Pure PA Research Articles

Influence of Polyhydroxybutyrate Content on the Crystallization Behavior of Polyamide 6‐polyhydroxy‐butyrate Blends

With the aim of exploring new areas of application for polyhydroxybutyrate (PHB), blends of PHB, polyamide 6 (PA 6) and partly maleated polyhydroxybutyrate (C) were compounded, injection molded into multi‐purpose test specimens and investigated. Blends with 2.5, 5, and 10% PHB content and an additional series where the PHB content was supplemented by an equal percentage of C, in each case, were produced. To investigate the influence of PHB and C on the crystallization behavior of PA 6, the blends were analyzed using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The results have shown that PHB has a nucleating influence on the PA 6 matrix. Compared to pure PA 6, the melting temperature decreases slightly, but the melting enthalpy and the proportion of smaller crystallites increases. A change of the crystallite configuration of the PA 6, from α to γ structure, depending on the PHB content, could be excluded by FTIR measurements.

Enhanced thermal conductivity of palmitic acid/mullite phase change composite with graphite powder for thermal energy storage

To improve the energy storage efficiency of phase change composites, porous mullite was used to encapsulate the PCM-palmitic acid and graphite powder was applied to enhance the overall thermal conductivity. During the experimental process, a series of palmitic acid/mullite/graphite (PA/mullite/GP) composites were prepared to obtain the PA/mullite/GP form stable phase change material (FSPCM) by facile direct impregnation method. Then their microstructure, chemical compatibility and thermophysical properties were studied by the method of SEM, FTIR, XRD, DSC, TGA and PR, systematically. The DSC results demonstrate that the PA, PA/mullite and PA/mullite/GP have the enthalpy of melting of 213.1 J/g, 54.7 J/g, and 52.3 J/g, while the enthalpy of freezing of 217.0 J/g, 53.6 J/g and 51.5 J/g, respectively. Compared with the pure PA, the thermal conductivity of the prepared PA/mullite/GP has been improved from 0.28 W m−1 K−1 to 0.52 W m−1 K−1 owing to the high thermal conductivity of GP (only 5 wt %). The reliability test shows that the PA/mullite/GP FSPCM maintains form-stable without any PA leakage even after 150 thermal cycles. In short, prepared PA/mullite/GP FSPCM exerts excellent chemical and thermal reliability and thus has a bright prospect in the field of solar energy storage and solar heating.

Development of graphene-drug nanoparticle based supramolecular self assembled pH sensitive hydrogel as potential carrier for targeting MDR tuberculosis

ABSTRACTThe Mycobacterium tuberculosis (MTB) resides in mononuclear phagocytes (macrophages) hence selective targeting at the molecular level using Graphene Oxide (GO) Air Dried Hydrogel (ADH) is investigated in present investigation. The GO has capability to form supramolecular self assembly, due to π – π stacking and hydrogen bonding interactions between surface groups of GO and oppositely charged drug molecule in presence of water. The hydrogel was fabricated using GO and Para-aminosalicylic acid (PAS) in solution phase. The fabricated hydrogel was lyophilized to obtain air dried hydrogel (ADH). The ADH showed potent antimicrobial activity and in-vitro cytotoxicity against S. Aureus and E. Coli, and MCF −7 cells respectively. The Alamar blue assay demonstrated the invasive characteristics of ADH in MTB (H37Rv). From the results obtained so far we lead to conclude that ADH is more invasive compared to the equivalent amount of pure PAS.

Enhanced thermal conductivity of phase change material nanocomposites based on MnO2 nanowires and nanotubes for energy storage

Phase change materials (PCMs) have been widely used as efficient materials in latent heat thermal storage systems for various applications. The poor thermal conductivity of most organic phase change materials (OPCMs), however, has long been considered as one of big obstacles hindering their practical applications. Here, we report the first examples of Manganese dioxide nanowires and nanotubes based PCM nanocomposites (named as MnO2 NWs/PCM and MnO2 NTs/PCM) with enhanced thermal conductivity by simply using MnO2 nanowires and nanotubes as efficient nanofillers. The PCMs nanocomposites show high latent heat ranging from 140.1 J g−1 to 206.1 J g−1. The thermal conductivity of PCM nanocomposites were dramatically enhanced by incorporation of Manganese dioxide nanowires and nanotubes with a maximum value of 377.16% of that of pure PA achieved, which is nearly two times of that of control. X-ray diffraction (XRD) analysis shows that the incorporation of nanofillers does not change the crystalline structure of OPCMs while lowering its crystalline size. The PCM nanocomposites also show excellent thermal stability of recyclability. Only a slight loss of 2.8% in latent heat was observed after 100 times of melting/cooling cycles. Based on their high heat storage performance, excellent thermal conductivity and thermal stability of recyclability, the as-prepared PCM nanocomposites may have great potentials for energy saving applications.

THE INFLUENCE OF SELECTIVE LASER SINTERING PARAMETERS ON TRIBOLOGICAL PROPERTIES OF PA 3200 GF POLYAMIDE

The paper presents the preliminary results of tribological research on the material used in the selective laser sintering technology, SLS. The samples in the shape of rings were manufactured of PA 3200 GF polyamide powder additionally reinforced with glass fibre, which is based on pure PA 2200 polyamide. The tests were carried out on a tribological T-15 tester, ring-on-disc type imitating the cooperation conditions of elements, e.g., the rings of the contact active seal. The main objective of the research was to determine the influence of the direction of the positioning of the models on the construction platform on the coefficient of friction and the wear of the cooperating friction pair components.

Process prediction of selective laser sintering based on heat transfer analysis for polyamide composite powders

With the increasing research into selective laser sintering of composite powders, a modified numerical model was introduced to provide appropriate process predictions for the production of different functional composites. This numerical method included an effective volumetric heat source model and an integrated testing procedure, in which the differences of polyamide/carbon fiber (PA/CF) and PA/NaCl composite powders in thermo-physical and optical properties were studied. The unknown variables in the numerical model were all determined by experiments. The simulated temperature distributions of different powder beds exhibited a big difference in the melting depth. Entirely different processing parameters were planned for the two composites according to their simulation results. In the following experiments, highly porous PA derived from PA/NaCl composites had a maximum porosity of 59%. Compared with pure PA, CF reinforced PA showed a dramatic increase of the flexural strength and modulus by a factor of 100% and 380%, respectively. Therefore, the design objectives of two PA composites were both well accomplished. In addition, the experimental investigation became more efficient due to the process prediction. The accuracy of the model was validated by the microstructures of PA/CF and PA/NaCl, which meant this method could be used to provide appropriate process planning for more composites.

Fabrication and characterization of polysiloxane/polyacrylate composite latexes with balanced water vapor permeability and mechanical properties: effect of silane coupling agent

In order to improve the water vapor permeability and mechanical properties of latex films, polysiloxane/polyacrylate (PSi/PA) composite latexes were fabricated via seeded emulsion polymerization of methyl methacrylate and butyl acrylate onto PSi latex particles, and the effects of the silane coupling agent 3-methacryloyloxypropyl trimethoxysilane (MATS) on the morphologies of the latex particles and films, as well as the microphase separation degree, the water vapor permeability and the mechanical properties of the latex films were investigated. Results indicated that MATS was essential for obtaining the PSi/PA composite latex particles with PSi as core and PA as shell and made a great contribution to restrict the phase separation. The PSi/PA core/shell latex films showed similar tensile strength and elongation with pure PA film, while exhibiting promising water vapor permeability. It was found that the influences of MATS content on the water vapor permeability and mechanical properties were opposite, and on the premise of the requirements for mechanical properties, lower MATS content could provide the PSi/PA core/shell latex films with better water vapor permeability.

Enhanced toughness for polyamide 6 with a core-shell structured polyacrylic modifier

Polyamide 6 (PA 6) is an important thermoplastic with excellent strength, stiffness, and good chemical resistance. The notch sensitivity and low notch impact toughness of PA 6, however, limit its application. A core-shell structured polyacrylic modifier, poly(n-butyl acrylate)/poly(methyl methacrylate-co-methacrylic acid) modifier (PBM-co-MAA), was used to toughen PA 6. To study the effect of PBM-co-MAA particles on the toughness of PA 6, various contents of poly(BA) in PBM-co-MAA latexes of 300 nm were synthesized by seed emulsion polymerization. The results showed that polymerization had an instantaneous conversion higher than 95 wt% and an overall conversion higher than 97 wt%. The PBM-co-MAA particles had a clear core–shell structure confirmed by transmission electron microscope (TEM). The mechanical properties of PA 6/PBM-co-MAA blends showed that the notch impact strength of PA 6/PBM-co-MAA blends with 85 wt% poly(BA) and 0.5 wt% MAA in PBM-co-MAA was nearly six times greater than that of pure PA 6, being consistent with the scanning electron microscope (SEM) observations on the fractured surfaces. The notch impact strengths of PA 6/PBM-co-MAA blends were also better than that of PA 6/PBM blend, which did not contain MAA functional group in the modifier. Dynamic mechanical analysis (DMA) results showed improved compatibility between PA 6 matrix and core-shell toughening modifier, which should contain a functional group in the shell layer and a suitable core rubbery content to toughen PA 6 effectively.

The application of PA/CF in stab resistance body armor

Stab resistance body armor (SRBA) is an essential defensive equipment to protect human body against injuries from stabbing. The conventional SRBAs shared low wearing frequency since they are heavy and poor in flexibility. This paper designed a structured stab-resistance plate using the model of crocodile armor and manufactured using 3D printing technology-laser sintering (LS). CF(Carbon fiber) was applied to enhance the stab resistance properties of SRBA. The effects of the material and structure were analysed through the stab resistance property tests based on the national standard GA68-2008. It is found that the stab resistance property of flat plates sintered by PA powder and PA/CF are both weaker than that of the structured plate. The penetrating depth of PA/CF structured plate is significantly 2-mm-less than the pure PA structured plate. The SEM observations confirmed the conclusion that addition of the CF largely improved the plate stab resistance property. Moreover, using PA/CF structured plate to produce the stab resistance body armor would result in a weight reduction by about 30-40% as compared to the existing SRBA that was made up of metal plates, which could largely reduce the wearer physical burden and improve the wearing frequency.

Polysiloxane/polyacrylate composite latexes with balanced mechanical property and breathability: Effect of core/shell mass ratio

ABSTRACTPolysiloxane/polyacrylate (PSi/PA) core/shell latexes are fabricated, and the particle morphology, the film structure, as well as the properties of the latex films are investigated by comparing with blend latexes, and the relationship between structure and property is proposed. Results indicate that the structure and property of the latex films heavily depend on the particle morphology. The sea–island latex films with uniform distribution of PSi phases can be formed from the PSi/PA core/shell latexes, and with the mass ratio from 1:1 to 1:4, their tensile strength and elongation at break are close to the pure PA latex film, while the elastic recovery and water vapor permeability improve notably. It is found that the phase segregation occurs in the blend latex films, and although the blend latex films provide better water vapor breathability, their mechanical properties sacrifice obviously. Therefore, the various properties must be balanced for practical applications and the core/shell latexes are competitive for meeting the balanced requirements. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45258.

Photomediated Larvicidal Activity of Pheophorbide a against Cercaria Larvae of Fasciola gigantica.

Fasciolosis is a parasitic disease caused by Fasciola gigantica. The freshwater snail Lymnaea acuminata is the intermediate host of F. gigantica which cause endemic fasciolosis in the northern part of India. To investigate larvicidal activity of pure and laboratory extracted pheophorbide a (Pa) against cercaria larvae of F. gigantica, data were analyzed in different spectra of visible light, sunlight, and laboratory conditions. Photostimulation of chlorophyll derivative pheophorbide a (Pa) caused time and concentration dependent larvicidal activity against cercaria larvae of F. gigantica. Larvicidal activity of pure Pa under 650 nm and 400–650 nm (8 h LC50 0.006 mg/10 mL) was more pronounced than extracted Pa under same irradiations (650 nm LC50 0.12 mg/10 mL, 400–650 nm LC50 0.14 mg/10 mL). Lowest toxicity of pure (8 h LC50 0.14 mg/10 mL) and extracted Pa (8 h LC50 1.25 mg/10 mL) was noted under 400 nm. Pa was found to be toxic in laboratory conditions also. The results presented in this paper indicate that pheophorbide a possess potential larvicidal activity against Fasciola gigantica larvae in different wavelengths of visible light, sunlight, and laboratory conditions.

Surface nanostructuring of thin film composite membranes via grafting polymerization and incorporation of ZnO nanoparticles

A new approach for modification of polyamid thin film composite membrane PA(TFC) using synthesized ZnO nanoparticles (ZnO NPs) was shown to enhance the membrane performances for reverse osmosis water desalination. First, active layer of synthesis PA(TFC) membrane was activated with an aqueous solution of free radical graft polymerization of hydrophilic methacrylic acid (MAA) monomer onto the surface of the PA(TFC) membrane resulting PMAA-g-PA(TFC). Second, the PA(TFC) membrane has been developed by incorporation of ZnO NPs into the MAA grafting solution resulting the ZnO NPs modified PMAA-g-PA(TFC) membrane. The surface properties of the synthesized nanoparticles and prepared membranes were investigated using the FTIR, XRD and SEM. Morphology studies demonstrated that ZnO NPs have been successfully incorporated into the active grafting layer over PA(TFC) composite membranes. The zinc leaching from the ZnO NPs modified PMAA-g-PA(TFC) was minimal, as shown by batch tests that indicated stabilization of the ZnO NPs on the membrane surfaces. Compared with the a pure PA(TFC) and PMAA-g-PA(TFC) membranes, the ZnO NPs modified PMAA-g-PA(TFC) was more hydrophilic, with an improved water contact angle (∼50±3°) over the PMAA-g-PA(TFC) (63±2.5°). The ZnO NPs modified PMAA-g-PA(TFC) membrane showed salt rejection of 97% (of the total groundwater salinity), 99% of dissolved bivalent ions (Ca2+, SO42−and Mg2+), and 98% of mono valent ions constituents (Cl− and Na+). In addition, antifouling performance of the membranes was determined using E. coli as a potential foulant. This demonstrates that the ZnO NPs modified PMAA-g-PA(TFC) membrane can significantly improve the membrane performances and was favorable to enhance the selectivity, permeability, water flux, mechanical properties and the bio-antifouling properties of the membranes for water desalination.

Graphene oxide-polyaniline nanocomposites for high performance supercapacitor and their optical, electrical and electrochemical properties

Polyaniline/Graphene oxide (PA/GO) composites were prepared by chemical polymerization of aniline with different wt% of GO under acid conditions. The synthesized samples were characterized by using Fourier transform infra red spectroscopy, ultraviolet–visible absorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. It is found that the dc electrical conductivity dramatically increased to 84 S/m for PA/GO (5 wt%) composite at 150 °C compared to pure PA (0.075 S/m). The PA/GO composites showed a reversible electrochemical response up to 150th repeated cycles as revealed by the cyclic voltammetry study. High specific capacitance of PA/GO composite of 543.75 F/g was obtained in the potential range from 0 to 0.50 V at 2 mA compared with 266.66 F/g for pure PA by galvanostatic charge–discharge analysis. Incorporation of GO into the polymer matrix has a pronounced effect on the electrical conductivity and electrochemical capacitance performance of PA/GO nanocomposites.

Thermally conductive polyamide 6/carbon filler composites based on a hybrid filler system

We explored the use of a hybrid filler consisting of graphite nanoplatelets (GNPs) and single walled carbon nanotubes (SWCNTs) in a polyamide 6 (PA 6) matrix. The composites containing PA 6, powdered GNP, and SWCNT were melt-processed and the effect of filler content in the single filler and hybrid filler systems on the thermal conductivity of the composites was examined. The thermal diffusivities of the composites were measured by the standard laser flash method. Composites containing the hybrid filler system showed enhanced thermal conductivity with values as high as 8.8 W (m · K)−1, which is a 35-fold increase compared to the thermal conductivity of pure PA 6. Thermographic images of heat conduction and heat release behaviors were consistent with the thermal conductivity results, and showed rapid temperature jumps and drops, respectively, for the composites. A composite model based on the Lewis–Nielsen theory was developed to treat GNP and SWCNT as two separate types of fillers. Two approaches, the additive and multiplicative approaches, give rather good quantitative agreement between the predicted values of thermal conductivity and those measured experimentally.

Measurement and correlation of ternary solid–liquid equilibrium of 2-methyl-1,4-naphthoquinone + phthalic anhydride + acetone system

The solid–liquid equilibrium or the ternary system of 2-methyl-1,4-naphthoquinone + phthalic anhydride + acetone were determined at three temperatures of (283.15, 293.15 and 303.15) K, respectively. Three isothermal phase diagrams of the system were constructed on the basis of the measured solubility. Two pure solid phases were formed at (283.15, 293.15 and 303.15) K, including pure PA and pure 2-MNQ, which were confirmed and determined by the method of Schreine makers' wet residue. The densities of equilibrium liquid phase were determined experimentally at the corresponding temperatures versus mass fraction of component. The phase diagram at 283.15 K is similar to those at (293.15 and 303.15) K and the crystalline fields of 2-MNQ and PA decrease with an increase in temperature. The ternary diagram can provide the fundamental basis for separation of 2-MNQ and PA.

Thermal extraction combined with thermal desorption: A powerful tool to investigate the thermo-oxidative degradation of polyamide 66 materials

Using thermogravimetric analysis (TGA) with a solid-phase adsorber for thermal extraction, followed by subsequently analysing the adsorber with thermo-desorption gas chromatography mass spectrometry (TDS-GC–MS) enables measurement of polymer degradation under oxidizing atmosphere, and the identification of certain complex hydrocarbon degradation products by chromatographic separation and defined mass patterns. This technique, thermal-extraction desorption gas chromatography mass spectrometry (TED-GC–MS) was used to investigate the thermo-oxidative degradation of PA 66 and PA 66 doped with 2wt% of metal oxide particles. In TGA pure PA 66 formed more residue under an oxidizing atmosphere than an inert one. In contrast to the measurements under inert atmosphere, several condensed aromatic species containing nitrogen could be identified in thermo-oxidative measurements. These degradation products were formed through condensation reactions of primary amides originating from imide hydrolysis. The formation of such highly condensed species also causes higher char formation. Four metal oxides have shown an impact on the thermo-oxidative degradation of PA 66: Fe2O3 on η-Al2O3<pure Fe2O3=Fe2O3 on γ-Al2O3<pure ZnO. For ZnO even a char-stabilizing effect could be observed. A catalytic effect of these metal oxides causes more condensed cyclopentanone and pyridine derivates. Thus, more water is formed and released, resulting in increased hydrolysis of the imides and degradation at lower temperatures.

Preparation and thermal characterization of composite “Paraffin/Red Brick” as a novel form-stable of phase change material for thermal energy storage

This study is focused on the preparation and characterization of thermal properties and thermal reliability of Paraffin (Pa)/Red Brick (Br) composite as form-stable phase change material (PCM). The maximum mass fraction of Pa retained in Br was found as 40 wt% without the leakage of Pa, in melted state even when it's heated over the melting point of Pa. The materials used, red brick powder (Br), paraffin (Pa), expanded graphite (EG) and PCM composite are characterized by Laser Particle Size, by Environmental Scanning Electron Microscopy and Spectroscopy Infrared Fourier Transform. The thermo-physical properties of composites MCPs are studied by Differential Scanning Calorimetry. The results show that the composite to form stabilized prevents leakage of the phase change material from the matrix. The surface of the clay matrix is fully charged paraffin by a physical attraction. The FT-IR analysis shows that there is no chemical reaction between the matrix and the MCP. From differential scanning calorimetry (DSC) analysis, the melting and freezing temperatures and latent heats of the form-stable PCM were measured as 52.73 °C and 55.8 °C and 41.32 J/g and 42.39 J/g. Thermal conductivity of form-stable Pa/Br/EG (10%) composite (0.52 Wm−1K−1) was found to be 3 times higher than that of pure Pa (0.1716 Wm−1K−1). Based on all results, it was concluded that the form-stable Pa/EG (40/60 w/w%) has considerable latent heat energy storage potential because of its good thermal properties, thermal and chemical reliability and thermal conductivity.

New Spectrophotometric Methods for the Determination of p-Aminosalicylic Acid in Tablets

Purpose: To develop a new spectrophotometric method with improved sensitivity and at higher wavelength for the determination of p-aminosalicylic acid in tablets.Methods: Two simple and sensitive spectrophotometric methods (methods A and B) were developed using p-dimethylaminobenzaldehyde (DAB), and p-dimethylaminocinnamaldehyde (DAC) as derivatizing reagents for the determination of p-aminosalicylic acid (PAS) in tablets. The derivatization was carried out using 3M HCl-KCl buffer for DAB and 5M HCl-KCl buffer solutions.Result: The new derivatives of PAS absorbed maximally with bathochromic shift to 460 and 555 nm in the linear concentration range of 0.4 – 2.0 μg/mL with molar absorptivities of 2.4 × 104 and 3.8 × 104 L/mole/cm, respectively, compared to pure PAS which absorbed at λmax of 264 nm with molar absorptivity 7.65 × 103 L/mole/cm in the linear concentration range of 2 - 10 μg/mL. The developed methods were successfully applied to assay PAS in tablets with % recovery of 97.6 ± 1.71 and 98.4 ± 1.45 for methods A and B, respectively.Conclusion: Both PAS derivatives absorb in the visible spectral region. The presence of excipients in pharmaceutical preparations did not interfere in the determination of PAS as PAS-DAB and PAS-DAC derivatives. Both methods can be applied to determine PAS from bulk and various pharmaceutical dosage forms.Keywords: p-Aminosalicylic acid, p-dimethylaminobenzaldehyde, p-dimethylaminocinnamaldehyde, Spectrophotometry

Facile preparation of carbon microcapsules containing phase-change material with enhanced thermal properties.

This study describes the hydrothermal synthesis of a novel carbon/palmitic acid (PA) microencapsulated phase change material (MEPCM). The field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) images confirm that spherical capsules of uniform size were formed with a mean diameter of 6.42 μm. The melting and freezing temperature were found to be slightly lower than those of pure PA with little undercooling. The composite retained 75% of the latent heat of pure PA. Thermal stability of the MEPCM was found to be better than that of pure PA. The thermal conductivity of MEPCM was increased by as much as 41% at 30°C. Due to its good thermal properties and chemical and mechanical stability, the carbon/PA MEPCM displays a good potential for thermal energy storage systems.

Distribution and surface characteristic of transfer film of polyamide composites filled with ZnOw during traction rolling

Purpose – The purpose of this paper is to investigate the distribution and surface characteristic of transfer film of polyamide composites filled with ZnOw during traction rolling. Design/methodology/approach – In this paper, the traction rolling tribological behavior of polyamide composites filled with ZnOw was studied with a twin-disc traction rolling tester. The topography of transfer film was observed with a three dimensional profiler. Meantime the thickness of transfer film was measured. The chemistry elements of transfer film were analyzed with EDS and XRD. Findings – The results indicated that transfer film of composites patchily covered on the surface of counter disc, the amount of which increased with increasing cycles. The coverage and thickness of pure PA film increased against rolling cycles. However, the thickness of 15 wt.% ZnOw/PA film remained at 6 μm as the coverage rose against rolling cycles. Fe element was found in pure PA transfer film, which existed in Fe0 and FeO for chemical reaction between Fe and atmospheric oxygen. Transfer film of 15 wt.% ZnOw/PA composites included a little Zn and Fe element. Fe element existed as Fe0. Zn element existed as ZnO. Originality/value – This paper presented the distribution and surface characteristic of transfer film during traction rolling.