18 TH International Conference on Composite Materials NON-ISOTHERMAL NON-ISOTHERMAL NON-ISOTHERMAL NON-ISOTHERMAL CURING CURING CURING CURING KINETIC KINETIC BENZOXAZINE/ KINETIC KINETIC BENZOXAZINE/ BENZOXAZINE/ BENZOXAZINE/ HYDANTOIN HYDANTOIN EPOXY EPOXY RESIN RESIN SYSTEM SYSTEM HYDANTOIN EPOXY HYDANTOIN EPOXY RESIN RESIN SYSTEM SYSTEM LiLing*, Tianjili, Chenjiannan Institute of material science and technology of North University of China, Taiyuan, Chian *LiLing （ iamleeling@126.com iamleeling@126.com iamleeling@126.com ） iamleeling@126.com Abstract: Abstract: Abstract: Abstract: Non-isothermal DSC was examined to follow the benzoxazin/ hydantoin epoxy resin curing reaction. A two-paramenter (m, n) autocatalytic model was found by Malke to describe the cure kinetic of the benzoxazin/ hydantoin epoxy resin. No-isothermal DSC curve obtained using the experimental data show agreement with calculated curve of autocatalytic model. Keywords reaction activation energy; benzoxazion; hydantion epoxy resin; curing kinetic Keywords : reaction Keywords Keywords reaction reaction activation activation activation energy; energy; energy; benzoxazion; benzoxazion; benzoxazion; hydantion hydantion hydantion epoxy epoxy resin; epoxy resin; resin; curing curing curing kinetic kinetic kinetic 1 1 1 1 Introduction Introduction Introduction Introduction cure temperatures and the activation energy of the reaction should be known to get a better control of Epoxy resins with outstanding properties are one the reactions and in consequence to optimize the of the most widely used thermosetting polymers in physical properties of the fjnal products. Cure kinetics automobile industries, shipbuilding, aerospace and of thermosetting resins can be studied by different laminates as adhesives, coatings and matrices of high techniques, in this work the DSC technique was used to performance composite materials. But fire risk is a investigate the kinetics of the benzoxazine/hydantoin major catastrophe of epoxy resins application. epoxy resins cured under nonisothermal conditions. Conventional method is used halogenated compounds with epoxy resin to obtain fmame-retardant materials. 2 2 2 2 Experimental Experimental Experimental Experimental Nevertheless, fmame-retardant epoxy resins containing 2.1 2.1 material material s s 2.1 material 2.1 materials s halogen can produce corrosive and obscuring smoke Formaldehyde aqueous solution (37%), aniline, and may send out super-toxic halogenated bisphenol A were purchased from beijing chemcial compounds with deleterious effects on the Co(China). The benzoxazine resin was synthesized environment and human health [1] . Recently, in according to the reported method [3]. 1-chloro-2, consideration of environmental problems, 3-epoxypropane, 5 ， 5’- dimethylhydantoin were halogen-free retardant epoxy resins have become a purchased from beijing zhonglian chemcial subject of considerable attention, especially laminates, Co(China). from scientists and engineers. Silicon, phosphorus 2.2 Preparation 2.2 2.2 2.2 Preparation Preparation Preparation of of of of hydantoin hydantoin epoxy hydantoin hydantoin epoxy resin epoxy epoxy resin resin resin and nitrogen, is regarded as an environmentally A three-necked fmask equipped with a stirrer, refmux friendly fmame retardant element because it can condenser and a thermometer were added 12.8g of 5 ， reduce the harmful impact on the environment more 5’-dimethylhydantoin and 20g of 1-chloro-2, than the existing materials which halogen atoms (e.g. 3-epoxypropane, 19.1g of isopropyl alcohol was bromine or chlorine) can be used to form some of the stirred. After that, the NaOH was added drop wise most widely applied fmame retardant materials [2] . We in to the mixture in 1h and further reacted at the have synthesized hydantoin epoxy resin, benzoxazine refmux temperature for 5h. The organic phase was resin was employed as a curing reagent, and called distillated isopropyl alcohol. IR(KBr, cm -1 ): 3500 cm -1 benzoxazine/hydantoin epoxy resins. The knowledge (–OH of epxoypropyl), 1769 cm -1 and 1708 cm -1 of the curing kinetics and find a mathematical (C == O), 2985 cm -1 和 2938 cm -1 (—CH 3 of hydantoin ), expression for the cure kinetics are important, when 849cm -1 (epxoypropyl). 1 H-NMR(CDCl 3 ,ppm):1.515ppm modeling the cure kinetics, the curing rates at various 1
18 TH International Conference on Composite Materials (6H, CH 3 of hydantoin ), 2.60-2.98ppm (2H, CH 2 of 1 epxoypropyl), 3.12ppm (H, CH of epxoypropyl), 0.9 5℃/min 0.8 10℃/min 3.55-3.87ppm(2H, CH 2 of N atom of hydantoin). 20℃/min 0.7 0.6 固化率，α CH 3 0.5 0.4 C C O CH 3 0.3 CH CH 2 CH C l 2 H N N H 0.2 O C 0.1 O 0 180 190 200 210 220 230 240 250 260 270 280 290 温度，℃ CH 3 CH 3 CH 3 CH 3 CH 3 C C C C O O CH 3 C C O Fig. 2 Degree of conversion α vs temperature at different CH 2 CH 2 CH CH CH 2 CH 2 N N N N CH 2 CH 2 CH CH CH 2 N N CH 2 CH CH 2 From DSC thermograms obtained information n C C C O O O O H about the curing reaction were get as follows: the O O O 2. 2. 2. 2.2 2 2 2 Differential Differential Differential Differential scanning scanning scanning scanning calorimetry calorimetry calorimetry calorimetry (DSC (DSC (DSC (DSC ) initial curing temperature(T i ), the peak temperature The polymerization behavior of benzoxazine/ (T p ), and the finishing temperature(T f ), Some data on hydantoin epoxy resins was examined using the curing reaction are listed in table1. The curing differential scanning calorimetry (DSC) Q100 from process temperatures of the resin system is important TA Instruments. The reaction mixture was cured in such as gelation temperature (T gel )=145 ℃ , curing DSC under non-isothermal conditions at heating rates temperature (T p )=227.8 ℃ and post-curing( Ttreat ) of 5, 10, and 20 ℃ / min which was heated from 30 up =260.6 ℃ were acquired by DSC extrapolation at to 350 ℃ in a constant flow of nitrogen of 50 ml /min. various heating rates. The heat flow data, as a function of temperature and Tab.1 The Tab.1 Tab.1 Tab.1 The The datas The datas datas for datas for for for curing curing curing curing of of of of benzoxazine benzoxazine / benzoxazine benzoxazine / / / hydantoin hydantoin hydantoin hydantoin time, were obtained using the area under the peak of epoxy resin from DSC thermograms at different rates epoxy resin epoxy epoxy resin resin from from DSC from DSC DSC thermograms thermograms thermograms at at at different different different rates rates rates the exotherm. They were processed further to obtain β ，℃ /min T i / ℃ T p / ℃ T f / ℃ a fractional conversion (α) and the rate of the reaction 5 154.3 233.0 265.7 dα/dt. 10 174.3 249.1 276.5 20 192.6 259.5 286.8 3 Results and discussion 3 3 3 Results Results and Results and and discussion discussion discussion The reaction rate of the kinetic curing process 3.1 3.1 3.1 3.1 Non-i Non-i Non-i Non-isothermal sothermal sothermal sothermal kinetic kinetic kinetic kinetic analysis analysis analysis analysis for resin syetem can be described by Eq. (1) The curing reaction of benzoxazine/yhdantoin α d epoxy resin can be studied by DSC at different = α K ( T ) f ( ) (1) dt heating rates. Fig.1 shows the DSC thermograms at 5, 10, and 20 ℃ /min. Fig.2 is the variation of the Where K(T) is a temperature-dependent reaction rate degree of conversion as a function of temperature at constant, f(α) a dependent kinetic model function, different heating rates. and T is the absolute temperature. The rate constant 40 is temperature dependent according to Arrhenius l aw 5℃/min 30 10℃/min shown in Eq. (2) 20℃/min 20 exothermic, → E = − K ( T ) A exp( a ) (2) 10 RT 0 Where A is the pre-exponential factor and Ea -10 is the apparent activation energy. In non-isothermal -20 150 170 190 210 230 250 270 290 conditions, when the temperature is rise at a constant temperature，℃ heating rate β=dT/dt , Eq. (2) can be modifjed as Fig.1 DSC curveof Benzoxazine/yhdantoin epoxy resin follows: 2
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