Research Of Surface Activity Of Carbon Black Via Atomic Force Microscope

The reinforcement performance of high structure carbon black is better than ordinary carbon black due to its complicated structure and surface active sites. In this thesis, surface structure and active sites of high structure carbon black was studied in order to learn the reinforcement mechanisim of carbon black profoundly and improve the reinforcement performance of carbon black. Thereby, it has a direct association with development and applications of “green tire”.(1) In this dissertation, DFM mode of atomic force microscope(AFM) was used to morphology characterization of high structure carbon black and analyzation of phase images.The results indicated that: the topography of high structure carbon black was more complex with cross-linked network structrue and botryoidal stucture, especially aggregates of CRX2125, CRX1380 and DZ13 had porous structure as well as CRX1380 with lamella structure. Theses unique structures were scanned and obtained for the first time. While the structure of ordinary carbon black N660 was sperical and oval. DFM phase images reflect the margin of carbon black aggregates clearly, which is a significant supplement of morphology. The results showed that the margin of carbon black aggregates is brighter than the other parts of carbon black, which meaned the edge of carbon black aggregates was viscoelastic and soft.(2) DFM mode of AFM was applied to make a large amount of force curves that analyzed by doing a lot of statistics on the surface of carbon black aggregates, which were treated at different temperature and oxygen. The results indicated that the active sites rates of high structure carbon black CRX1380、CRX2125、N234 were very low while high structure carbon black DZ13, N234 and ordinary carbon black N660 did not exhibite any surface activity at normal temperature and pressure. When carbon black was processed through high temperature and oxygen, surface activity emerged and the rates of active sites were enhanced a great deal. High structure carbon black CRX1380, CRX2125 and DZ13 present surface active sites after dealt with ultra high temperature and vaccum.(3) Element analysis results showed that the oxygen content increased sharply after treated with high temperature and O2. Furthermore, with increasing of the amount of oxygen of carbon black aggregates, the surface active sites rates were improved from the statistical results of DFM force curves. Force curves of high structure carbon black N234, N115 and ordinary carbon black N660, which were processed with 1350℃ in vacuum tube furnance, did not change. That’s to say, the probe tip did not detect the surface active sites. However, the surface active sites of high structure carbon black CRX2125、CRX1380、DZ13 are detcetable. The active sites of high structure carbon black were mainly determined by the surface oxygen containing functional groups and structure itself while the active sites of ordinary carbon black were mainly depended on the surface oxygen containing functional groups. The active sites of carbon black surface were maily distributed in the margin of carbon black aggregates, which had a direct assosiation with the viscoelasticity at the edge of carbon black.