Preparatian And Properties Of Natural Ubber Filled With Carbon Nanotubes

Carbon nanotube (CNT) is recognized as the ideal filler for rubberymaterials owning to its unique structure and outstanding performances.Nevertheless, it is difficult to disperse CNTs homogeneously in matrix andhard to form strong interface bonding between CNTs and polymer, thatresult from the highly entangled agglomerates of CNTs and its chemicalinertness. In order to improve the dispersion of CNTs and enhance theinterface bonding, four main aspects of research work have been studied:1. Pristine mutli-wall carbon nanotubes (MWCNTs) have been modified bypolydopamine (PDA) coating. High resolution transmission electronmicroscope (HR-TEM) was operated to observe the morphologies ofMWCNTs before and after modification, thermo gravimetric analysis (TGA)was used to investigate the covering amount of PDA and X-rayphotoelectron spectroscopy (XPS) was used to determine the change ofsurface elements. The HR-TEM images showed that there was anamorphous polymeric layer on the surface of MWCNTS modified bypolydopamine (MWCNTs-PDA), and the covering quality accounted for at least13%from the results of TGA. The increase of oxygen and nitrogenelements revealed that the functionalized degree of MWCNTs have beenenhanced after modification. After observing the dispersion and depositionof MWCNTs-PDA in water, it could be concluded that the PDA coating washelpful to improve the hydrophilcity of MWCNTs;2. Carbon nanotubes/natural rubber (CNTs/NR) composites were preparedby latex compounding. And the influences of technological parameters justas the demulsifier and its dosage, the solid content of mixed latex on theflocculation process and the productivity of masterbatch were researched indetail. And it was confirmed that using dilute sulphuric acid with3wt%fordemulsification of the mixed latex with10%solid content was the optimalcombination.3. HR-TEM and scanning electron microscope (SEM) were used to observethe dispersion of CNTs in NR. And the properties of NR composites (just ascuring behavior and crosslink density, static and dynamic mechanicalproperties, electrical and thermal conductivities, thermal stability) weremeasured completely and systematically. HR-TEM and SEM imagesshowed that the MWCNTs-PDA dispersed uniformly in the NR, but theMWCNTs existed as the form of agglomerates. The MWCNTs-PDA/NRcomposite gained greater enhancement in tensile strength and elongation,and showed obvious percolation threshold in electrical conductivity andexcellent thermal stability. MWCNTs brought more increase on the crosslink density and storage modulus of NR. But a small quantity of CNTs(whether MWCNTs or MWCNTs-PDA) could not drastically improve thethermal conductivity of NR;4. Silane coupling agents were used to strengthen the interface bondingbetween MWCNTs-PDA and NR. SEM was operated to characterize thetensile fracture surface of composites. The effects of coupling agents on thecuring behavior, static and dynamic mechanical properties of NR werestudied completely. The SEM images showed that the coupling agentsimproved the compatibility between MWCNTs-PDA and matrix. And stress(at certain strain) of composites gained more enhancements after addingcoupling agents, but the tensile strength had changed little. The elongation ofcomposite which mixed with Si69decreased significantly, that could beattributed to the increase of crosslink density.And the storage modulus of composites rose slightly and the loss factordeclined a bit as the adding of coupling agents.Moreover, the effects of sulphur and vulcanizing agents on thedispersion of CNTs in rubber solution have been investigated briefly. Andthe TEM images showed that the addition of zinc oxide (ZnO) could makethe aspect ration of CNTs lower and sulphur could play a part in untanglingof CNTs.