Thermal degradation of epoxidized natural rubber in presence of neodymium stearate

The effect of neodymium stearate (NdSt) synthesized by saponification method on thermal degradation and thermo-oxidative degradation of expoxidized natural rubber with 25 mol.% epoxidation (ENR25) was investigated by thermogravimetric analysis (TGA), and the structure of ENR25 vulcanized with NdSt after thermo-oxidative decomposition was characterized using Fourier transform infared spectroscopy-attenuated total-reflectance (FTIR-ATR). The thermal degradation kinetic parameters of ENR25 with different loadings of NdSt were determined by Coats-Redfern method. The results showed that the thermal degradation of ENR25 in nitrogen was a one-step reaction regardless of NdSt content, whereas the thermo-oxidative degradation was a multiple-step reaction. The thermal and thermo-oxidative stability of the ENR25 vulcanizates with the addition of NdSt was higher than that of pure ENR25 vulcanizates. The ENR25 vulcanizates with the incorporation of 1 phr (per hundred parts of rubber) NdSt imparted the highest activation energy (E) of thermal and thermo-oxidative degradation. This could be attributed to the many unoccupied orbits in rare earth Nd, which could capture the free radicals and make the epoxide groups stable in the process of thermal and thermo-oxidative degradation for ENR25.     

固相微萃取和同时蒸馏萃取法分析海南香草兰挥发性成分

对固相微萃取（solid phase micro-extraction,SPME）技术萃取香草兰中挥发性成分的萃取条件进行优化, 并采用SPME和同时蒸馏萃取（simultaneous distillation extraction,SDE）两种方法对海南地区香草兰豆荚中挥发 性成分进行检测分析。结果表明：SPME最优萃取条件为萃取头75 μm CAR/PDMS、萃取温度80 ℃以及萃取时 间20 min。2 种萃取方法共检测出105 种挥发性成分,其中利用SPME技术检测出挥发性成分73 种,SDE检测出78 种。结果表明：将SPME和SDE两种方法联合使用可以更加全面地检测出香草兰中的挥发性成分。     

胡椒叶抗氧化能力分析及其活性成分分离鉴定

胡椒果与叶都具有抗氧化活性,而叶还具有抗动脉粥样硬化功能,但胡椒叶的活性因子并不明确,另摘叶可以提高胡椒产量,为给胡椒叶开发利用提供理论依据,本文用氧自由基清除能力(ORAC)方法评价了胡椒叶的抗氧化活性,结果表明胡椒叶ORAC值为3639.05μmol TE/g,高于胡椒果(胡椒鲜果、白胡椒和黑胡椒);通过系统溶剂提取法,确定了胡椒叶的乙醇提取物的ORAC值最高;以ORAC检测方法作为分离鉴定抗氧化活性物质的追踪方法,对胡椒叶乙醇提取物依次萃取和采用硅胶层析、凝胶层析、反相层析、薄层层析及HPLC等方法分离纯化得到活性目标物,通过核磁共振和质谱等手段鉴定与表征,首次从胡椒中分离得到两种具有较高抗氧化活性的扁柏脂素和野漆树苷,其ORAC值分别为16070μmol TE/g和10823μmol TE/g。     

天然橡胶/羧甲基壳聚糖抗菌复合膜的力学性能研究

采用胶乳共混法制备得到了天然橡胶羧甲基壳聚糖(NR/CCS)复合胶膜,通过NMR交联密度仪、拉力测试机、动态热力学分析仪等对复合材料的性能进行了表征。结果表明,复合胶膜的交联密度略微增大(5.75×10-5mol/cm3),力学性能增强到11.25MPa,并且复合胶膜的弹性模量增大,刚性增强,并通过这些测试证明了NR与CCS分子存在氢键的作用。