Polymer Science Quiz

Study Notes

MMET 206 Lecture Notes 4: Polymers

Polymers are substances composed of large molecules with repeating structural units (monomers) connected by covalent bonds.
Synthetic polymers are artificially created via chemical synthesis, not derived from natural sources.
Examples of synthetic polymers include fibers (aramid, Nomex, Kevlar, nylon, polyester), plastics (acrylics, PET, styrene butadiene), elastomers (rubbers), protective coatings (paint, varnish), and adhesives (cyanoacrylates).
Crude oil and natural gas are natural resources used to produce polymers.
Crude oil is a mixture of various hydrocarbons (HCs) with varying molecular sizes.
Part 1 of the lecture focuses on Crude Oil/Monomers, outlining its composition and preparation.
- Refining crude oil by fractional distillation breaks it into various hydrocarbon fractions.
- Cracking breaks larger HCs to smaller ones, including producing monomers.
Part 2 (Step 3) details Polymerization/Polymers, the process connecting monomers into a polymer.
- This step uses polymerization processes such as addition (chain growth) and condensation (step growth).
Polymerization methods:
- Addition Polymerization (Chain Growth): This process involves rapid reactions between chemically active monomers to form long-chain polymers.
- Condensation Polymerization (Step Growth): This process involves the individual chemical reactions between pairs of reactive monomers, often with water as a byproduct, and results in a slower polymerization process.
Part 3 focuses on Synthetic Fibers.
- Polyester (PET) — used in fibers for curtains, dress fabrics, and fillers for various products.
- Polyamide (PA, aramid fibers)— includes Nomex and Kevlar, known for heat resistance use in space shuttles, fire protection gear, and race cars.
- Polyacrylonitrile (PAN, acrylic fibers)— synthetic fibers having a wool-like feel, commonly used for sweaters, hats, and rugs.
Part 4 focuses on Plastics.
- Thermoplastics— materials that can be repeatedly heated and reshaped. They include:
  - Commodity Plastics: Common-use plastics (PET, HDPE, PVC, LDPE, PP, PS).
  - Engineering Plastics: Specialized plastics with superior mechanical properties and used in engineering applications(e.g., nylon).
  - Plastic Alloys: These are mixtures of two or more polymers, which can enhance specific properties.
  - Thermosets: Materials that undergo irreversible changes and form strong, permanent crosslinks during curing, making them non-recyclable. They include Phenolics (PF), Amino Plastics (UF, MF), Unsaturated Polyesters (UP), Vinyl Esters (VE), Epoxies (EP), Thermoset Polyimides (PI), and Polyurethane (PU or PUR).
Part 5 focuses on Rubbers (aka Elastomers) and their properties.
- Types of synthetic rubbers include polyisoprene (IR), butadiene rubber (BR), nitrile rubber (NBR), styrene butadiene rubber (SBR), chloroprene/neoprene rubber (CR), butyl rubber (IIR), silicone rubber (SI), and ethylene propylene diene monomer (EPDM) rubber.
  - Rubber aging or degradation due to weather cracking is mainly caused by direct sunlight, UV light, and heat.
- Different applications of these types of rubbers include:
  - Tire components.
  - Car weather seals.
  - Protective equipment.
- Thermoplastic rubbers are also described.

Other Key Concepts

Degree of Polymerization (DP): The average number of repeating units in a polymer molecule, significantly influencing properties.
Crystallinity of Polymers: Polymers can have crystalline regions, amorphous regions, or mixtures of both.
Glass Transition Temperature (Tg): The temperature at which amorphous polymers change from a hard, brittle state to a rubbery state.
Additives: Substances added to polymers to modify or enhance properties.
Manufacturing Processes: Common methods for making plastic products include injection molding, extrusion, blow molding, cast film extrusion, vacuum thermoforming, and rotation molding.