Describe the effect of temperature (Tg and Tm) on polymer applications for crystalline andamorphous polymers. (6 marks)

Effect on Amorphous Polymers: Amorphous polymers do not have a sharp melting point (Tm), but they do have a glass transition temperature (Tg). Below Tg, amorphous polymers are in a glassy state and are brittle. As the temperature increases past Tg, the polymer transitions into a rubbery state, becoming more flexible and ductile. This transition affects the mechanical properties of the polymer, such as its hardness, strength, and elasticity. Therefore, the application of amorphous polymers is highly dependent on their Tg. For example, if the application requires a hard and brittle material, an amorphous polymer with a high Tg would be suitable.

Effect on Crystalline Polymers: Crystalline polymers have both a Tg and a Tm. Below Tg, they behave similarly to amorphous polymers. However, between Tg and Tm, crystalline polymers are in a semi-crystalline state. They have regions of ordered, crystalline structures and regions of disordered, amorphous structures. This gives them a unique combination of properties, such as good mechanical strength and toughness, and makes them suitable for a wide range of applications. As the temperature increases past Tm, the crystalline regions melt and the polymer becomes a viscous liquid. This property is utilized in applications such as injection molding, where the polymer is heated to a liquid state, injected into a mold, and then cooled to solidify in the desired shape.

Overall, the temperature (Tg and Tm) greatly influences the properties and applications of both amorphous and crystalline polymers. By carefully selecting a polymer with the appropriate Tg and Tm, engineers can design materials with specific properties to meet the requirements of various applications.