Causin Valerio, Yang Bing-Xing, Marega Carla, Goh Suat Hong, Marigo Antonio
Department of Chemical Sciences, University of Padova and INSTM Research Unit, via Marzolo 1, 35131 Padova, Italy.
J Nanosci Nanotechnol. 2008 Apr;8(4):1790-6.
Polyethylene-grafted multiwalled carbon nanotubes (PE-g-MWNT) were used to reinforce polyethylene (PE). The nanocomposites possessed not only improved stiffness and strength, but also increased ductility and toughness. The effects on the structure and morphology of composites due to pristine multiwalled carbon nanotubes (MWNT) and PE-g-MWNT were studied and compared using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The SAXS long period, crystalline layer thickness and crystallinity of polymer lamellar stacks were found to decrease significantly in MWNT composites, while the decreases were much smaller in PE-g-MWNT composites. PE-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. The SAXS crystallinity and the mechanical properties of the composites showed similar trends as a function of MWNT content. This suggested that the improvement of the interfacial strength between polymer and carbon nanotubes was a result of synergistic effects of better dispersion of the filler, better stress transfer, due to the grafting of polymer and MWNT, and the nucleation of a crystalline phase around MWNT. The latter effect was confirmed by measurements of kinetics of non-isothermal crystallization.
聚乙烯接枝多壁碳纳米管（PE-g-MWNT）被用于增强聚乙烯（PE）。该纳米复合材料不仅具有提高的刚度和强度，还具有增加的延展性和韧性。使用小角X射线散射（SAXS）、广角X射线衍射（WAXD）和差示扫描量热法（DSC）研究并比较了原始多壁碳纳米管（MWNT）和PE-g-MWNT对复合材料结构和形态的影响。发现在MWNT复合材料中，聚合物片层堆叠的SAXS长周期、结晶层厚度和结晶度显著降低，而在PE-g-MWNT复合材料中这些降低要小得多。PE-g-MWNT在片层水平上允许更有效且不受阻碍的结晶，而MWNT可能由于其聚集倾向破坏了片层堆叠的有序性。复合材料的SAXS结晶度和力学性能随MWNT含量呈现相似的趋势。这表明聚合物与碳纳米管之间界面强度的提高是填料更好分散、由于聚合物和MWNT接枝导致更好的应力传递以及MWNT周围结晶相的成核等协同效应的结果。通过非等温结晶动力学测量证实了后一种效应。
