Papers by Keyword: Swelling

Abstract: The application of bamboo by-products such as bamboo branches, chips to recycle and produce pressed bamboo pulp is an urgent task in Vietnam. It perfectly replaces natural wood with artificial wood embryos from bamboo powder, which has both economic benefits of reserving the source of raw materials, environmental protection... The paper presents a study of the influence of technological parameters on the water absorption and swelling thickness of pressed bamboo pulp plywood in order to ameliorate the quality of pressed bamboo pulp plywood in production of new materials for civil engineering with environmentally friendly bamboo wood pulp materials.

Abstract: The nanofiber PVA/chitosan have been successfully fabricated by the addition of TiO₂ or without TiO₂. Nanofiber membranes of PVA/chitosan/TiO₂ were fabricated with weight ratio of PVA/chitosan (w/w) 90/10, 85/15, and 80/20. Glutaraldehyde cross-linking was added to increase membrane stability in water. Swelling behavior was tested in three different pH to investigate the swelling behavior of nanofiber membranes of PVA/chitosan with and without TiO₂. The result indicated that the addition of chitosan concentration would decrease the swelling index, and increase the time constant (τ). The swelling index will increase in high pH (pH 10.01) compare to low pH (pH 4.01).

Abstract: Pectin is a derivative polysaccharides biopolymer that can be used as a material for an edible film. In this study, pectin edible film was made from a thin layer of edible pectin. The physical properties of the edible films such as elongation of the break, tensile strength, and the swelling degree were observed when carbonate hydroxyapatite (CHA) was added to the pectin edible film. In order to study the loading and release behavior of the pectin edible film, cinnamaldehyde (2 wt%) was also added to the film used as a drug sample. Cinnamaldehyde is known as a derivative compound of cinnamon bark. The edible film was made by mixing pectin (0.015 g/mL) and carbonate hydroxyapatite (CHA). Various concentration of carbonate hydroxyapatite (1, 3, 5, 7 wt%) was diluted in water and stirred using tween 80 and glycerol for about 1.5 h at a temperature of 70 °C. Then, cinnamaldehyde was added to the mixture and stirred for 30 minutes. The mixture was dried in an oven at a temperature of 50 °C for 15 h and stored in the desiccator. The experiment results showed that the tensile strength of pectin edible film was increased when more concentration of CHA added to the film, but the elongation of break and swelling were decreased. These results indicate that the addition of carbonate hydroxyapatite (CHA) affects the properties of pectin edible film significantly but does not affect the thickness of the film.

Abstract: The paper describes experimental measurement of volume changes of cement concrete. Volume changes include swelling and shrinkage of cement concrete specimens measured by string strain gauges both internal and external. Parallel to this measurement, the volume changes will be measured by means of shrinkage drains. The measurement of volume changes by the shrinkage drains is allowing continuous volume changes to be measured from the beginning of the setting of the concrete. It is possible to capture the entire process of hydration of concrete. The specimens are in the laboratory and in the outdoor environment, so it’s possible to compare values from different environments. The measured results are compared with the calculation models of shrinkage (Model B4 from Bažant [4]; Model Code 2010 [16] and ČSN EN 1992-1-1 [9]).

Abstract: The improvement of the thermal insulating material thermophysical characteristics of the thermal protection elements by studying the porous structure is a promising direction of research. The article describes the effects of the porosity and coupling of the porous structure on the thermophysical characteristics of thermal insulating materials. The article uses standard systematized techniques and instruments of scientific research applied in thermophysics. The research methodology of highly-porous material thermophysical properties is based on performance of empirical laboratory investigations of the samples obtained. It was found that for the pore structure effect on the material characteristics it is rational to use the following complex indices: porosity, number of pores, pore position in space, the pore form, pore formation energy. The article shows the effect of the porous structure on the thermophysical characteristics of the material. The complex parameters of the porous structure, which will allow to develop a new method of control of the porous structure, are proposed. As a result of the experiment planning method, the regression equation of an effective coefficient of thermal conductivity for porous thermal protection structures was developed. It was established that for a more even distribution of the mixture in a volume it is necessary to minimize the size of the dispersed components, thereby increasing the area of their contacts. The experimental method revealed that the moisture evaporation caused the formation of pores inside the clay. The shape of the pores was determined using electron microscope MMP-2P, both on the sample section and surface. The clearest clay has the greatest porosity (no iron oxide and calcium oxide). The pores have a spherical shape in it. The presence of impurities reduces the material porosity due to the increased clay viscosity.

Abstract: Different mesostructural elements of 16Cr-19Ni-2Mo-2Mn-Nb-Ti-B austenitic steel have been examined after neutron irradiation to damage dose up to 82 dpa by scanning electron microscopy using orientation microscopy (EBSD). Radiation porosity with maximum void size up to 200 nm was observed in austenitic steel structure after neutron irradiation. Nonuniformity, related to mesostructural elements, such as general grain boundaries, special CSL boundaries Σ3 (twins), areas with high density of low-angle boundaries, is typical for radiation porosity.

Abstract: The aim of this paper is to investigate whether ultraviolet radiation and elevated temperature influence the flexural strength, flexural modulus and swelling of glass fiber reinforced plastic pipes (GRP) over different aging periods. The degree of resistance to breaking on impact, and its measurement, is of practical importance in the selection and comparison of composite materials. Prepared samples from unused GRP pipe were subjected to ultraviolet radiation, humidity and elevated temperature prior to aging for 3, 6, 9, and 12 months in two different media, aquifer water and crude oil with high water cut. Flexural strength and modulus were obtained through a three-point bending test, results show that flexural strength noticeably decreases for samples aged in aquifer water when subjected to ultraviolet radiation. The exposed wet crude samples of composites to ultraviolet environment showed better flexural strength and modulus when compared to the unexposed samples. Maximum value of flexural strength (208 MPa) and flexural modulus (14.2 GPa) was observed for non UV aquifer water samples. In addition, swelling tests indicated that the pipe polymer matrix has a great resistance to solvent uptake which synergize with flexural modulus results for aquifer and wet crude samples. It can be found from this study that the combination of flowing chemicals in the pipe with the external factors such as elevated temperature and ultraviolet radiation have a notable impact over the polymer matrix and consequently on the composite physical properties .

Abstract: The article presents the data of an experimental study on how heat treatment influences the physical and mechanical properties of cured samples of sandwich structures. The sandwich structures were made using VaRTM method. Heat treatment at 80 °С and 60 °С leads to increase in the bending strength. Three-point bend tests of sandwich structures and FGRP were conducted. Also, hardness and tensile strength were determined. Heat treatment results in increase of bending stress of FGRP by 71%, via the the tensile strength of heat-treated FGRP increased by 78%. The results characterize the relationship between the durability and the temperature and exposure time of the sandwich structures. The results correlate with the data of swelling of the cured binder. As a result of heat treatment at 80 °С for 4 hours, the extent of swelling decreased by 14%. The heat treatment of sandwich structures at a temperature of 80 °С for 4 hours is optimal and leads to increase in the tensile strength by 30.7%.

Abstract: The article presents the data of an experimental study on how heat treatment influences the physical and mechanical properties of cured samples of sandwich structures. The sandwich structures were made using VaRTM method. Heat treatment at 80 °С and 60 °С leads to increase in the tensile strength. Three-point bend tests were conducted. The results characterize the relationship between the durability and the temperature and exposure time of the sandwich structures. The results correlate with the data of structural studies of fracture cross-sections and research on the extent of swelling of the cured binder. The SEM micrographs of the microstrustructures of fiberglass reinforced plastic samples show that during heat treatment there is a structural refinement of the polymer matrix. As a result of heat treatment at 80 °С for 4 hours, the extent of swelling decreased by 14%. The heat treatment of sandwich structures at a temperature of 80 °С for 4 hours is optimal and leads to increase in the tensile strength by 30.7%.

Abstract: Hydrophobic textile is a type of smart fabrics. Some of it are commonly coated with small particles and finally treated by water repellent agent in terms of acquiring its hydrophobic property. This research describes how hydrophobic textile are formed from its initial form of fabrics and even yarn, which are fibers. Synthesis process was commenced through wet spinning of viscose rayon mixed with nanorod silica which has been formerly produced with sol gel method. These fibers were then coated with chitosan and dried out by vacuum instrument. Scanning Electron Microscopy (SEM) results showed that nanorod silica were well attached on the fibers. Followed by Energy Dispersive Spectroscopy (EDS) mapping characterization, silica particles were moderately dispersed on its surface, performing roughness and creating hydrophobic effect. In addition, several characterization methods correlated to water absorption of the fibers were conducted. Fibers swelling percentage decreased from 50.2% to 17.13%, while moisture regain (MR) number also decreased from 14.28 to 10.72.