Preparation And Tribological Properties Of Multi-walled Carbon Nanotube And Poly (Ether Ether Ketone) Composites

Poly (ether ether ketone)(PEEK) is a high-performance semicrytallinethermoplastic polymer that displays a unique combination of thermal stability,low flammability, chemical resistance and excellent mechanical properties overa wide temperature range. A wide application of the polymer has been foundsince its commercialization, such as electronics, medicine and transportationindustries. However, it is difficult to use PEEK in pristine form because of itshigh value of friction coefficient and stick-slip behaviour. As a result, thetribological properties of PEEK have to be improved through a modification ofPEEK with appropriate methods. Carbon nanotubes (CNTs) have attracted greatinterest in polymer reinforcement owing to their extremely great mechanical,thermal and electrical properties. The work reported in this thesis was aimed atstudying the effects of surface modification of MWCNTs on compatibilitybetween different MWCNTs and PEEK as well as on dynamic mechanical andtribological properties of MWCNT/PEEK composites systematically. MWCNTs were treated by mixed acids to obtain acid-functionalizedMWCNTs. The acid-functionalized MWCNTs were modified with followingfive different chemical agents separately,1,6-Diaminohexane, hexadecyltrimethyl ammonium bromide, silane coupling agent KH550, anhydroussulfanilic acid and ethanolamine. The MWCNT/PEEK composite films（20wt%of MWCNTs） and MWCNT/PEEK composites (4wt%of MWCNTs) wereprepared in a solution-blending method. The morphology, structures ofMWCNTs and the dispersibility of MWCNTs in different solvents and PEEKmatrix as well as the morphology, thermal properties, dynamic mechanical andtribological properties were investigated.The following conclusions can be drawn:1. Agglomeration happened in acid-functionalized MWCNTs. Thesole-dispersibility of MWCNTs that were modified by the five differentchemical agents respectively was better than that of acid-functionalizedMWCNTs.2. Of the different MWCNT/PEEK composites, the MWCNTs modifiedwith anhydrous sulfanilic acid had an excellent dispersion in the PEEK graftedby sulfonic acid groups and the MWCNTs modified with ethanolamine(e-MWCNTs) were also dispersed well in pure PEEK.3. An introduction of MWCNTs into PEEK matrix could improve thethermal properties of composites, while the thermal properties of differentMWCNT/PEEK composites were similar. 4. The adding of MWCNTs in PEEK matrix could improve the dynamicmechanical properties of the MWCNT/PEEK composites.A clear increase in thestorage modulus of e-MWCNT/PEEK composites (about83.78%at25℃) hasbeen observed. It was also observed that the presence of e-MWCNTs caused anenhancement in the glass transition temperature of the composites (about7℃).5. Wear tests have shown that the value of friction coefficient ofe-MWCNT/PEEK composites was decreased significantly during the test afterthe running-in period (about12%). It is suggested that there was an obviousimprovement in tribological properties of e-MWCNT/PEEK composites.