Содержание
- 2. Over 80 million tonnes of poly(ethene), often known as polyethylene and polythene, is manufactured each year
- 3. Uses of poly(ethene) (polyethylene) Poly(ethene) is produced in three main forms: low density (LDPE) ( The
- 4. HDPE LDPE/LLDPE Figure 1 Uses of poly(ethene).
- 5. All forms can be used for injection-moulded products such as buckets, food boxes and washing-up bowls.
- 6. Poly(ethene) is used to make large water pipes and far smaller pipes.
- 7. Annual production of poly(ethene) (polyethylene)/million tonnes
- 8. Many plants can produce both forms of poly(ethene) and alter the amount that they produce of
- 9. Manufacture of poly(ethene) (polyethylene) Poly(ethene) is made by several methods by addition polymerization of ethene, which
- 10. Low density poly(ethene) (LDPE) The process is operated under very high pressure (1000-3000 atm) at moderate
- 11. This is a radical polymerization process and an initiator, such as a small amount of oxygen,
- 12. For example, It can be represented by:
- 13. There are about 20 branches per 1000 carbon atoms. The relative molecular mass, and the branching,
- 14. High density poly(ethene) (HDPE) Two types of catalyst are used principally in the manufacture of HDPE:
- 15. I. Slurry process (using either CSTR (continuous stirred tank reactor) or a loop) The Ziegler-Natta catalyst,
- 16. The manufacture of poly(ethene) using the slurry process in a loop reactor.
- 17. II. Solution process The second method involves passing ethene and hydrogen under pressure into a solution
- 18. III. Gas phase process Low pressure gas-phase process.
- 19. A mixture of ethene and hydrogen is passed over a Phillips catalyst in a fixed bed
- 20. Granules of poly(ethene) which are then used to make film, extruded into pipes or moulded.
- 21. The HDPE powder coming out of any of the reactors discussed above is separated from the
- 22. Linear low density poly(ethene) (LLDPE) Low density poly(ethene) has many uses but the high pressure method
- 23. For example, with but-1-ene, CH3CH2CH=CH2, the structure of the polymer is: The side chains are known
- 24. The structure is essentially linear but because of the short chain branching it has a low
- 25. Metallocene linear low density poly(ethene) (mLLDPE) This poly(ethene), known as mLLDPE, is produced by a new
- 26. The catalysts are even more specific than the original Ziegler-Natta and it is possible to control
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