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An ionic liquid (IL), 1-butyl-3-methyl-imiazolium hexafluorophosphate [BMIm]PF6, was coated onto halloysite nanotubes (HNTs) in tetrahydrofuran-water mixture. The IL layers on the HNTs were confirmed by thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectroscopy, determination of contact angle, and porosity analysis. The interaction between IL and HNTs, proposed to be hydrogen bonding, was verified by various spectral results such as Raman spectroscopy, nuclear magnetic resonance and X-ray photoelectron spectroscopy. Because of their interaction, the crystallization behavior of IL in the presence of HNTs was found to be changed, as indicated by the results of differential scanning calorimetry. The IL-coated HNTs (m-HNTs) were used as reinforcement for styrene-butadiene rubber. Compared with the compounds with uncoated HNTs, the uncured compounds with m-HNTs showed faster curing, and the resulting vulcanizates showed substantially higher tensile strength and much lower hardness. The unique changes in the compounds are correlated to the changes in filler dispersion and interaction between IL and HNTs. [ABSTRACT FROM AUTHOR]

Optically transparent composites containing nanotubular clay up to 65 wt%, prepared by a facile “one-pot” process, exhibited high mechanical strength and heat resistance. The attractive characteristics of the composites, in addition to their transparency, include use of low-cost and nontoxic raw materials, easy scaling-up, and possible petroleum independence. The properties of the composites were ascribed to the strong interfacial interactions and the excellent dispersion of nanotubular clay. [ABSTRACT FROM AUTHOR]

Abstract: Methacrylic acid (MAA) was used to improve the performance of styrene–butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed interaction mechanisms of MAA and the in situ formed zinc methacrylate (ZDMA) were revealed by X-ray diffraction (XRD), surface area and porosity analysis, X-ray photoelectron spectroscopy (XPS) together with crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through ZDMA and MAA intermediated linkages. ZDMA connects SBR and HNTs via grafting/complexation mechanism. MAA bonds SBR and HNTs through grafting/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and MAA or ZDMA was achieved. Effects of MAA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of MAA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and MAA or ZDMA and the largely improved dispersion of HNTs. [Copyright &y& Elsevier]

Abstract: Sorbic acid (SA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed mechanisms for the largely improved performance were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), porosity analysis and crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through SA intermediated linkages. SA bonds SBR and HNTs through grafting copolymerization/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and SA was achieved. Formation of zinc disorbate (ZDS) was revealed during the vulcanization of the composites. However, in the present systems, the contribution of ZDS to the reinforcement was limited. Effects of SA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of SA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and SA and the largely improved dispersion of HNTs. [Copyright &y& Elsevier]

Abstract: Non-isothermal crystallization and the polymorphism of the PA6 and the polyamide 6/halloysite nanotubes (PA6/HNTs) nanocomposites are studied by adopting differential scanning calorimetry (DSC) analysis, X-ray diffraction (XRD) analysis and polarized optical microscopy (POM) observations. HNTs act as nucleating agent and accelerate the crystallization. The kinetics analysis indicates that the fold-surface free energy of PA6/HNTs nanocomposites is larger than that of neat PA6. The increasing tendency of the fold-surface free energy of PA6/HNTs nanocomposites is restricted at higher HNTs loading. Interestingly, the crystallinity of the PA6/HNTs nanocomposites increases with cooling rate. HNTs content is found to have a significant effect upon the crystallinity of the PA6/HNTs nanocomposites, and the crystallinity reaches its maximum with 5phr of HNTs content. Moreover, the higher HNTs content is, the larger percentage γ-phase crystals take up. The crystallization behavior of the PA6/HNTs nanocomposites is correlated with the multiple roles of HNTs in the crystallization of PA6. [Copyright &y& Elsevier]

Abstract: Clay-philic benzothiazole sulfide, capable of donating electrons, is grafted onto polypropylene (PP) backbones when N-cyclohexyl-2-benzothiazole sulfonamide (CBS), a commonly used accelerator in the tire industry, is included in the processing of PP/halloysite nanotubes (HNTs) composites. CBS decomposes at elevated temperature and yields benzothiazole sulfide radicals, which react with the PP polymeric free radicals generated during the processing of the composites. On the other hand, the benzothiazole group of CBS is reactive to HNTs via electron transferring. The compatibilization between HNTs and PP is thus realized via interfacial grafting and electron transferring mechanism. The interfacial interactions in the compatibilized systems were fully characterized. Compared with the control sample, the dispersion of HNTs and the interfacial bonding are enhanced substantially in the compatibilized composites. The significantly improved mechanical properties and thermal properties of benzothiazole sulfide compatibilized PP/HNTs composites are correlated to the enhanced interfacial property. The present work demonstrates a novel interfacial design via interfacial grafting/electron transferring for the compatibilization of PP/clay composites. [Copyright &y& Elsevier]

Abstract: A co-coagulation process was utilized to prepare carboxylated butadiene–styrene rubber (xSBR)/halloysite nanotube (HNT) nanocomposites. The interfacial interaction, morphology, and the mechanical performance of the nanocomposites were investigated. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results indicate the formation of hydrogen bonding between xSBR and HNTs. Lower content of HNTs tends to delay the vulcanization of xSBR/HNT compounds, while higher HNT loading promotes the vulcanization. It is shown that HNTs are dispersed individually and uniformly in the matrix with strong interfacial bonding. The mechanical properties, especially the modulus and hardness, are significantly increased by the inclusion of HNTs. The significant reinforcing effects of HNTs are correlated to the co-coagulation process and strong interfacial interactions via hydrogen bonding. [Copyright &y& Elsevier]