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.
The interactions between the carbon black (CB) and the ionic liquid (IL), 1-butyl-3-methyl-imiazolium hexafluorophosphate ([BMIM+][PF6 −]), are firstly examined. The CB, mixed with the IL via simple blending, is then subjected to microwave (MW) irradiation to prepare the modified CB. The structure evolutions of the modified CB such as the microcrystalline structure and surface chemistry are revealed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and pore analysis. After mixing but before MW irradiation, the microcrystalline arrangement of CB turns to be more ordering and microcrystalline size (La) to be a little bigger but with a limited degree. Under MW irradiation, the IL undergoes severe decomposition. The combination of localized high temperature (proposed to be higher than 425°C) and the decomposition of the IL leads to substantial structure changes of the CB. The graphitization of the CB surface, the disordering of the microcrystalline and the decrease in La are disclosed. In addition, compared with the untreated CB, the CB treated with IL-assisted MW irradiation is found to have much higher volume of the smaller mesopore.
Many types of clay tend to absorb organics via electron transferring interactions between the clay and the organics. This may be utilized to design clay incorporated polymer composites with better interfacial properties. In the present paper, 2,5-bis(2-benzoxazolyl) thiophene (BBT), capable of donating electrons, is selected as the interfacial modifier for polypropylene (PP)/halloysite nanotube (HNTs) composites. The electron transfer between HNTs and BBT are confirmed. The mechanical properties and the unique morphology of the nanocomposites are examined. Formation of fibrils of BBT in the presence of HNTs is found in the nanocomposites. The chemical composition of the fibrils in the nanocomposites is found to be composed of largely BBT and a small amount of HNTs. The formation mechanism of BBT fibrils are elucidated to be the strong interactions between BBT and HNTs under melt shearing. The formation of the BBT fibrils leads to much higher crystallinity compared with previously reported PP nanocomposites. The nanocomposites with BBT show substantially increased tensile and flexural properties, which are attributed to the enhanced crystallinity of the nanocomposites.
The nucleating ability of halloysite nanotubes (HNTs) towards isotactic polypropylene (iPP) was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized optical microscopy (POM) and scanning electron microscopy (SEM). HNTs are identified to have dual nucleating ability for α-iPP and β-iPP under appropriate kinetics conditions. The formation of β-iPP is dependent on the HNTs loading in the iPP/HNTs composites. The composite with 20phr of HNTs is found to have the highest content of β-iPP. Under non-isothermal crystallization the content of β-iPP increases with decreasing of the cooling rate. The maximum β-crystal content is obtained at cooling rate of 2.5°C/min. The supermolecular structure of the β-iPP is identified as β-hedrites with flower-cup-like and axialite-like arrangements of the lamellae. Under isothermal crystallization the β-crystal can be formed in the temperature range of 115–140°C. Outside the temperature range, no β-iPP can be observed. The content of β-crystal reaches the maximum value at crystallization temperature of 135°C. The formation of the β-iPP in the composites is correlated to the unique surface characteristics of the HNTs.
No abstract is provided for this article.
Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo-montmorillonite (O-MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The dispersion state of the MMT in the matrix was investigated by X-ray diffraction and scanning electronic microscopy. The thermal stability of the epoxy nanocomposites was examined by TGA. Thermal stability of the epoxy nanocomposite is dependent upon the dispersion state of the OMMT in the epoxy matrix although all the epoxy nanocomposites had enhanced thermal stability compared with the neat epoxy resin. The thermal stability of the epoxy resin nanocomposites was correlated with the dispersion state of the MMT in the epoxy resin matrix.
Radical-scavenging carbon nanodots (CDs) were loaded into the 50 nm diameter natural halloysite clay tubes to fabricate low toxic CD-delivery vehicles for elastomer composites with sustained antiaging functionality. Then, 2 nm diameter carbon nanodots released from the halloysite lumens interacted with reactive radicals, generated at the initial stage of oxidative processes, which significantly improved thermo-aging resistance of the elastomers. The antioxidative efficiency of these CD-delivery vehicles was further increased through the nanotubes' surface modification with a thin grafted-silane shell, which allowed the slowing of the release rate, thus extending the protection. This nanoarchitectural design of the carbon dot-loaded clay nanotubes doped at 9 wt % into a rubber matrix allowed for sustained radical-scavenging and provides a new strategy for long-lasting elastomer protection. Our antiaging rubber nanoformulation based on a natural tubule clay and biocompatible CDs can decrease the environmental hazards of conventional petrol-derived antioxidants. Such clay core–shell systems may also be useful for biocompatible encapsulation of often-poisonous nanodots providing safe biomarkers.
Surface modification of fillers has a profound influence on the dispersion of filler and interfacial adhesion, and thus the final performance of polymer-based composites. In this contribution, the modification of silica by polymethylhydrosiloxane (PMHS) is conducted via an efficient and fast tris(pentafluorophenyl)borane-catalyzed functionalization, which can be completed within a few minutes at room temperature. A highly hydrophobic surface and an uncompromised reactivity are concurrently observed in the modified silica. By comparison between the composites filled with pristine and modified silica, it is revealed that such PMHS modification can not only improve the dispersibility of silica by lowering the surface energy, but also enhance the interfacial interaction in virtue of the reactivity of the residual SiH bonds. With a PMHS grafting content as low as 1.5 wt%, the modified composite exhibits tremendous improvements in mechanical properties (116% increase in modulus) and dynamic performances (116% increase in wet traction and 26% reduction in rolling resistance). Considering the superior overall performance of the modified composites, together with the simplicity and rapidity of the modification process, we envision that the hydrosilane-modified silica has great potential in the fabrication of high-performance polymer composites such as energy-saving tire treads.
