Plastics

Plastics

1. 1st plastics

   • In the late 19th Century, Adolph Spitteler invented a galalith from milk casein, with which some buttons, combs and decorative objects are made. The first massively used plastic was the bakelite, invented by Leo Baekeland in the early 20th century.

2. What are plastics?

   • Plastic consist of long chains of molecules, mostly made of the element carbon

3. Origin of plastic

   • Natural
     • From vegetables (cellulosa, latex) or animal (casein) sources.
   • Artificial
     • From petroleum, natural gas and carbon

4. Obtaining plastic

   • Raw matter→ Polymerisation process→ Product Fillers and additives may be added during the manufacturing process

5. Plastics additives

   • Dyes, Foaming agents, Plastitizers and Fire retardants
     • they allow plastic to have a desired color
     • decrease the density a lot, obtaining a very light and insulating plastic
     • they increase flexibility and make less brittle plastics
     • they hinder plastic combustion as, for example in the case of fire

6. Plastics and enviroment

   • Advantages
     • Plastics are corrosion resistant and chemically inert. They have low thermal expansion of co-efficient and possess good thermal and electrical insulating property. Is very good water resistant and possess good adhesiveness. Plastic is strong, good and cheap to produce
   • Desadvantages
     • They are not biodegradable, as waste they don't disappear until a hundred years. Some plastic are very toxic and recycling is more difficult than other materials

7. Types of plastic

   • Bioplastics
     • are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc.
   • Elastomers
     • They stretch, obtained from the vulcanisation process
     • Natural rubber, synthetic rubber and neoprene
   • Termosetting plastics
     • When heated and moulded can be shaped but they don't soften if heat again
     • PUR, melamine. bakelite and UP
   • Thermoplastics
     • They soften when heated
     • PET, HDPE, PVC,LDPE, PP, PS, Methacrylate, telfon, cellophane and nylon.

8. Making a plastic object

   • Mold design
   • Mold making
   • Manufacturing the piece
   • Plastic manufacturing techniques
     • Compression, Extrusion, Injection, Blow molding, Vacuum forming, Calendering, Rotational molding and Immersion molding
   • Modification techniques
     • Measuring(carpenter's square,ruler, measuring tape, protractor, bench vice, C-clamp, bar clamp and ring clamp ),drawing marks and lines(punch, pencil and permanent marker ), cutting(scissors, utility knife, hacksaw, jigsaw, punch and hot wire cutter), drilling(drill and tap and handle) and filing and sanding(file,sandpaper, belt sander and orbital sander)
     • Joining
       • Temporary joints(bolts, nuts, washers and threaded)
       • Permanent joints: adhesives(2-part resins, acrylic cement and contact adhesives) and soldering (heat sealer and hot air welder