Injection molding is a widely utilized technique for manufacturing thermoplastic materials. The selection of the right material can be challenging given the numerous options available for injection molding plastics. Thermoplastics are plastic polymers that can be melted, reshaped, and refrozen, allowing for recycling and reuse.
In this comprehensive guide, we will talk about some of the most commonly used injection molding plastics. We provide insights into their properties, advantages, and properties to help you choose the ideal injection molding material for your specific applications.
Common Materials for Plastic Injection Molding
Acrylic Poly (Methyl Methacrylate) (PMMA)
Acrylic, or PMMA, is a lightweight plastic often used as an alternative to glass. It finds applications in windows, lenses, and rear lights due to its weather resistance, high gloss, and abrasion resistance. However, it has limited heat resistance and can be prone to cracking under pressure.
Advantages of Acrylic:
- Exceptional Transparency
- Weather and Chemical Resistance
- Surface Hardness
- Dimensional Stability
Applications: Windows, greenhouses, solar panels, bathroom enclosures, and architectural, lighting, and outdoor components
Polycarbonate (PC)
Polycarbonate is a strong, transparent plastic commonly used in engineering applications, such as compact discs, safety helmets, and bulletproof glass. It offers high impact resistance and UV resistance but may turn yellow over time with prolonged UV exposure.
Advantages of Polycarbonate:
- High Impact Resistance
- UV Resistance
- Transparency
- Chemical Resistance
- Rigidity
Applications: Machinery guards, clear and tinted windows, LED light diffusers, and clear molds for casting. Not recommended for food preparation or storage due to the presence of bisphenol A (BPA).
Acrylonitrile Butadiene Styrene (ABS)
ABS is a thermoplastic used in pipes, automotive parts, and keyboards. It combines high impact resistance with heat resistance and lightweight properties. However, it is prone to scratching and can have environmental concerns.
Advantages of ABS:
- Impact Resistance
- Surface Hardness
- Chemical Resistance
- Uniform Shrinkage
- Wide Temperature Range
Applications: Keyboard keys, protective headgear, automotive parts, consumer goods, sports equipment, and industrial fittings.
Polypropylene (PP)
Polypropylene is widely used in food storage and packaging due to its chemical resistance and moisture resistance. It also boasts high-impact strength. However, it degrades when exposed to UV light and can be flammable.
Advantages of Polypropylene:
- Chemical Resistance
- Fatigue Resistance
- Electrical Resistance
- Elasticity
Applications: Toys, storage containers, sporting goods, packaging, appliances, and power tool bodies.
Nylon
Nylon, a versatile plastic, is used in apparel, car tires, fishnets, and electrical applications like insulators. It offers good abrasion resistance but can be sensitive to moisture and heat.
Advantages of Nylon:
- Low Friction
- Chemical Resistance
- Abrasion Resistance
- Adaptability
Applications: Mechanical parts, casings, threaded inserts, and high-friction applications.
High-Density Polyethylene (HDPE)
High-density polyethylene is a resilient, solid plastic thermoplastic mainly used in plastic bottles, shampoo bottles, toys, recycling bins, and flower pots. It’s affordable and has high strength but is highly flammable and non-biodegradable.
Advantages of HDPE:
- Sustainability
- Chemical and Heat Resistance
- Food Grade
- Inexpensive
Applications: Housewares, toys, food containers, and automotive parts. Limited UV resistance, suitable for indoor applications.
Low-Density Polyethylene (LDPE)
Low-density polyethylene is softer and more flexible than HDPE, used in bottles, plastic bags, and playground equipment. It offers moisture and chemical resistance but is flammable and less heat-resistant.
Advantages of LDPE:
- Flexibility
- Moisture Resistance
- Impact Resistance
- Chemical Resistance
Applications: Containers, dispensing bottles, tubing, plastic bags, and molded laboratory equipment.
Polyoxymethylene (POM)
POM, also known as acetal, is a tough material used in automotive parts, zippers, and handles. It boasts a high-gloss surface and resistance to chemicals but may not bond easily and can be vulnerable to UV.
Advantages of Polyoxymethylene:
- Rigidity
- Impact Resistance
- Solvent Resistance
- Glossy Surface
Applications: Bearings, gears, conveyor belts, fasteners, eyeglass frames, and high-performance engineering components.
Thermoplastic Polyurethane (TPU)
TPU combines elasticity, transparency, and resistance, used in mobile phone cases, keyboard protectors, and footwear. It’s tough, flexible, and resistant to impacts, grease, and oil.
Advantages of Thermoplastic Polyurethane
- Elasticity
- Resistance to Impacts
- Dimensional Stability
- Resistance to Tears
- Resistance to Grease and Oil
Applications: Footwear, gaskets, caster wheels, electronics enclosures, and medical devices.
Thermoplastic Elastomer (TPE)
TPE blends plastic and rubber properties, offering versatility, resistance, and eco-friendliness. It can be stretched and returned to its original shape upon stress removal.
Advantages of Thermoplastic Elastomer:
- Versatility
- Resistance
- Consistency
- Eco-friendly
- Safe for the medical and food & beverage industries
Applications: Footwear, medical devices, auto parts, and pet products, including weather seals and shock dust boots in automotive and medical applications.
Plastic Prototype Materials Comprehensive Guide
Plastic Manufacturing Processes – Comprehensive Guide
Property Chart of Injection Molding Materials
| Material | Max Temp | Tensile strength | Flexibility | Impact Strength | Cost (low to high) |
| Acrylic (PMMA) | 130â | 8000 psi | low | low | medium |
| Polycarbonate (PC) | 288 â 316â | 9500 psi | high | high | high |
| Acrylonitrile Butadiene Styrene (ABS) | 60 â 93â | 5900 psi | high | high | medium |
| Polypropylene (PP) | 65 â 148â | 4800 psi | high | medium | low |
| Nylon Polyamide (PA) | 93 â 177â | 12400 psi | high | high | high |
| High-Density Polyethylene (HDPE) | 120â | 3,200 â 4,500 psi | low | high | medium |
| Low-Density Polyethylene (LDPE) | 65 â 90â | 1,200 â 4,000 psi | medium | high | low |
| Polyoxymethylene (POM) | 180 â 230â | 6,000 â 22,000 psi | medium | high | high |
| Thermoplastic Polyurethane (TPU) | 71-121â | 4060 â 13900 psi | high | high | medium |
| Thermoplastic Elastomer (TPE) | 71-121â | 290 â 8200 psi | high | high | high |
How to Choose Material for Your Plastic Injection Molding Project
Selecting the ideal material for your plastic injection molding project can be a challenging task, especially in the diverse world of injection molding. To simplify this process, we offer a concise and comprehensive material selection guide. While it may not provide a definitive answer, it will help you narrow down your material choices to a manageable selection.
- Material Hardness: Hardness is a critical attribute that often cannot be compromised. Nylon grades excel in applications requiring hardness, while for top-tier performance, consider Thermoplastic Polyurethane (TPU). Keep in mind that TPU can be costlier both in material and molding.
- Flexibility: Many injection molding materials offer flexibility. Thermoplastic elastomers and Polypropylene are well-suited for applications demanding flexibility. Thermoplastic elastomers tend to exhibit superior fatigue resistance and handle high temperatures, whereas Polypropylene is known for its recyclability and safety.
- Cost: When it comes to material costs, Polypropylene (PP) and Polystyrene (PS) often emerge as cost-effective options. They are both affordable and readily accessible.
- Temperature Resistance: For applications involving high temperatures, Nylon and Acrylonitrile Butadiene Styrene (ABS) shine, maintaining their structural integrity and material properties. Polyoxymethylene (POM) demonstrates remarkable stability in sub-zero temperatures.
Conclusion
Given the multitude of choices, it helps to have an expertâs advice before choosing a plastic resin for your project. KUSLA stands ready with a team of design and production experts who can guide you through the selection process. Moreover, you’ll receive invaluable design for manufacturing (DFM) feedback alongside your project quote.
KUSLA provides low-cost and High-quality injection molding services with different types of materials and final products. Plus, we provide 100%-part inspection support. Contact us today for a quick quote and design feedback.
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