| Summary: | 博士 === 逢甲大學 === 化學工程學所 === 94 === Abstract
The cure kinetic parameters of 4,4΄-diaminodiphenylmethane (DDM)-cured or bis(4-amino-3,5-dimethylphenyl)naphthylmethane (BADN)-cured diglycidyl ether of bisphenol A (DGEBA) epoxy and their blends with polysulfone (PSn22， n = 22000 g/mol; PSn16， n = 16000 g/mol) of various compositions were investigated by using dynamic differential scanning calorimetry (non-isothermal DSC).
In the present work the dynamic curing process was applied at various heating rates (10, 20, 25℃/min), and the kinetic parameters, such as apparent rate constants (k1, k2), reaction orders (m, n) and activation energies (E1, E2) were investigated so that the temperature dependence of the reaction can be appreciated clearly, where a modified autocatalytic kinetic was used.
Experiments were conducted at 40-350℃for DGEBA/BADN (A0), and 40-300℃for DGEBA/DDM (B0) and their blend systems. Each run was performed within half an hour in the absence of diffusion-control caused by the vitrification. The kinetic parameters can be obtained rapidly at different reaction regions (i.e., initial, middle, or later). Using the dynamic analysis, the heating rate for each run must be in appropriate ranges, and the simplified nth-order model was considered inappropriate to the epoxy/amine reactions in this study.
Total reaction order and activation energy in the DGEBA/DDM and DGEBA/BADN systems are 0.70-0.95, 51.6 kJ/mol, and 1.20-1.60, 91.3kJ/mol, respectively, which are closed to the values reported in the literature. The activation energies obtained by Kissinger and Ozawa methods were very close and also close to this study for the DGEBA/DDM and PSn22/DGEBA/DDM systems.
The variation of kinetic parameters over the whole range of conversion for the neat epoxy amine-cured (A0) systems was also presented. The first activation energy E1 for the neat epoxy amine-cured is lower than that of the blends with polysulfone systems; however, the second activation energy E2 shows opposite result.
The total reaction order of the PSn22 /DGEBA/DDM, PSn16
/DGEBA/BADN and PSn22/DGEBA/BADN systems are 0.70-0.93, 1.38-1.66, and 1.21-1.57, respectively; for the PSn22 /DGEBA/DDM systems, however, remained the same as that of the neat epoxy. For PSn16 /DGEBA/BADN systems the reaction order of n is 10 times the order of m, and its Tg value is found to be less than that of the B0 system. The lower Tg´s is attributed to the enhanced molecular mobility as a result of plasticization of the crosslinking epoxy network by the PSn.
The variations of total heat of reaction (△H) with the increase of heating rates and the amount of additive are evident; this suggested that the addition of other polymers might also influence the reaction kinetics.
Increasing heating rate, all the samples tested showed a linear increase for rmax, i.e., the maximum reaction rate. The unknown parameters of kinetic for amine-cured systems can be certified in term of the characteristic parameters that were obtained from the proposed method.
It is obvious that the non-isothermal curing process is greatly advantageous than the isothermal curing process.
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