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Nonwoven fabrics are widely used for thermal insulation and sound absorption purpose in construction and automobile fields. It is essential to investigate their thermal conductivity and sound absorption coefficient. Five cross-laid nonwoven fabrics are measured on the Alambeta device and Brüel & Kjær impedance tube. Bogaty and Bhattacharyya models are selected to predict the thermal conductivity, and Voronina and Miki models are used to predict the sound absorption coefficient. The predicted thermal conductivity shows a significant difference compared with the measured values. It is concluded that Bogaty and Bhattacharyya models are not suitable for high porous nonwoven fabric. In addition, the results of Voronina and Miki models for sound absorption prediction are acceptable, but Voronina model shows lower mean prediction error compared with Miki model. The results indicate that Voronina model can be used to predict the sound absorption of cross-laid nonwoven fabric.

Thermal performance of aerogel-embedded polyester/polyethylene nonwoven fabrics in cross airflow was experimentally studied by using a laboratory-built dynamic heat transfer measuring device in which the fabric could be applied on a heating rod. Experiments were performed with different airflow velocities and heating conditions. The temperature–time histories of different materials were collected and compared. The temperature difference and convective heat transfer coefficient under continuous heating were analyzed and discussed. Results showed that under preheated conditions, the aerogel-embedded nonwoven fabrics had very small decrease in temperature and good ability to prevent against heat loss in cross flow. As for the continuous heating conditions, the heat transfer rate of each material showed an increasing trend with increase in the Reynolds number. The aerogel-treated nonwoven fabric with the least fabric thickness and aerogel content delivered a significantly increased heat transfer rate at higher Reynolds number. Thicker fabrics with higher aerogel content could provide better insulation ability in cross flow.

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Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nonwoven fabrics are widely used for thermal insulation and sound absorption purpose in construction and automobile fields. It is essential to investigate their thermal conductivity and sound absorption coefficient. Five cross-laid nonwoven fabrics are measured on the Alambeta device and Brüel & Kjær impedance tube. Bogaty and Bhattacharyya models are selected to predict the thermal conductivity, and Voronina and Miki models are used to predict the sound absorption coefficient. The predicted thermal conductivity shows a significant difference compared with the measured values. It is concluded that Bogaty and Bhattacharyya models are not suitable for high porous nonwoven fabric. In addition, the results of Voronina and Miki models for sound absorption prediction are acceptable, but Voronina model shows lower mean prediction error compared with Miki model. The results indicate that Voronina model can be used to predict the sound absorption of cross-laid nonwoven fabric. [ABSTRACT FROM AUTHOR]

Particulate matter 2.5 (PM 2.5.) pollution is a serious threat to human health. In this paper, we firstly used electrospraying technology to fabricate composite polytetrafluoroethylene (PTFE)/expanded graphite (EG) coated spun‐bond polypropylene (PP) microporous filters that show tremendous potential for its use as an effective PM 2.5. capture medium. The surface morphology, the surface area, the surficial chemical structure, the hydrophobicity, the antifouling ability, the mechanical property, the air permeability, and the filtration efficiency (FE) of the prepared composite PTFE/EG coated microporous filters were investigated. It is found that with the increase of EG content, the surface area of the filter tended to increase, and the pore size decreased correspondingly. Physical adhesion between the PTFE or PTFE/EG and the PP fabric is found. The composite PTFE/EG coated spun‐bond PP microporous filter exhibits an excellent hydrophobicity and antifouling ability. Compared with the original spun bond PP, the FE of the composite PTFE/EG coated spun bond PP microporous filter for PM 2.5. is significantly increased from 52.18% to 85.00%, and the quality factor (QF) increases from 0.0238 to 0.0431. These results indicate that the composite PTFE/EG coated spun‐bond PP microporous filter is an excellent material for PM 2.5. capture. [ABSTRACT FROM AUTHOR]

Air penetration behavior plays a vital role in the performance of fibrous material in various industrial applications. Two parameters, the permeability coefficient and airflow resistivity, can describe the air penetration behavior of fibrous material. FX 3300 Textech Tester III and AFD300 AcoustiFlow devices were used to respectively characterize the permeability coefficient and airflow resistivity of nonwoven materials. Nonwoven samples were compressed due to the load from the test head of the FX 3300. Finite element analysis along with the mathematical method were implemented to recover the airflow permeability of samples at the uncompressed state. The effects of pressure drop on the airflow velocity and permeability coefficient were analyzed by the Ergun-type model. The determination of airflow resistivity based on the permeability coefficient is carried out via two approaches, that is, the direct method and the extrapolation method. The results show that the airflow velocity is not linearly related to the pressure drop, which differs from Darcy's law. This non-linear relation is mainly attributed to the influence of frictional loss. By comparing the relative error between assessed and measured airflow resistivity, most of the assessed values of the compressed samples are overestimated. The results also suggest that the direct and extrapolation methods are applicable to assess airflow resistivity on an airflow velocity (or air permeability) test device. Moreover, the Ergun-type model is also applicable to determine the permeability coefficient and airflow resistivity of nonwoven materials. [ABSTRACT FROM AUTHOR]

In this work, three types of multi-layered fibrous materials with different middle layer structures, including Struto nonwoven, Struto nonwoven with air pockets and Struto nonwoven with air pockets filled by aerogel particles, were prepared based on laser engraving technique and laminating method. A custom-built new device was fabricated to evaluate convective thermal behaviour of the multi-layered materials in cross flow. It was found that in cross flow the heat transfer coefficient of the multi-layered material with encapsulated aerogels is directly proportional to Reynolds number. There are considerable variances in heat transfer rates of the three structures at low airflow velocity (less than 10 m/s), but the values are very close at high airflow velocity. It is concluded that the air pockets and aerogels present in the multi-layered fibrous material have significant effect on convective thermal behaviour of the overall structure in cross flow. The finding is a new contribution to the field of aerogel-based fibrous materials as thermal insulators in building and industrial facilities. [ABSTRACT FROM AUTHOR]

This study presents an investigation of the acoustical properties of multi-component polyester nonwovens with experimental and numerical methods. Fifteen types of nonwoven samples made with staple, hollow and bi-component polyester fibers were chosen to carry out this study. The AFD300 AcoustiFlow device was employed to measure airflow resistivity. Several models were grouped in theoretical and empirical model categories and used to predict the airflow resistivity. A simple empirical model based on fiber diameter and fabric bulk density was obtained through the power-fitting method. The difference between measured and predicted airflow resistivity was analyzed. The surface impedance and sound absorption coefficient were determined by using a 45 mm Materiacustica impedance tube. Some widely used impedance models were used to predict the acoustical properties. A comparison between measured and predicted values was carried out to determine the most accurate model for multi-component polyester nonwovens. The results show that one of the Tarnow model provides the closest prediction to the measured value, with an error of 12%. The proposed power-fitted empirical model exhibits a very small error of 6.8%. It is shown that the Delany–Bazley and Miki models can accurately predict surface impedance of multi-component polyester nonwovens, but the Komatsu model is less accurate, especially at the low-frequency range. The results indicate that the Miki model is the most accurate method to predict the sound absorption coefficient, with a mean error of 8.39%. [ABSTRACT FROM AUTHOR]

This study presents an investigation into the sound absorption behavior and compression properties of perpendicular-laid nonwovens. Seven types of perpendicular-laid nonwovens produced by vibrating and rotating perpendicular lappers were selected. Nonwovens with varying thickness and areal density were prepared by the heat-pressing method to investigate the effect of structural parameters such as thickness and areal density on sound absorption ability. Measurements of sound absorption properties were carried out with a Brüel and Kjær measuring instrument. The effect of manufacturing techniques on sound absorption performance and compression properties was investigated. The effect of porosity on sound absorption ability was studied. The influence of density and fiber orientation angle on compression properties was analyzed. The results show that samples prepared by vibrating perpendicular lapper exhibit better compression properties, whereas there is no significant influence of two manufacturing techniques on sound absorption performance. The increase of areal density results in improvement in the sound absorption ability. The increase of thickness can improve the sound absorption coefficient in the low-frequency range, but decrease of the coefficient occurred in the high-frequency range. A quadratic relationship between porosity and sound absorption ability has been found. The results also show that compressional resistance has a strong relation with density – the correlation coefficient is 0.95, indicating that the compressional resistance is directly proportional to the density of perpendicular-laid nonwovens. The results indicate that the perpendicular-laid nonwovens with higher initial fiber orientation angle have better compression properties. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on sound absorption performance of aerogel/polymer nonwoven fabrics. Polyester/polyethylene nonwovens embedded with hydrophobic amorphous silica aerogel were chosen for sound absorption measurements. The sound absorption coefficient (SAC) of single and laminated layers of aerogel nonwovens blankets was tested by Brüel and Kjær impedance tube, the noise reduction coefficient (NRC) was used for numerical analysis. A sound absorption index was developed to analyze the effect of aerogel content on sound absorption ability. The effect of air-back cavities on SAC of single-layer aerogel/polymer nonwoven fabrics was investigated. The results show that there is a decrease in SAC with the increase of aerogel content. It is observed that the NRC linearly increased with the increase of layers for all the samples. It was also found that the air-back cavities result in resonance phenomenon, as the increase in thickness of air-back cavities the peak values of SAC shift toward lower frequencies. [ABSTRACT FROM AUTHOR]

In this work, a new approach to apply silica aerogel into textiles by laser treatment and laminating technique was used to fabricate aerogel-encapsulated textiles. Thermal insulation performance of the prepared multilayer aerogel-encapsulated laminated fabrics was characterized in terms of thermal conductivity, thermal resistance and thermal diffusivity by Alambeta instrument. Infrared thermography data were collected by FLIR ThermaCAM TVS300 thermal camera. The ORIENTEC STA-1225 Universal Testing Machine was employed for testing the compression properties like compression resistance, compression resilience and thickness loss. Results showed that the aerogel-encapsulated structure has significant effect on thermal insulation enhancement. A temperature gap of 1℃ to 1.5℃ was observed between aerogel-filled samples and regular ones. It is also found that nonwoven fabrics with aerogel-filled voids generally have lower compression resistance than regular nonwovens, samples with air-filled voids and aerogel-filled voids are observed to recover compression to a lower extent than regular samples. Nonwoven based aerogel-encapsulated composites exhibit lower thickness loss in comparison with untreated composites. The findings in this study can be used for further research in aerogel-encapsulated composites. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on the sound absorption behavior and thermal properties of Struto nonwovens by establishing relationship between these properties. Seven Struto nonwoven fabrics were selected to examine the noise reduction coefficient (NRC) and average values of sound absorption coefficients (α¯) as well as thermal properties, including thermal conductivity and thermal resistance. The Brüel and Kjær impedance tube instrument and Alambeta were used for the evaluation of acoustic and thermal properties, respectively. The influence of structural parameters on acoustic and thermal properties of Struto nonwovens were investigated and analyzed. The results showed that Struto nonwovens with higher thickness, finer fibers and higher fabric grams per square meter can provide better sound absorption performance. The effect of specific airflow resistance on sound absorption performance was also investigated. It is observed that sound absorption performance has a strong correlation with specific airflow resistance. The effect of porosity on specific airflow resistance and thermal properties was studied in detail. The result indicated that porosity has a strong correlation with specific airflow resistance and thermal properties. It was also observed that sound absorption, the NRC and α¯ have an insignificant correlation with thermal conductivity, while they are strongly correlated with thermal resistance. The correlation coefficient of the NRC with thermal resistance is 0.9835, indicating that the NRC is directly proportional to the thermal resistance of Struto nonwovens. [ABSTRACT FROM AUTHOR]

This paper presents the preparation of aerogel/polytetrafluoroethylene (PTFE) microporous materials via needleless electrospray technique, by using an aqueous dispersion of polytetrafluoroethylene as the basic spinning liquid. Different contents of aerogel powders were applied to the spinning liquid for electrospraying to investigate the effect on the structural characteristics and various properties of the materials. Cross-section, surface morphology, and particle size distribution of the electrosprayed materials were examined. Surface roughness, hydrophobicity, and thermal conductivity were evaluated and discussed. The results showed that the electrosprayed aerogel/PTFE layers were compact and disordered stacking structures composed of spherical particles with a rough surface. As the aerogel content increased, the electrosprayed materials demonstrated increased surface roughness and improved surface hydrophobicity with a contact angle up to 147.88°. In addition, the successful achievement of thermal conductivity as low as 0.024 (W m−1 K−1) indicated a superior ability of the prepared aerogel/PTFE composites to prevent heat transfer. This study contributes to the field of development of aerogel/PTFE composites via electrospray technique, providing enhanced final performance for potential use as thermal and moisture barriers in textiles or electronic devices. [ABSTRACT FROM AUTHOR]

AbstractObjectiveMethodsResultsConclusionsTo investigate the role of 14-3-3β in acute asthma exacerbations in children and analyze the risk factors for asthma exacerbations.This study recruited 101 children with acute asthma exacerbations, 101 children with stable asthma, and 65 healthy children. Serum 14-3-3β was compared among the three groups. Factors such as asthma family history, skin prick test, serum-specific IgE test, coinfections, and clinical indicators (FeNO, FEV1, white blood cells, eosinophils, and serum IgE level) were compared between the asthma groups. Risk factors associated with acute asthma exacerbations were identified using multivariate logistic regression models. ROC curve was drawn to determine the diagnostic sensitivity and specificity of 14-3-3β.Serum 14-3-3β was significantly greater in the acute asthma group than in the stable asthma and control groups. Serum 14-3-3β was higher in severe acute asthma group than in mild-moderate asthma group. There were no significant differences in serum 14-3-3β levels between stable asthma and control groups (p > .05). Multivariate logistic regression analysis revealed that serum 14-3-3β level, FeNO, coinfection, and FEV1 z-score significantly increased the odds of acute asthma exacerbations in children. The optimal 14-3-3β cutoff value (39.79 ng/mL), had a sensitivity of 69.3% and specificity of 94.1% for predicting acute asthma exacerbations.14-3-3β is elevated in children with acute exacerbations of asthma, and increases with exacerbation severity. 14-3-3β, FeNO, FEV1, and coinfection could be independent risk factors for predicting asthma exacerbations. The optimal 14-3-3β cutoff value for predicting asthma exacerbations was 39.79 ng/mL. [ABSTRACT FROM AUTHOR]