Browsing by Author "Dr.Behnam Pourdeyhimi, Committee Chair"

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Absorbency Characteristics of Kenaf Core Particles
(2004-05-21) Zaveri, Mitul Dilip; Dr.Behnam Pourdeyhimi, Committee Chair; Dr. Medwick V. Byrd, Committee Member; Dr. Donald Shiffler, Committee Member; Dr. Timothy Clapp, Committee Member
Chopped Kenaf Core (2"; to 4" in length), obtained from Greene Natural Fibers — a company located in Snow Hill, North Carolina, was ground into very fine particles (below 1 mm) and categorized into various size ranges. The ground particles were tested for water absorbency and the optimum particle size, giving maximum absorbency, was determined. Experiments revealed that Kenaf Core of size range 106 — 425 microns gave the highest water absorbency at saturation, up to 12 times its weight. The 425 — 840 micron range was the next highest and it absorbed water up to 10 times its weight. Factors leading to this optimum particle size range were determined, the absorption mechanisms taking place were studied and experimental analysis was done to prove the results obtained. Scanning Electron Microscopy (SEM) images were also taken to understand the shape and profile of the granular particles in fine detail. Various chemical treatment and refining experiments were carried out on the highly absorbent particle sizes (106 — 840 microns) to enhance their bonding properties and to make handsheets from them. The highly absorbent Core particles were treated with NaOH in water bath at 90 ° C, Cooked with NaOH and Na2S at 170 ° C in a bomb reactor and treated with water in a water bath at 90 ° C, all for 3 hours. Handsheets were made from the chemically treated particles to determine if there was sufficient bonding between them. To enhance the bonding further, the particles were refined in a blender for one hour. The effect of chemical treatment and refining on the absorbency properties of the Core was determined. SEM analysis of the particles was done to visualize the fibrillation caused due to refining. Handsheets were made with a blend of hardwood and highly absorbent (untreated and water treated 106 — 840 micron) refined Core particles with 50 — 70% of Kenaf Core in them. The absorption properties of these handsheets were determined and compared with the absorption of a handsheet made from fluff pulp (same basis weight). As the final step, the handsheets made from a blend of kenaf core and hardwood pulp were sandwiched between a pair of 17gsm lightly calendared polypropylene spun bond fabrics.
Enzymatic Treatment of Fibers for Nonwovens
(2006-08-09) Arumugam, Karthik; Dr.Samuel M. Hudson, Committee Member; Dr.Behnam Pourdeyhimi, Committee Chair; Dr.Juan Hinestroza, Committee Member
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.
Surface Modification of Fibers and Nonwovens with Melt Additives
(2008-12-19) Datla, Vasantha Madhuri; Dr. Alan Tonelli, Committee Member; Dr.Behnam Pourdeyhimi, Committee Chair; Dr.Eunkyoung Shim, Committee Co-Chair; Dr. Keith Beck, Committee Member; Dr. Jan Genzer, Committee Member
Polypropylene (PP) fibers, widely utilized in woven and nonwoven industry, have highly inert and hydrophobic surfaces. Therefore a modification aimed at the creation of a more polar surface is an important issue in the application areas where wettability and adhesion properties are required. One way to impart surface hydrophilicity into polypropylene is blending of the melt additives prior to or during the fiber spinning process. It is reported that some oligomeric melt additives spun with host polymer migrate to surface and generate surface reactivity at low concentration without altering bulk properties. The principal objective of the study is to explore effective ways of imparting hydrophilicity to polypropylene fibers and nonwovens with the melt additives based on an understanding of hydrophilic surface formation on polypropylene and key parameters related to the process. It involves study of possible interactions between polypropylene polymer and the melt additive leading to a hydrophilic surface by melt additive surface migration. For this purpose, different classes of nonionic melt additives were melt extruded with a twin-screw extruder using a melt additive concentration of 2% to investigate how hydrophilic surfaces are created. The mechanism of hydrophilic surface creation by melt additives was explored using X-ray photoelectron spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Atomic Force Microscopy (AFM) and dynamic contact angle analyses. XPS analysis revealed migration and surface enrichment of melt additives by increase in the surface amount of polar oxygen groups leading to a more hydrophilic surface. Melt additives with different chemistries were studied for their surface modifying effectiveness. It is found that both size and characteristics of hydrophilic and hydrophobic groups in melt additives as well as their relative size; represented by HLB (Hydrophilic-Lipophilic Balance) value, affect the rate and the degree of surface additive segregation. The surface energy and the polar contribution of the polypropylene film increased due to the migration of low-molecular-mass components (additives) to the surface resulting in increase in surface wettability. Low molecular weight oxidized materials were observed in the form of a globular morphology on the surface of the film. Additionally thermal analysis of melt blended PP films using DSC revealed phase-separated nature. We also found that resulting surface characteristics are very dynamic, so melt additive containing polymer surfaces response to water or heat application effected surface properties and composition. Some melt additive containing PP films response to water enhanced surface migration and wettability leading to a durable hydrophilic PP surface. Analyses of melt additive concentration effects established that the minimum additive concentration to cause surface chemical changes is about 1 wt%. Finally evaluation of surface properties of spunbond PP nonwoven fabrics with the melt additives indicated that the structural and geometrical differences between the films and fabrics clearly affected the polymer surface characteristics and migration on surface wettability. It is shown that hydroentangling and heat calendering, which are typical spunbond nonwoven bonding processes, resulted in changes in the fiber surfaces. Heat calendering hastened the blooming of the melt additive by facilitating surface migration leading to enhanced wettability over time and found that 130°C is an optimum temperature to bring the desired surface hydrophilicity (complete wettability) in PP films or fabrics with 2-wt% of ethoxylated alcohol melt additives.