Diffusion Coefficient Of Water Research Articles

Esterification of Lignin Isolated by Deep Eutectic Solvent Using Fatty Acid Chloride, and Its Composite Film with Poly(lactic acid).

In this study, the effect of lignin esterification with fatty acid chloride on the properties of lignin and lignin/poly(lactic acid) (PLA) composites was investigated. Lignocellulose (Pinus densiflora S. et Z.) was treated using a deep eutectic solvent (DES) with choline chloride (ChCl)/lactic acid (LA). From the DES-soluble fraction, DES-lignin (DL) was isolated by a regeneration process. Lignin esterification was conducted with palmitoyl chloride (PC). As the PC loading increased for DL esterification, the Mw of esterified DL (EDL) was increased, and the glass transition temperature (Tg) was decreased. In DL or EDL/PLA composite films, it was observed that EDL/PLA had cleaner and smoother morphological characteristics than DL/PLA. The addition of DL or EDL in a PLA matrix resulted in a deterioration of tensile properties as compared with neat PLA. The EDL/PLA composite film had a higher tensile strength and elastic modulus than the DL/PLA composite film. DL esterification decreased water absorption with lower water diffusion coefficients. The effect of lignin esterification on improving the compatibility of lignin and PLA was demonstrated. These results are expected to contribute to the development of high-strength lignin composites.

Performance analysis of desiccant cooling system using polyacrylic acid sodium salt desiccant wheel

The adsorbent material has an important role in the improvement of desiccant cooling system performance. Super Desiccant Polymer (SDP) is chosen in this work as a sophisticated desiccant material characterized by excellent adsorption capacity and durability. The mathematical correlations of adsorption isotherm on SDP surface, adsorption heat and water diffusivity coefficient are used to model the SDP desiccant wheel by means of Comsol software. Modeling results are validated by an experimental data base. They serve as a base for the determination of the SDP wheel effectivenesses ԑ1 and ԑ1 which are equal to 0.02 and 0.83, respectively. The application of desiccant cooling system performance with SDP desiccant wheel in a hot and dry weather of the region of Gabes (south-eastern Tunisia) leads to a coefficient performance (COP) value equal to 1.1. This result is better than the COPs of other air conditioning desiccant systems which use zeolites and silica gel wheels. Moreover, the COP of desiccant cooling system with SDP desiccant wheel is the best for a wide range of operating conditions.

Modeling of mass transfer processes during dehydration of air-dried fish

The study addresses the problems of the Fisheries industry development in the Murmansk region. It has been acknowledged that the percentage of the frozen fish in the output of hydrobionts food products is about 90 %. The focus areas for the Russian Fisheries industry are the increasing share of products with high added value and the development of the domestic consumer market of fishery products. It has been found that the air-dried and dried fish products with defined organoleptic properties is traditionally in strong demand with the population. However, the range of air-dried and dried fish products available for the consumers is rather limited. Moreover, there is a very small part of air-dried and dried fish in the total volume of hydrobionts food products. It is possible to increase the efficiency of air-dried and dried fish production by using the scientific-based process solutions, which allow to reduce the production costs and improve the consumer properties of the finished products. This paper presents the aspects of generalization of the dehydration processes in the production of dried, air-dried and smoked fish. A link between the initial, critical moisture content of fish and the potential conductivity of mass transfer coefficients has been established. A mathematical relation for calculating the duration and modeling the kinetics of drying processes in production of dried and air-dried fish has been determined. The equations for calculating the water diffusion coefficients in the critical points of the kinetics curve have been obtained. The combined use of the received patterns allows to model the dehydration processes when producing the air-dried and dried fish products, calculate the drying time, determine the moisture diffusion coefficients and build dependencies of water distribution in the thickness of the processed object.

Hot-air drying characteristics of Millettia speciosa Champ. slice and establishment of the kinetic model

[Objective] To explore the influence of different hot air temperatures, slice thicknesses and material loads on Millettia speciosa Champ. slice hot air drying rate, establish model of thermal wind drying kinetic, and provide reference for perfecting M. speciosa Champ. drying processing technology. [Method] Taking hot air temperature (50, 60, 70, 80 °C), slice thickness (2,4,6,8 mm) and material load (100,200,300 g) as investigating factors,real-time measurement of moisture changes during hot air drying of M. speciosa Champ. slices under various conditions. The 5 kinds of drying models were screened and fitted, calculated the effective water diffusion coefficient and theactivation energy in the drying process. [Result] With the increase of the hot air temperature, the slice thickness and material load decreased, the moisture content of dry basis was greatly reduced, and the drying rate was greatly increased. The hot-air drying process of M. speciosa Champ. slices was divided into two stages : acceleration and deceleration, and most of the drying process was the deceleration stage. The kinetic model of hot-air drying of M. speciosa Champ. slices conformed to the Page model, and the predicted value of the Page model had a good fit with the experimental value ( R 2=0.969). the fitting equation ln (-lnMR)= -3.174-0.242 H+0.029 T-0.006 L+(0.721+0.015 H+0.002 T)ln t, k=e -3.174-0.242 H+0.029 T-0.006 L , n=0.721+0.015 H+0.002 T, the effective diffusion coefficient D eff of M. speciosa Champ. under different drying conditions was 1.62114×10 -10-12.96913×10 -10 m 2/s, with the increase of hot air temperature and slice thickness, the material load decreased, and the overall trend was increasing, and the activation energy was 60.7388 kJ/mol. [Conclusion] The Page model can better reflect the moisture change law of hot air drying process of M. speciosa Champ. slice with different slice thicknesses, and by fitting the equation, the content of water ratio in the hot air drying process at a certain time can be accurately predicted. 摘要：【目的】探讨不同热风温度、切片厚度及装载量对牛大力切片热风干燥速率的影响, 并建立牛大力切片热风 干燥动力学模型, 为牛大力干燥工艺探索提供理论依据。 【方法】以热风温度 (50、60、70、80 °C)、切片厚度 (2、4、6、8 mm)和装载量 (100、200、300 g)为考察因素, 实时测定各条件下牛大力切片热风干燥过程中水分变化, 对常见的5种 干燥模型进行筛选, 并计算干燥过程中的有效水分扩散系数和活化能。 【结果】随着热风温度的升高, 切片厚度和装载 量的降低, 牛大力切片的干基含水量明显减少, 干燥速率明显增加。牛大力切片在热风干燥过程分为加速和降速2个 阶段, 其中大部分干燥过程为降速阶段。牛大力切片热风干燥动力学模型符合Page模型, 该模型预测值与试验值拟 合度较高( R 2=0.969), 拟合方程为ln(-lnMR)=-3.174-0.242 H+0.029 T-0.006 L+(0.721+0.015 H+0.002 T)ln t, 可求得K=e -3.174-0.242 H+0.029 T-0.006 L , n=0.721+0.015 H+0.002 T, 不同干燥条件下牛大力切片的有效水分扩散系数在1.62114×10 -10~12.96913×10 -10 m 2/s, 均随着热风温度的升高和切片厚度的增加, 总体呈上升趋势; 活化能为60.7388 kJ/mol。 【结论】Page模型可 较好地描述不同切片厚度的牛大力切片热风干燥过程中水分的变化规律, 且通过拟合方程能较准确预测热风干燥过 程中某时刻牛大力切片的水分比。

Protein hydration shell formation: Dynamics of water in biological systems exhibiting nanoscopic cavities

This work explores the singular scenarios emerging from nanoscopic cavities, located in aqueous solutions, that include biomolecules and, as a consequence, the process of biomolecule hydration shell formation. The research presents a nano-scale study, performed in various systems related with protein-water solutions, using all-atoms molecular dynamics simulations. This research shows that if a protein falls within an empty nanoscopic cavity located in an aqueous solution, it will take a time, with a magnitude significant for biological processes, to rebuild its whole network of hydrogen bonds with the solvent molecules. During that protein isolation time the dynamics of the biomolecule, and therefore the corresponding bioactivity, will be seriously compromised. In the case of the protein barstar (radius of gyration of 1.17 nm) located in the centre of cavities with radius r from 2.5 to 4.5 nm, and solvent diffusion coefficients for bulk and physiologic water (2.4 and 1.5 μm2/ms, respectively), that time is found to be of the order of tens-hundreds of picoseconds, a significant temporal range concerning the dynamics and bioactivity of proteins. On the other hand, the dynamics of formation of the inner protein hydration shell has been followed using an atomic view. The required time has been found to decrease with r, as the network of water molecules approaching the biomolecule resembles that of the biological water corresponding to that biomolecule. That resemblance increases as those water molecules have previously been in close contact with the protein. The dynamics of those systems has been modelled using a two states model. Isolated bulk water is taken as reference for the computer simulations. Comparison with experimental data is also provided.

Simulation of the Parameters Effecting the Water Quality Evolution of Xuanwu Lake, China.

After years of water environment improvement, China’s water quality has improved to some extent in recent years. However, different water areas have different characteristics of water pollution. The paper used mathematical models to investigate the influence of different parameters on the water quality of Xuanwu Lake, China. The predominant focus was on the nutrients concentration due to changing the amount of pollutants, degradation coefficient, water diversion discharge and diffusion coefficient. The results showed that the amount of pollutants had the most significant impact, followed by the degradation coefficient. The total phosphorus and total nitrogen concentrations of Xuanwu Lake increased with the increase of the amount of pollutants. The water quality of Xuanwu Lake decreased significantly with the increase of degradation coefficient. Increasing the water diversion discharge will not only make a big difference in water quality, but it will also worsen the water quality. The effect of the amount of pollutants on Xuanwu Lake total phosphorus and total nitrogen is 4.1 and 5.7 times that of water diversion discharge. The influence of total phosphorus and total nitrogen in the degradation coefficient scheme is 3.5 and 6.2 times that of the water diversion discharge scheme. The diffusion coefficient has almost no effect on the water quality of Xuanwu Lake. From the practical difficulty and implementation effect of water environment improvement, the order of water quality improvement effect from good to bad is as follows: the amount of pollutants scheme, degradation coefficient scheme, water diversion scheme, diffusion coefficient scheme. Under the circumstance of limited water diversion, the lake will effectively improve the water quality. Reducing the discharge of pollutants is the fundamental measure to control water environment problems, and water diversion is an auxiliary measure to improve the water ecology. It will become a trend to combine the reduction of pollutant discharge and water transfer for water environment improvement. This paper is of significance for improving the water quality of Xuanwu Lake, and it also provides a scientific method for water environment improvement of water diversion projects.

A study on the effect of nano-ZnO on hygroscopic characteristics of PP/Wood flour composites

ABSTRACT Polypropylene/wood flour composites having different nano-ZnO content were fabricated using melt compounding and subsequent injection moulding. The long-term water absorption and thickness swelling of the composites were studied for a range of water immersion times. It was found that the moisture absorption and dimensional stability of the specimens progressively decreased with an increasing nano-ZnO loading. The lowest water diffusion coefficient and swelling rate parameter were observed in the specimens produced with 4 phc nano-ZnO. The mechanism of water transport processes the specimens was proved to follow the kinetics of Fickian diffusion theory. Morphological findings revealed that the void content in the composite decreased by adding nano-ZnO. The hydrophobicity of the specimens reinforced with nano-ZnO improved by creating a tortuous path as a result of its characteristic barrier property. In comparison with the contact angle of untreated samples (71°), adding 4 phc of nano-ZnO increased the contact angle by 34% (95°).

Resistance of Polylactide Materials to Water Mediums of the Various Natures

The influence of talc filler, its content, as well as an additional heat treatment and temperature on the regularities of polylactide materials water-absorption has been researched. Based on the obtained data, the water diffusion coefficient in polylactide materials and the activation energy of the diffusion process were determined. It was found that the process of water absorption by the filled and heat-treated materials based on polylactide proceeds slower and requires more activation energy of the process. Stability of the developed polylactide materials to acidic and alkaline media has been determined, in particular, it was found that the destruction of polylactide samples occurs faster in an alkaline medium than in an acidic one

778 Poor Sleep Quality is Associated with Reduced Myelination in Patients with Psychotic Disorders

Abstract Introduction Recent studies show that sleep favors oligodendrocyte proliferation and myelination, and sleep loss is associated with alterations in white matter structure and decreased myelination. Psychotic disorders are characterized by disrupted white matter integrity, and abnormal axon and myelin structure. Despite common sleep disturbances in these disorders, little is known about the relationship between sleep quality and white matter findings. A novel in vivo neuroimaging technique that combines diffusion tensor spectroscopy (DTS) and magnetization transfer ratio (MTR) allows separately examining the axon structure and glial function, and myelin content, respectively. Using this method, we examined the association of sleep quality with white matter biology in a sample of patients with psychotic disorders and matched healthy controls. Methods Participants included patients diagnosed with bipolar disorder with psychotic features (euthymic or depressed, n=12) and schizophrenia spectrum disorders (n=9), and age and sex matched healthy controls (n=20). DTS and MTR data was collected from the right prefrontal white matter at 4T. DTS measures included apparent diffusion coefficients of water, NAA, creatine and choline. Sleep quality was measured using Pittsburgh Sleep Quality Index (PSQI). Results PSQI total score was significantly higher in patients. and patient sample included a higher percentage of poor sleepers (PSQI total score>5). In patients, total PSQI score and sleep onset latency were significantly and negatively associated with MTR (F=6.9, p=0.02 and F=9.7, p=0.007, respectively). There was no difference in any DTS measures between groups. Conclusion Our preliminary results show that poor sleep quality is associated with decreased myelin content in the frontal lobe, in patients with psychotic disorders. This finding suggests that sleep loss may be a mediator of white matter alterations in psychosis. Support (if any) This work is supported by National Institute of Mental Health K23MH119322 to Cagri Yuksel

Role of interlayer porosity and particle organization in the diffusion of water in swelling clays

This study focuses on the role played by the interparticle and interlayer porosities, and the preferred orientation of the particles on water diffusion in dual-porosity clayey media (i.e., swelling clay minerals). For this purpose, we use Na-vermiculite, a swelling clay that does not exhibit osmotic swelling and therefore allows a clear discrimination between the interparticle and interlayer porosities. Two samples were prepared with an equal proportion of interparticle and interlayer porosities (i.e., 0.25 each) but different degree of preferred particle orientation (i.e., isotropic vs anisotropic). Through-diffusion and pulsed gradient spin echo attenuation measurements by nuclear magnetic resonance of protons techniques were used to probe water mobility, while the orientation of the particles was quantified by X-ray scattering analysis. Experimental water diffusion results obtained with these two Na-vermiculite samples were compared to those with samples made of Na-kaolinite particles (non-swelling clay mineral) having only interparticle porosities equal to 0.25 and 0.5, corresponding respectively to the interparticle and the total porosity of the Na-vermiculite samples. In addition, these experimental results were compared to simulated data using Brownian dynamics with virtual porous media representative of the real samples. For the range of porosities investigated, a good agreement was observed between measured and simulated water mobilities. The obtained results confirmed the important role played by the preferential orientation of the particles on water dynamics in clayey media, through an important reduction of overall water mobility between the isotropic and anisotropic Na-vermiculite samples. These results also showed that for the same total porosity, the presence of interlayer porosity and associated nano-confinement led to a logical reduction in the pore diffusion coefficient of water in Na-vermiculite in comparison to Na-kaolinite. Moreover, in comparison with Na-kaolinite having the same interparticle porosity, results showed that the contribution of the interlayer volume on the traversing flux was small compared to the interparticle volume. Finally, the computed results revealed that the anisotropy in water diffusion can be directly predicted based on the degree of particles preferred orientation, irrespective of the total or the distribution of the different porosity types.

Accelerated aging behavior and life prediction of low-temperature vulcanizable CR–BIIR blend based encapsulant material for undersea sensors

Blends of chloroprene rubber (CR) and bromobutyl rubber (BIIR) with low-temperature vulcanization (LTV) technology were found suitable for the encapsulation of temperature-sensitive undersea sensors. Polymeric blends are susceptible to the aging process due to external environments such as heat, oxygen, ozone, light, and mechanical stresses, etc. Hence, the longevity of these blends for hostile seawater applications is a great concern. The marine aging of rubber blends was not investigated much. In this study, the LTV blends with a curing system based on lead and zinc oxides were subjected to accelerated aging in a 3.5% aqueous solution of NaCl from 40°C to 70°C. The retention of tensile strength, % elongation and modulus properties were estimated. It was observed that aging could lead to an initial increase in the modulus and a considerable decrease in ultimate tensile strength and elongation values with an increase in the aging period. Reduction in elongation at break showed a gradual decrease with an increase in both temperature and exposure time. It was observed that the blends with lead oxide cure system were prone to more degradation than ZnO-based blend. A life of 6.5 years and 5.3 years at 25°C for blends based on ZnO and lead oxide cure systems was estimated. The water diffusion coefficient was found to be of the order of 10−12 mm2 s−1 for both blends.

Accurate Prediction of Organic Aerosol Evaporation Using Kinetic Multilayer Modeling and the Stokes-Einstein Equation.

Organic aerosol can adopt a wide range of viscosities, from liquid to glass, depending on the local humidity. In highly viscous droplets, the evaporation rates of organic components are suppressed to varying degrees, yet water evaporation remains fast. Here, we examine the coevaporation of semivolatile organic compounds (SVOCs), along with their solvating water, from aerosol particles levitated in a humidity-controlled environment. To better replicate the composition of secondary aerosol, nonvolatile organics were also present, creating a three-component diffusion problem. Kinetic modeling reproduced the evaporation accurately when the SVOCs were assumed to obey the Stokes-Einstein relation, and water was not. Crucially, our methodology uses previously collected data to constrain the time-dependent viscosity, as well as water diffusion coefficients, allowing it to be predictive rather than postdictive. Throughout the study, evaporation rates were found to decrease as SVOCs deplete from the particle, suggesting path function type behavior.

Influence of Nanofiller Lignite Fly Ash on Tribo-Mechanical Performance of Sansevieria Roxburghiana Fiber Reinforced Epoxy Composites

ABSTRACT The present study aims to explore the modification of nanofiller lignite fly ash (LFA) on mechanical, wear, friction, and moisture intake behavior of Sansevieria Roxburghiana fiber (SRF)-reinforced epoxy composites. The matrix epoxy was modified with a filler LFA of size 20 nm with different weight proportions of 0, 0.5, 1, 1.5, 2, and 2.5. The composite samples with different compositions were manufactured with a hand layup method followed by a compression molding technique. The prepared samples were investigated for tensile, flexural, impact, wear, and friction properties as per ASTM standards. The optimal results on tensile, impact, flexural, wear, and friction properties were obtained with the addition of 2 wt. % filler LFA. The percentage increase in the mechanical properties was perceived as 38.33% for tensile, 41.34% for flexural, and 33.56% for impact strength respectively. Minimum moisture intake is observed for the composite samples with nanofiller LFA, the water diffusion coefficient was reduced by 55% with the incorporation of nanoparticles LFA. The rupture surface of tensile-tested specimens was inspected using a scanning electron microscope. The SRF epoxy composites possess excellent tribological and mechanical features that can be exploited as low-cost construction materials.

Influence of Gamma Irradiation and Water Aging on the Space Charge Characteristics of Epoxy Micro-Nano Composites.

Epoxy micro-nano composites are well-known to exhibit enhanced electrical, mechanical as well as thermal properties compared to base epoxy resin. Yet, a clear understanding need to be achieved on the long-term aging performance of the epoxy micro-nano composites. The present review article is a comprehensive study on the impact of gamma irradiation and water aging on the space charge characteristics of epoxy micro-nano composites that are applicable as insulant in high-voltage power apparatus. Ion-trapping nanoparticles, which possess good oxidation resistance and high ion trapping ability, are being chosen as nanofillers along with silica micro fillers in epoxy micro-nano composite material for improving the reliability of electrical insulation structures. The epoxy micro-nano composite specimens were subjected to gamma irradiation (4 kGy and 8 kGy) and water aging (under room temperature and at 90 °C), to analyze the effect of aging on space charge accumulation and charge decay characteristics. The mean magnitude of accumulated space charge density of epoxy micro-nano composites tends to increase with an increase in gamma irradiation dose as well as an increment in water diffusion coefficient. The mean lifetime of the space charge decay during depoling has significantly reduced after gamma irradiation and is converse with water aged specimen. Voltage polarity reversal studies have indicated that a part of homo-charge injected from electrodes remained as hetero-charge just after polarity reversal and could result in the distortion of electric field thereby increasing the electric field enhancement factor.

Permeability Coefficient of Unsaturated Loess and Its Gaseous and Liquid Water Migration Modeling

Water migration changes the water distribution of loess and significantly affects the engineering properties of loess. However, because of the characteristics of loess such as water sensitivity and special structure, it is still difficult to understand the water migration trend of loess. The objectives of this study are to investigate the water diffusion coefficient and soil-water characteristic curve (SWCC) of loess, focusing on the effect of temperature and density, and establish a mixed migration equation for gaseous and liquid water to develop a new calculation method of loess water migration. The results show that the density of loess with larger liquid water content has a more significant effect on the diffusion coefficient than that of less liquid water content. Furthermore, the density significantly affects the matric suction of unsaturated loess, while the temperature change at normal temperature has slight effect. Based on the data obtained in this study, the soil water permeability coefficient was obtained. Moreover, considering the characteristics of mixed migration of gas and liquid water in unsaturated loess, an equation was derived for the gas-liquid water transfer in unsaturated loess. The calculation results are consistent with the experimental results of water migration experiment. Based on the calculation results of water migration, the trend of water migration and proportion of gaseous water during migration were analyzed.

Mechanical and water absorption properties of nano TiO2 coated flax fibre epoxy composites

The present study aims at evaluating the mechanical properties such as tensile, flexural and interlaminar shear strength of unmodified and nano TiO2 coated flax fibre composites. Nano TiO2 coating on the flax fibres is done by immersing the fibres in a solution containing ethanol and silane coupling agent in volume ratio 10:1 and further adding nano TiO2. Effect of fibre coating on the composites is also evaluated by conducting water absorption tests. The composites are prepared using the compression molding technique. Results indicate an improvement in the tensile, flexural and interlaminar shear strength values by 22%, 24% and 16% respectively. Water diffusion coefficient of fibre modified composites reduced by 42% for 0.6 wt% TiO2 coated samples. Nanoparticle grafting on the fibre surface by silane treatment enhanced the compatibility between the hydrophilic fibre and hydrophobic polymer matrix. Chemical and mechanical bonding is developed between the fibre and matrix on account to the fibre surface grafting with nano TiO2 and silane coupling agent. Mechanical properties and water absorption resistance are thus improved. Nanoparticle coating on the fibre surface is validated from the scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis.

Estimation of the effective water diffusion coefficient in Nafion® membrane by water balance measurements

AbstractParameters estimation is important in fuel cell modelling and it remains a challenging task to predict. One of the most discussed parameters is the water diffusion coefficient in Nafion® membrane, which has a huge variation (10−9 and 10−5 cm2 s−1), based upon the viewpoints of different authors. In this article, the estimation of the effective water diffusion coefficient through water balance method is presented and the effects of relative humidity gradient and cell temperature are explained. The membrane used in this work is Nafion® NRE 211 tested at a temperature of 60°C and 70°C with air flows. The value of water flux passing through the membrane is used to calculate the effective diffusion coefficient. A value in the range of 1 × 10−7 to 4 × 10−7 cm2 s−1 is reported and it shows that the water balance method can be applied easily to measure an effective membrane water diffusion coefficient.

Classification of Aged Epoxy Micro–Nanocomposites Through PCA- and ANN-Adopted LIBS Analysis

Epoxy micro–nanocomposite specimens are subjected to different levels of gamma irradiation and water aging to analyze their degradation behavior after aging. The plasma temperature calculated from the laser-induced breakdown spectroscopy (LIBS) spectral data tends to decrease, and the crater depth after laser ablation tends to increase with increment in the level of aging, reflecting the reduction in surface hardness of the epoxy specimens after aging. Water aging creates a more severe impact on the surface hardness of the specimens, compared to gamma irradiation, in the range studied. The normalized intensity ratio of H(I)/Si(II) is in direct correlation with the water diffusion coefficient. Machine learning techniques, such as the principal component analysis (PCA) and the artificial neural network (ANN) analysis, have been performed on LIBS spectral data in order to classify the unaged, gamma-irradiated, and water-aged specimens. The number of neurons in the hidden layer of the neural network architecture has been optimized based on classification accuracy and the number of epochs required to converge. The ANN-adopted LIBS analysis is successful with good classification accuracy compared to PCA, for categorizing the level and type of aging in epoxy micro–nanocomposites as observed in this work.

The Effect of Long Term Hygrothermal Aging by Immersion on Carbon/Epoxy Composites Exposed to the Heat Sources for Naval and Marine Applications

Fiber-Reinforced Polymer (FRP) composites have many advantages over conventional materials in terms of high strength-to-weight and stiffness-to-weight ratios, design flexibility and enhanced service life. Due to these advantages, FRP composites are used in many different fields such as Construction, Electric/power generation, Marine, Corrosion/infrastructure, transportation and so on. Most researches of FRP composites were focused on the applications used in ground field. However, in Navy, marine composite materials are increasingly being used in diverse applications: Submarine, Autonomous Underwater vehicle, Unmanned Surface vehicle and Payloads in Naval vessel. It is known that polymer composites are very sensitive and are friendly to water or moisture in any forms. Moisture in polymer composites often causes degradation by swelling and hydrolysis. Especially, if polymer composites will be immersed in water and seawater, faster degradation can be caused by water uptake than any other moisture environments. While general investigations regarding water uptake are concentrated on the composite materials cured in ambient temperature, the immersion effects of polymer composites exposed to elevated temperatures were studied because underwater applications of composite materials can be exposed to the various heat sources. For example, fires on naval vessels and underwater vehicles can be started by any number of causes such as electrical faults and ignition of flammable gases or liquids. Accordingly, immersion effects must be studied on marine composite materials exposed to various temperatures in order to evaluate service life in an underwater environment. This study investigated the water uptake, diffusion coefficient, and Short beam shear (SBS) for Interlaminar Shear Strength(ILSS), delamination between fiber and resin using test specimens exposed to the elevated temperatures. The specimens were immersed for a definite period of time (~one and a half years) in seawater and deionized water (DI water) to compare both degradation mechanisms.

Unraveling the mysteries of the thin film composite reverse osmosis membrane

A recent article in <i>Science</i> by Culp, Kumar, Gomez, and colleagues introduces a new approach to characterizing reverse osmosis thin film composite membranes to provide critical insights into understanding how polymer membrane microstructure affects water permeability. Such approaches offer a degree of microstructure characterization that has up until now been unavailable to the membrane science community. Combined with modeling of water diffusion coefficient in the polymer membrane itself, this effort has begun to answer decades-old questions about how polyamide reverse osmosis membranes function.