| 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,... |
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