Nylon

Distribution by Scientific Domains

Terms modified by Nylon

  • nylon clay nanocomposite
  • nylon membrane

  • Selected Abstracts


    The effect of temperature and ventilation condition on the toxic product yields from burning polymers

    FIRE AND MATERIALS, Issue 1 2008
    A. A. Stec
    Abstract A major cause of death or permanent injury in fires is inhalation of toxic gases. Moreover, every fire is unique, and the range of products, highly dependant on fire conditions, produces a wide variety of toxic and irritant species responsible for the most fire fatalities. Therefore, to fully understand each contribution to the toxicity it is necessary to quantify the decomposition products of the material under the test. Fires can be divided into a number of stages from smouldering combustion to early well-ventilated flaming through to fully developed under-ventilated flaming. These stages can be replicated by certain bench-scale physical fire models using different fuel-to-oxygen ratios, controlled by the primary air flow, and expressed in terms of the equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio). This work presents combustion product yields generated using a small-scale fire model. The Purser Furnace apparatus (BS7990 and ISO TS 19700) enables different fire stages to be created. Identification and quantification of combustion gases and particularly their toxic components from different fire scenarios were undertaken by continuous Fourier transform infrared spectroscopy. The relationship between type of the fire particularly the temperature and ventilation conditions and the toxic product yields for four bulk polymers, low-density polyethylene, polystyrene (PS), Nylon 6.6 and polyvinyl chloride (PVC) is reported. For all the polymers tested, except PVC, there is a dramatic increase in the yield of products of incomplete combustion (CO and hydrocarbons) with increase in equivalence ratio, as might be expected. For PVC there is a consistently high level of products of incomplete combustion arising both from flame inhibition by HCl and oxygen depletion. There is a low sensitivity to furnace temperature over the range 650,850C, except that at 650C PS shows an unexpectedly high yield of CO under well-ventilated conditions and PVC shows a slightly higher hydrocarbon yield. This demonstrates the dependence of toxic product yields on the equivalence ratio, and the lack of dependence on furnace temperature, within this range. Copyright 2007 John Wiley & Sons, Ltd. [source]


    A microwave-assisted process for coating polymer and glass surfaces with semiconducting ZnO submicron particles

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009
    Alexander Irzh
    Abstract A new method for coating glass slides with ZnO particles with an average size of 200 nm is proposed in the current article. The coating was performed under microwave radiation. Two main morphologies are found for the ZnO crystals that are deposited on glass slides. The first morphology is that of a very dense coating of ZnO hexagonal rods growing perpendicular to the glass surface. The second is the growth of ZnO flower-like particles. In addition to coating the glass by ZnO particles, we also report on coating other polymers [poly(methyl methacrylate) plate, polycarbonate beads, Nylon 6,6 beads, and polypropylene beads) by ZnO. The morphology obtained for ZnO coated on polymers is different from that detected for coating ZnO on glass. The unorganized coating of ZnO rods on polymers has been observed. The coated glass slides were characterized by X-ray diffraction, volumetric titration, EDS, scanning electron microscope, and optical measurements (DRS and transmittance spectroscopy). 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]


    Nonisothermal and isothermal crystallization kinetics of nylon-12

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
    Neil L. A. McFerran
    Abstract The isothermal and nonisothermal crystallization behavior of Nylon 12 was investigated using differential scanning calorimetry (DSC). An Avrami analysis was used to study the isothermal crystallization kinetics of Nylon 12, the Avrami exponent (n) determined and its relevance to crystal growth discussed and an activation energy for the process evaluated using an Arrhenius type expression. The Lauritzen and Hoffman analysis was used to examine the spherulitic growth process of the primary crystallization stage of Nylon 12. The surface-free energy and work of chain folding were calculated using a procedure reported by Hoffmann and the work of chain folding per molecular fold (,) and chain stiffness of Nylon 12 (q) was calculated and compared to values reported for Nylons 6,6 and 11. The Jeziorny modification of the Avrami analysis, Caz and Chuah average Avrami parameter methods and Ozawa equation were used in an attempt to model the nonisothermal crystallization kinetics of Nylon 12. A combined Avrami and Ozawa treatment, described by Liu, was used to more accurately model the nonisothermal crystallization kinetics of Nylon 12. The activation energy for nonisothermal crystallization processes was determined using the Kissinger method for Nylon 12 and compared with values reported previously for Nylon 6,6 and Nylon 11. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


    Effect of Pasteurization, High-Pressure Processing, and Retorting on the Barrier Properties of Nylon 6, Nylon 6/Ethylene Vinyl Alcohol, and Nylon 6/Nanocomposites Films

    JOURNAL OF FOOD SCIENCE, Issue 1 2009
    L. Halim
    ABSTRACT:, This study determined the impact of pasteurization, high-pressure processing (HPP), and retorting on the barrier properties of nylon 6 (N6), nylon 6/ethylene vinyl alcohol (N6/EVOH), and nylon 6/nanocomposite (N6/nano) materials. The pasteurized and high-pressure treated films were coextruded with low-density polyethylene (PE) as the heat-sealing layer. The retorted films were coextruded with polypropylene (PP). Oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the samples were measured after pasteurization (75 C for 30 min), HPP (800 MPa for 10 min at 70 C), and retorting (121 C for 30 min) treatments. These were compared with the thermal characteristics and morphologies of the samples using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Results showed that OTR of N6 and N6/Nano increased after HPP (16.9% and 39.7%), pasteurization (13.3% and 75.9%), and retorting (63.3% and 112.6%), respectively. For N6/EVOH, a decrease in OTR after HPP (53.9%) and pasteurization (44.5%) was observed. The HPP treatment increased the WVTR of N6 (21.0%), N6/EVOH (48.9%), and N6/Nano (21.2%). The WVTR of N6, N6/EVOH, and N6/Nano increased by 96.7%, 43.8%, and 40.7%, respectively, after pasteurization. The DSC analyses showed that the enthalpy and percent crystallinity increased (2.3% to 6.5%) in the N6/Nano when compared with the N6 material after each treatment. Retorting caused a decrease (3.5%) in the percent crystallinity of the polypropylene material. HPP did not cause major morphological changes to the samples. Results of the barrier studies were influenced by the crystallinity changes in the materials as seen in the XRD diffractograms. [source]


    On the Lamellar Crystal Structure of Nylons 6,8 and 8,10: A Study Combining Electron Microscopy and Energy Analysis

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2003
    Marta Bermdez
    Abstract Lamellar crystals of nylon 6,8 and nylon 8,10 with chains in a fully extended conformation were obtained by crystallization in solution, and examined by electron and X-ray diffraction. The same crystal structure appeared to be shared by both nylons crystallized in glycerin. This structure consisted of a mixture of ,- and ,-forms with features similar to that previously described for lamellar crystals of nylon 4,6 grown in the same solvent. Crystallization of nylon 8,10 in hexane-2,5-diol afforded lamellar crystals with sheets stacked in the ,-form. A comparative energy evaluation of the different models that are feasible for the crystal structure of these nylons with fully extended chains indicated very small energy differences among them. The presence of different chain arrangements in the same lamellar crystal, as well as the crystallization of the same nylon in different crystal forms upon slight modification of the crystallization conditions, are fully consistent, therefore, with the results obtained in the energy analysis. Nylon 8,10 crystals grown in hexane-2,5-diol at 150,C. Inset: The respective electron diffraction patterns. [source]


    A Novel Impact Modifier for Nylon 6

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2002
    Jing Peng
    Abstract A new carboxylated styrene-butadiene rubber (CSBR) in ultrafine powder form was used to modify the properties of nylon 6. The nylon 6/CSBR blends possessed higher toughness than nylon 6/maleic anhydride-grafted polyethylene-octene elastomer (POE- g -MAH) system. TEM micrographs revealed the fine dispersion of CSBR particles with a diameter of 150 nm. The effective toughening of nylon 6 with CSBR was attributed to the good interface, fine dispersion, and shear yielding. TEM photograph of undeformed Nylon 6/CSBR (80/20) blend (40,000). [source]


    Carbon Nanotube-Adsorbed Electrospun Nanofibrous Membranes of Nylon 6

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2006
    Hyun Suk Kim
    Abstract Summary: A simple and mass-producible method was developed to densely assemble multiwalled carbon nanotubes (MWNTs) onto electrospun nylon 6 nanofibrous membranes. The process consists of dispersing the acid-treated MWNTs in surfactant solutions or organic solvents, and dipping the nanofibrous membranes in the resulting dispersion for only 60 seconds, followed by the extraction of the surfactants in pure water and drying. The conductivity of the MWNT-adsorbed nanofibrous membranes ranges from 2.2,,10,2 to 1.5,,10,1 S,,cm,1, as determined by the four probe method, which implies that the MWNTs are adsorbed uniformly and densely along the nanofibrous membranes. Furthermore, the results suggest that there is a strong interaction between the acid-treated MWNTs and nylon 6. We also investigate the amount of MWNTs present in the membranes using thermogravimetric analysis. SEM images of the non-woven fibrous nylon 6 membranes after dip-coating in a dispersion of the MWNTs in surfactant-containing water. [source]


    Mechanistic Investigation into the Unique Orientation Textures of Poly(vinylidene fluoride) in Blends with Nylon 11

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2003
    Yongjin Li
    Abstract Self-seeded crystallization experiments were carried out to detect the mechanism of the unique orientation behavior of poly(vinylidene fluoride) (PVDF) in oriented PVDF/nylon 11 blends. It was found that primary nuclei have no effects on the final orientation textures adopted by PVDF. The results show that the PVDF crystal orientation in the oriented blends is determined in the early stage of crystal growth, thus a trans crystallization mechanism is preferred. Isothermal crystallization kinetics for the self-seeded and non-self-seeded crystallization at 145,C. [source]


    Thermal Degradation Kinetics of Nylon 66: Experimental Study and Comparison with Model Predictions

    MACROMOLECULAR REACTION ENGINEERING, Issue 5 2007
    Mark A. Schaffer
    Abstract An experimental investigation of nonoxidative thermal degradation kinetics of nylon 66 melt under high temperature (280,300,C) and low water content (0.02,0.14 wt.-%) conditions is presented. Experimental data for the time evolution of polymer end-group concentrations and degradation-product generation rates were compared with the predictions of the only published kinetic model. The omitted influence of water content is a plausible partial explanation for the considerable discrepancy between model predictions and some data. Several previously unreported or unquantified degradation products were identified and measured. Potential additional reactions to account for these results in future kinetic models are proposed. [source]


    Solving multi-objective dynamic optimization problems with fuzzy satisfying method

    OPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 5 2003
    Cheng-Liang Chen
    Abstract This article proposes a novel algorithm integrating iterative dynamic programming and fuzzy aggregation to solve multi-objective optimal control problems. First, the optimal control policies involving these objectives are sequentially determined. A payoff table is then established by applying each optimal policy in series to evaluate these multiple objectives. Considering the imprecise nature of decision-maker's judgment, these multiple objectives are viewed as fuzzy variables. Simple monotonic increasing or decreasing membership functions are then defined for degrees of satisfaction for these linguistic objective functions. The optimal control policy is finally searched by maximizing the aggregated fuzzy decision values. The proposed method is rather easy to implement. Two chemical processes, Nylon 6 batch polymerization and Penicillin G fed-batch fermentation, are used to demonstrate that the method has a significant potential to solve real industrial problems. Copyright 2003 John Wiley & Sons, Ltd. [source]


    Dynamic mechanical properties of extruded nylon,wood composites

    POLYMER COMPOSITES, Issue 4 2008
    Jianmin Chen
    Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon,wood composite in under-the-hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon,wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (Tg), physical aging effects, long-term performance prediction, and comparisons to similar products. The storage modulus of the nylon,wood composite was found to be more temperature stable than pure nylon 66. The Tg range of the nylon,wood composite was found to be between 23 and 56C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon,wood composites have good temperature-dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon,wood composite with other similar products shows that nylon,wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. 2008 Society of Plastics Engineers [source]


    Melt processing and characterization of multicomponent polymeric nanocomposites containing organoclay

    POLYMER COMPOSITES, Issue 3 2007
    M. Letuchi
    Nylon 6 (Ny)/polypropylene (PP)/maleated polypropylene (PP- g -MA)/organoclay/wollastonite composites were prepared by melt processing. The polymers' composition was kept constant ([70PP/30Ny]/4PP- g -MA). Melt compounding was conducted using a twin-screw extruder in three different methods: (1) simultaneous incorporation of the components into the compounding equipment, (2) preparation of [Ny6/clay] concentrate, and then in a second step, mixing the other components with the concentrate, and (3) mixing of PP with wollastonite and clay followed by the addition of Ny6 and PP- g -MA in the second step. Injection-molded specimens were characterized in tension, scanning electron microscopy, X-ray diffraction (XRD), and differential scanning calorimetry. The sequence of component addition greatly influences the structure and properties of the composites. Enhanced mechanical properties were achieved when the two-step mixing procedure was used for the PP/Ny6/PP- g -MA/clay system (method 2) and also for the PP/Ny6/PP- g -MA/clay/wollastonite system (method 3). The XRD pattern of the PP/Ny6/PP- g -MA/clay nanocomposites produced by the two-step mixing method does not show a characteristic basal reflection of the pristine organoclay, indicating a predominately exfoliated structure of clay. POLYM. COMPOS., 28:417,424, 2007. 2007 Society of Plastics Engineers [source]


    Morphology, thermal, and rheological behavior of nylon 11/multi-walled carbon nanotube nanocomposites prepared by melt compounding

    POLYMER ENGINEERING & SCIENCE, Issue 6 2009
    Shu Huang
    Nylon 11 (PA11) nanocomposites with different loadings of multi-walled carbon nanotubes (MWNTs) were prepared by melt compounding. Scanning electron microscopy images on the fracture surfaces of the composites showed a uniform dispersion of MWNTs throughout the matrix. The presence of the MWNTs significantly improved the thermal stability and enhanced the storage modulus (G,) of the polymer matrix. Melt rheology studies showed that, compared with neat PA11, the incorporation of MWNT into the matrix resulted in higher complex viscosities (|,*|), storage modulus (G,), loss modulus (G,), and lower loss factor (tan,). PA11 and its nanocomposites containing less than 1 wt% MWNTs showed similar frequency dependencies and reached a Newtonian plateau at low frequencies. For the nanocomposite with 2 wt% MWNTs, the regional network was destroyed and the orientation of the MWNTs during shearing exhibited a very strong shear thinning effect. The complex viscosities (|,*|) of the nanocomposites are larger than that of neat PA11 and decreased with increasing the temperature. POLYM. ENG. SCI., 2009. 2009 Society of Plastics Engineers [source]


    Effect of melt processing conditions on the morphology and properties of nylon 6 nanocomposites

    POLYMER ENGINEERING & SCIENCE, Issue 11 2007
    F. Chavarria
    Nylon 6 (PA-6) organoclay nanocomposites were prepared by melt processing using three different twin screw extruders (TSEs). The effect of mixing conditions, feed port location, residence time, and number of extrusion passes on the morphology and mechanical properties of the nanocomposites were examined. Wide-angle X-ray scattering, transmission electron microscopy (TEM), and mechanical property data are reported. Particle analyses were performed on the TEM images to quantitatively characterize the extent of exfoliation. The amount of shear and the mixing conditions created by TSEs have a significant effect on the morphology and properties of PA-6 nanocomposites. Morphology and mechanical property results show that (1) melting the polymer before coming into contact with the organoclay followed by a low level of shear and (2) maintaining a medium level of shear throughout the extruder with a longer residence time lead to extremely high platelet dispersion and matrix reinforcement for PA-6 nanocomposites. Nanocomposites formed in a DSM microcompounder showed similar morphologies and modulus trends as those obtained with conventional TSEs; thus, this microcompounder is a good alternative for nanocomposite research especially when only small amounts of material are available. POLYM. ENG. SCI., 47:1847,1864, 2007. 2007 Society of Plastics Engineers [source]


    Isothermal and nonisothermal crystallization kinetics of nylon 10 12

    POLYMER ENGINEERING & SCIENCE, Issue 9 2000
    Yongjin Li
    This article studied the crystallization behaviors of a newly industrialized polyamide, Nylon 10 12, under isothermal and nonisothermal conditions from the melt. A differential scanning calorimeter (DSC) was used to monitor the energetics of the crystallization process. During isothermal crystallization, relative crystallinity develops in accordance with the time dependence described by the Avrami equation with the exponent n=2.0. For nonisothermal studies, several different analysis methods were used to describe the crystallization process. The experimental results show that the Ozawa approach cannot adequately describe the nonisothermal crystallization kinetics. However, Avrami treatment for nonisothermal crystallization is able to describe the system very well. The calculated activation energy is 264.4 KJ/mol for isothermal crystallization by Arrhenius form and 235.5 KJ/mol for nonisothermal crystallization by Kissinger method. [source]


    Mechanical and dynamic mechanical properties of nylon 66/montmorillonite nanocomposites fabricated by melt compounding

    POLYMER INTERNATIONAL, Issue 8 2004
    Zhong-Zhen Yu
    Abstract Nylon 66 nanocomposites were prepared by melt compounding of nylon 66 with organically modified montmorillonite (MMT). The organic MMT was pre-modified with about 14 wt% of ammonium surfactant, much lower than the 35,46 wt% in most commercial organic MMT powders. Transmission electron microscope observation indicated that the MMT layers were well exfoliated in nylon 66 matrix. Dynamic mechanical analysis confirmed the constraint effect of exfoliated MMT layers on nylon 66 chains, which benefited the increased storage modulus, increased glass transition temperature and reduced magnitude of alpha relaxation peak. The effects of organic MMT loading levels on reinforcement and fracture behaviour of the nanocomposites were evaluated using tensile and three-point bending tests. The addition of the organic MMT clearly increased Young's modulus and tensile strength but decreased ductility and fracture toughness of nylon 66. Copyright 2004 Society of Chemical Industry [source]


    Semi-online nanoflow liquid chromatography/matrix-assisted laser desorption ionization mass spectrometry of synthetic polymers using an octadecylsilyl-modified monolithic silica capillary column

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2010
    Takehiro Watanabe
    We have designed a semi-online liquid chromatography/matrix-assisted laser desorption/ionization mass spectrometry (LC/MALDI-MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI-MS analysis. Our novel semi-online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,-hexafluoroisopropyl alcohol (HFIP), to be used to achieve cost-effective analysis. Using the semi-online LC/MALDI-MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size-exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed-phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI-MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size-exclusion separation; the reversed-phase separation by interaction with the ODS functions may have less influence on column separation. The semi-online monolithic capillary LC/MALDI-MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright 2010 John Wiley & Sons, Ltd. [source]


    Failed vasectomy reversal: is a further attempt using microsurgery worthwhile?

    BJU INTERNATIONAL, Issue 4 2000
    M. Fox
    Objective To determine, in failed vasectomy reversal, the usefulness of a revised anastomosis using microsurgery in achieving sperm in the ejaculate and fertility, and to relate the outcome to the site of the anastomosis, length of time from vasectomy, and presence or absence of sperm in the vas at surgery. Patients and methods In a series of 28 patients with confirmed anastomotic obstruction undergoing vasectomy reversal (over a 10-year period), a microsurgical technique using an oblique end-to-end two-layer interrupted anastomosis with 10/0 Nylon was used to establish vasal continuity. Subsequent seminal analysis at 3,6 months and ensuing paternity were related to several variables. The results were compared with those obtained after 137 cases of primary microsurgical vasovasostomy. Results Sperm was restored to the ejaculate in 16 (57%) of the patients and successful fertilization was reported in nine (32%). The interval between vasectomy and reversal surgery was relevant to the outcome, with four out of four men having sperm in the ejaculate within 5 years and three achieving paternity. However, the fertility rate was still moderate after an interval of 6,10 years (two of six) and at > 10 years (four of 18). The presence of sperm in the ejaculate was related to whether or not sperm were found in the testicular end of the vas at operation, but absence did not preclude a successful outcome. The overall results were not significantly different from those after primary microsurgical reversal surgery. Conclusion Microscopic vasovasostomy after previous obstructive failure provides the patient with a further reasonable chance of becoming fertile; although diminishing with time from vasectomy, even after a prolonged period there can be success. The absence of sperm at the time of vasovasostomy does not necessarily indicate failure, but in these cases the presence of thick creamy fluid in the vas predicts a poor outcome, and alternative methods of management should be considered. A microsurgical technique extending, if necessary, well into the convoluted part of the vas, is recommended. Microsurgical skills, relevant equipment and adequate time are required. [source]


    ChemInform Abstract: Studies on Synthesis of 2-Methyl-3,1-benzoxazine-4(4H)-one Dyes and Their Application on Nylon and Polyester Fibres.

    CHEMINFORM, Issue 16 2010
    H. D. Navadiya
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Nonisothermal and isothermal crystallization kinetics of nylon-12

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
    Neil L. A. McFerran
    Abstract The isothermal and nonisothermal crystallization behavior of Nylon 12 was investigated using differential scanning calorimetry (DSC). An Avrami analysis was used to study the isothermal crystallization kinetics of Nylon 12, the Avrami exponent (n) determined and its relevance to crystal growth discussed and an activation energy for the process evaluated using an Arrhenius type expression. The Lauritzen and Hoffman analysis was used to examine the spherulitic growth process of the primary crystallization stage of Nylon 12. The surface-free energy and work of chain folding were calculated using a procedure reported by Hoffmann and the work of chain folding per molecular fold (,) and chain stiffness of Nylon 12 (q) was calculated and compared to values reported for Nylons 6,6 and 11. The Jeziorny modification of the Avrami analysis, Caz and Chuah average Avrami parameter methods and Ozawa equation were used in an attempt to model the nonisothermal crystallization kinetics of Nylon 12. A combined Avrami and Ozawa treatment, described by Liu, was used to more accurately model the nonisothermal crystallization kinetics of Nylon 12. The activation energy for nonisothermal crystallization processes was determined using the Kissinger method for Nylon 12 and compared with values reported previously for Nylon 6,6 and Nylon 11. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


    On the Lamellar Crystal Structure of Nylons 6,8 and 8,10: A Study Combining Electron Microscopy and Energy Analysis

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2003
    Marta Bermdez
    Abstract Lamellar crystals of nylon 6,8 and nylon 8,10 with chains in a fully extended conformation were obtained by crystallization in solution, and examined by electron and X-ray diffraction. The same crystal structure appeared to be shared by both nylons crystallized in glycerin. This structure consisted of a mixture of ,- and ,-forms with features similar to that previously described for lamellar crystals of nylon 4,6 grown in the same solvent. Crystallization of nylon 8,10 in hexane-2,5-diol afforded lamellar crystals with sheets stacked in the ,-form. A comparative energy evaluation of the different models that are feasible for the crystal structure of these nylons with fully extended chains indicated very small energy differences among them. The presence of different chain arrangements in the same lamellar crystal, as well as the crystallization of the same nylon in different crystal forms upon slight modification of the crystallization conditions, are fully consistent, therefore, with the results obtained in the energy analysis. Nylon 8,10 crystals grown in hexane-2,5-diol at 150,C. Inset: The respective electron diffraction patterns. [source]


    Structural Phase Transitions of Aliphatic Nylons Viewed from the Simultaneous Measurements of WAXD and SAXS

    MACROMOLECULAR SYMPOSIA, Issue 1 2006
    Kohji Tashiro
    Abstract Structural changes occurring in the high temperature region of doubly-oriented nylon 10/10 sample have been investigated through the temperature-dependent simultaneous measurements of wide-angle and small-angle X-ray scatterings, and the results were compared with the infrared spectral data as well as the molecular dynamics simulation results. In the Brill transition region of 150,180,C the methylene segments are conformationally disordered with keeping the intermolecular hydrogen bonds. During this phase transition the stacked lamellar structure did not change very much: the lamellae are tilted by ca. 34 from the draw axis and the long period is almost 160 . In the temperature region immediately below the melting point the molecular chains were found to be contracted by ca. 10% the original repeating period and the intermolecular hydrogen bonds were almost broken, causing the violent rotational and translational motions of the chains around the chain axis. At the same time the long period increased remarkably from 160 to 410 and the originally tilted lamellae stood up in parallel to the draw axis. [source]


    Quality of orange juice in barrier packaging material

    PACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2008
    C. Berlinet
    Abstract The vitamin C content and the colour of orange juice made from concentrate were measured during 9 months of storage at 20C either under artificial light or in darkness. The packaging materials used were glass, standard monolayer polyethylene terephthalate (PET) and multilayer PET (PET/nylon and oxygen scavenger/PET) containers. In this experiment, all bottles were sealed with aluminium foil in order to avoid any cap effect. The results showed that in plastic packaging materials, the loss of vitamin C was related to the oxygen permeability, and that glass provided the best preservation of ascorbic acid. No statistical difference (p < 0.05) was revealed between the vitamin C content in the juice stored under artificial light or in darkness, whatever the packaging used. The modification of colour was studied with the L, a* and b* values during storage at 20C under artificial light. L and b* decreased, revealing a reduction of lightness and yellow colour of the juice, whereas a* increased, due to the formation of brown pigments. This change in colour was partly related to the oxygen permeability of the packaging used. The losses of aroma compounds by permeation through the bottle (PET) and the cap (high-density polyethylene, HDPE) have also been investigated. The results showed that permeation mainly took place through the cap. The use of a multilayer cap [HDPE with internal barrier layer of low-density polyethylene (LDPE)/EvOH/LDPE] considerably limited the permeation of the aroma compounds studied, whatever the PET bottle used. Copyright 2007 John Wiley & Sons, Ltd. [source]


    Mechanistic Investigation into the Unique Orientation Textures of Poly(vinylidene fluoride) in Blends with Nylon 11

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2003
    Yongjin Li
    Abstract Self-seeded crystallization experiments were carried out to detect the mechanism of the unique orientation behavior of poly(vinylidene fluoride) (PVDF) in oriented PVDF/nylon 11 blends. It was found that primary nuclei have no effects on the final orientation textures adopted by PVDF. The results show that the PVDF crystal orientation in the oriented blends is determined in the early stage of crystal growth, thus a trans crystallization mechanism is preferred. Isothermal crystallization kinetics for the self-seeded and non-self-seeded crystallization at 145,C. [source]


    Frequency of Use of Suturing and Repair Techniques Preferred by Dermatologic Surgeons

    DERMATOLOGIC SURGERY, Issue 5 2006
    BETH ADAMS MD
    BACKGROUND There are many closure techniques and suture types available to cutaneous surgeons. Evidence-based data are not available regarding the frequency of use of these techniques by experienced practitioners. OBJECTIVE To quantify, by anatomic site, the frequency of use of common closure techniques and suture types by cutaneous surgeons. METHOD A prospective survey of the members of the Association of Academic Dermatologic Surgeons that used length-calibrated visual-analog scales to elicit the frequency of use of specific suture techniques. RESULTS A response rate of 60% (61/101) indicated reliability of the received data. Epidermal layers were closed most often, in descending order, by simple interrupted sutures (38,50%), simple running sutures (37,42%), and vertical mattress sutures (3,8%), with subcuticular sutures used more often on the trunk and extremities (28%). The most commonly used superficial sutures were nylon (51%) and polypropylene (44%), and the most common absorbable suture was polyglactin 910 (73%). Bilayered closures, undermining, and electrocoagulation were used, on average, in 90% or more sutured repairs. The median diameters (defined as longest extent along any axis) of most final wound defects were 1.1 to 2.0 cm (56%) or 2.1 to 3.0 cm (37%). Fifty-four percent of wounds were repaired by primary closure, 20% with local flaps, and 10% with skin grafting, with the remaining 15% left to heal by second intent (10%) or referred for repair (5%). Experience-related differences were detected in defect size and closure technique: defects less than 2 cm in diameter were seen by less experienced surgeons, and defects greater than 2 cm by more experienced surgeons (Wilcoxon's rank-sum test: p=.02). But more experienced surgeons were less likely to use bilayered closures (r=,0.28, p=.036) and undermining (r=,0.28, p=.035). CONCLUSIONS There is widespread consensus among cutaneous surgeons regarding optimal suture selection and closure technique by anatomic location. More experienced surgeons tend to repair larger defects but, possibly because of their increased confidence and skill, rely on less complicated repairs. [source]


    A further study of factors affecting pneumatic-impact ignition of polymers

    FIRE AND MATERIALS, Issue 6 2006
    Fu-Yu Hshieh
    Abstract One likely cause of polymer ignition in high-pressure oxygen systems is the adiabatic-compression heating of polymers caused by pneumatic impact. The previous study showed that pneumatic-impact ignition of polymers could be initiated by a local heterogeneous reaction between the hot oxygen and the oxidation sites of the polymer. This study further investigates other factors that cause pneumatic-impact ignition of polymers in high-pressure oxygen. Because the oxygen concentration has a significant effect on pneumatic-impact ignition, threshold oxygen concentrations for pneumatic-impact ignition of six selected polymers were determined at 20.7 MPa (3000 psia), an expected service pressure in high-pressure oxygen systems. The six polymers investigated were: Teflon PTFE (polytetrafluoroethylene), Neoflon CTFE (polychlorotrifluoroethylene), PEEK (polyetheretherketone), Zytel 42 (nylon 6/6), Buna N (acrylonitrile butadiene rubber), and Viton A (copolymer of vinylidene fluoride and hexafluoropropylene). The results show that PEEK exhibited the highest threshold oxygen concentration (65%) and Zytel 42 exhibited the lowest threshold oxygen concentration (<21%). Copyright 2006 John Wiley & Sons, Ltd. [source]


    How Interface innovates with suppliers to create sustainability solutions

    GLOBAL BUSINESS AND ORGANIZATIONAL EXCELLENCE, Issue 6 2009
    Eric Nelson
    Becoming a sustainable and restorative company can mean rethinking the basic components of your products. This leading carpet manufacturer's innovations, including those developed in collaboration with key suppliers, have changed the industry and moved the company closer to its sustainability goals. The author explains the company's seven areas of sustainability focus, and the role innovation plays in reducing its negative impact on the environment. He then describes Interface's approach for building supplier commitment and participation in these goals, and examines the firm's partnership with Universal Fibers, which led to the first commercially viable processes for incorporating postindustrial and postconsumer nylon in carpet facing and for salvaging old carpet from end-of-life disposal and recycling it into materials for new carpet production. 2009 Wiley Periodicals, Inc. [source]


    Natural convection heat transfer along a vertical flat plate with a projection in the turbulent region

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2001
    Katsuo Komori
    Abstract In the present study, the heat transfer coefficients occurring with a projection in the turbulent region of a vertical flat plate were measured experimentally for various projection heights in the range of 0 to 20 mm. The wall temperature and fluid flow fields were also visualized using a liquid crystal sheet and nylon 12 powder, respectively. The average and local Nusselt numbers reach 1.07 to 1.22 and 1.2 to 1.7 times those for pure turbulent natural convection, respectively. The maximum enhancement rates of heat transfer are attained at a position of 2.3 to 3.3 times the projection height from the upper projection surface toward the downstream, and these positions are in good agreement with those of the reattachment of the fluid flow and with centers of dark red regions in the liquid crystal. On the other hand, the heat transfer coefficients in the just upstream and downstream regions of the projection are small compared with those for no projection. By introducing the nondimensional parameter R, the present experimental results are rearranged quantitatively and effectively. 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 222,233, 2001 [source]


    Electrical and thermal properties of nylon 6/calcium carbonate composites

    ADVANCES IN POLYMER TECHNOLOGY, Issue 4 2009
    M. A. Moussa
    Abstract Several polymer composites formed from nylon 6/CaCO3 with different ratios and particle sizes were prepared using modified and unmodified CaCO3 as inorganic filler. The modification of CaCO3 surfaces was carried out by adsorption of oleic acid from toluene. TGA and DSC measurements show that the glass transition temperatures reduced by the presence of inorganic filler, whereas the melting temperature did not influenced. In all prepared polymer composites, the presence of filler accelerates the degradation process of the polymer. Dielectric properties of the investigated samples were studied in the frequency range from 45 Hz to 1 MHz and at temperatures ranging between 50 and 200C. The presence of CaCO3 led to a remarkable decrease in the conductivity of nylon 6. 2010 Wiley Periodicals, Inc. Adv Polym Techn 28:257,266, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20165 [source]


    Synergistic effects of carbon fillers on shielding effectiveness in conductive nylon 6,6- and polycarbonate-based resins

    ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2003
    Quinton J. Krueger
    Abstract Electrically conductive resins can be made by adding electrically conductive fillers to typically insulating polymers. Resins with an electrical resistivity of approximately 100 , cm or less can be used for electromagnetic and radio frequency interference shielding applications. This research focused on performing compounding runs followed by injection molding and shielding effectiveness (SE) testing of carbon filled nylon 6,6- and polycarbonate-based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch-based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 23 factorial design and a complete replicate in each polymer. The objective of this study was to determine the effects and interactions of each filler on the SE properties of the conductive resins. Carbon black caused the largest increase in SE. Also, each single filler and each two filler interaction caused a statistically significant increase in SE. 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 96,111, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10040 [source]