[Chemistry Class Notes] on Thermoplastic Polymers Pdf for Exam

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 

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.

2. 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.

3. 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.