Screen-printing of microfibrillated cellulose for an improved moisture management, strength and abrasion resistant properties of flame-resistant fabrics

Low moisture absorbency of hydrophobically coated flame-resistant (FR) fabrics do not correlate well with the thermophysiological comfort. In this frame, we were the first to study the effect of screen-printed microfibrillated cellulose (MFC) on fabric’s breathability and moisture build-up and transfer as user-friendly and wear-related comfortable coating. The amount of MFC applied and its patterning was varied using different printing parameters, the density and thickness of FR fabric, and studied by add-on measurement and microscopic imaging. The effect of MFC coating and its durability (attachment) after a post-printing of hydrophobic polyacrylate on the same (layer-by-layer) or other side of the fabrics was considered, thus to maintain one side of the fabric (facing towards the wearer) hydrophilic while keeping the other side (facing outward) hydrophobic. The results showed that MFC provides uniform and repeatable printing, which gave homogeneous patterning with good layering on the fabrics, although, resulting in the MFC concentration, squeegee’ pressure, and fabric’ structure dependent add-on, its imprinting and co-crosslinking within the polyacrylate. This slightly reduced the fabric air-permeability, but increased it surfaces wetting, moisture uptake kinetic and capacity (hydroscopicity), without affecting the water vapour transfer. Besides, the polyacrylate could fix the MFC pre-printed on the other side of the fabric, thus maintaining its hydrophilicity, being more pronounced in the case of less open and thicker fabric, while improving its tensile/tear strengths and abrasion resistance, without deterioration of the fabric`s flammability.

Screen-printing of microfibrillated cellulose for an improved moisture management, strength and abrasion resistant properties of flame-resistant fabrics

Low moisture absorbency of hydrophobically coated flame-resistant (FR) fabrics do not correlate well with the thermophysiological comfort. In this frame, we were the first to study the effect of screen-printed microfibrillated cellulose (MFC) on fabric’s breathability and moisture build-up and transfer as user-friendly and wear-related comfortable coating. The amount of MFC applied and its patterning was varied using different printing parameters, and the density and thickness of FR fabric, and studied by add-on measurement and microscopic imaging. The effect of MFC coating and its durability (attachment) after a post-printing of hydrophobic polyacrylate on the same (layer-by-layer) or other side of the fabrics was considered, thus to maintain one side of the fabric (facing towards the wearer) hydrophilic while keeping the other side (facing outward) hydrophobic. The results showed that MFC provides uniform and repeatable printing, which gave homogeneous patterning with good layering on the fabrics, although, resulting in the MFC concentration, squeegee’ pressure, and fabric’ structure dependent add-on, its imprinting and co-crosslinking within the polyacrylate. This slightly reduced the fabric air-permeability, but increased it surfaces wetting, moisture uptake kinetic and capacity (hydroscopicity), without affecting the water vapour transfer. Besides, the polyacrylate could fix the MFC pre-printed on the other side of the fabric, thus maintaining its hydrophilicity, being more pronounced in the case of less open and thicker fabric, while improving its tensile /tear strengths and abrasion resistance, without deterioration of the fabric`s flammability.

The effects of elastane and finishing properties on wicking, drying and water vapour permeability properties of denim fabrics

Purpose The liquid water and water vapour transfer properties of fabrics play an important and decisive role in determining thermal comfort properties of clothing systems. The purpose of this paper is to analyse the effects of fabric composition (98 percent cotton–2 percent elastane and 100 percent cotton) and finishing treatments (rigid, resin, bleaching and softening) on the wicking, drying and water vapour permeability (WVP) properties of denim fabrics. Design/methodology/approach The research design for this study consists of experimental study. Two fabric compositions (98 percent cotton–2 percent elastane and 100 percent cotton) and four finishing treatments (rigid, resin, bleaching and softening) were evaluated to see the effects of elastane and finishing treatments on wicking, drying and WVP properties of woven denim fabrics. Results were analysed statistically. Findings Experimental results showed that the transfer wicking, drying and WVP values of denim fabrics were significantly influenced by fabric weight, fibre composition and finishing treatments. Practical implications The wicking ability of sweat from the skin to the outer environment of a skin contact fabric layer is the primary requirement. Originality/value As a result of the literature review, it was seen that there are some studies in the literature about comfort properties of denim fabrics, but there is no study concerning the water vapour transmission, wicking and drying properties of denim fabrics.

Hygric properties of hydrophobized building materials

Moisture loads due to wind-driven rain can lead to accelerated decay of exposed building facades. Hydrophobic impregnation reduces water absorption of facade materials and is thus presumed to decrease moisture related damages. Hydrophobic impregnation however also lowers the drying speed of the exposed facade, leaving mainly water vapour transfer to take place. This study examines the open porosity and capillary absorption coefficient of impregnated brick samples as well as the effect of hydrophobic impregnation on the vapour permeability of brick and mortar samples. The open porosity was measured with vacuum saturation test, the absorption coefficient was determined by water uptake tests, both done after one month of curing of the impregnated brick samples. The vapour permeability was `derived from cup tests and from drying tests. The resulting open porosity from brick samples indicates that the changes in the overall pore structure are minimal after impregnation. In addition, the absorption coefficient of brick was found to be fairly close to zero, even with low concentrations of active ingredient, and regardless the percentage of silane/siloxane. Our findings support the claim that the hydrophobic impregnation does not influence significantly the water vapour permeability of brick and mortar.

DEVELOPMENT AND INVESTIGATION OF THERMAL INSULATION FROM HEMP-POLYLACTIDE FIBRES

In the last two decades intensive grow of industry of building materials from renewable resources is observed. Such situation is related to some aspects: global warming, environmental pollution, impact on human health, environmental impact of materials at their end-of-life. In current study development of thermal insulation materials from hemp and polylactide fibres are analysed. While main parameter for thermal insulation materials is thermal conductivity, rational density of composite 40 kg/m3 was chosen. For experiments 11 compositions were prepared. One composition was prepared just with hemp and polylactide fibres, five compositions with different amount of hydrophobic agent and 5 compositions with different amount of fire retardant. Experimentally thermal conductivity, sound absorption coefficient, short-term water absorption, fire resistance, water vapour transfer properties and compressive strength were determined. Rational amount of hydrophobic agent and fire retardants was chosen.

Testing New Water Repellent Solutions to Protect Deteriorated Granite

The evaluation of nano-particle based products to protect granite surfaces from water absorption is presented. Wettability, water absorption, drying behaviour and water vapour transfer were considered as the most relevant parameters for this evaluation. The effect of the application methods on the final performance was also tested. The results allow to consider that nanostructured products may present some advantages when compared with conventional water repellent products, namely on some common relevant harmful effects, such as colour changes, water vapour or liquid transfer during drying, but their effectiveness as barriers against water absorption upon longer contact time may not be equally satisfactory.

Continuous stand-alone controllable aerosol/cloud droplet dryer for atmospheric sampling

We describe a general-purpose dryer designed for continuous sampling of atmospheric aerosol, where a specified relative humidity (RH) of the sample flow (lower than the atmospheric humidity) is required. It is often prescribed to measure the properties of dried aerosol, for instance for monitoring networks. The specific purpose of our dryer is to dry cloud droplets (maximum diameter approximately 25 μm, highly charged, up to 5 × 102 charges). One criterion is to minimise losses from the droplet size distribution entering the dryer as well as on the residual dry particle size distribution exiting the dryer. This is achieved by using a straight vertical downwards path from the aerosol inlet mounted above the dryer, and removing humidity to a dry, closed loop airflow on the other side of a semi-permeable GORE-TEX membrane (total area 0.134 m2). The water vapour transfer coefficient, k, was measured to be 4.6 × 10-7 kg m−2 s−1% RH−1 in the laboratory (temperature 294 K) and is used for design purposes. A net water vapour transfer rate of up to 1.2 × 10-6 kg s−1 was achieved in the field. This corresponds to drying a 5.7 L min−1 (0.35 m3 h−1) aerosol sample flow from 100% RH to 27% RH at 293 K (with a drying air total flow of 8.7 L min−1). The system was used outdoors from 9 May until 20 October 2010, on the mountain Brocken (51.80° N, 10.67° E, 1142 m a.s.l.) in the Harz region in central Germany. Sample air relative humidity of less than 30% was obtained 72% of the time period. The total availability of the measurement system was >94% during these five months.