Swelling Coefficients Research Articles

Swelling properties and coefficient of permeability of friction-reducing polymer for pull-out of temporary sheet piles

Harmful cracks and settlements occur after the pull-out removal of temporary sheet piles. This is because a large amount of soil is discharged from the ground due to the significant skin friction at the steel surface. In order to prevent these cracks and settlement problems, a friction-reducing polymer was developed. After a sheet pile coated with the polymer is installed into the ground; the polymer absorbs ground water and transforms to a swollen gel layer which separates the soil and the sheet piles. In this investigation, a newly designed column type test apparatus was used to simulate ground conditions. The swelling test was carried out, followed by a continuous permeability test. Based on the obtained test results, the swelling properties and coefficient of permeability of the friction-reducing polymer in the ground were determined. The main conclusions are as follows. The values of the water-absorbing ratio, Ramax, decrease with increasing earth pressure, p′, independent of the pore water pressure, u. Equations to determine the values of Ramax are proposed as functions of p′ only. The maximum swelling pressure, at which the friction-reducing polymer cannot absorb water and swell, is p′max = 560 kPa. Even at a depth of approximately 100 m, the polymer absorbs ground water, and the swollen gel layer forms. The approximate range of coefficient of permeability, k, of the swollen gel layer is 10−13–10−11 m/s; these are extremely small values. The swollen gel can be considered an impermeable material. Depth distributions of the thickness and the coefficient of permeability of the swollen gel layer are illustrated in practical charts, based on the test results.

Effect of wax and dimethyl silicone oil pretreatment on wood hygroscopicity, chemical components, and dimensional stability

Wood is a renewable and environmental friendly material, but its low dimensional stability characteristics limit its applications. In this study, wax mixed with dimethyl silicone oil was used to enhance the dimensional stability under heat treatment. Samples were heated at 120 °C under 3 impregnation conditions (wax, wax + 20% dimethyl silicone oil, and wax + 40% dimethyl silicone oil) for 3 and 6 h respectively. After treatment the effects of combination pretreatment on wood weight gain percentage (WPG), tangential, radial and volume swelling coefficients (TS, RS, VS), distribution of impregnation liquid, and the types of functional groups of African Padauk (Pterocarpus soyauxii) were evaluated. The results showed that impregnation improved the dimensional stability of wood to a certain extent; moreover, the addition of dimethyl silicone oil improved the modification effect. Furthermore, the VS reduced to 0.66 (±0.28)% in the treatment of wax + 20% dimethyl silicone oil for 6 h. The impregnation liquid mainly adhered to the walls of vessels and ray cells. The hydroxyl absorption intensity of the impregnated groups was lower than that of the control group.

Analysis of coal permeability rebound and recovery during methane extraction: Implications for carbon dioxide storage capability assessment

Coal permeability rebound and recovery severely affect the efficiency of coalbed methane extraction and CO2 storage capability of coal seams, but theoretical research on it is insufficient now. Besides, ambiguity still remains in evolution laws of coal permeability rebound and recovery pressure with the change of various influencing factors. In this work, the focus is first placed on the influences of effective stress (considering engineering-strain and natural-strain) and adsorption-induced swelling (considering matrix bridge) on fracture aperture; then, a new evolution model of coal fracture aperture is established by adopting the competition mechanism of the two. At the same time, based on the correlation between the variation of fracture aperture and permeability using the classical cubic law, the evolution model of coal permeability is set up, of which is on the basis together with some reasonable assumptions to obtain the factors influencing permeability rebound and the recovery pressure. The evolution laws of coal permeability rebound and recovery under the influence of main factors are in detailed analysis. Specifically, permeability rebounds and recovers when the initial coal reservoir pressure is greater than its switching threshold. The greater the initial pressure, the larger the numerical range dropping from the initial value to rebound value, so does the effect of coal cleat compressibility. However, only on condition that the internal swelling coefficient is smaller than its switching threshold, the permeability will rebound and recover. Besides, the influencing mechanism of CO2 storage and CBM extraction on permeability evolution is the same, while the variation laws of permeability, of rebound and recovery especially, exert strong impact on CO2 storage capability. Therefore, the influence of various permeability evolution laws on CO2 storage capability is discussed macroscopically for valid assessment of it, providing guidance to select appropriate coal seams for CO2 storage.

In-situ characterization of moisture absorption and hygroscopic swelling of silicone/phosphor composite film and epoxy mold compound in LED packaging

In this paper, moisture absorption/desorption and hygroscopic swelling of silicone/phosphor composite film and epoxy mold compound (EMC) used in chip-on-board (COB) LED packaging is studied with in-situ characterization. Material properties, including diffusivity, activation energy, saturated moisture concentration and the coefficient of hygroscopic swelling, are extracted from the experimental data. For silicone/phosphor film, the moisture diffusion can be described by the conventional Fickian diffusion model. However, the saturated moisture concentration increases with temperatures under the same relative humidity condition. The dependence of saturated moisture concentration on temperature is characterized by an Arrhenius-like equation, and the net absorption heat is found to be 8–11 kJ/mol. Furthermore, the silicone/phosphor composite film shows reversible diffusion process during absorption and desorption cycle, which confirms the Fickian behavior of moisture absorption. Moisture diffusion in EMC, on the other hand, exhibits non-Fickian diffusion, and thus, a dual stage diffusion model is adopted to fit experimental data. Moreover, EMC shows partially non-reversible moisture absorption during absorption and desorption cycle, which is consistent with the dual-stage model description. In hygroscopic swelling testing, silicone/phosphor film shows a permanent swelling during moisture absorption despite that the moisture absorption is completely reversible. EMC shows partially reversible swelling after moisture is removed, which indicates the residual moisture in material. Further study is needed to understand the mechanism of permanent hygroscopic swelling for silicone/phosphor composite during moisture absorption and desorption.

Characterisation of moisture diffusion and strength degradation in an epoxy-based structural adhesive considering a post-curing process

Adhesive bonding techniques have been widely used in many industrial fields, such as aerospace, vehicle and civil engineering, etc., while the bonded structures are designed to perform satisfactorily under complex service conditions. This paper presented an experimental insight into the moisture diffusion process in Araldite 2015 adhesive considering the effect of post-curing process under elevated temperature. Polytetrafluoroethylene mould was adopted for the curing process of dumbbell adhesive specimens and both distilled and salt water were introduced to simulate a severe immersion environment. Quasi-static testing was conducted on both unaged and aged bulk adhesive after certain period of immersion to reveal the mechanical properties variation. Measurements on specimen weight and thickness were performed with different time intervals during the immersion process. It is shown that the strengths of bulk adhesive were significantly degraded due to the presence of water in both immersion conditions, where higher moisture content led to greater strength degradation regardless of the curing and ageing conditions applied. In addition, distilled water environment led to notably higher saturation content and hygroscopic swelling compared to salt water. However, the rates of water diffusion and hygroscopic swelling processes in salt water were detected to be far above the ones in distilled water. It is worth noting that slight increase was observed in moisture saturation content and swelling expansion for post-cured adhesive, while the coefficients of hygroscopic swelling showed no difference for all sample groups studied. Scanning Electron Microscopy observation further revealed the transition in microscopic topography from unaged to saturated samples.

Gellan Gum Hydrogels with Enzyme-Sensitive Biodegradation and Endothelial Cell Biorecognition Sites.

The survival of a biomaterial or tissue engineered construct is mainly hampered by the deficient microcirculation in its core, and limited nutrients and oxygen availability to the implanted or colonizing host cells. Aiming to address these issues, we herein propose bioresponsive gellan gum (GG) hydrogels that are biodegradable by metalloproteinase 1 (MMP-1) and enable endothelial cells adhesion and proliferation. GG is chemically functionalized with divinyl sulfone (DVS) and then biofunctionalized with thiol cell-adhesive peptides (T1 or C16) to confer GG endothelial cell biorecognition cues. Biodegradable hydrogels are then formed by Michael type addition of GGDVS or/and peptide-functionalized GGDVS with a dithiol peptide crosslinker sensitive to MMP-1. The mechanical properties (6 to 5580 Pa), swelling (17 to 11), MMP-1-driven degradation (up to 70%), and molecules diffusion coefficients of hydrogels are tuned by increasing the polymer amount and crosslinking density. Human umbilical cord vein endothelial cells depict a polarized elongated morphology when encapsulated within T1-containing hydrogels, in contrast to the round morphology observed in C16-containing hydrogels. Cell organization is favored as early as 1 d of cell culture within the T1-modified hydrogels with higher concentration of peptide, while cell proliferation is higher in T1-modified hydrogels with higher modulus. In conclusion, biodegradable and bioresponsive GGDVS hydrogels are promising endothelial cell responsive materials that can be used for vascularization strategies.

Modeling the effects of lipid contamination in poly(styrene-isobutylene-styrene) (SIBS)

Lipid uptake and subsequent degradation was characterized as a function of molecular weight and styrene content in four different formulations of poly(styrene-block-Isobutylene-block-styrene) (SIBS). Mechanical testing in uniaxial tension at varying lipid concentrations showed a consistent decrease in tensile strength for all specimens due to lipid contamination. Higher styrene content was associated with an improved resistance to lipid intrusion. A decrease in elongation at break was observed for low molecular weight formulations only; an expected result of the stiffer network and local chain motion restriction due to increased entanglements in high molecular weight SIBS. A new, coupled diffusion/finite element method was used to recover the swelling coefficient of the four different SIBS formulations. The Ogden strain-density energy function recovered from unidirectional tensile testing and diffusion properties from gravimetric analysis were used to construct the finite element model. The predicted swelling behavior matched experimental data and the swelling coefficients were recovered for all formulations tested. Results indicate that the higher lipid affinity of the isobutylene phase contributed to increased swelling, as expected. This novel method to calculate swelling coefficient effectively circumvents the inability of commonly-used thermal deswelling methods to characterize lipid and oil-induced swelling behavior; enabling better prediction of long-term in vivo performance of polymer-based biomedical devices and more accurate evaluation of lipid-induced degradation and swelling.

SWELLING ANISOTROPY OF STRAIGHT-GRAINED AND WAVY-GRAINED WOOD OF ABIES ALBA MILL.

Вивчено особливості анізотропії розбухання прямоволокнистої та хвилясто-завилькуватої деревини ялиці білої в межах радіуса та висоти стовбура. Дослідженнями охоплено ялицевий деревостан у вологій смереково-буковій суяличині Буковинських Карпат. Взірці деревини відібрано з 12 модельних дерев ялиці білої із прямоволокнистою та хвилясто-завилькуватою структурою деревини. Встановлено, що середні значення тангентального та радіального розбухання прямоволокнистої деревини є більшими від аналогічних показників хвилясто-завилькуватої. Середні значення розбухання прямоволокнистої деревини за об'ємом становить 14,2-14,3 %, а для хвилясто-завилькуватої деревини – 11,9-12,1 %. Величина поперечної анізотропії розбухання прямоволокнистої деревини є на 20 % більшою від подібного показника для хвилясто-завилькуватої деревини ялиці білої. Щільність прямоволокнистої деревини при абсолютній вологості 8 % становить 380 кг∙м-3 на висоті стовбура 1,3 м. Взірці хвилясто-завилькуватої деревини характеризуються на 21 % більшими середніми значеннями щільності деревини за абсолютної вологості 8 %. Щільність мокрої деревини змінюється від 900 до 1100 кг×м-3 за абсолютної вологості від 106 до 224 %. Встановлено істотні відмінності показників анізотропії розбухання та об'ємної маси прямоволокнистої та хвилясто-завилькуватої деревини ялиці білої.

New fire retardant compositions for fire-resistant automatic curtains

The paper overviews the way by which intumescent fire retardant compositions act as fillers in fire-resistant automatic curtains. A several intumescent compositions, which form a heat-isolating charred layer when they are exposed to high temperatures, were produced and applied to the mineral-fabric basis of the curtain. Fire-protective properties of produced materials were assessed and compared with foreign specimens. Swelling coefficient and material’s fire durability were considered as operating parameters. The developed specimen which performed the best during fire tests was sent to accredited laboratory. It was proven, using standardized methods, that it’s fire resistance limit reaches 30 minutes. This proves an effective contribution of an intumescent compound and opens new ways of using them in fire curtains manufacturing.

Microstructural characterization and evaluation of certain important physical properties of thuja burl wood

This investigation aimed to characterize certain important anatomical, chemical and physical properties of Tetraclinis articulate (Thuja) burl wood from Morocco. Anatomical properties and constituent structure were analysed using image analysis system, environmental scanning electron microscope (ESEM) and powder x-ray diffraction techniques. A few important physical properties of Thuja burl wood such as density, specific gravity, equilibrium moisture content (EMC), total swelling and water absorption characteristics were evaluated. Real-time water absorption and swelling profiles were recorded electronically using a digital force sensor and linear variable differential transformers (LVDTs) respectively. Microscopic structure observed on fractured surfaces showed very compact and thread-like fibers. Average crystallinity index and diameter of cellulose crystallite was found to be 0.35±0.03 and 36.00±5.58 A respectively. The average values of air-dry density and the EMC of Thuja burl wood were 932.67±50.57 kg/m3 and 10.19±1.43% respectively. Swelling profile as a function of the water immersion duration followed a curvilinear variation with maximum swelling coefficient of 2.9±0.43% after 24 hour from oven-dry condition. The suitability of this wood for decorative and handicraft items is attributed mainly to its dense microstructure, higher dimensional stability, lower water absorption, random grain texture, dark brownish with intense and pleasant smell.

Synthesis and evaluation of pH dependent polyethylene glycol-co-acrylic acid hydrogels for controlled release of venlafaxine HCl

pH dependent polyethylene glycol/acrylic acid(AA/PEG) hydrogels of an anti-depressant, venlafaxine hydrochloride were prepared by free-radical co-polymerization method, using benzyl peroxide (BPO) as initiator and methylene bisacrylamide (MBA) as cross-linker. Different formulations were prepared with varying concentration of polymer, monomer and cross-linker to study their effect on gel swelling, diffusion characteristics and subsequent drug release. Structural parameters of AA/PEG hydrogels were investigated by measuring diffusion co-efficient, volume fraction of polymer in the swollen state, effective molecular weight of polymer chain between cross-linking points, the number of links between two crosslink and solvent interaction parameters. Swelling coefficients were found to be increased with increase in pH i.e. minimum at pH 1.2 and maximum at pH 7.5. Increase in acrylic acid concentration increases swelling while increase in cross-linker concentration has an opposite effect due to denser structure. AA/PEG hydrogels were characterized by fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-Ray diffraction (XRD), thermo gravimetric analysis (TGA) to determine the polymer structure, its morphology and strength. Drug release studies performed at pH 1.2, 5.5 and 7.5 shows higher release at higher pH. Drug release was increased by increasing acrylic acid concentration and decreasing cross-linker concentration.

Physical characteristics, proximate composition and anti-nutritional factors in grains of lablab bean (<i>Lablab purpureus</i>) genotypes from Kenya

Objectives: The objectives of this study were to determine the physical characteristics, nutritional composition and anti-nutritional factors of grains from three lablab bean varieties with different colours and size developed by The Kenya Agricultural and Livestock Research Organisation (KALRO) Methodology and results: The length, thickness and width were determined using Vernier callipers. Dry matter, protein, fat and ash were determined using standard association of official analytical chemists (AOAC) methods. Phytates were determined using high performance liquid chromatography (HPLC), while the tannins and trypsin inhibition were determined by UV spectrophotometry. The mean 100 seed weight was significantly different among the three varieties, and ranged from 26.1 g to 29.2 g. The length, thickness and width ranged from 9.7 for KAT/DL-3 to 10.7 mm for KAT/DL-1, 5.2 (KAT/DL-1) to 5.6 mm (KAT/DL-2) and 6.8 (KAT/DL-3) to 7.4 mm (KAT/DL-1), respectively. The hydration and swelling coefficients of the beans ranged from 130.7 in KAT/DL-2 to 147.2 in KAT/DL-1, and 125.1 in KAT/DL-2 to 153.3 (KAT/DL-1), respectively. The mean crude protein and energy contents varied from 22.5(KAT/DL-3) to 25.4 %,( KAT/DL-1) and 347.4 (KAT/DL-3) to 353.7 KCal/100g in KAT/DL-1, respectively, and differed significantly (p<0.05) among the varieties. There were significant differences (p<0.05) in the phytic acid and tannin levels, where KAT/DL-2 recorded the highest levels of 723.6 mg/100 g, and 0.33%CE, respectively. Conclusion and application of findings: These results indicate that KAT/DL-1 has the best physical characteristics in respect to cooking and nutrition quality. This variety had the highest protein and energy content with low anti-nutritional factors, thus could offer better nutritive value in comparison to KATDL-2 and KAT/DL-3 Keywords: Lablab beans, varieties, proximate composition, physical parameters, anti-nutritional factors

Integrating artificial neural network and imperialist competitive algorithm (ICA), to predict the energy consumption for land leveling

PurposeThis work aims to determine the best linear model using an artificial neural network (ANN) with the imperialist competitive algorithm (ICA-ANN) and ANN to predict the energy consumption for land leveling.Design/methodology/approachUsing ANN, integrating artificial neural network and imperialist competitive algorithm (ICA-ANN) and sensitivity analysis (SA) can lead to a noticeable improvement in the environment. In this research, effects of various soil properties such as embankment volume, soil compressibility factor, specific gravity, moisture content, slope, sand per cent and soil swelling index on energy consumption were investigated.FindingsAccording to the results, 10-8-3-1, 10-8-2-5-1, 10-5-8-10-1 and 10-6-4-1 multilayer perceptron network structures were chosen as the best arrangements and were trained using the Levenberg–Marquardt method as the network training function. Sensitivity analysis revealed that only three variables, namely, density, soil compressibility factor and cut-fill volume (V), had the highest sensitivity on the output parameters, including labor energy, fuel energy, total machinery cost and total machinery energy. Based on the results, ICA-ANN had a better performance in the prediction of output parameters in comparison with conventional methods such as ANN or particle swarm optimization (PSO)-ANN. Statistical factors of root mean square error (RMSE) and correlation coefficient (R2) illustrate the superiority of ICA-ANN over other methods by values of about 0.02 and 0.99, respectively.Originality/valueA limited number of research studies related to energy consumption in land leveling have been done on energy as a function of volume of excavation and embankment. However, in this research, energy and cost of land leveling are shown to be functions of all the properties of the land, including the slope, coefficient of swelling, density of the soil, soil moisture and special weight dirt. Therefore, the authors believe that this paper contains new and significant information adequate for justifying publication in an international journal.

Impact of matrix–fracture interactions on coal permeability: Model development and analysis

In this study, we develop a new permeability model that incorporates the matrix–fracture interactions. In addition, a newly defined internal swelling coefficient (f) has been introduced to quantify the contribution of adsorption-induced matrix deformation to fracture aperture and coal permeability. The model is independent of the boundary conditions and has been verified with the data tested under the conditions of uniaxial strain, constant external stress, constant effective stress, and constant pore pressure. Besides, a comparison between the commonly used models and our model shows that our model can cover most of the variation trends of the other models. The influencing factors and the mechanisms controlling the internal swelling coefficient have been comprehensively discussed. The results show that under the conditions of uniaxial strain and constant effective stress, f shows a downward trend with a reduction of the pore pressure, whereas under the constant external stress condition, f presents an opposite variation trend. The gas type has an effect on the internal swelling coefficient and f decreases in the order of N2, CH4, and CO2. In addition, the coal type also affects the internal swelling coefficient. All the factors indirectly affect the internal swelling coefficient by changing the effective stress and adsorption-induced matrix deformation. We have also investigated the controlling mechanism of the internal swelling coefficient on permeability, which indicated that the permeability shows an opposite variation trend with the internal swelling coefficient. It is suggested that the internal swelling coefficient can be set as a value in the range of 0–0.2 for the prediction of coal seam permeability during CBM recovery and CO2 geological sequestration.

Preparation and characterization of a composite biomaterial including starch micro/nano particles loaded chitosan gel

Thermosensitive Chitosan hydrogels which can be injected into defects with minimally invasive approach were prepared. Also starch micro/nano particles were synthesized via water-in-oil (W/O) miniemulsion technique. The starch particles were incorporated into the chitosan hydrogel to prepare injectable thermosensitive hydrogel composites. Tube inverting method, compression tests, swelling studies, XRD, SEM, OM, DLS, UV–vis spectroscopy were used for investigations. Results revealed that increasing crosslinker and surfactant contents and stirring rate leads to particle size reduction. Particle size was modeled using design of experiments (DOE) via the response surface method (RSM). Due to analysis of variance (ANOVA), the particle sizes can be predicted by quadratic model within the design space. Gelation time and compressive modulus measurements showed the particles significant influence on the blend network density and hydrogel mechanical properties. Swelling measurements revealed that incorporation of starch particles in chitosan hydrogel increases its swelling coefficient significantly. The innovative architecture, namely micro/nano particles in gel can be considered as a dual delivery platform or smart scaffold for engineering of certain tissues.

On the interpretation of cryogenic sorption isotherms in glassy polymers

Sorption data of nitrogen, argon and krypton in different glassy polymers at different cryogenic temperatures are analyzed, including hydrogen in PIM-1; conventional and high free volume glassy polymers are included. A consistent interpretation of experimental data is obtained by considering penetrant dissolution in a uniform dense glassy polymer, undergoing volume swelling with all penetrants but hydrogen. All the data are properly described by using the NELF model which is appropriate for the solubility in glassy polymers. Remarkably, in each polymer the sorption isotherms of different penetrants are described well by using the same initial polymer density, and the same swelling coefficient value allows satisfactory description of the sorption behavior of one penetrant at different temperatures. For PIM-1, NELF model and molecular dynamics give exactly the same swelling, and desorption after sorption or subsequent sorption-desorption cycles show hysteresis effects clearly associated to irreversible volume changes; in addition, hydrogen sorption in PIM-1 is fully predicted by the NELF model, simply based on nitrogen sorption, as opposed to BET theory. On the bases of the above results the conclusion is drown that BET theory is not applicable to the cryogenic sorption isotherms in glassy polymers.

Establishment of the mechanism and fireproof efficiency of wood treated with an impregnating solution and coatings

Description of the behavior of fireproof means and coatings, including those swelling, in the moment of the formation of a thermal insulating structure is a special and complex task. In general, it covers both stages of the process of thermal protection: both heat transfer and subsequent swelling of the coating, which is formed during fire protection. In necessitates studying conditions for the formation of barrier to thermal conductivity and the establishment of a mechanism of fire protection from layer to a layer of coke. Given this, we examined the process of fire protection with work of an impregnating solution and at swelling of a fireproof coating. Data that we obtained revealed that the formation of volatile products under the effect of coating at high temperature occurs with the formation of noncombustible substances. We established experimentally that under the action of heat flow on the fireproof samples, intense release of inert gases occurs, as well as a reduction in the combustible, which leads to the effectiveness of fire protection in reverse order. It was found in the course of conducted tests that the intensity of the formation of noncombustible gases shifts toward elevated temperature with the formation of coked cellular material. Results of determining a swelling capacity of coating for the intumescent system demonstrated that under the influence of high-temperature flow, material combustion and weight loss of the coating is reduced by more than twice due to the formation of high-temperature compounds; in this case, the time to reach a limit temperature grows as well. A coating under the influence of high temperature forms a significant coefficient of swelling, contributes to the formation of a thermal insulating layer of coke, which prevents wood from burning, as well as the passage of high temperature to the material. In general, the efficiency of wood fire protection revealed that the goods belong to the materials that are difficult to combust, which spread the flame over surface slowly and with low smoke-generating capacity. protection means; fire resistance; volatile products; loss of weight; surface treatment; efficiency of protection

Hygroscopic Swelling Determination of Cellulose Nanocrystal (CNC) Films by Polarized Light Microscopy Digital Image Correlation.

The coefficient of hygroscopic swelling (CHS) of self-organized and shear-oriented cellulose nanocrystal (CNC) films was determined by capturing hygroscopic strains produced as result of isothermal water vapor intake in equilibrium. Contrast enhanced microscopy digital image correlation enabled the characterization of dimensional changes induced by the hygroscopic swelling of the films. The distinct microstructure and birefringence of CNC films served in exploring the in-plane hygroscopic swelling at relative humidity values ranging from 0% to 97%. Water vapor intake in CNC films was measured using dynamic vapor sorption (DVS) at constant temperature. The obtained experimental moisture sorption and kinetic profiles were analyzed by fitting with Guggenheim, Anderson, and deBoer (GAB) and Parallel Exponential Kinetics (PEK) models, respectively. Self-organized CNC films showed isotropic swelling, CHS ∼0.040 %strain/%C. By contrast, shear-oriented CNC films exhibited an anisotropic swelling, resulting in CHS ∼0.02 and ∼0.30 %strain/%C, parallel and perpendicular to CNC alignment, respectively. Finite element analysis (FEA) further predicted moisture diffusion as the predominant mechanism for swelling of CNC films.

Characterization of acoustic and mechanical properties of common tropical woods used in classical guitars

There is a need of substitution woods for the use in musical instruments because of the limited availability of some commonly used tropical tonewoods. Before substitutions can be found, it is necessary to know about the required properties. Hence, in this paper acoustical, mechanical and physical properties of four common tropical hardwoods (Indian rosewood, ziricote, African blackwood and ebony) were determined because there are less literature values for some properties available, e.g. internal friction, hardness or swelling behaviour. The acoustic properties were determined by means of experimental modal analysis, the mechanical properties by means of static bending tests and tests of the Brinell hardness. For the swelling behaviour the volume swelling and also the differential swelling coefficients were determined. With the results it is possible to look for new ‘tonewoods’ or to specifically modified woods, e.g. thermally treated wood, to substitute tropical wood species.

The effect of organoclays on the fire-proof efficiency of intumescent coatings

We explored thermal transformations of the intumescent system (ammonium polyphosphate, pentaerythrite, melamine, copolymer of styrene acrylate) in the temperature range of 200–600 °C in the presence of organomodified montmorillonites and titanium nano-oxide. Coefficients of swelling, masses of coke residues are determined and morphology of the formed coke layer is investigated. These data were used for the development of formulations for effective fire-retardant coatings of the intumescent type, which do not contain halogen fire retardants. As a result of the research, it was established that montmorillonite and organic clays on its base (cetyltrimethylammonium-montmorillonite and tallow bis-hydroxyethyl methyl ammonium-montmorillonite), in contrast to titanium nano-oxide, significantly inhibit the processes of swelling at the initial stages of fire action. At temperatures above 500 °C, the intumescent compositions, which contain organic clays, form a durable and dense coke layer. IR-spectrometric studies of the samples of coke with the participation of organoclays demonstrate deceleration of oxidation processes and decomposition of polymeric protective layer in contrast to the composition with titanium oxide and nano-oxide. Based on these observations, we give practical recommendations regarding the preparation of formulations for fire-retardant coatings for the building structures depending on the required limit of fire resistance. It is recommended to use additives of nano-oxides for the class of fire resistance R 30–R 45; and for the class of fire resistance R 60 and above, organoclay should be added to the intumescent system. This assumption was confirmed by firing tests of steel columns. The results we obtained may be used for the design of new fire-retardant coatings of the intumescent type with improved efficiency and ecological safety.