Polyamide Nylon Research Articles

Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage

Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage

In Situ Compatibilizer Reinforced Interface between an Amorphous Polymer (Polystyrene) and a Semicrystalline Polymer (Polyamide Nylon 6)

We present an investigation of the reinforcement of the interface between a flexible amorphous polymer (polystyrene, PS) and a semicrystalline polymer (a polyamide, Ny6). Poly(styrene-co-maleic anhydride) was used as the compatibilizer. Fracture toughness was measured using the asymmetric double cantilever beam test (ADCB). For bonding temperatures above 190 °C, the adhesion strength was found to increase with bonding time, pass through a peak value, and then reach a plateau. The fracture toughness increased with increasing bonding temperature, passed through a peak near 200 °C, and then decreased with further increase of the bonding temperature. This behavior was more obvious for an amorphous polymer/semicrystalline polymer pair than for a pair of semicrystalline polymers. The variation of the fracture toughness with bonding time and temperature can be plausibly explained in terms of two different failure mechanisms: adhesive failure at the interface for short bonding times and when the bonding temperature is low, and for longer bonding times and at high temperatures, cohesive failure between chains at the interface and the bulk PS due to decreased chain entanglement. As long as the compatibilizer molecular weight is sufficiently large that entanglements form between the matrix polymers, common features of the fracture mechanisms depending on the bonding conditions can be outlined that are independent of the crystallinity of the polymer.

Catalytic effect of Fe/C powder on the formation of gas-phase products of vacuum pyrolysis of N,N′-ethylenebisstearamide

Abstract In the present work N,N′-ethylenebisstearamide (EBS) in its free form and mixed with iron/carbon powder was thermolyzed in a closed system under vacuum to produce gas-phase products (GPP). A catalytic effect of the iron/carbon surface on the gasification of thermolyzed EBS is observed over the 573–973 K temperature range. The overall yield of GPP measured after one hour of heating at a constant temperature increased with temperature (T The total yield, and the yields of the main identified GPP (CO, CH4, CO2 and C2H4), measured for free EBS are significantly lower (∼30 times) than those observed for mixture of EBS with iron/carbon powder. The catalytic formation of H2/N2, H2O and small amounts of other volatile 1 organic products is assumed at temperatures below 973 K. The formation of GPP from low volatility products of EBS decomposition is assumed to proceed via at least two competing mechanisms (EBS → Primary products → 2CO (1) or CO2 (2)). This mechanistical model can be used as a basis for understanding the delubrication mechanism of ferrous compacts and for the catalytic gasification of heavy amides (EBS) or polyamides (Nylon) widely used in industry.

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.

High-Yield Activation of Scaffold Polymer Surfaces To Attach Cell Adhesion Molecules

Zirconium tetra(tert-butoxide) reacts with surface amide groups of polyamide nylon 6/6 to give (eta(2)-amidate)zirconium complexes in high yield. These surface complexes react to bond the cell-adhesive peptide arginine-glycine-aspartic acid (RGD) to the polymer surface. A surface loading of 0.18 nmol/cm(2) of RGD is achieved, which is 20-1000 times higher than previously reported attainable on natural or synthetic polymers by other strategies. Approximately 40% of the nylon surface is covered by the RGD, which gives a surface that is both stable to hydrolysis and highly active for cell adhesion and spreading in vitro.

Free volume study of 70 MeV carbon induced modification in polymers through positron annihilation

Free volume properties of polymers have strong correlation with macroscopic properties and can be modified by radiations and ions. Positron annihilation lifetime spectroscopy (PALS) provide direct information about the dimension, content and size distribution of free volume holes in polymers. CR-39 (DOP), a polycarbonate widely used as ion track detector and polyamide Nylon-6, a high performance plastic having a unique combination of superior mechanical, electrical, chemical and thermal properties were irradiated with 70MeV C5+ ion beam to different fluences ranging from 1011 to 3.7×1013ions/cm2. The results of characterization by PALS are reported here. o-Ps lifetime and the average free volume for both the polymers are found to decrease with fluence, indicating the facilitation of cross-linking. The results are interpreted in terms of change in the free volume. Maximum change of 9.7% in average free volume was observed in PN-6 irradiated to 3.7×1013ions/cm2.

Hydration in a new semiaromatic polyamide observed by humidity‐controlled dynamic viscoelastometry and X‐ray diffraction

AbstractHydration in a new semiaromatic polyamide, named polyamide 9‐T (PA9‐T), a copolymer of terephthalic acid with n‐ and iso‐nonanediamines, is studied by dynamic viscoelastic analysis under controlled humidity conditions and wide‐angle X‐ray diffraction analysis in comparison with common polyamide nylon 6. The storage modulus of PA9‐T is retained at up to 60 °C with increasing humidity, then dropped with further increases in temperature past 70 °C. The decrease in mechanical properties at 70 °C due to moisture uptake is found to be substantially improved by annealing to develop molecular packing and/or crystallization. In contrast, the storage modulus of very highly crystallized (50% crystallinity) nylon 6 decreases markedly with humidity at low temperatures such as 20 °C. Thus, PA9‐T retains its mechanical properties in humid atmospheres at much higher temperatures than nylon 6. The crystalline X‐ray diffraction peaks for nylon 6 corresponding to (002) + (202) of the α form shift upon absorption of moisture, speculated to be due to the weakening of hydrogen bonds and the subsequent conformational disordering of the chains. Unlike nylon 6, the crystalline peaks of PA9‐T do not shift due to moisture uptake. This is considered to be attributable to that the long aliphatic chain in PA9‐T forms the large hydrophobic domain, rendering PA9‐T less hygroscopic than nylon 6. Additionally, strong hydrogen bonds formed by terephthalamide residues together with a strong stacking force of phenylene groups may also repel water, preventing moisture bind with the amide groups of PA9‐T crystals. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1640–1648, 2005

Mechanical properties of thermally cycled nylon bonded Nd-Fe-B permanent magnets

The effect of thermal cycling on the stress-strain behavior of polyamide (nylon) and polyphenylene-sulfide (PPS) based injection molded Nd-Fe-B magnets was investigated after test specimens were cycled between −40 and 150°C for 50, 500, or 5000 repetitions. It was found that PPS based magnets exhibit higher ultimate strengths, higher modulus and lower toughness than nylon based magnets. Furthermore, formulations containing platelet morphology particles exhibited higher strengths and modulus than those containing spherical morphology particles, with increases in particle volume fraction leading to a decrease in strength. Differences in strength, modulus, and toughness were attributed to the degree of bonding between the matrix and the magnet powder in the various formulations, the degree of crosslinking, along with the effects of powder morphology. Additionally, it was found that while the stiffness of these materials increased with thermal cycling, their toughness decreased significantly, by as much as 99%. The extent of these effects was found to be dependent on the polymer matrix, powder morphology, and volume fraction of powder in the magnet. Finally, it was found that the PPS composites showed less relative change due to thermal cycling than the Nylon composites.

Ion beam modification of CR-39 (DOP) and polyamide nylon-6 polymers

Swift heavy ions interact predominantly through inelastic scattering while traversing any polymeric medium and produce excited/ionized atoms. This results into the modification of physical and chemical response of the polymer. CR-39 (DOP) and polyamide nylon-6 polymer samples were irradiated with 70 MeV C 5+ ion beam to the fluences of 10 11, 10 12 and 10 13 ions cm −2. Modifications due to irradiation were studied using Fourier transform infra red (FTIR) spectroscopic and X-ray diffraction (XRD) technique. Considerable deformation has been observed in both the polymers at the fluence of 10 12 and 10 13 ions cm −2. XRD analyses show slight shift of peak position and significant changes in peak width and intensity. Particle size or grain size, calculated by applying Scherrer formula, indicates measurable changes in particle size in the irradiated samples. XRD peaks at d-values of 4.335 Å and 3.838 Å for the virgin polyamide nylon-6 gradually change with increasing fluence into one broad peak. Some difference in the irradiation effect in these two different polymers has been observed.

Reactive Blending of Polyamides with Different Carbonyl Containing Olefin Polymers

AbstractIn this paper the blending of polyamides nylon 6 and nylon 12, with a perfectly alternating ethylene/CO copolymer containing 50 mol‐% carbonyl groups (polyketone) is investigated in comparison to blends of the same polyamides with polyolefins containing varying degrees of carbonyl group incorporation. These include a poly[ethylene‐co‐(methyl acrylate)] copolymer containing 1.9 mol‐% methyl ester groups and poly[ethylene‐co‐(ethyl undecylenate)] copolymers with between 0.20 and 1.25 mol‐% ester incorporation. Blends were obtained of polyamides and the polyolefins in compositions between 20/80 and 80/20 in solution and in a Brabender mixer. SEM studies together with TGA, DSC and FTIR measurements show excellent compatibilization for both polyketone and poly[ethylene‐co‐(methyl acrylate)] copolymers with the nylons. The poly[ethylene‐co‐(ethyl undecylenate)] polymers displayed much less compatibilization although they still performed significantly better compared to pure polyethylene. The difference in compatibilization is discussed with respect to the importance of both the number of interactive groups present in the polyolefin and the steric requirements of hydrogen bond formation.SEM micrograph of the fracture surface of the blend nylon 6/polyethylene 70:30.magnified imageSEM micrograph of the fracture surface of the blend nylon 6/polyethylene 70:30.

UV Excimer laser modification on polyamide materials: effect on the dyeing properties

Polyamide (nylon 6) fabrics were irradiated with 193 nm ArF Excimer Laser and then dyed with commercially available acid, disperse and reactive dyes. The morphology of the irradiated surfaces was examined by scanning electron microscopy (SEM). Chemical surface changes of the materials were characterized by X-ray photoelectron spectroscopy (XPS) and change in cry-stallinity was examined by differential scanning calorimetry (DSC). Polyamide materials irradiated with laser developed ripple-like structures of micron size on the surface. These structures are strictly perpendicular to the stress direction of the fiber. It is worth noting that the dyeing properties of all dyes on polyamide fabrics changed remarkably after the treatment. The change in color is believed to be closely related with the appearance of ripple-like structures. Changes in chemical properties of the treated materials may also be one of the reasons for dyeability changes. This work suggests that the dyeing properties of disperse and reactive dyes on nylon can be improved after laser modification.

Laboratory aging studies for the HERA-B muon chambers

Abstract The severe radiation environment of the HERA-B experiment leads to a maximum accumulated charge on a wire, within the muon detector, of 200 mC/cm wire . For operation in this high-intensity environment, the main criteria for the gas choice turned out to be stability against aging. We report recent results of laboratory aging studies performed by irradiating proportional wire chambers filled with Ar/CF 4 /CH 4 (74:20:6), Ar/CF 4 /CH 4 (67:30:3), and Ar/CF 4 /CO 2 (65:30:5) mixtures. The penetration of water and oxygen through the walls of plastic tubes has also been investigated. Water can be introduced indirect to the gas mixture by using polyamide (nylon) pipes for gas supply lines.

Effect of thermal ageing on Nylon 6,6 fibres

The residual effects of thermal ageing at various temperatures on fibres of the aliphatic polyamide Nylon 6,6 have been studied. Both crystal and macro structural characteristics manifest the residual effects. The former category includes changes in intensity, 2θ values and half width. The macro changes include introduction of surface damages in the form of holes, material deposits etc. The fibre also undergoes reduction in weight. The structural changes suggest deterioration in the initial tensile characteristics which has been verified experimentally. A direct correlation between the tensile strength and the angular separation of the equatorial reflections has also been observed.

Synthesis, structure and crystal morphology of nylon 16

The new polyamide nylon 16 was produced by polycondensation of 16-aminohexadecanoic acid in bulk at 210°C. The monomer was obtained by ring-opening hydrolysis of 2-azacycloheptadecanone which was prepared from commercial 8-cyclohexadecen-1-one through a four-step synthesis route. The polymer has a molecular weight of 13 000 and melts at 164°C. Fiber X-ray diffraction and single crystal electron diffraction measurements revealed that nylon 16 crystallizes in a monoclinic lattice with the parameters a = 0.483 nm, b = 0.935 nm, c = 4.16 nm (chain axis), γ = 121° containing two chains in the unit cell. The packing for the chains was found to be similar to that described for the γ-form characteristic of nylons, whereas a crystal phase in the α-form was not observed. Lamellar crystals of nylon 16 grown in 2-octanol were examined by electron microscopy, and their structure and morphology is discussed in relation to the crystal model conventionally accepted for the γ-form of nylons.

Molecular Imprinting in Hydrogen Bonding Networks of Polyamide Nylon for Recongnition of Amino Acids

Abstract Molecularly imprinted Nylon-6 was prepared from the polymer solution of formic acid having l-glutamine template. The recognition of amino acids by l-glutamine imprinted-polymer was evaluated by binding experiments for l-glutamine and its analogues. It was revealed that the recognition was effective for l-glutamine by the imprinted polymer as compared with its racemate d-glutamine and l- or d-glutamic acid.

Interfacial interaction and peel adhesion between polyamide and acrylate rubber in thermoplastic elastomeric blends

The interfacial thickness, λ, and the adhesion strength of polyamide (nylon 6) and acrylate rubber (ACM) joints were measured by ellipsometry and a 180° peel adhesion test, respectively. Above 225°C, λ attained its equilibrium value very rapidly, which was ascribed to chemical interaction between nylon-6 and ACM in that temperature range. The possibility of reaction between the two polymers was confirmed by both infrared (IR) spectroscopy and solid-state 13C-NMR analysis and a probable mechanism of the reaction between nylon-6 and ACM was also proposed. The effects of the temperature of testing and the rate of separation on the adhesion strength of the joints were investigated. Dynamic mechanical thermal analysis of the joints annealed at 200°C for different times showed broadening of the loss tangent peak corresponding to that of ACM rubber with the progress of the reaction. Also, the storage modulus of the joints increased progressively, supporting better adhesion between the two polymers with increasing annealing time.

Rheological properties, crystallization, and morphology of compatibilized blends of isotactic polypropylene and polyamide

Blends of isotactic polypropylene (iPP) with the polyamide nylon-6 (N6), prepared by extrusion, were studied with a composition of up to 30% by weight polyamide. In the case of a 70/30 iPP/N6 blend, the influence of a compatibilizing agent based on polypropylene functionalized with maleic anhydride (PP-g-MA), with compositions of 1, 3, 5, and 10% by weight in polypropylene, was followed. The influence of the concentration of N6 and the compatibilizing agent on the rheological and thermal properties, and the morphology of the blends, was analyzed by monitoring the melt viscosity at different shear rates, differential scanning calorimetry, and polarized light microscopy. Vibrational spectroscopy was used to characterize the blends and to study the effect of the compatibilizing agent. The viscosity—composition curves for the iPP/N6 blends, in the composition and shear rate ranges analyzed, show a negative deviation from the additive rule, while the opposite trend is observed for the blends compatibilized with PP-g-MA. Important variations in the spectroscopic behavior was observed between compatibilized and noncompatibilized blends, which varied as a function of the compatibilizing agent concentration. The crystallization rates of iPP in the iPP/N6 blends, under both dynamic and isothermal conditions, are much greater than are those observed for pure iPP and are directly related to the nucleating activity of the polyamide. This effect is much smaller in the presence of the compatibilizing agent. The isothermal crystallization of the polyamide N6 in compatibilized blends is affected by the presence of iPP, reducing the crystallization rate due to the diluent effect of the polypropylene. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2665–2677, 1997

Improved blood compatibility of drawn polyamide sheets

A series of aliphatic polyamide (nylon) sheets with different draw ratios were prepared and their blood-contacting properties examined in relation to the bulk and surface characteristics. Increases in both the molecular orientation and crystallinity were observed with increasing draw ratio. Their surface wettability slightly decreased with draw ratio, indicating less amide linkages at their surfaces by the drawing process. An increase in contact angle hysteresis by the drawing process is thought to be due to the existence of more amorphous chains at the surfaces. The adsorption of albumin and fibrinogen onto nylon sheets was significantly reduced with draw ratio, suggesting the formation of well-established crystalline-amorphous microdomain structures at the surfaces. Blood compatibility of these surfaces was greatly improved with draw ratio in terms of a change in cytoplasmic calcium levels in platelets contacting these surfaces. Thus, it is suggested that the control of crystalline-amorphous microdomain structures by the drawing process is a feasible approach to improve blood compatibility of commercially available semicrystalline polyamides.

Morphology variety and formation mechanisms of polymeric membranes prepared by wet phase inversion

The cross-section morphologies of polymeric membranes obtained by scanning electron microscopy are presented. Membranes are prepared by a wet phase inversion process from cellulose acetate, polysulfone, polyester and a polyether type of elastomeric polyurethanes, poly(methylmethacrylate), and polyamide—nylon 4,6. Morphologies are qualitatively correlated with the turbidity appearance and its intensity during the (proto)membrane formation process and with their permeability to pure water. From the morphological characteristics, such as different cellular or dense structures, macrovoids, and polymer beads, and from the turbidity phenomena during the (proto)membrane formation, the nucleation and growth of polymer-lean or polymer-rich phase and the spinodal modes of polymer-solvent-nonsolvent ternary system decomposition are postulated. © 1996 John Wiley & Sons, Inc.

Analysis of the neurotoxic plasticizer n-butylbenzenesulfonamide by gas chromatography combined with accurate mass selected ion monitoring.

The plasticizer, n-butylbenzenesulfonamide (NBBS), is reported to be neurotoxic when inoculated intracisternally or intraperitoneally into rabbits. Because NBBS is commonly used in the production of polyamide (nylon) plastics and is soluble in water, the disposal of NBBS-containing plastics in landfill sites could result in NBBS appearing in the leachate. Further, NBBS could also be leached from packaging into their contents. To allow us to examine the risks posed by NBBS in the environment, we have developed a quantitative assay for this compound. The assay employs a one-step extraction into dichloromethane followed by gas chromatography with accurate mass selected ion recording. The assay incorporates [13C6]NBBS as an internal standard to allow precise quantitation, and four separate ion chromatograms are recorded. NBBS was found in some Australian domestic solidwaste landfill leachate (from less than 0.3 to 94.6 ng/mL), but ground water in the vicinity of a landfill had only trace quantities of NBBS. NBBS was also quantitated in some bottled and cask wines, and levels varied from not detected to 2.17 ng/mL (n = 14). Additional studies are required to assess the public health risks associated with the use of NBBS as a plasticizer.