Learn about plastics manufacturing

What are plastics?

Plastics manufacturing is a relatively modern process and has been making our daily lives better for just over a century. Because of the scarcity of more traditional product materials during World War II, the demand for plastics products rose quickly. The consumer boon of the 1950’s and 1960’s made sure that plastic goods and products were here to stay.

Plastics are materials that can be moulded into shapes by applying heat and /or pressure. Plastics manufacturing is the process of moulding these materials into something that we can use in our daily lives.

The materials (or chemicals) used to create plastics often come from natural substances like oil, sand, sugar cane, cotton, coal, and corn amongst others.

In plastics manufacturing, these natural substances have been already formed into materials so that they can be more easily used in the process. Often they can be found in the form of granules, tablets, powders, syrups or pastes.

Plastics Manufacturing - DemaPlasTech South Africa
Plastics Manufacturing - Thermosets - DemaPlasTech South Africa


Plastics typically belong in two main groups – thermosets and thermoplastics. Thermosets refer to plastics that can’t be melted again or reformed after they have been moulded. Some examples of thermosets include:

  • Polyurethanes (used in mattresses, cushions and ceiling insulation)
  • Unsaturated Polyesters (used in plastics baths and furniture)
  • Epoxies (used in glues and blades of jet engines and helicopters)
  • Phenol Formaldehydes (used in electrical circuit boards and some building products)

Thermosets are known for being durable and strong. The most common thermoset is the rubber truck and car tire.

Plastics Manufacturing - Thermoplastics - DemaPlasTech South Africa


This group of plastics can be re-melted after moulding. This makes them good for recycling for example. Examples of thermoplastics include:

  • Polyethylenes (used in packaging, plastic bottles and plastic wrapping)
  • Polypropylenes (used in carpets or car bumpers)
  • Polyvinyl Chloride or PVC (used in electrical cabling sheaths, building pipes and floor and wall coverings)

Thermosets are known for being versatile and can offer a wide range of uses. A common example of thermoplastics are include soft drink bottles and food packaging.

Some plastics manufacturing processes suit thermosets and others suit thermoplastics. For example, if a product needs to be created by reforming a plastic sheet, then this can only be done using thermoplastics.

The role of additives in plastics manufacturing

Plastics are often also called polymers. The term polymer is often used today in the plastics and composites industry, and it is often used to imply “plastic” or “resin”. A polymer is chemical compound where molecules are bonded together in long repeating chains. These materials (plastics or polymers) have unique properties and can be tailored to suit different purposes.

In the plastics manufacturing industry additives are used to make polymers perform better. This process creates a copolymer which is made up of two or more polymers. This flexibility to use additives to make a plastic better is an important feature of the plastic manufacturing process.

Additives can be included in plastics manufacturing to:

  • give additional strength or stability
  • act as plasticisers or lubricants
  • provide decoration or pigmentation
  • improve chemical resistance
  • act as fire-retardants
  • protect against ultra-violet degradation
  • reduce costs by acting as a filler.

It would be impossible to turn most polymers into useful objects without additives. Additives can be added in different quantities and can affect the long term stability of the plastic.

Plastics Manufacturing - Additives - DemaPlasTech South Africa

This is an example of a Moretto dosing unit used to measure and add additives in the plastic manufacturing process

The different types of manufacturing processes

There are a number of processing methods used to convert polymers into finished products that we can use in our daily lives. The manufacturing process influences both the particular plastic used and the characteristics of the product manufactured. These processes include:

  • Injection moulding
  • Extrusion
  • Blow moulding
  • Rotational moulding
  • Casting
  • Compression moulding
  • Thermoforming
  • Foaming

The most common manufacturing processes are extrusion, injection and blow moulding. Click on the buttons below to read more about these processes.

DemaPlasTech - Plastics manufacturing | 3D Printing

50 years of plastics manufacturing experience

DemaPlasTech have a wealth of experience in the South African plastics manufacturing industry and can help your business with a range of customised solutions to meet your needs. Our areas of expertise include:

Exclusive Sub-Saharan agents

DemaPlasTech are exclusive Sub-Saharan agents for a range of prestigious plastics manufacturing brands including Sumitomo SHI Demag, Moretto, Simar, Single, Mo.Di.Tec, Frigel and Epicor.

If you are involved in plastics manufacturing, let’s see how we can help your business.

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