What type of plastic is used for injection moulding?
You’d surprised by just how many consumer products have plastic moulded parts. Think telecoms equipment and toys. Medical products and electrical appliances. Aerospace parts and lighting components. Without plastic injection moulding the appearance – and practicality – of many of our consumer products would be quite different.
Plastic injection moulding should never be undervalued. Why? Manufacturing wouldn’t be the same without it. We rely on plastic injection moulding for mass production. It’s accurate. Has affordable unit costs and short lead times.
How many different types of polymer are there?
There are 85,000 different types of commercial injection moulding polymers. Each is divided into 45 individual families and then classified into two categories: thermosets and thermoplastics. Choosing the right polymer depends on the required material composition. The most common polymers used for consumer application are:
- Polypropylene (PP)
- Acrylonitrile Butadiene Styrene (ABS)
- Polyamide (Nylon)
- High Density Polyethylene (HDPE)
- Polycarbonate (PC)
- High Impact Polystyrene (HIPS)
- ABS + PC Blend (typically for electronic application)
So, what are the individual attributes of each of these plastic polymers? Let’s examine each to define the right polymer for the right application.
This common, dynamic plastic is renowned for its flexibility and can be compounded (mixed with other polymers and additives when in a molten state) to achieve desired characteristics.
Polypropylene typically has a high melting point and resistance to stress and cracking. It also has excellent impact strength and is difficult to break down when reacting with water, acids and detergents. Moreover, PP is highly resistant to fatigue and therefore many integral hinges, such as those used on pill boxes, are made from polypropylene.
Moreover, because the polymer will not leach chemicals into food products, compromising health, PP is favoured as the polymer of choice for food containers. PP is also prevalent in in household utensils, car batteries, athletic clothing and household area rugs.
Acrylonitrile Butadiene Styrene (ABS)
This opaque thermoplastic polymer does not have a clearly defined form and consists of three separate monomers (identical molecules that have been bonded together) to form a polymer: acrylonitrile, butadiene and styrene. The polymer is lightweight, flexible and can be moulded into a range of different consumer products.
The primary benefits to acrylonitrile butadiene styrene are the polymer improves impact resistance, enhances tensile strength and is highly resistant to heat.
When moulded at a high temperature, ABS will:
- Become very heat resistance
- Have a glossy finish
- Become highly impact resistant
- Have enhanced tensile strength
ABS is often used in the manufacture of drainpipe systems, automotive parts and common kitchen appliances. It is also used to mould plastic clarinets, in the design of golf club heads and is what LEGO bricks are made of.
Often used as an alternative to metal bearings and bushing, polyamide (or nylon) features outstanding bearing and wear properties and often eliminates the need for external lubrication.
This strong, stiff polymer is often praised for its durability and resistance to external abrasion, chemicals and impact. Not only that, but polyamide is also easy to fabricate, machine and reduces the weight, noise and general wear and tear of mating parts (surface of two or more separate parts that are in contact with one another.)
You’ll find polyamide in a wealth of different products and sectors. From medical and automotive products to sports equipment, apparel and footwear, plus certain industrial components.
High Density Polyethylene
One of the most versatile of plastic polymers, high density polyethylene (HDPE) has the added attribute that it’s widely recycled, whether it has a rigid state or flexible state. Today, HDPE is the most widely used plastic polymer.
HDPE is attractive to commercial applications. Why? It’s lightweight, versatile and strong. This makes the polymer an ideal replacement for a range of different products and industries. Additionally, HDPE is durable and weather resistant. It can also be moulded into a wealth of different shapes.
Common uses of HDPE include:
- Milk cartons
- Household appliances
- Cable insulation
- Food wrapping material
- Carrier bags
A naturally transparent and shapeless thermoplastic, polycarbonate (PC) is used in the design of a range of different products. Particularly impact resistant and being transparent, PC is most notable used in the production of bulletproof glass.
As you can probably guess, PC can be subjected to strong pressure be it on a miniscule or expansive surface area without ever cracking or breaking. In fact, PC is virtually unbreakable, with a float strength 250 times that of glass and 30 times that of acrylic.
Better still, polycarbonate has a long service lifespan and it’s sustainable. These attributes make PC one of the most desired polymers for a range of different products.
Polycarbonate sheets are perfect for greenhouses, boat windows, basketball backboards or even a terrace canopy. They have a fire rating of B1 and self-extinguishing, meaning that they won’t burn when they come into contact with an open flame and as such are often used to encase fire extinguishers.
High Impact Polystyrene (HIPS)
This tough plastic polymer is much sought-after for a range of applications. In its natural state, polystyrene is brittle and features minimal impact resistance. It’s made more impact resistant when combined with other materials – which forms HIPS.
Recyclable with sound property retention, HIPS maintains its strength even after high impact, can be easily moulded to a range of shapes and sizes and can even be painted to suit application.
Made by modifying crystal styrene with rubber, HIPS has layered impact resistance, making it ideal for application across a range of different products. From TV and audio-visual equipment to appliance components vehicular instrument panels, even food containers.
PC + ABS Blend
A thermoplastic alloy of polycarbonate and acrylonitrile butadiene styrene is one of the most widely used industrial formless thermoplastics. PC + ABS is known for its enhanced processability, for being strong and rigid and being heat resistant.
The polymer is known for its UV and oxidation stability and fire safety properties. It features reinforcing agents, including glass fibres and mineral fillers which are added to the blend for a better strength and rigidity.
Commonly used in a variety of commercial applications, including telecommunications, electronics and automotive parts, this hard, yet lightweight plastic polymer can be found in instrument panels, seat belt components, door liners and handles, computer keyboards – even sports equipment and gardening tools.
Wide Range of Plastics Used for Injection Moulding
As you can see a range of plastics can be injection moulded to form a diverse range of products and components that we see and use every single day.
Flexible and with diverse application, the truth is that without plastic polymers, many of the products that we seeand use each day simply wouldn’t be the same.
The next time you open your laptop, put food in storage containers for meals throughout the week, sit behind the wheel of your car or pack your kit for a session in the gym take a minute to stop and think how different products would be without plastic polymer injection moulding – or even if the product would exist at all!
Wheatley Plastics can offer low, medium and high-volume injection moulding from our manufacturing facility in south Manchester. We’d be happy to discuss your requirements on 0161 477 2800.