Understanding Thermoplastic Polymers

Thermoplastic polymers are a class of polymers that can be repeatedly heated to soften and molded, and then cooled to solidify. This process can be repeated many times without significant degradation of the polymer properties, unlike thermosetting polymers which undergo irreversible chemical changes upon heating.

Analyzing Statements about Thermoplastic Polymers

Let's examine each statement provided in the options to determine which one is incorrect regarding thermoplastic polymers.

• Statement 1: These are linear on branched linear polymers.

  Thermoplastic polymers typically have linear or branched chain structures. These structures allow the polymer chains to slide past each other when heated, leading to softening. This statement is characteristic of thermoplastic polymers.

  Therefore, this statement is correct.

• Statement 2: Poly vinyl chloride (PVC) is an example of thermoplastic polymer.

  Poly vinyl chloride (PVC) is a common example of a thermoplastic polymer. It is widely used in pipes, window frames, flooring, and cables due to its ability to be molded into various shapes upon heating.

  Therefore, this statement is correct.

• Statement 3: They cannot be repeatedly soften under heating and harden on cooling.

  This statement claims that thermoplastic polymers cannot be repeatedly softened by heating and hardened by cooling. This contradicts the fundamental definition and behavior of thermoplastic polymers. The ability to undergo this reversible softening and hardening process upon heating and cooling is precisely what defines a thermoplastic polymer.

  Therefore, this statement is incorrect.

• Statement 4: They can be reshaped and recycled.

  Because thermoplastic polymers can be repeatedly softened by heating and solidified by cooling, they can be easily reshaped and recycled. This is a significant advantage of thermoplastics compared to thermosetting polymers.

  Therefore, this statement is correct.

Identifying the Incorrect Statement

Based on the analysis, the incorrect statement about thermoplastic polymers is the one claiming they cannot be repeatedly softened under heating and hardened on cooling. This property is the defining characteristic that allows them to be molded and recycled.