In any project that involves injection molding, the number one priority is getting the materials right. The choice will determine the operation’s efficiency and the performance of the components. Loads of plastic material types to choose from. Which one is the best for your purposes?
Plastic selection depends on lots of factors, including the function and environmental impact of the material. You want the material to be as strong, durable, flexible, and color-friendly as possible. So here’s a list of the readily available plastics and their uses.
Acrylic
Acrylics are a lightweight and semi-transparent plastic material. You can see it used in windows, doors, lamps, walls, and more. It has a lot in common with glass. For example, it’s durable, weather-resistant, and transparent. It’s an affordable alternative to glass because it doesn’t shatter under pressure. The material also has other properties than transparency and lightweight.
In fridges and food storage containers, acrylic is commonly found as the material is odor-free and inert. It’s also BPA-free, Bisphenol A (BPA) is a harmful chemical that has a toxic reaction to food.
Acrylonitrile Butadiene Styrene (ABS)
As a weldable plastic material, ABS has a low melting point, but once it cools down it becomes incredibly rigid. ABS is highly resistant to impact, electricity, and abrasion.
You can use it to build fan blades, vacuum cleaners, and various electronics. Laboratory test tubes also use ABS. Since it’s easy to install, doesn’t rot, and resists corrosion, ABS is used in making pipes and fittings.
Nylon (Polyamide)
Polyamide is a common chemical compound used to manufacture mechanical parts such as linings, nuts and bolts, and bearings. This compound is strong, hard, and resistant to chemical wear and tear. The chemical designation of nylon is PA (Polyamide).
Poly carbonate
This plastic has exceptional optical features. It’s the clearest plastic available that allows you to maintain complete dimensional control. Thanks to its uniformity and predictability properties, it’s much easier to mold. Poly carbonate is used whenever you need something harsher than acrylic. Unfortunately, poly carbonate isn’t safe for water bottles and food packaging. Since it has 95% BPA, which creates toxic reactions with organic material.
Polyethylene (PE)
Plastic polymer polyethylene is lightweight and resists chemicals, is pliable, and has electricity-proof features. Even though this material isn’t particularly strong or durable, it still makes up a wide range of consumer plastics, such as motor oil and medicine containers, paper bags, and trash and grocery bags. The most popular type of injection-molded plastic for toys is polyethylene.
Polyoxymethylene (POM)
The engineering thermoplastic polyoxymethylene is used for parts designed to be metal-based, such as mechanical and automotive components. It is extremely strong, sturdy, and rugged.
Despite its exceptional resistance to solvents such as diesel, fuels, disinfectants, and engine oils, you should avoid mixing polyoxymethylene with oxidizing agents, bases, and acids.
Polypropylene (PP)
Food packaging is made with polypropylene, a type of thermoplastic that keeps chemicals from reacting to food. It’s also safe to clean it with hot water without worrying about damage. You can also use it to store a variety of chemicals thanks to its chemical-resistant material. Polypropylene is highly impact-resistant, elastic, and tough.
Polystyrene (PS)
Polystyrene has several types depending on its uses. You have polystyrene foam, regular polystyrene plastic, and polystyrene film. Polystyrene foam has different types such as polystyrene (EPS) and extruded polystyrene (XPS). The most common type of polystyrene is the EPS, which is used in insulating walls, floors, and roofs.
As a firm, thick plastic, it is frequently used in transparent items, such as food boxes and laboratory glassware. You can also combine it with other plastics and materials to make tools, gadgets, automotive components, landscaping items, accessories, and much more.
Thermoplastic Polyurethane (TPU)
A soft polyurethane (TPU) with high flexibility and tear strengths is primarily used in producing parts that need to be elastic and stretchy. TPU is widely used in inflatable rafts, medical devices, and sporting apparel.
Thermoplastic Rubber (TPR)
Thermoplastic rubber is a widely used injection molding material. TPR has both rubber-like properties and plastic properties. It is strong and lightweight and contains properties of both plastic and rubber. It is commonly found in suspension bushings, medical equipment, and electronic cables.
Where To Start Choosing The Right Injection Molding Material?
Imagine the finished product and start working backward. A few good starting questions could be: What will the part be used for? How much stress will it endure? Where will the part be located? The following criteria can help you choose your material:
- The part must always be considered, whether it will live inside, outdoors, in direct sunlight or damp conditions, or somewhere else entirely.
- Choosing the right material for your product depends on the temperature. Will it be shipped to a freezer, or somewhere very hot or cold?
- When is a part expected to expire? Do you plan to use it for five years, fifteen, twenty-five, etc?
- In the automotive industry, in particular, you need to consider the warranty. It may break years from now. How much will it cost to cover the warranty?
- Choosing the right material may require you to choose between two types of materials. You could select a standard plastic (such as high-density polyethylene or polypropylene), which is well-known and more commonly available, and relatively inexpensive. The second type of plastic is engineered plastic, including materials such as PEEK and PEI. These are difficult to find and extremely expensive, but stiff and very high-temperature resistant.
- If your part needs to match another part in an assembly, it may be required to be transparent, or a specific color. The finish standards provided by SPI cover a range of treatments you may specify for your parts, ranging from optically-polished SPI-A1 to coarse matte SPI-D3. Mold texture techniques, such as those outlined by MoltTech, are another possibility for cosmetic faces.
Injection Molding Material FAQ
Q: Which raw material is the most commonly used for injection molding?
A: A standard among mold makers and much more common than ABS is Acrylonitrile Butadiene Styrene (ABS). ABS plastic molding is often used in the plastic industry.
Q: Is it possible to inject PVC into a mold?
A: The chemical chlorine in polyvinyl chloride makes the process of injecting it more difficult than with other plastics. Melted PVC releases a toxic gas which makes it more difficult to inject.
Q: Which plastic material should I choose?
A: You need to think about several factors when choosing plastics. Among the most important ones are cost, durability, surface finish, strength, and flexibility. You also need to consider how and where the plastic part will be used.
Q: Which plastic is the strongest in the world?
A: Unlike glass, polycarbonate is stronger and is guaranteed against breakage or cracks. It is the strongest plastic.
Q: Is POM plastic safe?
A: You can use a food-grade polymer called polyoxymethylene copolymer (POM) that is FDA and USDA-approved. However, not all plastics are endocrine disruptors and many are safe for food contact applications.