Preparation and properties of chitosan/acidified attapulgite composite proton exchange membranes for fuel cell applications

A composite proton exchange membrane chitosan (CS)/attapulgite (ATP) was prepared with the organic–inorganic compounding of ATP and CS. The composite membranes were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). The mechanical properties, thermal stability, water uptake, and proton conductivity of the composite membranes were fully investigated. The composite membranes exhibited an enhanced mechanical property, dimensional and thermal stability compared to CS membrane, owing to the interface interaction between ATP and CS. The maximum tensile strength of 53.1 MPa and decomposition temperature of 223.4°C was obtained, respectively. More importantly, the proton conductivity of the composite membrane is also enhanced, the composite membrane with 4 wt% ATP content (CS/ATP-4) exhibited the highest proton conductivity of 26.2 mS cm⁻¹ at 80°C with 100% relative humidity, which is 25.1% higher than pure CS membrane. These results may explore a simple and green strategy to prepare CS-based PEMs, which have a great potential in the application of proton exchange membrane fuel cells.     

Preparation,characterization, electrical and antibacterial properties of sericin/poly(vinyl alcohol)/poly(vinyl pyrrolidone) composites

In this study, we focused on the fabrication of poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP)/sericin composites via a simple solution‐blending method. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, UV spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and measurements of the conductivity, tensile strength, and antibacterial activity against Staphylococcus aureus. The results of FTIR and UV spectroscopy implied the occurrence of hydrogen bonding between sericin and the PVA/PVP blend. The structure and morphology, studied by XRD and SEM, revealed that the sericin particles were well dispersed and arranged in an orderly fashion in the blend. The glass‐transition temperature (T_g) of the composite was higher than that of the pure blend, and the T_g value shifted toward higher temperatures when the volume fraction of sericin increased. TGA indicated that sericin retarded the thermal degradation; this depended on the filler concentration. The mechanical and electrical properties, such as the tensile strength, alternating‐current electrical conductivity, dielectric constant, and dielectric loss of the composites, were higher than those of the pure blend, and these properties were enhanced when the concentration of sericin was increased up to 10 wt % filler content, whereas the elongation at break of the composite decreased with the addition of sericin particles. The antibacterial properties of the composite showed that sericin had a significant inhibitory effect against S. aureus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43535.     

Thermal and mechanical characterization of films based on poly(vinyl alcohol) and β‐lactoglobulin blends

In this study, we investigated the possibility of creating easy to handle films based on poly(vinyl alcohol) (PVA) and β‐lactoglobulin (βlg) blends using the casting method. Four different variables were studied to obtain these films: different proportions of PVA and βlg, different pHs (10, 7, 5.5, and 2.5), several molecular masses of PVA (130,000, 13,000–23,000, and 2000 g/mol), and the denaturation of βlg. The first objective was to obtain films, and the second was to characterize them by differential scanning calorimetry, thermogravimetric analysis, and mechanical testing. Significant variations in behavior were found, and the variables studied modified the blends in different ways. In particular, better results were achieved when the βlg proportion was less than 30 wt %, and when a pH of 2.5 was used in conjunction with a high molecular mass (130,000 g/mol) of PVA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41745.     

Mechanical and film formation behavior from PDMS/NaY zeolite composite membranes

In this study, polydimethylsiloxane (PDMS) and NaY zeolite doped composite membranes were prepared for the films varying from 0 to 15 NaY zeolite wt %. All the membranes were characterized by attenuated total reflectance–Fourier transform infrared (FTIR), X-ray diffraction, scanning electron microscopy, thermogravimetry/differential thermal analysis methods. The FTIR spectral results showed that there is physical interaction existing between the PDMS matrix and NaY zeolite. Additionally, film formation from the pure PDMS and PDMS/NaY composites were investigated by photon transmission technique. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. The NaY zeolite added films led to the significant improvement in the mechanical properties that both the tensile strength and Young's modulus increased three times. Thermal properties of the films were also investigated and the addition of NaY zeolite into the PDMS matrix could significantly improve the thermal stability of the composite membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48549.     

Preparation and characterization of polyamide 6/liquid natural rubber blends

This study presents a new approach to toughen Polyamide 6 (PA6) by using a low‐molecular weight liquid natural rubber (LNR). The LNR is prepared by mastication of pale latex crepe in the presence of 0.5 phr Peptizol 7. The PA6/LNR blend samples are characterized in terms melt flow index, hardness, abrasion resistance, impact strength, flexural strength, tensile strength, and thermal properties. The impact strength of PA6 increases by about 67% upon addition of 10% LNR. The percolation model is applied to study of brittle to ductile transition. The percolation threshold for the brittle to ductile transition of the blend was found to be 14.5 wt % LNR, corresponding to the critical volume fraction of the stress volume, V_sc = 0.58, which is consistent with the calculated value of ≈ π/6. The PA6/LNR blends exhibit cavitation and matrix shear yielding, which would be the main contribution to the increases impact strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39750.     

Thermal and mechanical properties of PES/PTFE composites and nanocomposites

Polyethersulphone/polytetrafluoroethylene (PES/PTFE) nanocomposites and composites were prepared by precipitation of PES into a PTFE latex‐containing nanoparticles. Different samples were obtained by varying the relative ratio between PES and PTFE. The complex crystallization process, discussed within the fractionated crystallization frame, allowed to identify and quantify different dispersion degree of the PTFE nanoparticles within the PES matrix. The different samples were thus divided into nanocomposite and composites. The effect of crystalline PTFE domains on the mobility of PES was investigated and discussed. The dynamic‐mechanical behavior was explained in terms of the particle aggregation state. The mechanical properties of the PES/PTFE composites were found to depend on both the dispersion and the concentration of the PTFE nanoparticles. In the glassy state the stiffness of the materials was found to increase with the dispersion degree, resulting higher for the nanocomposite with respect to composites. On the contrary, in the rubbery state the modulus was found proportional to the PTFE nanoparticles concentration, resulting higher in the composites with respect to the nanocomposite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3624–3633, 2013     

Enhancing the mechanical and barrier properties of chitosan/graphene oxide composite films using trisodium citrate and sodium tripolyphosphate crosslinkers

This study investigated the effect of ionic crosslinking on the mechanical, barrier, and optical properties of chitosan (CS) and CS/graphene oxide (CSGO) composite films using trisodium citrate (CIT) and sodium tripolyphosphate (TPP) solutions of different concentrations (0.5, 1.0. 2.0, and 3.0% w/v). Successful crosslinking was confirmed by Fourier-transform infrared spectroscopy. The hydrophilicity and light transmittance decreased significantly (p < 0.05) with the increase in concentration of both crosslinking agents. The CS films crosslinked with 3.0% w/v TPP exhibited significant (p < 0.05) improvements in barrier properties, achieving a 51% decrease of water vapor permeability and 59% decrease in oxygen permeability, in comparison to neat CS film. In addition, TPP-crosslinked CSGO films experienced an 82% and 42% improvement in tensile strength and elongation at break, respectively. Overall, crosslinked CS and CSGO films possess significantly improved properties and have great potential to be further studied as food packaging materials.     

Preparation and characterization of soluble bismaleimide‐triazine resins based on asymmetric bismaleimide

A series of bismaleimide‐triazine resins (EBT) were prepared from 2‐(4′‐maleimido)phenyl‐2‐(4′‐maleimidophenoxyl)phenylbutane (EBA‐BMI) and 2,2‐bis(4‐cyanatophenyl)propane (BADCy). The resins show attractive processability with good solubility in low boiling point solvents and wide processing temperature windows. Introduction of diallylbisphenol A (DBA) can decrease the curing temperature of EBT resins that the curing exothermic peak temperature shifted from 291 to 237 °C as the content of DBA increased from 0 to 20%. The curing condition influenced the thermal properties of the cured EBT resins. The glass transition temperature increased as the curing temperature and curing time increased. The cured EBT resins show high glass transition temperature up to 352 °C, high thermal stability with 5% weight loss temperature over 405 °C, low coefficient of thermal expansion about 45 to 52 ppm/°C, and high storage modulus up to 2.6 GPa at 250 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44519.     

Preparation and Recycling of Plasticized PLA

PLA is one of the most interesting new polymeric materials, mainly because of its favorable environmental features. On the other hand, one of its drawbacks is represented by its brittleness and low impact resistance. A possible solution may be the use of proper impact modifiers. Furthermore, limited knowledge exists on the behavior of PLA upon recycling. In this paper, a detailed investigation has been carried out on the behavior of PLA systems upon adding small amounts of commercial impact modifiers, and the effects of multiple recycling steps have been studied. The use of impact modifiers can effectively improve mechanical properties. Recycling led to a significant reduction in the impact strength; however a relatively high fraction of the other mechanical properties was still retained.

     

Synthesis and characterization of conductive composite films of polyisoprene/PA12@ PANI

Polyamide@Polyaniline powders of core‐shell structure are known to have reduced conduction thresholds useful to maintain the mechanical and optical properties of the matrix. However, difficulties emerge at the synthesis stage, where dissolving the matrix without damaging the core‐shell particles becomes a challenge. The present solution avoids using solvents. Conductive polymer films containing solid Polyamide@Polyaniline particles are elaborated by UV photoreticulation of a liquid polyisoprene serving as a matrix. The conductive powders are obtained by in‐situ polymerization of aniline in presence of polyamide 12 (PA12) at room temperature using Dodecyl benzene sulfonic doping acid and Ammonium persulfate oxidant. Obtained films exhibit low percolation threshold compared to those containing pure solid polyaniline (PANI) particles even more conductive. This threshold is shown to be about 1.5 wt % of PANI. Films show good electrical conductivity and thermal stability up to 200°C allowing their use as antistatic polymer films for high temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39833.     

Irradiated sodium–alginate/poly(ethylene oxide) blend films improved by methyl acrylate monomer

Sodium alginate (SA)‐based poly(ethylene oxide) (PEO) blend films were improved by methyl acrylate (MA) monomer and γ irradiation toward practical application. The films were prepared by a casting method and modified by glycerol (Gol) and mustard oil (MO). The SA‐based films were successfully produced with γ irradiation (12 kGy) with 10% PEO, 15% Gol, 20% MO, and 7% MA on a mass basis as optimized. The tensile strength (TS), tear strength (TT), elongation at break (EB), Young's modulus, moisture content, water vapor permeability (WVP), and structural properties of the blended films were determined. The thermal properties of the films were characterized by thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry, and the structural features were examined with Fourier transform infrared spectroscopy. The ultimate results of this study show a rather remarkable enhancement in the tensile properties (30% TS and 67% TT) and reduction in EB (40%) of the SA‐based films with MA addition and γ irradiation. The as‐prepared SA‐based films demonstrated considerable reductions in the moisture content and WVP and also conferred a desired stability of the films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43562.     

Curing behavior of epoxy resin/tung oil anhydride exfoliated nanocomposite by differential scanning calorimetry

The nanocomposite of epoxy resin/tung oil anhydride/organic montmorillonite was prepared by casting and curing. The distance of the clay gallery rose and the exfoliated nanocomposite was formed. The exfoliation behaviors of the nanocomposite had been investigated by X‐ray diffraction (XRD). The curing mechanism and kinetics of epoxy resin with the different amounts of organic montmorillonite were studied using isothermal and dynamic methods by differential scanning calorimetry (DSC). Some parameters, the activation energy and reaction orders, were calculated by the modified Avrami equation in analysis of the isothermal experiment. The total curing mechanism and kinetics of curing reaction were also analyzed by the Flynn–Wall–Ozawa method. It was noted that the instantaneous activity energy during the curing process could be obtained by the Flynn–Wall–Ozawa method and the trend of the results was in agreement with those obtained from the modified Avrami equation. These results show that the activity energy decreases with the addition of organic montmorillonite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3822–3829, 2004     

Crosslinked poly(vinyl alcohol) and starch composite films: Study of their physicomechanical,thermal, and swelling properties

Crosslinked poly(vinyl alcohol) was blended with 10, 20, 40, and 50 wt % starch by a solution‐casting process. The solution‐cast films were dried, and then their physicomechanical properties including tensile strength, tensile elongation, tensile modulus, tear strength and density, and burst strength and density were tested. Thermal analysis was performed by differential scanning calorimetry. A moisture analysis of the PVA/starch films was performed and their moisture content determined. Also investigated were the films'resistance to solubility in water, 5% acetic acid, 50% ethanol, and sunflower oil and their swelling characteristics in 50% ethanol and sunflower oil. The prepared PVA/starch blends showed significant improvement in tensile modulus and in resistance to solubility in water, 5% acetic acid, and 50% ethanol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1127–1132, 2007     

Structural characterization of polymer blends based on polysulfones

A series of blends with various compositions was prepared on the basis of polysulfone, polyethersulfone, and polyimide. These blends were characterized by different techniques, including Fourier transform IR spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and tensile stress–strain measurements. The results obtained allowed for certain conclusions regarding blend compatibility. In addition, the mechanical properties were subjected to an experimental test design to measure the blends for tensile break strength and Young's modulus with a computer program, which eventually enabled us to obtain the surface response equations of both properties and also to predict the optimum composition presenting the best mechanical behavior. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3030–3039, 2004     

Poly(ethylene terephthalate)-based nanocomposite films as greenhouse covering material: Environmental sustainability,mechanical durability,and thermal stability

The environmental sustainability, mechanical durability, and thermal stability of the poly(ethylene terephthalate) (PET)-based nanocomposite films compared with pure PET were evaluated. The samples were obtained by incorporating 2 wt% of TiO₂, SiO₂, ZnO nanoparticles (NPs), and an equal mixture of NPs in polymer by melt-mixing in a twin-screw extruder. The mechanical properties and hardness of samples were determined by the tensile and the atomic force microscopy-based nanoindentation tests. The melting, crystallization, and glass transition temperatures of samples were studied by dynamic mechanical thermal analysis and differential scanning calorimetry. The effects of compatibility, dispersity, and hydrophobicity of NPs on the surface morphology, crystallinity, and thermomechanical properties of nanocomposites were studied. The interaction of SiO₂ NPs with PET chains had a promising effect on the surface morphology, high elastic modulus, dispersibility, crystallinity, and thermostability of the sample. The mixing of ZnO and TiO₂ NPs improved the UV-blocking effects, and photostability, while the SiO₂ and TiO₂ NPs maintained the thermal properties of the film against UV radiation. The resulting film could be a good candidate as a greenhouse covering material due to its suitable photosynthetically active radiation transmittance.     

The effect of PETA/PETTA composite system on the performance of UV curable waterborne polyurethane acrylate

UV curable waterborne polyurethane acrylate based on pentaerythritol triacrylate (PETA)/pentaerythritol tetraacrylate (PETTA) composite system was prepared by using polycaprolactone glycol (PCL), isophorone diisocyanate (IPDI), β‐cyclodextrin (β‐CD) and 2,2‐dimethylol butanoic acid (DMBA) as the main materials. Besides, PETA was used as capping agent and PETTA was used as reactive diluent. By varying the additive amount of PETA and PETTA, a series of emulsions and films were obtained. The molecular structure was characterized by infrared spectra and a series of performance tests such as particle size, contact angle, tensile properties, UV curing performance, differential scanning calorimetry and thermogravimetric analysis were conducted. The result showed that more compact network structure was formed by introducing PETTA with higher reactivity into the polyurethane molecule under UV irradiation and many performances were improved as a whole. However, there existed phase separation to a certain extent. Especially when the content of PETTA was higher than 83.33%, the effect of compatibility became more prominent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41262.     

Impact modification of poly(trimethylene terephthalate)/polypropylene blend nanocomposites: Fabrication and characterization

A poly(trimethylene terephthalate) (PTT)/polypropylene (PP) blend and the nanocomposites were prepared with and without the addition of a compatibilizer precursor [maleic anhydride grafted polypropylene (MAPP)]. A reactive route was used for the compatibilization with the addition of MAPP during melt blending in a batch mixer. Organically modified nanoclays were used as nanoscale reinforcements to prepare the blend nanocomposites. Mechanical tests revealed optimum performance characteristics at a PTT/PP blend ratio of 80 : 20. Furthermore, incorporation of nanoclays up to 3 wt % showed a higher impact strength and higher tensile strength and modulus in the blend nanocomposites compared to the optimized blend. The nanocomposite formation was established through X‐ray diffraction and transmission electron microscopy (TEM). Thermal measurements were carried out with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC thermograms revealed an increase in the crystallization temperature in the presence of the nanoclays in the blend system containing Cloisite 30B. TGA thermograms also indicated that the thermal stability of blend increased with the incorporation of Cloisite 30B. Furthermore, dynamic mechanical analysis measurements showed that the Cloisite 30B nanocomposite had the maximum modulus compared to other nanocomposites. TEM micrographs confirmed an intercalated morphology in the blend nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphology and thermal properties of recycled polyacrylonitrile fiber blends with poly(ethylene terephthalate): Microstructural characterization

The compounding of rPAN/PET [polyacrylonitrile/poly(ethylene terephthalate]; 30/70, 50/50, and 70/30 wt %) using a melt‐blending technique was the main focus of this investigation. An X‐ray diffraction study indicated the possibility of interphase boundary interactions between the polymer matrices in the blends. The differential scanning calorimetry results showed that varying the ratios of rPAN in the blends marginally improved the processing temperature of PET. The thermogravimetric analysis revealed that the addition of PET up to 70% increased the thermal stability of the blend, and adding more than 70% of PET resulted in poor adhesion between the matrix and phase. On the basis of the results obtained, we propose a general understanding of how the morphology and the mechanical and thermal properties of the blend could assist in the development of rPAN blends with PET, rather than disposing of the viable materials as wastes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43777.     

Chemical and thermal characterization of high‐ and low‐density irradiated polyethylenes

A comparative study of the dynamic mechanical relaxation spectra of high‐ and low‐density polyethylenes irradiated with γ‐radiation from a Co⁶⁰ source was performed. The irradiation doses ranged from 0 to 100 Mrad. All the samples were previously characterized by determination of the molecular weight distribution, the number of functional groups, and the crystalline fraction. All the relaxation zones between ?145°C and the melt were studied in the frequency range from 0.3 to 30 Hz. The changes observed in the mechanical relaxation spectra were related to modifications in the chemical structure and morphological parameters attributed to the exposure of the samples to the γ‐radiation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1953–1958, 2002