Injection molding is one of the most trusted manufacturing methods in the world—and for good reason. It allows companies to produce plastic parts at scale with consistent quality, repeatable dimensions, and a clean finish that works for everything from household products to automotive components and medical devices.
But here’s the truth many businesses learn after their first few projects: injection molding success depends heavily on choosing the right plastic material. The mold may be perfectly engineered, and the machine settings might be dialed in—but if the plastic resin doesn’t match the job, you’ll run into problems like cracking, warping, poor surface quality, or parts that simply don’t perform in real life.
That’s why experienced engineers and production teams spend a lot of time selecting the best resin before a project ever goes into production. Whether you’re working with a local supplier or sourcing from plastic manufacturers in Thailand, the resin choice will directly affect durability, appearance, flexibility, heat resistance, and cost.
In this guide, we’ll break down the top 10 most common plastic materials used in injection molding, what they’re best for, and how to choose the right one for your product. We’ll also touch on how some of these plastics are used in plastic thermoforming and why partnering with a reliable plastic injection molding factory matters.
Why Material Selection Matters in Injection Molding
Injection molding works by melting plastic pellets (resin), injecting the molten material into a mold cavity, and letting it cool into a finished part. The process sounds straightforward—but the performance of the final product depends on the material’s properties such as:
- Strength and stiffness
- Impact resistance
- Flexibility
- Heat resistance
- Chemical resistance
- UV resistance
- Shrinkage behavior
- Surface finish quality
- Cost and availability
Some plastics mold beautifully but don’t handle heat well. Others are extremely strong but can be more expensive. Some are ideal for outdoor use, while others break down under UV exposure. Your job is to match the plastic to the real-world conditions your part will face.
A professional plastic injection molding factory will usually help guide you through this decision—but it still helps to understand the basics so you can make confident choices.
Top 10 Common Plastic Materials Used in Injection Molding
Let’s dive into the most widely used injection molding plastics and where they perform best.
1. Polypropylene (PP)
Polypropylene is one of the most common plastics used in injection molding worldwide. It’s lightweight, flexible, and offers excellent chemical resistance, making it a go-to material for many everyday products.
Key Benefits
- High chemical resistance
- Flexible and fatigue-resistant (great for living hinges)
- Lightweight and cost-effective
- Good moisture resistance
Common Uses
- Food containers and packaging
- Bottle caps and closures
- Automotive interior parts
- Medical containers and lab supplies
- Storage bins and household products
PP is also commonly used by plastic manufacturers in Thailand due to its affordability and wide availability. It’s an excellent choice for high-volume products where cost matters but durability is still important.
2. Acrylonitrile Butadiene Styrene (ABS)
ABS is known for its toughness and clean appearance. It molds well, holds shape, and provides a solid, slightly glossy finish that looks professional.
Key Benefits
- High impact strength
- Good surface finish
- Strong and rigid
- Easy to machine and paint
Common Uses
- Electronics housings
- Appliance components
- Automotive trims
- Toys (including building block-style products)
- Consumer product casings
ABS is a favorite when you need a part that looks good and can handle regular use. It’s commonly offered by any established plastic injection molding factory because it performs consistently.
3. Polyethylene (PE) – HDPE & LDPE
Polyethylene comes in two popular forms:
- HDPE (High-Density Polyethylene) – stronger and more rigid
- LDPE (Low-Density Polyethylene) – softer and more flexible
Key Benefits
- Excellent moisture resistance
- Good chemical resistance
- Durable and lightweight
- Low cost
Common Uses
- Bottles and containers
- Household product parts
- Industrial caps and covers
- Pipes and fittings (especially HDPE)
While PE is more famous in packaging, it’s also widely used in injection molding for functional components. Some PE sheets are also used in plastic thermoforming, especially for protective covers and containers.
4. Polycarbonate (PC)
Polycarbonate is a high-performance plastic known for being extremely tough and impact resistant. It’s often used when strength and clarity are required.
Key Benefits
- High impact strength (very tough)
- Heat resistant
- Can be transparent
- Strong dimensional stability
Common Uses
- Safety glasses and protective shields
- Clear machine guards
- Medical device housings
- Lighting components
- Automotive headlamp lenses
PC is a great option for products that need durability and clarity. It’s not always the cheapest resin, but it delivers premium performance.
5. Nylon (Polyamide – PA6 / PA66)
Nylon is widely used for mechanical parts because it offers excellent wear resistance and strength. It’s often chosen for moving parts or components that face friction.
Key Benefits
- Strong and durable
- Excellent wear resistance
- Good heat resistance
- Works well for mechanical applications
Common Uses
- Gears and bearings
- Cable ties
- Automotive under-hood components
- Industrial machine parts
- Tool housings
Nylon is a strong choice, but it does absorb moisture over time, which can affect dimensions. A good plastic injection molding factory will account for this in design and tolerances.
6. Polystyrene (PS)
Polystyrene is known for being easy to mold and cost-effective. It’s often used in products that don’t require high impact resistance.
Key Benefits
- Low cost
- Good rigidity (in general-purpose form)
- Easy to mold
- Clear versions available
Common Uses
- Disposable cutlery and containers
- Cosmetic packaging
- Lab trays
- Display components
Polystyrene is also commonly used in plastic thermoforming, especially for trays and packaging inserts.
7. High Impact Polystyrene (HIPS)
HIPS is basically a tougher version of polystyrene. It includes rubber additives to improve impact resistance, making it more suitable for everyday products.
Key Benefits
- Better impact resistance than standard PS
- Easy to mold
- Good surface finish
- Cost-effective
Common Uses
- Refrigerator liners
- Packaging inserts
- Point-of-sale displays
- Disposable products with more durability
HIPS is popular for both injection molding and thermoforming, which makes it useful for companies that use both processes.
8. Polyoxymethylene (POM / Acetal / Delrin)
POM is one of the best plastics for precision parts. It has a smooth surface, low friction, and excellent dimensional stability.
Key Benefits
- Very low friction
- High stiffness and strength
- Great dimensional stability
- Excellent wear resistance
Common Uses
- Gears
- Clips and fasteners
- Pump components
- Precision mechanical parts
POM is widely used in industrial and automotive applications. If you’re producing functional parts that must move smoothly, POM is a top-tier option.
9. Thermoplastic Elastomers (TPE / TPU)
TPE and TPU are flexible, rubber-like materials used when you need soft-touch surfaces or parts that bend and compress.
Key Benefits
- Flexible and soft
- Good grip and comfort
- Durable and elastic
- Can be overmolded on rigid plastics
Common Uses
- Handles and grips
- Seals and gaskets
- Protective covers
- Medical tubing components (depending on grade)
These materials are commonly used in multi-material injection molding. A capable plastic injection molding factory can combine TPE with ABS or PC to create premium products with comfort and durability.
10. Polyvinyl Chloride (PVC)
PVC is widely used in construction and medical applications due to its chemical resistance and durability. It can be rigid or flexible depending on additives.
Key Benefits
- Good chemical resistance
- Durable
- Cost-effective
- Available in rigid and flexible forms
Common Uses
- Pipe fittings
- Cable insulation
- Medical tubing (specific grades)
- Protective housings
PVC is not used in every injection molding project, but it’s common in industries where chemical resistance matters.
How to Choose the Right Plastic for Your Product
Choosing the right resin is not just a technical decision—it’s a business decision. The wrong material can increase defects, returns, and long-term costs.
Here are the top factors to consider:
1. Strength Requirements
Does your part need to handle pressure, weight, or impact?
ABS, PC, Nylon, and POM are strong options.
2. Flexibility Needs
If the part needs to bend, snap, or flex repeatedly, PP or TPE may be better.
3. Heat Resistance
If your product will be exposed to heat, consider PC, Nylon, or specific high-temperature resins.
4. Chemical Exposure
If the part touches cleaning chemicals, oils, or fluids, PP, PE, and PVC perform well.
5. Appearance and Surface Finish
If the product is consumer-facing, ABS and PC often deliver a cleaner finish.
6. Cost and Volume
For high-volume production, PP and PE are often the most economical.
A professional manufacturer will usually test and recommend options based on your product needs and budget.
Injection Molding vs Plastic Thermoforming: What’s the Difference?
Many businesses compare injection molding with plastic thermoforming, especially when launching new products.
Injection Molding
Best for:
- High-volume production
- Small to medium parts
- Complex details and precision
- Strong repeatability
Plastic Thermoforming
Best for:
- Large parts and trays
- Packaging inserts
- Lower tooling costs
- Faster prototype changes
Some companies use both processes together. For example:
- Injection molding for small functional parts
- Plastic thermoforming for packaging trays or covers
This is common in medical, electronics, and industrial product manufacturing.
Why Work With Plastic Manufacturers in Thailand?
Many global brands are increasingly sourcing from plastic manufacturers in Thailand because Thailand has become a strong hub for modern plastic production.
Benefits often include:
- Competitive production pricing
- Skilled engineering teams
- Advanced factory equipment
- Export-ready supply chain
- Experience with international clients
If you’re looking for both quality and scalability, Thailand is a region worth considering—especially if you need consistent resin sourcing and dependable lead times.
What to Expect From a Good Plastic Injection Molding Factory
A reliable plastic injection molding factory doesn’t just mold parts—they help you avoid expensive mistakes.
A good factory typically provides:
- Material recommendations and sourcing support
- Mold design guidance
- Prototype and sampling options
- Quality control checks and inspections
- Production consistency and repeatability
- Packaging and shipping support
If your project involves tight tolerances or customer-facing products, factory experience matters just as much as the material choice.
Final Thoughts: The Right Material Makes the Difference
Injection molding is one of the most efficient manufacturing methods available today—but it only works well when the right plastic material is selected.
The top 10 common plastic materials used in injection molding—including PP, ABS, PE, PC, Nylon, PS, HIPS, POM, TPE, and PVC—cover a wide range of applications. Each material has its strengths, and the best choice depends on your product’s function, environment, appearance, and cost targets.
Whether you’re sourcing parts locally or working with plastic manufacturers in Thailand, understanding material basics helps you make smarter decisions, reduce defects, and create products that perform reliably.
And if you’re deciding between injection molding and plastic thermoforming, remember: many successful products use both methods together. The key is choosing the right process—and the right partner—for the job.
