Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular s...Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular structure of the novolac-type phenolic resin and the benzoxazine-phenolic copolymer BP31. In order to understand the curing process of the copolymers, the curing behavior and curing kinetic characteristics were studied by differential scanning calorimetry （DSC）, and the catalytical effect of phenolic hydroxyl on the curing behavior of copolymers was investigated. To investigate the thermal properties of this resin, the thermal degradation behaviors of the cured samples were studied by thermal gravimetric （TG） method, and glass-transition temperatures （Tg） of the cured copolymers were also evaluated by DSC. The dynamic Ozawa method was adopted to determine the kinetic parameters of the curing process as well. The activation energy is 78.8 kJ/mol and the reaction rate constant is in the range from 40.0 to 5.2 （K/min）＂ according to reaction temperatures. The Ozawa exponent decreases from 2.4 to 0.7 with the increase of reaction temperature, and curing mechanism is expounded briefly according to the results. TG result shows that the highest char yield of copolymers is 50.3%. The highest Tg of copolymers is 489 K, which is much higher than that of pure benzoxazine resin.展开更多
Carbonation decomposition of hydrogarnet is a significant reaction of the calcification-carbonation new method for alumina production by using low-grade bauxite.In this work,non-isothermal decomposition kinetics of hy...Carbonation decomposition of hydrogarnet is a significant reaction of the calcification-carbonation new method for alumina production by using low-grade bauxite.In this work,non-isothermal decomposition kinetics of hydrogarnet in sodium carbonate solution was studied by high-pressure differential scanning calorimetry(HPDSC) at different heating rates of 2,5,8,10,15 and 20 K·min^(-1),respectively.The activation energy(E_α) was calculated with the help of isoconversional method(model-free),and the reaction mechanism was determined by the differential equation method.The calculated activation energy of this reaction was 115.66 kJ·mol^(-1).Furthermore,the mechanism for decomposition reaction is Avrami-Erofeev(n=1.5),and the decomposition process is diffusion-controlled.展开更多
The fatty acid composition as well as the antioxidant composition and content of two commercially available chia oils of different origins were studied. The purpose of this work was the study of the oxidative stabilit...The fatty acid composition as well as the antioxidant composition and content of two commercially available chia oils of different origins were studied. The purpose of this work was the study of the oxidative stability from different methods and the antioxidant content of the chia oils compared with other commercial oils. The oxidative stability of the oils was determined based on the oxidative stability index test （OSI test） conducted at 110 ~C and isothermal as well as non-isothermal differential scanning calorimeter （non-isothermal DSC） for the chia oil and the linseed oil. The OSI induction time of chia oil was compared with that of commercially available linseed, canola, sunflower and high-oleic sunflower oils, chia oil being the least stable oil among those studied. The inherent stability value and oxidazibility for linseed oil was lower than the chia oil A may be ascribed to a lower linolenic acid content of the former. The induction time （It） quotient at 110 ~C calculated for chia oil A and linseed oil were similar, suggesting a high degree of consistency between the results obtained by the two methods. The activation energy and specific reaction rate constant of chia and linseed oils were compared based on the results of isothermal and non-isothermal DSC. An apparent inconsistency in the experimental data results from the temperature-dependence of the activation energy of each fatty acid which can explain because the methods conditions were different.展开更多
基金Project (20050106) supported by the Key Science and Technology Item of Guangdong Province,China
文摘Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular structure of the novolac-type phenolic resin and the benzoxazine-phenolic copolymer BP31. In order to understand the curing process of the copolymers, the curing behavior and curing kinetic characteristics were studied by differential scanning calorimetry （DSC）, and the catalytical effect of phenolic hydroxyl on the curing behavior of copolymers was investigated. To investigate the thermal properties of this resin, the thermal degradation behaviors of the cured samples were studied by thermal gravimetric （TG） method, and glass-transition temperatures （Tg） of the cured copolymers were also evaluated by DSC. The dynamic Ozawa method was adopted to determine the kinetic parameters of the curing process as well. The activation energy is 78.8 kJ/mol and the reaction rate constant is in the range from 40.0 to 5.2 （K/min）＂ according to reaction temperatures. The Ozawa exponent decreases from 2.4 to 0.7 with the increase of reaction temperature, and curing mechanism is expounded briefly according to the results. TG result shows that the highest char yield of copolymers is 50.3%. The highest Tg of copolymers is 489 K, which is much higher than that of pure benzoxazine resin.
基金Supported by the Joint Funds of the National Natural Science Foundation of China(U1202274)the National Natural Science Foundation of China(51204040)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(201200421100 11)the Doctor Start-up Foundation in Taiyuan University of Science and Technology(20142001)
文摘Carbonation decomposition of hydrogarnet is a significant reaction of the calcification-carbonation new method for alumina production by using low-grade bauxite.In this work,non-isothermal decomposition kinetics of hydrogarnet in sodium carbonate solution was studied by high-pressure differential scanning calorimetry(HPDSC) at different heating rates of 2,5,8,10,15 and 20 K·min^(-1),respectively.The activation energy(E_α) was calculated with the help of isoconversional method(model-free),and the reaction mechanism was determined by the differential equation method.The calculated activation energy of this reaction was 115.66 kJ·mol^(-1).Furthermore,the mechanism for decomposition reaction is Avrami-Erofeev(n=1.5),and the decomposition process is diffusion-controlled.
文摘The fatty acid composition as well as the antioxidant composition and content of two commercially available chia oils of different origins were studied. The purpose of this work was the study of the oxidative stability from different methods and the antioxidant content of the chia oils compared with other commercial oils. The oxidative stability of the oils was determined based on the oxidative stability index test （OSI test） conducted at 110 ~C and isothermal as well as non-isothermal differential scanning calorimeter （non-isothermal DSC） for the chia oil and the linseed oil. The OSI induction time of chia oil was compared with that of commercially available linseed, canola, sunflower and high-oleic sunflower oils, chia oil being the least stable oil among those studied. The inherent stability value and oxidazibility for linseed oil was lower than the chia oil A may be ascribed to a lower linolenic acid content of the former. The induction time （It） quotient at 110 ~C calculated for chia oil A and linseed oil were similar, suggesting a high degree of consistency between the results obtained by the two methods. The activation energy and specific reaction rate constant of chia and linseed oils were compared based on the results of isothermal and non-isothermal DSC. An apparent inconsistency in the experimental data results from the temperature-dependence of the activation energy of each fatty acid which can explain because the methods conditions were different.
