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Plastics, Hydrocarbons and Everyday Usage

1. PET is the most valuable plastic at the present time. Suggest a way to separate it from the others at a plastic recycling center.

2. Since waste plastics are mostly hydrocarbons, it has been suggested that waste plastic be used as fuel. From your observations, is this a reasonable suggestion. Defend your answer.

3. Suppose you have two other plastics to fit into your scheme. These are polymethymethacrylate (density 1.19 g/mL) and poly-4-methyul-1-pentene (density 0.83 g/mL). Where would they fit in your scheme?

4. Identify five common household plastics and for each of the plastics, show the starting monomer and the final polymer structure. For each polymer, show at least two monomer's worth. For example, polyethylene is ~CH2CH2-CH2CH2~.

Solution Preview

1) Polyethylen-terephthalate, is fully recycable and may be used for manufacturing new products in many industrial areas such as packaging for detergents, cosmetics, high-quality carpets, foils, car spare parts, pillow fillings for allergic persons and fabrics.
PET containers are identified by a resin identification code imprinted on the side or bottom of the container. PET bottles in the United States, which are usually clear or transparent green, carry the resin identification code " 1 " and the symbol "PETE." They may also be recognised by the dot, or circular gate, centrally located on the bottom.
In some areas, drop-off bins are provided at appropriate locations in the community and at retail deposit return sites. Recycling co-ordinators ask that container caps be removed and the bottles rinsed before being placed in a collection bin.
Once collected, containers are forwarded to recycling locations where they are run through grinders that reduce them to flake form. The flake then proceeds through a separation and cleaning process that removes all foreign particles such as paper, metal, and other plastic materials.
Having been cleaned according to market specifications, the recovered PET is sold to manufacturers who convert t into a variety of useful products such as carpet fibre, strapping, moulding compounds, and non-food containers.

2) It is definitely a reasonable suggestion. Both plastics and petro-products are hydrocarbons. The only difference is that in plastics the chain of molecules is longer. So, it was possible to break the chain into small segments to convert it into value-added fuel. It is proved from the following points :

a) The first report of turning plastic wastes into oil came in 2001 from the People's Daily, China's English language newspaper. An oil refinery in Hunan province had succeeded in processing 30 000 tonnes of plastic wastes into 20 000 tonnes of gasoline and diesel oil that satisfied the provincial standards.
Although no details were given on the technology used, it is most likely based on thermal depolymerization, a process for breaking down ...

Solution Summary

This solution of over 1,400 words contains recommendations on how to separate PET in a recycling center, if waste plastic can be used as fuel, and also it identifies and describes the monomer of five common household plastics.