Plastic Properties, Types, and Manufacturing

Posted on Mar 5, 2025 in Technology

Properties of Plastics

Lightweight

This provides comfort when loading and transporting objects or plastic containers.

Impermeable

We can produce fabrics that protect us from the rain, or pipes that carry water or gas.

Photodegradable

Continued exposure to sunlight degrades them and makes them more brittle over time.

Electrical Insulator

We can protect ourselves from electrical accidents if we isolate steel cables with plastic.

Tough (Not So Fragile)

We can manufacture windows, bottles, or lenses for impact-resistant glasses.

Resistant to Many Chemical Substances

We can package highly corrosive chemical products.

Advantages of Plastics

  • As they are light, we save a lot of energy in the transport of plastic objects or products packaged in plastics.
  • By having a low melting point, less energy is consumed in the manufacturing process.
  • As thermal insulators in homes, they help us save energy on heating and cooling.

Disadvantages of Plastics

  • They are not biodegradable like wood or natural fibers. Therefore, as waste, they do not naturally disappear until after hundreds of years.
  • Some types of plastics can be very toxic if, to eliminate them, they are burned in incinerators.
  • Due to the great variety of plastics that are put into the containers, recycling is more difficult than that of the other materials such as glass, paper, or metals.

Recycling Plastics

Selective Recycling

Plastics are separated by type, crushed, cleaned, melted, and objects are once again made with almost the same quality as the originals.

Non-Selective Recycling

The same as the above but without separating plastics by type. It is the cheapest, but the plastics obtained has a lower quality than the original and cannot be used for food packaging.

What Are Plastics?

Plastics come from fossil fuels (coal, oil, natural gas), formed millions of years ago by the decomposition of living organisms. The main chemical elements of plastics are carbon, hydrogen, and oxygen.

Examples of Types of Plastics

Thermoplastics

PP (polypropylene) / PC (polycarbonate) / PA (polyamide)

Thermostable

Melamine resins / Epoxy resins / Polyester resins

Elastomers

Rubber / Silicone / Polyurethane

Do Thermoplastics Have a Numeric Code?

Many objects have a numeric code to identify the type of plastic.

Bioplastics Definition

A type of biodegradable plastic derived from biological substances rather than petroleum.

Bioplastics Advantages

  • It is a renewable resource; that is, they will never be exhausted.
  • They can be biodegradable and, therefore, compostable. Thus, we convert a residue into fertilizer for the plants.
  • Their production pollutes less and consumes less energy.
  • If they burn, they do not emit toxic gases.
  • They allow printing with water-based inks, less polluting than the usual ones.

How Are Plastic Objects Manufactured?

  1. Place the plastic (granules) in the mold.
  2. Heat the plastic (with electrical resistance) and soften it.
  3. Give shape to the plastic using the mold.
  4. Cool the plastic objects.
  5. Remove the plastic object.

Manufacturing Processes

Compression, extrusion, injection, blow molding, vacuum forming, calendering, rotational molding, immersion molding

Compression Molding

Manufacturing by compression or thermocompression applies mainly to thermostable plastics, such as bakelite. Plastic is placed in a steel mold and it is heated to make it pasty. Pressure is applied with a hydraulic press so that the plastic takes the shape of the mold. It is then allowed to cool and extracted from the mold.