Monday 12 September 2011

Plastics

There are two main types of plastics:
                   Thermo Plastics (chained)
                   Thermosetting plastics (cross linked)


Polymers (plastics)
      ABS     aerylonitrile butadiene styrene
      CA       cellulose acetate
      Nylon   polyamide
      PMMA polymethylmethacrylite
      PP        polypropylene
      HIPS    high impact polystyrene
      PS        polysyrene
      LDPE  low density polyethylene
      HDPE high density polyethylene
      uPVC   polyvynil chloride
      PVC     polyvynil chloride (unplasticisized, flexibe)
      PET     polyethylene terephthalate
      PC       polycarbonate
  • good electrical and thermal insulator
  • good strength to weight ratio
  • good resistance to atmospheric and chemical erosion
  • low melting point
  • light weight
  • wide range of colour and transparency's
Thermoset polymers:
      Epoxy resins
      Melamine Formaldahide
      Polyester resins
      Urea Formaldahide

Moulding Processes:
     Injection Moulding
      plastic granuels are poured into the njection moulder, they are then pushed down through a screw like tube, heating up on the way down, so they're liquid form, then they are injected into a split mould and cooled to set, then the mould is split open and there you have the finished product. The benifits of injection moulding are that its a very quiet, quick process, where there is no waste. There is also the oppetunity to add lots of detail. All deformed materials can be reheated and used again, therefore creating no waste materials.

      Compression Moulding
          this process uses powdered plastic, or sometimes sheet plastic, in the bottom of the heated mould, the hydrolic press then presses down onto the liquid plastic, and compresses into its required shape, the plastic then cools, ceating the shape reqired, this is a more difficuls prosess, as ther is a lot of ecsess materials.
       

Thursday 8 September 2011

Assignmnt 1



Last Christmas I purchased a pair of Abercrombie and Fitch jogging bottoms. As Abercrombie and Fitch are a very well known brand, they also come with a very expensive price tag! Despite the fact that they were extortionately priced I still went ahead with the purchase. I did not particularly like them, and just bought them for the recognisable name.
when my jogging bottoms arrived, I realised that I didn’t like them at all but I still wanted them for the name on the clothing. I wore the joggers, twice and I have owned them for eight months, I know now that I bought them for all the wrong reasons, although at the time it seemed like a great thing to do, I know now it was completely stupid, and I have learnt from my mistakes and will always make sure I take time to think about something before I buy it. I will make sure I have a reason rather than just the name.
I could have just as easily bought a less expensive pair that I actually liked and wanted to wear, as it would have been more value for money. in future I will buy things based on the quality, value for money and the look, not just for the brand.
at the time I was very stubborn as my mum told me I was silly to buy them just for the brand, especially as I did not like them, she showed me another pair of joggers that were much better looking, a decent quality and less than half the price, at the time I said no as they had no recognisable name. now I know how stupid I was, the named joggers cost £75 and I wore them once where as the other joggers cost £15...
what a mistake, never again...