What are Thermoplastic Polymers Definition Types Examples and Differences from Thermosetting Polymers
Thermoplastics are formed by additional polymerization and are soft and less brittle. They are soluble in organic solvents. On heating the thermoplastics, it gets softer and hence are amenable for molding into any shape in the hot condition, on cooling the reason becomes hard and rigid and retains the molded shape. They can be reheated and molded into any other shape reversibly, any number of times without any change in the chemical nature.
It is the most common term used in polymer chemistry. In this article, we will cover all the important topics such as thermoplastic meaning, thermoplastic uses, characteristics of thermoplastic, and thermoplastic examples.
Characteristics of Thermoplastic
Thermoplastics are generally high molecular weight polymers.
The chains in the polymer are associated with the intermolecular forces.
The intermolecular force acting between the chains becomes weak on increasing temperature and yields a liquid with high viscosity.
These polymers can be reshaped.
These polymers are different from thermosetting polymers because thermosetting polymers do not get melted when heated.
Thermoplastics are recyclable.
These are lightweight and high strength polymers.
They act as flame retardants.
Thermoplastic Examples
Few thermoplastic examples are polyvinyl chloride, polystyrene, polypropylene, and polyethylene.
Polypropylene:
It is made up of monomer propene. It is produced by the chain growth polymerisation reaction mechanism. It belongs to the polyolefins group. It is a non-polar compound and partially crystalline.
Effect of Additives on the Properties of Polypropylene Thermoplastic Polymer
Since polypropylene has a low UV tolerance, additives such as hindered amines stabilize the light and prolong the service life when compared to unmodified polypropylene. Clarifiers, flame retardants, glass fibers, minerals, conductive fillers, lubricants, pigments, and a variety of other polymer additives can enhance the physical and/or mechanical properties of PolyPropylene.
Polypropylene can be divided into two types:
Homo polypropylene
Co polypropylene
Difference Between Homo Polypropylene and Co Polypropylene
Types of Polypropylene Films
Cast Polypropylene Film-
CPP stands for cast polypropylene and is well-known for its versatility. Polypropylene of this form is highly resistant to tears and puncture. They have higher heat tolerance and transparency at high temperatures.
Biaxially Oriented Polypropylene Film-
BOPP is a biaxially oriented polypropylene film that is extended in both the transverse and longitudinal directions, resulting in molecular chain orientation in both directions. This improves the tensile strength and stiffness of the material.
Polyvinyl Chloride-
It is made up of monomer vinyl chloride. It is a high strength material. Its abbreviation is PVC. It is a white-brittle and lightweight solid material.
Polystyrene
It is a polymer made up of a styrene monomer. It contains an aromatic group. It exists in either solid or foamed form. It is hard, clear, and brittle in nature. Its molecular formula is (C8H8)n.
Thermoplastic Uses
Thermoplastic material used in making sports equipment.
It is also used in making toys.
It is used in automobile parts.
It is used in making CDs and DVDs.
Containers like shampoo bottles, drinking bottles, and food storage containers are made up of thermoplastic polymer.
Some of the thermoplastics (polyurethane) are used as a sealant, adhesives, and coating material.
Disadvantages of Some Thermoplastic Polymers are:
The UV, effects, and scratch resistance is low for thermoplastic polymers.
Under -20°C, thermoplastic polymer embrittles
90 - 120°C is a low upper service temperature for thermoplastic polymers.
Thermoplastic polymer shows Paint adhesion problems
These types of polymers swell quickly in chlorinated solvents and aromatics when attacked by strongly oxidizing acids.
Action with metals has a negative impact on heat-aging stability.
Dimensional changes after molding due to crystallinity effects are observed in these polymers.
Did You Know?
Polyvinyl chloride is the world's third most widely produced synthetic plastic polymer.
Some of the thermoplastic can melt in direct sunlight.
Most thermoplastics show higher fatigue properties than metals. Therefore, it can tolerate higher deflections than metal.
FAQs on Thermoplastic Polymers Structure Properties and Applications
1. What are thermoplastic polymers?
Thermoplastic polymers are polymers that soften when heated and harden when cooled, and this process is reversible without significant chemical change.
- They consist of long linear or branched polymer chains held together by weak intermolecular forces.
- On heating, these forces weaken, allowing the material to flow and be reshaped.
- On cooling, the forces reform, and the material solidifies again.
- Common examples include polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC).
This reversible behavior makes thermoplastics widely used in molding, extrusion, and recycling processes.
2. How are thermoplastic polymers different from thermosetting polymers?
Thermoplastics soften on heating and can be remolded, whereas thermosetting polymers form permanent cross-linked structures and cannot be remelted once set.
- Thermoplastics: linear or slightly branched chains, weak intermolecular forces, recyclable.
- Thermosets: heavily cross-linked 3D networks, strong covalent bonds between chains, not recyclable by melting.
- Example thermoplastic: polyethylene (PE).
- Example thermoset: Bakelite.
The key difference lies in the presence or absence of cross-linking between polymer chains.
3. What are some common examples of thermoplastic polymers?
Common examples of thermoplastic polymers include polyethylene, polypropylene, PVC, polystyrene, and PET.
- Polyethylene (PE): used in plastic bags and bottles.
- Polypropylene (PP): used in containers and automotive parts.
- Polyvinyl chloride (PVC): used in pipes and cables.
- Polystyrene (PS): used in packaging and insulation.
- Polyethylene terephthalate (PET): used in beverage bottles.
These materials are widely used due to their moldability, durability, and recyclability.
4. Why can thermoplastic polymers be recycled?
Thermoplastic polymers can be recycled because they melt on heating without undergoing permanent chemical change.
- The polymer chains are not cross-linked by strong covalent bonds.
- Heating weakens intermolecular forces, allowing reshaping.
- Cooling restores the solid structure.
- This process can be repeated multiple times with minimal structural change.
Their reversible softening behavior makes thermoplastics suitable for mechanical recycling and reprocessing.
5. How are thermoplastic polymers formed?
Thermoplastic polymers are formed by addition or condensation polymerization of monomers into long-chain molecules.
- Addition polymerization: Unsaturated monomers join without elimination of small molecules.
Example: nCH2=CH2 → (–CH2–CH2–)n (polyethylene). - Condensation polymerization: Monomers react with elimination of small molecules like H2O.
Example: Formation of PET from terephthalic acid and ethylene glycol.
The resulting long chains give thermoplastics their characteristic strength and flexibility.
6. What is the structure of thermoplastic polymers?
Thermoplastic polymers have linear or slightly branched molecular structures with little or no cross-linking between chains.
- Chains are held together by van der Waals forces or dipole–dipole interactions.
- They may be amorphous or semi-crystalline.
- Weak intermolecular forces allow chains to slide past each other on heating.
This structural feature explains their flexibility, ductility, and remoldable nature.
7. What are the properties of thermoplastic polymers?
Thermoplastic polymers are lightweight, moldable, chemically resistant materials that soften on heating and harden on cooling.
- Good impact resistance and flexibility.
- Low to moderate melting points.
- Electrical and thermal insulation properties.
- Recyclable and easy to process by extrusion or injection molding.
Their properties depend on molecular weight, degree of branching, and crystallinity.
8. What are the uses of thermoplastic polymers?
Thermoplastic polymers are used in packaging, construction, automotive parts, textiles, and consumer goods due to their versatility and recyclability.
- Packaging: bottles, films, containers (PE, PET).
- Construction: pipes and fittings (PVC).
- Automotive: dashboards and bumpers (PP).
- Textiles: polyester fibers.
Their ease of molding and cost-effectiveness make them essential in modern industry.
9. What is the difference between linear and branched thermoplastic polymers?
Linear thermoplastic polymers have straight chains, while branched thermoplastics have side chains attached to the main backbone.
- Linear polymers: Pack closely, higher density, higher tensile strength (e.g., HDPE).
- Branched polymers: Less closely packed, lower density, more flexible (e.g., LDPE).
The degree of branching affects density, melting point, and mechanical properties.
10. Can you give an example of a thermoplastic polymerization reaction?
An example of thermoplastic polymerization is the formation of polyethylene from ethene by addition polymerization.
- Monomer: CH2=CH2 (ethene).
- Reaction: nCH2=CH2 → (–CH2–CH2–)n
- The double bond opens and links with other monomers to form a long chain.
The product, polyethylene, is a widely used thermoplastic polymer in packaging and household items.
