PLASTICS TECHNOLOGY

PLASTICS TECHNOLOGY

1. ORIGIN

   • POLYMERS
     • A plastic is a material made of polymers. Polymers are made up of macromolecules that are obtained  by the monomers.  The union of these simple molecules is carried out by the polymerization reaction.
   • NATURAL
     • They are obtained from natural substances. Examples: Latex, cellulose, casein
   • ARTIFICIAL
     • They are obtained from petroleum hydrocarbons.

2. PROPERTIES

   • - Good thermal insulators - Good electrical insulators - Very cheap - Easy to model - Light - Waterproof

3. OBTAINING PROCESS

   • 1st The oil is extracted from the wells. 2nd In the refineries we obtain the desired hydrocarbon. 3rd It is stirred in a reactor together with the additives. 4th The polymer is obtained in granules. During the production process some addittives are incorporated, plasticizers, or pigments.

4. 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.
   • POLYETHYLENE
     • - Lightweight, strong, and use in food. - Safe, but it can be use only one time because of hygiene
   • HIGH DENSITY POLYETHYLENE
     • - Rigid, resistant to hot and cold. - Safe, it is used in long-term food storage. - Oil carafes, detergents...
   • POLYVINIL CHLORIDE
     • - Resistant, strong, flexible and the most versatile. - Unsafe, most dangerous. - Use in toys, cables...
   • LOW DENSITY POLYETHYLENE
     • - Strong, flexible, resistant and transparent. - Safe, one of the safest. - Plastic bags....
   • POLYPROPYLENE
     • - High melting points for liquid containment. - Safe, recyclable. - Yogurts, bottle caps
   • POLYSTYRENE
     • - Acoustic insulator. - Unsure, easily deteriorated - Plates, glasses
   • OTHERS
     • Unsure, and their characteristic depend of the plastic

5. THERMOSETS

   • - Strong bonds - Heating them can give them shape, but a second heating would decompose them.  - They are not recyclable.- Electrical plugs 

6. ELASTOMERS

   • Linear chains, with bonds, 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 

7. EVIROMENTAL PROBLEMS

   • The principal problems of the plastics are: "THE MICROPLASTICS" The plastics in the sea decompose themselves in microplastics. Littles fish eats this micro plastics, and then a big fish eat that little fish. This big fish is the one that we eat in our daily lives and this means that we have micro plastics in our organism which is really bad for our health

8. PLASTIC FORMING

   • INJECTION MOLDING
     • - The granules are dragged by the movement of the screw to melt by the action of the heating bands. - The molten plastic is pushed by the screw, injecting it into the mold that will shape it. - Once the material has cooled, the piece is removed from the mold.
   • EXTRUXION
     • - The granules are dragged by the movement of the screw to melt by the action of the heating bands. - The molten plastic is pushed by the screw forcing it to pass through a nozzle that will shape the plastic.
   • BLOW MOLDING
     • - A cylinder called preform is introduced into a hollow hot mold. - The mold is closed and hot air is introduced under pressure so that the material expands adapting to the mold.- Once cold, the mold is opened and the piece is extracted.
   • VACUUM MOLDING
     • - A thin plastic sheet is introduced and attached to the mold. - The sheet softens due to the action of heat. - At the bottom the vacuum is made and the air is extracted.