12 Engineering Plastic Injection Moulding Materials and Their Chemical Properties

Key Properties of Plastic Injection Moulding materials table

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These material are amazing choice for Plastic Injection Moulding but here are some other manufacturing processes where these materials are used.

Material selection is important but it is important to have the right auxiliary equipment for processing.

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1. Low Density Polyethylene (LDPE)

Polyethylene is the simplest hydrocarbon polymer in plastic injection moulding, derived from ethylene, which can be synthesized by the hydrogenation of acetylene or dehydration of ethanol. It is commonly produced from petroleum products via catalytic cracking.

Key Properties:

• Melting Point: 110-125°C

• Crystallinity: ~40%

• Density: 0.91-0.92 g/cc

• Chemical Resistance: Resistant to most solvents at room temperature; dissolves at high temperatures in solvents like toluene and trichloroethylene.

• Applications: Packaging films, squeeze bottles, irrigation pipes, electrical insulation.

  
  

At Plast Fab, LDPE was a go-to material for flexible packaging solutions. Its soft and pliable nature made it perfect for molding items like caps and protective covers. However, we always had to be mindful of its low-temperature resistance, which could lead to warping in high-heat conditions.

2. High Density Polyethylene (HDPE)

Chemically, it is more resistant than the low-density variety and has a significantly lower gas permeability when considered for plastic injection moulding.

Key Properties:

• Melting Point: 144-150°C

• Crystallinity: ~90%

• Density: Up to 0.965 g/cc

• Properties: Higher stiffness, tensile strength, and chemical resistance than LDPE.

• Applications: Toys, containers, pipes, high-strength applications.

In our manufacturing, HDPE was a beast. We used it for sturdy containers and industrial piping components. One challenge we faced was shrinkage during cooling, leading to occasional dimensional inconsistencies that required fine-tuned mold adjustments.

3. Polypropylene (PP)

Polypropylene is the lightest industrial polymer, synthesized through the polymerization of propylene using Ziegler-Natta catalysts.

Key Properties:

• Melting Point: Above 100°C

• High stiffness, hardness, and tensile strength

• Resistant to acids, alkalis, and oils but prone to oxidation

• Superior dielectric and mechanical properties

• Applications: Washing machine components, packaging films, pipes, storage tanks, monofilaments, and ropes.

Plast Fab saw extensive use of PP for storage containers. We found it excellent for impact resistance but had to be cautious about its low-temperature brittleness. A funny incident once had us testing a batch of PP buckets—only to find them cracking under extreme cold! Lesson learned: PP and freezing temperatures don’t mix.

3. Polystyrene (PS)

Polystyrene, also known as polyvinyl benzene, is an amorphous polymer with linear molecular chains.

Key Properties:

• Heat Distortion Temperature: 85°C (poor resistance to high temperatures)

• Chemical Resistance: Inert to acids, alkalis, oxidizers

• Weathering Issues: Prone to yellowing and crazing upon outdoor exposure

• Applications: Molded containers, television cabinets, toys, foamed plastics.

Copolymers:

• Styrene-Acrylonitrile (SAN): Higher impact strength, transparency, used in household and packaging items.

PS was a dream to mold but a nightmare for heat resistance. I recall a time when we experimented with PS-based casings for electronic devices—only to realize they deformed slightly under prolonged exposure to heat. Needless to say, we switched to ABS in those cases.

4. Polymethyl Methacrylate (PMMA)

PMMA is a transparent plastic with excellent weather resistance and optical clarity. One of the most commonly used materials for Plastic Injection Moulding

Key Properties:

• High resistance to chemicals (except ketones and chlorinated hydrocarbons)

• Good mechanical strength but poor scratch resistance

• Applications: Automotive lighting lenses, signboards, decorative panels.

Working with PMMA was like handling glass—except much more forgiving. We once crafted high-end transparent panels for industrial equipment, and they turned out stunningly clear. The only downside? Scratches! We had to add protective coatings to maintain the pristine look.

5. Polycarbonate (PC)

Polycarbonate is a high-strength, transparent plastic formed from Bisphenol A and diphenylcarbonate.

Key Properties:

• Melting Point: ~265°C

• High impact resistance

• Resistant to water and most organic compounds (hydrolyzed by alkalis)

• Applications: Safety goggles, machine housings, telephone parts.

PC was the king of toughness in our production. We used it for protective shields and industrial covers. However, during molding, we had to deal with its tendency to absorb moisture, leading to defects. The solution? A strict drying protocol before processing.

6. Acrylonitrile Butadiene Styrene (ABS)

ABS is a terpolymer made from acrylonitrile, butadiene, and styrene, combining rigidity, toughness, and chemical resistance.

Key Properties:

• Excellent impact resistance

• High tensile strength and dimensional stability

• Resistant to acids, alkalis, and oils

• Applications: Automotive parts, consumer electronics casings, helmets.

At Plast Fab, ABS was a favorite for rugged enclosures. One time, we had a batch of machine casings that came out slightly warped. The culprit? Uneven cooling rates. We learned that keeping mold temperatures consistent was key to getting that perfect finish.

7. Polysulfone (PSU)

Polysulfone is a high-performance engineering thermoplastic known for its excellent thermal stability and chemical resistance.

Key Properties:

• High heat resistance (service temperatures up to 180°C)

• Excellent hydrolytic stability, making it suitable for repeated steam sterilization

• High mechanical strength and transparency

• Applications: Medical devices, food processing equipment, aerospace components.

Polysulfone was our go-to material for high-temperature applications. We used it in precision-engineered parts where other plastics would fail under heat. However, the processing window was narrow, and improper temperature control could lead to brittleness. Our trick? A carefully monitored molding process with a pre-drying step to prevent moisture-related defects.

8. Polyamide (Nylon)

Polyamide (commonly known as Nylon) is a strong and versatile polymer used extensively in engineering applications.

Key Properties:

• High mechanical strength and toughness

• Excellent wear resistance and self-lubricating properties

• Resistant to most chemicals, except strong acids and bases

• Applications: Gears, bearings, automotive components, textiles.

At Plast Fab, Nylon was a reliable choice for producing industrial gears and bushings. We loved its strength and wear resistance, but its moisture absorption sometimes led to dimensional changes. To counter this, we implemented strict drying procedures before molding, ensuring optimal performance in end-use applications.

Also nylon is a great companion for insert molding.

9. Polyvinyl Chloride (PVC)

PVC is a widely used thermoplastic with excellent chemical resistance and versatility.

Key Properties:

• High chemical resistance, especially to acids and bases

• Good electrical insulation properties

• Can be rigid or flexible based on plasticizer content

• Applications: Pipes, medical tubing, vinyl flooring, window frames.

At Plast Fab, we used PVC extensively for piping and insulation. One major challenge was controlling the release of hydrogen chloride fumes during processing—requiring us to use proper ventilation and stabilizers to prevent degradation. The upside? It was an affordable and reliable workhorse for many of our projects.

10. Polytetrafluoroethylene (PTFE)

PTFE, commonly known as Teflon, is a fluoropolymer with exceptional chemical resistance and non-stick properties.

Key Properties:

• Melting Point: ~327°C

• Chemical Inertness: Highly resistant to acids, bases, and solvents

• Non-Stick Surface: Low friction coefficient, making it an ideal choice for anti-adhesive applications

• High-Temperature Resistance: Can withstand temperatures up to 260°C without degrading

• Applications: Seals, gaskets, bearings, non-stick coatings, electrical insulation

At Plast Fab, PTFE was our go-to material for specialized sealing components in harsh chemical environments. I remember once testing PTFE bushings in an industrial setting—no matter how much friction we subjected them to, they refused to wear out! The only challenge? Molding PTFE wasn’t straightforward. Unlike other thermoplastics, it required a sintering process instead of conventional injection molding, adding an extra layer of complexity to production. But once mastered, it became an invaluable material for high-performance applications.

11. Polybutadiene (PBT)

Polybutadiene (PBT) is a synthetic rubber with exceptional toughness, flexibility, and resistance to wear. It is primarily used in applications requiring high impact resistance and durability.

Key Properties:

• High Elasticity & Toughness: Excellent resilience, making it ideal for shock-absorbing applications.

• Wear and Abrasion Resistance: Outperforms many other polymers in high-friction environments.

• Low Glass Transition Temperature: Stays flexible even in sub-zero temperatures.

• Good Chemical Resistance: Withstands oils, greases, and various solvents.

• Applications: Tire treads, automotive parts, industrial belts, gaskets, and electrical insulation.

At Plast Fab, we once used PBT in high-wear conveyor belt components, and I remember being amazed at how well it handled friction. While most materials degraded over time, PBT kept going like a champ! The biggest challenge was its shrinkage rate, which required meticulous mold design to avoid dimensional inconsistencies. But once dialed in, it became one of our go-to materials for tough applications.

After reading about our experiences with various materials, you must be confident about our abilities. So, we are offering you a free quote. Click here to get a free quote today!

Also read about the 5 best Plastic Injection Moulding Companies in India.