scholarly journals Measurement of the dynamic moisture buffering potential of fabrics

2018 ◽  
Vol 89 (5) ◽  
pp. 739-747 ◽  
Author(s):  
Geoffrey RS Naylor
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Natural Fibers ◽  
Test Sample ◽  
Fiber Types ◽  
Fixed Temperature ◽  
New Approach ◽  
Synthetic Fibers ◽  
Wide Range ◽  
Moisture Buffering

In non-stationary wear conditions, characterized by intermittent pulses of moderate or heavy sweating, a garment with a good moisture buffering action can improve comfort. This is consistent with the common consumer belief that clothing manufactured from hygroscopic natural fibers (e.g., wool or cotton) provides better breathability. The current work describes a new approach for measuring dynamic moisture buffering potential using the sweating guarded hotplate instrument in a novel mode of operation. A fabric test sample is placed on the hotplate following the normal procedure for dry mode testing but with the relative humidity of the surrounding environment set to a low value (45%). After equilibration, the relative humidity is rapidly increased to a high value (85%). In the case of hygroscopic samples, a transient reduction in the heat required to maintain the hotplate at its fixed temperature is observed. It is demonstrated that the area of this transient peak is a measure of the water vapor absorbed during this transition, that is, the moisture buffering potential of the test specimen. A key to this new approach is that the heat of sorption per gram of water vapor absorbed is approximately the same for a wide range of natural and synthetic fibers commonly used in clothing. Using matched knitted fabrics manufactured from wool, cotton or polyester, the technique detected the heat released from light weight fabrics and the performance of the different fiber types is clearly distinguished.

A modified resistance to compression (RtC) test for evaluation of natural fiber softness

2022 ◽  
pp. 004051752110694
Author(s):  
Hao Yu ◽  
Christopher Hurren ◽  
Xin Liu ◽  
Stuart Gordon ◽  
Xungai Wang
Keyword(s):  
Compression Test ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Assessment Method ◽  
Fiber Types ◽  
New Approach ◽  
Additional Information ◽  
Significant Difference ◽  
Single Force ◽  
Different Diameters

Comfort is a key feature of any clothing that relates significantly to softness of the fiber, yarn and fabric from which is it constructed. A known softness assessment method for fibers is the resistance to compression test. This traditional test only provides a single force value for the resistance of a loose fiber sample using a fixed mass under compression. In this research, a modified resistance to compression test was introduced to show the effects of repeated compression, providing more information about the softness and resilience of selected fibers. Three different natural fiber types, including wool, cotton and alpaca were compared using this new approach. The results showed compression profiles were quite different for different fiber types as well as for the same fibers with different diameters. While the diameters of the wool and alpaca samples were similar (18.5 μm), the modified resistance to compression values were significantly higher for wool (with a peak value at 9.5 kPa compared to 2.1 kPa for alpaca). Cotton was different from wool and alpaca but showed a similar modified resistance to compression value (10.4 kPa) to wool. During cycles of compression, modified resistance to compression peak values decreased slightly and then tended to be constant. Even though the structures of wool, cotton and alpaca were quite different, there was no significant difference in the magnitude of decline in modified resistance to compression peak values. This means that the modified resistance to compression test is able to provide additional information on the resilience characteristics of different natural fibers, and can reveal the resistance behavior of fiber samples during cyclic compression.

scholarly journals Hygrothermal and Mechanical Behaviors of Fiber Mortar: Comparative Study between Palm and Hemp Fibers

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7110
Author(s):  
Younes Zouaoui ◽  
Ferhat Benmahiddine ◽  
Ammar Yahia ◽  
Rafik Belarbi
Keyword(s):  
Natural Fibers ◽  
Fiber Types ◽  
High Porosity ◽  
Environmental Footprint ◽  
Good Efficiency ◽  
Hemp Fibers ◽  
Buffer Value ◽  
Hydrophilic Character ◽  
Moisture Buffering ◽  
Very High

This paper presents an experimental investigation of the hygrothermal and mechanical properties of innovative mortar mixtures reinforced with natural fibers. Fibers extracted from palm stems (PS) and hemp (HF) were evaluated at different percentages. Scanning electron microscope (SEM) observations showed that the PS fibers have rough surfaces and very complex microstructures. Prior to their incorporation into the mortar, the fibers were subjected to different treatments to reduce their hydrophilic character. The employed treatments showed good efficiency in reducing the water absorption of both PS and HF fiber types. Furthermore, the mortar mixtures incorporating these fibers exhibited low thermal conductivity and excellent moisture buffering capacity. Indeed, the moisture buffer value (MBV) of the investigated mixtures ranged between 2.7 [g/(%HR·m2)] and 3.1 [g/(%HR·m2)], hence providing them excellent moisture regulator character. As expected, the fiber mortar mixtures showed very high porosity and low compressive strength ranging between 0.6 and 0.9 MPa after 28 days of age. The low-environmental footprint materials developed in this study are intended for thermal insulation and building filling.

scholarly journals Robust and precise identification of the hygro-expansion of single fibers: a full-field fiber topography correlation approach

Cellulose ◽  
2020 ◽  
Vol 27 (12) ◽  
pp. 6777-6792
Author(s):  
N. H. Vonk ◽  
N. A. M. Verschuur ◽  
R. H. J. Peerlings ◽  
M. G. D. Geers ◽  
J. P. M. Hoefnagels
Keyword(s):  
Relative Humidity ◽  
Low Cost ◽  
Natural Fibers ◽  
Three Dimensional ◽  
Surface Displacement ◽  
Fiber Surface ◽  
Surface Strain ◽  
Full Field ◽  
Hygroscopic Properties ◽  
Wide Range

Abstract Over the past decades, natural fibers have become an important constituent in multiple engineering- and biomaterials. Their high specific strength, biodegradability, low-cost production, recycle-ability, vast availability and easy processing make them interesting for many applications. However, fiber swelling due to moisture uptake poses a key challenge, as it significantly affects the geometric stability and mechanical properties. To characterize the hygro-mechanical behavior of fibers in detail, a novel micromechanical characterization method is proposed which allows continuous full-field fiber surface displacement measurements during wetting and drying. A single fiber is tested under an optical height microscope inside a climate chamber wherein the relative humidity is changed to capture the fiber swelling behavior. These fiber topographies are, subsequently, analyzed with an advanced Global Digital Height Correlation methodology dedicated to extract the full three-dimensional fiber surface displacement field. The proposed method is validated on four different fibers: flat viscose, trilobal viscose, 3D-printed hydrogel and eucalyptus, each having different challenges regarding their geometrical and hygroscopic properties. It is demonstrated that the proposed method is highly robust in capturing the full-field fiber kinematics. A precision analysis shows that, for eucalyptus, at 90% relative humidity, an absolute surface strain precision in the longitudinal and transverse directions of, respectively, 1.2 × 10-4 and 7 × 10-4 is achieved, which is significantly better than existing techniques in the literature. The maximum absolute precision in both directions for the other three tested fibers is even better, demonstrating that this method is versatile for precise measurements of the hygro-expansion of a wide range of fibers. Graphic abstract

scholarly journals Review of Hybrid Fiber Based Composites with Nano Particles—Material Properties and Applications

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2088 ◽  
Author(s):  
Ayyappa Atmakuri ◽  
Arvydas Palevicius ◽  
Andrius Vilkauskas ◽  
Giedrius Janusas
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Material Properties ◽  
Chemical Treatment ◽  
Hybrid Composites ◽  
Natural Fibers ◽  
Nano Particles ◽  
Synthetic Fibers ◽  
Wide Range ◽  
Natural And Synthetic

The present review article provides an overview of the properties of various natural and synthetic fibers for the fabrication of pure natural composites and the combination of both natural/synthetic fibers-based hybrid composites, bio-based resins, various fabrication techniques, chemical and mechanical properties of fibers, the effect of chemical treatment and the influence of nanoparticles on the composite materials. Natural fibers are becoming more popular and attractive to researchers, with satisfactory results, due to their availability, ease of fabrication, cost-effectiveness, biodegradable nature and being environmentally friendly. Hybrid composites made up of two different natural fibers under the same matrix material are more popular than a combination of natural and synthetic fibers. Recent studies relevant to natural fiber hybrid composites have stated that, due to their biodegradability and the strength of individual fibers causing an impact on mechanical properties, flame retardancy and moisture absorption, natural fibers need an additional treatment like chemical treatment for the fibers to overcome those drawbacks and to enhance their better properties. The result of chemical treatment on composite material properties such as thermal, mechanical and moisture properties was studied. Researchers found that the positive influence on overall strength by placing the filler materials (nanoparticles) in the composite materials. Hybrid composites are one of the fields in polymer science that are attracting consideration for various lightweight applications in a wide range of industries such as automobile, construction, shipping, aviation, sports equipment, electronics, hardware and biomedical sectors.

Mass transfer of water vapor, carbon dioxide and oxygen on modified cellulose fiber-based materials

2012 ◽  
Vol 27 (2) ◽  
pp. 409-417 ◽  
Author(s):  
Alemayehu H. Bedane ◽  
Qinglin Huang ◽  
Huining Xiao ◽  
Mladen
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Water Vapor ◽  
Relative Humidity ◽  
Transmission Rate ◽  
The Other ◽  
Paper Sample ◽  
Coated Paper ◽  
Wide Range ◽  
Transfer Properties

Abstract Mass transfer properties of fibre network and coated paper are essential for understanding the barrier properties of the products and further advance in their application. In this study, different unmodified and coated papers, e.g., (Poly lactic acid (PLA), zein grafted paper) were prepared and characterized with regard to mass transfer properties. Water vapor, carbon dioxide (CO2) and oxygen (O2) transmission rates through the cellulose paper films were measured and the results discussed. The effects of sample film thickness and samples were found to be strongly dependent on the temperature and the relative humidity difference (mass transfer driving force). On the other hand water vapor permeabilities relative humidity. Water vapor diffusivities of the samples were also measured from the uptake rate measurements using Fickian diffusion slab model for a wide range of relative modified samples were found to be generally low compared to unmodified (reference) paper sample. Among the investigated samples, PLA/polyhedral oligomeric silsesquioxane POSS-bentonite modified paper sample showed higher mass transfer resistance to water vapour and the gases investigated in this study (CO2and O2). It showed lower water transmission rate (104 g/m2.day) compared to PLA-coated paper (130 g/m2.day), zein coated paper (179 g/m2.day) and control sample (359 g/m2.day) at the relative humidity gradient RH=74% and temperature of 25 oC. The oxygen transmission rate for PLA/(POSS-Bentonite) coated paper was found to be lower than for the other modified papers. Zein grafted paper showed better barrier property for water vapor than oxygen. Water vapor permeation through paper films shows an Arrhenius type of dependency with temperature, indicating activated process. The activation energies reveal diffusion dominated process for all paper samples investigated in this study, according to the solution-diffusion mechanism used to describe the permeation processes.

scholarly journals Water Vapor Sorption and Diffusivity in Bio-Based Poly(ethylene vanillate)—PEV

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 524
Author(s):  
Greta Giacobazzi ◽  
Claudio Gioia ◽  
Micaela Vannini ◽  
Paola Marchese ◽  
Valérie Guillard ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Sorption Isotherms ◽  
Sorption Process ◽  
Water Vapor Sorption ◽  
Gravimetric Analysis ◽  
Vapor Sorption ◽  
Wide Range ◽  
Poly Ethylene ◽  
Segmental Flexibility

The dynamic and equilibrium water vapor sorption properties of amorphous and highly crystalline poly(ethylene vanillate) (PEV) films were determined via gravimetric analysis, at 20 °C, over a wide range of relative humidity (0–95% RH). At low RH%, the dynamic of the sorption process obeys Fick’s law while at higher relative humidity it is characterized by a drift ascribable to non-Fickian relaxations. The non-Fickian relaxations, which are responsible for the incorporation of additional water, are correlated with the upturn of the sorption isotherms and simultaneously the hysteresis recorded between sorption and desorption cycles. The sorption isotherms of amorphous and highly crystalline PEV are arranged in the same concentration range of that of PET proving the similarity of the two polyesters. Water diffusion coefficients, whose determination from individual kinetic sorption/desorption curves required treatment with the Barens–Hopfenberg model, were demonstrated to be ≈10× higher for amorphous PEV compared to amorphous PET. Such a difference originates from the enhanced segmental flexibility of PEV chains.

Factors Affecting Molecular Self-Assembly and Its Mechanism

2012 ◽  
Vol 9 (1) ◽  
pp. 43 ◽  
Author(s):  
Hueyling Tan
Keyword(s):  
Self Assembly ◽  
Building Blocks ◽  
Molecular Engineering ◽  
Molecular Structures ◽  
Polymer Science ◽  
New Approach ◽  
Factors Affecting ◽  
Dna Structures ◽  
Self Assembling ◽  
Wide Range

Molecular self-assembly is ubiquitous in nature and has emerged as a new approach to produce new materials in chemistry, engineering, nanotechnology, polymer science and materials. Molecular self-assembly has been attracting increasing interest from the scientific community in recent years due to its importance in understanding biology and a variety of diseases at the molecular level. In the last few years, considerable advances have been made in the use ofpeptides as building blocks to produce biological materials for wide range of applications, including fabricating novel supra-molecular structures and scaffolding for tissue repair. The study ofbiological self-assembly systems represents a significant advancement in molecular engineering and is a rapidly growing scientific and engineering field that crosses the boundaries ofexisting disciplines. Many self-assembling systems are rangefrom bi- andtri-block copolymers to DNA structures as well as simple and complex proteins andpeptides. The ultimate goal is to harness molecular self-assembly such that design andcontrol ofbottom-up processes is achieved thereby enabling exploitation of structures developed at the meso- and macro-scopic scale for the purposes oflife and non-life science applications. Such aspirations can be achievedthrough understanding thefundamental principles behind the selforganisation and self-synthesis processes exhibited by biological systems.

Extraction of DNA from a Wide Range of Objects by Treatment with Ammonium Salts

2020 ◽  
Vol 36 (6) ◽  
pp. 98-106
Author(s):  
E.I. Levitin ◽  
B.V. Sviridov ◽  
O.V. Piksasova ◽  
T.E. Shustikova
Keyword(s):  
Dna Extraction ◽  
Dna Isolation ◽  
Tissue Samples ◽  
New Approach ◽  
Cell Wall Disruption ◽  
Wide Range ◽  
Low Salt ◽  
Mammalian Blood ◽  
Plasmid Extraction ◽  
Two Hybrid

Currently, simple, rapid, and efficient techniques for DNA isolation from a wide range of organisms are in demand in biotechnology and bioinformatics. A key (and often limiting) step is the cell wall disruption and subsequent DNA extraction from the disintegrated cells. We have developed a new approach to DNA isolation from organisms with robust cell walls. The protocol includes the following steps: treatment of cells or tissue samples with ammonium acetate followed by cell lysis in low-salt buffer with the addition of SDS. Further DNA extraction is carried out according to standard methods. This approach is efficient for high-molecular native DNA isolation from bacteria, ascomycetes, yeast, and mammalian blood; it is also useful for express analysis of environmental microbial isolates and for plasmid extraction for two-hybrid library screening. express method for DNA isolation; ammonium salt treatment (в русских ключевых такой порядок), osmotic breakage of cells This study was financially supported by the NRC "Kurchatov Institute"-GOSNIIGENETIKA Kurchatov Genomic Center.

PU composites based on different types of textile fibers

2021 ◽  
pp. 002199832110316
Author(s):  
Nuno Gama ◽  
B Godinho ◽  
Ana Barros-Timmons ◽  
Artur Ferreira
Keyword(s):  
Thermal Conductivity ◽  
Raw Materials ◽  
Natural Fibers ◽  
Tensile Modulus ◽  
High Water ◽  
Textile Fibers ◽  
Synthetic Fibers ◽  
Hydrophilic Nature ◽  
Different Types ◽  
Recycled Composites

In this study polyurethane (PU) residues were mixed with residues of textile fibers (cotton, wool and synthetic fibers up to 70 wt/wt) to produce 100% recycled composites. In addition, the effect of the type of fiber on the performance of the ensuing composites was evaluated. The presence of fibers showed similar effect on the density, reducing the density in the 5.5-9.0% range. In a similar manner, the addition of fillers decreased their thermal conductivity. The 70 wt/wt wool composite presented 38.1% lower thermal conductivity when compared to the neat matrix, a reduction that was similar for the other type of fibers. Moreover, the presence of fillers yields stiffer materials, especially in the case of the Wool based composites, which with 70 wt/wt of filler content increased the tensile modulus of the ensuing material 3.4 times. This was attributed to the aspect ratio and stiffness of this type of fiber. Finally, the high-water absorption and lower thermal stability observed, especially in the case of the natural fibers, was associated with the hydrophilic nature of fibers and porosity of composites. Overall, the results suggest that these textile-based composites are suitable for construction and automotive applications, with the advantage of being produced from 100% recycled raw-materials, without compromised performance.

scholarly journals HGPT2: An ERA5-Based Global Model to Estimate Relative Humidity

2021 ◽  
Vol 13 (11) ◽  
pp. 2179
Author(s):  
Pedro Mateus ◽  
Virgílio B. Mendes ◽  
Sandra M. Plecha
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Real Time ◽  
Prediction Models ◽  
Weather Prediction ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Global Navigation Satellite Systems ◽  
International Gnss Service ◽  
Weighted Mean Temperature

The neutral atmospheric delay is one of the major error sources in Space Geodesy techniques such as Global Navigation Satellite Systems (GNSS), and its modeling for high accuracy applications can be challenging. Improving the modeling of the atmospheric delays (hydrostatic and non-hydrostatic) also leads to a more accurate and precise precipitable water vapor estimation (PWV), mostly in real-time applications, where models play an important role, since numerical weather prediction models cannot be used for real-time processing or forecasting. This study developed an improved version of the Hourly Global Pressure and Temperature (HGPT) model, the HGPT2. It is based on 20 years of ERA5 reanalysis data at full spatial (0.25° × 0.25°) and temporal resolution (1-h). Apart from surface air temperature, surface pressure, zenith hydrostatic delay, and weighted mean temperature, the updated model also provides information regarding the relative humidity, zenith non-hydrostatic delay, and precipitable water vapor. The HGPT2 is based on the time-segmentation concept and uses the annual, semi-annual, and quarterly periodicities to calculate the relative humidity anywhere on the Earth’s surface. Data from 282 moisture sensors located close to GNSS stations during 1 year (2020) were used to assess the model coefficients. The HGPT2 meteorological parameters were used to process 35 GNSS sites belonging to the International GNSS Service (IGS) using the GAMIT/GLOBK software package. Results show a decreased root-mean-square error (RMSE) and bias values relative to the most used zenith delay models, with a significant impact on the height component. The HGPT2 was developed to be applied in the most diverse areas that can significantly benefit from an ERA5 full-resolution model.

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