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Making Perspex (AQA new spec)

Discussion in 'Science' started by gasheadruss, Aug 5, 2011.

  1. On the scrounge for info again!
    AQA's new spec refers to demonstrating making perspex. Has anyone found any info on this or even done it before? It must be a bit elusive as in my search I came across the same question on a thread on another forum which no-one was able to answer...
    Any pointers much appreciated.
    Thanks.

     
  2. On the scrounge for info again!
    AQA's new spec refers to demonstrating making perspex. Has anyone found any info on this or even done it before? It must be a bit elusive as in my search I came across the same question on a thread on another forum which no-one was able to answer...
    Any pointers much appreciated.
    Thanks.

     
  3. sci84

    sci84 New commenter

    Not sure why AQA are suggesting this?! Unless they have some other method!
    Google "methyl methacrylate cleapss" and the first link takes you to the laboratory handbook.
    Look in the plastics section page 1341 and it says:
    <font size="4" face="NewCenturySchoolbook,Bold">Poly(methyl methacrylate)
    </font>
    The monomer has a very irritant vapour, is highly flammable and its boiling point is
    below that of water. In a few rare cases, people handling the monomer have become
    sensitised so that further contact brings on an asthma attack.
    <font size="5" face="WarningLHPi"><font size="4" face="Arial,Bold">It is advisable not to polymerise methyl methacrylate to make Perspex.</font>
    </font>
     
  4. phlogiston

    phlogiston Lead commenter


    This can be good - but you need to woork with care as both starting materials are hazardous.
    Monomer for perspex is methyl methacrylate.
    It needs washing with sodium hydroxide solution (0.1/0.5M will do - this should be done in advance by a technician using a spearating funnel). YThis removes the inhibitor.
    I put about 1ml in an old test tube (has to be discarded at the end of the lesson). Add 1 spatula lauroyl peroxide (eye irritant) and put the tube in a hot water bath. Polymerisation occurs over about 10 minutes. As the peroxide decomposes, bubbles form and they enable the increase in viscosity to be seen. Eventually a solid is found in the tube. This must not be removed as unreacted starting materials are dangerous.
    This works safely as a class experiment if the tubes are premixed. The mixture must not be tipped into the hot water as methylmethacrylate vapours are more than somewhat unpleasant, can cause respiratory difficulties.
    Best wishes,
    P

     
  5. blazer

    blazer Star commenter

    And we want to do this because..?
     
  6. phlogiston

    phlogiston Lead commenter

    CLEAPSS hazcards don't suggest that methyl methacrylate should not be polymerised. (Finally got to school to check them).
    I always ensure a high level of control as the reagents are hazardous.
    I do the polymerisation so that students can observe a monomer polymerising, and make inferences about the changing size of molecules as the viscosity increases.
    I shall give consideration as to whether I should do the activity as a demo.
    P
     

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