Lesson Notes By Weeks and Term - Junior Secondary 3

Plastics and rubber



Class: Junior Secondary School 3

Age: 14 years

Duration: 40 minutes of 5 periods each




SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Identify the methods of production of plastics
  2. Identify the uses of Plastics
  3. Identify the methods of production of rubber
  4. Identify the uses of rubber

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,









The teacher Identify and discuss the methods of processing plastics

Students pay




Teacher discusses the uses of Plastics.

Students pay

attention and





Teacher discusses the methods of processing rubber and state the uses of rubber.

Students pay

attention and




The teacher writes a summarized

note on the board

The students

copy the note in

their books





The processing of plastics involves converting raw plastic materials into finished products through various manufacturing techniques. Here are some common methods of processing plastics:

  1. Extrusion:In extrusion, molten plastic is forced through a die to create a continuous profile or shape. It is used for the production of pipes, tubing, sheets, films, and various profiles.
  2. Injection Molding: Here a molten plastic is injected into a mold cavity, where it cools and solidifies to form the desired product. It is used for the production of automotive parts, toys, packaging, consumer goods.
  3. Blow Molding: Here hollow plastic parts are formed by inflating a hot, hollow tube of plastic in a mold cavity. It is applicable for the production of bottles, containers, automotive components.
  4. Rotational Molding (Rotomolding): Plastic powder is placed in a mold, heated, and rotated on two axes to evenly coat the interior of the mold as it melts.

          It is used for the production of large containers, tanks, playground equipment.

  1. Compression Molding: A plastic material is placed in an open mold, and pressure is applied to compress and shape the material.

           It is used for the production of automotive parts, electrical components, appliance parts.

  1. Extrusion Blow Molding: Similar to blow molding, but starts with a tube of plastic (parison) formed by extrusion. Used for bottles, containers, automotive parts production.
  2. Injection Blow Molding: A preform is injection molded and then transferred to a blow molding machine to form the final shape. It is used for the production of bottles, pharmaceutical containers.

Uses of Plastics

Plastics have become ubiquitous in various aspects of modern life due to their versatility, durability, and cost-effectiveness. Here are some common uses of plastics across different industries:

  1. Plastic packaging materials, such as bags, bottles, and containers, are widely used for food, beverages, cosmetics, and household products due to their lightweight and protective properties.
  2. Plastics are used in automotive parts to reduce weight, improve fuel efficiency, and enhance design flexibility. Examples include interior components, dashboards, bumpers, and various trim parts.
  3. PVC pipes, insulation materials, window frames, and flooring are examples of plastic products used in construction for their durability, weather resistance, and ease of installation.
  4. Plastics are integral in the production of electronic devices, including casings for smartphones, laptops, and other gadgets. Insulating materials and connectors are also made from plastics.
  5. Plastic materials are used in medical devices, packaging for pharmaceuticals..
  6. Plastic-based materials, such as polyurethane foam and polystyrene, are used for insulation in buildings. PVC is commonly used in pipes and electrical conduit.
  7. Artists and designers utilize plastics for creating sculptures, modern art installations, and various design elements due to their moldability and ability to achieve unique shapes.


The processing of rubber involves several manufacturing methods to transform raw rubber materials into finished products with desirable characteristics. Here are some common methods of processing rubber:

  1. Mastication: Raw rubber is mechanically worked, typically through a mill or extruder, to break down large polymer chains and improve processability. Mastication softens the rubber, making it easier to mix with other ingredients in the subsequent steps.
  2. Compounding: Various compounding agents, such as carbon black, accelerators, antioxidants, and fillers, are mixed with masticated rubber.
  3. Mixing (Banbury Mixing): The rubber compound is mixed in a Banbury mixer or two roll mill to achieve uniform dispersion of compounding agents.s.
  4. Calendering: The mixed rubber compound is passed through a series of rollers in a calender machine to form sheets of the desired thickness.
  5. Extrusion: The rubber compound is forced through an extruder, typically in the form of a continuous profile or tubing.
  6. Vulcanization: Rubber is treated with sulfur and heated to a specific temperature to initiate cross-linking between polymer chains, forming a three-dimensional network.
  7. Molding: Vulcanized rubber is shaped using molds and heat to create specific products or components.

Uses of Rubber

Rubber is a versatile material with a wide range of applications due to its elasticity, resilience, and insulating properties. Here are some common uses of rubber across various industries:

  1. The largest single application of rubber is in the production of tires for vehicles, including cars, trucks, bicycles, and motorcycles. Rubber provides the necessary grip, flexibility, and durability for tire treads.
  2. Rubber is used in various automotive components, including belts, hoses, gaskets, seals, and engine mounts, for its ability to dampen vibrations and withstand mechanical stress.
  3. Rubber is a key material in the manufacturing of shoe soles, providing comfort, flexibility, and slip resistance. It is commonly used in athletic shoes, boots, and casual footwear.
  4. Rubber belts are widely used in industries for power transmission, conveying materials, and facilitating mechanical processes. Common examples include conveyor belts and V-belts.
  5. Rubber is employed for seals and gaskets in machinery and equipment to prevent leaks and provide a barrier against moisture, chemicals, and contaminants.
  6. Rubber is an excellent electrical insulator, making it suitable for the production of electrical insulation materials, cable insulation, and insulating gloves used in electrical work.
  7. Rubber is used in various consumer goods such as erasers, handles, grips, and elastic bands for its flexibility, durability, and resistance to wear.


EVALUATION: 1. Discuss the steps for processing rubber

  1. Identify 5 uses of rubber
  2. Mention and discuss 5 methods of plastic production.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively