Development and Evaluation of Experimental Nonwoven Breathable Barrier Fabrics

Fiber size, pore size, and air permeability are three important properties in melt blown (MB) webs. Air permeability governs the air resistance or the pressure drop of the air through the web. One of the major applications of MB webs is for air filters. Fiber size dominates the web air filtration efficiency. Liquid filtration is another major application of MB webs. Pore size of the web determines the rated particle size in liquid filtration. Air permeability can be easily determined by air permeability testers. Fiber size and pore size in MB webs are difficult to measure by optical microscopy or other methods. However, they can be determined in fibrous products from the air flow rate through the web.

The primary goal of this research was to determine optimum processing conditions to produce commercially acceptable melt blown (MB) thermoplastic polyurethane (TPU) non-woven fabrics. The 20-inch wide Accurate Products MB pilot line at the Textiles and Nonwovens Development Center (TANDEC), The University of Tennessee, Knoxville, was utilized for this study. MB TPU webs having small fiber diameters were obtained from film-forming and highly elastic fiber-forming TPUs and the webs were mechanically strong and durable to abrasion compared to MB PP. The basic MB process was found to be fundamentally valid for the MB TPU process; however, the MB process was more complicated for TPU than PP, because web structures and properties of MB TPUs are very sensitive to MB process conditions. Furthermore, different TPU polymers responded very differently to MB processing and exhibited different web structure and properties, although uniform elastic MB webs were produced with average fiber diameters as small as 5.0μm. Preliminary research leading to this study was funded the Army Research Office (ARO) and the findings were used by ARO towards the development of an elastic chemical protective liner with better overall comfort attributes and protection against chemical warfare agents.

Fluorinated compounds provide excellent oil and water repellency to cotton fabrics. But, they have various toxic effects on human health and the environment. To address this challenge, scientists are continuously struggling to develop the eco-friendly oil and water repellents. To support these efforts, this research focused on the synthesis of some bio-based and non-fluorinated oil and water repellent recipes for the cotton fabric through the polymerization of palmitic acid with an eco-friendly cross-linker “citric acid” considering the effects of catalyst, enhancer, time, temperature, and polymerization environment. After the numerous trials, an optimized water repellent finish has been developed. The performance of the cotton fabric treated with the newly developed water repellent was measured in terms of the oil and water repellency, crease recovery angle, contact angle, stain release, air permeability, shrinkage, washing durability, tensile strength, tear strength, and antimicrobial performance. Finally, the characterization of the optimized recipes and the treated fabric was performed through the various techniques such as H-NMR spectroscopy, scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The results exhibited the successful synthesis and application of the newly developed recipes onto the cotton fabric.

The Graduate Automotive Technology Education (GATE) Center at the University of Tennessee, Knoxville (UTK) offers courses addressing the simulation, modeling, and control system design of hybrid electric vehicles (HEV). In the Spring of 1999 such a course was conducted to support the UTK FutureCar Challenge entry for 1999. The vehicle modeled is a Dual-configuration Hybrid Electric Vehicle (DHEV) which uses a planetary power-split device similar to the Toyota Hybrid System used in the Toyota “Prius”. The goals of the course included the development of a real-time simulator that could incorporate actual vehicle control hardware in the simulator loop. This “control-hardware-in-the-loop” (CHIL) configuration was used for simulation, control system design, and troubleshooting. This approach allows the simulation of normal vehicle operating conditions as well as emergency fault handling situations in which it may not be desirable to subject the actual prototype vehicle to a given test condition. Additionally, it is possible to do a great deal of control system testing and development without an operating vehicle.

Fluoroalkyl acrylate (FA) polymers are widely used as fluorine-based water and oil repellents for various materials such as textiles, carpets and paper. Water repellency can also be achieved with silicone-based polymers and hydrocarbon polymers, but with FA polymers even higher resistance to water pressure, better oil repellency, and antifouling properties can be attained. For that reason, generally fluorine-based systems are currently employed as water and oil repellents. In recent years, extensive investigations and research have been carried out because of increasing concerns about the accumulation in the environment and the living body of perfluorooctanoic acid (PFOA) derived from fluorotelomers, which constitute the raw material for FA polymers. This chapter gives an overview of the PFOA issue and the production process of FA polymers, touching upon the relationship between the water-repellent performance of FA polymers and their structures. The future prospects of alternative technologies to produce environmentally friendly (short-chain type) fluorine-based water and oil repellents and PFOA-free products are discussed.

To clarify differences in air permeability of the hose cloth of different types of pantyhose on the market in Japan, cylindrical model experiments and wearing experiments were conducted. The former was made to determine fundamental performance of the air permeability, and the latter, to evaluate the practical performance of worn pantyhose. Zokki, kohhen, sheer, wooly, and conjugate types of pantyhose were used as samples. There were large differences in air permeability among these fabrics when elongation was low or moderate. In around the maximum elongation state, almost the same high air permeability was shown regardless of pantyhose types. There were some pantyhose with lower air permeability while being worn, or other ones which have higher air permeability, regardless of posture, body shape, and sites of legs.

Meltblown (MB) nonwovens as air filter materials have played an important role in protecting people from microbe infection in the COVID-19 pandemic. As the pandemic enters the third year in this current global event, it becomes more and more beneficial to develop more functional MB nonwovens with special surface selectivity as well as antibacterial activities. In this article, an antibacterial polypropylene MB nonwoven doped with nano silicon nitride (Si3N4), one of ceramic materials, was developed. With the introduction of Si3N4, both the average diameter of the fibers and the pore diameter and porosity of the nonwovens can be tailored. Moreover, the nonwovens having a single-side moisture transportation, which would be more comfortable in use for respirators or masks, was designed by imparting a hydrophobicity gradient through the single-side superhydrophobic finishing of reactive organic/inorganic silicon coprecipitation in situ. After a nano/micro structural SiO2 precipitation on one side of the fabric surfaces, the contact angles were up to 161.7° from 141.0° originally. The nonwovens were evaluated on antibacterial activity, the result of which indicated that they had a high antibacterial activity when the dosage of Si3N4 was 0.6 wt%. The bacteriostatic rate against E. coli and S. aureus was up to over 96%. Due to the nontoxicity and excellent antibacterial activity of Si3N4, this MB nonwovens are promising as a high-efficiency air filter material, particularly during the pandemic.

This report describes the tasks performed and the progress made during Phase 2 of the DOE-NERI project number 99-119 entitled Automatic Development of Highly Reliable Control Architecture for Future Nuclear Power Plants. This project is a collaboration effort between the Oak Ridge National Laboratory (ORNL), The University of Tennessee, Knoxville (UTK) and the North Carolina State University (NCSU). ORNL is the lead organization and is responsible for the coordination and integration of all work.

Alkali-Silica Reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, non-crystalline silica in aggregates. An expansive gel is formed within the aggregates which results in micro-cracks in aggregates and adjacent cement paste. The reaction requires the presence of water and has been predominantly detected in groundwater-impacted portions of below grade structures, with limited impact to exterior surfaces in above grade structures. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, shear strength, and tensile strength. Since ASR degradation often takes significant amounts of time, developing ASR detection techniques is important to the sustainability and extended operation lifetimes of nuclear power plants (NPPs). The University of Tennessee, Knoxville (UTK) in collaboration with Oak Ridge National Laboratory (ORNL) designed and built an experiment representative of typical NPP structures to study ASR in thick concrete structures.

Great durability problems are being found in concrete structures related to the penetrability of aggressive agents through the concrete (ie. chloride penetration, sulphate attack, carbonation, freezing and thawing, and so on). Air permeability coefficient is used as an effective tool to estimate the potential durability of concrete structures due to its direct relation with the microstructure and the moisture content. This paper discusses the effect of the aggregate grading and water/cement ratio on the air permeability coefficient. An aggregate grading with more sand than coarse aggregates has resulted more beneficial from the point of view of concrete air permeability. This fact can be attributed to a denser skeleton formed by the finer aggregates. With fine aggregates, the higher water/cement ratio, the lower air permeability. However, the contrary was found with coarse aggregates. Overall, a temperature increase from 20 °C to 60 °C during preconditioning led to a Dair increase of 40–80%.

Water and oil repellent coating on fabric using hollow cathode PECVD

Multilayer three-dimensional (3D) fabrics are gaining importance due to their unique properties, which are significantly influenced by the interlocking pattern and govern their end-use applications, particularly in protective textiles requiring higher through-the-thickness mechanical characteristics. This research focuses on developing 3D woven structures with novel orthogonal through-the-thickness interlocking patterns: warp interlocked (WP-IL), weft interlocked (WT-IL), and hybrid interlocked (HB-IL) by using warp and weft yarns simultaneously for interlocking fabric layers. Various performance characteristics, including air permeability, thermal conductivity, compression resistance, bending rigidity, tensile strength, and puncture resistance, were evaluated to assess the influence of fabric structure. Statistical analysis using One-way ANOVA was conducted to determine the significance of the interlocking pattern on these properties. The results indicate that weft interlock structures exhibit the highest air permeability due to their greater porosity, whereas hybrid interlock and warp interlock structures show 20.7% and 18% lower air permeability, respectively, due to their reduced structural porosity. Thermal conductivity results suggest no significant differences in insulation properties among the structures. Hybrid interlock fabrics demonstrate superior compression resistance and tensile strength, with 26.2% higher tensile strength than warp interlock structures and 12.3% higher than weft interlock structures in the warp direction, owing to the balanced distribution of binding yarns. In contrast, warp interlock structures exhibit the lowest bending rigidity in the weft direction, making them more flexible. Additionally, hybrid interlock structures provide the highest puncture resistance, while weft interlock structures show the lowest resistance due to their increased porosity. These findings highlight the critical role of fabric architecture in determining both comfort and mechanical properties, providing valuable insights for selecting optimal 3D woven structures in applications requiring specific performance attributes.

Predicting the steady state distribution of air pressure in the unsaturated zone resulting from a pneumatic test provides a method for determining air‐phase permeability. This technique is analogous to the inverse problem of well hydraulics; however, air flow is more complicated than ground water flow because of air compressibility, the Klinkenberg effect, variations in air density and viscosity that result from temperature fluctuations in the unsaturated zone and the possibility of inducing water movement during the pneumatic test. An analysis of these complicating factors reveals that, when induced water movement can be neglected, a linear version of the airflow equation can provide an appropriate approximation for the purpose of determining air‐phase permeability. Two analytical solutions for steady state, two‐dimensional, axisymmetric airflow to a single well partially screened in the unsaturated zone are developed. One solution applies where there is a stratum of relatively low air permeability, separating the stratum in which the well is completed, from the atmosphere. The other solution applies where there is no separating stratum between the domain and atmosphere. In both situations the water table forms the lower horizontal boundary. Applications of both solutions to determine air permeability from data collected during pneumatic tests are presented.

In this study, tri-layer fabrics for surgical gown applications were developed using polypropylene spunbond, polypropylene melt-blown and polyester/rayon spunlace (hydro-entangled) nonwoven layers with the aid of a fusing machine and polypropylene powder as the bonding agent. Weight, thickness, bending rigidity, grab tensile properties, bursting strength, air permeability, water vapour transmission rate, hydrostatic pressure, water resistance (impact penetration test), and synthetic blood repellency of the fabrics (unfinished and finished with water repellent polymethylhydrosiloxanes solution) were measured and the data was statistically analyzed. The results showed that the finished fabric composed of the spunbond outer layer, melt-blown middle layer, and spunlace inner layer, meets the blood repellency requirements of level 4 protection according to the barrier protection classification of Association for the Advancement of Medical Instrumentation (AAMI). The other samples, i.e. untreated type of abovementioned sample and treated and untreated tri-layer of spunbond, melt-blown, spunbond samples offer level 2 protection according to AAMI classification.

Facing the rain after the phase out: Performance evaluation of alternative fluorinated and non-fluorinated durable water repellents for outdoor fabrics