polypropyene analysis

please tell me how I can analyze the copolymer content of an unknown
polypropylene specimen? If DSC, so how much is the fusion heat of
isotactic PP.
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NMR would probably be best. You might be able to do a XRD correlation too. DSC can be tricky and difficult to see differences if the PE content is low, a delta H value is not clear. The "Polypropylene Handbook" by Edward J. Moore, Jr. (Hanser Press) page 125-126 lists published values between 148 and 209 J/g, with an average of 165. They cite the value of 209 from the Polymer Handbook (Brandrup and Immergut).
Best of Luck John Aspen Research -
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Do you know what the other "monomer" is? I think others have assumed ethylene as that is a very common copolymer (PP/PE). If you don't know you may want to try FTIR to get a quick feel for what other bonds are present. Unless the copolymer is present in only very small amounts then you are on to NMR and slogging through figuring out those peaks. Elemental analysis might help if you think there is anything other than hydrocarbon present (N, O, or S being the most likely candidates).
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Most PP copolymers contain 3-5 wt.% of ethylene as a comonomer. FTIR is the easiest way to get a quantitiative value for the amount of comonomer. Although NMR should work as well.
Larry Effler
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Larry Effler
FTIR analysis has been and continues to be the best quickest ,best and most economical method in use today by all polymer manufactuers and those who do R&D by the big companies. Transient NMR was tried but found to be problematic and never flew. Joe Webster
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I have made recently some DSC's of PP with PE in it. In my case the fusion heat of PP (meltpeak at 164°C) was about 33 J/g and there was a peak at 96°C and a small peak at 122°C (PE). All together 100 J/g. So a lot less than 165 J/g. Another recent test with 100% PE gave me 160J/g (peak 129°C) Another polymer Vestoplast is a terpolymer of ethylene, propene and butene. It contains a lot amorphous polymer, but also crystalline polymer. What I want to say is : DSC is rather complex , but certainly usefull. If you have a pure polymer, than the fusion heat or the melting heat can be very high, because you will form nice crystallites. If another copolymer is used, that copolymer can interfere. It can make another type of crystallite (e.g. propene-butene) at another temperature. The other copolymer can disturb the crystallisation which will lead to a shift of the peak temperature and decreasing of fusion/melting heat. So I combine such investigations always with an IR-scan. PP has some distinct peaks. PE has a peak at 720 cm-1.
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Johan Goris

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