Most Common Thermoplastics Used In Injection Molding

Thermoplastic injection molding is the most common way to manufacture parts. Thermoplastics are polymers that can be repeatedly molten or softened by heating and solidified by cooling—as a physical change rather than a chemical change that takes place during the creation of thermoset materials. It is important to distinguish what type of thermoplastic should be used for the type of product you want us to help you create. Below are the most common thermoplastics used in injection molding.

Acrylonitrile Butadiene Styrene

Acrylonitrile Butadiene Styrene (ABS), is an opaque thermoplastic and amorphous polymer. It is a terpolymer (copolymer consisting of three distinct monomers) of Acrylonitrile, Butadiene, and Styrene. Together they create a product that is flexible and light in weight that can be molded into many items that we use in our everyday lives.

The advantage of ABS is that a variety of modifications can be made to improve impact resistance, toughness, and heat resistance. The last properties of the process will influence the final product. Molding at a high temperature improves the gloss and heat resistance of the product whereas molding at a low temperature is where the highest impact resistance and strength are obtained.

In addition to molded plastics, ABS is used in drain pipe systems, plastic clarinets, golf club heads, automotive parts, common appliances in a kitchen, LEGO bricks, and many other products.

Polyethylene

Polyethylene is a thermoplastic polymer with variable crystalline structure and an extremely large range of applications depending on the specific type. It is one of the most versatile and most popular plastics in the world since the 1950s when it was developed by German and Italian scientists. The two most common types of this plastic are high-density polyethylene (HDPE) and low-density polyethylene (LDPE).

The advantages of polyethylene are high levels of ductility, tensile strength, impact resistance, resistance to moisture absorption, and recyclability. The higher the density of the polyethylene material used the stronger, more rigid, and more heat resistant the plastic is. The primary uses of polyethylene are plastic bags, plastic films, containers including bottles, and geomembranes.

 Polycarbonate

Polycarbonate (PC) plastics are a naturally transparent amorphous thermoplastic. They are used to produce a variety of materials and are particularly useful when impact resistance and transparency are a requirement (ex: bullet-proof glass). Unlike most thermoplastics, PC can undergo large plastic deformations without cracking or breaks.

PC is commonly used for greenhouses, digital disks like DVDs, eyewear lenses, medical devices, automotive components, and cellular phones.

Polyamide (Nylon)

Nylon material is used in a large range of different applications because of its electrical properties, toughness, wear resistance and chemical resistance being quite impressive. Nylon has a high level of stability (helps with strength) and is resistant to many external factors like abrasion, impact, and chemicals. This material produces plastic parts used in many industries such as:

• Medical products
• Automotive products
• Sports equipment
• Apparel and footwear
• Industrial components

High Impact Polystyrene

High Impact Polystyrene (HIPS) is a popular and tough plastic that is in the Polystyrene family. Polystyrene is brittle and can be made more impact resistant if combined with other materials (in this form it is known as HIPS). It is made from modifying crystal styrene with rubber which helps to give it many levels of impact resistance. It is low cost, has good dimensional stability and rigidity. There are FDA grades available since it is non-toxic and used as containers for many food goods.

It is highly flammable, but there are flame retardant and high gloss grades that are commonly used for injection molding.

Polypropylene

This is a very common plastic that is known for its flexibility. PP (polypropylene) is a very dynamic plastic and has been compounded for a wide range of properties. Some characteristics of this plastic are its high melting point, high resistance to stress and cracking, excellent impact strength, and does not break down easily from reactions with water, acids, and detergents.

PP is safe for use as food containers because it does not leach chemicals into food products. It can be commonly found in household goods such as utensils, athletic apparel, area rugs, and automotive parts such as car batteries.

Choosing the right material for your application can result in increased performance and reduced cost. At Midstate Mold, we understand that there is no “one size fits all” solution when it comes to the production of molded plastic parts. We have been producing high-quality plastic injection parts for our clients around the globe since 1965. If you have any questions or concerns on what type of plastic you should be using, contact our team of experts who can help you every step of the way.