Iranian Polymer Journal最新文献

Carbon fibers (CFs) can usually only be used to reinforce polar (or non-polar) resins, and if they are to be used for reinforcing with another polymer type, they need to be surface-modified, which will inevitably damage the surface of the carbon fibers and thus reduces the overall performance of the composite. In this work, graphene oxide was first prepared and modified, and then two polymer brushes, polystyrene (PS) and hydroxypropyl polyacrylate (PHPA) were grafted onto its surface in a one-step process. This approach reduced the damage caused to the CFs surface by multiple treatments and improved the interfacial adhesion between CFs and different resin matrices. An electrophoretic deposition method was used to deposit the modified GO on the surface of CFs, which can form strong interaction between CFs and a variety of resins. The results showed that different molecular chains have been grafted on the surface of GO, and then the latter was uniformly deposited on the surface of CFs, improving their surface toughness. Additionally, when the suspension concentration was only 1 mg/mL, the interfacial shear strength (IFSS) of CF/epoxy and CF/PP increased by 52.0% and 26.5%, respectively. This means that a small amount of GO can significantly improve the interfacial properties of carbon fiber reinforced composites (CFRCs). Therefore, they can be applied to aerospace, wind energy and other industries to effectively improve the interfacial bonding between fiber and resin, after surface modification.

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It was reported that various studies have been carried out to increase the strength, permeability and durability performances of lightweight concrete (LC) mixtures. Extensive research was carried out on the production of sustainable and ecologic LC. In this context, the use of various innovative materials and methods have been demonstrated. In this direction, increasing the service life of concrete produced by the use of fiber, nanomaterials and self-healing with bacteria is one of the applied methods. In this study, the effects of the use of fiber, nanomaterials and bacteria on the workability, unit weight, strength, toughness, modulus of elasticity, impact resistance, permeability, drying-shrinkage, freeze–thaw, high temperature resistance, thermal conductivity performance of LC mixtures have been compared in detail. It was reported that workability, specific gravity, permeability, thermal conductivity and drying-shrinkage values decrease, while strength, high temperature resistance, freeze–thaw resistance and toughness performance increase with the addition of fiber and nanomaterials to LC mixtures. While it was emphasized that the strength and permeability performance and elasticity modulus values of the mixtures increased with the addition of bacteria. In addition, the use of fiber has insignificant effect in terms of the modulus of elasticity.

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The effect of incorporation of barley husk (BH) grafted with different fatty acids (lauric acid: LBH; palmitic acid: PBH; arachidic acid: ABH) on the physicochemical properties of cross-linked PVA/starch based composite films was studied at different loadings (0.2–2)%. Surface morphology of the films showed that grafted BH dispersed well within the matrix as compared to BH enabling them to provide the greatest reinforcing effect. Composite films containing grafted BH showed higher tensile strength, water resistant properties, thermal stability as well as barrier properties compared to composite films containing BH. At optimum loading (1%), tensile strength of the composite film, containing ABH, was 22.9 MPa, and 23.5% and 31.6% higher than films containing LBH (17.4 MPa) and PBH (18.54 MPa), respectively. Composite films prepared with ABH exhibited the highest values of water contact angle, water vapor, and oxygen permeability among all composite films owing to the incorporation of longest hydrophobic aliphatic chain and provides more hindrance for transmission. The activation energy values of thermal degradation for composite film directly indicate their thermal stability were calculated as 203.37, 222.62 and 366.52 kJ at 1% loading of LBH, PBH, and ABH, respectively. Thus, composite film containing ABH at 1% showed maximum improvement in physicochemical properties followed by composite films containing 1% PBH and LBH. This study provides the alternatives for choosing the most effective composite film, which can be a nature-friendly substitute for non-degradable packaging films and it may help to maintain the circular economy.

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In this work, we described the structural modification of palygorskite (Pal) and its use in the preparation of flame retardant (FR) additives. Theses FR additives were prepared by an encapsulation process involving in situ polymerization reaction between melamine and diisocyanate. The structural modification of Pal and the encapsulation process were characterized by FTIR and SEM techniques. These FR additives were incorporated into polymer blends of poly(lactic acid) (PLA) and ethylene vinyl acetate (EVA) by melt mixing. The compounds obtained from mixing FR additives and PLA/EVA were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), cone calorimetry, limiting oxygen index (LOI), and plastics flammability standard (UL 94, HB). The incorporation of FR additives showed a significant change in the thermal properties of the PLA/EVA composites. We observed a marked reduction in the peak heat release rate during cone calorimetry tests and significant increase of LOI value. A reduction in the horizontal burn (HB) rate was also observed in the UL-94 test. The results obtained confirmed the notable increase in thermal stability and FR characteristics of the PLA/EVA composite, which was attributed to the formation of a homogeneous protective carbon layer on the surface of the composite samples. This composite showed excellent FR characteristics with good mechanical properties, which is a good option to obtain flame retardant composites with better performance. These results demonstrated that this methodology is a promising way to meet the growing demand for high-performance materials with flame retardant characteristics, using composites with sustainable and ecological materials.

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3D printing, particularly “fused filament fabrication” (FFF), plays a crucial role in Industry 4. FFF is widely used for creating complex structures and multi-material parts across various industries such as food industry, fashion industry, and manufacturing sectors. The properties of FFF-produced objects are remarkably affected by printing parameters. This study explores the impact of printing parameters and the addition of short carbon fibers on the strength of polylactic acid (PLA) printed samples. The lowering layer height, increasing feed rate and extrusion temperature boost impact strength, while a smaller raster angle enhances it. Meanwhile, an improved flexural strength is achieved by adjusting layer height, extrusion temperature, and raster angle. Higher extrusion temperatures enhance tensile strength, microstructure, and reduce porosity. Lower layer height improves flexural and impact strength (28.05% increase in 0.1 mm layer height), higher feed rate boosts strengths (12.56% improvement in 7 mm³/s feed rate), and elevated extrusion temperatures enhance impact strength (14.49% increase in 230 °C extrusion temperature) but reduce flexural strength (14.44% decrease). Incorporating carbon fibers in PLA negatively affects the microstructure but increases crystallinity, raising the melting temperature and lowering cold-crystallization temperature. The introduction of carbon fibers into PLA results in a complex interplay of mechanical and thermal properties.

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The development of durable and effective antibacterial materials has been a research hotspot. Here, we reported a new kind of long-lasting stable antibacterial material [Cu-metal–organic framework (MOF)-embedded polyethylene (PE)/ethylene vinyl acetate copolymer (EVA), namely Cu-MOF-embedded PE/EVA] through extrusion foaming, and its structure was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and energy dispersive spectroscopy (EDS). The degree of agglomeration or cluster formation, thermal stability, and melting point temperature of different contents of Cu-MOF/PE/EVA foams were evaluated by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC), respectively. The results indicated that with the increase of Cu-MOF content, the average size and swelling ratio for foams increased, instead, the density decreased. Besides, the surface gradually showed good hydrophobicity. Remarkably, the water absorption rate was nearly 8 times that of pure PE/EVA when the Cu-MOF content reached 3%. Since Cu-MOF is stably embedded in the foaming structure and well dispersed, it can release Cu²⁺ at a rate of about 37 ppb/day in foams containing 3% Cu-MOF, which not only maintains the antimicrobial capacity up to 99.2%, but also have no cytotoxicity. Finally, a promising new candidate for medical material with excellent, durable antibacterial ability was proposed.

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PVC-based nanocomposites with varying concentrations of zinc oxide (ZnO) nanoparticles are fabricated using the melt mixing technique and then subjected to compression molding to acquire desired shapes (circular) and thickness (1.5 mm). Conformational analysis is performed using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, and optical microscopy. The prepared samples are then exposed under UV light having an intensity of 5.11 mW/cm² for 5000 lab hours of aging. The effect of UV aging on the structural and thermal behavior of the nanocomposites is analyzed at every 1000 h. Structural degradation of more than 50% in the case of neat PVC has been observed to be reduced with the increase in filler concentration. The contact angle values for 2, 4 and 6 phr of PVC nanocomposites after 5000 h of aging are 69°, 93°, and 104° having hydrophobicity classes of HC3, HC2, and HC2, respectively. The detailed analysis to study the effect of UV aging on the thermal behavior of the nanocomposites is evaluated using differential scanning calorimetry in the temperature range of 60–220 °C. Finally, the life span of all the samples was calculated using statistical calculations and it was observed that PVC with 2 phr of ZnO showed a maximum lifetime of 17,750 lab hours whereas for PVC with 0 phr of ZnO 8693 lab hours were calculated.

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The exceptional tensile strength and modulus of high-performance carbon fibers are determined by the microstructure evolution during the manufacturing process. The comprehension of the internal morphology of polyacrylonitrile (PAN) fibers is crucial for establishing the robust structure–property relationship and achieving superior mechanical properties in the fibers. In this work, a combination method of the ultrathin sectioning and electron microscopy technique was developed and employed for the analysis of internal structure features of the nascent fibers, precursor fibers, pre-oxidized fibers and carbon fibers. The microfibril elements were already formed during the coagulation stage and further developed within the carbon fibers through spinning, thermal stabilization and carbonization processes. Subsequently, the unoriented microfibrillar network underwent a transformation into dense fibrils, and the crystal layers within these microfibrils experienced a conversion into the turbostratic graphite structures. Based on the Nano-IR2-FS results, the morphological changes of the microfibrils were found to be intricately associated with the evolution of chemical structure, implying a strong correction between them. Through analysis of the modulus differences, it became possible to distinguish between the crystalline domains and amorphous regions, facilitating the establishment of a relationship between the mechanical strength and the microfibril structures. This work presented a direct measurement method for unraveling the complex hierarchical structures of polymer fibers, which held great potential for developing high-performance polymer fibers.

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Sugarcane bagasse (SCB) and pineapple crown leaves (PCL) as low-cost waste biomass generated from the industries were subjected to chemo-mechanical modification to compare the morphology, charge, and thermal stability of native and modified biomass, accompanied by their cellulose-rich fractions. A novel aspect of this research lies in the versatility of the hybrid approach for sustainable production of cellulose polymers from an array of biomass sources. Using scanning electron microscopy (SEM), the surface morphology and structure of the samples were examined. To give thorough insights into the material characteristics, other techniques such as Fourier transform infrared spectroscopy (FTIR), zeta potential, X-ray diffraction (XRD), and thermogravimetric/differential thermal analysis (TG/DTA) were used. According to the findings, after being exposed to the hybrid treatment, the modified sample had a more ordered crystalline structure than the raw biomass (supported by the FTIR spectra), the XRD results indicated that the crystallinity index (CrI) raised with crystallite size. Although the cellulose-rich fraction extracted by the hybrid method showed better thermal stability, the overall thermal analysis revealed that biomass produced by the hybrid method had lower thermal stability than the raw biomass. The current work showed that combining ultrasonication with sulfuric acid hydrolysis is a successful hybrid method for separating cellulose nanofibers from the cellulosic plant fiber sources for reinforced composite products.

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Natural fiber composites often exhibit significant acoustic behavior in low-frequency range. The focus of this study is to create soundproof panels using luffa and Kevlar fiber composites reinforced using nanoclay (MMT) filler. Mechanical testing was performed on the prepared samples. The addition of 4% MMT improved the mechanical characteristics. Mechanical parameters such as interlaminar shear, tensile, flexural, and impact strength were enhanced by 9.13%, 16.89%, 9.71% and 51.64%, respectively, as compared to the control sample. Tribological experiments were performed on the manufactured composite samples in dry sliding conditions as a function of control factors such as sliding speed, sliding distance, and effective load. The results reveal that using 6% MMT to Kevlar/LCF epoxy composites greatly increases the COF and specific wear rate. The sound absorption test results indicated that the incorporation of nano MMT with Kevlar/LCF composites increased the sound transmission loss. The reduced hydrophilicity effect has been reported with the addition of 4% (by weight) MMT in contact angle measurement studies. Moreover, the created biocomposites are low-cost and long-lasting materials suitable for use as soundproofing panels in automobiles and railway cabins.

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