Study on degrees of mesomorphic zone of polymer.Ⅰ.Determination of degrees of crystallinity of Eucommia ulmoides gum and natural rubber by dynamic mechanical thermal analysis |
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| Institution: | 1. Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029, PR China;2. Engineering Research Center of Elastomer Materials Energy Conservation and Resources, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029, PR China;3. State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing University of Chemical Technology, Beijing 100029, PR China;4. Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, PR China;1. Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, H-1521 Budapest, P.O. Box 91, Hungary;2. Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1519 Budapest, P.O. Box 286, Hungary;1. Department of Polymer Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, M?egyetem rkp. 3., H-1111 Budapest, Hungary;2. MTA–BME Research Group for Composite Science and Technology, M?egyetem rkp. 3., H-1111 Budapest, Hungary;1. Centre Català del Plàstic, Departament de Ciència dels Materials i Enginyeria Metal-lúrgica, Universitat Politècnica de Catalunya, BarcelonaTech, C/Colom 114, 08222 Terrassa, Spain;2. NUDEC SA, C/ Pintor Vila Cinca, 24-28, Pol. Ind. Can Humet de Dalt, 08213 Polinyà, Spain;1. Chemistry Department, Faculty of Science, Damietta University, Damietta, Egypt;2. Physics Department, Faculty of Science, Damietta University, Damietta, Egypt |
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| Abstract: | According to the two-phase model theories of polymer crystallization, the degree of crystallinity of natural rubber (NR) induced to crystallize at ?25 °C can be directly determined by dynamic mechanical thermal analysis (DMTA) by testing its tanδ peak areas of crystalline state and 100% amorphous state respectively. The degree of crystallinity is 86% when the induction time increases to 12 h. However, due to the tanδ peak area of 100% amorphous state cannot be measured by DMTA directly, the degree of crystallinity of Eucommia Ulmoides (EU) gum can only be determined indirectly with DMTA by using the tanδ peak areas of 100% amorphous state extrapolated from the linear equation (y = ax + b) which is derived from the relationship between tanδ peak areas and crosslink densities. The degree of crystallinity is 87%, which is very close to NR. The crystallization of NR can be prevented effectively by increasing slightly the crosslink density to the critical crystallization point, which is 6.20 × 10?5mol/cm?3 for vulcanized NR induced to crystallize at ?25 °C for 4 h. However, it is very hard for EU gum to prevent the crystallization by crosslinking. Because, with increasing of the crosslink density, the EU gum will firstly show a percolation threshold, which is 53.34 × 10?5mol/cm?3, and the degree of crystallinity is 71.04%. Then, like NR, the degree of crystallinity of EU gum will decrease rapidly to zero by increasing the crosslink density to the critical crystallization point, which is 68.89 × 10?5mol/cm?3. In the end of the paper, the linear relationship of the equation is verified and the influence factors on slope a and intercept b of the linear equation are discussed as well. |
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| Keywords: | Natural rubber Degree of crystallinity DMTA |
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