Surakit TuampoemsabAdun NimpaiboonJitladda T. SakdapipanichKing Mongkut's University of Technology North BangkokMahidol University2018-11-232018-11-232015-01-01Polymer Testing. Vol.43, (2015), 21-26014294182-s2.0-84923872495https://repository.li.mahidol.ac.th/handle/20.500.14594/35778© 2015 Elsevier Ltd. All rights reserved. Isoprene units in natural rubber (NR) and its synthetic analogues were quantified by1H-NMR spectroscopy using polyethylene glycol (PEG) as an internal standard. The effect of PEG and rubber concentrations, molar ratio of rubber/PEG, measuring temperature and scan number on the quantification was investigated to establish the respective working range. Analysis of commercial grades of NR revealed that the differences in 1,4 isoprene content is caused by the production process and feedstock, in which proteins and lipids were found to be the major impurity in NR. Gel fraction of NR has insignificant effect on the measurement of 1,4 isoprene content. Furthermore, the new method was found to produce good results for the quantification of 1,4 and 3,4 units of synthetic polyisoprenes.Mahidol UniversityChemistryMaterials ScienceArticleSCOPUS10.1016/j.polymertesting.2015.02.003