Marian McCord

Modifying Nylon and Polypropylene Fabrics with Atmospheric Pressure Plasmas

Polypropylene and nylon 66 fabrics are subjected to atmospheric pressure He and He-O2 plasmas for selected exposure time intervals. Scanning electron microscopy anal ysis of the fabrics shows no apparent changes in the plasma-treated nylon fiber surfaces, but significant surface morphological changes for the polypropylene. Surface analyses of the nylon filaments reveal small differences in the surface carbon and oxygen contents between the treated and control groups. The surface oxygen and nitrogen content of the polypropylene fabric increases significantly after treatment in both He and He-O2 plasmas. There is a slight decrease in nylon fabric tensile strength after treatment in He plasma for 3 minutes, while. there is no significant change in tensile strength of the nylon fabric treated with He-O2 after exposure times of up to 8 minutes.

Effect of atmospheric plasma treatment on desizing of PVA on cotton

Both air/He and air/O 2/He atmospheric plasma treatments are applied to desize PVA on cotton, then PDR (percent desizing ratio) and tensile strengths of cotton fabrics and single yams are measured. XPS and SEM are used to analyze the effects of atmospheric pressure plasma treatments on PVA. These treatments can both remove some PVA sizing and significantly improve PDR by washing, especially by cold water washing. The tensile strengths of cotton fabrics treated with atmospheric pressure plasma are the same as for the unsized fabric. XPS analysis of the plasma treated PVA films reveals surface chemical changes such as chain scission and formation of polar groups, which promote the solubility of PVA in cold water. Air/O2/He plasma is more effective than air/He plasma on PVA desizing.

One-step synthesis of silver nanoparticle-filled nylon 6 nanofibers and their antibacterial properties

A novel and facile one-step approach to in situ synthesize silver nanoparticle-filled nylon 6 nanofibers by electrospinning is reported. The method does not need post-treatments and can be carried out at ambient conditions without using additional chemicals. It employs the electrospinning solvent as a reducing agent for in situ conversion of AgNO3 into silver nanoparticles during the solution preparation. The resultant silver nanoparticle-filled nylon 6 hybrid nanofibers show an excellent fibrous structure (fiber diameter at 50–150 nm), with narrow size 2–4 nm silver nanoparticles uniformly dispersed throughout the nylon 6 matrix. DSC analysis shows that the in situ incorporation of silver nanoparticles increased the Tg and crystallinity of the resultant nanofibers. These silver nanoparticle-filled nylon 6 nanofibers exhibit a steady and long-lasting silver ion release behavior, and robust antibacterial activity against both Gram-positive B. cereus and Gram-negative E. coli microorganisms.

The effect of atmospheric pressure helium plasma treatment on the surface and mechanical properties of ultrahigh-modulus polyethylene fibers

Ultrahigh-modulus polyethylene fibers were treated with atmospheric pressure He plasma on a capacitively coupled device at a frequency of 7.5 kHz and a He partial vapor pressure of 3.43 × 103 Pa. The fibers were treated for 0, 1, and 2 min. Microscopic analysis showed that the surfaces of the fibers treated with He plasma were etched and that the 2-min He plasma-treated group had rougher surfaces than the 1-min He plasma-treated group. XPS analysis showed a 200% increase in the oxygen content and a 200% increase in the concentration of C—O bonds (from 11.4% to 31%) and the appearance of C=O bonds (from 0% to 7.6%) on the surface of plasma-treated fibers for the 2-min He plasma-treated group. In the microbond test, the 2-min He plasma-treated group had a 100% increase of interfacial shear strength over that of the control group, while the 1-min He plasma-treated group did not show a significant difference from the control group. The 2-min He plasma-treated group also showed a 14% higher single-fiber tensile strength than the control group.

Atmospheric pressure helium + oxygen plasma treatment of ultrahigh modulus polyethylene fibers

Ultrahigh modulus polyethylene fibers were treated with atmospheric pressure helium + oxygen plasma in a capacitively coupled device at a frequency of 7.5 kHz. The fibers were treated for 0, 0.5, 1, 1.5, and 2 min. The surfaces of the fibers treated with He + O2 plasma were etched and micro-cracks were formed. XPS analysis showed a 65ndash213% increase in oxygen content on the surfaces of all plasma-treated fibers, except for the 1.5 min group. An increase in the concentration of C—O and the appearance of C=O bonds on the surfaces of plasma-treated fibers were observed. In the micro-bond test, He + O2 plasma-treated groups had a 65–104% increase in interfacial shear strength over that of the control. The tensile strength of the fibers was either unchanged or decreased by 10–13% by the plasma treatments.

Effects of atmospheric pressure helium/air plasma treatment on adhesion and mechanical properties of aramid fibers

In order to investigate the effect of atmospheric pressure plasmas on adhesion between aramid fibers and epoxy, aramid fibers were treated with atmospheric pressure helium/air for 15, 30 and 60 s on a capacitively-coupled device at a frequency of 5.0 kHz and He outlet pressure of 3.43 kPa. SEM analysis at 10 000× magnification showed no significant surface morphological change resulted from the plasma treatments. XPS analysis showed a decrease in carbon content and an increase in oxygen content. Deconvolution analysis of C1s, N1s and O1s peaks showed an increase in surface hydroxyl groups that can interact with epoxy resin. The microbond test showed that the plasma treatment for 60 s increased interfacial shear strength by 109% over that of the control (untreated). The atmospheric pressure plasma increased single fiber tensile strength by 16-26%.

Surface Modification of Organic Polymer Films Treated in Atmospheric Plasmas

The effect of plasma treatment on surface characteristics of polyethylene terephthalate films was investigated using helium and oxygenated-helium atmospheric plasmas. Sample exposure to plasma was conducted in a closed ventilation test cell inside the main plasma chamber with variable exposure times. The percent weigh loss of the samples showed an initial increase followed by decrease with extended exposure time, indicating a combined mechanism of etching and redeposition. The wettability as measured by the contact angle showed a sharp initial increase followed by a steady-state trend with increased exposure time, suggesting a change in surface functionality. Atomic force microscopy analysis revealed increase in surface roughness, as well as evidence of redeposition of etched volatiles. Functionality changes were measured using X-ray photoelectron spectroscopy and these changes were correlated to the new plasma-induced properties.

Multifunctional ZnO/Nylon 6 nanofiber mats by an electrospinning-electrospraying hybrid process for use in protective applications.

Abstract ZnO/Nylon 6 nanofiber mats were prepared by an electrospinning–electrospraying hybrid process in which ZnO nanoparticles were dispersed on the surface of Nylon 6 nanofibers without becoming completely embedded. The prepared ZnO/Nylon 6 nanofiber mats were evaluated for their abilities to kill bacteria or inhibit their growth and to catalytically detoxify chemicals. Results showed that these ZnO/Nylon 6 nanofiber mats had excellent antibacterial efficiency (99.99%) against both the Gram-negative Escherichia coli and Gram-positive Bacillus cereus bacteria. In addition, they exhibited good detoxifying efficiency (95%) against paraoxon, a simulant of highly toxic chemicals. ZnO/Nylon 6 nanofiber mats were also deposited onto nylon/cotton woven fabrics and the nanofiber mats did not significantly affect the moisture vapor transmission rates and air permeability values of the fabrics. Therefore, ZnO/Nylon 6 nanofiber mats prepared by the electrospinning–electrospraying hybrid process are promising material candidates for protective applications.

The Use of Atmospheric Pressure Plasma Treatment in Desizing PVA on Viscose Fabrics

In this study, both air-oxygen-helium and air-helium atmospheric pressure plasma treatments were employed to desize PVA on a rayon (viscose) fabric. Both the plasma treatments were able to remove some of the PVA on the rayon fabric and increase PVA solubility in cold water, resulting in a higher weight loss in cold washing. The effect of the atmospheric pressure plasmas became greater as the treatment time increased. Plasma treatment followed by one cold and one hot washing had the same effect as the conventional chemical treatments followed by two cycles of cold and hot washing. The atmospheric plasma treatment did not have negative effect on rayon fabric tensile strength.

Conformal Atomic Layer Deposition of Alumina on Millimeter Tall, Vertically-Aligned Carbon Nanotube Arrays

Atomic layer deposition (ALD) can be used to coat high aspect ratio and high surface area substrates with conformal and precisely controlled thin films. Vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) with lengths up to 1.5 mm were conformally coated with alumina from base to tip. The nucleation and growth behaviors of Al2O3 ALD precursors on the MWCNTs were studied as a function of CNT surface chemistry. CNT surfaces were modified through a series of post-treatments including pyrolytic carbon deposition, high temperature thermal annealing, and oxygen plasma functionalization. Conformal coatings were achieved where post-treatments resulted in increased defect density as well as the extent of functionalization, as characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Using thermogravimetric analysis, it was determined that MWCNTs treated with pyrolytic carbon and plasma functionalization prior to ALD coating were more stable to thermal oxidation than pristine ALD coated samples. Functionalized and ALD coated arrays had a compressive modulus more than two times higher than a pristine array coated for the same number of cycles. Cross-sectional energy dispersive X-ray spectroscopy confirmed that Al2O3 could be uniformly deposited through the entire thickness of the vertically aligned MWCNT array by manipulating sample orientation and mounting techniques. Following the ALD coating, the MWCNT arrays demonstrated hydrophilic wetting behavior and also exhibited foam-like recovery following compressive strain.