Cross model correlates the dynamic complex viscosity of polymer systems to zero complex viscosity, relaxation time and power-law index. However, this model disregards the growth of complex viscosity in nanocomposites containing filler networks, especially at low frequencies. The current paper develops the Cross model for complex viscosity of nanocomposites by yield stress as a function of the strength and density of networks. The predictions of the developed model are compared to the experimental results of fabricated samples containing poly(lactic acid), poly(ethylene oxide) and carbon nanotubes. The model’s parameters are calculated for the prepared samples, and their variations are explained. Additionally, the significances of all parameters on the complex viscosity are justified to approve the developed model. The developed model successfully estimates the complex viscosity, and the model’s parameters reasonably change for the samples. The stress at transition region between Newtonian and power-law behavior and the power-law index directly affects the complex viscosity. Moreover, the strength and density of networks positively control the yield stress and the complex viscosity of nanocomposites. The developed model can help to optimize the parameters controlling the complex viscosity in polymer nanocomposites.

An artificial neural network (ANN) model is developed for the analysis and simulation of correlation between flake powder metallurgy parameters and properties of AA2024-SiC nanocomposites. The input parameters of the model are AA 2024 matrix size, ball milling time, and weight percentage of SiC nanoparticles and the output parameters are density and hardness. The model can predict the density and hardness of the unseen test data with a correlation of 0.986 beyond the experimental data. A user interface is designed to predict properties at new instances. We have used the model to simulate the individual as well as the combined influence of parameters on the properties. Moreover, we have analyzed the calculated results from the powder metallurgical point of view. The developed model can be used as a guide for further composite development.

Effects of multi-walled carbon nanotube (MWCNT) type and flow type (shear and elongational flow) on the electrical conductivity of polycarbonate (PC)/MWCNT nanocomposites were investigated. Two different MWCNTs produced a huge difference in electrical conductivity in an injection molded PC/MWCNT nanocomposite. It was observed that MWCNTs having a higher aspect ratio provide much lower electrical conductivity in injection molded PC/MWCNT nanocomposites while the conductivities of compression molded samples from two different MWCNTs were the same. We found that this is due to a difference in the deformability of the two MWCNTs. Nanocomposite samples prepared at a higher extensional rate and shear rate showed lower electrical conductivity. This is attributed to flow induced orientation of the MWCNTs. The experimental results were discussed in relation to variation in the tube–tube contact due to the change of the MWCNT orientation.

Gold functionalized graphene oxide (GOAu) nanoparticles were reinforced in acrylonitrilebutadiene rubbers (NBR) via solution and melt mixing methods. The synthesized NBR-GOAu nanocomposites have shown significant improvements in their rate of curing, mechanical strength, thermal stability and electrical properties. The homogeneous dispersion of GOAu nanoparticles in NBR has been considered responsible for the enhanced thermal conductivity, thermal stability, and mechanical properties of NBR nanocomposites. In addition, the NBR-GOAu nanocomposites were able to show a decreasing trend in their dielectric constant (ε´) and electrical resistance on straining within a range of 10–70%. The decreasing trend in ε´ is attributed to the decrease in electrode and interfacial polarization on straining the nanocomposites. The decreasing trend in electrical resistance in the nanocomposites is likely due to the attachment of Au nanoparticles to the surface of GO sheets which act as electrical interconnects. The Au nanoparticles have been proposed to function as ball rollers in-between GO nanosheets to improve their sliding on each other and to improve contacts with neighboring GO nanosheets, especially on straining the nanocomposites. The NBR-GOAu nanocomposites have exhibited piezoelectric gauge factor (GFε´) of ~0.5, and piezo-resistive gauge factor (GFR) of ~0.9 which clearly indicated that GOAu reinforced NBR nanocomposites are potentially useful in fabrication of structural, high temperature responsive, and stretchable strain-sensitive sensors.

The microstructure, flexural properties, electrical conductivity, thermal conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of epoxy composites filled with multi-walled carbon nanotubes (CNTs), exfoliated graphite nanoplatelets (xGnPs) and CNT-xGnP hybrid filler were investigated. The EMI SE of the CNT-xGnP hybrid composite was higher than 25 dB at 100 MHz while that of the xGnP based composite was almost zero. The flexural modulus of the CNT-xGnP based epoxy composite continuously increased to 3.32 GPa with combined filler content up to 10 wt% while that of the CNT based epoxy composites slightly decreased to 1.96 GPa at 4 wt% CNT, and dropped to 1.57 GPa at 5 wt% loading, which is lower than that of epoxy. The CNT and CNT-xGnP samples had the same EMI SE at the same surface resistivity, because samples with the same surface conductivity have the same amount of the charge carriers.

식품 포장, 전자 기기 등에 활용되고 있는 고분자 기반 기체 차단성 필름은 경량성, 낮은 제조 원가, 높은 가공성 으로 인하여 많은 주목을 받고 있다. 특히 전자기기에 활용되기 위하여, 기체 차단 필름은 매우 높은 수준의 기체 차단성을 요구받고 있다. 하지만 현재 수준의 고분자 기반 기체 차단 필름은 다른 소재와 비교하여 상대적으로 높은 수준의 기체 투과 유량을 보이고 있다. 따라서 기존의 고분자 필름이 가지고 있는 장점을 유지하면서 더 높은 수준의 기체 차단성을 부여하기 위한 요구가 증대되고 있다. 최근 그래핀 소재는 기체 차단을 위한 2차원 소재로서 각광받고 있다. 그러나 그래핀 소재의 낮 은 가공성과 어려운 대면적화 문제 때문에 산화그래핀이 그 대안으로서 떠오르고 있다. 산화그래핀은 높은 종횡비를 가지는 2차원 층상구조의 그래핀에 산소관능기를 함유한 형태로서, 수용성 혹은 극성 용매에 잘 분산되는 성질을 가지며, 따라서 대 량 생산에 용이한 특성을 가지고 있다. 본 연구에서는, 산화그래핀이 함유된 폴리이미드 나노복합막을 제조하였다. 폴리이미 드는 현재 널리 이용되고 있는 기체 차단성 고분자 중의 하나로서 높은 기계적 강도, 열적 안정성 및 내화학성을 가지고 있 다. 본 연구를 통하여 산화그래핀이 함유된 폴리이미드 나노복합막이 기체 차단성을 가지고 있음을 확인하였다. 더 나아가, Triton X-100이나 sodium deoxycholate (SDC) 등의 계면활성제를 나노복합막에 도입함으로써 산화그래핀의 고분자 매트릭스 내에서의 분산성을 향상시켜 기체 차단성을 높이고자 하였다. 그 결과로서, Triton X-100이 도입된 나노복합막이 예상치와 유 사한, 향상된 기체 차단성을 보임을 확인하였다. 본 연구를 기반으로 고분자 기반 나노복합막의 기체 차단성 분야로의 활용성 이 증대될 것으로 기대한다.

In this study, a multiscale method for solving a thermoelasticity problem for interphase in the polymeric nanocomposites is developed. Molecular dynamics simulation and finite element analysis were numerically combined to describe the geometrical boundaries and the local mechanical response of the interfacial region where the polymer networks were highly interacted with the nanoparticle surface. Also, the micrmechanical thermoelasticity equations were applied to the obtained equivalent continuum unit to compute the growth of interphase thickness according to the size of nanoparticles, as well as the thermal phase transition behavior at a wide range of temperatures. Accordingly, the equivalent continuum model obtained from the multiscale analysis provides a meaningful description of the thermoelastic behavior of interphase as well as its nanoparticle size effect on thermoelasticity at both below and above the glass transition temperature.

Time-temperature indicators or integrators (TTIs) indicate food quality changes based on time-temperature history. Whilst many types of TTIs have been developed and commercialized, educated consumers often refuse to purchase food products with attached TTI labels showing even a slight color change. In this study, a novel on-off diffusion-based TTI coupled with polydiacetylene/silica nanocomposites has been proposed. The prototype TTI tag has a multilayer structure comprised of a self-adhesive base layer, a middle microporous sheet, and an upper opaque white layer coupled with a square reservoir of Tween 20 attached to an activation stripe. At the end of the diffusion path, polydiacetylene/silica nanocomposites were injected into a loading site as a fine blue stripe. After activation, Tween 20 diffused and reached the loading site, where it rapidly changed from blue-to-red via solvatochromism. This alternative and innovative TTI continuously showed a blue color until reaching the end point, at which stage a red color rapidly appeared, indicating product rejection. Thus, this novel TTI it is of great benefit to the brand owner. The developed prototype was characterized and evaluated for its ability to monitor microbial quality based on published, isothermal, microbial growth data of modified-atmosphere packaged minced beef, Mediterranean fish, and ground pork. The diffusion of Tween 20 in the TTI system was measured under various isothermal conditions and a kinetic model, based on the association between diffusion and time-temperature, was investigated. The Gaussian-estimated activation energy value was 51.082kJ mol-1. Tween 20 diffusion of 6.10, 5.15 and 6.15mm along the TTI systems were considered to be end points and the 95% confidence interval between the times taken for TTI to display OFF and for the foods to reach their deterioration thresholds were 23.30-23.70, 23.00-23.50 and 23.44-24.05h for total aerobic bacteria, Shewanella putrefaciens, and Pseudomonas spp. respectively. The TTI performance test for reproducibility and accuracy revealed a normal frequency distribution with 35004.90, 1200.254.82 and 549.811.09min at 0, 11 and 25C, respectively in accordance with the investigation of diffusion in the TTI.

In this study, bulk nickel-carbon nanotube (CNT) nanocomposites are synthesized by a novel method which includes a combination of ultrasonication, electrical explosion of wire in liquid and spark plasma sintering. The mechanical characteristics of the bulk Ni-CNT composites synthesized with CNT contents of 0.7, 1, 3 and 5 wt.% are investigated. X-ray diffraction, optical microscopy and field emission scanning electron microscopy techniques are used to observe the different phases, morphologies and structures of the composite powders as well as the sintered samples. The obtained results reveal that the as-synthesized composite exhibits substantial enhancement in the microhardness and values more than 140 HV are observed. However an empirical reinforcement limit of 3 wt.% is determined for the CNT content, beyond which, there is no significant improvement in the mechanical properties.

본 총설에서는 고분자와 은염으로 구성된 고분자 전해질 분리막과 장시간 안정성을 해결하기 위한 방안들이 정리 되었다. 특히 이온성 액체를 활용하여 AgNO3를 새로운 운반체로 사용하기 위한 방안, 새로운 고분자 매트릭스로서 poly(ethylene phthalate) (PEP)를 활용하는 방안과 가장 최근 알루미늄 염을 활용하여 운반체의 안정성을 부여하는 연구결과들이 정 리되었다. 올레핀 촉진수송을 위한 고분자 나노복합체 분리막의 경우, 운반체인 은 나노입자 표면을 극성화시킬 수 있는 전자 수용체의 종류와 특징들이 소개되었으며, 최근 투과도 성능을 향상시킬 수 있는 연구결과들이 정리되었다.

Recently, with continuous developments in the field of materials science, graphene oxide (GO) has emerged as a promising material with excellent electrical, thermal, mechanical, and optical properties, which play important roles in most fields. Researchers have achieved considerable progress with graphene. Chitosan (CS) is a natural polymer that has been studied intensively owing to its specific formation, high chemical resistance, and excellent physical properties. These outstanding properties have led to its universal use in applications such as textile fabrics, tissue engineering, medicine and health, coatings, and paints. By combining the advantages of GO and CS, different types of promising materials can be obtained. This review discusses the preparation of GO-CS fibers, hydrogel and aerogel, and the applications of GO-CS nanocomposites. In addition, directions for future research on graphene material composites are discussed.

To improve photocatalytic efficiency, graphene/Ag/TiO2 nanotube catalyst was synthesized, and its surface characteristics and photocatalytic activity investigated. For deposition of Ag nanoparticles on the TiO2 nanotubes, a polymer compound containing CH3COOAg/poly(Llactide) was utilized, and the silver particles were precipitated by reducing the silver ions during the annealing process. Graphene deposition on the Ag/TiO2 nanotubes was achieved using an electrophoretic deposition process. Based on the dye degradation results, it was determined that the photocatalytic efficiency was significantly affected by deposition of silver particles and graphene on the TiO2 catalyst. Highly efficient destruction of the dye was obtained with the new graphene/Ag/TiO2 nanotube photocatalyst. This may be attributed to a synergistic effect of the graphene and Ag nanoparticles on the TiO2 nanotubes.

We report a covalent functionalization of graphene nanoparticles (GnPs) employing 2,3,4-Tri-O-acetyl-β-D-xylopyranosyl azide followed by fabrication of an epoxy/functionalized graphene nanocomposite and an evaluation of its thermo-mechanical performance. Successful functionalization of GnP was confirmed via thermal and spectroscopic study. Raman spectroscopy indicated that the functionalization was on the edge of the graphene sheets; the basal plane was not perturbed as a result of the functionalization. The epoxy/functionalized GnP composite system exhibited an increase in flexural modulus (~18%) and glass transition temperature (~10°C) compared to an un-functionalized GnP based epoxy composite.

Multi-walled carbon nanotube (MWCNT)/polycarbonate (PC) nanocomposite was prepared by direct melt mixing to investigate the effect of the shear rate on the surface resistivity of the nanocomposites. In this study, an experiment was carried out to observe the shear induced orientation of the MWCNT in the polymer matrix using a very simple melt flow indexer with various loads. The compression-molded, should be eliminated. MWCNT/PC nanocomposite sample exhibited lower percolation thresholds (at 0.8 vol%) and higher electrical conductivity values than those of samples extruded by capillary and injection molding. Shear induced orientation of MWCNT was observed via scanning electron microscopy, in the direction of flow in a PC matrix during the extrusion process. The surface resistivity rose with increasing shear rate, because of the breakdown of the network junctions between MWCNTs. For real applications such as injection molding and the extrusion process, the amount of the MWCNT in the composite should be carefully selected to adjust the electrical conductivity.

An attempt was made to investigate the effect of the preparation temperature on the electro-capacitive performance of polypyrrole (PPY)/graphene oxide (GO) nanocomposites (PNCs). For this purpose, a series of PNCs were prepared at various temperatures by the cetyltrimeth-ylammonium bromide-assisted dilute-solution polymerization of pyrrole in presence of GO (wt%) ranging from 1.0 to 4.0 with ferric chloride as an oxidant. The formation of the PNCs was ascertained through Fourier-transform infrared spectrometry, X-ray diffraction spectra, scanning electron microscopy and simultaneous thermogravimetric-differential scanning calorimetry. The electrocapacitive performance of the electrodes derived from sulphonated polysulphone-bound PNCs was evaluated through cyclic voltammetry with reference to Ag/AgCl at a scan rate (V/s) ranging from 0.2 and 0.001 in potassium hydroxide (1.0 M). The incorporation of GO into the PPY matrix at a reduced temperature has a pronounced effect on the electrocapacitive performance of PNCs. Under identical scan rates (0.001 V/s), PNCs prepared at 10 ± 1°C render improved specificconductivity (526.33 F/g) and power density (731.19 W/Kg) values compared to those prepared at 30 ± 1°C (217.69 F/g, 279.43 W/Kg). PNCs prepared at 10 ± 1°C rendered a capacitive retention rate of ~96% during the first500 cycles. This indicates the excellent cyclic stability of the PNCs prepared at reduced tempera-tures for supercapacitor applications.

최근 자원과 에너지를 절약하고 효과적으로 사용하여 환경 훼손을 줄이고 청정에너지를 이용할 수 있는 기술의 연구가 활발하게 진행되고 있다. 이와 관련 하여, 친환경적이고 경제적이며 독성이 거의 없는 초임계 유체가 물질의 합성과 프로세스에 많이 응용되고 있다. 이산화탄소는 낮은 임계온도와 압력, 가격 경쟁력 그리고 무독성 등의 장점을 가짐으로써 초임계 공정에 많이 사용되고 있는 용매 중에 하나이다. 그러나 분자량이 높은 고분자들에게는 낮은 용해력이 단점으로 있어서 사용에 제한적이다. 따라서, 분자량이 높은 고분자를 용해하기 위해선 하이드로카본 계열의 용매를 사용하여야 한다. 본 연구에서는, 초임계 유체를 이용하여 Poly (methyl methacrylate)/클레이 나노 복합체 제조에 관한 연구를 진행 하였다. 또한, 초임계 유체 내에서 분산성을 극대화 할 수 있도록 Na+-MMT 클레이 표면을 플로린 계열의 surfactant로 개질 시키어 복합체 제조에 응용 하였다. 개질된 클레이를 이용하여 제조 된 복합체는 neat Poly (methyl methacrylate)보다 향상된 기계적, 열적 특성을 보였으며, 제조 된 복합체는 X-ray 회절 방법, 열적 안정성 그리고 TEM 으로 나노 클레이의 분산성을 분석 하였다.

최근 낮은 표면장력, 높은 확산계수, 가스와 같은 낮은 점도, 그리고 액체와 유사한 밀도를 갖는 초임계 유체의 장점을 이용하여 여러 가지 물질의 합성이나 응용 공정에 초임계 유체를 이용하고 있다. 초임계 유체를 이용하여 복합체 제조 시 기존의 용융공정에 비해서 분자들의 움직임이 활발하게 이루어 질 수 있어서 물성의 향상을 기대할 수 있다. 또한 클레이가 고농도로 함유된 마스터 배치를 쉽게 제조할 수 있으며, 기존의 유기 용매를 사용하여 복합체를 제조할 때보다 잔존 용매를 쉽게 제거할 수 있다는 장점을 가지고 있다. 따라서 본 연구에서는 이러한 초임계 이산화탄소를 이용하여 폴리에틸렌옥사이드/클레이 나노복합체를 제조하였다. 또한 본 연구의 목적은 초임계 상태에서 분자들의 활발한 움직임을 기대할 수 있으므로 고분자가 용해되고 클레이 층상으로 효과적으로 삽입되어 복합체의 열적 특성 및 다른 여러 가지 물성을 증가시키는 데 있다. 복합체 제조 후 XRD, TGA, 그리고 DSC를 이용하여 복합체의 특성을 분석 했다. 그 결과 용융방법으로 제조한 복합체보다 열 안정성이 향상되었으며, 클레이 층상 거리도 더 많이 벌어짐을 확인할 수 있었다.

In this work, nanocomposites of epoxy resin and chemically reduced graphene oxide (RGO) were prepared by thermal curing process. X-ray diffractions confirmed the microstructural properties of RGO. Differential scanning calorimetry was used to evaluate the curing behaviors of RGO/epoxy nanocomposites with different RGO loading amounts. We investigated the effect of RGO loading amounts on the mechanical properties of the epoxy nanocomposites. It was found that the presence of RGO improved both flexural strength and modulus of the epoxy nanocomposites till the RGO loading reached 0.4 wt%, and then decreased. The optimum loading achieved about 24.5 and 25.7% improvements, respectively, compared to the neat-epoxy composites. The observed mechanical reinforcement might be an enhancement of mechanical interlocking between the epoxy matrix and RGO due to the unique planar structures.