Synthetic Fibres and Plastics - Quick Review
Polymer Basics
Synthetic fibres are polymers; a polymer is a long chain formed by joining many monomer units.
Monomer: a small repeating unit.
Polymerisation: the process of linking monomers to form a polymer.
Analogy: beads on a string resemble polymer chains.
Key terms:
\text{polymer} = \text{poly} + \text{mer}
\text{poly} = \text{many}, \quad \text{mer} = \text{unit}
Example: \text{polyethylene} = \text{polymer of ethylene};\text{ many ethylene units polymerise to form polyethylene}.
Monomers can join linearly (linear polymerisation) or cross-linked (cross-linked polymerisation).
Synthetic fibres are man-made polymers derived from petroleum/natural gas by-products, produced in plants or labs.
Types of Polymerisation
Linear polymerisation: monomers join end-to-end to form a chain.
Cross-linked polymerisation: monomers link to form a network structure, yielding rigid polymers.
Synthetic Fibres: Overview
Main types: Rayon, Nylon, Polyester, Acrylic.
Rayon
Semi-synthetic fibre; made from cellulose (wood pulp).
Resembles silk; absorbs moisture; easy to dye.
Used in apparels, home furnishings, tyre cords, carpets, surgical dressings.
Nylon
Made from coal, petroleum, water, air.
High tensile strength; resists wrinkling; low water absorption; elastic and durable.
Uses: toothbrush bristles, carpets, ropes, parachutes.
Polyester
Polymer of ester units; includes Terylene.
Very strong, durable; chemical resistant; dries quickly; does not absorb water.
Highly flammable; used for clothes, ropes, PET bottles; microfibres are extremely fine.
InfoBits: Polyester and nylon microfibres are about 60-100\times finer than a strand of hair.
Acrylic
Substitute for wool; warm, wrinkle-resistant, easy to wash.
Soft, durable; resistant to moths, oils, chemicals; sun-stable.
Used in sweaters, tracksuits, linings, furnishings; also called Orlon/Acrilon.
Can be blended with other fibres.
Blending Fibres
Blended fabrics combine two or more fibres to improve properties.
Benefits: improve comfort, crease-resistance, durability, or cost.
Examples:
Terylene + cotton = terrycot (dress materials).
Terylene + wool = terrywool (substitute for wool).
Cotton + Lycra = more comfortable/stretchy jeans.
Acrylic + wool = cheaper warm garments.
Identifying the Type of Fibre (Burning Test) – Quick Idea
Burning test helps identify fibres by observing burn rate, flame type, smell, and residue.
Typical tendencies (summary):
Cellulosic fibres (cotton, rayon): ignite readily; odor like burning paper; leave ash.
Protein fibres (silk, wool): may resist ignition; char; odor like burnt hair.
Synthetic fibres (nylon, polyester): may melt/bead; sometimes self-extinguish; distinctive odors.
Acrylic: burns with a yellow flame; may melt/bead; characteristic smell.
Conclusion: burning test aids quick fibre identification.
Properties of Synthhetic Fibres (Key Pros/Cons)
Advantages
High tensile strength; strong under load.
Low wrinkling; retains shape; easy to wash and wear.
Soft and stretchy; durable; readily available.
Generally less expensive than many natural fibres.
Disadvantages
Poor moisture absorption; uncomfortable in hot/sweaty conditions.
Can be fire hazards; melt easily; ironing can be difficult.
Plastics: What they Are and Why They’re Ubiquitous
Plastic: a synthetic polymer that can be moulded or shaped; property called plasticity.
Used in packaging, building, furniture, toys, insulation, pipes, hoses, electronics, etc.
Common plastics: Polythene, PVC, Bakelite, PET, polystyrene, Teflon.
Classification of Plastics
Thermoplastics: soften on heating and can be remoulded; polymer chains lie side by side; easy to heat and remould.
Examples: Polythene (PE), Polyvinyl chloride (PVC).
Thermosetting plastics: cannot be softened/remoulded on heating after setting; cross-linked bonds make them hard and brittle.
Examples: Bakelite, Melamine.
Why Plastics Are So Useful
Properties:
Light weight; strong; durable.
Chemical and water resistance; safe packaging.
Poor thermal and electrical conductivity; good insulators.
Limitations:
Some are highly flammable and melt under heat.
Non-biodegradable; disposal and environmental concerns.
Uses of Plastics (Representative Examples)
Polythene: packaging liquids (thermoplastic).
PET: bottles and microwave-safe containers.
Polystyrene: electronics and insulation.
PVC: plumbing pipes, flooring, upholstery.
Bakelite: electrical fittings (thermosetting).
Teflon: non-stick coatings.
Plastics and the Environment
Non-biodegradable: do not decay easily by natural processes.
Disposal concerns include:
Toxic fumes when burnt.
Accumulation in water bodies; habitat and health impacts.
Impedes sewage disposal; soil and plant growth issues when buried.
Solutions: the 4Rs
Reduce, Reuse, Recycle, Recover.
Separate biodegradable from non-biodegradable waste.
Thermoplastics are easier to recycle.
Avoid disposal in drains and water bodies.
Word Bytes (Glossary – essential terms)
Synthetic fibres: fibres not derived from natural sources but artificially made.
Thermoplasts: plastics that can be remoulded by heating.
Monomer: small unit that joins to form a polymer.
Polymer: large molecule formed by joining monomers.
Polymerisation: process of joining monomers to form a polymer.
Plastics: synthetic or semi-synthetic polymers that can be shaped when soft and hardened into shape.
Thermosets: plastics that cannot be remoulded after setting.
Biodegradable: substances that decay by microorganisms.
Non-biodegradable: substances that do not decay by natural processes.
Quick Recap (Key Takeaways)
Fibres can be natural or synthetic; blending improves properties.
Plastics are versatile due to plasticity and varied polymer structures; classification into thermoplastics and thermosetting plastics is fundamental.
Environmental concerns with plastics center on non-biodegradability and disposal; the 4Rs provide a framework for mitigation.
Examples to remember:
Natural/fibres: cotton, wool, silk.
Synthetic/fibres: rayon (semi-synthetic), nylon, polyester, acrylic.
Plastics: PE, PVC (thermoplastics), Bakelite (thermosetting).
Brief Practice Prompts
Identify a thermosetting plastic from the common list.
Name a blended fibre and its constituent fibres.
State one advantage and one disadvantage of synthetic fibres.
Explain why plastics are widely used despite environmental concerns.
Note on Concepts for Exam
Distinguish between monomer, polymer, and polymerisation with simple definitions and examples.
Know differences between thermoplastics and thermosetting plastics and give at least one example of each.
Be able to name common synthetic fibres and one key property and use for each.
Understand the 4Rs approach to plastics management and why recycling of thermoplastics is often feasible.
Science Questions with Answers: Polymers and Plastics
What are synthetic fibres?
Answer: Synthetic fibres are polymers, which are long chains formed by joining many monomer units.
Define monomer and polymer.
Answer: A monomer is a small repeating unit. A polymer is a large molecule formed by joining many monomer units.
What is polymerisation?
Answer: Polymerisation is the process of linking monomers to form a polymer.
How is a polymer like polyethylene formed?
Answer: Polyethylene is a polymer of ethylene; many ethylene units polymerise to form polyethylene.
List the two main types of polymerisation.
Answer: The two main types are linear polymerisation and cross-linked polymerisation.
Briefly describe linear polymerisation.
Answer: In linear polymerisation, monomers join end-to-end to form a chain.
How does cross-linked polymerisation differ from linear polymerisation?
Answer: In cross-linked polymerisation, monomers link to form a network structure, yielding rigid polymers, unlike linear polymerisation which forms simple chains.
From what are synthetic fibres derived?
Answer: Synthetic fibres are man-made polymers derived from petroleum/natural gas by-products, produced in plants or labs.
Name the main types of synthetic fibres mentioned in the notes.
Answer: The main types are Rayon, Nylon, Polyester, and Acrylic.
Is Rayon a natural or synthetic fibre? Explain.
Answer: Rayon is a semi-synthetic fibre; it is made from cellulose (wood pulp), which is a natural source, but undergoes a chemical process.
List two properties and two uses of Rayon.
Answer: Properties: Resembles silk; absorbs moisture; easy to dye. Uses: Apparels, home furnishings, tyre cords, carpets, surgical dressings.
What are the raw materials used to make Nylon?
Answer: Nylon is made from coal, petroleum, water, and air.
Describe two key properties of Nylon.
Answer: High tensile strength; resists wrinkling; low water absorption; elastic and durable.
Give two applications of Nylon.
Answer: Toothbrush bristles, carpets, ropes, parachutes.
What is polyester a polymer of?
Answer: Polyester is a polymer of ester units.
Is Polyester flammable? What is one of its common uses?
Answer: Polyester is highly flammable. It is used for clothes, ropes, and PET bottles.
How fine are polyester and nylon microfibres compared to a strand of hair?
Answer: Polyester and nylon microfibres are about 60-100 imes finer than a strand of hair.
What natural fibre does Acrylic often substitute for?
Answer: Acrylic is a substitute for wool.
List two properties of Acrylic
Answer: Warm, wrinkle-resistant, easy to wash, soft, durable, resistant to moths, oils, chemicals, sun-stable.
What are some common applications of Acrylic?
Answer: Sweaters, tracksuits, linings, furnishings.
Why are blended fabrics created?
Answer: Blended fabrics combine two or more fibres to improve properties like comfort, crease-resistance, durability, or cost.
Give an example of a blended fabric and its constituent fibres.
Answer: Terrycot, which is a blend of Terylene and cotton; or terrywool, a blend of Terylene and wool.
How can a burning test help identify the type of fibre?
Answer: A burning test helps identify fibres by observing burn rate, flame type, smell, and residue.
What smell is typical when burning cellulosic fibres like cotton or rayon?
Answer: They ignite readily and have an odor like burning paper.
How do protein fibres (silk, wool) behave when subjected to a burning test?
Answer: They may resist ignition, char, and have an odor like burnt hair.
What are typical characteristics of synthetic fibres (nylon, polyester) during a burning test?
Answer: They may melt/bead, sometimes self-extinguish, and have distinctive odors.
What are three advantages of synthetic fibres?
Answer: High tensile strength; low wrinkling; retains shape; easy to wash and wear; soft and stretchy; durable; readily available; generally less expensive than many natural fibres.
What are two main disadvantages of synthetic fibres?
Answer: Poor moisture absorption (uncomfortable in hot/sweaty conditions); can be fire hazards (melt easily; ironing can be difficult).
What is plastic, and what property does it exhibit?
Answer: Plastic is a synthetic polymer that can be moulded or shaped; this property is called plasticity.
List three common uses of plastics.
Answer: Packaging, building, furniture, toys, insulation, pipes, hoses, electronics.
Name three common types of plastics.
Answer: Polythene, PVC, Bakelite, PET, polystyrene, Teflon.
Distinguish between thermoplastics and thermosetting plastics.
Answer: Thermoplastics soften on heating and can be remoulded, as their polymer chains lie side by side. Thermosetting plastics cannot be softened or remoulded on heating after setting, due to their cross-linked bonds which make them hard and brittle.
Give two examples of thermoplastics.
Answer: Polythene (PE), Polyvinyl chloride (PVC).
Provide two examples of thermosetting plastics.
Answer: Bakelite, Melamine.
List three reasons why plastics are considered useful.
Answer: Light weight; strong; durable; chemical and water resistance; safe packaging; poor thermal and electrical conductivity; good insulators.
What are the main limitations of plastics?
Answer: Some are highly flammable and melt under heat; they are non-biodegradable, leading to disposal and environmental concerns.
What is Polythene primarily used for? Is it a thermoplastic or thermosetting plastic?
Answer: Polythene is used for packaging liquids and is a thermoplastic.
What is Teflon known for in terms of its use?
Answer: Teflon is used for non-stick coatings.
Explain why plastics pose environmental concerns.
Answer: Plastics are non-biodegradable and do not decay easily. Their disposal leads to toxic fumes when burnt, accumulation in water bodies (impacting habitat and health), and issues with sewage disposal, soil, and plant growth when buried.
What are the 4Rs solutions for managing plastic waste?
Answer: Reduce, Reuse, Recycle, Recover.
Which type of plastic is easier to recycle, thermoplastics or thermosetting plastics?
Answer: Thermoplastics are easier to recycle.
Define, in your own words, Biodegradable and Non-biodegradable.
Answer: Biodegradable substances decay easily by natural processes and microorganisms. Non-biodegradable substances do not decay easily by natural processes.
What is the key difference between a monomer and a polymer?
Answer: A monomer is a small, repeating unit, while a polymer is a large molecule formed by the joining of many monomers.
Why is Bakelite classified as a thermosetting plastic?
Answer: Bakelite is a thermosetting plastic because it cannot be softened or remoulded after it has been heated and set, due to its cross-linked molecular structure.
How does blending fibres improve fabric properties? Give an example.
Answer: Blending fibres combines the desirable properties of different fibres. For example, blending Terylene with cotton to make terrycot improves crease-resistance and comfort.
Discuss the impact of non-biodegradable plastics on the environment, providing at least three specific issues.
Answer: Non-biodegradable plastics cause several environmental issues: they release toxic fumes when burnt, accumulate in water bodies leading to habitat and health impacts, and impede sewage disposal as well as soil and plant growth when buried.
Outline the essential steps in dealing with plastic waste to mitigate environmental damage.
Answer: The essential steps involve practicing the 4Rs (Reduce, Reuse, Recycle, Recover), separating biodegradable from non-biodegradable waste, recognizing that thermoplastics are easier to recycle, and