WORKING WITH MATERIALS

WORKING WITH MATERIALS

1. POLYMERS

   • Polymers  are made up of smaller molecules called monomers 
   • Natural
     • They are obtained using plant-based materials or from products of animal origin 
   • Synthetic
     • Are derived from petroleum and natural gas 

2. TYPES OF PLASTICS

   • ELASTOMERS
     • Rubber
       • Elasticity  Can be natural or synthetic 
     • Neoprene
       • Flexibility  Insulator  Waterproof 
   • THERMOSTABLES
     • PF: polyphenols
     • UP: polyester resins
       • Rigid and brittle  Strengthened with fibreglass 
     • UF: urea folmaldehyde
     • Bakelite
       • Hard and brittle  Resistance to heat 
     • Melamine
       • Resistance to high temperatures and chemicals  Easy  to clean
   • THERMOPLASTICS
     • PET: polyethylene therephtalate
       • Recyclable  Transparent Easy to dye 
     • PVC: polvinyl chloride
       • High resistance to abrasión and impact 
     • PP: polypropylene
       • Easy to model and dye  Resistance to solvents and splintering 
     • PS: polystyrene
       • Very lightweight  Transparent plastic 
     • PE: polyethylene
       • Chemical resistance Non-toxic
     • PC: polycarbonate
       • High resistance to impact and heat  Good optical transparency 
     • Teflon
       • High resistance to chemicals and high temperatures  Excellent non-stick properties 

3. PROPERTIES OF PLASTICS

   • PHYSICAL PROPERTIES
     • Low density
     • Light weight
   • THERMAL PROPERTIES
     • Thermal insulator
     • Low melting point
   • ELECTRICAL PROPERTIES
     • Electrical insulator
   • MECHANICAL PROPERTIES
     • Elasticity
     • Plasticity
     • Toughtness
     • Resistance to breakage = low tenacity
   • TECHNOLOGICAL PROPERTIES
     • Wayerproof
     • Fusibility
     • Malleability
     • Acoustic insulator
     • Flexibility
   • CHEMICAL PROPERTIES
     • Low melting point
     • Resistance to moisure
     • Resistance to oxidation

4. IDENTYFING PLASTICS

   • Scratching
     • Harder plastics will be more difficult to scratch.
   • Floatin in water
     • To test density
   • Burning
     • Some properties can be observed by burning, observing the flame and checking whether or not meltig occurs.

5. FORMING PLASTICS

   • Compression moulding
     • It is used with thermoplastics.
   • Injection moulding
   • Extrusion
     • It is used with thermostables.
   • Blow moulding
   • Vacuum forming
     • It is used with thermoplastics.

6. WORKING WITH PLASTICS

   • Marking
     • It is important to protect the plastic
   • Cutting
     • When the sheets are thin, they can be cut using a cutter
   • Joining by cohesion
     • Pieces of plastic are joined by heating them or using solvents
   • Drilling
     • For making holes
   • Sawing
     • For cutting thicker sheets
   • Joining by adhesion
     • Special adhesives are used
   • Mechanical joining
     • Rivets, screws, nuts and bolts are used.

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