• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Story of Poly(ethene) and Poly(propene).

Extracts from this document...

Introduction

The Story of Poly(ethene) and Poly(propene) The term "Addition Polymerisation" means when a reaction takes place where a polymer is created from its monomers without leaving other molecules behind. A monomer is a molecule that when joined up in long chains create a polymer. For example: the monomer of polyethylene is an ethylene molecule: CH2=CH2 When this molecule is joined up with other similar molecules it creates polyethylene, a polymer. CH2=CH2 + CH2=CH2 ? -CH2-CH2-CH2-CH2-CH2-CH2- ethene ethene polyethene piece When this reaction takes place nothing is lost as the monomers (i.e. ethene) join end-to-end forming no other products. The monomers double bond is opened to bond with other monomers. When Polyethene is produced there are two kinds, hdpe and ldpe. Ldpe is polymer molecules that contain branching. The carbons of an ldpe instead of having Hydrogen atoms they will have polyethene bonded to them. ...read more.

Middle

The structure of hdpe on the right of the diagram shows a much more compact structure making it a much more strong plastic. The same rule applies to polypropene. The fact that hdpe and hdpp are closely compacted together also means it can withstand higher temperatures. This can be shown simply by getting a plastic bag and a plastic chopping board. When you place the plastic bad over a source of heat you can see that is melts almost straightaway, yet the plastic chopping board doesn't. The complete control of the process of polymerisation was not something that was done overnight. It involved a lot of lucky chances in understanding how it really worked. On Friday, March 24 1933, the chemists Eric Fawcett and Reginald Gibson carried out an experiment. Ethene was heated with benzyldehyde at 1400 atmospheres in an attempt to prepare a ketone. ...read more.

Conclusion

The greater the pressure, the higher the average molecular mass. They also discovered that if the temperature within the vessel was too high, then explosions were more imminent. The solved this problem by the addition of cold ethene. Further on in the development of polyethene, the chemists Zielger and Holzkamp found that in one experiment, no polymer was produced. After thorough investigations, they found that the vessel contained small traces of Nickel from previous experiments. This made them question whether adding other metals to the reaction had the same or even opposite effects. They found that adding certain compounds (triethylaluminium catalyst) into the ethane made it polymerise more easily. The chemist Guilio Natta wanted to see whether the same methos would work for Propene. This worked well, it seemed that scientists had the knowledge to control the manufacture of polymers. However the control was not total. This was because if this catalyst were damaged in any way, the forming of chains would cease. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Classifying Materials section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Classifying Materials essays

  1. Marked by a teacher

    In this CDA I will write about how plastic bags are made, why plastic ...

    Plastic bags are not good for the environment. As I had written previously, they may take about 1000 years to degrade in landfills (in bad circumstances, in good circumstances polyethylene will take about 20 years to degrade), and as they degrade they may become toxic. Plastic bags are increasing more and more and as they do, many of them come in contact with animals.

  2. What "Carried the Trick"? Mass exploitation and the decline of thought in Ray Bradbury's ...

    Powerful "beetle cars" are designed, and probably marketed, for "driving a hundred miles an hour, at a clip where you can't think of anything else but the danger" (84). Millie often drives "a hundred miles an hour across town .

  1. Affect of concentration on reaction

    Reduce the quantity of calcium carbonate to 2.00g. Results 4 50cm3 0.4M HCl Starting Mass 2.00g CaCO3 (Powdered) Time (seconds) Mass (grams) Mass Loss (grams) 0 2.00 0.00 5 1.99 0.01 10 1.98 0.02 15 1.97 0.03 20 1.96 0.04 25 1.96 0.04 30 1.95 0.05 35 1.94 0.06 40

  2. The role of mass customization and postponement in global logistics

    In the wake of growing competition, even government controlled firms have started to practice customisation in limited ways. Cooptex, the Cooperative textile firm of Tamil Nadu, Government has introduced recently the free selection of design, pattern etc. for the silk and cotton sarees by the consumers through computers which can be produced and delivered in a definite period.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work