Layered Silicate / Rubber Nanocomposites Mechanism And Industrialization

"The only judgment of truth is practice". "The science and technology is the most important factor of productive forces". The development of Chinese economic requires that the science and technology come into productive forces as well as research achievements come into industrialized products. The later is one of the most important subjects supported by the National Tenth-five Program and the industrialization of layered silicate/rubber nanocomposites is one of the subjects funded by the National Tenth-five Program. Consequently, studying the industrial technology of producing layered silicate/rubber nanocomposites is significant in theory and practice.Professor Liqun Zhang and his group put forward an easy and efficient method to prepare the layered silicate/rubber nanocomposites, namely "Clay aqueous suspension/rubber latex co-coagulating nanocompounding " (referred to Latex method), which is one of the most important methods to prepare the layered silicate/rubber nanocomposites. Above all, the author carefully researches the mechanism of the lab technology of the latex method in detail, and characters the structure of the nanocomposites prepared by the method. At the same time, the structure and properties of montmorillonite (MMT)/styrene butadiene rubber (SBR) nanocomposites, MMT/natural rubber (NR) nanocomposites, rectorite/SBR nanocomposites, rectorite/ nitrile butadiene rubber (NBR) nanocomposites and rectorite/NR nanocomposites are investigated. Further more, some designs of material structures and preparing process are performed to optimize the properties of the nanocomposites. Eventually, a trial product is performed in a product line of layered silicate/NR nanocomposites designed by author, whose throughput is one thousand ton per year. On the other hand, another product line of rectorite/SBR nanocomposites has been building based on the above results on another place.With the help of X-ray Diffraction (XRD) patterns , Scan Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) micrographs, the process of MMT dispersing in water, the process of MMT aqueous suspension mixing with rubber latex, the process of the mixture co-coagulating and the structure of the material obtained are analyzed. At the same time, the main factors affecting the structure and properties of the material obtained are also considered. The results reveal that the preparing process comprises three main steps, hydratinglayered silicate, mixing the aqueous suspension with rubber latex and co-coagulating the mixing. The first step is the precondition and foundation process and the third step is the key process.The results of XRD and TEM discover that the structure of the nanocomposites prepared by latex method is "separated structure", in which the dispersed phase consists of individual layers and aggregates of silicate layers without the intercalation of rubber molecules into silicate galleries. The statistical average thickness of the aggregates is about l-20nm. The thickness of dispersed phase nearly doesn't change with the increase of filler amount, and there may be a relationship between the thickness of dispersed phase in nanocomposites and in pristine materials.The effect of process on the structure of nanocomposites is studied by applying XRD and TEM. The results show that silicate layers align in two-dimensions along the force exerting direction during the compounding operation on an open mill. The aggregation of the dispersed layers may occur during blending, however, the opportunity to form the regular structure similar to pristine clay is very little. This find is an important supplement for the relationships between structure and properties.The size and concentration of free volume holes of MMT/SBR nanocomposites prepared by latex method (MMT/SBRNC), organic MMT/SBR nanocomposites prepared by melting compouding (OMMT-SBRNC), MMT/SBR micron composites by melting compouding (MMT/SBR MC), and caborn black (N33O) / SBR nanocomposites by melting compouding have been investigated by positron annihilation lifetime spectroscopy (PALS). The relationships of the free volume and the interface of those materials are discussed. The interfacial interaction indeed plays a very important role in the free volume of MMT/SBR nanocomposites. As for MMT/SBR MC, the poor interaction between micrometer MMT and rubber matrix results in the formation of micro-cavities in the interface, which can contribute to the slight increase of Fv. Although there are differences in nano-sized stacking layers between MMT-SBR NC and OMMT-SBR NC, I30 for two nanocomposites are almost the same, which suggests the similar interaction in these two kinds of nanocomposites. For MMT-SBR NC and OMMT-SBR NC, the interaction between nano-dispersed MMT and rubber matrix is ion bond that is stronger than that of MMT-SBR MC, but the number of the bonds is less than that of N330/SBR NC.Therefore, this may cause the Fv of them are larger than that of N330/SBR NC.Applying pristine MMT to prepare nanocomposites is an important characteristic of the latex method. To improve the compatibility of MMT and rubber, macromolecular compatilizer and siliane coupling agent are used. On the other hand, the modifications of MMT layers edges are carried out by chemical or physics methods. The results show that the most efficient modification method is severely stirring to ensure MMT dispersed in water into nano-scale, and then adding macromolecular compatilizer into the mixture. As a modifier during process, siliane KH550 is better than siliane Si69 since the former owns a function group of NH2-. Compared with the MMT/SBR MC, the MMT/SBR NC prepared by optimized process exhibits improved mechanical properties, gas permeability, anti-aging property and flame retardant.Owing to NR being a very important strain-induced crystallizable rubber, the structure and properties of MMT/NR nanocomposites are studied. When the clay content less than lOphr, the presence of nano-MMT induces the development of crystallization of NR on stretching. Compared with the pure NR and the NR composites filled with the same amount of carbon black (N330), MMT/NR nanocomposites exhibit better aging resistance properties (thermal-air aging, ozone aging and photo-oxidation (ultraviolet)). The improvement of aging resistance properties of MMT/NR may be attributed to its excellent gas permeability and improved thermal stability. The cross net work may be more favorable when MMT and carbon black are used together in NR. The introduction of MMT in carbon black filled NR composites may reduce the loading amount of carbon black and improve the properties of NR.Rectorite is a unique layered silicate. To obtain rectorite/SBR nanocomposites with excellent properties prepared by the latex method, rectorite powder must be fully hydrated. Therefore, higher purity of rectorite and lower concentration of rectorite aqueous suspension are favorable. The structure and properties of rectorite/SBR nanocomposites, rectorite/NBR nanocomposites and rectorite/NR nanocomposites are studied. The results of TEM and XRD reveal that these nanocomposites are "separated structure" similar to MMT/rubber nanocomposites. The aspect ratio (area/thickness) of dispersed phase in rectorite system is higher than that in MMT system, which results in higher hardness, higher stress at certain strain, higher tear strength, better anti-aging and lower permeability of rectorite/SBR nanocomposites. Macromolecular compatilizer is also effective on improving the compatibility of rectorite and NR and enhancing its mechanical properties.