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Synthetic Fibers and Plastics

Learning Objectives

• Identify synthetic fibers and plastics and distinguish them from natural materials.

• Name common synthetic fibers such as nylon, polyester, acrylic, and rayon.

• Describe the properties of synthetic fibers and plastics.

Success Criteria

• Compare synthetic and natural fibers based on their properties and uses.

• Explain why specific plastics are used for particular purposes.

• Identify the advantages and disadvantages of synthetic materials.

• Recognize and classify different synthetic fibers and types of plastics.

Index

• Fibers
    - Types of Fibers
    - Monomers and Polymers
    - Polymerization

• Polymers may be natural or synthetic

• Plastic Products

• Raw Materials for Synthetic

Types of Fibers

Natural Fibers

• Source: Derived from natural sources like plants (e.g., cotton, linen) and animals (e.g., wool, silk).

Synthetic Fibers

• Definition: Man-made fibers created through chemical processes.
    - Properties:
      - Typically longer and more durable than natural fibers.
      - Limitations: Poor moisture absorption and high flammability.

Monomers and Polymers

• Monomer: A single unit that combines to form larger molecules.

• Polymer: A large molecule composed of many repeating units called monomers.

• Polymerization: The process by which monomers join to form polymers under specific conditions of temperature and pressure.

Examples of Polymers

Natural Polymers

• Natural fibers (e.g., cotton, wool, and silk).
    - Cotton: A polymer made from glucose.
    - Wool and Silk: Polymers made from amino acids (proteins).
    - Spider Silk: Notable for being one of the strongest natural polymers.

Synthetic Polymers

• Definition: Made from chemical substances, typically plastics.

• Examples: Nylon, polyester
    - Monomer Source:
      - Ethylene (chemical formula: $C_2H_4$), derived from petroleum, polymerizes into polyethylene.
      - Nylon’s monomers: amine and adipic acid.

Synthetic Fibers

Rayon

• Source: Prepared from cellulose, converted using chemicals; hence considered semi-synthetic.
    - Advantages: Cheaper than cotton; can be blended with other fibers (e.g., wool, silk).
    - Properties: Lustrous, good absorbent, drapes well.
    - Uses:
      - Helmets (mixed with fiberglass)
      - Upholstery and drapes
      - Soft dress materials.

Nylon

• Inventor: Wallace H. Carothers (1935).

• Type: A polyamide (synthetic polymer).
    - Properties: Tough, elastic, resistant to oil, diverse uses.
    - Uses: Stretchable wears, ropes, nets, and furnishings.

Polyester

• Definition: Synthetic fibers created from the reaction of alcohol with organic acids to form esters.
    - Brands: Terylene, Dacron, Terene.
    - Properties: Dries quickly, resistant to chemicals, maintains crease.
    - Uses: Fabrics for clothing, magnetic storage media, hulls for boats.

Acrylic

• Common names: Acrilan, Orlon, Creslan, Zefran.
    - Properties: Soft, warm, durable, and easy to dye.
    - Uses: Baby wear, artificial fur, surgical tools covering.

Lycra (Spandex)

• Description: Extremely elastic, stretches up to 600% and returns to original shape.
    - Uses: Stage clothing, swimsuits, t-shirts.

Advantages of Synthetic Fibers

1. Strength: High tensile strength—able to withstand significant weight.

2. Low Water Absorption: Dries quickly in sunlight.

3. Good Elasticity: E.g., used in socks.

4. Wrinkle Resistance: Maintains shape well.

5. Durability: Resistant to abrasion.

6. Moth Resistance: Protects against pests.

7. Lightweight: Easy to wear.

8. Inertness: Chemically non-reactive.

Disadvantages of Synthetic Fibers

1. Flammability: Melt and burn easily.

2. Non-biodegradable: Environmental impact.

3. Comfort: Can be uncomfortable in hot weather.

4. Skin Issues: Develop static electricity, potential skin diseases like eczema.

Types of Plastics

Thermosetting Plastics

• Characteristics: Hard, rigid, cannot be remolded.
    - Examples: Bakelite and melamine.
    - Uses: Kettle handles, electrical components.

Thermoplastics

• Characteristics: Soft, flexible; can be melted and reshaped.
    - Examples: Nylon, PVC, polyethylene.
    - Uses: Household items, toys, containers, cutlery.

Properties of Plastics

• Corrosion Resistance: Durable over time.

• Heat Tolerance: Resists high temperatures.

• Electrical Insulation: Non-conductive properties.

• Recyclable: Certain plastics can be reused.

• Water Resistant: Does not react with water.

Environmental Concerns

• Plastics and Pollution: Non-biodegradable, causing ecosystem harm.
    - Innovations: Biopolymers developed for better environmental compatibility.
    - Solutions: 5-R principle (Refuse, Reduce, Reuse, Recycle, Recover).

Critical Thinking Questions

• If you were a clothing designer, how would you minimize the disadvantages of synthetic fibers?

• Choose between a plastic or steel lunch box and justify your choice.

• Experiment Design: Use a "Burn Test" to differentiate between natural, synthetic, or semi-synthetic fibers based on flame characteristics.