Pamela Banks-Lee

Determining Effective Thermal Conductivity of Multilayered Nonwoven Fabrics

The average effective thermal conductivity K eff is measured for forty-eight multilayered needle-punched nonwoven samples. Samples are produced using glass and ceramic fibers layered in several different constructions and punched with needles with varying numbers of barbs. The thermal conductivities are determined at steady state, using a Holometrix guard hot plate at an average applied temperature of 455°C. Statistical results show an ability to predict effective thermal conductivity with greater than 88% accuracy. Important parameters of the model include fabric weight, thickness, porosity, and structure, along with the applied temperature. Results also show that the nine-barbed structure with the highest ceramic content has the greatest potential for thermal insulation at elevated temperatures.

Determining Radiative Heat Transfer Through Heterogeneous Multilayer Nonwoven Materials

A theoretical equation of the combined thermal conductive, convective, and radiative heat flow through heterogeneous multilayer fibrous materials is presented. Samples whose properties are analyzed by this equation were constructed from glass and ceramic webs and used in an earlier work to experimentally determine their thermal conductivities. In that experimental work, overall effective thermal conductivities were determined using a guarded hot plate instrument with temperatures ranging from 430 to 480°C. In the theoretical equation presented here, thermal convective heat flow is ignored because of fabric structural conditions, and the conduction component of the overall conductivity is determined by Frickes equation. Furthermore, the results of Frickes equation and the overall effective thermal conductivity are used to estimate the radiative thermal conduc tivity of the samples.

Multi-fiber needle-punched nonwoven composites: Effects of heat treatment on sound absorption performance

Nonwovens have been increasingly used in car interiors for noise reduction. Most of these nonwovens are subjected to thermal treatments to give the nonwovens their final three-dimensional forms. Therefore, it became crucial to investigate the effects of thermal treatment on sound absorption characteristics of nonwovens. In this study, the effects of the material and treatment parameters on airflow resistivity and normal-incidence sound absorption coefficient of thermally treated three-layered nonwoven composites have been studied. The material parameters included fiber size and porosity. The treatment factors included the temperature and duration. The thermally treated three-layered nonwoven composites are classified into three types based on the material content and fiber blend. Sandwich structures consisting of polylactide/hemp/polylactide and polypropylene/glassfiber/polypropylene layers were called LHL and PGP, respectively. The sample which consisted of three layers of an intimate blend of polypropylene-glassfiber was named as PGI. Both temperature and duration of thermal treatment have been found to affect air flow resistivity and sound absorption. An increase in air flow resistivity and a decrease in sound absorption have been detected with heat treatment. A similarity has been observed between the thermal behaviors of PGP and PGI, which included the same thermoplastic polymer fiber. Variation in air flow resistivity of sandwich structure nonwoven composites increased with the increase in temperature, which was not observed in the intimate blend ones. The air flow resistivity of heat-treated nonwovens followed a steeper trend compared to unheated nonwovens per change in material parameters. In terms of treatment parameters, the difference between the thermal treatment and the melting point of the thermoplastics constituent of the nonwoven composite was found to be a significant factor on sound absorption. This effect of treatment temperature on sound absorption changed with treatment duration. The sound absorptive characteristic of the nonwoven composites in terms of sound frequency underwent a change with thermal treatment due to the structural changes with exposure to high temperature.

Air Permeability of Multilayer Needle Punched Nonwoven Fabrics: Theoretical Method

The theoretical permeability of multilayered nonwoven fabrics was studied using a modified Kozeny equation. The Kozeny equation is based on the concept of a hydraulic radius, i.e., a characteristic length parameter. It is limited to structures with porosities less than 0.94. The structures used in this research are intended for use as high temperature insulation and all had porosities of greater than 0.96. The Kozeny equation was therefore modified to extend its usefulness to fabrics with higher porosity. Fabric construction parameters, along with fabric and fiber properties were used as inputs to this model and theoretical air permeability was determined. The effect of number of barbs and layering structure on the determination of theoretical air permeability was also considered and discussed. Statistical analysis was performed showing that fabric thickness, number of needle barbs, mean pore size and fabric density are significant factors in predicting theoretical air permeability.

Hemp-fiber based nonwoven composites: Effects of alkalization on sound absorption performance

The effects of the material and treatment parameters on airflow resistivity and normal-incidence sound absorption coefficient of alkalized three layered nonwoven composites have been studied. The material parameters included fiber size and porosity. The treatment factors included the temperature, duration and concentration. The alkalized composite was a three-layered nonwoven sandwich structure consisting layers of Polypropylene/Hemp/Polypropylene. Alkalization treatment has been found to result in a loss of basis weight and a decrease in air flow resistivity. Among treatment factors, only temperature was found to be a statistically-significant factor on air flow resistivity. Higher-temperature alkalization leads to higher air flow resistivity compared to the lower-temperature treatment. Alkalization at higher temperature and higher concentrations gives better results in normalized sound absorption performance compared to lower-temperature and lower-concentration treatments, respectively.

Air Permeability of Multilayer Needle Punched Nonwoven Fabrics: Experimental Method

In many applications, fabric structure has a dominant influence on the performance characteristics of a material, particularly in controlling transport of flows. Experimental air permeability was determined for 12 multilayer, heterogeneous, needle punched nonwoven materials. Samples were produced using multiple layers of ceramic and glass fibers. The fibers used to produce the ceramic layers for all samples have approximately the same diameter and density as the fibers used to produce the glass layers for all samples. Therefore, the samples were assumed to be multilayer homogeneous fabrics. In this paper, the experimental permeability is measured usingstandard equipment and results are discussed as a function of fabric construction parameters. Results showed that increasingthe fraction of glass and/or the fraction of ceramic content, and increasingthe number of needle barbs all cause a decrease in air permeability. Statistical results showed that the experimental air permeability can be predicted with greater than 99% confidence when using fabric thickness, fraction of glass in the sample, and fabric density as independent variables in the model.

An innovative wood-fiber composite incorporating nonwoven textile technologies.

This article is the first to describe a process of manufacturing engineered wood composites that combine two nonwoven textile technologies: bicomponent fiber and needle punching. Hardwood fiber was blended with 10 percent urea formaldehyde and formed into mats. The mats were sandwiched with polypropylene/polyester bicomponent fibers and then needle punched. Needle punching was done by means of barbed needles that oscillated in a vertical direction with regard to the surface of the fiber mat. The barbed needles mechanically interlaced the bicomponent web to the wood-fiber mat and pulled some of the polymer fibers through the thickness direction of the mat. During hot pressing, the polypropylene sheath of the bicomponent fiber flowed, bonded with adjacent wood fibers, and coalesced with the sheath of the adjacent bicomponent fibers. The mats were pressed until the urea formaldehyde was fully cured. Bending and tensile properties of the needle-punched wood composite were assessed and compared with medium-den...

Evaluating the Effectiveness of Bifid Medical Needles for Protection from Needle-Stick Injuries

Most blood-borne pathogen transmissions in the healthcare industry are caused by needle-stick injuries, and protection from sharp invasive instruments is of great concern. Recently, a modified design of medical needles (bifid needles) has been proposed to prevent needle-stick injuries. The bifid needle is designed to provide protection for users by entangling itself with an article of personal protective clothing. The purpose of this research is to study the effectiveness of bifid medical needles for protection against needle-stick injuries. A comparison of bifid and standard needles is conducted by evalu ating the forces experienced by the needle during penetration through Spectra 1000® woven fabric using a force measurement device. A predictive model is derived, expressing resistance to needle penetration in terms of needle and fabric parameters. Our study shows that bifid and standard needles behave differently when penetrating through a fabric. The predictive model indicates that the independent parameters of fabric orientation, needle penetration depth, and needle gap and their interactions significantly affect fabric resis tance to needle penetration.

Protective system from medical needle-sticks. Part I: Background and system development

Previous research on healthcare workers’ protection has concentrated on liquid barrier protection by providing impermeable personal articles such as latex gloves. This property is of high importance but since most blood-borne pathogen transmissions in the healthcare industry are caused by needle-stick injuries, protection from sharp invasive instruments should also be of high concern. And since latex and alike provide no protection against needle-stick injuries, new protective systems need to be developed and evaluated. This part of the study provides a review regarding the current practice of protection and the serious problems that arise from needle-stick injuries. Additionally, the development of new protective system is described. In part II of the study, evaluation of the new system will be provided.

Protective System from Medical Needle-sticks. Part II: Evaluation of Woven Structures and Bifid Needles

We have shown in Part I [1] of this study that medical needle-stick injuries are causing serious health problems to healthcare personnel and other professionals that require the attention of healthcare and textile researchers to develop new protective systems. Responding to such need, a needle force measurement device that is capable of measuring dynamic forces experienced by medical needles during needle penetration through protective articles was developed and described in part I. This paper reports the results of evaluation of protective woven fabrics from high performance fibers and standard and bifid medical needles using the force measurement system. The woven fabrics varied in cover factor, number of layers, and orientation angle. Standard and bifid needles with different gap widths were used to evaluate the resistance of the fabric to needle penetration.