Investigation on failure modes for pin joints made from unidirectional glass–epoxy nanoclay laminates

In the present work the effect of the nanoclay on the bearing strength and failure mode of the pin joints was investigated both experimentally and numerically. Geometric parameters, i.e. the distance from the free edge of specimen to the diameter of the first hole (E/D) ratio and width of the specimen to the diameter of the holes (W/D) ratio were investigated. The E/D and W/D ratios were varied from 1 to 5. Tsai–Wu failure criterion with characteristic curve method and progressive damage analysis was used for the prediction of failure modes. Results showed that bearing strength and failure mode were considerable affected by the wt% of nanoclay and the geometric parameters. A good agreement was obtained between experimental and numerical predictions.     

A study on UV-protection property of poly(vinyl alcohol)-montmorillonite composite nanofibers

The aim of this research is to investigate the possibility of barrier effect of poly(vinyl alcohol) (PVA)/montmorillonite (MMT) nanofiber, against the UV radiation in different electrospinning situations. For this purpose, nanofibers with different weight ratio of PVA and nanoclay (MMT) were electrospun under different circumstances, and the amount of protect that is created by the nanofiber web against UV radiation by examining the rate of degradation of methylene blue dye that was protected by the same web was estimated. The UV-vis spectrometry was used for the analysis of methylene blue color. In order to investigate the morphology and miscibility of PVA-MMT composite nanofiber, X-ray diffraction, scanning election microscope, and Fourier transform infrared spectrometer have been used. Thermal gravimetric analysis is used to investigate and explore how nanofibers behave against heat.     

Synthesis,characterization of hexagonal boron nitride nanoparticles decorated halloysite nanoclay composite and its application as hydrogen storage medium

In the emerging front of research, much attention is focused on the usage of hydrogen as a promising alternative energy carrier that can potentially replace fossil fuels. Conversely, the realization of hydrogen as an energy carrier becomes impounded since the light weight and compact hydrogen storage materials are still prerequisites for hydrogen fuel cell technology. In the present study, the performance of nanoclay composites composed of acid treated halloysite clay nanotubes (A-HNTs) and hexagonal boron nitride nanoparticles (h-BN) are investigated towards hydrogen storage. where facile ultrasonic approach was adopted. The prepared A-HNT–h-BN nanoclay composites subjected to various characterization techniques such as X-ray Diffraction (XRD), micro–Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), UV–Visible Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Spectroscopy (EDX) and High Resolution Transmission Electron Microscopy (HRTEM) with Selected Area Transmission Electron Diffraction (SAED). The presence of h-BN nanoparticles at the surface of A-HNTs can be seen from HRTEM images and these findings are supported by XRD, FTIR and Raman results. Hydrogen adsorption studies are performed using Sieverts-like hydrogenation setup. A 2.88 wt% of hydrogen storage capacity and 100% desorption were achieved for the A-HNT–5wt% h-BN nanoclay composite at 50 °C. The adsorbed hydrogen possess the average binding energy of 0.33 eV, which lies in the recommended range (0.2–0.4 eV) for fuel cell applications. So it is expected that A-HNT–h-BN nanoclay composites will serve as a better hydrogen storage material for fuel cell applications in the near future.     

Kinetic studies of the preparation of nanocomposites based on encapsulated Cloisite 30B in poly[styrene‐co‐(butyl acrylate)] via mini‐emulsion polymerization

Mini‐emulsion polymerization of poly[styrene‐co‐(butyl acrylate)] encapsulating various contents of Cloisite 30B was performed. The kinetic behaviours of mini‐emulsions were investigated using the gravimetric method and the effect of nanoclay content on the polymerization rate was investigated. The average number of radicals per particle was estimated by calculating the number of particles. The results showed that by increasing the nanoclay content, the average diameter of polymer particles increased. Studies of the polymerization rate indicated that the increase in particle size provided a greater average number of reactive radicals per polymer particle, which increased from 0.0520 for the neat copolymer to 0.2462 for the nanocomposite containing 5.3 wt% encapsulated nanoclay. This study also confirmed our previous claim about the role of sodium dodecylsulfate (SDS) molecules in the exfoliation of nanoclay platelets. On increasing the clay content, fewer SDS molecules will be available on particle surfaces resulting in larger particles at the end of the reaction. Copyright © 2011 Society of Chemical Industry     

纳米改性剂增强聚丙烯阻燃性能机理综述

为了提高聚丙烯阻燃性能,对炭纳米管、黏土、C60、富勒烯、聚倍半硅氧烷改性聚合物的阻燃性能和力学性能进行了综述,系统地归纳了5种纳米改性剂的阻燃机理。指出:目前任何一种阻燃剂都有自身缺陷,未来所需要的PP用阻燃剂不仅要大幅提高其阻燃性能,同时还要提高力学性能、热性能及其他物理性能。今后应深入研究纳米阻燃剂的表面改性技术,解决分散性、界面黏结性等问题,以减少其劣化材料力学性能的影响,提高阻燃效率。     

Modeling the delamination process during shear premixing of nanoclay/thermoset polymer nanocomposites

As shear premixing is an important process for the dispersion of nanoclays in polymeric resins, this article studies the effect of temperature, duration, speed of premixing, and also the interlamellar spacing of clay platelets on the dispersion of organoclay in epoxy by using a high speed premixing technique which can generate high shear. The quality of dispersion and intercalation/exfoliation of organoclay in epoxy after premixing (before adding hardener) was analyzed by means of X‐ray diffraction (XRD) and rheological measurement. The dispersion and intercalation/exfoliation of organoclay in the epoxy nanocomposites (ENCs) after curing were characterized by TEM. The results illustrate that the intercalation/exfoliation of organoclay in epoxy at the premixing step is very much depending on the premixing parameters. This article also presents a model which takes into account the parameters such as the interlamellar spacing of clay platelets, the viscosity of the epoxy‐clay mixtures, and the velocity of the mixer to explain their effect on the dispersion of clay in epoxy resin. The study focuses on the flow of epoxy clay in the high shear mixer to describe a model for predicting the processing conditions necessary for achieving delamination of the clay layers. Experimental results on the dispersion of clay are also provided to validate the model. The model provides a guide for the premixing parameters necessary to separate the clay layers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

全互穿半乳糖基水凝胶的制备与细胞活性研究

采用两步法,分别以无机纳米粘土硅酸镁锂(LMSH)和亚甲基双丙烯酰胺(MBA)作为异丙基丙烯酰胺(NIPAm)和氨基半乳糖丙烯酸衍生物(GAC)的物理和化学交联剂,制备得到全互穿的P(NIPAm/LMSH)/P(GAC/MBA)水凝胶;采用红外光谱、扫描电镜和称重法研究了全互穿水凝胶的化学结构、内部孔洞、(消)溶胀和温度脉冲响应性行为,并探索了凝胶表面的细胞活性.结果表明:全互穿水凝胶孔洞数量多,尺寸为20~30μm;10 min内溶胀度增加1.4倍,失水率超过60%,并表现出良好的温度脉冲响应性,且随脉冲次数的增加,溶胀度逐渐下降;鼠成纤细胞(L929)培养结果表明2~8 d内水凝胶表面细胞数量逐渐增加,但低于聚苯乙烯组织培养板(TCPS)上的细胞数量.     

Polymer nanocomposites based on needle‐like sepiolite clays: Effect of functionalized polymers on the dispersion of nanofiller,crystallinity, and mechanical properties

Polypropylene (PP)/sepiolite (Sep) nanocomposites are prepared by melt compounding in a mini‐extruder apparatus. The often used maleic anhydride‐modified polypropylene (PP‐g‐MA) is compared with two custom‐made functionalized polymers, PP‐acid and the di‐block copolymer PP‐PEO, with respect to the filler dispersion and filler reinforcement efficiency. For that purpose, morphological and mechanical studies are carried out by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical tensile tests. In addition, the nanocomposites are characterized by wide‐angle X‐ray scattering (WAXS) and differential scanning calorimetric (DSC) techniques, to assess the effect of the nanofiller on the crystalline structure of the PP matrix nano‐filler. The use of PP‐PEO and PP‐acid resulted in a better nanofiller dispersion compared with traditional PP‐g‐MA‐modified systems. Sepiolite acts as nucleating agent for the crystallization of PP and seems to lead to an orientation of the α‐phase crystals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

The rheological behavior of bitumen and moisture susceptibility modified with SBS and nanoclay

The effect of styrene–butadiene–styrene (SBS) and nanoclay additive on performance of pure bitumen and stone matrix asphalt (SMA) mixture was investigated. Different samples with various percentages of nanoclay (2%, 3%, 4%, and 5%) and SBS (0% and 5%) by weight of bitumen were prepared, and the rheological and chemical behavior of bitumen (rotational viscosity, dynamic shear rheometer, SEM, and FTIR), the indirect tensile strength and moisture susceptibility of different mixtures were evaluated. Based on the results, using nanoclay and SBS polymer can improve the rheological behavior of base binder and the resistance of SMA mixtures against moisture damage.     

Effect of nanoclay on fatigue life of hot mix asphalt

The aim of this research is to investigate effect of two types of nanoclay additives, namely Cloisite 15-A and Cloisite 30-B, on fatigue life of asphalt mixes. Indirect tensile-resilient modulus and four-pointed beam fatigue tests were employed for this purpose. Results of both tests indicated that nanoclay additives improve fatigue life at 25°C but they have negative impact on it at 5°C. Moreover, Cloisite 15-A was found more effective at both temperatures regarding fatigue life.