The density of perfectly crystalline polyethylene is c = 1000 kg m-3, and the density of perfectly amorphous polyethylene is a = 865 kg m-3. (i) For a semi-crystalline material with mass density , show that the percent crystallinity (xc) can be calculated as: xc = a c a where c is the mass density of a 100% crystalline polymer. (ii) Calculate xc in a sample of linear polyethylene with s = 970 kg m-3 and a sample of branched polyethylene with = 917 kg m-3. (iii) Why do the two samples have considerably different crystalline content?

3. The density of perfectly crystalline polyethylene is c=1000kgm3, and the density of perfectly amorphous polyethylene is a=865kgm3. (i) For a semi-crystalline material with mass density , show that the percent crystallinity (xc) can be calculated as: xc=caa where c is the mass density of a 100% crystalline polymer. (ii) Calculate xc in a sample of linear polyethylene with s=970kgm3 and a sample of branched polyethylene with =917kgm3. (iii) Why do the two samples have considerably different crystalline content