Study on the mechanical property of modified bismaleimides for Kevlar fiber composite.

• Main Authors: T. K. Lin, 林宗寬
• Other Authors: S. S. Shyu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/75340601076918937517

博士 === 國立中央大學 === 化學工程研究所 === 88 === The thermal properties of all the bismaleimides were examined by differential scanning calorimetry (DSC), thermogravimetry (TG) and thermomechanical analysis (TMA). Both 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane (BMPP) and 2,2-bis[4-(4-maleimidophenoxy)phenyl]hexafluoropropane (BMIF) showed a large processing temperature range between their melting points and polymerization initial temperature, which decreased the crosslinking density of the cured resins without significant reduction in their thermal resistance. The structures of BMIs were confirmed through IR and 13C-NMR spectroscopies. The introduction of flexible groups to BMI (BMIF) structure improved the interfacial shear strength of the Kevlar/BMIF composites by microbond pull-out test. The result of microbond pull-out test show that BMIF has larger interfacial shear strength value than 4, 4’-bismaleimidodiphenylmethane (BMI-DMA). p-BMIF showed the lowest dielectric constant and water absorption than both p-BMPP and p-BMI-DMA. The results show that both p-BMPP and p-BMIF have larger interlaminar fracture energy values than p-BMI-DMA. It has demonstrated that the introduction of flexible groups to the BMI structure enhanced the toughness of the Kevlar/bismaleimide composites. The effect of PPO content was not significant change in the thermal stability of BMIF/PPO and BMPP/PPO blends. Kevlar 49 fibers were surface-modified by chlorosulfonation and subsequent reaction of -SO2Cl with some reagents (allylamine, ethylenediamine, and deionized water) to improve the adhesion to 2,2-bis[4-(4-maleimidophenoxy)-phenyl]propane (BMPP) resin. The change in the fiber surface morphology and the surface functional groups introduced to the surface of the fiber were investigated by the scanning electron microscopy (SEM), second ion mass spectrometer (SIMS) and energy dispersion X-ray microanalyzer (EDX), respectively. From the results of SIMS and EDX analysis, they were confirmed that the surface composition of the Kevlar fibers was significantly different from that of the bulk composition. Fiber tensile strengths were found to be strongly dependent on the treatment time and the concentration of chlosulfonic acid. The decrease in fiber strength was significant when the fiber was treated at a high concentration of the reagent for a longer time. The microbond pull-out test was then used to measure the interfacial shear strength (IFSS) between Kevlar fibers and BMPP resin. From the microbond pull-out test, it can be concluded that treatment with 0.2% chlorosulfonic acid for 150s is the optimum chlorosulfonation condition. From the T-peel test, it can be concluded that treatment with 0.08% chlorosulfonic acid for 150s is the optimum chlorosulfonation condition. For the post-treatment reactions with both ethylenediamine and allylamin, the IFSS and T-peel strength were improvement. However, the IFSS and T-peel strength did not increase in the case of water post-treatment. From the interlaminar shear strength (ILSS) test, it can be concluded that treatment with 0.2% chlorosulfonic acid for 90s is the optimum chlorosulfonation condition. The IFSS between Kevlar fibers and BMIF resin increased after ammonia plasma treatment. Kevlar 49 fibers were surface modified by gases (ammonia and nitrogen) plasma treatment to find the optimum condition (30 W, 3 min) for adhesion to BMIF resin. However, the result of microbond pull-out test shows that the IFSS of NH3-plasma treatment is more obvious improvement than that of N2-plasma treatment.