Using The Right Thermoplastic Material For Your Project

Before you start designing your product, you must decide which thermoplastic you will use. Your material requirements may vary depending on the industry, the product’s environment, and the product’s intended life span. The two most common types of thermoplastics are commodity and engineering.

A thermoplastic resin becomes molten when heated above a certain point and solidifies when cooled. The process can easily be reversed without any impact on its properties. Engineering grades have a higher melting point than commodity plastics.

Before choosing your plastics, you need to you will need to answer questions about the product’s design and use. Examples include:

  • Will the product be exposed to harsh environmental conditions?
  • Will it be exposed to chemicals or solvents?
  • Does it need to be compatible with other elements?
  • Will it be exposed to very high or very low temperatures?
  • Does it need to be strong or impact-resistant?
  • How critical is the surface finish?
  • What are acceptable tolerances?
  • How complex is the shape?

Thermoplastics each have their own properties that may or may not be useful for your product. Working with an injection molder with vast material knowledge is critical to help you choose the correct thermoplastic for your project. Below is a brief overview of some commodity and engineering grades Greenleaf has experience with.

Commodity Thermoplastics for Injection Molding

Commodity thermoplastics are inexpensive and easy to process. They are used in various applications, including toys, interior automotive parts, and consumer products. Below are the pros, cons, and uses for five common commodity plastics used for injection molding.

Acrylonitrile Butadiene Styrene (ABS)

Pros

  • Superior stiffness and strength
  • Outstanding impact and abrasion resistance
  • Excellent chemical resistance
  • Low cost

Cons

  • Not appropriate for high temperatures
  • Poor solvent resistance
  • High fatigue resistance
  • Doesn’t stand up well to UV exposure and weathering

Some uses include:

  • Toys (like LEGO® blocks)
  • Consumer goods
  • Machine housing
  • Auto interiors

 

Poly (methyl methacrylate) (PMMA) – also known as acrylic

Pros

  • Good strength and stiffness
  • Optically clear
  • Good dimensional stability
  • Resistant to shrinkage and flash
  • moderate cost
  • Excellent insulation properties
  • Good weathering

Cons

  • Will crack under high pressure – not for structural use

Some uses include:

  • Aquariums
  • Casing
  • LED diffusing light panels
  • Glass replacement

 

Polypropylene (PP)

Pros

  • High impact resistance
  • Excellent durability
  • Easily processed
  • Food contact safe
  • High chemical resistance

Cons

  • Low strength
  • Sensitive to UV light
  • Not suitable for high-temperature applications

Some uses include:

  • Consumer goods
  • Living hinges
  • Automotive components

 

Polyethylene (PE)

Pros

  • Durability
  • High impact strength
  • Resistant to warpage and shrinkage
  • Highly flexible

Cons

  • Low strength
  • High thermal expansion
  • Poor weatherability

Some uses include:

  • Tool handles
  • Toys
  • Bottle caps
  • Packaging

 

Polystyrene (PS)

Pros

  • Good rigidity
  • Lightweight
  • Easily molded
  • Foods safe

Cons

  • Poor impact strength
  • Poor chemical and solvent resistance

Some uses include:

  • Food packaging
  • Automotive parts
  • Plastic utensils
  • Toys
  • Product casing

Engineering Thermoplastics for Injection Molding

Engineering resins have better thermal and mechanical properties than commodity plastics. They offer high strength as well as heat, wear, and corrosive resistance. Engineering plastics are often used to replace other materials, such as metal, to reduce product weight.

Acetal

Pros

  • Moderate strength and impact resistance
  • Excellent chemical resistance
  • Excellent wear and abrasion resistance properties
  • Can maintain shape when exposed to heat and pressure
  • Fair resistance to warpage and shrinkage

Cons

  • Degrades when exposed to considerable UV light
  • Poor resistance to acid

Some uses include:

  • Valve parts
  • Bearing
  • Springs

 

Polycarbonate (PC)

Pros

  • Good strength & impact resistance
  • Heat resistant
  • Excellent stiffness
  • Dimensionally stable
  • Good optical clarity

Cons

  • Impact strength drops dramatically in freezing temperatures
  • Poor scratch resistance
  • Poor solvent resistance

Some uses include:

  • Light covers
  • Lenses
  • Face shields
  • Machine guards

 

Polyamide (PA) – common name is Nylon

Pros

  • High strength and impact resistance
  • Dimensional stability
  • High abrasion resistance
  • Good chemical resistance
  • Filled grades offer additional properties.

Cons

  • Water absorption
  • Low resistance to acid and bases
  • High shrinkage

Some uses include:

  • Bearings
  • Bushings
  • Rollers
  • Machinery parts
  • Suited for structural parts

 

Thermoplastic Elastomer (TPE)

Pros

  • Rubber-like characteristics – Returns to original shape when stretched to moderate elongation
  • Good weatherability
  • Good UV resistance

Cons

  • Low strength
  • Susceptible to creep
  • Can lose rubbery properties at high temperatures

Some uses include:

  • Seals
  • Bushings
  • Footwear
  • Auto parts

 

Polybutylene Terephthalate (PBT)

Pros

  • High resistance to solvents
  • High strength
  • Excellent dimensional stability
  • Good heat resistance
  • Good electrical resistance

Cons

  • Poor resistance to acids, bases, and hydrocarbons
  • Poor resistance to hydrolysis (sensitive to boiling water)
  • Prone to warpage due to high differential shrinkage

Some uses include:

  • Auto parts
  • Electronic and electrical parts
  • Mechanical gears
  • Sporting goods

Let’s Create Something Great

The list above is just a few of the thermoplastics we have experience with at Greenleaf Industries. With so many thermoplastics available, knowing which is the best choice for your application and budget can be challenging. When you choose our plastic injection molding services, we can work with you to design and engineer your product and use efficient production processes to cut costs, reduce cycle time and offer 100 percent on-time delivery.

Contact us to learn how we can reduce your production costs.

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