Nylon Film Research Articles

Activation Energies of Light Fading of Non-ionic Disperse Dyes in Hydrophobic Polymers

Eight non–ionic (disperse) dyes adsorbed in films of cellulose acetates, nylon and poly(ethylene terephthalate) (PET) have been faded by visible and near–ultraviolet radiation at temperatures in the range 15 to 100°C, and in atmospheres of relative humidities (r. h.) from zero to saturation. Fading is accelerated by rise in temperature, and, at r. h. above 5%, by rise in r. h. Activation energies of fading (Ef) (r. h. > 5%) range between about 3 and 18 kcal/mole, and depend on the nature of the substrate rather than on the structure of the dye. Values rise with increasing crystallinity of the polymer structure, except for PET which gives anomalously low values. The extent of dye–fibre interaction is at a minimum with PET and the rate–controlling step is a purely photochemical one. With the other substrates, the rate of fading is controlled by the dye–substrate interaction. The accelerating action of atmospheric humidity over normal ranges is partly due to its influence on the dye–substrate bonding and partly to its effect in swelling the substrate and thus increasing the diffusion coefficient of oxygen.

Two-silane chemical vapor deposition treatment of polymer (nylon) and oxide surfaces that yields hydrophobic (and superhydrophobic), abrasion-resistant thin films

This article describes a two-silane, chemical vapor deposition (CVD) approach to creating hydrophobic (or even superhydrophobic), abrasion-resistant coatings on silicon oxide and polymer (nylon) substrates. This multistep approach employs only reagents delivered in the gas phase, as follows: (i) plasma cleaning/oxidation of the substrate, (ii) CVD of 3-isocyanatopropyltriethoxysilane, which is used as an adhesion promoter for the substrate, (iii) hydrolysis with water vapor, and (iv) CVD of (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane (the “Rf-Cl silane”). Surfaces are characterized by wetting, spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). This work has the following unique features. First, the authors explore an all gas phase deposition of a new silane coating that is scientifically interesting and technologically useful. Second, the authors show that the presence of an adhesion promoter in the process leads to thinner films that are more robust in abrasion testing. Third, results obtained using plasma/deposition equipment that is relatively inexpensive and/or available in most laboratories are compared to those obtained with a much more sophisticated, commercially available plasma/CVD system (the YES-1224P). The entire deposition process can be completed in only ∼1h using the industrial equipment (the 1224P). It is of significance that the polymer surfaces modified using the 1224P are superhydrophobic. Fourth, the thickness of the Rf-Cl silane layer deposited by CVD correlates well with the thickness of the underlying spin coated nylon surface, suggesting that the nylon film acts as a reservoir of water for the hydrolysis and condensation of the Rf-Cl silane.

Molecular orientation in individual electrospun nanofibers measured via polarized Raman spectroscopy

Using polarized Raman spectroscopy, we have recorded Raman spectra from individual electrospun Nylon-6 nanofibers. Analysis of these single-fiber spectra, compared to those of unoriented and oriented Nylon-6 films, indicates significant molecular orientation. Because electrospinning produces fibers in a jet with a large strain rate, this molecular orientation is expected. We present quantitative measurements of molecular orientation in a single nanofiber and compare these to those of film samples. Such measurements could yield information about the uniformity of the electrospinning process and resulting fibers, and may also allow comparison between spectrally measured orientation functions and single-fiber mechanical properties.

Effect of surface roughness of incident region on determination of tissue optical properties

The reduced scattering and absorption coefficients of the nylon bar with different surface roughness for the smooth and rough surface of the incident region respectively were determined by a spatially resolved steady-state diffuse reflection technique. The anisotropy factors of the nylon film with different surface roughness for the smooth and rough surface of the incident region, respectively, were determined by a goniophotometric measurement technique. The scattering coefficients of the nylon bar with different surface roughness for the smooth and rough surface of the incident region, respectively, were determined for the determination of the reduced scattering and the corresponding anisotropy coefficients of the nylon bar with different surface roughness for the smooth and rough surface of the incident region, respectively. Comparing the determined optical parameters of the nylon bar with different surface roughness for the smooth surface of the incident region with that for the rough surface of the incident region, the results indicate surface roughness can significantly affect the determination of the tissue optical parameters and the effect of the surface roughness of the incident region on the determination of tissue optical parameters is predominant.

Measurement of Acoustic Impedance of Thin Polymeric Films by Acoustic Resonant Spectroscopy

An acoustic resonant spectroscopy technique for measuring the acoustic impedance of micron-scale polymer films without knowing any values of ultrasonic velocity, thickness and density has been developed. The method, which is based on spectral analysis, observes the acoustic resonance between water, the film and a tungsten plate with high acoustic impedance. The acoustic impedances of poly(vinyl chloride), poly(vinyl alcohol) and nylon films are determined by the spectroscopy technique. Moreover, the values of ultrasonic velocity and density of the films are also determined from the resonance frequencies of the films.

The nylon scintillator containment vessels for the Borexino solar neutrino experiment

Borexino is a solar neutrino experiment designed to observe the 0.86 MeV Be 7 neutrinos emitted in the pp cycle of the sun. Neutrinos will be detected by their elastic scattering on electrons in 100 ton of liquid scintillator. The neutrino event rate in the scintillator is expected to be low ( ∼ 0.35 events per day per ton), and the signals will be at energies below 1.5 MeV, where background from natural radioactivity is prominent. Scintillation light produced by the recoil electrons is observed by an array of 2240 photomultiplier tubes. Because of the intrinsic radioactive contaminants in these PMTs, the liquid scintillator is shielded from them by a thick barrier of buffer fluid. A spherical vessel made of thin nylon film contains the scintillator, separating it from the surrounding buffer. The buffer region itself is divided into two concentric shells by a second nylon vessel in order to prevent inward diffusion of radon atoms. The radioactive background requirements for Borexino are challenging to meet, especially for the scintillator and these nylon vessels. Besides meeting requirements for low radioactivity, the nylon vessels must also satisfy requirements for mechanical, optical, and chemical properties. The present paper describes the research and development, construction, and installation of the nylon vessels for the Borexino experiment.

Visco-elastic properties of thin nylon films using multi-cycling nanoindentation

Abstract Time dependent behavior of thin nylon films is investigated by depth sensing nanoindentation. Different loading rates and holding times are applied in single indentation procedures to study the relaxation behavior of nylon resulting in a characteristic nonlinear displacement – time dependence. Several load – time functions of multi-cycling indentation are developed, such as constant load repetition and incremental load increase mode sometimes containing holding segments. Hysteresis loops in multi-cycling nanoindentation quantify the visco-elastic energy of nylon films. The loading rate does not change the loop size if the maximum and minimum load of the cycle are the same. The unloading process has to be sufficiently large to allow the performance of the visco-elastic relaxation of the material.

Detection of functional states of molecularly imprinted thin films with multi-cycling nanoindentation

Molecular imprinting is a chemical technique for the production of molecule-specific cavities. Spin casting with amino acids, aromatic molecules, carbohydrates or pesticides used as template molecules produces thin, selectively imprinted films of nylon-6 and other polymers. The film recognition activity is clearly coordinated with the appearance of nanometer-sized pores. The mechanical properties of the imprinted network reflect the various functional states of molecularly imprinted polymer films. Three specific functional states of the MIP were observed. Pores filled by template molecules may be distinguished from empty pores due to the variation in the elasticity modulus, the viscoelasticity and the hardness. The presence of the template molecule makes the polymer matrix stiffer due to strong hydrogen bonds (or other interactions) with the polymer chains. Films with empty pores have a higher viscoelasticity than those with filled pores. Changes in the polymer network are directly related to the nanomechanical properties and systematically studied in this work.

Ion induced modification in free volume in PN-6 and PES polymers by positron annihilation lifetime studies

The irradiation of polymeric materials with swift heavy ions (SHI) results in a change of their free volume properties which have strong correlation with their macroscopic properties. Positron annihilation lifetime spectroscopy (PALS) has been developed into a powerful characterization tool for the study of free volume and free volume fraction in polymers. Polyamide nylon-6 (PN-6) and polyethersulphone (PES) films of thickness of 250μm were irradiated with C5+ ions of energy 70MeV from 15 UD Pelletron accelerator at Inter University Accelerator Centre (IUAC), New Delhi, India. PN-6 films were irradiated to the fluences of 1011, 1012 and 1013 ions/cm2 whereas PES films were irradiated to the fluences of 9.3×1011, 9.3×1012 and 1.2×1013 ions/cm2. Characterization of the effect of ion irradiation on free volume has been done by PALS. The average free volume and fractional free volume obtained from long lived component, attributed to ortho-positronium (o-Ps) lifetime, are found to decrease with the fluence in both the cases. With increasing fluence, scissioned segments cross-link randomly, resulting in a decrease of average free volume due to overlapping of tracks.

Surface modification of polyamide fibers and films using atmospheric plasmas

In this work, polyamide (Nylon 6) fibers and films were treated under atmospheric pressure glow discharges (APGD) and the effects on the morphology and chemistry of the material were studied. The fibers were plasma treated with N 2, C 2H 2 in He for (0.6–9.6) s at a frequency of 90 kHz, leading to the functionalization of the surface through the addition of new reactive chemical groups such as –COOH and –OH and changing the energy, chemical composition and wettability of the surface. Surface characteristics were examined via contact angle measurements, XPS, and SEM. Wettability tests revealed the improvement of the hydrophilic character of the surface as the water contact angle measured after the plasma treatments significantly decreased. The corresponding changes of the total surface energy were evaluated with a dynamic contact angle analysis system revealing a significant increase due to the exposure that can be mainly attributed to the increase of its polar component. Preliminary XPS results show a significant increase in oxygen content with the addition of carboxylic and hydroxylic groups and a decrease in the carbon content of the surface. Most importantly, the plasma modified nylon fibers and films exhibit a stable wetting behavior, even for weeks after being treated, suggesting that it is a promising technique to minimize aging phenomena.

Nylon surface modification. Part 1. Targeting the amide groups for selective introduction of reactive functionalities

Nylon is a widely used synthetic polymer because it has a combination of strength, flexibility, toughness, and abrasion resistance. For a variety of applications, however, it is necessary to impart desired surface properties by introducing specific functional groups in specific locations and densities. Several chemical modification methods were developed for the introduction of functional groups to nylon surfaces using amide-selective reactions without cleaving the polymer chains. Activation of amides by reaction with potassium tert-butoxide (t-BuOK) facilitates the N-alkylation of surface amides. When 2-bromoethylamine hydrobromide (BEA–HBr) was employed as an alkylating agent, surfaces with a mixture of primary/secondary/tertiary amine groups were obtained. Alkylation with (3-glycidoxypropyl)triethoxysilane (GPTES) was utilized to prepare surfaces with silica-like reactivity. Chemical reduction with borane–THF complex (BH3-THF) results in a 69% conversion of surface amide groups to the corresponding secondary amines. A kinetic study of this reaction for different types of nylon films revealed that the yield was dependent on the segmental mobility of the polymer. These surfaces are useful substrates for the fabrication of nylon-supported composite films.

Nanomechanical measurements on glutamine molecularly imprinted nylon films

Thin, selectively imprinted films of nylon-6 are produced by spin casting with glutamine used as a template molecule. The template molecules can be extracted from the films by a formic acid wash and later reloaded with a similar solution. Infra-red spectroscopy gives a clear characterization of the chemical components of the films. Depth sensing nanoindentation is applied to determine the mechanical properties of the molecularly imprinted polymer films. An optimized multi-cycling test function with a sequence of several loading and unloading procedures was developed. Typical hysteresis loops are visible in the load-displacement charts, which allow the quantitative measurement of the visco-elasticity of the material and a comparison relative to the total elastic contribution during deformation. The characteristic depth dependent hardness and the elastic indentation modulus are also obtained from the nanomechanical tests. Changes in the polymer network caused by the inclusion of the template molecules are clearly related to the nanomechanical properties and are systematically studied in this work. The relative energy loss for pure nylon films lies between 35 and 50% depending on the crystallinity of the films. The glutamine template molecule makes the polymer matrix stiffer due to strong hydrogen bonds between the amino acid and the nylon chains. Removal of the glutamine molecules results in a considerable increase of the visco-elastic energy loss of approximately 16%, whereas reloading again results in an increase of the indentation modulus and the hardness.

Evaluation of particle deposition in aqueous solutions by the quartz crystal microbalance method

Concerning the redeposition of particulate soils in the detergent process, particle deposition onto substrates in aqueous solutions was investigated by the application of the quartz crystal microbalance (QCM) technique, and the effects of the kinds of the particle and substrate and the addition of ethanol were discussed by the extended DLVO theory. The film of polyethylene, Nylon 6 or cellulose acetate as a substrate was prepared on the gold electrode of the QCM by a spin-coating method. The electrode with or without the polymer film was perpendicularly immersed in the aqueous dispersion of spherical polyethylene or nylon particles. The total mass of particles deposited onto the electrode was determined, in situ, from frequency change of the QCM. The deposited mass was also determined from the difference in frequency measured in air before and after the immersion in the dispersion. In both cases, the particle deposition increased with immersion time and attained apparent equilibrium after 30–60 min. Apparent equilibrium deposition was large for the polyethylene particle compared with the Nylon 12 particle. For either particle, a considerable difference in the deposited amount was observed among the substrates. In all systems, the particle deposition drastically decreased by addition of ethanol to the aqueous dispersion. The results were discussed in terms of the electrical double layer, the Lifshitz–van der Waals and acid–base interactions between the particle and the substrate, which were calculated using the experimentally determined surface free energy components and electrokinetic potentials.

Does isothermal crystallization ever occur?

Much of what we think we know about crystallization in polymers is obtained from studies carried out under isothermal conditions. From extrapolations of equilibrium melting temperature to crystallization regimes, interpretations in the literature all assume that the measured temperature of a polymer film is the temperature at which the crystallization occurred.Recently it has been possible to study crystallization at very high supercoolings, even in rapidly crystallizing polymers, through the use of a rapid cooling technique in which a thin film contains a microthermocouple to measure actual temperature. In adequately thin films an isothermal temperature is set up through a balance between the heat of fusion released and the cooling rate applied. This technique has been applied successfully to polypropylenes, and to polyethylene homopolymers and copolymers. The results have told us much about crystallization at very high supercoolings. Recently, a study of the effect of nucleating agents on quench-crystallization in PET and in nylon 6 was conducted, in which it was discovered that films containing nucleating agents generated the expected temperature plateau when crystallization occurred.In this paper, we wish to report the results of studies of thin films of nylon 66 and PET which did not contain nucleating agents. The results are totally unexpected and indicate that a steady state condition exists at the growth face of the polymer, which is not reflected in the macroscopic temperature of the thin film, as measured using a microthermocouple. In other words the measured temperature of a film is not the temperature at which crystallization occurs. The consequences of this finding to our general understanding of crystallization in polymers will be discussed.

Characterisation of heat-sealing part of laminated oriented nylon and polyethylene films

In order to clarify the relationship between heat-sealing conditions and the strength of the heat-sealed part, the crystalline structure of the heat-sealed part of the film was evaluated by differential scanning calorimetry (DSC) and Fourier transform infrared (FT IR) spectroscopy. The laminated films that include a biaxially oriented nylon (ONY) film and a cast linear low-density polyethylene (LLDPE) film with an appropriate adhesive were heat-sealed by using an impulse type heat-sealer. First the possibility of adhesion was examined by changing the processing conditions and the maximum temperature was measured. As for mechanical properties, a peel strength test was performed to evaluate the strength of the heat-sealed parts. However, the strength could not be evaluated by the peeling test alone, because the fracture shifted from the heat-sealed part to the edge of the heat seal accompanied by necking and yielding of the film. In order to solve this problem, a tensile specimen with a semicircular notch was proposed to evaluate the strength of the heat-sealed part. Tensile strength increased with increasing crystallinity of the LLDPE indicated by the melting peak in the DSC measurement and FT IR spectra. It was found that crystallinity profoundly affected the mechanical properties of the heat-sealed part.

Three-Dimensional Structure of the Zone-Drawn Film of the Nylon-6/Layered Silicate Nanocomposites

Semicrystalline polymer/layered silicate nanocomposites exhibit a unique three-dimensional structure associated with the high-aspect ratio constituents (layered silicates and polymer crystallites), which is sensitive to shear and deformation history. Beginning from quenched biaxially extruded films of nylon-6/ montmorillonite nanocomposites, the impact of elevated temperature uniaxial drawing on the orientation of the layered silicate and crystallites, crystalline polymorphism, and layered silicate buckling was studied using X-ray and transmission electron microcopy. The quenched biaxially protruded films exhibited a uniplanar crystalline texture with the b-axis of the dominate γ-form oriented toward the normal to the film surface and the surface of the layered silicate oriented parallel to the film surface. Small-angle scattering features suggest that the lamellar of the γ-form is within the proximity of the layered silicate and has a fringed micelle structure. Upon uniaxial drawing, α-crystallites developed with a lamellar regularity of ∼15 nm along the draw direction, comparable to previous studies on pure nylon-6 fibers. The newly formed α-form exhibited a uniaxial texture with the b-axis parallel to the draw direction. This suggests that the α-form crystallized during the drawing of the film and does not have an orientation correlation with the layered silicate. Finally, the layered silicate within the zone-drawn film buckled perpendicular to the draw direction, analogous to failure of a uniaxially strained sheet of paper. The failure mode appears to occur for a collection of parallel aluminosilicate layers (2−4) and not individually. Recognition of the structural changes of the layered silicate and crystalline regions in response to uniaxial deformation of planar oriented films is critical to ascertaining the local transport properties of shaped layered silicate nanocomposite parts.

A comparative study of the surface activation of polyamides using an air dielectric barrier discharge

Nylon-6 and Nylon-12 films were modified in an air dielectric barrier discharge (DBD) to understand the contributions of parent polymers structure to the resulting surface modification. The modified polyamide films were characterised by contact angle measurement, XPS, SIMS and ATR-FTIR techniques. For DBD treatment under similar experimental conditions, the resultant surface hydrophilic modification of the Nylon-12 film (based on contact angle measurement) was slightly greater than that of the Nylon-6 film. In contrast, the oxygenation of the surface achieved by the DBD treatment of the Nylon-6 film (in terms of XPS derived O/C ratios) was significantly greater than that of the Nylon-12 film. Post-processing storage study after one-month show recovery of modifications (in terms of the contact angle and O/C ratios) induced by DBD treatment. The recovery of modified surface was relatively marked for the Nylon-6 film. On the basis of SIMS investigations of the Nylon-12 film, formation of low molecular weight oxidised material at the treated surface after DBD treatment and their subsequent decay with extended storage is arguably responsible for the greater recovery from modification. On the other hand, relatively stable hydrophilic modification of the Nylon-12 film was associated with the chemically bonded surface oxygen formed during DBD treatment.

In vitro studies of platelet adhesion on UV radiation-treated nylon surface

The aim of the study was to prepare a novel blood compatible of nylon film by grafting O-butyrylchitosan (OBCS). The immobilization was accomplished by irradiating with ultraviolet light, OBCS being coated on the film surface to photolyze azide groups, thus crosslinking OBCS and nylon together. Surface properties of nylon were investigated by attenuated total reflection Fourier transform infrared spectroscopy, electron spectroscopy for chemical analysis and water contact angle measurements. The blood compatibility of the OBCS-grafted nylon films was evaluated by platelet rich plasma contacting experiments and the results were observed by scanning electron microscopy. The blood compatibility of OBCS grafted nylon films seems better than that of blank nylon films. The modifications could be carried out to tailor nylon biomaterial to meet the specific needs of different biomedical applications. These results suggest that the blood compatible of nylon/OBCS films make them suitable biomaterials for some applications.

Scanning force microscopy study of the morphology of spin‐cast molecular‐imprinted nylon thin films

AbstractThe morphology of thin, selectively imprinted films of Nylon‐6 was investigated by scanning force microscopy. Four amino acids were used as template molecules in the spin‐cast films. Film thickness ranged from 2 µm to 500 nm, depending on the nylon and template concentration in the casting solution. The thin‐film properties, including the presence of nanometer‐ to micrometer‐sized pores, are clearly associated with the imprinting process. The larger features observed by scanning force microscopy are attributed to amino acid clustering during the casting process. Copyright © 2004 John Wiley & Sons, Ltd.

Radon permeability through nylon at various humidities used in the B orexino experiment

We have investigated the radon permeation through a nylon film at various humidities. The measurement method and the instrumentation applied, as well as a mathematical model of the 222Rn diffusion are described. The dependence of the radon diffusion, solubility and permeability coefficients for the nylon film on the relative ambient humidity and the nylon moisture content has been found. No significant change in these parameters was observed as the relative humidity was increased from 0% to 30%. However, in the range from 30% to 100% the radon permeability increases by about two orders of magnitude. In the range from 30% to 60%, which is of particular importance for B orexino, the 222Rn permeability is about one order of magnitude higher than it is through dry nylon.