1. Overview of Polyurethane Material Applications

　　Polyurethane materials are increasingly widely used in the automotive industry and have become one of the most extensively consumed types of plastics in vehicles, with global annual consumption exceeding 1 million tonnes. In 2006, China’s automobile production surpassed 7.2 million units, driving total polyurethane consumption to more than 100,000 tonnes. Polyurethane typically accounts for about 15% of all plastic used in automobiles, with an average usage of 15 kg per vehicle, predominantly in the form of MDI-based products.

　　Depending on the specific automotive component, polyurethane is formulated into various forms and properties—such as foams, elastomers, and adhesives—to meet diverse performance requirements. For instance, polyurethane foams, through adjustments in formulation, exhibit characteristics such as light weight, excellent thermal insulation, superior resilience, enhanced comfort, outstanding low-temperature performance, durability, high safety, and strong vibration-damping capabilities, making their advantages unmatched by other materials.

　　The recycling of waste expanded polystyrene (EPS) from automobiles and household appliances has increasingly attracted attention. Recently, foreign automakers have succeeded in incorporating up to 30% recycled EPS into their products. The process involves cleaning, crushing, and drying the waste EPS, followed by bonding the fragments with an adhesive, after which the material can be used to manufacture carpet backings and other cushioning materials.

　　2. Automotive Interior Parts

　　2.1 Dashboard

　　(1) Surface material

　　Currently, automotive manufacturers are striving to further enhance the comfort, safety, and aesthetic appeal of vehicle interiors, driving a clear trend toward greater sophistication. This move toward higher-end interiors is first reflected in the use of a diverse array of materials with varying properties—such as fiber fabrics, genuine leather, and tufted textiles—to soften and beautify all interior surfaces through intricate patterns, rich woodgrains, and carefully coordinated color schemes. These soft-touch surface materials are then integrated with sound- and vibration-absorbing materials as well as structural components to form elements like headliners, premium instrument panels, steering wheels, and seats. However, this evolution inherently conflicts with the goals of material recycling and cost reduction. Consequently, there is an urgent need to develop new interior materials that can simultaneously meet the demands for high-end, soft-touch, and personalized designs while also delivering lightweight construction, low costs, and recyclability.

　　Securing supplies is the top priority.

　　BASF has developed Elastoskin, a polyurethane thermoplastic elastomer (TPU) skin material for automotive interior trim, intended for use as the surface layer on instrument panels and door panels. Its performance surpasses that of currently used polyvinyl chloride (PVC) and other skin materials, while its cost is lower than PVC and similar alternatives, making it an ideal substitute for PVC. This material boasts excellent mechanical properties, a remarkably realistic leather-grain texture, exceptional flexibility, and a luxurious aesthetic; it is also suitable for two-color components. Its outstanding durability—resistance to weathering, extreme temperatures, and abrasion—makes it the preferred choice for high-quality, Class C and above passenger-car interior trim skins. The material has already been employed in the instrument panels and door inner panels of models such as the Buick Park Avenue, Oldsmobile Aurora, and Cadillac CTS, and will also be used in new models like the Cadillac Seville and Cadillac Deville. In short, the application of this material in automotive interior trim is only just beginning. Moreover, the use of aromatic polyurethane spray-on skin technology holds significant value in providing an effective pathway for producing recyclable integrated polyurethane dashboards that combine a polyurethane spray-on skin, low-density polyurethane cushioning foam, and a polyurethane chopped-fiber structural core.

　　In addition, Bayer’s thermoplastic polyurethane is produced using blow molding for automotive instrument panels and door panels. It is reported that this process can reduce cycle time by 70% compared with injection molding.

　　(2) Dashboard Cushion Layer

　　The instrument panel’s outer skin is formed by vacuum molding, with a semi-rigid polyurethane foam core sandwiched in between and securely bonded to a metal or plastic structural frame. This semi-rigid polyurethane foam boasts high compressive load-bearing capacity and outstanding vibration-damping performance, making it ideally suited for use as a protective cushioning material in automotive instrument panels as well as in components such as armrests and door pillars.

　　(3) Skeletal Material

　　A polyurethane structural reaction injection molding (SRIM) technology is already widely used in Europe and North America and can effectively reduce the weight of automotive components. The process involves first preforming the skin layer, placing a glass-fiber mat into the mold, and then injecting polyurethane resin followed by curing and molding (with micro-foaming). This process can be used to produce a variety of interior trim parts, such as door panels, coat hooks, instrument-panel frames, and headliner frames. A key advantage of SRIM is its flexibility in designing wall thickness, curvature, and reinforcing ribs to meet the specific mechanical performance requirements of each component. Compared with injection-molded parts, SRIM results in lower in-cabin noise and enhances the material’s physical properties, including lower density, higher elongation at break, reduced odor emission, and improved resistance to mold growth, thereby creating a more comfortable cabin environment. In China, the current production technology for door panels involves pre-laying glass fibers in the mold, then injecting a polyurethane system; after closing the mold, the part is cured and molded into the desired interior components, such as instrument panels, door panels, and air-conditioning covers. Another technique is short-chopped glass-fiber spray molding.

　　Polyurethane products manufactured using RIM and RRIM technologies are primarily used in automobiles for steering wheels, bumpers, body panels, hoods, trunk lids, radiator grilles, fenders, and spoilers. Although RRIM parts weigh only 55% of their steel counterparts, their surface quality and dimensional stability still require further improvement, limiting their overall application volume.

　　2.2 Vehicle Seat Cushions, Backrests, and Headrests

　　Seat cushions, backrests, and headrests are among the largest applications of polyurethane foam in automobiles and are also the areas most sensitive to ride comfort; consequently, the performance requirements for these components are extremely stringent. Currently, most polyurethane foam seat cushions used in domestic vehicles are uniform-density, cold-cured products. In recent years, a new type of automotive seat cushion has emerged that employs dual- or multi-density foam. Such dual-density cushions can be manufactured either by injecting a polyether polyol–isocyanate mixture through a two- or multi-head mixing unit directly into the mold, or by using an all-MDI cold-molding process, in which the isocyanate index is adjusted to precisely control the hardness of different regions of the cushion—soft in the central area and firmer at the sides. The softer foam provides comfort, while the harder side sections offer superior support, helping to maintain the stability of the driver’s and passengers’ bodies during high-speed driving or cornering and thereby enhancing ride safety. FAW Group’s Fu’ao Company has already adopted a three-component blending technology to produce both dual- and multi-density foams, placing it at the forefront of this technology in China.

　　2.3 Door Handrails

　　The armrest features a steel frame embedded in the door panel, with an outer layer of self-bonded semi-rigid polyurethane foam that is both decorative and comfortable, providing passengers with a sense of comfort and security. The left and right interior door panels of the sedan also incorporate armrests, constructed from either self-bonded semi-rigid polyurethane foam or a plastic-coated shell with foam core. Materials used in these areas must be sweat-resistant, odorless, and exhibit excellent hardness, as well as superior performance under high and low temperatures.

　　2.4 Steering Wheel Assembly

　　In China, the steering wheels of passenger vehicles typically feature a semi-rigid, self-bonded polyurethane foam outer cover layer, with an internal steel skeleton formed by welding; however, there is a gradual shift toward integral die-casting of aluminum–magnesium alloys. The hardness of the outer cover layer generally ranges from Shore A 60 to 80.

　　2.5 Foam Plastics for Sound and Thermal Insulation Applications

　　(1) Car roof lining and door inner panels

　　The vehicle interior roof is a composite product formed by laminating and processing various materials, and is required to exhibit multiple functions such as thermal insulation, sound absorption, sound insulation, and vibration damping. Soft roofs are made from polyurethane foam combined with fiber fabrics, nonwovens, and synthetic leather, while rigid roofs are produced by laminating and compressing fabric fibers, glass fibers, cardboard, and polyurethane foam.

　　Polyurethane foam sheets are also widely used in automobiles; for example, seat upholstery today commonly consists of a textile layer combined with PU and knitted synthetic fibers. The headliner is typically made by laminating a PVC film with PU, then punching small holes in the surface before bonding it to the interior roof panel. Door pillar trim panels often use PP and PPO. Given material cost considerations, PP grades that offer high flowability, high rigidity, and excellent impact resistance will have a distinct advantage going forward. The surface color of door pillar trim must harmonize with the overall interior color scheme and meet requirements for antistatic properties, scratch resistance, and aesthetic appeal; therefore, developing production technologies that integrate acrylic sheet materials with surface decorative finishes through vacuum forming or thermoforming can effectively meet the needs of small-batch passenger car manufacturing.

　　(2) Polyurethane foam for sealing

　　Rectangular, soft polyurethane foam sealing blocks are used in the vehicle’s heating and air-conditioning system, the instrument panel assembly, electrical components, and other areas. Foam is also injected into the cavities of the A- and B-pillars to reduce body vibration and noise, often in combination with vibration-damping expansion films.

　　3 Microporous polyurethane used as vibration-damping pads for vehicle underbody panels

　　Microporous polyurethane foam is poised to replace rubber materials in most vehicle bodies as underbody vibration-damping pads, as North American automakers strive to make vehicles quieter and more comfortable. These damping pads are mounted on the vehicle’s chassis to isolate the body from the frame, thereby enhancing ride and driving quality. Microporous polyurethane is a cutting-edge material that delivers exceptional noise, vibration, and harshness (NVH) performance.

　　Microporous polyurethane, as a substitute for rubber body assemblies, offers competitive pricing, effectively enhances vibration-damping performance, extends the service life of material properties, reduces weight, and improves assembly processes. Another advantage of using microporous polyurethane is that, by adjusting material density, the vibration-isolating pads for the vehicle chassis can be readily optimized—eliminating the need, as in conventional methods, to modify the material formulation or product geometry. The latter approach requires prototype development, which is costly and time-consuming. A composite structure comprising low-foam PVC, PU foam, and porous materials is commonly used in light commercial vehicles: the low-foam PVC is vacuum-formed and shaped, locally filled with foamed PU, and partially backed with porous material. This structure combines excellent elasticity with a firm, supportive feel, while also delivering superior foot comfort, sound insulation, and thermal insulation.

　　4 Refrigerated Vehicle Insulation Layer

　　To effectively ensure the soundproofing and thermal insulation performance of the vehicle body interior, in addition to using rigid polyurethane foam for the insulation layer in refrigerated trucks, van-type panel vans also employ on-site spray-foaming to expand the application of rigid polyurethane foam: rigid polyurethane foam is sprayed directly onto the interior surfaces of the roof and side panels and bonded to both the inner and outer skin of the body to form an integrated structure. This approach significantly enhances the vehicle’s thermal insulation, heat retention, and sealing performance, while also preventing body corrosion, reducing body vibration, and lowering interior noise levels. The estimated consumption per vehicle is approximately 20 kg.

　　Engine heat shields made of rigid polyurethane foam are fabricated by laminating and compressing layers of polyurethane foam, glass-fiber mat, nylon fabric, or aluminum foil, resulting in a lightweight structure with excellent thermal insulation properties.

　　The application of glass-fiber-reinforced polyurethane foam in automotive components is also steadily expanding; for example, integral roof trim panels are manufactured using textile-reinforced, glass-fiber-modified PU. Similarly, wheel arch fenders and oil pan splash guards are thin, complex-shaped parts that demand stringent manufacturing processes, as well as resistance to stone-chip impact, high impact strength, and excellent performance across a wide temperature range.

　　5. Prospects for Applied Technology

　　Recently, many automotive interior components have shown a trend toward replacing polyurethane (PUR) materials with polyolefin (PO) foams. Several types of polyolefin foams are increasingly challenging the widespread applications of PUR foams in areas such as surface layers for automotive interior trim, foam cores, coated fibers, fabrics, and sound-insulation systems. The primary drivers behind the substitution of PUR foams with expanded polyolefins are lower product costs, improved recyclability, and the potential to reduce toxic gas emissions—since the thermal lamination of fabrics with PUR foams can generate harmful fumes.

　　Automotive instrument panels are multifunctional, composed of numerous components, and feature a complex structure; therefore, they should be the primary focus for the recycling and reuse of interior automotive materials. Currently, most instrument panels consist of a PVC skin, semi-rigid expanded polyurethane foam, and a structural skeleton, making material recovery and recycling highly challenging. The future trend in instrument panel design is to prioritize ease of disassembly and assembly, select materials that meet design specifications while also considering recyclability, and strive for both aesthetic appeal and cost-effectiveness. This could drive the development of thermoplastic instrument panels and single-material plastic panels, provided that safety and aesthetic requirements are fully met.

　　Passenger car interior headliners are typically formed by laminating glass fiber, expanded polyurethane, and a surface decorative fabric. In contrast, commercial vehicle headliners generally consist of foam sheets coated with synthetic leather or fiber fabrics that are adhered to the roof panel. In light of functional requirements and recycling considerations, future trends point toward using the same material for the structural framework, sound-absorbing layers, thermal-insulating layers, and surface coverings, or toward employing reinforced composite materials that do not require separation and can be directly recycled in a single step.

　　Polyurethane leather is gradually replacing PVC artificial leather. As the first generation of synthetic leather, PVC artificial leather boasts characteristics such as a texture closely resembling natural leather, vibrant appearance, soft feel, and excellent resistance to abrasion, flexing, and acids and alkalis. Since its development in the 1970s, the industry has grown to a considerable scale; however, its poor breathability and moisture absorption have imposed certain limitations on its further growth in recent years. Today, wherever PVC is used, polyurethane can serve as a viable substitute. Polyurethane not only exhibits outstanding high strength and toughness but also demonstrates superior aging resistance, breathability, moisture permeability, water impermeability, and oil resistance, making it a well-established, environmentally friendly material.

　　FAW Group’s FAW Fu’ao Johnson Controls Co., Ltd. is a leading manufacturer in the automotive interior components industry, consuming more than 10,000 tonnes of polyurethane raw materials annually for soft components such as seats and instrument panels, with Changchun alone accounting for 4,000 tonnes. The company supplies over 100 varieties of soft components—including seats and instrument panels—to major automakers such as Jetta, Audi, Mazda, and Jiefang, consuming more than 3,000 tonnes of polyurethane raw materials each year.

　　The main technical challenges associated with polyurethane foams and products include: the storage stability of MDI, TDI, and additive blends; the resistance of products to damp-heat aging; and defects such as voids and cracking resulting from unstable foaming processes.

　　The primary development requirements for polyurethane foams and products include lightweighting, wide hardness ranges, low odor, low haze, aging resistance, storage stability, and environmental sustainability—such as the need to replace conventional blowing agents.