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Thermoset vs Thermoplastic Materials: Key Differences
Reading Time: 4 minutes
Designers of end products must understand thermoset vs thermoplastic materials. In the realm of molding products, these materials are the most common polymers used. Both are used to produce a range of materials and parts used in various markets.
Both of these polymers, while fulfilling comparable roles, belong to distinct classes with their own set of characteristics, production techniques, and practical uses.
Thermosets, for instance, are capable of higher durability due to their chemical bond when cured. This performance attribute makes them more suitable for critical applications. It’s essential to grasp these distinctions to make informed choices about the most fitting polymer for a given application.
Exploring Thermoplastics
Thermoplastics make up more than 75% of the global consumption of plastic usage globally. These plastics are supplied as pellets and are easily molded into various shapes, without the need for chemical bonding. They can be recycled and reused to create new products.
A more cost-effective option compared to metals, thermoplastics can be manufactured on a large scale at low costs. They are versatile, being used in several manufacturing processes such as injection molding, extrusion, and thermoforming. Thermoplastics are distinguished by their impressive thermal, mechanical, electrical, and chemical qualities compared to typical resins.
Thermoplastics Profile
A variety of thermoplastics are on the market possess unique characteristics ideal for specific products. This table outlines different types of thermoplastics, their properties, and applications.
| Thermoplastic | Description | Applications |
| ABS (Acrylonitrile butadiene styrene) | Tough, glossy, and good electrical insulation | Auto parts, LEGO blocks |
| Acrylic | A more durable substitute for glass. | Motorcycle helmet visors, plane windows, eyeglass lenses |
| Polycarbonate
|
Tough, transparent, and heat resistant. | Medical products, construction materials, electronic components, auto parts. |
| Polyethylene | The most common thermoplastic, polyethylene features a family of materials ranging from ultra-high molecular weight that provide extremely tough plastic with high corrosion and chemical wear resistance to a lower cost linear low density that offers good processability and high impact strength. | Packaging machinery parts, artificial joints, chemical tanks, and marine bumpers to shampoo bottles, lamination films, and plastic bags.
|
| Polystyrene | Made from styrene, it is clean, hard, weatherproof, and nonflammable. | Packing peanuts, disposable cutlery |
| Polyvinyl chloride | Lightweight, tough, and resistant to acids and bases. | Home vinyl siding, drain pipes, gutters, roofing sheets. |
Exploring Thermosets
Thermosets are available in liquid, pellet or bale forms. They are designed to cure and harden inside molds to form specific shapes. After solidifying, they cannot be melted down or reformed because permanent chemical bonds develop during the curing phase. This cross-linked molecular architecture makes this polymer very strong and dimensionally stable, making them ideal for use in high-performance environments.
Types and Uses of Thermosets
As with thermoplastics, thermosets come in a variety of formulas with different properties. This table showcases some different types of thermoset profiles.
| Thermoset | Description | Applications |
| Polysulfide (T) | Excellent chemical resistance, low temperature flexibility and dielectric strength | Tank liner, potting compound, vibration mount |
| Nitrile (NBR) | Oil & chemical resistance | Seals, gaskets, hoses |
| Polybutadiene Rubber (BR) | Low hysteresis loss, low coefficient of friction | Tire sidewalls, golf balls |
| Styrene-Butadiene Rubber (SBR) | Abrasion resistance, impact strength, tensile strength | Tires, belts, footwear |
| Natural Rubber (NR)
|
Durability, abrasion resistance, elongation | Weather stripping, window seals, animal toys |
| Ethylene Propylene Diene Rubber (EPDM) | Electrical insulation, elongation, water & steam resistant | Wire & cable, diaphragms, roofing |
| Silicone (Q) | Weather resistant, low compression set | Coatings, sealants, medical devices, kitchenware |
Thermoset vs Thermoplastic Polymers
Key distinctions between thermoplastics and thermosets lie in their ability to be recycled & their reaction to heat. Thermoplastics can be melted and formed or reformed with heat, recycled & reused, while thermosets have a chemical cross-linking to maintain their structural integrity. Thermosets are permanently set after the initial molding. This limits their recyclability, but not their usefulness.
The specific properties of each are detailed in this Table for comparison.
| Property | Thermoset | Thermoplastic |
| Molecular structure | Network polymers with strong bonds | Linear polymers with weak bonds |
| Melting point | High | Low |
| Mechanical | Brittle and inelastic; strong chemical bond, resistant to creep. | Flexible, elastic, and impact-resistant; strong from crystalline microstructure |
| Recyclable | Retain permanent chemical bonds during the curing process (can pose waste management challenges) | Yes (but factors like mixed plastic and contamination can cause challenges) |
| Chemical Resistance | Good | High |
| Applications | High-performance apps: electronics, aerospace, and auto components as insulation, structural components, adhesives | Broad application use: packaging, medical devices, plastic bags, artificial joints, cookware coating |
Selecting the Correct Polymers and Additives
With the vast selection of polymers available in the categories of thermoplastics and thermosets, it’s vital to identify the specific properties of each that can benefit a particular product or component.
H.M. Royal sells additives that impart performance characteristics into both thermosets and thermoplastics.
Curing agents
Curing is essential for thermosets, as it transforms them from pliable, tacky materials into durable and resilient products. The choice of curing agent depends on factors such as the base polymer, processing conditions, and the requirements of the final product.
Curing agents can take various forms–powders, liquids, or filler-supported–with the selection depending on the mixing conditions. Common chemical curatives include peroxide & sulfur, and they play a vital role in a wide range of applications, such as automotive parts, conveyor belts, adhesive tapes, and wire and cable products.
Flame retardants and smoke suppressants
Flame retardants diminish the flammability of both thermoset and thermoplastic formulations. Fires can erupt in various scenarios and find applications in numerous applications, spanning from electronic devices to household furnishings.
Selecting the appropriate flame-retardant additive for your specific needs depends on several key factors:
- The type of polymer being used
- Compounding process conditions
- Operating temperatures
- Desired performance specifications for the final product
Process aids & plasticizers
Processing aids and plasticizers enhance the plasticity, fluidity, and lubrication of thermoset and thermoplastic products. These additives soften polymers, making processing easier, reducing viscosity, and increasing flexibility.
Since there’s a wide variety of chemicals used, the choice of additive depends on specific compound requirements, process needs, and chemical compatibility. These additives find applications in various products such as flooring, tubing, beverage bottles, building materials, automobile engine hoses, and wire and cable jackets.
Phenolic resins
These resins impart increased hardness, toughness, rigidity, and enhanced tear resistance to elastomer parts such as belts, hoses, and brake pads. We offer both heat-reactive and non-heat-reactive thermoplastic options.
Thermoset vs thermoplastics? We can help you decide which is right for your application and select the required additives. Contact an expert at H.M. Royal today.
