WHAT MATERIALS CAN BE USED IN PLASTIC INJECTION MOULDING?
One can easily get lost in the plastic jargon; not only are the names complex, but it can also be a tad bit confusing trying to differentiate them from one another. How do you know the best choice between high density and low-density polyethylene or distinguish polypropylene from polyethylene? While they may seem similar, it is essential to tell them apart as they differ in their properties and uses.
How then do you make the choice of thermoplastic for your plastic needs?
There is no single hard and fast rule to it. Each product is unique in the function it serves and the physical environment it is exposed to. These physical factors include:
- Chemical exposure,
- UV light et cetera.
Other factors like the material’s strength, durability, flexibility, color, and cost are also important.
There are several manufacturing methods, including; Plastic injection moulding, Rotational moulding, Extrusion blow moulding, reaction injection moulding, and Vacuum casting. However, plastic injection molding remains the technique of choice, responsible for over 80% of plastic manufacturing. This is because it can be used to quickly manufacture large quantities of similar products.
Below is a list of some thermoplastics commonly used in injection moulding, their properties, and everyday items they can manufacture to guide you in making the right plastic choice.
- Acrylonitrile Butadiene Styrene (ABS)
ABS is one of the most commonly used thermoplastics in injection moulding. It is a very resilient plastic, sturdy, opaque, and lightweight. It is resistant to high temperatures, chemicals, and abrasions with excellent tensile strength and dimensional stability.
These properties make ABS the material of choice in manufacturing engineering-grade items. It is also food-grade safe, and recyclable, which makes it a good choice for the ecosystem. Examples of items manufactured from ABS include; keyboards, pipes, automotive parts, electric insulator parts- adaptors, and wall sockets.
While ABS is an excellent plastic choice due to the benefits mentioned above, it is not a good choice for outdoor use. ABS’s prolonged exposure to sunlight reduces its tensile strength, surface gloss, and hardness and causes color changes.
- High-density polyethylene (HDPE)
HDPE is a semi-rigid, rugged, low-cost, weatherproof material with good resistance to chemicals. HDPE is a popular choice for manufacturers because it is easy to process. Its high abrasion and tears resistance and high tensile strength are some of HDPE’s impressive properties.
HDPE plastics are hundred percent recyclable! They are also reusable, thus a great environmental choice. The major downside to HDPE is that it is highly flammable. It can be termed household plastic as it is commonly used in the production of kitchen wares, food packaging (milk and juice bottles), and toys.
- Low-density polyethylene (LDPE)
While both LDPE and HDPE are low-cost, weatherproof, light-grade materials, they differ slightly in some properties. Where HDPE is semi-rigid, LDPE is a highly flexible material. What HDPE has in tensile strength, LDPE makes up for in impact strength and high fatigue life span. It has thus found use in the production of toys, plastic bags, wraps, and bottles. It is also used to produce electric cables, insulation, and hydraulics. Like HDPE, it is also highly flammable.
Also called polyamide (PE), Nylon is chosen for its toughness and abrasive strength. The major downside is its tendency to absorb moisture. It is not the resin of choice if you intend to manufacture parts of a marine automotive or an item constantly exposed to water.
It is preferred as a light weighted and cheaper alternative to metals in automotive production. Its remarkable wear resistance and excellent bearing ability have contributed to its wide acceptance as an engineering plastic. Nylon is used in making mechanical parts like gears, bushing, gasket, wheels, and bearings.
Do you need a transparent item? Acrylic is the right choice. It is an excellent alternative to glass. Also known as Polymethyl methacrylate (PMMA), acrylic is known for its optical clarity, stiffness, and strength. It is also lightweight and has good resistance to abrasion and weathering.
Its fine gloss makes it aesthetically pleasing, hence a good choice if aesthetics is an essential component of your product.
What acrylic has in beauty, transparency, and abrasive resistance, it lacks in heat resistance, and also easily cracks under pressure. It is generally used in display signs, frames, shelves, and skylights, among others.
- Polycarbonate (PC)
This is another injection moulding resin of choice where optical clarity is needed. It has the advantage of greater strength when compared to acrylic. However, the cost of production is higher as it requires moulds made of more expensive materials. PC has good abrasion resistance as well.
There are different grades of PC available, including; General purpose, sign grade, glass-filled, machine grade, and FDA compliant – with varying modifications that confer added advantages to the plastic.
- Polypropylene (PP)
PP is a food-grade plastic since the chemicals from the plastic don’t mix with the food. It is tough and semi-rigid with good chemical and heat resistance. PP also has high impact strength, high thermal expansion, and is resistant to moisture.
PP is used in the manufacture of crates, boxes, carpet fibers, OPP films for packing biscuits, tobacco, etc. The significant downsides to its use are that it is not resistant to ultraviolet rays from the sun, and is easily degraded when in contact with certain materials like copper.
Otherwise called thermoplastic rubber. It possesses excellent elasticity, which is its major advantage. Other properties of this resin include its high impact resistance, strength, chemical, and weathering resistance. It is also resistant to tears and abrasion.
Elastomer is quite costly and loses its elasticity at very high temperatures. They are used in grips and handles, cables, wires, and airbag covers.
Other plastic resins used in injection moulding include; thermoplastic polyurethane, polystyrene, polyoxymethylene, et cetera.
We do hope that this post helps you navigate the ever-confusing plastic lingo! Reach out to us at All Moulds Plastics for your unique plastic injection moulding needs.