Introduction to Polymer Materials
This page collects short reference notes on polymer structure, processing, and common material properties. It was prepared for basic course use and for quick lookup during laboratory sessions.
A polymer is a large molecule made from repeating units called monomers. The final material behavior depends on the monomer chemistry, chain length, branching, crystallinity, additives, and the way the polymer was processed.
Common Polymer Classes
| Thermoplastics | Soften when heated and can usually be reshaped. Examples include PE, PP, PS, PVC, PMMA, and PET. |
|---|---|
| Thermosets | Form cross-linked networks during curing and do not melt again. Epoxy and phenolic resins are common examples. |
| Elastomers | Flexible network materials with rubber-like recovery, such as natural rubber, SBR, silicone rubber, and neoprene. |
| Biopolymers | Polymers made by biological systems or derived from renewable sources, including cellulose, starch, PLA, and proteins. |
Key Terms
- Degree of polymerization: the average number of repeat units in a chain.
- Glass transition temperature: the temperature region where amorphous segments become more mobile.
- Crystallinity: ordered packing of polymer chains, often increasing stiffness and chemical resistance.
- Cross-linking: chemical bridges between chains that increase dimensional stability.
- Plasticizer: an additive used to increase flexibility by reducing intermolecular forces.
Processing Notes
Polymer parts are often produced by extrusion, injection molding, blow molding, compression molding, casting, fiber spinning, or film blowing. Processing temperature and cooling rate can strongly influence shrinkage, surface finish, crystallinity, and residual stress.
Laboratory samples should be labeled with material code, batch number, drying conditions, processing temperature, and cooling method. Moisture-sensitive polymers such as PET, PA, PC, and some biodegradable polyesters should be dried before melt processing.
Typical Observation Checklist
- Record visual appearance: transparent, translucent, opaque, glossy, or matte.
- Check flexibility and recovery after light bending.
- Note odor, surface marks, bubbles, discoloration, and weld lines.
- Compare density by water float test where appropriate.
- Store heat-treated samples separately from untreated controls.
Notice: This mirror is maintained for internal reference only. Some links may be unavailable while old course material is being transferred from the laboratory server.