regrind can be incorporated up to a 25% level into flexible thermoplastic fascia without sacrificing impact resistance.

Adhesive materials are required to bond cover fabrics to most molded interior headliner substrates. Several thermoplastic adhesive films are qualified and used at U.S. and Japanese OEM's. These adhesive films offer benefits such as convenience, cost effectiveness, excellent adhesive performance and process efficiency while reducing concerns of emissions and hazardous waste handling compared to prior bonding methods. The automotive headliner part is a multifunctional component of the vehicle's interior trim. One of the main headliner functions is to reduce the interior cabin noise. Various adhesive materials are used in a lamination process to form a composite headliner. The purpose of this study was to compare the effects of this lamination process and various alternative adhesive materials on the overall acoustical performance of the headliner composite. Various headliner samples were fabricated under controlled process conditions and tested by an independent acoustics testing lab.

A method for refining magnesium scrap which produces consistent, high quality magnesium metal has been developed. High quality magnesium metal is defined in this paper as metal which has heavy metal contaminants controlled within high-purity ASTM chemical specification, and is relatively free of internal impurities such as non-metallic inclusions (oxides and flux) and dissolved gas. The refining process utilizes a protective gas atmosphere, inert gas sparging and filtration techniques, rather than salt based fluxes, to remove both non-metallic inclusions and dissolved gases. Experimentation results of this refining process indicate magnesium scrap can be remelted and refined to a quality equal to or better than virgin ingot, without the introduction of salt based fluxes or a large capital investment.

Continued development of Reinforced Reaction Injection Molding (RRIM) polyurea polymers for toughness, blister resistance and large-part processing as exterior vertical body panels has launched ELPO-compatible exterior outers into automotive assembly-line operations. This allows automotive OEM design to take advantage of the unique molding shapes for side outers and fenders while reducing weight, assembly (DFA) and time/operations costs (DFM). Polyurea RRIM body panels have been successful in meeting the demanding auto industry requirement for lightweight, damage-resistant exterior outer panels as an economical alternative to steel. Design freedom advantages, low prototype cost and tooling savings through predictive modelling have allowed the commercial use of RRIM body panels. This high-temperature-resistant polyurea RRIM composite allows on-line painting, including passing through the steel corrosion protection primer (E-coat) cure environments.

Syndiotactic potystyrene (SPS) is a new semi-crystalline polymer under development by Dow Plastics, a business group of The Dow Chemical Company. The material is differentiated from conventional styrenic polymers in terms of microstructure and physical properties and represents the basis for an entirely new family of materials derived from crystalline polystyrene. SPS exhibits excellent thermal performance with a melting point of 270° C (520° F) combined with resistance to moisture and automotive fluids. Products produced from SPS demonstrate exceptional electrical performance, low specific gravity, competitive toughness and high modulus relative to other semi-crystalline engineering polymers. A wide range of products have been formulated including impact modified and glass reinforced resins for use in specific markets.

The objective of this paper will be to review a novel recycle process involving Structural Reaction Injection Molding(SRIM) which enables a variety of coarsely ground plastic recycle materials to be incorporated into the molded part. What makes this approach novel, is that flexural modulus of the fabricated parts are actually increased when the recycled granulate is employed in the part. This paper will present data for the recycle of a variety of automotive parts, including painted fascia, door skins, covered interior door panels, armrests and instrument panels along with composite bumper beams into the SRIM recycle core process. Resulting part economics will be reviewed along with potential applications to utilize this technology.

The American public's desire to recycle and the predictions of future recycle mandates are motivating automotive OEMs and plastic suppliers to address the recycling of plastic materials. As a result, the OEMs and plastic industry groups have asked resin suppliers, automotive dismantlers and reprocessors to assist them in studying and developing solutions for the recovery of post-consumer automotive plastics and recycling those materials back into automotive applications. The Dow Chemical Company has been a participant in plastic industry sponsored projects and has initiated numerous research and development activities involving the recycling of automotive thermoplastic and thermoset materials, as well.

The use of low density reinforced Reaction Injection Molded (RIM) substrates for covered interior automotive articles continues to increase globally. Reduced party mass, consolidation of manufacturing steps (labor), and the use of aluminum tooling, instead of steel, are cited advantages that LD-RIM offers when compared to traditional wood based and thermoplastic materials. Two RIM processes are successfully being used to produce covered interior door panels. Low density structural RIM (LD-SRIM), utilizing conventional RIM equipment, involves the placement of a pre-cut fiberglass mat in the tool cavity prior to open-pour injection of the 2-stream liquid urethane components. Low density reinforced RIM (LD-RRIM), utilizing lance cylinder RIM equipment, incorporates reinforcing fibers, such as milled fiberglass or wollastonite, in the liquid resin component. The liquid resin containing reinforcing filler is injected with the isocyanate component into a closed mold.

The opportunity for composites in engine closure systems such as valve covers, oil pans, and timing belt covers is expanding rapidly. The primary driving forces are lighter weight finished components, integrated designs, improved isolation of engine noise, improved materials systems, and matured manufacturing processes for composite materials. Thermoset-based composite materials, particularly those based on high-temperature resistant epoxy vinyl ester matrices, offer improved performance with respect to thermoplastic and thermoset polyester-based composites and can be manufactured using different processing methods. This paper presents the current state-of-the-art design, engineering and optimization techniques for engine closure systems. The performance requirements of different systems such as valve covers and oil pans are explained in detail. Techniques for long-term structural stiffness evaluation, vibration performance assessment and noise transmission estimation are described.

Structural instrument panels are an excellent alternative to traditional constructions since they can provide substantial part consolidation, weight reduction, tool and cost savings, and manufacturing and assembly simplification. In structural panels, the main energy absorbing element for decelerating an unrestrained occupant is the plastic integrated retainer-structural duct. The role of the components in the instrument panel needs to be clearly understood for adequately engineering the system and properly selecting the polymeric material for optimum system performance in the different operating environments. The present paper discusses the performance of the structural instrument panel, the engineering and design requirements, and provides guidelines for selection of materials.

Today's interior systems design engineer has been challenged with providing significantly lighter, simpler and more cost-effective instrument panel (IP) design solutions, while simultaneously meeting rigorous occupant protection and quality standards. These issues provided the motivation behind the fully-integrated structural instrument panel design developed for Chrysler's Dodge Dakota Truck Platform. This total system design approach greatly depends on the stiffness and ductility of the engineering thermoplastic substrate and cross-sectional design for managing the energy of unrestrained occupants during frontal collisions. The structural IP consists of a fully integrated, three-piece monocoque thermoplastic structure that replaces the traditional retainer, air delivery ducts, steel beams and reinforcements typically used in IP designs.

A fully-integrated thermoplastic structural instrument panel (IP) system will be implemented on Chrysler's Dodge Dakota Truck Platform. The structural IP consists of a three-piece monocoque thermoplastic injection molded structure that replaces the traditional retainer, air delivery ducts, steel beams and reinforcements typically used in IP designs. Ribbed thermoplastic bolster systems have been incorporated as part of the energy management system. The structural IP provides the required stiffness to satisfy noise, vibration, and harshness (NVH) quality targets and the necessary strength and rigidity to effectively meet FMVSS No. 208 requirements for managing occupant and passenger air bag (PAB) deployment loading during 48 km/h (30 mph) frontal crashes.

Increased requirements for crash energy management in automotive interiors have led to increased application of magnesium alloy AM50A. Successful integration of this new alloy with hot chamber diecasting process technology requires substantial adjustment and attention to processes and practices. This paper details the conversion of magnesium AZ91D steering column diecastings to high ductility structural alloy. Description is given of the changes made to foundry practices, casting parameters, process compliance monitoring, and hot end component management. The resulting improvements allow production of components comparable to the traditional alloy in manufacturing process demands while offering improved ductility and impact strength.

The recycling of plastics from end of useful life durable goods continues to evolve as an issue. Recycle strategies need to be based on a careful understanding of sustainability for both the environmental and business domains. The definitions and processes utilized in a recycle program can dramatically affect the economic structure. These recycle programs need to be carefully constructed to minimize cash costs. There is an emerging industry, recyclers, who may become an important link in the recycle supply chain.

The increase in instrument panel design and functional performance requirements has resulted in a variety of structural architectures that have been utilized in different passenger vehicles, vans, and light trucks. Each architecture can be designed and engineered to meet corporate and federal requirements using different levels of integration, functionality consolidation, and assembly simplification. The present paper reviews three basic IP design architectures, i.e., traditional, hybrid, and structural, and discusses the performance requirement-functionality matrix in each case. Emphasis is given at explaining the role components play in the different architectures, defining their contribution to static, dynamic and crash performance and their relation to the overall assembly process and sequence. Performance and functionality requirements are linked to basic material characteristics that guide material selection for achieving design targets.