Plastic Facts

  • Some plastics are light and soft and can be filled with air bubbles to make an ideal packing material.
  • Vacuum molding involves using a vacuum to suck a sheet of plastic into a mold.
  • Extrusion molding involves heating plastic pellets and forcing them through a nozzle to give the required shape. Plastic pellets Extrusion molding is used to produce continuous shapes such as pipes. Injection molding is used to produce non-continuous forms such as bowls.
  • Plastics are synthetic (man-made) materials that can be easily shaped and molded.
  • Most plastics are polymers (see new materials). The structure of polymer molecules gives different plastics different properties.
  • Long chains of molecules that slide over each other easily make highly flexible plastics such as polythene. Tangled chains make rigid plastics such as melamine.
  • Typically plastics are made by joining carbon and hydrogen atoms. These form ethene molecules, which can be joined to make plastic called polythene.
  • Many plastics are made from liquids and gases that are extracted from crude oil.
  • Thermoplastics are soft and easily molded when warm but set solid when cool. They are used to make bottles and drainpipes and can be melted again.
  • Thermoset plastics, which cannot be remelted once set, are used to make telephones and pan handles.
  • Blow molding involves using compressed air to push a tube of plastic into a mold.