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Difference between Thermoset & Thermoplastic Injection Molding

Released on Apr. 29, 2022

Difference between Thermoset


Thermoplastics and thermosetting plastics are two separate classes of polymers that are widely used in the process of injection molding to create products of various types. Both these categories of plastics possess different properties and characteristics. Hence, choosing the right category of polymer, between the two, is of paramount importance to achieve the expected results when used in applications.  Most injection molding service providers usually receive a question from their clients about the differences between thermoplastic and thermoset molding processes. Here, in this post, let’s see the thermoset & thermoplastic injection molding comparison.


Defining Thermoplastic and Thermosets

Before we go deeper into the topic, it is important to understand the two terms thermoset and thermoplastic. Let’s first find out what are thermosets and thermoplastics.


What Are Thermosets?

Thermoset plastics “set” after they cure and are generally stronger than thermoplastic materials. Initially, the polymer is a liquid or soft solid, which becomes rigid later when cured. Owing to their high mechanical and physical strength, resistance to heat, corrosion, and mechanical creep, thermosets are used in a variety of applications. A few of the common thermoset materials used in the injection molding process include alkyds, epoxy, phenolic, polyimides, thermoset polyester, and so on.


What Are Thermoplastics?

In contrast to thermosets, thermoplastics liquefy and become pliable when heat is applied. Thermoplastic polymers can be reheated and reprocessed many times, which is impossible when it comes to thermosets. Usually stored in the form of pellets prior to the molding process, these categories of polymers can withstand multiple re-shaping without causing any damage to the material. They possess high strength, shrink-resistance, flexibility, high-Impact resistance, and chemical resistant, among others. A few of the common thermoset materials used in the injection molding process include ABS, nylon, PET, polypropylene, polyethylene, and TPE, among others.


Difference between Thermoset & Thermoplastic Injection Molding

The way thermosets are molded differs with respect to thermoplastics in several aspects and both the categories require varied treatment during the injection molding process. Let’s check a few differences when molding thermosets and thermoplastics.


ㆍCold material is injected into an extremely hot mold to produce parts. 

ㆍForm a permanent chemical bond.

ㆍCannot be remolded or reshaped

ㆍComparatively difficult to surface finish

ㆍThermoset injection molding doesn’t require high heat and high pressure compared to the molding of thermoplastics.

ㆍPrepared mostly by condensation polymerization.

ㆍThe production process encompasses compression, transfer, and casting.

ㆍExamples of products made from thermosetting injection molding include: Tool handles, billiard balls, sprockets, insulation, parts of computers, parts of TVs or any electronic equipment, gardening items, tools, cooking utensils

ㆍDisadvantages include: 

1. Difficulty in recycling. 

2. Release emissions are known as volatile organic compounds (VOCs).


ㆍPlastic material is melted and injected into a mold to produce parts.

ㆍ100% reversible as no chemical bonding takes place during the process.

ㆍCan be remolded and recycled

ㆍInjection molding using thermoplastics produces flexible, accurate, and aesthetically pleasing surface finishes.

ㆍThermoplastic injection molding demands high heat and high pressure.

ㆍPrepared mostly by additional polymerization.

ㆍThe production process involves injection molding, extrusion, and blow molding.

ㆍExamples of products made from thermoplastic injection molding include: Vacuum cleaners, kettles, toasters, toys, machine screws, gear wheels and power tool casings, packaging film, sacks and gas pipes, and fittings.

ㆍDisadvantages include:

1. Expensive

2. Can melt if heated

3. Difficult to prototype

Now that you know how thermoset injection molding differs with respect to thermoplastic injection molding. With the information provided in the post, you would be able to make a judgment on the type of polymer category you should opt to produce molded parts. However, just knowing the differences between the materials won’t be enough, instead, you would need an injection molding service provider who can mold your parts as per the right specifications provided. Partner with leading injection molding companies like Fine Art who own a comprehensive working knowledge regarding injection molding.