The plastics

The plastics

1. Origin of plastics

   • A plastic is a material made of polymers
     • Polymers are made up of macromolecules that are obtained by repeating a simple molecule called a monomer. The union of these simple molecules is carried out by the polymerization reaction.
   • Can be:
     • Natural
       • Obtained from natural susbtances
     • Artificial
       • They are obtained petroleum hydrocarbons. They are the majority of those we know today.

2. Plastic forming

   • INJECTION MOLDING:
     • 1st The granules are dragged by the movement of the screw to melt by the action of the heating bands
     • 2nd The molten plastic is pushed by the screw, injecting it into the mold that will shape it.
     • 3rd Once the material has cooled, the piece is removed from the mold.
   • Extrusion
     • 1st The granules are dragged by the movement of the screw to melt by the action of the heating bands
     • 2nd The molten plastic is pushed by the screw forcing it to pass through a nozzle (boquilla) that will shape the plastic.
     • It is used to obtain tubes, pipes, carpentry profiles
   • BLOW MOLDING:
     • 1st A cylinder called preform is introduced into a hollow hot mold.
     • 2nd The mold is closed and hot air is introduced under pressure so that the material expands adapting to the mold.
     • 3rd Once cold, the mold is opened and the piece is extracted.
     • This process is used to obtain bottles and similar products.

3. Recycling of plastics

   • We can recycle the plastic:
     • Replacing it for other element of material more biodegradable
     • Using plastic biodegradable
     • Recycling it in the dustbin
     • Reutilizing ever if it is posible

4. Tipes of plastics

   • Thermoplastics
     • A completely linear internal structure.
     • They melt easily.
     • They are ideal for recycling
     • They are very cheap
     • They are easy to model
     • They have the disadvantage that with high temperatures they deform
   • Thermosets
     • Their chains are entangled and held together with strong bonds
     • Heating them can give them shape, but a second heating would decompose them. They are not recyclable.
     • Pan handles and electrical plugs are examples of these plastics
   • Elastomers
     • More or less linear chains, with bonds that join them together, which gives them great flexibility and elasticity (they regain their initial shape after deformation)
     • They are easily degraded by heat, so they are not recyclable by this system
     • Tires and diving suits belong to this group.
     • Rubbers, neoprene, polyurethanes, silicones…

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