Papers by Keyword: Water Vapour Permeability

Abstract: Starch-based biodegradable films of polybutylene adipate co-terephthalate (PBAT) have been prepared by the solution casting method. The effect of heating at two different temperatures (80 and 110°C) on the mechanical, optical and morphological properties of these films has been evaluated. The two temperatures were selected based on the crystallization and melting temperatures of PBAT. The blend of PBAT with thermoplastic starch has been prepared by melt mixing technique using two roll mills and then the solution casting method has been followed to prepare the films. Apart from curing at room temperature, the films have been cured at 80°C and 110°C. The tensile strength of the films increased by 110% and 252% for films heated to 80°C and 110°C, respectively. As revealed from spectroscopic analysis, the heating of films has no significant effect on the absorption of light by the films in the UV-visible region. The bonding characteristics of the films have been evaluated using Fourier transform infrared (FTIR) spectroscopy. The lowest water absorption and vapour permeability have been obtained in films cured at 80°C.

Abstract: Hemp concrete is one of the most used bio-based materials in the construction industry due to its hygrothermal behaviour and its low environmental footprint. This is mainly due to the complexity of the microstructure of these materials and their highly breathable nature. However, their use remains limited due to the lack of databases and guarantees regarding of the evolution of their functional properties over time. In this paper, experimental investigation has been performed to answer this problematic. The aim is to investigate the influence of accelerated aging on the properties of this material through a succession of immersion/freezing/drying cycles. Materials (aged and reference) were characterized at the same relative humidity state in order to be able to compare the results and to highlight the effect of ageing on the properties of hemp concrete. Results revealed a significant change in the microstructure of this material. As a consequence, this induced significant changes in its hygrothermal and mechanical properties. An increase of 40% in water vapour permeability and decrease of 57% in compressive strength were observed after aging (07 cycles of immersion/freezing/drying).

Abstract: The food packaging material provides protection against moisture, heat, enzymes, oxygen penetration etc. The shelf life of food can be increased by coating barrier materials on plastic films. In this work the oxygen transfer rate (OTR) and water vapour permeability (WVP) of Polyethylene terephthalate (PET) films were adjusted via coating of Polyphenols and Gelatin mixture (PGM) with different concentrations while maintaining the other properties of modified PET films. This article deals with the changes in properties of PGM coated PET films with some innovative ideas of multilayer film formulation. Polyphenolics were extracted from Terminalia Catappa (Indian almond), Camellia sinensis (Green tea leaves) and Trachyspermumammi (Ajwain). The results showed that WVP was decreased from 1.0±0 to 0.12±0.03 g/in2/day (p < 0.01) in comparison with uncoated (1.3±0.07g/in2/day). Similarly, same trend was obtained for OTR (63.5±0.02 to 38.1±0.03g/in2/day) with respect to uncoated film (82 ± 3.5). This study provides important evidence that addition of PGM on PET films leads to improved films in terms of OTR and WVP with minor changes in optical properties.

Abstract: In the paper there are summarized results of diffusion properties of mortars. Water vapour permeability represented by diffusion thicknesses and water vapour resistance factors are except mechanical properties the most important physical parameters of historic buildings. These parameters are influenced by border conditions among that mainly temperature, relative humidity and barometric air pressure belong. It is necessary to know these parameters to understand a material behaviour after a flood. They are decisive for a determination how quick a diffusion speed rate will be and a drying process will take. Everything depends on a type of binder, a material of a structure itself and primarily on properties of mortar and plaster and finishing. After a flood it is necessary to know when users of buildings can start to make rehabilitations and which of them are proper for particular material and when can return to their homes.

Abstract: The paper summarizes the results of water vapour resistance factors of three commonly used compositions for wall finishing (basic adhesive diffusion mortar; basic adhesive diffusion mortar + silicate plaster; basic adhesive diffusion mortar + acrylic plaster). The border conditions of the measuring (temperature, relative humidity and barometric air pressure) and their impacts on the results are discussed as well.

Abstract: In last decades, increased attention is paid to comfort properties of textiles and garments. The most important parameters characterizing the called physiological comfort of textile structures are the evaporative resistance and water vapour permeability. Contrary to common textiles, protective and functional garments and, also some technical textiles, are also used in wet state, which affect their comfort properties. In this paper, PERMETEST commercial instrument is described, which provide reliable non-destructive measurement of evaporative resistance and water vapour permeability of fabrics in dry and wet state. By means of this instrument, evaporative resistance and water vapour permeability of cotton, polyester and cotton/polyester knitting fabrics, in the wet state, were experimentally determined and results were discussed. The effect of count yarn and composition of the above mentioned properties of these fabrics has been investigated as well. Some surprising results were achieved: with increasing fabrics moisture, the water vapour permeability also increases, especially with the presence of hydrophilic textile material.

Abstract: Chitosan is an abundant, natural polysaccaride obtained from fishing industry waste and films of chitosan also provide an efficient oxygen barrier. However, they are a poor water vapor barrier, which can be improved by incorporation of a hydrophobic compound, forming a emulsified film. Chitosan films were produced with the addition of palmitic acid lipid analysis and then the process in parallel with the diffusive permeability to water vapor. The objective of this work was to characterize the diffusion and water vapor permeability behavior of chitosan films and chitosan emulsified films.

Abstract: In the paper, preparation and properties of pullulan composite films were studied. Several kinds of materials (glass, iron, steel, propene polymer and polyvinyl chloride plates) were chosen for preparing films. The results showed that the steel plate was the most suitable material for preparing film. The tensile strength of pullulan film was significantly reduced when the drying temperature was higher than 50°C. The time of dissolution observably decreased, whereas water vapor permeability increased with increasing drying temperature. Pullulan film has higher tensile strength, better water barrier properties, shorter solubilization time and lower elongation at break than those of hydroxypropylmethylcellulose film, respectively. The composite film (Pullulan and hydroxypropylmethylcellulose) with weight ratio (1/2) has higher tensile strength, better water barrier properties, longer solubilization time than those of other ratios. Difference properties of films could be obtained in different weight ratio (Pullulan and hydroxypropylmethylcellulose).

Abstract: The development and research of new thermal insulation materials become a hot point due to the demand of building energy efficiency and high hygrothermal environment. Although there are many kinds of insulation materials in Chinese market, most of them are made from oil. It is very important to develop new thermal insulation materials to decrease the emission of CO2 and the use of non-renewable energy. The new materials have the function of reducing carbon emissions, improving the insulation performance of building envelope and indoor hygrothermal environment. However the research on hygrothermal characteristic of eco-fiber production is still kind of new work, such as water vapor permeability, thermal conductivity, water absorption coefficient, and isothermal sorption curve and so on, especially water absorption coefficient which doesn’t obey the classical model, according to the classical standards.

Abstract: In this paper, gelatin-based films were prepared by mixing gelatin with glycerol, and microbial transglutaminase (mTG) which was used as cross linking agent. The result of SEM confirmed that a dense network structure was formed after mTG treatment comparing to the native. The effect of mTG on water barrier property of films was investigated by measuring the water vapor permeability (WVP). The results showed that the concentration of gelatin has a significant influence on the water barrier property of gelatin-based film which was treated with mTG. The WVP value of the films decreased sharply after enzymatic cross-linking when gelatin concentration increased to 8%, while no evident change of the WVP can be found when the gelatin concentrations was lower than 8%.