rubber moles 1

[roes]

How can I convert rubber mass to moles? I know the number average molecular weight.

 

[berti]

Hi roes,
basically you can calculate molecular weight of rubber polymer.

But I suppose you are going to calculate the amount of something which should react with the rubber or what is the content of an element in the rubber? E.g how many percent chlorine is in chloroprene rubber or how many % sulfur can react with natural rubber.
In this case you have to calculate with the molecular weight of the repeating unit in the polymer. Some typical examples:
poly-butadiene (BR) -CH2-CH=CH-CH2-
M=12*4+6 = 54
poly-isoprene (NR) -CH(CH3)-CH=CH-CH2-
M= 12*5 + 8 = 68

For copolymers (NBR, SBR) you have to take both monomer units and multiply with the fraction.

E.g. NBR with 33 % acrylonitrile ( and 67 % butadiene)

poly acrylonitrile -CH2-CH(CN)- M= 12*3+14*1 + 3 =53

0,33 * 53 + 0,67 * 54 = 53,66.

Example:Nitrogen content in a.m. NBR: 0,33*14/53,66 =8,6 %
HTH Berti