Study on degrees of mesomorphic zone of polymer. Ⅲ.Determination of the degree of crystallinity of Eucommia Ulmoides gum by VTFTIR and VTWAXD

Abstract

Eucommia Ulmoides (EU) gum will crystallize easily at room temperature due to the regular trans-1,4-polyisoprene (TPI) molecular structure. Around the skeleton stretching vibration band of TPI, its FTIR spectrum showed 5 weak crystalline peaks decrease as temperature increase, and there are also two amorphous peaks (845 cm−1 and 668 cm−1) increase as temperature increase. According to this phenomenon, Variable Temperature Fourier Transform Infrared Spectrum (VTFTIR) and Variable Temperature Wide Angle X-ray Diffraction (VTWAXD) have been taken to analyze the degree of crystallinity of EU gum. In addition to the ratio of crystalline zone, the result determined by VTFTIR also involve the mesomorphic zone, which make it higher than the result determined by VTWAXD. Through the comparative analysis of VTFTIR and VTWAXD, it has been proved that the ratio of crystalline zone, mesomorphic zone, amorphous zone in EU gum were respectively 39.8%, 27.6%, 32.6% at room temperature. Based on the Density Measurement and the three-phase model theory, the density gradient function of the mesomorphic zone of EU gum was firstly proposed. Below 60 °C, the density of the mesomorphic does not change with the temperature, approximately 0.931g/cm−3. Above 60 °C, the density of the mesomorphic decreases with the temperature increasing, and finally drops to 0.905g/cm−3 at 80 °C, which is equal to the density of the complete amorphous zone.