Preparation Of Hybrid Functionalized Carbon Nanotubes/Polyurethane Composites

Carbon nanotubes (CNT) are one of the best promising reinforcement materials for polymer composites due to their unique structure and extraordinary physicochemical properties. However, their applications to polymer composites are limited because of the easy formation of aggregates and rather weak interfacial interactions between CNT and polymer matrix. In order to improve the dispersion and the interfacial behavior of CNT in polymer matrix and synthesize high-performance polymer composites, we firstly studied the effect of experimental temperature and modification of Methylene-bis-ortho-chloroanilline (MOCA) on the structure and properties of CNT; Through the esterification reaction on the basis of oxidization of multi-walled carbon nanotubes (MWNT-COOH), the MWNT-based macroinitiators, MWNT-Br was produced, and then the atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) was initiated to produce the MWNT wrapped by poly-(glycidyl methacrylate) (MWNT-g-PGMA); Under the guidance of hybrid functionalization, We synthesized different temperature oxidization of MWNT coated by PPA. Finally, the dependence of mechanical and thermal properties of PU composites on the content of different MWNT was investigated. The main results are:(1) The active groups(-COOH, -OH) could be grafted to the MWNT via oxidation with a mixture of concentrated sulfuric acid and nitric acid at different temperature. In addition, the drafted amount of active groups and dispersion effect could be enhanced with higher temperature. Raman spectra analysis of pristine MWNT, 50℃oxidization of MWNT (MWNT-COOH(Ⅰ)), refluxing-temperature oxidization of MWNT (MWNT-COOH(Ⅱ)) indicated that the oxidation treatment generated defects and reduced the structural order degree of MWNT. The MOCA had been drafted to the oxidized MWNT in one-step with the aid of condensation agent N,N'-dicyclohexylcarbodiimide (DCC).(2) The morphological structures of MWNT-g-PGMA were examined by Transmission Electron Microscope (TEM). It was clearly observed that the PGMA was grafted to the MWNT via the ATRP through the TEM images.(3) We got the hybrid functioanlization MWNT coated by PPA through the ultrasonic dispersion treatment for 5 hours, it has a better dispersion than the MWNT-COOH.(4) The thermal properties of polyurethane (PU) composites have relation to the category of functionalized MWNT (f-MWNT). When MWNT or MWNT/PPA was added to the matrix, the thermal properties of PU composites declined. When MWNT-COOH, MOCA-grafted MWNT or MWNT-COOH/PPA was added to the matrix, the temperature of initial decomposition increased and the thermal properties of PU composites were improved.(5) The category and content of f-MWNT have great influence on the tensile strength of PU composites. When the reinforcement was MWNT or MWNT/PPA, the mechanical properties of PU composites declined; When the reinforcement was MWNT-COOH(Ⅰ) or MWNT-COOH(Ⅰ)/PPA, the tensile strength of PU composites increased. The curve of tensile strength and the content of f-MWNT fell after raising, and the optimum content was 0.2wt%; When the reinforcement was MWNT-COOH(Ⅱ), MOCA-grafted MWNT or MWNT-COOH(Ⅱ)/PPA, the tensile strength of PU composites increased more, and the optimum content was 0.3wt%. Comparing the tensile strength of all kinds of PU composites, MWNT-COOH(Ⅱ)/PPA/PU had the maximum tensile strength.