Polyamide Nylon Research Articles

Building a resistance to ignition testing device for sunglasses and analysing data: a continuing study for sunglasses standards

BackgroundSunglasses popularity skyrocketed since its advent. The ongoing trend led to the creation of standards to protect consumers from injuries and secondary hazards due to spectacles use. In Brazil, the corresponding standard is NBR ISO 12312-1:2015 and since there is no mandatory testing, evaluating sunglasses performance provides an insight into compliance with the standard. In a continuing revision of sunglasses standards requirements, resistance to ignition is one of the concerns, since sunglasses should be protected from burning into flames at a pre-determined temperature, which may protect user of getting their sunglasses into flames if some, cigarette sparks reaches the spectacles, as an example. This paper describes the building of a resistance to ignition system and the results of 410 samples that have been tested accordingly to ISO 12312-1.MethodsThe procedure is in accordance with the resistance to ignition test. It consists of heating a steel rod to 650 °C and pressing it against the sample surface for 5 s, with a force equivalent to the rod weight. For carrying out the assessments, we have build resistance to ignition testing system and assured the testing requirements of the standard. The apparatus has an electrical furnace with a temperature acquisition circuit and electronic control that maintains the temperature of the steel rod at 650 °C. A linear actuator was designed for the project to drive the steel rod vertically and pressing it against the sunglasses samples. The control system is composed by a Freescale development board FRDM-KL25Z with an ARM Cortex-M0 embedded. We have also provided a LabView PC interface for acquiring, displaying, and storing data as well as added a physical control panel to the equipment for performing the evaluations. We assessed 410 sunglasses frames at the built apparatus, where the 410 lenses came out to be in accordance with the guidelines provided by the ignition to resistance test. Out of the 410 tested frames, 50% were made of polyamide (nylon 12); 10% were made of polyamide (nylon 11, mamona oil); 5% were made of cellulose acetate; 15% were made of ABS and 20% were made of polycarbonate. Out of the 410 tested lenses, 80% were polycarbonate; 2% were polymethyl methacrylate (PMMA); 5% CR-39 (with polarizing filter inside); 12.8% polyamide; 0.2% glass.ResultsFor all the 410 tested spectacles frames and lenses, none burst into flames or continued to melt at the end of the procedure, being in compliance with ISO 12312-1:2013.ConclusionsThe evidences show that all the tested thermoplastic and thermosetting materials are exceptionally resistant to ignition and all samples assessed comply with the resistance to ignition test. The analysis of the sunglasses made herein assures that most of sunglasses currently available to population are made of safe material.

Training model for control of an internal carotid artery injury during transsphenoidal surgery.

As the adoption of endoscopic endonasal approaches (EEA) continues to proliferate, increasing numbers of internal carotid artery (ICA) injuries are reported. The objective of this study was to develop a synthetic ICA injury-training model that could mimic this clinical scenario and be portable, repeatable, reproducible, and without risk of biological contamination. Based on computed tomography of a human head, we constructed a synthetic model using selective laser sintering with polyamide nylon and glass beads. Subsequently, the model was connected to a pulsatile pump using 6-mm silicon tubing. The pump maintains a pulsatile flow of an artificial blood-like fluid at a variable pressure to simulate heart beats. Volunteer surgeons with different levels of training and experience were provided simulation training sessions with the models. Pre- and posttraining questionnaires were completed by each of the participants. Pre- and posttraining questionnaires suggest that repeated simulation sessions improve the surgical skills and self-confidence of trainees. This ICA injury model is portable; reproducible; and avoids ethical, biohazard, religious, and legal problems associated with cadaveric models. A synthetic ICA injury model for EEA allows recurring training that may improve the surgeon's ability to maintain endoscopic visualization, control catastrophic bleeding, decrease psychomotor stress, and develop effective team strategies to achieve hemostasis. NA Laryngoscope, 127:38-43, 2017.

Sustainable Chiral Polyamides with High Melting Temperature via Enhanced Anionic Polymerization of a Menthone-Derived Lactam.

Polyamides are very important polymers that find applications from commodities up to the automotive and biomedical sectors, and their impact is continuously growing. The synthesis of structurally significant, chiral, and sustainable polyamides is described via a new, convenient, and solvent-free anionic polymerization of a biobased ε-lactam, which is obtained from the renewable terpenoid ketone l-menthone in a one-step synthesis. These polyamides are shown to have outstanding structural and thermal properties, which are thus introduced via the structure and chirality of the natural lactam monomer and which are discussed and compared with those of petroleum-based, established, and commercial polyamide Nylon-6. X-ray data reveal a remarkable degree of crystallinity in these green polymers and emphasize the impact of their structural features on the resulting properties.

PALS and physico-chemical study of swift heavy ions and gamma radiation irradiated polyamide nylon 66 polymer

Polyamide nylon 66 (PA-66) polymer samples after being irradiated with 100 MeV O7+ ions and gamma radiation were studied for modifications in free volume properties by using positron annihilation lifetime spectroscopy (PALS) technique. The results obtained from PALS experiment were analysed in terms of hole radius, available free volume and fractional free volume. Both, ion irradiation as well as gamma exposure showed modifications in the size of available free volume and fractional free volume but the effectiveness of gamma radiation exposure was more pronounced than that of ion irradiation. The modifications produced in optical, structural and chemical properties of the PA-66 samples were studied by UV–visible (UV–vis) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy respectively. UV–vis studies showed a shift in absorption edge towards the visible region and a decrease in band gap energy (Eg). An increase in the crystalline nature of the polymer at higher fluence as a result of decrease in the peak width of XRD patterns was observed. The FTIR studies showed insignificant modifications in the chemical structure of irradiated polymer samples. Increase in surface roughness and cracks were observed in SEM results of ion and gamma exposed samples respectively.

A carbon nanotubes photoconductive detector for middle and far infrared regions based on porous silicon and a polyamide nylon polymer

Sensitive and good response photoconductive detectors working in the middle and far infrared regions were fabricated. These detectors were fabricated based on multi and double walled carbon nanotube films and works at room temperature. The films were deposited on a porous silicon (PSi) nanosurface. The surfaces were functionalized by a thin layer of polyamide nylon polymer to improve the photoresponsivity of the fabricated detectors. The response time of the fabricated MWCNTs-PSi detectors were 30 and 0.22 ms for the middle and far IR region respectively. The functionalisation of the MWCNTs-PSi film surface by the polyamide nylon polymer improved the photoconductive gain, photoresponsivity, and specific conductivity in both MWCNTs-PSi and DWCNTs-PSi detectors. The designed carbon nanotube (CNT) based photodetector has low cost, high sensitivity and reasonable speed for the middle and far IR spectral range without cooling.

Enhanced production of gamma-aminobutyrate (GABA) in recombinant Corynebacterium glutamicum by expressing glutamate decarboxylase active in expanded pH range.

BackgroundGamma-aminobutylate (GABA) is an important chemical in pharmacetucal field and chemical industry. GABA has mostly been produced in lactic acid bacteria by adding L-glutamate to the culture medium since L-glutamate can be converted into GABA by inherent L-glutamate decarboxylase. Recently, GABA has gained much attention for the application as a major building block for the synthesis of 2-pyrrolidone and biodegradable polyamide nylon 4, which opens its application area in the industrial biotechnology. Therefore, Corynebacterium glutamicum, the major L-glutamate producing microorganism, has been engineered to achieve direct fermentative production of GABA from glucose, but their productivity was rather low.ResultsRecombinant C. glutamicum strains were developed for enhanced production of GABA from glucose by expressing Escherichia coli glutamate decarboxylase (GAD) mutant, which is active in expanded pH range. Synthetic PH36, PI16, and PL26 promoters, which have different promoter strengths in C. glutamicum, were examined for the expression of E. coli GAD mutant. C. glutamicum expressing E. coli GAD mutant under the strong PH36 promoter could produce GABA to the concentration of 5.89 ± 0.35 g/L in GP1 medium at pH 7.0, which is 17-fold higher than that obtained by C. glutamicum expressing wild-type E. coli GAD in the same condition (0.34 ± 0.26 g/L). Fed-bath culture of C. glutamicum expressing E. coli GAD mutant in GP1 medium containing 50 μg/L of biotin at pH 6, culture condition of which was optimized in flask cultures, resulted in the highest GABA concentration of 38.6 ± 0.85 g/L with the productivity of 0.536 g/L/h.ConclusionRecombinant C. glutamicum strains developed in this study should be useful for the direct fermentative production of GABA from glucose, which allows us to achieve enhanced production of GABA suitable for its application area in the industrial biotechnology.

Endoscopic endonasal cranial base surgery simulation using an artificial cranial base model created by selective laser sintering.

Mastery of the expanded endoscopic endonasal approach (EEA) requires anatomical knowledge and surgical skills; the learning curve for this technique is steep. To a great degree, these skills can be gained by cadaveric dissections; however, ethical, religious, and legal considerations may interfere with this paradigm in different regions of the world. We assessed an artificial cranial base model for the surgical simulation of EEA and compared its usefulness with that of cadaveric specimens. The model is made of both polyamide nylon and glass beads using a selective laser sintering (SLS) technique to reflect CT-DICOM data of the patient's head. It features several artificial cranial base structures such as the dura mater, venous sinuses, cavernous sinuses, internal carotid arteries, and cranial nerves. Under endoscopic view, the model was dissected through the nostrils using a high-speed drill and other endonasal surgical instruments. Anatomical structures around and inside the sphenoid sinus were accurately reconstructed in the model, and several important surgical landmarks, including the medial and lateral optico-carotid recesses and vidian canals, were observed. The bone was removed with a high-speed drill until it was eggshell thin and the dura mater was preserved, a technique very similar to that applied in patients during endonasal cranial base approaches. The model allowed simulation of almost all sagittal and coronal plane EEA modules. SLS modeling is a useful tool for acquiring the anatomical knowledge and surgical expertise for performing EEA while avoiding the ethical, religious, and infection-related problems inherent with use of cadaveric specimens.

Preparation of MgO-templated carbons from waste polymeric fibres

Mesoporous carbons with a high surface area were produced using reinforcing fibres from scrap tyres, polyester Dacron®, polyamide Nylon6 and a bituminous waste as carbon precursor by two different procedures: physical activation and MgO-template synthesis. Moreover, MgO-template synthesis was carried out by means of two different mixing methods: powder- and solution-mixing procedures. The maximum surface area, highest pore volume and mesopore ratio were obtained for MgO-templated carbons. Nanocarbons with narrow pore size distributions showing maxima at 4.5–5nm in the case of powder-mixed MgO templated carbons and at 7nm for solution-mixed MgO templated carbons were obtained. The mesopore size of the carbon-coated materials was in agreement with their crystallite size as determined by X-ray diffraction (XRD). The surface chemistry of the materials was also studied by thermal programmed desorption (TPD), infrared spectroscopy and by determining the pHPZC. The MgO-templated carbons had acid surface groups, whereas activated carbons had basic surface groups. The adsorption of a reactive dye by two nanocarbons prepared by two different mixing procedures was tested.

Study on structure and properties of dimer acid-based polyamide nylon modified by situ doping of Na-Montmorillonite

The effects of the inorganic situ doping of Na-MMT on the phase morphology, thermal properties and mechanical properties of DAPA nylon copolymers were investigated. The results show that addition of Na-MMT promoted the formation of the γ crystal phase and increased the crystal content of them caused by heterogeneous nucleation effect of stripped Na-MMT layer structure. It greatly increased tensile properties and flexural properties of DAPA/Na-MMT nanocomposite. Therefore, the tensile and flexural strength as well as flexural modulus achieved 15.4, 9.84, 192.3 MPa, while elongation and IZOD notched impact strength decreased. The decomposition reaction process of DAPA/Na-MMT nanocomposite was still one-step, and the maximum endothermic peak of the decomposition process of DAPA/Na-MMT nanocomposite shifted to high temperature region.

Comparative evaluation of sorption, solubility and microhardness of heat cure polymethylmethacrylate denture base resin & flexible denture base resin.

The aim of the study was to evaluate and compare sorption, solubility and microhardness of heat cure polymethylmethacrylate (PMMA) denture base resin and flexible (thermoplastic polyamide nylon) denture base resin. Sorption, solubility and microhardness were assessed to determine compliance with ADA Specification no. 12. RESULTs were assessed using statistical and observational analyses. All materials satisfied ADA requirements for sorption, solubility and microhardness. Heat cure PMMA showed more sorption, solubility and microhardness than flexible (thermoplastic polyamide nylon). Flexible (thermoplastic polyamide nylon) resin absorbs less water, is less soluble and is more flexible than PMMA.

Preparation and Characterization of Modified Nylon 66 Membrane for Blood Purification

Membranes were synthesized using polyamide (nylon 66) and monosodium glutamate (MSG) additive. The membranes with higher concentration of MSG additive were found to be thermally more stable and of porous structure. Due to porous structure, the permeation rate of impurities in blood through the membrane was increased. The effect of coagulant liquid temperature was also investigated and it was shown that increasing/decreasing the temperature does not significantly affect the performance of the polyamide-MSG membrane.

Free volume evolution in 50 MeV Li3+ ion-irradiated polymers studied by positron annihilation lifetime spectroscopy

This article is aimed at studying the effect of ion irradiation on free volume of polyethersulphone (PES) and polyamide nylon-6 (PN-6) polymers by positron annihilation lifetime spectroscopy (PALS). Free volume properties of polymeric materials change with swift heavy ion irradiation. Free volume is found to have a strong correlation with the macroscopic properties of the polymer. PALS has recently emerged as a unique non-destructive and non-interfering nano-probe, capable of measuring the free volume hole size in polymers with high detection efficiency. PES and PN-6 polymer films of thickness of 250 μm were irradiated with Li3+ ions of energy 50 MeV from the 15 UD Pelletron accelerator at the Inter University Accelerator Centre, New Delhi, India. PES films were irradiated to the fluences of 1011, 1012, 1013 and 1014 ions/cm2, whereas PN-6 films were irradiated to the fluences of 1011, 1012 and 1013 ions/cm2. The average free volume and fractional free volume obtained from the long-lived component, attributed to ortho-positronium lifetime, are found to vary with the variation of fluence in both the cases.

Semicrystalline Polyamide Engineering Thermoplastics Based on the Renewable Monomer, 1,9-Nonane Diamine: Thermal Properties and Water Absorption

A series of poly(1,9-nonamethylene adipamide-co-1,9-nonamethylene terephthalamide) copolymers were produced using melt polymerization and the thermal properties, crystal structure, and moisture uptake characterized. The results confirmed that the copolymers exhibit isomorphism. As expected, glass transition temperature and the apparent melting temperature increased with increasing terephthalmide content. Using the difference in the apparent melting temperature to the crystallization temperature as a measure of relative crystallization rate, it was observed that crystallization rate decreased as the terephthalamide content of the copolymer was increased from 0 to 50 mole % but then sharply increased when increased beyond 50 mole %. This behavior may be the result of extensive inter- and intramolecular interactions in the melt associated with terephthalmide units in the polymer chain that nucleate crystallization upon cooling below the equilibrium melting temperature. Comparing the thermal properties of copolymers possessing an excess of terephthalmide units to the commodity polyamide Nylon 6,6, it is believed that these copolymers may have utility as partially renewable engineering thermoplastics.

Fabrication and Characteristics of Fast Photo Response ZnO/Porous Silicon UV Photoconductive Detector

Fast response time UV photoconductive detector was fabricated based on ZnO film prepared by thermal chemical spray pyrolysis technique. The ZnO nanofilms are grown on the porous silicon (PS) nanosurface which has drastically reduced the response time of the ZnO UV detector from few seconds to few hundreds of microseconds. The surface functionalization of the ZnO film deposited on porous silicon (PS) layer by polyamide nylon has highly improved the photoresponsivity of the detector to 0.8 A/W. The normalized de-tectivity (D*) of the fabricated ZnO UV detector at wavelength of 385 nm is found to be about 2.12 × 1011 cm Hz1/2 W–1. The ZnO film grown on the porous silicon layer was oriented in the c-axis and it is found to be a p-type semiconductor, which is referred to the compensation of the excess charge carriers in the ZnO film by the nanospikes silicon layer.

Mechanical properties of injection-molded thermoplastic denture base resins

Objective. To investigate the mechanical properties of injection-molded thermoplastic denture base resins. Material and methods. Four injection-molded thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were used in this study. The flexural strength at the proportional limit (FS-PL), the elastic modulus, and the Charpy impact strength of the denture base resins were measured according to International Organization for Standardization (ISO) 1567 and ISO 1567:1999/Amd 1:2003. Results. The descending order of the FS-PL was: conventional PMMA > polyethylene terephthalate, polycarbonate > two polyamides. The descending order of the elastic moduli was: conventional PMMA > polycarbonate > polyethylene terephthalate > two polyamides. The descending order of the Charpy impact strength was: polyamide (Nylon PACM12) > polycarbonate > polyamide (Nylon 12), polyethylene terephthalate > conventional PMMA. Conclusions. All of the injection-molded thermoplastic resins had significantly lower FS-PL, lower elastic moduli, and higher or similar impact strength compared to the conventional PMMA. The polyamide denture base resins had low FS-PL and low elastic moduli; one of them possessed very high impact strength, and the other had low impact strength. The polyethylene terephthalate denture base resin showed a moderately high FS-PL, moderate elastic modulus, and low impact strength. The polycarbonate denture base resin had a moderately high FS-PL, moderately high elastic modulus, and moderate impact strength.

Skull base training and education using an artificial skull model created by selective laser sintering

Practicing skull base approaches on cadavers affords the surgeon a chance to learn complex anatomical relationships and to practice surgical skills. However, there are ethical or legal problems in obtaining cadaver material in some countries. In addition, there is always risk of transmitting infections with cadaveric material. In order to get around these problems, we created a whole skull model which reproduces the detailed anatomy within the skull base using a selective laser sintering (SLS) technique. The first author's head was scanned using multidetector-row computed tomography. The data were reconstructed and converted into the standard triangulation language file system. Powdered material comprised of polyamide nylon and glass beads was laser-sintered in accord with the data derived from the head CT. The model was dissected under a surgical microscope using a high-speed drill, suction, and other surgical instruments. The appearance of both inner and outer cranial surfaces, including sutures, foramens, fissures, and protrusions, were clearly demonstrated. The artificial mastoid did not melt from the heat of the drill when a mastoidectomy was performed. The anatomical structures inside the mastoid and of paranasal sinuses were accurately reproduced in the model. The model created using SLS should be very useful for the teaching skull base approaches avoiding the ethical, legal, and infection problems inherent in cadavers.

How Should Nets be Dried After Insecticide Treatment in the Field?

Different procedures for drying polyamide (nylon) hammock nets (approximately 10 m2) posttreatment were evaluated. Forty-three nets were soaked for 10 min in a plastic bowl containing a solution of water and lambdacyhalothrin 0.05% (target dose of 10 mg/m2). Twenty-two freshly treated nets were put to dry in the sun: 13 of them hung vertically with the roof of the hammock net at the top and the hem at the bottom, and the other 9 were folded and laid flat on a plastic sheet. The rest of the nets (21) were dried in the shade: 11 of them hung vertically and 10 were folded flat on a plastic sheet. After 6-7 h, 2 15-cm2 samples of each net were cut, one on top of the lateral side and one 40 cm from the edge. Concentrations of lambdacyhalothrin were determined by gas chromatography-mass spectrometry on subsamples of netting (1 cm2). The mean insecticide concentrations of samples were compared between nets that were dried in the sun or in the shade, and placed to dry either hanging vertically or folded flat. In general, no differences were found between the mean insecticide concentrations of nets that were dried vertically in the sun or in the shade, or those dried flat in the shade. However, the mean dose was considerably lower in the remaining nets, which were dried flat in the sun. The reason for this is unclear but is hypothesized to be an effect of temperature. Results indicated that nets hung vertically either in the sun or shade dried faster than those laid flat. Based on the time to dry and mean insecticide extracted, it is recommended to hang treated nets vertically in the sun for drying.

Li3+ ion irradiation effects on polyamide nylon6,6 studied by positron annihilation lifetime and Doppler broadening spectroscopy

AbstractSwift Heavy ion (SHI) irradiation of polymeric materials changes their free volume properties which are strongly correlated to their macroscopic structure. 250 μm thick Polyamide Nylon‐6,6(PN‐6,6) polymer films were irradiated with 50 MeV Li3+ ions from Pelletron accelerator to the fluences of 5 x 1010, 1011, 5 x 1011, 1 x 1012, 5 x 1012, 1013 and 3.5 x 1013 ions/cm2. The effect of heavy ion irradiation on the free volume was studied by Positron Annihilation Lifetime (PAL) and Doppler Broadening Spectroscopy (DBS). Mean free volume hole radius, free volume and fractional free volume of micro‐voids, obtained from o‐Ps lifetime decrease with fluence and is attributed to cross linking. S parameter which is supposed to change due to vacancies type defects created due to SHI irradiation also decreases. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Plastic materials as a radiation shield forβ− sources: a comparative study through Monte Carlo calculation

We have developed a Monte Carlo simulation in Geant4 to compare the attenuation properties andthe bremsstrahlung radiation yield of different types of plastic materials employed as shields forβ− radioactivesources. Code validation results against Sandia and NIST data are presented. For polypropylene (C3H6), polystyrene (C2H3), polyamide nylon-6 (C6H11ON), poly-methyl methacrylate(C5H8O2), polycarbonate(C16H6O3), polyethyleneterephthalate (C10H8O4),polyvinyl chloride (C2H3Cl) andpolytetrafluoroethylene (C2F4) we evaluated the mean and maximum ranges for electrons originating from 90Sr and 90Y, as well as the number and spectrum of the bremsstrahlung x-rays produced. Significantdifferences appear between the various materials, and the choice of the best onealso depends on the physical properties requested for each specific application.

Further Validation of a Numerical Model for Prediction of Pyrolysis of Polymer Nanocomposites in the Cone Calorimeter

Nanocomposites have been increasingly used, as an alternative to traditional fire retardants, to improve the strength and fire retardancy of polymeric materials. A number of studies using the cone calorimeter showed that the nanoparticles used in small quantities (e.g., 3 wt%) reduce significantly the heat release rate (HRR). The formation of a surface layer on top of the unpyrolysed material is generally considered responsible for the reduced HRR. In a previous study, the global effects of the surface layer were examined by the present authors and a methodology was subsequently developed to predict pyrolysis of a polyamide nylon (PA6) nanocomposite in good agreement with the experimental data. This work presents further validation of the methodology for two more nanocomposites, namely polybutylene terephthalate and ethylene-vinyl acetate. Furthermore, the existing model is extended to explain the effects of change in the nanofiller loading on the HRR, and the modified model is applied to the experimental data obtained for a PA6 nanocomposite by Morgan et al. (Fire and polymers: materials and solutions for hazard prevention. American Chemical Society, Washington, DC, 2001, pp 9–23).