| Summary: | 博士 === 國立臺灣科技大學 === 化學工程系 === 101 === This thesis includes five parts. In the first part, non-isothermal degradation kinetics of the cured polymer samples of N,N′-bismaleimide-4,4′-diphenylmethane (BMI)/barbituric acid (BTA) based polymers in the presence and absence of hydroquinone (HQ) were investigated by the thermogravimetric (TG) technique. By adding 5 wt% HQ into the BMI/BTA polymerization, the activation energy (E) of the thermal degradation process increased significantly in comparison with native BMI/BTA. The thermal degradation kinetics and mechanisms for the native BMI/BTA and BMI/BTA/HQ were quite different.
In the second part, preparation and characterization of phenylsiloxane (PhSLX)-modified bismaleimide/barbituric acid based polymers with 3-aminopropyltriethoxysilane (APTES) as the coupling agent were investigated. The resultant hybrid polymers of BMI/BTA-APTES-PhSLX were characterized primarily by the thermogravimetric (TG) analysis in combination with differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) measurements. The thermal stability of BMI/BTA oligomer was improved significantly by incorporation of a small amount (20-30 wt%) of the copolymer of PhSLX and APTES (PASi). After adequate post-curing reactions, the PASi-modified BMI/BTA oligomers (HYBRID20 and HYBRID30 containing 20 and 30 wt% PASi, respectively) exhibited the greatly reduced thermal degradation rates in the temperature rang 300-800 oC and the increased level of residues at 800 oC as compared to the native BMI/BTA oligomer.
In the third part, the thermal stability of cured samples of organofunctional polysiloxanes including glycidyloxypropyl polysiloxane (GSLX160), aminopropyl polysiloxane (ASLX160), methacryloxypropyl polysiloxane (MSLX160) and vinyl polysiloxane (VSLX160) was investigated. The result showed that these ogranofunctional polysiloxanes showed very different weight loss-vs.-T profiles. As to VSLX160, the weight loss only decreased gradually beyond 450 oC, indicating its superior thermal stability as compared to other polysiloxanes. Thermal degradation was not observed in FTIR measurements for GSLX160, MSLX160 and VSLX160 subjected to thermal treatment at 300 oC over a period of 1 h. By contrast, the amino group-containing ASLX160 underwent degradation when it was treated at 300 oC for 1 h. These results showed that ASLX160 exhibited the worst thermal stability as compared to GSLX160, MSLX160 and VSLX160. The thermal degradation kinetics for GSLX160, ASLX160 and MSL160 were determined by the model-fitting method with the aid of a deconvolution technique. The degradation mechanisms determined for all organofunctional polysiloxanes were quite different.
In the fourth part, non-isothermal radical polymerization kinetics for BTA/bisphenol A diglycidyl ether diacrylate (EA) and benzoyl peroxide (BPO)/EA (serving as the reference) in N-methyl-2-pyrrolidone (NMP) were investigated. The DSC data showed that the activation energy of the polymerization of EA initiated by BTA was much lower than that initiated by BPO. For polymerizations of BTA/EA and BPO/EA except BPO/EA = 3/100 (w/w), the reaction mechanism involving nucleation, followed by nucleus growth in the first stage was proposed. For the polymerization of BPO/EA [3/100 (w/w)], the reaction system was adequately described by the instantaneous nucleation and nucleus growth mechanisms in the first stage. Moreover, the nucleation and subsequent growth of microgel nuclei were primarily governed by the propagation reaction and diffusion-controlled termination reaction for the polymerization system of BTA/EA or BPO/EA. In the second stage (in the conversion range 0.75-0.9), the diffusion-controlled propagation and termination reactions governed the development of highly crosslinked macrogel (i.e., macroscopic agglomerate).
Finally, non-isothermal degradation kinetics of cured polymer samples of BTA/EA and BPO/EA was studied. The cured polymer sample of BTA/EA exhibited an inferior thermal stability as compared to the BPO/EA counterpart (as the reference). The degradation kinetics for cured polymer samples of BTA/EA and BPO/EA were determined by the model-fitting method with the aid of a deconvolution technique. For the cured polymer sample of BTA/EA, the complex degradation process was described by the diffusion-controlled and reaction-controlled mechanisms in the first and second steps, respectively. For the sample of BPO/EA, the mechanism responsible for the first step of the degradation process was reaction-controlled. By contrast, the degradation process was described by the nucleation-controlled mechanism, followed by the multi-molecular decay law in the second step. The different degradation kinetics and mechanisms between cured polymer samples of BTA/EA and BPO/EA were attributed to their different crosslinked network structures.
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