| Cellulose is one of the very rich natural macromolecular materials in nature. In the tropical areas, pineapple leaf fiber is a good source of cellulose. Because of low prices of natural fiber, low density, high Young’s modulus and tensile strength, as well as the biodegradable and renewable characteristics, natural plant fiber has the potential advantages as the reinforcing material, showing a great application prospects in preparation of high performance composite materials, which has attracted scientists’great attention.NCC (nano-crystalline cellulose, NCC), a kind of tiny particles with the partical size between1-100nm. are easily prone to reunion and lose the characteristics of the nano-particles owing to its great specific surface area and the abundant hydroxyl groups on the surface. Therefore, in the practical application surface modification of NCC should be carried out to reduce its surface energy and more different characteristics of the fiber particles could be gained, which can expand the scope of application of the NCC. Natural rubber composites are usually refined by adding the reinforcing agent and the various ingredients to dry glue with the "dry mixing" method, and in the processing, the powder dust causes serious harm to the operator’ health. So the object of this research was to explore a high dispersion, economic and environmentally friendly "latex compounding" method and the "wet" process to prepare the NCC/NR composites.The high-purity NCC with the particle size of30-50nm, high crystallinity and uniform size was obtained with pineapple leaf fiber as raw material by the Sulfuric acid degradation method.Furthermore, the silane coupling agent called silicon-69was used in surface modification and the results of a series of instrumental analysis such as infrared spectroscopy (FTIR), scanning electron microscopy (SEM), particle size analysis, the Zeta-potential analysis, contact angle measurements and thermo gravimetric analysis shows that the silicon69was successfully grafted on NCC, which endowed NCC a better particle dispersion, potential absolute value increasing and better solubility in water.Due to the bridge role of the silane coupling agent, the modified NCC by silicon-69could be coupled tightly with the natural rubber matrix, which formed a cross-linked network structure, and improved the compatibility between the nano-particles and produced high performance NCC/NR nano-composites. In this paper, composites with different percentage compositions was prepared by the wet process of the "latex compounding" method. And the properties of the corresponding composites were characterized by SEM, TGA, dynamic mechanical thermal performance analysis (DMA). It demonstrated that NCC could reinforce natural rubber better, while the modified NCC reinforcing effect was more prominent. When 3%of the modified NCC was added, the tensile strength reached maximum value, up to28.03MPa, which was7.00MPa higher than that of pure natural rubber. At the same time, the tear strength of the composites had been greatly improved, from34.26N/mm for pure natural rubber to79.12N/mm. SEM showed that the modified NCC can be uniformly dispersed in natural rubber matrix, leading a good compatibility. The result of DMA analysis showed that the addition of NCC could improve the rigidity of the material, increase the composite elastic modulus and the glass transition temperature. |
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