Processing of Materials – Plastics and Rubber

Subject: Basic Technology
Class: JSS 3
Term: First Term
Week: 8
Age: 12-15 years
Topic: Processing of Materials – Plastics and Rubber
Sub-topic: Methods of Processing and Uses
Duration: 60 minutes

Behavioural Objectives

By the end of the lesson, students should be able to:

1. Define plastics and rubber.
2. Explain the methods used in processing plastics and rubber.
3. Identify the uses of plastics and rubber in daily life.
4. Differentiate between thermoplastics and thermosetting plastics.

Keywords

• Plastics
• Rubber
• Thermoplastics
• Thermosetting plastics
• Vulcanization
• Injection molding

Set Induction

The teacher displays various plastic and rubber products such as bottles, buckets, erasers, and tires and asks students to mention how they think these items are made.

Entry Behaviour

Students are familiar with common plastic and rubber products like water bottles, erasers, and shoes.

Learning Resources and Materials

• Plastic and rubber products (e.g., bottles, shoes, tires)
• Charts or videos showing plastic and rubber production processes

Building Background/Connection to Prior Knowledge

In previous lessons, students learned about the processing of wood and ceramics. Now they will explore how plastics and rubber—materials widely used in daily life—are processed and utilized.

Embedded Core Skills

• Critical thinking and problem-solving
• Observation skills
• Practical application of material science

Learning Materials

• Real-life plastic and rubber objects
• Diagrams of plastic injection molding and rubber vulcanization processes

Reference Books

• Lagos State Scheme of Work
• Basic Technology for Junior Secondary Schools
• Materials Processing Handbook by T. Adetunji

Instructional Materials

• Plastic bottles, rubber erasers, car tires
• Visual aids showing production steps
• Video clips demonstrating processing techniques

Content

I. Definition of Plastics and Rubber

• Plastics: Synthetic materials made from polymers that can be molded into different shapes.
• Rubber: A flexible, elastic material obtained from natural or synthetic sources, used for various applications.

II. Types of Plastics

1. Thermoplastics: Plastics that soften when heated and can be reshaped. Examples: Polyethylene, PVC.
2. Thermosetting Plastics: Plastics that harden permanently after being heated once. Examples: Bakelite, Epoxy resin.

III. Methods of Processing Plastics

1. Injection Molding:
   • Plastic is melted and injected into a mold to form the desired shape.
   • Used to make bottles, containers, and buckets.
2. Extrusion:
   • Molten plastic is forced through a die to produce continuous shapes like pipes.
3. Blow Molding:
   • Used for making hollow plastic products like bottles by blowing air into molten plastic inside a mold.
4. Thermoforming:
   • Plastic sheets are heated and shaped over a mold.
5. Recycling:
   • Plastic waste is melted and reused to create new products.

IV. Methods of Processing Rubber

1. Tapping:
   • The process of extracting latex from rubber trees.
2. Molding:
   • Rubber is poured into molds to take specific shapes, such as erasers.
3. Vulcanization:
   • Heating raw rubber with sulfur to make it stronger and more elastic. This is used to produce tires and rubber belts.
4. Extrusion:
   • Rubber is forced through a die to form continuous shapes like tubes or hoses.
5. Recycling:
   • Old rubber products, such as tires, are shredded and reused for new purposes like floor mats.

V. Uses of Plastics and Rubber

Uses of Plastics

1. Bottles, bags, and containers for packaging.
2. Pipes and fittings for water systems.
3. Electrical insulators for wiring.
4. Furniture, toys, and household items.
5. Medical devices such as syringes.

Uses of Rubber

1. Tires for vehicles.
2. Rubber belts and hoses in machinery.
3. Shoes and sandals.
4. Erasers and rubber bands.
5. Seals and gaskets in engines and machines.

Evaluation (Fill-in-the-Blank Questions)

1. __________ is a process used to make plastic bottles.
   (a) Injection molding (b) Extrusion (c) Vulcanization (d) Tapping
2. __________ plastics can be reshaped by heating.
   (a) Thermosetting (b) Thermoplastics (c) Synthetic (d) Natural
3. Vulcanization involves heating rubber with __________.
   (a) sulfur (b) clay (c) silica (d) plastic
4. A __________ is used to shape molten plastic into continuous forms.
   (a) mold (b) die (c) kiln (d) lathe
5. __________ is a natural source of rubber.
   (a) Latex (b) Resin (c) Silica (d) Wood
6. __________ is a plastic product used in packaging drinks.
   (a) Eraser (b) Pipe (c) Bottle (d) Tire
7. The process of extracting latex from rubber trees is called __________.
   (a) tapping (b) molding (c) recycling (d) glazing
8. __________ plastics harden permanently after heating.
   (a) Thermoplastics (b) Vulcanized (c) Thermosetting (d) Laminated
9. Old tires can be __________ to make floor mats.
   (a) recycled (b) vulcanized (c) molded (d) tapped
10. Shoes and sandals are examples of products made from __________.
    (a) rubber (b) plastic (c) glass (d) ceramic

Class Activity Discussion (FAQs)

1. What is the difference between thermoplastics and thermosetting plastics?
   Thermoplastics can be reshaped by heating, while thermosetting plastics harden permanently.
2. What is injection molding?
   It is a process where molten plastic is injected into molds to create shapes.
3. What is vulcanization?
   It is the process of heating rubber with sulfur to improve its strength and elasticity.
4. How is latex collected?
   Latex is collected from rubber trees through tapping.
5. Can plastics be recycled?
   Yes, many plastic items can be melted and reshaped into new products.
6. What are the uses of rubber?
   Rubber is used to make tires, shoes, belts, and erasers.
7. Why are plastic pipes used in plumbing?
   They are lightweight, durable, and resistant to corrosion.
8. What is the role of sulfur in vulcanization?
   Sulfur makes rubber more elastic and durable.
9. Can rubber products be recycled?
   Yes, old tires and other rubber items can be shredded and reused.
10. What are the environmental concerns with plastic waste?
    Plastic waste takes a long time to decompose, leading to pollution.

Teacher’s Activities

1. Demonstrate the production methods using diagrams or videos.
2. Show examples of plastic and rubber products.
3. Facilitate discussions on the uses and recycling of these materials.

Learners’ Activities

1. Identify and describe different plastic and rubber products.
2. Participate in discussions about the production processes.
3. Complete the evaluation questions.

Evaluation Questions

1. Define plastics and rubber.
2. Explain the process of vulcanization.
3. What is injection molding?
4. List three uses of plastic.
5. Mention two products made from rubber.
6. What are thermoplastics?
7. How is latex obtained?
8. Name the materials used in blow molding.
9. What are the benefits of recycling plastic?
10. Differentiate between molding and extrusion.

Conclusion

The teacher checks students’ understanding by reviewing their answers and provides necessary corrections.