The Injection Molding Process is a mass manufacturing process used for producing parts or components by injecting molten plastic or rubber material into the mold cavity. Injection molding is the most popular plastic manufacturing technology and is utilised in practically every consumer plastic product. High-strength engineering polymers lower the cost of parts production, assembly, and maintenance while also making the vehicle lighter, more energy-efficient efficient, and environmentally friendly.

Here are the commonly used materials in injection molding of automotive components and their advantages/disadvantages that will help you select the material:

Polyethylene (PE)

Key features: Polyethylene offers strong impact resistance, a low density, and long service life. It can be utilized in a variety of thermoplastics processing procedures and is especially useful in situations where moisture resistance and cheap cost are required. There are three types of PE: polyethylene terephthalate (PET, PETE), low density (LDPE), and high density (HDPE, PEHD). While both HDPE and LDPE have beneficial features including chemical resistance, they differ in terms of flexibility, hardness, transparency, and melting point.

Advantages:

• Low-cost plastics

• Resistant to both moisture and chemicals

• High toughness and impact resistance

Disadvantages:

• Poor UV resistance

• Low dimensional stability

• Unable to withstand high service temperatures (> 125°C)

Applications: corrosion-resistant piping, glass-reinforced car bodywork, fuel tank, vent pipe, deflector, various storage tanks, and electrical insulation.

Polypropylene (PP)

Key features: Polypropylene (PP) is similar to Polyethylene (PE) in terms of characteristics; however, it is slightly tougher and more heat resistant. Also, it has strong electric insulation properties.

Advantages:

• Good Moisture Resistance & High melting point (160 °C)

• Variety of color pigments can be used & it can be recycled three to four times

• High flexibility with high fatigue resistance Chemical resistant to acids and bases

Disadvantages:

• Sensitive to UV exposure

• Poor adhesion with external paint/coatingsHighly flammable

Applications: bumpers, instrument panel housing, door trim panel, air conditioner parts, battery shell, cooling fan, chemical tanks, cable insulation, snap-over lids, gas cans, carpet fiber, and steering wheel.

Polycarbonate (PC)

Key features: Polycarbonate is an engineering-grade thermoplastic with outstanding performance and transparency. Toughness and high strength are the thermoplastic's major characteristics, which enable impact resistance and fracture resistance. Polycarbonate is also lightweight, so it reduces a vehicle’s overall weight.

Advantages:

• High strength and impact resistant

• Low shrinkageHigh melting point (155°C)

• Good dimensional stability & good heat resistance

Disadvantages

• Poor chemical resistanceVoids/bubbles and sink marks could result from sensitivity in thick sections of components.

• Transparency reduces and it turns yellow when exposed to sunlight for a prolonged duration.

Applications: automobile headlights, headlight lenses, bulletproof glass, helmets, clear windows, and glasses. It is the preferred material for automotive bumpers due to its exceptional impact strength.

Acrylonitrile Butadiene Styrene (ABS)

Key features: ABS is a low-cost plastic material with high strength and impact resistance. ABS resin is an opaque engineering-grade plastic. When exposed to fire, ABS is a good insulator and does not conduct electricity or emit gasses. During an impact, ABS helps the body absorb and redistribute energy, keeping passengers safe.

Advantages:

• Durable and lightweight

• High mechanical toughness

• Good dimensional stability

• Resists impacts and scratching,

• Lower cost than PC

• Improved processing because of low melting point

Disadvantages:

• Low resistance to UVLow resistance to moisture

• Generates smoke when burned

Applications: Steering wheel covers, adaptors, socket plastic guard, wheel covers, automotive covers, shrouds, and housings and dashboards parts.

ABS-PC

Key features: ABS-PC, or polycarbonate-acrylonitrile butadiene styrene, is an engineering thermoplastic that combines ABS and PC. ABS-PC plastic is one of the most extensively utilized engineering thermoplastics in the world due to its mechanical qualities.

Advantages:

• Higher Strength

• heat and low-temperature resistance

• Improved flow and process ability

Disadvantages:

• Poor solvent resistance

• Low continuous service temp

• Low dielectric strength

• Generates smoke when burnt

Applications: glove boxes, knee bolsters, overhead and middle consoles, enclosures, and blow-molded seatbacks.

Acrylic (PMMA - Polymethyl Methacrylate)

Key features: Acrylic is transparent and has excellent optical clarity therefore it is a lighter-weight, shatter-resistant alternative to glass. Acrylic can also be tinted to make it transparent or opaque.

Advantages:

• Good optical properties

• High scratch resistance

• High tensile strength

• High resistance to sunlight and moisture

• Does not release Bisphenol A (BPA), a hazardous chemical

• Fully recyclable

• Good dimensional stability

Disadvantages:

• Poor chemical resistance.

• Costs more than glass

• Poor wear and abrasion resistance

• Low impact resistance

• PMMA has a service temperature that is too low < 90 °C

• stress cracking under especially heavy loads

Applications: Interior and exterior panels, sunroofs, bumpers, fenders, and screens.

Polystyrene (PS)

Key features: Polystyrene is a polymer that is utilized in a wide range of plastic and foam applications in many industries. Electrical and chemical resistance are exceptional in polystyrene. It's simple to make, flexible, and softens when heated over its glass transition temperature. Strength, elongation, toughness, and impact strength are some of its mechanical qualities.

Advantages:

• High optical clarity

• High Stability

• Good electric insulator

• Inexpensive

• Recyclable

• Lightweight

• Resistant to moisture

• Resistant to bacterial growth

Disadvantages:

• Brittle and prone to cracking

• Poor UV resistance

• Susceptible to hydrocarbon solvents

• Flammable

• Not biodegradable

Applications: equipment housings, car fittings, display bases, and buttons.

Nylon (PA - Polyamides)

Key features: Nylon is a silk-like thermoplastic that may be melt-processed into fibers, films, or forms. It is primarily manufactured from petroleum. Nylon has high mechanical and wear-resistant properties. When a robust, low-cost stiff, and stable material is required, it is frequently utilized.

Advantages:

• High strength, abrasion resistance

• High-temperature tolerance when reinforced

• DurableHigh heat-resistant

Disadvantages:

• Absorbs water When wet, nylon swells and deteriorates quickly

• Poor UV resistance

Applications: wear pads, guide wheels, slide bearings gears, cams, bearings, and screws, under-hood components, waterproof coatings, high-wear parts, quick-release buckles, gears, and hand cranks.

Polyoxymethylene (POM) or Acetal

Key features: POM has excellent stiffness, yield strength, and cold temperature stability. It can be injection molded into products with low friction, high stiffness, and good dimensional stability.

Advantages:

• Excellent friction and wear resistance

• Long-term sliding characteristics, High forming fluidity, Good surface finish and luster (smooth, reflective properties)

• High Rigidity High Impact Resistance High Solvent Resistance

Disadvantages:

• Painting and coating it is difficult

• Very poor resistance to UV radiation

• Poor fire resistance as fire retardants cannot be incorporated into the polymer

Applications: Interior and exterior trims, fuel system parts, performance small gears, steering knuckle bushing, various bracket bushing, front and rear leaf spring bushing, brake bushing, door handles, seat belt mechanical components, and combination switches, rollers, bushings, wear strips, ball bearings, fasteners, lock systems, automotive ventilation, conveyor links, fan and blower blades, buttons, knobs, automotive cooling system parts fuel tank modules.

Thermoplastic elastomer (TPE)

Key features: TPEs are a class of rubber-like materials that combine the recyclability and processing advantages of plastics with the qualities of rubber. TPEs can be used for advanced processing including over-molding and two-shot molding, as well as secondary processes such as bonding with diverse materials.

Advantages:

• Part design flexibility Simple adhesion to different thermoplastic substrates can be recycled five-six times

• Less expensive to mold than liquid silicone rubber.

Disadvantages:

• Cannot withstand higher temperatures

• TPEs tend to creep after usage of prolonged duration.

Applications: Instrument panel components, buttons, encapsulation seals, cup holders, handles, gaskets, grip pads, bushings, and cables.

Thermoplastic Polyurethane (TPU)

Key features: TPU is a form of thermoplastic elastomer (TPE) that is typically mentioned individually due to its widespread use.

Advantages:

• High-temperature resistance

• Good load-bearing capabilities

• Good Moisture resistance

• High resistance to abrasion, chemicals, greases, and oils.

Disadvantages:

• TPU costs more Drying is required before processing

• Some TPU grades have a short shelf life

Applications: Gaskets, caster wheels, wheels, gears, drive belts, hose, and tubing.

Polyurethane (PUR)

Key features: Polyurethane, or PUR for short, is a thermoset plastic substance made by mixing two liquids and pressing them into a mold in a precisely calibrated reaction process. Solid polyurethane is an elastomeric material with outstanding physical qualities such as toughness, flexibility, abrasion, and temperature resistance.

Advantages:

• High toughness and flexibility

• High heat and abrasion resistance

• High resistance to moisture, UV radiation, and solvents

Disadvantages:

• Poor thermal capability

• Low moisture resistance

• Low resistance to solvents

• Utilize toxic isocyanates

• Flammable

Applications: foam insulation panels, flexible foam seating, elastomeric wheels and tires, electrical potting compounds, housings, enclosures, coverings, panels, doors, and functional structural parts, automotive suspension bushings, cushions, suspension bushings, and hard plastic parts.

Polyvinyl Chloride (PVC)

Key features: PVC, or polyvinyl chloride, is a common thermoplastic polymer. Naturally, it is white and brittle. PVC is cost-effective, resistant to environmental deterioration, chemicals, and alkalis, and has high tensile strength and hardness.

Advantages:

• Excellent flexibility

• Flame retardant

• Good thermal stability

• Little to no lead content

• High density

• High resistance to chemicals and alkalis

• Economical

• Recyclable

Disadvantages:

• When melted or burned, polyvinyl chloride generates hazardous gasses

• Poor thermal capability

• Poor weatherability

• Susceptible to most solvents

• Contents toxic isocyanates

• Flammable

Applications: door parts, dashboard, and electrical cable sheathing.

About Procurabl: Procurabl offers a full range of injection molding services to assist with your production needs.

Disclaimer:

The content appearing on this webpage is for informational purposes only. Procurabl makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Procurabl's Partner Network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.