Moisture Swelling Research Articles

Convolutional Neural Network for Segmenting Micro-X-ray Computed Tomography Images of Wood Cellular Structures

To further enhance the performance of wood products, improved tools are needed to study in situ cellular scale phenomena like mechanical deformations and moisture swelling. Micro-X-ray computed tomography (μXCT) using brilliant synchrotron light sources now has the spatial and temporal resolution for real-time visualization of phenomena in three-dimensional cellular structures. However, the tradeoff for speed includes the loss of intensity contrast between different types of materials within the imaged structure, such as cell wall and air in wood. This loss of contrast prevents traditional histogram-based segmentation methods from being used effectively. A new convolutional neural network (CNN) approach was therefore developed to segment fast μXCT images of wood into cell wall and air volumes. The fast μXCT and segmentation were demonstrated in the study of moisture swelling in loblolly pine (Pinus taeda) earlywood and latewood cellular structures conditioned at 0%, 33%, 75%, and 95% relative humidity (RH). The CNN segmentation results had a mean intersection over union (IoU) metric accuracy of 96%. Initial analysis of the swelling in the latewood revealed cell walls swelled about 25% when conditioned from 0% to 95% RH. Additionally, the widths of ray cell lumina in the transverse plane of latewood could be observed to increase at higher RH. The segmentation method presented here will facilitate future quantitative analyses in in situ μXCT studies of wood and other similar cellular materials.

Study on the Effect of Acrylic Acid Emulsion on the Properties of Poplar Wood Modified by Sodium Silicate Impregnation

Inorganic silicate impregnation-modified fast-growing wood shows improved mechanical properties and thermal stability, but inorganic silicate agent loss and moisture absorption affect its processability. This study proposes a method to improve the impregnating agent loss and modified wood moisture absorption of poplar wood modified by using an acrylic acid emulsion/sodium silicate composite. The acrylic acid emulsion coated the sodium silicate and cell wall surfaces with a cured film that blocked water molecules from entering the modified wood. The acrylic acid emulsion adhered to the wood and sodium silicate, thus reducing impregnating agent loss. The addition of the acrylic acid emulsion maintained the excellent mechanical properties of sodium silicate-modified poplar wood and greatly improved its bending strength. The water absorption and moisture swelling rate were significantly decreased, and the dimensional stability of modified poplar wood was more than 50% higher than that of unmodified poplar wood. The thermogravimetric analysis (TG)results showed that the addition of organic components reduced the heat resistance of modified wood, but the thermal stability was still higher than unmodified wood. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results showed that acrylic esters in acrylic acid emulsion reacted with hydroxyl groups on sodium silicate and wood to form covalent bonds that improved the impregnating agent’s resistance to loss and reduced the moisture absorption of the wood. The modified poplar wood showed better dimensional stability and water resistance.

Moisture sorption and swelling of flax fibre and flax fibre composites

This study evaluates the influence of moisture sorption on the properties of flax fibres and their composites. The radial swelling of both the elementary and technical flax fibres at a wide range of relative humidity (RH) values is determined. Moreover, the effects of moisture sorption on both the thickness swelling and flexural properties of flax/polyester and flax/epoxy composites are evaluated. Park's model is used to define the fibre moisture sorption curve. The model suggests that the moisture is first sorbed on hydrophilic fibre surfaces or microcavities until specific sites within the fibre reach saturation and later, the moisture forms aggregates at high RH. Flax elementary fibres have a lower radial swelling coefficient when compared to technical fibres , with radial swelling coefficients of β r = 1.2 and 1.9, respectively. At the composite level, flax/polyester and flax/epoxy systems have approximately the same thickness swelling coefficients, β t = 0.5 and 0.6, respectively, over the RH range , 11–97%. This behaviour could be explained by the constraining effect of the resins on flax fibres due to higher stiffness of matrix and probably due to resin penetrating the fibre lumen. Flexural properties of longitudinal and transverse fibre-oriented flax/polyester and flax/epoxy composites conditioned at different RH, and tested in fully dry condition, decreased as RH increased beyond 54%, likely due to moisture swelling which induced damage. This study provides new insights into the moisture sorption and dimensional changes of both the elementary and technical flax fibres and their composites and also the effects of moisture on the flexural properties of the composites.

Moisture swelling and shrinkage of pine wood versus susceptibility to robotic assembly of furniture elements

Moisture swelling and shrinkage of pine wood and susceptibility to robotic assembly of furniture elements. Background and Objectives. Processing technology, storage conditions and wood properties affect the actual dimensions of wooden elements. It was decided to experimentally check how the dimensions of samples, made of the selected wood species, will change under the influence of different storage conditions, typical for industrial environments. And especially how these changes will affect the susceptibility to assembly of upholstery frame rails that form a box joint. Materials and Methods. The tests were performed on three series of rails made of Scotch pine wood. Each tested series consisted of 12 elements. First, the five dimensions forming the box joint were measured. Then, each series was exposed to different conditions: in the industrial hall (air of RH = 29-48% and t = 16-24°C), in the compressor room (RH = 24-51%, t = 13-27°C) and outside in a covered shed (RH = 20-50%, t = 3-23°C). After 35 days the dimensions were measured again. Results. It was found that the average moisture content decreased and the dimensional deviations increased in the samples stored in the production hall and in the compressor room. In samples stored outside, the mean moisture content did not change, but the dimensional deviations increased significantly. Discussion. The storage of wooden elements increases the deviations from assigned dimensions. Exposure to repeated changes in moisture content and ambient temperature, even without changing the final moisture content of the elements, results in greater dimensional changes than storage under more stabilized conditions that reduce wood moisture content. Conclusions. The shrinkage and swelling of wood due to changes in its moisture content are not fully reversible, therefore, apart from maintaining the appropriate temperature and air humidity during storage, it is important to keep these conditions unchanged.

Karakteristik chiffon berbahan baku tepung pisang lewat matang

Background: The X’s bakery industry makes banana chiffon using fresh banana fruit as a raw material; however, fresh bananas were prone to rot.
 Research purposes: to apply overripe banana flour in making chiffon and study the characteristic differences with fresh banana chiffon.
 Method: This research consisted of making overripe banana flour using foam mat drying and making banana chiffon. The chiffon cake was made by adding 20g, 40g, and 60g banana flour (150g flour base) and control of 50g fresh ripe bananas. The yield, color, repose angle, and moisture content of overripe banana flour were analyzed, including specific volume, chiffon color, chiffon swelling, texture profile, and moisture content in chiffon cake. A complete one-factor random design with Dunnet’s analysis was used.
 Results and Discussion: The results showed that overripe banana flour has yellowish color with a yield of 26.23±0.45%, a repose angle of 27.44±0.92, and a moisture content of 7.97±0.43% (wet base). Statistical analysis showed that chiffon of overripe banana flour did not differ significantly at 5% from than chiffon of fresh bananas on several parameters. They were the specific volume of the dough and moisture content and swelling, hardness, adhesiveness, elasticity, and chewing power. In addition, the chiffon’s crumb section of banana flour has a lower brightness compared to fresh banana chiffon, where the top, middle, and side crusts were not significantly different.
 Conclusion: These results indicated that the use of banana flour could replace fresh bananas in chiffon cake.

Wood surface modification with an arabinogalactan–silica composition

In this work, a method is proposed for increasing the operational properties of wood by treating it with organomineral compositions based on arabinogalactan and silica. Scots pine (Pinus silvestris) was chosen as the object of the study. Three different treatments were used. One treatment was a pure aqueous solution of arabinogalactan, the second and third were compositions based on aqueous solutions of arabinogalactan with 5% and 10% (by weight) addition of highly dispersed silica, respectively. Arabinogalactan was used as a surfactant for silica nanoparticles and also as a film-forming agent. The hardness of the wood surface increased by 1.2–2.3 times and compressive strength along the fibers increased by 20–45% after treatment with an organic–mineral composition. Treatment with impregnating compositions did not lead to a significant decrease in moisture absorption and swelling.

Influence of temperature and humidity on power cycling capability of power modules

Since power electronics becomes more and more important for harsh environments, its power cycling capability under these conditions needs to be known. The goal of this research is to identify how high temperature and humid environments contribute to the damage of power modules during power cycling. Therefore, IGBT modules are tested with power cycling in cold environment, hot, dry environment and hot, humid environment. Additionally, High Humidity High Temperature Reverse Bias testing is done for comparison of different failure mechanisms.Power modules under warm, humid conditions fail significantly earlier than in warm, dry, or even cold, dry environment. This is mainly attributed to two effects. Firstly to the moisture swelling and thermal expansion of the housing material at higher temperatures and humidity which have an influence on the pressure on the thermal interface and secondly the moisture uptake capability of the thermal interface material.

Structure for shape stable poly(vinyl alcohol) hydrogel under pH shock

Abstract Shape stable poly(vinyl alcohol) (PVA) hydrogels can be synthesized in acidic or basic medium. The PVA hydrogels yielded at acidic or basic pH can be applied to applications with aqueous solutions at opposite pH's. This study investigated the changes in linkage core and the shape stability of the PVA hydrogels subjected to opposite pH shock, with the sizes, weights and chemical composition changes for the yielded hydrogels, together with the FTIR, Raman and NMR spectroscopy, and the TGA analysis on the hydrogel samples being recorded and reported. With basic pH shock, the B(OH)3 ([B3]) cores in the “acidic” PVA hydrogels were converted to B(OH)4− ([B4]) cores; while with acidic pH shock, part of the [B4] cores in the “basic” hydrogels were transformed into [B3] cores. The acidic pH shock would deteriorate the shape stability and moisture swelling capability of the basic hydrogels; conversely, the basic pH shock would not affect shape stability but even enhanced swelling capability of the acidic hydrogels. The [B3][B4] or [B4] cores in the PVA matrix tend to enhance water stability of the hydrogels and the conversion of [B4] and SO42− ([S4]) to [B4][B4] or [B4][S4] dimers would destabilize the shape stability of the hydrogels. The findings proposed a way to manipulate the structure stability of PVA hydrogels by converting linkage cores in the matrix.

Preparation and evaluation of dual modified Ethiopian yam (<i>Dioscorea abyssinica</i>) starch for sustained release tablet formulations

Starch has been intensively studied over decades due to the fact that native starches are diverse, biodegradable, amenable to modifications and have enormous applications. In this study, Dioscorea abyssinica starch has been chemically dual modified by cross-linking using sodium hexametaphosphate (SHMP) followed by acetylation with acetic anhydride (AA). The physicochemical and tablet forming properties of the modified starches were investigated to determine potential usages in sustained release (SR) applications. Moisture sorption and swelling properties of the native starch (NS) were improved by the dual modification. The reduction observed in viscosity values indicated the effectiveness of cross-linking in reducing swelling of the NS. On the basis of powder properties analysis, it was evident that acetylation improved the poor flow property of NS. The starch acetylated at starch:AA ratio of 1:2 was found to be free flowing with angles of repose of 23.02o and flow rate 10.54 g/sec. The Hausner ratio and Carr’s index also confirmed the same, 1.25 and 20.24, respectively. Tablets were prepared and evaluated for hardness, tensile strength, friability, and disintegration time. Results indicated that both cross-linking and acetylation processes improved tablet forming properties of the NS with more significant effect in the dual modified starches. Matrix tablets containing Ac-CLS-F, where cross-linked starch (CLS – at 15% SHMP) reacted in a 1:2 ratio with AA, loaded with 20, 30 and 40% theophylline released 80% of theophylline in about 10.62, 9.35, and 8.18 h, respectively. From the foregoing, it can be concluded that Ac-CLS-F could have a potential for use as a sustained release excipient.Keywords: Dioscorea abyssinica, cross-linking, acetylation, dual modification, sustained release

Poly(glycerol adipate) – indomethacin drug conjugates – synthesis and in vitro characterization

The linear biodegradable polyester poly(glycerol adipate) (PGA) was synthesized via enzymatic polycondensation using lipase B from Candida antarctica (CAL-B). Every monomer unit of PGA possesses a pendant hydroxyl group which is responsible for the hydrophilic character and moisture swelling. These OH groups were esterified to different degrees with the anti-inflammatory drug indomethacin in order to create a prodrug with a pH-sensitive linker for modified drug release. The structure of the conjugates was determined via ATR FT-IR spectroscopy, NMR spectroscopy, GPC and UV/VIS spectroscopy. The physical properties of polymers with different drug load were investigated using DSC, contact angle measurements and oscillatory rheology. Drug release was monitored over one month in vitro. A very slow, but continuous release was observed in PBS. Slightly acidic conditions and lipase activity are accelerating the indomethacin release. Therefore, poly(glycerol adipate) − indomethacin conjugates are promising prodrugs for the local sustained release of indomethacin.

Soil-atmosphere Interaction as Triggering Factors of Openings between Embankment and Pavement

The analysis of openings between embankment and pavement due to uneven deformations of the highway embankment is incapable of accurate prediction when the pattern of seasonal weather variation is considered. This realization was used for elaborate openings analyses which include infiltration and evapotranspiration of the embankment soils to better predict atmosphere-induced openings between embankment and pavement at Nairobi where the longitudinal cracks of the pavement structure occurred during the period of the season alternation. The empirical equations were used to estimate evapotranspiration and the soil–water characteristic curve was established for the embankment soils. The consolidation theory and the moisture swelling model were then used to estimate performances of the highway embankment under atmospheric influence. A field test was conducted to verify the simulated moisture change in soil and soil movement, and small difference between simulated and measured values was found. The results showed that openings between embankment and pavement would occur when the highway embankment had undergone uneven deformations due to the rainfall and evapotranspiration, there were small openings during the dry season, but the maximum openings reached 10.2 mm and 25.5 mm during the first rainy season and the most intense rainy season, respectively.

Evaluation of the Dimensional Stability and Leaching Performance of ACQ/Wax Treated Southern Pine

Southern pine (Pinus sp.) wood cubes were treated with ACQ solutions with wax modification and post-treated at 70 °C for 10 h with hot air circulation. The effects of wax concentrations in ACQ-treated southern pine on its dimensional stability and copper leaching performance were investigated. The ACQ/wax-treated wood exhibited improved water resistance during the water soak process. The testing of swelling and shrinkage performance of the treated wood showed that samples with a higher percentage of wax had higher resistance to water swelling and shrinkage. The samples with a lower percentage of wax addition had only a slight effect on the moisture swelling and shrinkage resistance. As a result, copper leaching from ACQ/wax-treated wood with a 2% wax concentration was reduced to a lower level compared to ACQ-treated wood. When the proportion of wax in ACQ preservative was less than 1%, a higher percentage of copper was leached from treated wood.

Evaluation of tablet disintegrant properties of microcrystalline cellulose obtained from cassava fermentation waste

This study was aimed at exploring the application of microcrystalline cellulose from cassava fermentation waste as a disintegrant in the formulation of paracetamol tablets for immediate release. Alkali delignification of the dried cassava fermentation fibres, followed by bleaching and acid depolymerisation was employed in the extraction of α-cellulose and conversion to microcrystalline cellulose (MCC). The MCC obtained was evaluated for some of its physicochemical properties. Thereafter, a comparative evaluation of paracetamol granules and tablets formulated using the MCC and Avicel ® PH 101 as disintegrants was undertaken. Drug-excipient interaction was also investigated using fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Results showed a 48% yield of α-cellulose from the waste material. The MCC powder was off-white in colour, insoluble in water and gritty in texture. It showed negative reaction to the presence of starch, sugar and lignin but positive to cellulose. It exhibited a moisture content and swelling capacity of 2.1 and 63.3%, respectively. The paracetamol granules formulated showed good flowability with angles of repose ≤ 31 °, Hausner’s ratios of 1.07 - 1.18 and Carr’s indices of 6.58 - 16.00%. The formulated tablets showed good hardness (> 7 kp) and friability values (≤ 0.7%). Two batches of tablets containing 7.5 or 10% (w/w) of the MCC and three batches of tablets containing Avicel® (5, 7.5 and 10% (w/w) disintegrated within 15 min. The tablets containing 5 - 10% (w/w) of the MCC or Avicel® passed the dissolution test for tablets which specifies that at least 70% of the drug should be in solution after 30 min. FTIR and DSC analyses revealed no interaction between the excipients and paracetamol. MCC from cassava fermentation waste may serve as an alternative substance to explore as a pharmaceutical excipient in solid dosage form even though its tableting parameters are not as good as those of Avicel® PH 101. Keywords: cassava, microcrystalline cellulose, disintegrant, paracetamol granules, tablets

Hygro effects on the low-velocity impact behavior of unidirectional CFRP composite plates for aircraft applications

Hygro effect on the impact resistance of unidirectional (UD) CFRP composite plates under low-velocity impact loading are studied experimentally. Before the test, the UD specimens were immersed in water at 80°C for moisture absorption. Through the moisture ingress into the matrix–fiber interfacial region and resulting in the moisture swelling which may release the thermally induced residual compressive stresses around interfacial zone, certain degradation of disband at the interface of fiber and matrix was observed in the SEM pictures. The experimental results showed that the moisture content played a negative role by decreasing the impact resistance of composite plates. The composite plates with higher moisture level have small values of impact peak force, delamination threshold load, and initiation energy. The flexural rigidity of the unidirectional plates decreased as the moisture content increased, and the larger damage sizes were observed in wet specimens as compared to those of dry specimens.

Stress impact of moisture diffusion measured with the stress chip

The experimental observation of the actual thermo mechanical weak points in microelectronics packages remains a big challenge. Recently, a stress sensing system has been developed by the publicly funded project that allows measuring the magnitudes and the distribution of the stresses induced in the silicon dies by thermo-mechanical loads.Moisture can saturate a package very fast at high temperatures and high humidity within hours but also at low temperatures and low humidity within weeks or months. Every normal stored or used package will be swelled due to this moisture. A high temperature over a short time or within the first cycle of a temperature cycling test will dry the package and the internal stress of the package decrease. This moisture swelling will be investigated in this paper.All measurements are supplemented by finite element simulations based on calibrated models for in depth analysis and for extrapolating the stress results to sites of the package that are not measured directly. The methodology of closely combining stress measurements and FE simulation presented in this paper has been able to validate the stress sensing system for tasks of comprehensive design and process characterization as well as for health monitoring. It allows achieving both, a substantial reduction in time to-market and a high level of reliability under service conditions, as needed for future electronics and smart systems packages.

Tensile Strength and Water Absorption Behavior of Recycled Jute-Epoxy Composites

Recycled natural fi bers and biopolymers with sustainable, eco-friendly, and biodegradable properties are receiving increased attention. The moisture absorption and swelling of natural fi ber composites adversely infl uence their mechanical properties and applications. In this research, bio-based epoxy polymers that are reinforced with recycled woven jute fabrics were subjected to water immersion tests in order to study the effect of water absorption on their mechanical and geometrical properties. For comparison, petroleum-based epoxy polymers that are reinforced with new woven jute fabrics were also subjected to the same tests. The effect of fi ber percentage on water absorption, thickness swelling, and volume swelling was measured as a function of immersion time. It was observed that water absorption and swelling behavior were higher in bio-based epoxy than in petroleum-based epoxy composites. The stress decreased and the strain increased after water immersion in both composites. However, the rates of change in stress and strain were much more signifi cant for composites made with bioepoxy.

Effect of moisture swelling on MEMS packaging and integrated sensors

In MEMS packaging moisture uptake of packaging materials may lead to severe changes in sensor behavior and package reliability. Knowledge and understanding of the effect of moisture swelling on the overall package deformation and on the sensor system is therefore inevitable for a successful MEMS design and packaging solution. The paper shows a design optimization of a pressure sensor packaging towards minimization of sensor drift due to stresses induced by moisture uptake. The work was done in a combined experimental and simulative approach. Experimental data clearly shows the sensor sensitivity to moisture uptake of polymer based packaging material. Based on the experimental findings the complete sensor package was modeled by means of finite element analysis. In a second step a new packaging geometry was defined to reduce the effect of moisture swelling to sensor signal. Additionally sensitivity of the sensor output signal to viscoelastic properties of three different moulding compounds was simulated. In the result of the work an optimized package design was achieved.

Caracterização física e térmica de compósito de poliuretano derivado de óleo de mamona associado com partículas de bambu

Composites of Polyurethane (PU) resin derived from castor oil and bamboo particles (Dendrocalamus giganteus) were prepared by pressing with 10, 15 and 20% weight of PU. The aim of this study was to develop a new application of wastes from bamboo manufacture, minimizing the negative impact to the environment, adding a resin free of volatile organic compounds (COV). The composite characterization was performed with physical and thermogravimetric analysis. The association of PU and bamboo particles produced the expected effects, including a decrease in moisture content, swelling and water absorption as PU percentage increased. The Shore D hardness increased with the percentage of resin PU in the composite.

Characterization of interfacial toughness in carbon fiber/epoxy resin composite subjected to water aging using single‐fiber fragmentation method in an energy‐based model

AbstractThe toughness of the interphase between carbon fibers and epoxy resin was characterized by the interfacial fracture energy, which was derived from the modified Wagner‐Nairn‐Detassis (WND) model, considering the moisture swelling stress. The characterization was used to evaluate the changes of interphase bonding before and after water aging, including boiling water and 70°C water immersion. The effects of the water aging on the parameters in WND model were analyzed. The mechanism of interphase degradation under water aging was interpreted considering the change of interphase thickness, which was measured using the dynamic nanomechanical mapping method. It is shown that the single‐fiber fragmentation test with the proposed energy‐based model can quantify the degradation of interphase toughness after water aging. For the studied system, the interphase thickness has a close relationship with the interfacial fracture energy, indicating that the swelling of the resin matrix and interphase results in an increase in interphase thickness and a decrease in interphase bonding property. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

An Experimental and Computational Study on Moisture Induced Epoxy Swelling in Non-hermetic Optoelectronic Packages

Moisture induced epoxy swelling is a potential failure mechanism in nonhermetic packages. Epoxy materials used in the package absorb moisture and swell in a relatively humid environment. This will result in hygroscopic stresses in the material that can eventually lead to failure. The coefficient of hygroscopic swelling (CHS) is a material property that characterizes moisture induced swelling in the material. It is defined as the ratio of hygroscopic strain to the moisture concentration in the material. Prior research investigated the measurement of CHS experimentally using techniques such as thermo mechanical analysis (TMA) (Ardebili et al., 2003, “Hygroscopic Swelling and Sorption Characteristics of Epoxy Molding Compounds Used in Electronic Packaging,” IEEE Trans. Compon. Packag. Technol., 26(1), pp. 206–214; Mckague et al., 1978, “Swelling and Glass Transition Relations for epoxy Matrix Material in Humid Environments,” J. Appl. Polym. Sci., 22, pp. 1643–1654.), Moiré interferometry (Han et al., 2003, “Measurement of the Hygroscopic Swelling Coefficient in Mold Compounds Using Moire Interferometer Experimental Techniques,” IEEE Trans. Compon. Packag. Technol., 27(4), pp. 40–44), and digital image correlation (DIC) (Park and Zhang, 2007, “Investigation of Hygroscopic swelling of Polymers in Freezing Temperature,” ASME International Mechanical Engineering Congress and Exposition). Some of these studies recommended investigation of improved measurement techniques, while others made some procedural assumptions that may not be applicable for all materials. One of the goals of this study was to investigate an improved technique for CHS measurement and helps to better understand the various factors that affect the measurement. The DIC technique was used to measure the moisture swelling of the epoxy material considered for use in the package. Moisture loss during the measurement results in a change in moisture concentration in the sample. While it may be thought that the moisture loss during the DIC scan can be assumed negligible due to the short test time compared with other methods, this assumption did not hold well for the current epoxy material. The ramp rate chosen for the test affects the moisture loss. It introduces a level of nonuniformity in temperature and moisture distribution in the sample. A suitable value that takes into account both of these effects was determined. The moisture loss measured during the DIC scan was accounted for in the CHS computation. In addition to this, the temperature and concentration dependence of the CHS was determined. Results indicated that the temperature and concentration effects are small for the current test material within the test temperature range. The moisture loss found during the DIC measurement leads to a nonuniform moisture distribution in the sample. This was characterized by using experimental and computational methods and the effect on the measurement was determined.