Thermoplastics vs Thermosetting Plastics: Difference and Comparison

Key Takeaways

  1. Molecular Structure: Thermoplastics have linear or branched polymer chains held together by weak secondary bonds, allowing them to sand melt when heated. Thermosetting plastics have a cross-linked molecular structure formed by strong covalent bonds, making them infusible and insoluble after curing.
  2. Response to Heat: Thermoplastics can be melted and re-molded multiple times without significant chemical changes. Thermosetting plastics undergo a permanent chemical change when heated and cured, retaining their shape and becoming unmeltable.
  3. Properties and Applications: Thermoplastics offer flexibility, good impact resistance, and are recyclable, making them suitable for everyday products and various manufacturing processes. Thermosetting plastics provide high-temperature resistance and superior mechanical properties and are commonly used in applications that require heat resistance and stability, such as electrical insulation and aerospace components.

What are Thermoplastics?

The types of resin that change from solid to soft once heated and gradually turn to liquid form are known as thermoplastics. They are the resultant products of either crystal melting or turning into liquid due to crossing the glass transition at a certain temperature.

No chemical bonding processes are required to get the desired shape of thermoplastics; one can put them into molds and acquire their solidified forms. The material properties of thermoplastics remain unchanged despite reheating and recycling. They can also be molded again after recycling.

Because of the flexible nature of thermoplastics, they are used in various extrusion processes, thermoforming, and injection molding. Different forms of thermoplastics have varying properties. These forms include PET or polyethylene terephthalate, which is widely used in making various products that we use daily.

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Thermoplastics can lose their physical properties due to exposure to high temperatures, but their chemical properties remain unchanged. They provide elasticity, strength, and flexibility. Different forms of thermoplastics include polycarbonate, polystyrene, polypropylene, etc.

Better grip on metals, flexibility, aesthetic finish, recycling, reshaping, resistance, insulation, anti-slip features, and non-corrosiveness are some of the pros of thermoplastics; on the other hand, some drawbacks of using thermoplastics are that it is expensive and can change its form when heated.

What are Thermosetting Plastics?

Thermosetting plastics or thermosetting resins are exactly contradictory to thermoplastics. They turn into a solid form once exposed to heat. At room temperature, they are in liquid form. Thermosetting plastics change their form from liquid to solid even when a chemical is added.

Thermosetting plastics are produced using either two main processes: RIM or reaction injection molding or RTM or resin transfer molding. During the curing process, these thermosetting plastics form permanent chemical bonds, also called crosslinks. These crosslinks hold the monomer chains from the material together.

They also hold the molecules without displacing them to prevent the material from reverting to liquid form. They maintain and preserve the solidification of the material. While heating thermosetting plastics, caution must be taken as overheating can cause quality degradation.

Thermosetting plastics resist heat and chemicals, making them suitable for electronic appliances, chemical processing equipment, etc. Composites are made from various thermosetting plastics like epoxy resin and phenolic.

Thermosetting plastics provide flexibility in product designs and structural integrity; they are affordable and water, heat, and corrosion-resistant. They have a relatively higher strength-to-weight ratio. However, they are not recyclable, and reshaping is impossible. 

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Difference Between Thermoplastics and Thermosetting Plastics

  1. Thermoplastics are solid at room temperature; however, thermosetting plastics are liquid at room temperature.
  2. Thermoplastics are liquid once heated; however, thermosetting plastics are solid once heated.
  3. Thermoplastics can be reshaped; however, thermosetting plastics cannot be reshaped.
  4. Thermoplastics can be recycled; however, thermosetting plastics cannot be recycled.
  5. Thermoplastic’s melting point is lower than that of thermosetting plastics.
  6. Thermoplastics are costlier than thermosetting plastics.

Comparison Between Thermoplastics and Thermosetting Plastics

Parameters Of ComparisonThermoplasticsThermosetting Plastics
Tensile strengthSynthesis is done by additional polymerizationHigh
BondsSecondaryPrimary
SynthesisSynthesis is done by condensation polymerizationReaction injection molding.
Processed byThermoforming, extrusion etc.Thermoforming, extrusion, etc.
Melting pointsLowHigh
ExamplesTeflon, nylonBakelite, epoxy resin
Heat resistanceLowHigh
References
  1. https://onlinelibrary.wiley.com/doi/abs/10.1002/9781118480793.ch28
  2. https://onlinelibrary.wiley.com/doi/abs/10.1002/9781118480793.ch28

Last Updated : 13 July, 2023

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