11 Common Plastic Injection Molding Materials

Plastic injection molding is one of the most popular manufacturing processes found in most industries, ranging from the automobile, electronics, medical appliances, consumer goods, and packaging industries. Material choice is a key consideration that determines product performance, cost, and reliability, it cannot be ignored! Here we present some of the most common plastics used for plastic injection molding and provide other valuable information to assist you in choosing an optimum material for your application.

Part 1. What Type of Plastic is Used in Injection Molding?

Where injection molding is involved, a good choice of plastic is essential for achieving the desired synergy of performance, strength, price, and aesthetics. Different plastics have varied properties such as strength, flexibility, transparency, chemical resistance, and thermal stability that make them well suited for use in particular applications. In this article, we present the most widely used injection molding plastics.

1. ABS (Acrylonitrile Butadiene Styrene)

ABS is a terpolymer of three monomers butadiene, styrene and acrylonitrile. Each brings some characteristics, acrylonitrile provides thermal stability and chemical resistance and butadiene provides toughness and impact strength; finally, styrene provides smooth finish rigidity and rigid surface finish rigidity.

Mechanical Properties:

  • lHigh tensile strength and rigidity
  • lGood impact resistance, even at low temperatures
  • lGood dimensional stability
  • lModerate chemical and heat resistance

Processing Characteristics

ABS can be easily molded and offers high-quality surface finishes, hence it is suitable for painting, plating, and adhesive bonding. It is UV sensitive except when stabilized with additives.

Advantages & Disadvantages:

✅ Hard, strong, and versatile

✅ Excellent surface finish (can be painted or plated)

❌ Poor weather and UV resistance in the absence of stabilizers

❌ Poor resistance to heavy solvents

Applications:

Automotive interior trim, dashboard components, appliance enclosures, toys (LEGO bricks), electronic enclosures, and head protection.

abs materials of injection molding

2. PP (Polypropylene)

Polypropylene is a semi-crystalline thermoplastic that is manufactured by the polymerization of propylene monomers. It exhibits high resistance to most solvents, acids, and bases.

Mechanical Properties:

  • Low density and weight
  • High flexural endurance against fatigue (living hinges)
  • Good chemical resistance
  • Moderate tensile strength
  • Impact strength comparatively low compared to ABS or PC

Processing Characteristics:

PP is easy to process with little shrinkage, but can warp in complex mold shapes. It has better flow characteristics, with which it can be used to produce thin-wall components. Food contact grades are available due to its non-toxicity.

Advantages & Disadvantages:

✅ Light in weight and cost-effective

✅ Chemical-, fatigue-, and moisture-resistant

✅ Medical- and food-safe

❌ Bad UV stability unless modified

❌ Brittle at low temperatures

Applications

Food packaging containers, medical syringes, home storage boxes, car battery covers, apparel, and refillable water bottles.

3. PC (Polycarbonate)

Polycarbonate is an amorphous thermoplastic made from bisphenol A (BPA) and phosgene. It contains carbonate groups in its chemical makeup, which make it strong and transparent.

Mechanical Properties:

  • Great impact resistance (nearly unbreakable)
  • Great optical clarity and translucence
  • Good dimensional stability
  • Heat resistance up to 135°C (275°F)
  • Flame resistance when modified with additives

Processing Characteristics

PC must be dried with care before molding since it is sensitive to moisture. It is possible to shape very fine details with it but requires fairly high processing temperatures.

Advantages & Disadvantages:

✅ Hard, clear, and heat resistant

✅ Excellent electrical insulation characteristics

✅ Adequate to substitute for glass in the majority of applications

❌ More expensive than commodity plastics

❌ Susceptible to scratching and chemical attack (e.g., by solvents)

Applications

Optical lenses, protective goggles, car light housings, compact discs, medical equipment, protective shields, and bullet-resistant windows.

pc materials of injection molding

4. PA (Polyamide, Nylon)

Nylon is a family of synthetic polymer plastics with amide linkages (-CONH-). Common grades are PA6 and PA66, with slightly different mechanical and heat properties.

Mechanical Properties:

  • High tensile strength and impact toughness
  • Good wear and abrasion resistance
  • Self-lubricating with low coefficient of friction
  • Good thermal resistance (melting point ~220°C for PA66)
  • Moisture-absorbing, which can affect dimensions

Processing Characteristics:

Must be properly dried before molding to avoid hydrolytic degradation. Shrinkage needs to be considered, especially in glass-fiber-reinforced grades.

Advantages & Disadvantages:

✅ High strength, wear-resistant, and durable

✅ Suitable for high-load mechanical parts

✅ Can be glass fiber-reinforced for stiffness

❌ Water-absorbing, leading to dimensional instability

❌ Decreased UV stability without stabilizers

Applications:

Gears, bearings, bushings, under-hood automotive parts, electrical connectors, and industrial fasteners.

5. PS (Polystyrene)

Polystyrene is an amorphous thermoplastic that results from styrene monomers. It is available as general-purpose PS (GPPS) and high-impact PS (HIPS).

Mechanical Properties:

  • Light and rigid
  • Good dimensional stability
  • Transparent in GPPS, opaque in HIPS
  • Poor impact resistance (except for HIPS grades)

Processing Characteristics:

Readily processed and cheap but extremely prone to brittleness. Expanded PS (EPS) is expanded into foam for application in insulation and packaging.

Advantages & Disadvantages:

✅ Cheap and easily moldable

✅ Excellent transparency (GPPS) or shock resistance (HIPS)

✅ Highly available

❌ Brittle and crack-prone

❌ Poor heat and solvent resistance

Applications:

Packaging boxes, disposable cutlery, laboratory equipment, insulation boards, and protective packing foam.

ps materials of injection molding

6. POM (Polyoxymethylene, Acetal)

POM is a half-crystalline formaldehyde polymer. It is manufactured in homopolymer and copolymer grades.

Mechanical Properties:

  • Highly stiff and strong
  • Low wear and high friction
  • Strong creep resistance
  • High fatigue endurance
  • Working temperature up to 100–120°C

Processing Characteristics:

Easily machined with good dimensional stability, but sensitive to strong acids and oxidizers. Requires proper mold design to minimize shrinkage.

Advantages & Disadvantages:

✅ Excellent metal replacement in precision parts

✅ Low friction and low surface finish

✅ Excellent dimensional stability

❌ Poor chemical resistance (bases, acids)

❌ No effective UV resistance outside

Applications:

Precision gears, bearings, automotive fuel system parts, conveyor belts, zippers, and electrical insulators.

7. PMMA (Polymethyl Methacrylate, Acrylic)

PMMA is a transparent thermoplastic that is derived from methyl methacrylate. It is also called acrylic or Plexiglas.

Mechanical Properties:

  • Excellent optical clarity (92% light transmission, better than glass)
  • Good rigidity and hardness
  • Poor impact resistance (worse than PC)
  • Excellent weather and UV resistance

Processing Characteristics:

Simple to polish and mold, and therefore highly appropriate for transparent parts. Brittle, though, unlike PC.

Advantages & Disadvantages:

✅ High surface gloss and transparent

✅ Weather and UV resistant

✅ Lighter weight than glass

❌ Lower impact resistance than PC

❌ Stress cracking susceptible

Applications:

Light covers, displays, aquariums, protective screens, car tail lights, and advertisement signboards.

pmma materials of injection molding

8. PET (Polyethylene Terephthalate)

PET is a semi-crystalline thermoplastic polyester, which is made of terephthalic acid and ethylene glycol.

Mechanical Properties:

  • High tensile strength
  • Good dimensional stability
  • Good chemical and moisture resistance
  • Heat-resistant grades are available for engineering applications

Processing Characteristics:

Requires drying before processing. Mouldable into clear or opaque products. Recyclable (PET bottles are widely recycled).

Advantages & Disadvantages:

✅ Stable, strong, and recyclable

✅ Excellent barrier properties for gases and water

✅ Wide range of processing window

❌ Hydrolysis sensitive when moulding

❌ Brittle when not modified

Applications:

Bottle drink containers, food packaging, automobile components, textiles (polyester fibres), and electrical enclosures.

9. PE (Polyethylene – HDPE & LDPE)

PE is a low-cost hydrocarbon polymer of different grades of density. HDPE is extremely crystalline, while LDPE is branched.

Mechanical Properties:

  • Low weight with high impact strength
  • Good chemical and moisture resistance
  • LDPE: flexible, low strength
  • HDPE: rigid, stronger than LDPE

Processing Characteristics:

Easy to mold and extrude, widely available at cheap prices. Food-grade variants are common.

Advantages & Disadvantages:

✅ Food contact safe, non-toxic

✅ Chemical and moisture resistant

✅ Flexible (LDPE) or rigid (HDPE) nature

❌ Poor high-temperature resistance

❌ Limited bonding/painting ability

Applications:

Bottles, containers, pipes, toys, films, and cable insulation.

pe materials of injection molding

10. PVC (Polyvinyl Chloride)

PVC is an all-purpose thermoplastic polymer composed of vinyl chloride monomers. Available in rigid (uPVC) and flexible (with plasticizers) forms.

Mechanical Properties:

  • Robust and strong
  • Natural fire retardance
  • Chemical resistance is good
  • Rigid in rigid form, flexible with addition

Processing Characteristics:

Can be readily molded and extruded. Plasticizers and stabilizers are occasionally introduced to alter properties.

Advantages & Disadvantages

✅ Low cost and versatile

✅ Excellent chemical and weather resistance

✅ Flame retardant with no additives

❌ Environmental concerns with additives (phthalates)

❌ Emits toxic fumes during burning

Applications:

Pipes, building sections, window frames, flooring, cables, and medical tubing.

11. PEEK (Polyether Ether Ketone)

PEEK is a high-performance semicrystalline thermoplastic of the polyaryletherketone family. It is highly noted for excellent thermal and chemical resistance.

Mechanical Characteristics:

  • High mechanical strength and stiffness
  • Excellent fatigue and wear resistance
  • Maintains properties to temperatures of 250°C
  • Resistant to radiation and harsh chemicals

Processing Characteristics:

Requires high processing temperatures (350°C+). More expensive than regular plastics, but its performance is well worth it for rigorous applications.

Advantages & Disadvantages:

✅ Excellent heat, chemical, and wear resistance

✅ Biocompatible for medical applications

✅ Substitutes metal in high-performance uses

❌ Very costly relative to regular plastics

❌ Requires specialized processing equipment

Applications

Aerospace components, medical devices, oil & gas parts, high-performance connectors, and motor vehicle transmission parts.

peek materials of injection molding

Part 2. Key Factors to Consider When Choosing Plastics for Injection Molding

When making the selection for an injection molding material, it is crucial that multiple properties be considered when making a choice. Proper evaluation will help ensure the final product meets performance and cost requirements effectively. Here are the main points of consideration:

Mechanical Properties

Plastic materials vary significantly in their strength, rigidity and toughness properties – which will determine their behavior under load or stress. Gears and structural parts would require high tensile strength and wear resistance while consumer goods would benefit from higher impact resistance and flexibility.

Heat Resistance

Many applications call for materials with heat-resistance that do not deform when subjected to intense temperatures, including engine parts for cars, electrical housing, and assembly components that use light assemblies. High melting points and heat stability plastics are perfect for these uses.

Chemical Stability

Plastics that come into contact with oils, solvents, acids or alkalis must be chemically stable in order to remain functional in environments hostile to them – like automotive fuel system containers and cleaning fluids – for instance require materials like PP or POM that will keep their integrity when exposed to aggressive fluids such as acids or alkalis.

choose materials for injection molding

Cost Efficiency

Raw material price and processing costs directly affect the overall production budget. While engineering plastics such as PEEK deliver exceptional performance, they may not be economical for high-volume, everyday consumer products. Manufacturers must strike a balance between performance and cost.

Processability

Each plastic also possesses unique molding requirements, such as melting temperature, viscosity and shrink rate. Plastics with desirable flow characteristics (such as polypropylene or PBT ) will be most effective in thin-wall applications while high-performance plastics will require special equipment and more severe conditions under which to successfully mold.

Aesthetic and Surface Requirements

Attractive products require considerations such as transparency, gloss and customization in terms of color customization and optical clarity. PMMA and PC materials tend to perform well to realize such an effect; ABS offers improved surface finishes suitable for painting or plating operations.

Part 3. Applications of Plastic Injection Molding Materials

Plastic injection molding materials are widely used across industries because of their versatility, cost-effectiveness, and ability to meet specific technical requirements. Below are some key application areas:

Medical Industry

Plastics like PP, PC, and PVC find extensive usage in disposable medical devices and housing components. PP is preferred for syringes, containers, and labware on the basis of safety and chemical resistance. PC is utilized in those medical products that require strength along with transparency, like oxygen masks and diagnostic housings. PVC, with its flexibility along with sterilizability, gets used in IV containers, tubing, and catheters.

Consumer Electronics

Plastics such as ABS, PC, and PMMA are responsible for the production of strong, lightweight, and beautiful electronic devices. ABS finds application in impact resistance for phone casings, remote controls, and keyboards. PC finds widespread application in laptop casings and protective casings which require heat and shock resistance. PMMA, which offers optical clarity, is applied in display panels and light guides for monitors and screens.

Automotive Industry

The plastics such as ABS, PA, PP, and PC are used extensively for functional and cosmetic components. ABS is extensively utilized in dashboards, interior trim, and panels due to its impact and satisfactory surface finish. PA and POM are used for gears, bearings, and under-hood parts owing to their thermal stability and resistance to wear. PP is utilized for lightweight parts that have chemical resistance such as bumpers and battery covers, and PC for lighting circuits and transparent covers.

applications of injection molding

Packaging Industry

Plastics like PP, PET, and PS can be found everywhere in the packaging sector due to their safety, lightweight, and cost-effectiveness. PP is used in containers and closures for food, PET in bottles and food-packaging of the beverage type due to the fact that it is recyclable and transparent, and PS in disposable cups, trays, and protective packing foam.

Industrial Components

Performance plastics such as POM, PA, and PEEK play a vital role in the production of long-duration industrial parts. Low friction and stability of dimensions of POM make it suitable for precision gears and conveyor parts. PA is widely used in bearings, fasteners, and structural parts needing strength and wear resistance. While being costly, PEEK finds applications in aerospace, oil & gas, and heavy machinery where extreme resistance to chemicals and high-temperature tolerance are essential.

KENENG: Your Injection Molding Materials Expert Partner

The careful choice of plastic injection molding materials can result in a gigantic difference in the product quality, durability and competitiveness in the market. From common ones like ABS, PP and PC to high performance polymers like PEEK every material has a specific use and advantage. In making the selection of materials, the designer should consider product needs, processing conditions, cost constraint, and environmental protection targets so as to make the optimum decision.

With rich experience as a professional injection molding service enterprise, KENENG has a professional team and rich experience to offer a one-stop service from mold design and material selection to trial run and mass production. KENENG offers customized injection molding solutions according to customer requirements for consumer electronics, industrial parts and high-performance customized parts in the fields of maximum performance, quality and cost-effectiveness. Call them now to design an innovational product.