Polymer Types, Properties and Polymerization Processes

Polymer Concepts and Terminology

1. What is a homopolymer?

Homopolymer: It is called a homopolymer when monomer molecules of a single type combine to form polymer molecules. If two or more different types of monomers are involved, the resulting material is called a copolymer.

2. What is polymerization?

Polymerization is the process by which polymers are formed from monomers. The term names the process of forming polymer chains from monomer units.

3. What does T represent in load–deformation phenomena?

The symbol T refers to the ambient temperature. Temperature affects the load–deformation behavior of thermoplastic polymers.

4. What does aging of polymers consist of?

Aging of polymers results from atmospheric and environmental factors and affects the loss of properties over time.

5. What is calendering?

Calendering is a process in which the material is passed between heated rollers; it is used to produce sheets by pressing and heating the plastic as it passes through the rollers.

6. What plastic is known by the trade name Delrin?

The trade name Delrin refers to polyacetals, commonly known as POM (polyoxymethylene).

7. What type of plastic is PET and its common applications?

PET (polyethylene terephthalate) is a technical thermoplastic and belongs to the family of saturated polyesters. Applications include:

• sheet extrusion
• coextrusion
• injection molding
• blow molding
• thermoforming and thermal treatments

8. What are high-performance plastics?

High-performance plastics are characterized by exceptionally good mechanical properties and the ability to withstand loads for extended periods (in some cases, indefinitely under proper conditions). They are often obtained by polymerization of monomers in which benzene (aromatic) rings are incorporated into the polymer chain, increasing thermal and mechanical stability.

9. Types of polymerization

Polymerization can be classified mainly into two types:

• Addition (chain-growth) polymerization: Formed from monomers without the loss of small molecules. The repeating structural unit has the same composition as the starting monomer.
• Condensation (step-growth) polymerization: Formed from polyfunctional monomers through various reactions accompanied by the elimination of small molecules, such as water.

10. Thermomechanical characterization of polymers

The thermomechanical properties of polymers vary with temperature and are commonly described using three key temperatures:

1. Glass transition temperature (Tg)
2. Melting temperature (Tm)
3. Decomposition temperature (Td)

Different types of polymers can be considered in terms of elastic modulus (E) as a function of temperature, for example: amorphous thermoplastics, semi-crystalline thermoplastics, and thermosetting plastics.

11. What is an isochrone?

An isochrone is a curve on a diagram used to perform calculations often referred to as pseudostatic analysis for parts subjected to prolonged stresses over time. Isochrones help determine behavior and deformation limits when parts are exposed to sustained loads.