Search

This research is a collaboration between Wake County Economic Development, NCSU Economic Development, and the College of Textiles. The overall purpose of this research is to examine the process by which an Industry Technology Roadmap (ITR) is developed, to start the development of an elementary roadmap for the medical nonwovens industry, and finally to identify the role of the College of Textiles, NCSU in effectively implementing this roadmap. The scope of this thesis covers the examination of Industry Technology Roadmapping process, including the selection process for panel members and preliminary identification of goals and challenges for the nonwoven medical textiles. Compiling the roadmap itself goes beyond the scope and time frame of this masters thesis. A mixed methods method is employed for data collection and analysis. Experts affiliated with the nonwovens industry, personnel from the Association of Nonwovens Fabrics Industry (INDA), Nonwovens Cooperative Research Centre (NCRC), and faculty from NC State University were surveyed. An attempt was also made to conduct an industry wide survey to collect data about Industry location factors. The results of this research provide insight into the road-mapping process that can be employed for the nonwovens industry. A pilot roadmap for the nonwovens medical industry identifies the process/product performance targets of medical textiles, technology barriers/challenges for achieving these targets and the priorities related to research and development for achieving the targets. Finally the research proposes an action plan for the College of Textiles in the areas of (i) types of collaborations with the nonwoven industry and (ii) allocation of research and development resources to better serve nonwoven industry.

In this work we have tried to relate the thermal bond strengths with the concepts of chain dynamics via interfacial adhesion development at symmetric polymer interfaces. To relate structural bond strengths with polymer chain dynamics we need a molecular connectivity relation. This requires relation of the microscopic dynamics of chains with macroscopic interfacial adhesion measurements. Previous literature does indicate that the nonwoven fabric strength reaches a maximum for a particular value of any of the following variables: temperature, contact time, pressure and quench rate, while the others are kept constant. The rationale for such a behavior has been supported in qualitative terms where a fundamental understanding of the polymer physics is lacking. The properties of reptation and diffusion of polymer chains to form effective entanglements and boost interfacial adhesion has been reviewed. The present work provides a useful compendium of valuable inter-relations between the effects of calendar speed and calendar temperature on interfacial bond strengths. The varying molecular weights of the polymer have been found to affect the thermal bonding process in previous studies. Our results for the effect of varying molecular weight on bond strengths have been found to be an extension to Wool's work beyond a critical molecular weight. Interesting trends for the effect of molecular weight on interfacial adhesion have been presented.

Cellulases are natural catalysts for the modification of cellulosic materials. The major advantage of enzymes in wet processing is their specific action without undesirable side effects. Cellulase treatment is commonly used to produce specific finishing effects such as ageing, defuzzing, and softening. The latter is often achieved by sacrificing the strength of the fabric. The strength loss problems would be severe in case of nonwovens since cellulase could attack bonded area of the fabrics which leads to significant web strength loss. Therefore, this research was undertaken to investigate the effects of enzymatic pretreatment on the properties of cotton fibers and fabric produced from enzymatically modified fibers. The first stage of this research was to investigate the effect of cellulase action on bleached cotton fibers. Two enzyme solutions, Cellusoft L, a commercial whole cellulase solution, and monocomponent endoglucanases (EG) devoid of its cellulose binding domain (CBD) were used in this work. Enzyme hydrolysis was monitored by weight loss, enzyme adsorption and reducing sugar formation. The effect of enzyme action on the fiber surface was also analyzed by Congo red dye analysis and imaging with Scanning electron microscope (SEM). The analysis revealed that Cellusoft L was more aggressive than the CBD-free monocomponent endoglucanases. Based on the analysis of reducing ends, nonwoven fabrics were prepared by carding and hydroentangling of fibers treated under selected conditions. The fabrics prepared from fibers treated with Cellusoft L and CBD-free EG's, showed improved performance in terms of tenacity in comparison to fabrics prepared from untreated fibers. However, improved bending properties were observed with fabrics made of fibers pretreated with Cellusoft L rather than the fabrics made of CBD-free Endoglucanases treated fibers. It has been established that a soft and strong fabric was obtained if fibers were pretreated with cellulases before the formation of nonwoven fabric.

Today much importance is given to the acoustical environment. Noise control and its principles play an important role in creating an acoustically pleasing environment. This can be achieved when the intensity of sound is brought down to a level that is not harmful to human ears. Achieving a pleasing environment can be obtained by using various techniques that employ different materials. One such technique is by absorbing the sound and converting it to thermal energy. Fibrous, porous and other kinds of materials have been widely accepted as sound absorptive materials. A literature scan [19, 20, 53, 76] showed nonwovens could be considered to be a prospective candidate for sound absorption. The impetus for this study stemmed from the drawbacks associated with the existing sound absorbing materials like felts made from glass, asbestos and rock wool and foams. Some of these drawbacks include the fact that the materials are unsuitable for molding, non-recyclable, difficult to handle and install, dust accumulating and in the case of foams are high in density. These drawbacks are forcing the acoustical product manufacturers to look into natural, biodegradable raw materials. To assist in that effort, the research presented here studies the feasibility of using kenaf fibers blended with reclaim polyester fibers and other fiber blends as sound absorptive materials. Products from kenaf/reclaim fiber blends will have the benefit of low raw materials and manufacturing cost, at the same time providing a suitable end use for reclaim polyester fibers. Early work in noise control has shown the importance of understanding micro- structural and other physical parameters in designing high performance acoustic materials. As a final objective, this research describes how the physical elements of nonwoven sound absorbent system like fiber type, fiber size, fiber cross section, material thickness, density, airflow resistance and porosity can change the absorption behavior of nonwovens. Influence of fire retardant treatment, surface impedance, air gap, compression, manufacturing methods and attachment of film on sound absorption behavior of nonwovens were also considered.

It is known that not all polymers can be melted and extruded to form polymer fibers. Electrospinning process involves a direct method to produce fibers in nanometer range by dissolving the polymer in solvent(s) to form the spinning solution. In this work, the spinning solution was prepared by dissolving Poly (ethylene terephthalate) polymer in triflouroacetic acid and methylene chloride. Charging the solution to a very high potential initiated the process to produce electrospun fibers. With increasing voltage, a critical point is reached and a charged jet of the solution is ejected. As this charged jet moves in the air, the solvent evaporates, leaving behind a charged polymer fiber that collects on a targeted source (rotating drum). Equipment to form electrospun fiberwebs on a rotating drum was designed and successfully built. The equipment for this process is relatively simple and small since this process lend itself to the production of fibers/fiberwebs from small quantity of polymer solution. An experiment was designed to investigate the influence of polymer concentration in the spinning solution and the electric field level on fiber and fiberweb response of interest. Electrospun fibers and fiberwebs were characterized for fiber diameter and its distribution, orientation distribution function, and pore size and its distribution. The results showed that an increase in the electric field resulted in a decrease of the average diameter of the electrospun fibers. It has also been observed that there was concentration/electric field interaction effect on fiber diameter. As the electric field increased keeping polymeric concentration constant, the fibers orientation in machine direction increased. It was observed that as the electric field was increased, the average pore diameter decreased. The decrease in average pore size with increase in electric field was explained in terms of fiber diameter as well as fiberweb structural parameters (orientation and basis weight).

The main focus of this research is to make a composite of sufficient strength from glass fibers using low melt polyester or bicomponent (polyester/polyethylene sheath/core) fibers as binder fibers for nonwoven preforms. A wet-laid hydroentangled sheet consisting of a blend of glass and low melt binder fibers is used to make compression molded composite. An appropriate white water recipe for dispersing glass and binder fibers was obtained after personal conversation with Owens Corning Company and after image analysis of the trial sheets. The amount of defects in the fabric was analyzed and optimum time of dispersion was established. 6 layers of wet lay sheets were stacked and hydroentangled to get a high weight per unit length single hydroentangled sheet that is then heat pressed. When heat pressed, the binder fibers in the blend melt, adhere to the glass fibers and form a composite. These composites were tested for stiffness, toughness and flexural strength. An instron machine was used for tensile and 4-point bending tests. Stress strain curves were obtained and the secant modulus at breaking strain was determined. The area under the curve was measured determine the toughness of the material. The tensile strength and toughness increased significantly with increasing glass fiber content of up to 30-40%, after which the strength of the composite decreases. This may be caused by the reduction in binding points and lower adhesion between the glass fibers resulting in lower tensile and flexural strength. The innovative aspect of this research is in the manufacturing of composites using glass fibers along with binder fibers. Some of the current composite manufacturing techniques use resin to bind the fibers/sheets. Resins are costly and also, not environment friendly. By using binder fibers, the need of using resin is eliminated. Elimination of resin and manufacture of high strength low cost composites with more process flexibility is an imperative objective of this research.