With the rapid development of modern technology and the continuous advancement of new materials and processes, people today have set a series of higher requirements for the quality of automobiles, mainly in terms of comfort, safety, environmental friendliness, and aesthetics. Against this backdrop, the lightweight and low-cost design of automobiles has become the dominant trend in industrial design.
Automotive plastics offer numerous advantages over traditional materials. These advantages are primarily manifested in their lightweight properties, excellent aesthetic appeal, diverse practical applications, superior physical and chemical properties, ease of processing and forming, energy efficiency, and sustainability. The main characteristics of polymeric automotive materials are as follows:
Lightweight
Lightweight yet high-strength; only 15-20% of the density of ordinary steel, lighter than wood; significantly promoting automotive lightweight design.
Excellent processability
Excellent plasticity and good compatibility with other materials, enabling various shapes, properties, colors, and functions to be produced through multiple processing methods; secondary processing such as turning, punching, and cutting is also possible. Superior comprehensive physical and
Chemical properties
Excellent insulation properties, corrosion resistance, aging resistance, wear resistance, washability, waterproofing, mechanical properties, and adhesive
Bonding properties
Excellent decorative effects: Can be processed into products with complex shapes and multiple colors in a single step. Sometimes printing, film application, embossing, layering, and coloring are required to create highly realistic images, patterns, and designs. It can mimic the textures of natural wood, metal, and animal skin, and can also be surface-gilded, film-coated, silver-plated, or inlaid.
Energy-saving and environmentally friendly
Saves a significant amount of resources; excellent processability reduces energy consumption during production; widely used to replace natural materials, with scrap materials easily recyclable and directly reusable in remanufacturing.
There are many types of plastics, and their applications in automobiles can be divided into interior parts, exterior parts, and functional parts. This article will introduce the three major materials used for interior parts.
Ⅰ. PP
Polypropylene (PP) is a white, waxy material that is transparent, lightweight, and has excellent flow properties during injection molding. It has a low moisture absorption rate of less than 0.02%, is resistant to chemical organic solvents, and remains stable in many media except for concentrated nitric acid and concentrated sulfuric acid. It has high impact strength, good bending performance, is easy to form, has a high shrinkage rate, and is highly temperature-resistant. However, it becomes brittle at low temperatures and has low wear resistance. Since PP is a non-polar material, surface treatment is required during coating (e.g., flame treatment, primer application, etc.). The shrinkage rate of PP is 1.0–3.5%, and the suitable thickness is 1.5–2.5 mm.
The widespread use of PP in the automotive industry primarily faces two issues: flammability (which can cause burning droplets) and brittleness in low-temperature environments. To address these issues, appropriate additives are incorporated during industrial applications to modify PP. To address flammability, flame retardants are added; for brittleness in low-temperature environments, various modification techniques are employed to enhance toughness by incorporating other flexible materials, rigid particles, or elastomers, such as rubber (EPDM), talc (TD), and glass fiber (GF). Many automotive components are manufactured using PP resin, including instrument panels, door panels, pillar panels, bumpers, radiators, and decorative panels. The application of PP in the automotive industry is showing an increasing trend.
Ⅱ. PVC
Polyvinyl chloride (PVC) is a multi-component plastic. Due to variations in the content of its components, PVC particles exhibit significant differences in mechanical properties and hardness, generally categorized into two main types: soft PVC and hard PVC. Soft PVC is flexible, abrasion-resistant, has excellent bending elasticity, low water absorption, is easy to process and form, and possesses good low-temperature resistance and electrical insulation properties. It is resistant to acids and alkalis but not to organic solvents. PVC is flame-retardant, and the flame extinguishes immediately upon removal from the heat source. Rigid PVC has higher mechanical strength, with surface hardness, tensile strength, and rigidity exceeding those of PE and approaching those of ABS. It can be used as an engineering material but has a limited operating temperature range (-15°C to +55°C). Shrinkage rate: 1-1.5% for rigid PVC and 2-2.3% for soft PVC. The suitable thickness is 2-3.5 mm.
Among plastic materials used in automotive plastic products, polyvinyl chloride (PVC) is the most commonly used raw material. Automotive plastic products made from PVC are ubiquitous, including PVC instrument panel covers, PVC steering wheels, PVC trim panels, and PVC automotive flooring materials. This is not only because PVC resin is cost-effective but also because it offers good processing performance and comprehensive mechanical properties.
Ⅲ. ABS
Acrylonitrile-butadiene-styrene copolymer, which is white in color, combines the excellent properties of acrylonitrile (chemical corrosion resistance, surface hardness), butadiene (toughness), and styrene (good processability, good dyeability, poor weather resistance, prone to oxidation). It exhibits high impact toughness, excellent mechanical properties, superior heat and oil resistance, chemical stability, dimensional stability, ease of machining, surface electroplating capability, and good electrical properties. However, ABS has a relatively low heat deflection temperature, is flammable, has poor weather resistance, and is prone to discoloration and brittleness under sunlight exposure. The shrinkage rate is 0.4–0.7%, and the suitable wall thickness is 1.8–3 mm.
Due to its wide variety, excellent surface treatment effects, and low price, ABS is widely used in the automotive field. However, given the poor weather resistance of ABS, high weather-resistant PVC/ABS alloys, TPU/ABS alloys, and other materials are now widely used in commercial vehicles to replace ABS. Typical automotive products include instrument panels, armrest boxes, double-decker bus bunks, vehicle interior walls, and ceiling assembly components.