Thermoplastic Polymers

Dhristi JEE 2022-24

All You Need to Know About Thermoplastics

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

Homo Polypropylene

Co Polypropylene

The strength to weight ratio of the homo polypropylene is high.

The strength to weight ratio of the co polypropylene is low.

These types of polypropylene are harder and stronger.

These types of polypropylene are softer and weaker.

Homo polypropylene has high impact resistance.

Co polypropylene has low impact resistance.

It is acceptable for food contact applications.

It is not acceptable for food contact applications.

It is suitable for making corrosion-resistant structures.

Co polypropylene is not used for making corrosion-resistant structures.


Types of Polypropylene Films 

  1. 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.

  1. 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.

  1. 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

1. What are thermosets?

The polymers which undergo chemical changes and crosslinking on heating and become permanently hard rigid and infusible are known as thermosets. Once they are set, they will not become soft on heating. Thermosets are mostly formed by condensation polymerization and are mostly branched polymers which change with potential to form a three dimensional structure. In the common organic solvents, thermosets are not soluble. Thermosets exhibit their characteristic properties of nauvin softening and non swelling nature, hardness and brittleness. They cannot be softened, reshaped or reformed once they are set and cannot be reclaimed from wastes

2. What are the uses of thermoplastics?

Thermoplastics are used for making solutions of electric wires and cables, various types of plastic containers (plastic bottles, plastic jar extra), combs, toys, plastic bags, raincoats, seat covers, bristles of the electric car, brushes, packaging materials and chairs.


They are also used for making insulation of electric wires because they do not conduct electricity and are flexible.

3. What are the uses of thermosetting plastics?

The thermosetting plastics are being used for making the handles of the cooking utensils for example pressure cooker, frying pan etc because they do not soften on getting heated and also they are the non-conductors of heat. They are used for making electrical fittings such as electrical boards and sockets because they do not conduct electricity and do not become soft on getting heated.

4. Explain the difference between thermoplastics and thermosetting plastics?

We can tell whether a given plastic is thermoplastic or thermosetting plastic from the way it behaves on heating. If a given plastic article softens on heating then it will be a thermoplastic. On the other hand, if the plastic article which was given does not become soft by heating it, then it will be a thermosetting plastic. Moreover, thermoplastics are flexible and can be bent whereas thermosetting plastics are very hard rigid which cannot be bent at all. By this, we mean that the handle of a toothbrush should be made of thermosetting plastic whereas its bristles should be made of thermoplastic. Please note that the articles made from thermoplastics can be recycled whereas the articles made of thermosetting plastics cannot be recycled.

5. Define Thermoplastic.

Thermoplastic is a type of plastic polymer that can be molded at high temperatures but solidifies when cooled. Thermoplastic, also known as thermosoftening polymer, is a type of thermoplastic.

6. Write Five Characteristics of Thermoplastic.

Five characteristics of thermoplastic are:

  • Thermoplastics are polymers with a high molecular weight.

  • The intermolecular forces are related to the chains in the polymer.

  • If the temperature rises, the intermolecular force acting between the chains weakens, resulting in a viscous liquid.

  • These polymers have the ability to be reshaped.

  • These polymers differ from thermosetting polymers in that when dried, thermosetting polymers do not melt.

  • Thermoplastics are naturally recyclable.

  • There are high-strength polymers that are lightweight.

  • They have a flame-retardant effect.

7. Give Three Thermoplastic Examples.

Three examples of thermoplastics are polystyrene, polyvinyl chloride, and polypropylene.

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