Question

Identify the correct statement(s) about thermoplastics from among the following (a) They can be remelted and remoulded many times by heating and cooling. (b) The intermolecular forces in thermoplastics are weaker than those present in elastomers. (c) There are no cross links between polymeric chain. (d) Neoprene is a thermoplastics polymer.

Short answer

Question: Identify the correct statement(s) about thermoplastics among the given options. Options: a) They can be remelted and remoulded many times by heating and cooling. b) The intermolecular forces in thermoplastics are weaker than those present in elastomers. c) There are no cross links between polymeric chains. d) Neoprene is a thermoplastics polymer. Answer: a) and c) are the correct statements about thermoplastics.

Step-by-step solution

Understand thermoplastics properties

Thermoplastics are a type of polymer that can be heated, melted, and molded multiple times without undergoing any significant change to its properties. They have no cross-links between their polymer chains, which allows them to be remolded when heated.

Compare thermoplastic properties to elastomers

Elastomers are a category of polymers with elastic properties. Their intermolecular forces are weaker than those of thermoplastics, allowing them to be stretched and deformed but return to their original shape when the force is removed.

Analyze given statements (a) and (c)

Statement (a) says, "They can be remelted and remoulded many times by heating and cooling," which aligns with the properties of thermoplastics. Statement (c) claims that "There are no cross links between polymeric chains," which is also true for thermoplastics.

Check statement (b)

Statement (b) claims that "The intermolecular forces in thermoplastics are weaker than those present in elastomers." This statement is incorrect because the intermolecular forces in thermoplastics are stronger than those in elastomers, as mentioned earlier.

Examine statement (d) and Neoprene

Statement (d) states that "Neoprene is a thermoplastics polymer." Neoprene is a synthetic rubber and is classified as an elastomer, not a thermoplastic.

Conclusion

Based on the analysis of the given statements, the correct statements about thermoplastics are (a) and (c). The other two statements (b) and (d) are incorrect.

Key concepts

Polymer Chemistry

Polymer chemistry is a branch of science that focuses on the study and manipulation of polymers, which are long, repeating chains of molecules. These chains are made up of smaller units called monomers that have been chemically bonded together.

Thermoplastics, a central topic in polymer chemistry, are polymers that become soft and moldable upon heating and solidify upon cooling. This process is reversible, and it can be repeated many times without altering the polymer's inherent properties. This characteristic is due to the lack of cross-linking between the polymer chains, allowing them to slide past one another when heated, making them moldable.

Understanding the chemical structure of polymers enables us to predict and explain the behaviors and properties of different types of plastics, such as their melting points, strength, and flexibility. This understanding is crucial in developing new materials and recycling existing ones, contributing to various fields, from packaging to biomedical engineering.

Intermolecular Forces in Polymers

Intermolecular forces are non-covalent attractions between molecules, including those in polymers, and these forces play a significant role in determining a polymer's properties.

Types of Intermolecular Forces

In polymers, the primary intermolecular forces include van der Waals forces, hydrogen bonding, and dipole-dipole interactions.

• Van der Waals forces are weak attractions that are significant in polymers with nonpolar monomers.
• Hydrogen bonds occur when a hydrogen atom is attracted to an electronegative atom, like oxygen or nitrogen, and are stronger than van der Waals forces.
• Dipole-dipole interactions occur between polar molecules, where positive and negative charges attract.

These intermolecular forces affect how polymers behave under stress and heat. Stronger intermolecular forces typically make a polymer more rigid and less flexible, as is the case with many thermoplastics. In contrast, weaker intermolecular forces allow a polymer to stretch and recover, as seen in elastomers. The manipulation of these forces can lead to the design of polymers with specific characteristics for targeted applications.

Elastomers vs Thermoplastics

The distinction between elastomers and thermoplastics is crucial as it pertains to their application in design and manufacturing. Elastomers are polymers that can stretch extensively and return to their original shape, a property that is highly valued in products that need to be flexible or undergo regular deformation, like tires and rubber bands. This elastic behavior is due to their loosely cross-linked molecular structure and relatively weak intermolecular forces, which allow the molecules to move relative to one another easily.

Thermoplastics, on the other hand, have a more orderly structure and stronger intermolecular forces, which become temporary when heated, allowing them to be molded. Upon cooling, these forces solidify, setting the polymer into a rigid and stable form. This quality makes thermoplastics ideal for items that require a defined shape that can be produced repeatedly, like containers and tech device housings.

Choosing between an elastomer and a thermoplastic depends on the requirements of the application. Elastomers are favored for their flexibility and resilience, while thermoplastics are preferred for their stability and reshaping capability. Understanding the difference between these materials is fundamental for engineers and product designers in bringing forth innovative solutions in various industries.