How to Choose the Right Plastic for Your Project
You need to pick a type of plastic for your injection molding project. That sounds pretty easy. After all, how many types of plastic could there possibly be?
Actually, there are more than 85,000 commercial options, and that could start your head spinning if you try to decide without some guidance. There are quite a few factors to consider—cost, durability, surface finish, strength, and flexibility are some of the most important ones. You also need to think about how and where your plastic part will be used.
Here are some common applications, along with suggestions for an appropriate plastic material. With this information in hand, you should at least be able to narrow down your choices:
Tool boxes, housings, handheld devices, and computers
The best choice here would be acrylonitrile butadiene styrene (ABS). A relatively inexpensive choice, ABS has high impact resistance, low shrink, and dimensional stability. Add to that its resistance to breaking, tearing, and most acids, and it’s easy to understand why ABS is popular in many industries.
On the downside, parts molded with ABS can have sinks and voids in thicker areas. You could reduce some of that by using an ABS-PC blended material.
Parts for the automotive, electronic, and telecommunications industries
ABS-PC blended plastic combines the flexibility of ABS with the strength and heat resistance of polycarbonate (PC). Some of its benefits include:
- Better processing during molding
- Increased toughness
- Dimensional stability
- Low-temperature impact resistance
- Fewer shrinks and voids
When it comes to transparent products—lenses, shatterproof windows, optical fibers, etc.—PMMA (also known as acrylic) and polycarbonate (PC) are both recommended. PMMA takes a high polish, has good tensile strength, and is economical, but if you need something that’s more impact or chemical resistant, PC is a safer bet. While it’s more expensive than PMMA, polycarbonate can be bent and formed at room temperatures without shattering it. And it is heat resistant and dimensionally stable.
Polyamide (PA), better known as nylon, provides high strength and withstands heat and vibration, which is especially suited for simple mechanical parts in engine compartments.
Another option, polyoxymethylene (POM), commonly called acetal, is known for its toughness, hardness, and strength. It works well for pump impellers, gears, automotive switches, and bearing surfaces.
Plastic containers and toys
Polypropylene (PP) is an inexpensive food-safe plastic used in food storage containers. Because it can be formed into a hinge, it’s often used for bottle caps and snap-over lids. Living hinges made from PP can repeatedly be bent without breaking them. Some of its other advantages: wear resistance, flexibility, and acid resistance.
Polyethylene (PE), the world’s most common plastic, is found in milk and medicine bottles and trash cans. Its elasticity also makes it a popular choice for plastic bags and cling-wrap.
Approximately one-third of all children’s plastic toys are made from PE. And with good reason. It’s non-toxic, colorfast, and inexpensive. For more strength and impact resistance, toys can be made from ABS or nylon.
It isn’t easy to choose the right plastic from such an extensive list. Discuss your application with a reputable plastic injection molding shop. They can lead you to the right material for your next project.
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