Preparation and properties of carbon nanotube/polyurea-urethane composites

• Main Authors: Chung-Hao Wang, 王崇豪
• Other Authors: Chen-Chi M.Ma
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/66036770593085394311

碩士 === 國立清華大學 === 化學工程學系 === 94 === The functionalized multiwall carbon nanotube (MWNT) has been prepared by free radical reaction with maleic acid or maleic anhydride. The functionalized MWNT was further blended with poly(dimethylsiloxane) (PDMS) based Polyurea-urethane (PUU). Both maleic acid modified MWNT (Maa-g-MWNT) and maleic anhydride modified MWNT (Mah-g-MWNT) showed enhanced dispersion compared with that of pristine MWNT and PUU. PUU containing end capped PDMS soft segment has been synthesized successfully and was monitored by Fourier transform infrared spectrometer (FT-IR). Different functional groups were grafted onto the multi-wall carbon nanotube (MWNT) by free radical method. Raman spectra and FT-IR were utilized to characterize the functionalized MWNT. Thermal gravimetric analysis (TGA) was used to calculate the organic contents of functionalized MWNT, which were 5.39wt% and 6.63wt% for Mah-g-MWNT and Maa-g-MWNT, reapectively. The morphology of MWNTs can be observed by scanning electron microscope (SEM). MWNTs were blended with PUU to obtain MWNT/PUU nanocomposite sheet, and the properties of the nanocomposites such as morphology, molecular mobility, EMI Shielding effectiveness, mechanical property, thermal property were investigated. The SEM microphotographs showed the bottom side and fracture side morphology of 5phr MWNTs/PUU nanocomposites. The microphotographs of bottom side presented the dispersion of MWNTs in PUU polymer matrix. The pristine MWNT was easily entangled in PUU polymer. The Maa-g-MWNT/PUU was dispersed better than that of Pristine MWNT. The SEM microphotographs of fracture side Pristine/PUU, Maa-g-MWNT/PUU, and Mah-g-MWNT/PUU were shown wave-frectured patterns, indicating the composites containing more flexibile composites. These wave patterns could be observed in Maa-g-MWNT/PUU, while the patterns of Mah-g-MWNT/PUU were clearier and uniform. The TEM microphotographs of pristine MWNT showed which was incorporated with carbon black in polymer matrix while the modified MWNTs showed hollow fiber microstructure clearly. 13C solid state NMR spectra explicated that the shorter the T1ρH value, the higher the molecular mobility of composites. Consequently, the molecular mobility of the nanocomposites was in the following sequence Mah-g-MWNT/PUU > Maa-g-MWNT/PUU > Pristine MWNT/PUU, because of the hydrogen bonding. DMA results indicated that the glass transition temperature (Tg) MWNTs/PUU composites were decreased comparing to that of pristine PUU because of the reduced cross-linking density. Low content of MWNT displayed poor connection of conducting path which led to lower electromagnetic interference Shielding effectiveness (EMI SE) ranging between 200 and 1800MHz. On the other hand, it was found that three kinds of MWNTs/PUU nanocomposites pocessed good EMI absorption properties at higher range of frequency (18-40GHz). Results showed that MWNT/PUU nanocomposites with higher content of MWNTs possess higher EMI SE and the lower the range of half height width of the peak. Moreover, the frequency of max absorption shifted to a lower value with the increasing of MWNT contents. Results also showed that the values of EMI SE and their corresponding peaks were -17.5dB at 25GHz, -19.2dB at 26 GHz, and -22dB at 23.5GHz with 5 phr MWNTs of pristine MWNT, Maa-g-MWNT, and Mah-g-MWNT in MWNT/PUU composites, and their half height width was 6.0GHz, 4.0GHz, and 3.8GHz, respectively. When the thickness of the composites films were doubled (about 1.4mm), the maxium absorption frequency EMI SE also shifted to lower values, which possessed smaller frequency range of half height width. The tensile strength and Young’s modulus of MWNT/PUU nanocomposites were improved, significantly. The tensile strength and the Young’s Modulus of 5phr of Pristine MWNT/PUU composites were from 7.2 MPa and 28.0MPa to 13.9 MPa and 55Mpa, respectively. Similarily, they were increased to 14.1MPa and 62.5MPa for Maa-g-MWNT and to 14.8MPa and 66.1MPa for Mah-g-MWNT. Mah-g-MWNT showed the best dispersion which was corresponding to the improvement of mechanical properties. Thermal degradation properties were measured by TGA which displayed 10% weight loss temperature (Td10) MWNT/PUU of composites could be enhanced by the addition of MWNTs. The Td10 temperature of 5phr of Pristine MWNT/PUU, Maa-g-MWNT/PUU, and Mah-g-MWNT/PUU composites were increased from 265.4 oC to 279 oC, 285.2oC, and 287.2 oC respectively.