Thermoplastic and Thermosetting plastics

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. The rate of curing may be increasing in many cases by increasing pressure or by adding a catalyst.

Curing is induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst. Heat is not necessarily to be applied externally. It is often generated by the reaction of the resin with a curing agent (catalyst, hardener). Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.

The starting material for making thermosets is usually malleable or liquid prior to curing, and is often designed to be molded into the final shape. It may also be used as an adhesive.

Once hardened, a thermoset cannot be melted for reshaping, in contrast to thermoplastic polymers which are commonly produced and distributed in the form of pellets, and shaped into the final product form by melting, pressing, or injection molding.

Example of thermosetting plastic

  • One of the most common examples of thermosets is bakelite which is relatively a bad conductor of electricity and heat.
  • It is mainly used for making electrical switches, handles of various utensils, etc.
  • Another example is Melamine which has the capacity to resist fire and heat much efficiently than other plastics.
  • It is used in kitchenware and fabrics as well as floor tiles.
  • Some other examples of thermoset plastic polymers include silicones, vulcanized rubber, epoxies, polyesters, and phenolics.

Application of Thermosetting Plastics

  • Thermoset plastics offer an enhanced high-performance combination of thermal stability, chemical resistance, and structural integrity.
  • Thermoset ingredients are used broadly in a wide range of industries and are used in the automotive, appliance, electrical, light, and energy markets due to their excellent chemical, thermal stability with excellent strength, hardness, and moldability.
  • Thermosetting plastic composites are capable of meeting the specifications of a wide range of production materials at a very low cost. Their use allows for the assortment of small and large parts to be fabricated with high production volumes while maintaining their repetition continuously from batch to batch.
  • Thermosets give an alternative method when complex and geometric patterns cannot be obtained through metal fabrication or the use of thermoplastics but can be manufactured in a mold. Thermoset plastics sustain their stability in all weather and heat.

Advantages of Thermosetting Plastics

The usage of thermoset plastics has a number of advantages. Unlike thermoplastics, they maintain their durability and shape even when heated. This provides thermosetting plastics well-suited to the making of permanent parts and large solid shapes. Additionally, these elements have excellent durability attributes (although they are brittle), and will not lose important strength when opened to higher operating temperatures.

Thermosets plastics have increased its demands between manufacturers, who have switched to their use as a lower-cost replacement for metal components.

The advantages that thermoset plastics can offer over their metal counterparts include:

  • Available molded-in tolerances
  • Choice of color and surface finishes
  • High strength-to-weight ratio and performance
  • Outstanding dielectric strength
  • Low thermal conductivity and microwave transparency
  • Resistance to corrosion effects and water
  • Lower tooling/set-up costs
  • Reduced production costs over fabrication using metals
  • More Resistant against high temperature
  • Hard and rigid
  • Excellent aesthetics finishes
  • High mechanical property
  • Excellent dimensional stability
  • Cost-effective

Disadvantages of Thermosetting Plastic

There are several disadvantages to the usage of thermosets whereas the material properties are not as developed as those of thermoplastics.

The low initial viscosity of materials results in a flash and the need for secondary operations. Also, low tensile strength and ductility tend to result in parts that require designs with thick walls.

The compounds used in thermosets are reactive methods, which can affect the useful shelf life. Batch methods may exhibit greater variation and less consistency from lot to lot.

High levels of some filler in the materials may appear in excessive tool wear. The product quality is dependent upon the degree of crosslinking set while the molding cycle.

  • Cannot be recycled.
  • 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 in vibration applications.
Thermoplastic and Thermosetting plastic

What is Thermoplastic?

Thermoplastics are defined as polymers that can be melted and recast almost indefinitely. They are molten when heated and harden upon cooling. When frozen, however, a thermoplastic becomes glass-like and subject to fracture.

These characteristics, which lend the material its name, are reversible, so the material can be reheated, reshaped, and frozen repeatedly. As a result, thermoplastics are mechanically recyclable. Some of the most common types of thermoplastic are polypropylene, polyethylene, polyvinylchloride, polystyrene, polyethylenetheraphthalate, and polycarbonate.

Thermoplastics have a simple molecular structure comprising chemically independent macromolecules. Upon heating, they are softened or melted, then shaped, formed, welded, and solidified when cooled. Multiple cycles of heating and cooling can be repeated, allowing reprocessing and recycling.

Examples of thermoplastic

Examples of thermoplastic materials are polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamides, polyesters, and polyurethanes. High-temperature thermoplastics include polyetherether ketones, liquid crystalline polymers, polysulfones, and polyphenylene sulfide.

Applications of Thermoplastics

Polluted, acidic, such as environments can be found in modern cities, steel piping systems are often vulnerable to corrosion or rust and therefore require special provisions for corrosion protection. The costs associated with protecting steel piping systems that are exposed to these harsh environments can be expensive. Thermoplastic is considered a favorable option to reduce these costs. Some properties of thermoplastic that make them a suitable substitute material:

  • Their ability to withstand corrosive materials and corrosive environments.
  • Remaining to bring materials of intense temperatures.
  • Their capacity to handle virtually any type of fluid transport application.
  • ABS: LEGO bricks, safety hats, whitewater canoes, musical instruments
  • Acrylic: Lucite, Perspex, Plexiglass
  • Polyester: Clothing, conveyor belts, blankets, mousepads, furniture, Yarn, rope,
  • Polypropylene: Carpets, textiles, packing, Lab equipment, labeling
  • Polystyrene: Disposable cutlery, smoke alarm housings, foam cups, models, CD/DVD cases
  • Cellulose Acetate: Cigarette filters, playing cards, eyeglass frames, adhesives, photography
  • Nylon: Carpet, rope, strings for musical instruments, fishing line, fabric

Other common applications for thermoplastic include high-pressure polyethylene for encapsulating rigid objects such as electrical equipment. Low-pressure polyethylene is very elastic and ideal for insulating electrical cables. Polyamide is most commonly associated with the production of ropes and belts.

Advantages and Disadvantages of Thermoplastics

Advantages of Thermoplastics

The primary advantage of thermoplastics is a wide range of applications. Thermoplastics are lightweight materials, high strength, and have relatively low processing costs. Additionally, thermoplastic components are relatively easy to manufacture with high volume and precision.

  • Extremely adhesive to metal
  • High recyclable
  • Superb impact resistance
  • Can be remolded and reshaped
  • Excellent corrosion resistance
  • Slip enhancement
  • Detergent and chemical resistance
  • Flexibility and elongation of the coating film
  • Electrical insulation
  • Chip resistance
  • Aesthetically-superior finishes
  • Superb corrosion resistance

Disadvantages of Thermoplastics

The primary limitation of using thermoplastics instead of materials such as metal is their comparatively low melting point. Certain types of low-quality thermoplastics can melt when they’re exposed to the sun for long periods. Furthermore, thermoplastics can have lower resistance to organic solvents, hydrocarbons, and highly polar solvents.

Thermoplastics are susceptible to creep, which occurs when the material stretches and weakens under exposure to long-term stress loads. The susceptibility to creep is further exacerbated by the lower melting temperature of the material. Different types of thermoplastics, such as composites, can crack instead of becoming deformed under high-stress conditions.

  • 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

Types of Thermoplastic Materials

Types of thermoplastics usually employed for manufacturing include polyethylene, polyvinyl chloride, and polystyrene, which often is used for packaging. Other groups of thermoplastics are fluoropolymers, acrylics, polyesters, polyimides, and nylons.

All of these types can be melted down repeatedly and re-shaped into different forms. For example, a foam cup is a thermoplastic material that can be remelted and fabricated into a dish.

Some of the most common thermoplastic materials in use include:

  • Polycarbonate
  • Acetal Copolymer Polyoxymethylene
  • Acetal Homopolymer Polyoxymethylene
  • Acrylic
  • Nylon
  • Polyethylene
  • Polypropylene
  • Polystyrene
  • Polyvinyl chloride (PVC)
  • Teflon

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.

ThermoplasticThermosetting Plastic
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 Plastic is processed by compression molding, reaction injection molding.
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.

FAQ

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.

What is Thermoplastic?

Thermoplastics are defined as polymers that can be melted and recast almost indefinitely. They are molten when heated and harden upon cooling. When frozen, however, a thermoplastic becomes glass-like and subject to fracture.

What is the main 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.

What are examples of thermoplastics?

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.

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