Journal of Polymer Research最新文献

Annealing is a heat treatment process for materials. In this study, a conductive hydrogel was synthesized by a one-pot method using three raw materials: polyvinyl alcohol(PVA), carboxylated carbon nanotubes(Multi-Walled Carbon Nanotubes-COOH, MWCNTs-COOH) and polyethyleneimine (PEI). Based on the traditional freeze-thaw method for the preparation of PVA-based hydrogels, the annealing treatment was further added here to enhance the mechanical properties and fatigue resistance of the hydrogels. The synthesized conductive hydrogels were annealed in oven at different temperatures for a certain time, and the optimized experimental conditions and results were: the mechanical properties of the conductive hydrogel were best improved under the condition of 100 ℃-20 min, with the ultimate stress of 30.8 MPa and toughness as high as 779.58 MJ/m³. A high-strength, fatigue-resistant conductive hydrogel was successfully prepared, and its mechanical properties far exceeded those of other conductive hydrogels. Through a series of tests such as X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), it was found that annealing promotes the orderly arrangement of PVA chains and crystallization through high temperatures, so as to enhance the mechanical properties of hydrogels. As a relatively simple and inexpensive annealing post-treatment technique, it is expected to be more widely used in improving the mechanical properties of hydrogels.

This study examines the impact of gamma radiation on the mechanical characteristics of carbon/Kevlar hybrid epoxy composites used in aerospace applications. Composites consisting of carbon (CCCC), Kevlar (KKKK), and hybrid (CKCK) fabrics with varied stacking sequences were produced using a hand lay-up technique. These composites were then exposed to different dosages of gamma radiation (1 kGy, 3 kGy, and 5 kGy ). A thorough mechanical analysis was conducted, encompassing tests for tensile strength, flexural strength, impact resistance, interlaminar shear strength (ILSS), hardness, and water absorption. The carbon composite that was not exposed to radiation demonstrated the maximum tensile strength, measuring 246.28 MPa. Additionally, it exhibited a flexural strength of 787.72 MPa and an interlaminar shear strength (ILSS) of 9.75 MPa. After being exposed to a radiation dose of 5 kGy, the values decreased to 215.36 MPa, 578.49 MPa, and 8.71 MPa, respectively. Among the materials that were examined, the hybrid composite had the highest impact strength of 0.0537 J/mm2. The results of dynamic mechanical analysis showed a reduction in the storage modulus from 11762.1 MPa to 10338.7 MPa, and a decrease in the glass transition temperature from 113.05 °C to 107.7 °C following exposure to 5 kGy of radiation. The scanning electron microscopy (SEM) analysis of fractured surfaces revealed a transition from a ductile to a brittle fracture behaviour as the radiation doses increased.

This work introduces the fabrication of eco-friendly poly (ε-caprolactone) based polymeric membranes for water filtration applications by a non-solvent induced phase inversion method by using N-methyl pyrrolidone as solvent and water as non-solvent. The membranes are prepared with good morphological features and permeation properties to fit filtration applications by varying the polymer concentration in the dope solutions in the range of 10-18%. The thermal, mechanical, chemical composition, and surface roughness properties of the fabricated poly (ε-caprolactone) membranes were studied by thermo gravimetric analysis (TGA), universal testing machine (UTM), fourier transform infrared spectroscopy (ATR-FTIR), and atomic force microscopy (AFM) respectively. Morphological studies of the membranes showed a porous asymmetric structure with different skin layer morphology. Precipitation kinetics studied by cloud point measurement showed instantaneous demixing during precipitation resulting in fingerlike morphology. Hydrophilicity and the performance of the prepared membranes for filtration applications were analyzed by contact angle measurements, equilibrium water content, porosity, and pure water flux. Pore size measured using ImageJ software and the Guerout–Elford– Ferry equation assures the utility of the membranes for the microfiltration process. The soil degradability of the fabricated membranes was also evaluated and the efficiency of the fabricated membranes for oil/water separation was studied with olive oil-water emulsion. All the results obtained revealed the dependence of membrane properties and performance on the casting solution composition.

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The effects of flower-shaped hybrid nano biocatalyst (hFe-NFs) from coordination between horseradish peroxidase (HRP) enzyme and Fe²⁺ ions on the free-radical polymerization reactions of three different vinyl monomers (styrene, methylmethacrylate and acrylamide) were investigated. Polymerizations of styrene and methylmethacrylate (MMA) were performed under emulsion conditions using three different surfactants in the presence of acetylacetone (AcAc) and hydrogen peroxide (H₂O₂) initiator. Polymerization of water soluble acrylamide was accomplished under surfactant-free media. According to the obtained outcomes, hFe-NFs exhibited higher catalytic activity towards polymerization of vinyl monomers compared to the free-HRP enzyme in terms of yields and the number average molecular weights (M_n) of the synthesized polymers. hFe-NFs also demonstrated very high thermal stability. While optimum polymerization of styrene was achieved at room temperature (RT), the highest polymerization yields for acrylamide and MMA were respectively accomplished at 70 and 60 ºC in which free-HRP enzyme loses its catalytic activity. Preparation of the flower-shaped hFe-NFs, therefore, enables inexpensive and stable catalyst system for free-radical polymerization of vinyl monomers compared to free-HRP enzyme. Increasing catalytic activity and stability of hFe-NFs at higher reaction temperatures are very crucial for utilization of these types of catalysts in both scientific and industrial purposes.

In this study, gallic acid-g-chitosan colored complex were produced using the HRP-catalyzed method. Then, these were used to successfully dye silk fabrics. The dyed silk fabrics were characterized through K/S, color fastness, and antibacterial tests. We studied the polymerization mechanism in detail using FT-IR and ESI-MS technologies, then the dyeing process and optimum reaction conditions were further investigated using the K/S values. Chitosan and gallic acid were polymerized to form a dark yellow polymer, which was successfully colored on silk fabrics. In addition, significant color differences were observed between fabrics dyed without chitosan and fabrics dyed in the presence of chitosan. In particular, the fabric treated with the pre-polymerization dyeing process showed high antibacterial properties, color fastness, and color depth compared to other dyeing processes. We found that the optimum reaction conditions for dyeing silk fabrics are as follows: 3-hour incubation period, 50 ℃ temperature, 3 mM gallic acid; 3 g/L chitosan. While the GA and CS pre-treatment or co-treatment process resulted in lower color fastness, the pre-polymerization approach offered enhanced fastness and overall performance. Based on the findings, the pre-polymerization process is recommended as the most effective method for dyeing silk fabrics with chitosan and natural dyes, optimizing both aesthetic and functional properties.

Butacene is a polymeric binder that incorporates ferrocenyl groups chemically bonded to the backbone of the hydroxyl-terminated polybutadiene (HTPB). Given the role of iron as an oxidation catalyst and its potential applications in the aerospace and aeronautics industries, it is important to design a desirable product with improved initial decomposition, increased thermal sensitivity, high thermal stability, and superior catalytic performance. To attain improved desired properties, without compromising the critical physical features of HTPB, herein, a one pot and cost effective synthesis method was employed for this purpose. Iron containing HTPB composite samples, containing 5, 10, 20, 35, and 50 wt% ferrocene, were synthesized through Friedel Crafts alkylation of ferrocene with HTPB while using AlCl₃ as a Lewis acid catalyst. Ferrocene, serving as the source of iron to ensure minimal alteration in the microstructure of HTPB. Confirmation of the chemical structures, elemental composition, and surface morphology of the polymer and Fc-HTPB composite samples was achieved through Fourier transform infrared spectroscopy (FTIR), CHNS/O analysis, and scanning electron microscopy (SEM), respectively. Based on these results, it can be said that the desired composite samples are successfully fabricated. Physiochemical characterization, including tensile strength testing was conducted. Additionally, thermal properties such as thermal stability of the final product were studied through thermogravimetric analysis (TGA), Furthermore, rheological investigations, including viscosity, loss and gain moduli of HTPB and the newly synthesized composite samples (Fc-HTPB) were carried out. Based on the comprehensive physiochemical results obtained, it was observed that addition of ferrocene (Fc) to HTPB and also by changing the ratio of Fc/HTPB could enhance the desired physiochemical behaviour of the Fc-HTPB composite. This study also offers a potential pathway for proposing and recommending a composite formulation with enhanced cumulative properties for use as a catalyst to accelerate burning rates in future propellants.

Chain conformation and molecular parameters of three different polyamic acids (PAA), including (6FDA − DMB) PAA, (6FDA − TFDB) PAA and (Ultem 1000) PAA were investigated by gel permeation chromatography coupled with multi − angle laser light scattering detector, viscosity detector, and differential refractive index detector (GPC − MALLS − VIS − RI) using 0.02 M LiBr/0.20 M HAc/DMF as mobile phase. The weight-average molecular weights of the PAAs are 220.2–293.9 kg/mol. The scaling exponents ν obtained by the scaling relationship between the root-mean-square radius of gyration (R_g) and molecular weight (M) are 0.59, 0.59, and 0.57 and the scaling exponents α obtained by the Mark − Houwink − Kuhn − Sakurada (MHKS) relations are 0.78, 0.78, and 0.74 for (6FDA − DMB) PAA, (6FDA − TFDB) PAA and (Ultem 1000) PAA, respectively. These scaling relationships indicate that all three polyamic acids with different structures have a random coil conformation in the mobile phase. The persistence lengths l_p estimated based on R_g through a Kratky-Porod wormlike model are 2.3, 2.1, and 1.6 nm, and estimated from intrinsic viscosity through a Bohdanecky approach are 1.9, 1.8, and 1.7 nm for (6FDA − DMB) PAA, (6FDA − TFDB) PAA and (Ultem 1000) PAA, respectively. These results imply that the three PAA show a characteristic of a flexible chain with local rigidity in the mobile phase. The (Ultem 1000) PAA always has the smallest l_p among the three PAA samples, which may be attributed to a flexible ether linkage in the backbone.

The tyre industries are now thriving towards the concept of sustainability in every aspect of their product realization to prevent the harmful effects of greenhouse gas emissions. This initiated the urge for a global decarbonization movement and the researchers have explored a plethora of filler materials for a sustainable circular economy. In this perspective, the prime objective of the present work is focused on the optimization of natural rubber/polybutadiene (NR/BR) blend composition for the successful incorporation of thermally exfoliated graphite (EG). The preparation of the polymer blend of NR with BR improved the processability as well as abrasion resistance of the overall tyre tread compounds. Optimization of the NR/BR blend ratio at 60/40 synergistically improved the overall output properties in terms of rheological, mechanical as well and tribological characteristics. Partial replacement of BR with epoxidized natural rubber (ENR) offers dual functions to the composite such as both compatibilizer and matrix material. The low rolling resistance (0.040) and mechanical performances were balanced through the partial replacement of carbon black with thermally exfoliated graphite which in turn effectively transferred the stress between the filler material and the polymer matrix. Incorporation of 10phr of thermally exfoliated graphite into the NR/BR blend also lowers the Payne effect to a minimum level indicating excellent filler–polymer interaction in the composite.

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Direct discharge of Congo red (CR) dye wastewater can cause environmental pollution. Herein, magnetic polyacrylamide/sodium alginate/Fe₃O₄@ZIF-8 (PAM/SA/Fe₃O₄@ZIF-8) hydrogel beads with semi-interpenetrating polymer network (SIPN) structure were prepared by combining the properties of PAM/SA hydrogel and Fe₃O₄@ZIF-8 for removal of CR. The magnetic hydrogel beads were characterized by SEM, EDS, FTIR, XRD, and BET. The effect of different factors on the adsorption of CR by magnetic hydrogel beads was investigated. The results showed that the addition of Fe₃O₄@ZIF-8 improved the adsorption capacity of PAM/SA hydrogel beads and the maximum adsorption amount of CR by magnetic PAM/SA/Fe₃O₄@ZIF-8-8 was 234.69 mg g⁻¹. The adsorption of CR on PAM/SA/Fe₃O₄@ZIF-8-8 complied with the Pseudo-second-order kinetic model and Freundlich model. Thermodynamic analyses indicated that the adsorption process was endothermic and spontaneous. The adsorption mechanism of PAM/SA/Fe₃O₄@ZIF-8 on CR was based on electrostatic attraction, metal coordination, hydrogen bonding, and π-π stacking. PAM/SA/Fe₃O₄@ZIF-8-8 had excellent selective adsorption and cyclic regeneration performance for CR removal. This study showed that magnetic PAM/SA/Fe₃O₄@ZIF-8 hydrogel beads can be used as a new effective adsorbent for the recovery of CR in wastewater.

The increasing electromagnetic (EM) radiation pollution necessitates the development of low-cost, lightweight, and high absorption-dominated electromagnetic interference (EMI) shielding composites. Herein, the isotactic polypropylene (iPP)/high-density polyethylene (HDPE)/carbon nanotubes (CNTs) nanocomposite foams were fabricated using a simple melt blending method, followed by an eco-friendly foaming process with supercritical CO₂ as the blowing agent. The asymmetric bilayer structure of resulting iPP/HDPE/CNTs nanocomposite foams was produced by integrating iPP/CNTs and HDPE/CNTs segments, followed by a foaming process. Due to the different melt strength and viscoelasticity of iPP and HDPE, this asymmetric bilayer nanocomposite foams with identical CNTs content exhibited diverse structures and unique EMI shielding properties. Specifically, the HDPE/CNTs layer served as an absorption layer due to its relatively low electrical conductivity, whereas iPP/CNTs layer functioned as a reflective layer owing to its high electrical conductivity, leading to the formation of a distinct absorption-reflection-reabsorption interface within the iPP/HDPE/CNTs nanocomposite foams. Finally, the unique asymmetric structure endowed the nanocomposite foams with superior EMI shielding effectiveness of 37.32 dB, as well as a high absorption coefficient of 0.60, rendering the nanocomposite foams absorption-dominated EMI shielding materials and effectively preventing secondary EM wave pollution.