Browsing by Author "Datla, Vasantha Madhuri"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    The Influence of Fiber properties and Processing conditions on the characteristics of Needled fabrics.
    (2002-06-07) Datla, Vasantha Madhuri; Dr. William Oxenham, Committee Chair; Dr. Behnam Pourdeyhimi, Committee Co-Chair; Dr. Yiping Qiu, Committee Member
    In nonwovens, the inherent fiber crimp characteristics, along with finish determine the processing efficiency and the finished fabric properties like rapid wrinkle recovery, durability, bulk, loft, warmth and resistance to abrasion. Understanding the fiber crimp's influence on the processing properties of nonwoven fabrics has been hampered by the lack of appropriate techniques. Also the carding performance and other process parameters related to different aspects of web and fabric quality have always been a major concern in the manufacture of nonwoven fabric. The purpose of this study is to investigate the role of fiber crimp and other processing conditions on nonwoven fabric properties. This will involve possible interactions between fiber crimp, carding parameters, crimp retention and relate these to fabric properties and processability in nonwoven equipment. For this purpose, nonwoven needle-punched fabrics were produced from PET fibers with different crimp levels, using different card machine parameters during web formation. The webs were then cross-laid and bonded by needle punching using different needling densities and the influence all of these parameters were investigated with respect to "fabric" properties like basis weight, tensile strength, compressibility, air permeability, and directional distribution of the fibers (ODF's) using image analysis. The basis weight measurements were statistically analyzed and investigated. It is concluded that the fiber crimp, carding and needling density significantly contribute to the differences in the basis weight measurement and so do the various fiber to card interactions. The tensile strength of various needled fabrics were investigated. The results have shown that the mechanical response mainly depends on the fiber orientation distribution and processing conditions. Fiber crimp and finish also influence the mechanical performance. Higher carding speeds produced a dominant MD oriented structure and the ODF explains the cross-lapping effect and also the crimp pullout during carding. The air permeability measurements were largely dependent on the weight per unit area and thickness of the final needled fabrics. So the fiber crimp, the various carding and the needling density parameters have a decisive effect on the rate of airflow through the fabric. A power function can be used to describe the fabric behavior under compressive loads. This function which is fit to experimental data delivers two fitting parameters that characterize the shape of the experimental load-thickness curve. The extracted characteristic compression parameters are being evaluated with respect to inherent fiber crimp characteristics and the various carding and needling machine parameters during nonwoven production.
  • No Thumbnail Available
    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.