Abstract
The functionalized multi-walled carbon nanotubes (MWCNT) had been prepared via Friedle-Crafts acylation with maleic anhydride. Raman spectra, X-ray photoelectron spectroscope (XPS), and Fourier transform infrared spectrometer (FT-IR) were utilized to characterize the functionalization of MWCNT. Thermogravimetric analysis (TGA) was used to calculate the organic contents of maleic anhydride modified MWCNT (Mah-g-MWNT), which were 5.05wt%. The composites with MWCNT and poly(methyl methacrylate) (PMMA) were then prepared by the in-situ and ex-situ solution polymerization system. SEM and TEM microphotographs reveal that the MWCNT/PMMA composites process better compatibility and uniform dispersion in the in-situ method system than in the ex-situ method system. MWCNT/PMMA composites prepared by the in-situ method exhibit a lower surface electrical resistivity, a lower volume resistivity, and a lower percolation threshold. The Electromagnetic Interference (EMI) shielding effectiveness (SE) of MWCNT/PMMA composites increased with the increasing of the MWCNT content. Additionally, the in-situ system shows higher EMI SE value, and the Mah-g-MWCNT/PMMA composites exhibit lower EMI SE value than that of the P-MWCNT/PMMA composites. The glass transition temperature (Tg) of PMMA was 87.44oC, and it was increased with the increasing of MWCNT content. Additionally, in the in-situ method system, the Mah-g-MWCNT showed higher Tg (101.31 oC for 4.76wt% P-MWCNT；106.46 oC for 4.76 wt% Mah-g-MWCNT). However, in the ex-situ method system, the Mah-g-MWCNT showed lower Tg (97.40 oC for 4.76 wt% P-MWCNT；96.59 oC for 4.76 wt% Mah-g-MWCNT). The organic contents of PMMA grafted MWCNT in the MWCNT/PMMA composites were calculated by TGA. The in-situ method system processed higher organic contents than in the ex-situ method system. (P-MWCNT/in-situ：8.17 wt%、P-MWCNT/ex-situ：1.12 wt%、Mah-g-MWCNT/in-situ：11.77 wt%、Mah-g-MWCNT/ex-situ：6.69 wt%). Attenuated total reflectance FTIR (ATR-FTIR) was utilized to confirm the quantity of PMMA grafted on the MWCNT. The dynamic mechanical analyser (DMA) showed that the storage modulus of PMMA at 50oC was 503.3 MPa. The storage modulus was increased by the stiffening effect of the MWCNT. The increment of storage modulus in the in-situ method system was higher than that of the ex-situ method system. Additionally, the Maleic anhydride grafted on the surface of MWCNT would improve the load transfer efficiency, which increased the storage modulus. (The storage modulus of 4.76 wt% MWCNT/PMMA composites at 50oC：for P-MWCNT/in-situ is 1047.9 MPa；for P-MWCNT/ex-situ is 994.7 MPa；for Mah-g-MWCNT/in-situ is 1446.6 MPa；and for Mah-g -MWCNT/ex-situ is 1214.6 MPa) The wear resistance decreased at lower MWCNTs loading. However, it was enhanced while the weight fraction of the MWCNT was above the percolation threshold, and the in-situ method system exhibited better wear resistance. Additionally, the Mah-g-MWCNT/PMMA composite in the in-situ method system showed better wear resistance than that of the pristine MWCNT/PMMA composite.