What is Thermosetting Plastic?
Thermosetting plastic is a polymer that irreversibly becomes rigid when heated. Such a material is also known as a thermoset or thermosetting polymer. Initially, the polymer is a liquid or soft solid. Heat provides energy for chemical reactions that increase the cross-linking between polymer chains, curing the plastic.
Thermosetting plastics are made up of long chains of molecules that are cross-linked. They have a very rigid structure. Once heated, thermosetting plastics can be molded, shaped, and pressed into shapes. Once set they cannot be reheated since they are permanently set.
Thermosetting plastics are generally stronger than thermoplastic materials due to the three-dimensional network of bonds (cross-linking) and are also better suited to high-temperature applications up to the decomposition temperature since they keep their shape as strong covalent bonds between polymer chains cannot be broken easily.
The higher the crosslink density and aromatic content of a thermoset polymer, the higher the resistance to heat degradation and chemical attack. Mechanical strength and hardness also improve with crosslink density, although at the expense of brittleness. They normally decompose before melting.
Thermosetting Plastic Examples
Example of thermosetting plastic:
- Epoxy Resin
- Vinyl Ester Resin
- Cyanate Ester
- Poly Ester
- Polyurethane, and
Uses of Thermosetting Plastics
Some of the common uses of thermosetting polymers are:
- Thermosetting plastics are heat resistant, so they are used in the making of kettles, plugs, laptop chargers, etc.
- They are used in Electrical fittings, handles, and control knobs, adhesives
- Thermoset components are used extensively in a wide range of industries – and are used for applications in the automotive, appliance, electrical, lighting, and energy markets due to excellent chemical and thermal stability along with superior strength, hardness, and moldability.
- These are used to produce construction equipment panels.
- These are used in agricultural equipment including feeding troughs and motors.
Advantages of Thermosetting Plastics
The benefits that thermoset plastics can offer over their metal counterparts include:
- Choice of color and surface finishes
- Resistance to corrosion effects and water
- Available molded-in tolerances
- High mechanical property
- Low thermal conductivity and microwave transparency
- High strength-to-weight ratio and performance
- Outstanding dielectric strength
- Lower tooling/set-up costs
- Excellent dimensional stability
- Reduced production costs over fabrication using metals
Disadvantages of Thermosetting Plastic
There are certain disadvantages to the use of thermosets:
- It cannot be recycled.
- low tensile strength and ductility
- It cannot be remolded or reshaped.
- Poor thermal conductivity for housing replacements.
- Much more difficult to surface finish.
- The rigidity of the material can result in product failure when used in high-vibration applications.
What is Thermoplastic?
A thermoplastic, or thermo-softening plastic, is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Thermoplastics differ from thermosetting polymers (or “thermosets”), which form irreversible chemical bonds during the curing process.
A thermoplastic is a material, usually, a plastic polymer, which becomes softer when heated and hard when cooled. Thermoplastic materials can be cooled and heated several times without any change in their chemical or mechanical properties.
When thermoplastics are heated to their melting point, they melt into a liquid. They freeze to a glassy state when cooled below their glass transition temperature.
Most thermoplastics have a high molecular weight. The polymer chains associate with intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid.
In this state, thermoplastics may be reshaped and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion.
Thermoplastic materials have many features. Some products made from thermoplastic materials are used for electronic applications. They protect against electrostatic discharge and radio frequency interference. Thermoplastics are one of the main two types of plastics.
Thermoplastic can be molded into any shape. Thermoplastics differ from thermosetting polymers. Thermosets form irreversible chemical bonds during the curing process.
Examples of thermoplastic
Examples of thermoplastic materials are polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamides, polyesters, and polyurethanes. High-temperature thermoplastics include polyether ether ketones, liquid crystalline polymers, polysulfones, and polyphenylene sulfide.
- Acrylonitrile butadiene styrene (ABS) is a thermoplastic used to manufacture:
- Sports equipment.
- Various automobile parts
- Polycarbonate is used to make:
- CDs and DVDs.
- Drinking bottles
- Food storage containers
- Eyeglass lenses.
- Polyethylene is probably the most common thermoplastic and is used to make:
- Shampoo bottles.
- Plastic grocery bags.
- Bullet-proof vests.
Advantages of Thermoplastics
The primary advantage of thermoplastics is a wide range of applications:
- Extremely adhesive to metal
- Thermoplastics are lightweight materials,
- High strength, and relatively low processing costs.
- High recyclable
- Superb impact resistance and can be remolded and reshaped
- Excellent corrosion resistance and detergent and chemical resistance
- Slip enhancement
- Flexibility and elongation of the coating film
- Electrical insulation
- Aesthetically-superior finishes
Disadvantages of Thermoplastics
- Thermoplastics degrade more easily in direct sunlight or under UV exposure
- Not all thermoplastics resist hydrocarbons, organic solvents, and polar solvents
- Some types of experience creep under long-term loading
- Can fracture rather than deform under high stress
The difference between thermoplastic and thermosetting plastic
The primary difference between the two is that Thermoset is a material that strengthens when heated but cannot be remolded or heated after the initial forming, while thermoplastics can be reheated, remolded, and cooled as necessary without causing any chemical changes.
|Thermoplastic can be synthesized by the process called addition polymerization.
|Thermosetting plastics are synthesized by condensation polymerization.
|Thermoplastic is processed by injection molding, extrusion process, blow molding, thermoforming process, and rotational molding.
|Thermosetting plastics have primary bonds between molecular chains and are held together by strong cross-links.
|Thermoplastics have secondary bonds between molecular chains.
|Thermosetting plastics have primary bonds between molecular chains and held together by strong cross-links.
|Thermoplastics have low melting points and low tensile strength.
|Thermosetting plastics have high melting points and tensile strength.
|Thermoplastic is lower in molecular weight, compared to thermosetting plastic.
|Thermosetting Plastic is high in molecular weight.