DT Plastics

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  • Plastics
    • 3 main types of plastics(Polymers)
      • Thermoplastics
        • These  materials can be repeatdly reheated and re-moulded
        • Structure- Have a tangle of long-chain molecules held together by strong electrostatic forces
      • Elastomers
        • These are polymers that have a good elasticity, i.e they can be distorted under pressure but will return to original shape.
        • Structure- Have long chain molecules like coils whihc spring giving it elastic properties
      • Thermo-setting plastics
        • A chemical change results in them becoming permenantly rigid i.e cannot be re-heated/reshaped
        • Structure-  coonsist of long chain molecules but differ in thath they ar eheld together by rigid cross-links making them permanently rigid
    • Introduction
      • Plastics are a group of materials made up of a long chain of molecules. Mostly  hydrocarbons(hydrogen and carbon atoms only)
      • Plastics are becoming  more popular than other materials because of its benefits(lightweight, self-colored/finished, electrical and thermal insulator).
    • General properties of plastics
      • +They are good electrical/thermal insulators
      • +They have a good strength to weight ratio
      • +Good atmospheric and chemical corrosion resistance
    • Improving the properties of plastics
      • Fillers-Fill in plastic reducing bulk and price
      • Flame-Retardants-Reduces the risk of combustion
      • Anti-static agents-Reduce the effects of static charges that could build up on a product
      • Plasticizers- added to increase plasticity and flexibility to reduce brittleness
      • Stabilisers-used to reduce the effects of UV light , by breaking down sunlight
    • Sources of plastic
      • Animal and vegetable by products-are used to manufacture some synthetic polymer plastics. E.g Cellulose(plant fibre)
      • Coal, oil and gas- Most purely synthetic plastics
    • Biodegradab-e Plastics-Conventional oil plastics don't biodegrade. Thus biodegradea-le plastic are designed to degrade in correct conditions
      • Applications-vary widely mainly packaging: shopping bags, food trays,soft drinks bottle, disposable items, gardening, medical,  sanitary products
      • PHAs and PHBs-Biodegradabl-e plastic polymers are created naturally using bacteria to aid in fermentingplant sugars forming PHA. The most popular type is PHB
      • Oxo-degradable polymers-Have additives that promote short degradation time e.g. less than five years.


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