氯化天然橡胶的热降解研究

【作者】 彭政；

【导师】 陈鹰； 李思东； 钟杰平；

【作者基本信息】 华南热带农业大学 ， 农产品加工及贮藏工程， 2001， 硕士

【摘要】 本文用热重分析法（TGA）与红外光谱/热重联用分析法（FTIR/TGA）研究了“胶乳法”与“溶液法”氯化天然橡胶（CNR）的热降解与热氧降解过程，探讨了升温速率（B）与降解温度（T）、降解率（C）的关系，求出了反应级数（n）、反应活化能（E）等反应动力学参数，讨论了气氛对降解反应的影响，比较了“胶乳法”与“溶液法”CNR热稳定性差异。结果表明：1、“胶乳法”CNR的热降解为一步反应，T随B的升高而线性升高，起始降解温度T_o=0.968B+264.3，最大降解速率时即DTG曲线峰值温度T_p=0.860B+293.3，终止降解温度T_f=0.582B+325.0。DTG曲线峰宽随升温速率的升高而减小。最大降解速率时的降解率C_p基本不受B的影响，平均值为34.2%，终止降解率C_f也不受B的影响，平均值为64.8%；2、“溶液法”CNR的热降解为一步反应，T随B的升高而线性升高，T_p=0.894B+275.2，T_o=0.976B+295.3，T_f=0.816B+314.7。DTG曲线峰宽随升温速率的升高而减小。C_p随B的升高而略为增大，平均值为38.3%，C_f不受B的影响，平均值为64.9%；3、“胶乳法”CNR的热降解反应为脱氯化氢反应，n为1.1，E随B升高而线性升高，表观反应活化能E_o为98.6kJ/mol；4、“溶液法”CNR的热降解反应为脱氯化氢反应，n为1.1，E随B升高而线性升高，E_O为99.9kJ/mol。5、“胶乳法”CNR的热氧降解为两步反应，T随B的升高而线性升高，第一步反应的T_o=0.906B+266.6，T_p=0.765B+296.9，T_f=0.734B+318.3，第二步反应的T_o=2.526B+476.7，T_p=3.296B+512.0，T_f=2.808B+547.4。第一步反应的DTG曲线峰宽随B升高而减小，第二步反应随B的升高而加宽。第一步反应的C_P、C_f不受B的影响，平均值分别为37.0%，61.8%，第二步反应的C_P随B的升高而升高，平均值为93.0%，C_f接近100%；6、“溶液法”CNR的热氧降解为两步反应，T随B的升高而线性升高，第一步反应的T_o=0.850B+273.9，T_p=1.210B+290.7，T，＝＝0．976B＋312．5，第 二 步 反 应 的T。二2．216B＋468．3T。＝2．644B＋502．9，T。二2．178B＋531．2。第一步反应的DTG曲线峰宽随B升高而加宽，第二步反应随B的升高而减小。两步反应的C卜C，都不受B的影响，第一步反应C，、C，的平均值分别为37．5％与61．4％，第二步反应的C，为gi．2＄，C。接近100％；7、“胶乳法”CNR的热氧降解反应第一步为脱氯化氢反应，第二步反应为主链氧化断裂，两步反应的n均为二1，E随B的升高而线性升高，第一步反应的民一101．7kjlmol，第二步反应的E广139．IkJ／mol；8、“溶液法”＊＊K的热氧降解反应第一步为脱氯化氢反应，第二步反应为主链氧化断裂，两步反应的n均为1．1，E随B的升高而线性升高，第一步反应E广105．ZkJ／mol，第二步反应E广133．Ikjlmol。9、反应气氛对CNR降解的影响很大，空气和氮气两种气氛中反应的种类和反应机理均不同，反应产物和降解程度也不一样。10、不同工艺制造的 CNR的热稳定性有明显差异，“胶乳法”CNR在低温反应区的热稳定性比“溶液法” CNR差，而在高温反应区则好于“溶液法”CNR。更多还原

【Abstract】 ABSTRACTThe thermal and thermooxidative degradation of chlorinatednatural rubber (CNR) from solution and latex processes were studiedby using of thermal gravimetry (TG) ana1ysis and TG analysiscoupling with infrared spectroscopy. The relations between theheating rates (B) and thermal degradation temperatures (T) andthetmal de8radation rates (C) were studied, the kinetic parameterssuch as the degradation reaction orders (n) and activity ener8y (E)were calculated and the effects of the atmospheres on the degradationwere also discussed. The thermal degradation of CNR from latex wasa one-step reaction. The T increased linearly with the B. The initialtemperature of weight loss (T,) was 0.968B + 264.3, and the finaltemperature of weight loss (Tr) was 0.582B + 325.0, and thetemperature at the maximum weight loss rate (T,) was 0.860B +293 .3.The peak width of DTG curve decreased with the increment of B. Thedegradation rates at T, (C,) and degradation rates at Tf (Cf) were notaffected by B, and the average values were 34.2% and 64.8%,one-step reaction. The T increased linearly with the B. The T, was0.894B + 275.2, and the Tf was 0.8l6B + 3l4.7, and T. was 0.976B+295.3. The peak width of DTG curve decreased with the incrementof the B. The C, increased appreciably with the increment of B andthe average value was 38.3%. The Cf was not affected by B, and theaverage value was 64.9%. The thermal degradation of CNR fromlatex was a reaction of dehydrochlorination with a reaction order (n)of l.l. The reaction activity cnergy (E) increased linearly with theincrement of B and the apparent activity energy (E,) was 98.6kJ/mol.The thermal degradation of CNR from solution was a reaction ofdehydrochlorination with a reaction order (n) of l. l. The E increasedlinearly with the increment of B and E, was 99.9kJ/mol.’ Thethermooxidative degradation of CNR from latex was a two-step34reaction. The T increased linearly with the increment of B. T,, andthe T, and T, of the first step were 0.906B + 266.6, 0.765B + 296.9,and 0.734B +3 l8.3. The T,. T, and T, of the second step were 2.526B+ 476.6, 3.296B + 5l2.0, and 2.808B +547.4. The peak width of theDTG curve of the first step reaction became narrow with theincrement of B. The C, and C, of the first step reaction were notaffected by B, and the average values were 37.0% and 6l.8%respectively. The C, of the second step reaction increased with theincrement of B and its average value was 93.3%, and the Cfapproached to l00%. The thermooxidative degradation of CNR fromsolution was a two-step reaction. The T increased linearly with theincrement of B. The T,, T, and Tf of the first step were 0.850B +273.9, l .2l0B + 290.7, and 0.976B +3l2.5. The T,, T, andT, of thesecond step were 2.2l6B + 468.3, 2.644B + 502.9, and 2. l78B+53l.2. The peak width of the DTG curve of the first step reactionbecame wide with the increment of B, but that of the second stepbecame narrow with the increment of B. The C, and C, of both of thetwo steps were not affected by B, and the average values of C, and C,fOr the first step reaction were 37.5% and 6l.4% respectively. Theaverage value of C, of the second step reaction was 9l .2%, and the C,approached tol00%. The first step of the thermooxidativedegradation of CNR from latex was a reaction of dehydrochlorination,and the second step was an oxidative scission reaction of themolecular main chain. The reaction orders for the two steps of thedegradation were l. l. The E increased linearly with the increment ofB and E, of the first and second steps were l0l.7kJ/mol andl39.lkJ/mol respectively. The first step of the thermooxidativedegradation of CNR from solution was a reaction ofdehydrochlorination, and the second step was an oxidative scissionreaction of the molecular main chain. The reaction orders of the twosteps of the degradation were l. l. The E increased linearly with theincrement of B and the E,更多还原