Studies On Surface Properties And Resource Recycle Of Pyrolytic Carbon Black From Waste Tires

With the development of polymer industry, how to eliminate the used polymer pollution, reclaim the resource and obtain high extra value of product, are significant in realization of eco-industry and recycling economy. Waste tires are the one of the biggest sources of waste polymer. More attention was paid on the utilization of waste tires at present.Pyrolytic carbon black (PCB) is one of the key products of the waste tires pyrolysis. The economy of the tire pyrolysis process strongly depends on the quality of the PCB, especially its ability to be used in high value commercial areas. How to improve the properties of recovered PCB from the waste tires obtained by atmospheric pyrolysis, increase its value and characterize its application performance, are the main subjects for waste tires pyrolysis technology. We investigated the surface micro-chemical system designing and application studies for resource recycle of PCB by means of many systematical analytical methods. The main results can be summarized as following:1. The routine industrial analysis was performed to determine the bulk elemental composition and physical characteristics of PCB. The results show that PCB has lots of inorganic components and volatile components. Through acid washing the ash content can be reduced greatly. There are more defects on the PCB surface than that on graphite and N880 surface.X-ray photoelectron spectroscopy (XPS) was utilized to examine the surface elemental distribution and chemical structure of PCB in different conditions compared with washed PCB (WPC), commercial reinforcing filler N375 for rubber and a color black from Anshan. XPS analysis shows that there is large amount of ester and short hydrocarbon graft on the surface of PCB.Atomic force microscopy (AFM) was applied to investigate the micro-structure properties of PCB. The surface of PCB consists of plentiful poorly organized amorphous structure with distinct imperfections and distortions and a small quantity of graphite-like layers with ordered six-angle aggregates. Crystallite layers on the surface of PCB are stagger and of cohesion each other. The residual active sites uncovered by ash and carbonaceous deposits on the surface of PCB might exist at the edges of the layers.A "Core-shell model" of PCB was proposed firstly. It shows that the main body of the PCB is the same as the original carbon black filled. The inhomogeneous shellcomprised of inorganic ash and carbonaceous deposits covered the mostly active sites on the surface of PCB, of which polarity is low.2. The principle of the micro-chemical environment design on the surface of PCB was put forward. Methods to replace the relevant commercial materials were developed. The original large a mount of short ester and hydrocarbon grafts with low electronegativity on the surface of PCB were directly used to intensify Cr (VI) adsorption and catalysis process in the wastewater. The appropriate grafts with long chain on the surface of PCB were designed to intensify the interactions between the recycled PCB and natural rubber or resin.3. The three kinds of properties about reinforcing (particle size, structure and iodine adsorption value) of pyrolytic and modified carbon blacks were examined and compared with those of commercial carbon black. The technological quasi-vulcanization time of mixed rubbers with different carbon blacks was determined from the vulcanization curves.The rubber reinforcement properties of pyrolytic and modified carbon blacks were investigated and compared with those of commercial carbon black by means of solid-state high resolution nuclear magnetic resonance (NMR). Four aspects (chemical crosslink structure, relaxation, dipolar correlation effect and self-diffusion) were examined by NMR. The chemical crosslink structures of the vulcanized rubbers with different carbon blacks are similar. Surface grafting intensified the interactions between the carbon blacks and the neighboring polyisoprene chains. The density of chemical cross-links of the vulcanized rubber with modified PCB was greatly improved. After titanate coupling agent modification, the penetrability of the rubber samples was improved.The mechanical testing of the vulcanized rubbers with different kinds of carbon blacks showed the strain of the rubber with modified PCB was improved greatly. The mechanical testing results confirmed the conclusion of the NMR. The PCB modified by the demineralization and NDZ-105 titanate coupling agent could be used to replace the commercial semi-reinforcing carbon black.4. The three kinds of pigment properties (ash content, particle size and volatize content) of pyrolytic and modified carbon blacks were examined and compared with master color black (MCB). Modified PCB has the potential to replace the industrial low color black.The inverse gas chromatography was used to examine the interaction between the pigment and the resin. Inverse gas chromatography at infinite dilution is shownto investigate the dispersive and specific component of surface energy and the thermodynamics function. Inverse gas chromatography at finite concentration has been used to characterize the energy distribution of different active sites. In particular, toluene, polar model probe molecule, is selected as analogy for synthetic resin in to examine the interactions between the modified PCB and the resin. The results show that the modified PCB has stronger adsorption with model probe than MCB.The performances of offset printing ink with different carbon blacks were tested in two different recipes. The results show that the offset printing ink with modified PCB has better fluidity and thermal stability than that with MCB. In addition, the offset printing ink with modified PCB conquers the disadvantages, such as bigger ink fineness, lower production efficiency, worse luster, longer setting time, whiter complexion and higher emulsification ratio than that with the MCB. The PCB modified by the demineralization and NDZ-311 titanate coupling agent could substitute the commercial low color black in offset printing ink.5. One of the most significant applications for PCB recovered is used for the removal of Cr (VI) in the wastewater effluent to control waste by waste. The adsorption kinetic curves of Cr (VI) ion on PCB and commercial activated carbon (CAC) were determined experimentally. The mechanism of the Cr (VI) removal from aqueous solution by carbon was assumed to be the integration of adsorption and catalysis. The adsorption was the rate-controlled step for Cr (VI) removal. Compare to CAC, the weaker repulsive interactions between the surfaces of PCB and the negatively charged HCrCV intensify the adsorption and redox reaction process. The adsorption of Cr (VI) has been identified as pseudo-second order kinetics.