RECYCLING OF PLASTICS

The 20th century has been seen the invasion of plastic into almost all the spheres of our daily lives. The increasing of consumerism, plastic knowingly or unknowingly have taken certain stages. No other materials which has a wide applications as plastic have the reason is versatility.

  • According to WWF, 1,50,000 tons of plastic are used only for water bottles, every year. The state cabinet of Maharashtra in August 2005 has decided to ban plastic bags. Banned plastic bags of less than 20 microns thickness but failed miserably in implementing.
  • The word ‘Plastic’ means able to be molded. That can be molded into any required shape and size can take any color.
  • Plastic are also light, portable, resistant to the effects of water, chemical, sunlight etc.
  • The single largest use of plastic is in packing and in construction materials. Major uses include electronics telephones, televisions, radios, computers, tapes, CDs, transportation parts of cars, ships, industries, appliances, housewares, bottles, light switches, furniture, toothbrush, carpets, clothes, bags and toys. The most commonly used resins and their uses are

1. LOW DENSITY POLYETHYLENE (LDPE)

  • Used primarily for making wraps for baked goods and meats, trash bags pipes and coatings for wires and cables.

 2. HIGH DENSITY POLYETHYLENE (HDPE)

  • Milk bottles containers for liquids like motor oil and detergents, dairy crates, toys, housewares, pipes and pails.

3. POLYPROPYLENE (PP)

  • Drinking straws, battery case box liners, bread and cheese wrap, dosing of acids etc.

4. POLYSTYRENE (PS)

  • Plastic plates and cups, egg cartons, food trays, furniture and housewares.

5. POLYETHYLENE TEREPHTHALATE (PET)

  • It is primarily used to make soft drink bottles, PET is also used as packing material.

6. POLY VINYL CHLORIDE (PVC)

  • Building materials like pipes, siding and flooring, wall covering and bottles for storing cooking oil, water etc.

         Some recycling, reuse, reduces method in general are:

  • Build  enclosures to limit the dispersion of pollutants in industries.
  • Use personal protective device for workers success respirators, gloves, shoes and  goggles.
  • Maintain good housekeeping by regular cleaning.
  • Increasing concern about pollution and its effects on the delicate ecosystem, disposal of plastics represents a major environmental challenge. Plastics, unlike animal and vegetable matter, are neither biodegradable and photo degradable or can they be burnt like paper. Hence the need arises for plastics to be recycled.
  • Environmental aspects, the lack of effective non plastic substitutes and the threats of ban on the use of plastics like PVC, necessitate recycling of used plastic products.

  RECYCLING IS MADE UP OF THREE STAGES

  • COLLECTION
  • SORTING
  • REPROCESSING

   1. COLLECTION

  •  A substantial portion of plastic waste finds its way into people’s homes. The most efforts in collecting plastics for recycling have targeted the residential sector of the communities.
  • Complex chemical composition and very low density relative to recyclable paper, glass and metals make collecting plastics particularly unique and troublesome problems.

    2. SORTING

  • Pure plastic like article made out of only a single resin type can be separated manually through it is a laborious process. Plastic Recycling Facility (PRF) has been developed which makes mixed plastics sorting a viable option.
  • When plastic containers are still white, PET and PVC are removed by hand.
  • An air classification system is used to separate polystyrene from the plastics.
  • After the PS, PET and PVC has been removed the whole containers and shredded and metals are removed using magnetic separators from the ferrous and eddy current separators from the nonferrous.
  • A secondary granulation is then used to  reduce the size of the plastic.
  • The material passes through another air classifier to remove paper contaminants. A washing system is used to clean up the granule prior to the final separation process.
  • The PRF uses a density a separation system. The granules are fed into a float tank which contains water.
  • Remaining PET and PVC sinks while polyethylene and polypropylene float. Rigid PS is also separated.
  • The final step in the process is for the individual polymers to be dried and flaked.

     3. REPROCESSING

  • In reprocessing the material goes through a cleaning process is shredded or ground and then melted and reformed in an extrudes. The recycle resin is then put back into the manufacturing process. Using mixed plastics usually requires except for those that make mixed plastic products that the various resins be sorted prior to reprocessing.
  • LDPF is reprocessed in the following way:
  • The plastic is fed into a recycling extruder which melts it about 240 degrees Celsius. It is then squeezed and screened severe times to remove impurities and chopped into pellets. 
  • Recycling pellets are combined with virgin pellets and pigments, melted and extruded again and finally fed out in sheet form.

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