Synthesis and characterization of fluorine functionalized graphene oxide dispersed quinoline-based polyimide composites having low-k and UV shielding properties

Polyimide nanocomposites having low-k and UV shielding properties have been developed using fluorine functionalized graphene oxide and bis(quinoline amine) based polyimide. The polyimide was synthesized using bis(quinoline amine) and pyromellitic dianhydride at appropriate experimental conditions, and its molecular structure was confirmed through various spectral analysis such as FTIR and NMR. The polyimide (PI) composites were prepared using bis(quinoline amine), pyromellitic dianhydride, and separately filled with 1, 5, 10 wt% of fluorinated graphene oxide (FGO) through in situ polymerization. The polymer composites were characterized using thermo gravimetric analysis (TGA), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). In addition, the water contact angle, dielectric behavior, and UV–Vis shielding behavior of FGO/PI composites were evaluated. The value of the water contact angle of the polyimide was increased with increment of FGO in the polyimide matrix. The highest water contact angle of polyimide composites observed 108° was obtained for 15 wt% FGO reinforced polyimide composite. The value of the dielectric constant for neat, 1, 5, and 15 wt% FGO reinforced polyimide composites was obtained as 4.5, 3.7, 2.6, and 2.0, respectively. It is also observed from by UV–Vis spectroscopy analysis that the FGO reinforced polyimide composites have good UV shielding behavior.     

Bamboo fibers grafted with a soybean-oil-based monomer for its unsaturated polyester composites

A soybean-oil-based monomer, acrylated epoxidized soybean oil (AESO), was grafted onto bamboo fibers (BFs) using 1,6-diisocyanatohexane (DIH) as a linker to facilitate the formulation of a hydrophobic layer on the fiber surface and to impart the fibers with active functional groups that can form chemical connections with unsaturated polyester (UPE) resin. The reaction mechanism of BFs with AESO and DIH and its surface chemical characteristics were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) analyses. These analyses confirmed that the AESO reacted with the DIH and then the resultant AESO-DIH oligomer was covalently bonded onto the BFs via urethane linkages. The grafting of BFs with AESO-DIH resulted in improved tensile and flexural properties, storage modulus, and thermal stability of the BF–UPE composite samples. There were also reductions in the water uptake rate and the diffusion coefficient due to the surface chemical changes of the fibers and thus the enhanced fiber-matrix interface of the composites.     

Effect of alkali treatment on mechanical and thermal properties of Kenaf fiber-reinforced thermoplastic polyurethane composite

In this study, a composite of thermoplastic polyurethane reinforced with short Kenaf fiber (Hibiscus cannabinus) was prepared via melt-blending method using Haake Polydrive R600 internal mixer. Effect of various sodium hydroxide NaOH concentrations, namely 2, 4 and 6% on tensile, flexural and impact strength was studied. Mean values were determined for each composite according to ASTM standards. Tensile, flexural and impact strength negatively correlates with higher concentrations of NaOH. Scanning electron microscope (SEM) was used to examine the surface of both treated and untreated fibers as well as fracture surface of tensile specimens. Morphology of treated and untreated fibers showed a rougher surface of treated fibers. It also showed that some of high concentrations of NaOH treated fibers have NaOH residues on their surface. This was confirmed by energy dispersive X-ray point shooting performed on the same SEM machine. Morphology of surface of fracture indicated that untreated composite had a better adhesion. Treated and untreated fibers as well as composites were characterized using Fourier transform infrared spectroscopy (FTIR). FTIR of treated fibers showed that NaOH treatment resulted in removal of hemicelluloses and lignin. FTIR also showed that untreated composite has more H-bonding than all treated composites. Thermal characteristic studies using thermogravimetry analysis and differential scanning calorimetry showed that untreated composite was more thermally stable than treated composites.     

Chemical Modifications on Linen for Unsaturated Polyester Composites

Linen was chemically modified by oleoyl chloride(OC) and stearoyl chloride(SC) to graft fatty moieties onto fiber via ester connections. Pyridine was used as solvent. The reaction was simplified by reacting the compounds in air at 60℃ for 6 h. Fourier transform infrared spectroscopy(FTIR) and thermal gravimetric analysis were conducted to characterize the treated fiber. The FTIR result confirms that the fatty portions have been successfully grafted onto the fiber after the chemical modification. The thermal stability of the SC-modified linen(SCL) was similar to that of the flax modified by oleoyl chloride(OCL). SCL and OCL demonstrated a temperature of 5% mass loss, which was above 200℃ and could meet the requirements of the processing conditions for most composites. Thereafter, the SCL-reinforced unsaturated polyester(UPE) composites were prepared and characterized. The composite presented a much better impact strength of 61.1 J/m and tensile modulus of 1.69 GPa than those of UPE with applicable thermal stability. SCL has been shown to be a promising choice as reinforcing material for composites.     

Effect of the feeding mode of cross-linker and microcapsule on the corrosion resistance and hydrophobicity of composite coatings

The interface combination of anti-corrosive materials and polymer matrix has a significant effect on the overall performance of the composite coating. However, past research has focused on blending anti-corrosive materials to improve the performance of the polymer matrix. Herein, we proposed a layer-by-layer spray-coating process to further enhance the reinforcing effect of anti-corrosive materials on the polymer matrix by changing their feeding modes. In this paper, taking waterborne polyacrylate (WPA) as an example, two kinds of reinforcement materials commonly used to improve the corrosion resistance of polymer matrix were introduced into the coating system and then applied to the tinplate: cross-linker and microcapsule. Firstly, five types of WPA composite coating systems were designed according to the feeding mode of aziridine cross-linker and the position of benzotriazole@zinc oxide microcapsules (BTA@ZnO MCs). Electrochemical impedance spectroscopy (EIS) and electrical equivalent circuits were used to evaluate the corrosion resistance of these composite coating systems and analyze their electrochemical processes. By spraying the mixture of WPA and aziridine crosslinker as the bottom layer and BTA@ZnO MCs as the top layer, the resulting composite coating exhibited higher corrosion resistance and hydrophobic properties. Scanning electron microscope (SEM) and contact angle tests indicated that the feeding mode of aziridine cross-linker and the position of BTA@ZnO MCs played important roles in the compactness and hydrophobicity of the composite coating. Subsequently, the effects of the amount of aziridine cross-linker and BTA@ZnO MCs on the corrosion resistance and physical properties of the composite coating were further analyzed by EIS, water absorption test, contact angle test and atomic force microscopy (AFM). The significant improvement in the corrosion resistance of this composite coating was mainly attributed to the synergistic effect of highly cross-linked network structure and superhydrophobic surface.     

Hydrophobicity modification of woven cotton fabric by hydrophobic fumed silica coating

Water repellency of woven cotton fabric was achieved by coating with the aqueous dispersion containing organosilane agent (HDTMS) and fumed silica. The coating agents were applied using padding method and then followed by batching the coated fabric at the ambient temperature for 24 h to allow the condensation reaction between HDTMS silanol group and fumed silica silanol group, rendering silica particles hydrophobic. An ultrasonicator was employed to prepare the homogenous coating dispersion. The water repellency evaluated by water contact angle determination which showed the contact angle over 110° was obtained with low amount of applied HDTMS of 1 wt%. The effect of fumed silica addition on an increase in fiber surface roughness geometry showed the influential result in improving the water contact angle. From durability to washing test, the hydrophobic coatings evidenced from SEM and ATR/FTIR remained adhering to fiber surface, indicating the durability. After washing, the coating on the fabric with fumed silica addition appeared to be scatter particles which made a contribution to the higher contact angle value when compared to sheet-like layer coating in case of HDTMS coating alone.     

Thermomechanical and shape memory properties of SCF/SBS/LLDPE composites

A thermally triggered shape memory polymer composite was prepared by blending short carbon fiber (SCF) into a blend of poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS)/linear low density polyethylene (LLDPE) prior to curing. These composites have excellent processability compared with other thermosets. The dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were investigated to assess the thermomechanical properties of the SCF/SBS/LLDPE composite. Scanning electron microscope (SEM) imaging of the samples was performed to show the distribution of the SCF in the composite. The study specifically focused on the effect of SCF on the shape memory behavior of the SCF/SBS/LLDPE composite. The results indicated that the large amount of SCF significantly improved the mechanical property of the polymer composites while not damaging the shape memory performance. The SCF/SBS/LLDPE composites exhibited excellent shape memory behavior when the SCF content was less than 15.0 wt%. Moreover, the shape fixity ratio and shape recovery time of the SCF/SBS/LLDPE composites increased with the SCF content.     

Effect of annealing on hydrophobic stability of plasma deposited fluoropolymer coatings

Fluorinated amorphous carbon (a-C:F) films e.g. plasma polymerised perfluorocyclobutane have long attracted much consideration due to their low surface energy, hydrophobicity, low refractive index, good electrical and thermal insulation and good thermal stability. Although a-C:F films have many advantages, hydrophobic stability over time in air and water remains a major concern. In this study, the effects of weathering conditions on the hydrophobicity of fluorocarbon films prepared from perfluorocyclobutane precursors were examined using water contact angle measurements. It was found that the high initial hydrophobicity of as-deposited films degrades rapidly in humid conditions. The stability of hydrophobicity can be significantly improved when a suitable treatment such as annealing is employed. The mechanism of weathering was explained with the help of a number of morphological and chemical characterisation techniques such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). In particular, XPS results demonstrated that a reduction in the overall amount of -CF₃ radical, oxygenation of surface fluorides and the formation of an overlayer all influence the degradation of fluorocarbon in aquatic environment.     

Thermal,Mechanical and Morphological Properties of Composites Developed from Glycerol and Dicarboxylic Acids Reinforced with Piassava Fiber

Summary: Vegetable fibers are being widely used as reinforcement in polymer composites. These composites can be applied in several fields, such as automotive, packaging and even construction. The polymer matrix used was synthesized from glycerol with phthalic and terephthalic acids in order to open future perspectives in the use of glycerin generated from the production of purified biodiesel. Composites with 2, 5, 10 wt% untreated and treated piassava fiber were obtained. Thermal, morphological and mechanical properties were evaluated. The tensile stress-strain curve of the polyester synthesized and composites was typical of a ductile material. SEM of the surface of fracture showed that the adhesion between fiber and matrix was enhanced after chemical treatment. However, the fiber content was more efficient than the superficial treatment when incorporated into the matrix. Therefore, the material under study is promising for the industrial marketplace, due to its good compatibility with natural fibers.     

Effects of curing agents and modified graphene oxide on the properties of XNBR composites

This paper investigates the effects of crosslinking methods on the incorporation of graphene oxide (GO) in carboxylated nitrile butadiene rubber (XNBR) in the process of producing nanocomposites for chemical-resistant protective clothing and gloves. The novel aspect of the study is a comprehensive approach involving both unmodified GO as well as GO that was carboxylated to increase its affinity to XNBR and to facilitate its application. The nanostructure of XNBR composites was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Fourier transform infrared spectroscopy (FTIR) was used to elucidate the chemical structure of the composites. Thermal stability studies were performed using differential scanning calorimetry (DSC). The barrier properties of the composites were determined based on swelling, crosslinking density, and permeation by mineral oils. The mechanical tests included resistance to puncture and abrasion, stress at strain, and tensile strength. Contact angle was measured to determine the degree of hydrophobicity of the obtained composites.AFM and SEM images revealed the effects of different curing agents (sulfur, magnesium oxide, or a hybrid system) as well as GO type on the surface morphology of XNBR composites. The type of curing agent was found to affect the kind of crosslinks formed and their spatial network structure, as confirmed by FTIR. The DSC curves showed that the crosslinking methods of XNBR did not affect glass transition temperature, but led to large changes observed in the temperature range of 130–220 °C.The type of crosslinking method affected the degree of swelling. It was found that the incorporation of carbon nanofillers led to an improvement in the abrasion and puncture resistance as well as tensile strength of XNBR composites. The water contact angle of the composites indicated hydrophobicity. The properties of XNBR composites containing GO revealed their substantial application potential in protective clothing.     

溶液共混法制备聚苯乙烯/多壁碳纳米管复合导电材料

碳纳米管(CNTs)自从1991年被发现以来,以其特有的力学、电学和化学性能以及独特的准一维管状分子结构和在未来高科技领域中所具有的许多潜在应用价值,迅速成为化学、物理及材料科学领域的研究热点[1]。碳纳米管的C-C共价键链段结构与高分子链段结构相似,能通过配位键作用与高分     

Effective sequestration of Congo red dye with ZnO/cotton stalks biochar nanocomposite: MODELING,reusability and stability

Widespread application of dyes and disposal of their untreated effluents into water bodies adversely affect the ecosystem due to their complex aromatic structures and persistent nature. The present study aims to utilize the cotton stalks biochar (CSB) and its composite with zinc oxide nanoparticles (CSB/ZnONPs) to evaluate for the decontamination their batch scale potential of Congo red dye from wastewater. The characterization of CSB and CSB/ZnONPs was performed with Fourier-transform infra-red (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDX) and point of zero charge (PZC) to get insight of their potential for the decontamination of CR. The effects of initial CR concentration (25–500 mg/L), dosage of CSB and CSB/ZnONPs (0.5–2 g/L), solution pH (2–10) and contact time (0–180 min) were evaluated on CR removal at temperature (25 ± 1.5 °C). The results disclosed that CSB/ZnONPs showed excellent adsorption potential (556.6 mg/g) in comparison with CSB (250 mg/g) and most of the other adsorbents previously studies in the literature. The equilibrium experimental data were equally explained with Freundlich and Langmuir isotherm models (R² > 0.98) while kinetic data demonstrated the best fit with pseudo second order model. The CSB/ZnONPs composite exhibited excellent reusability (89.65%) after five adsorption/desorption cycles for the sequestration of CR from contaminated systems. The present study demonstrated that metallic nanocomposite of CSB (CSB/ZnONPs) is an excellent candidate for the cost effective and environment friendly decontamination of CR from industrial wastewater and is suggested to be considered for the decontamination of other pollutants from the wastewater.     

Superabsorbent Capability and High Retention Ability of China Clay (Kaolinite)/Polyacrylic Acid Composites for Aqueous Solution

Majority of superabsorbent polymers (SAPs) yet reported either have low gel strength or high production cost. Therefore, we synthesized a novel polyacrylic acid-grafted China clay (Kaolinite) super-absorbent polymer composite (SAPC) with high thermal stability, low cost of production and superior sorption and retention capability for water and salt solution. The resulting SAPCs were extensively characterized and analysed by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results suggested that the composites were thermally stable. Water absorbency increased with increase of clay content up to 45%, while further increase in clay content decreased the water absorbency. Percentage of acrylic acid (AA) and clay by weight shows the optimum absorbency in 35% and 40% respectively. Crosslinker and initiator contents were optimized to be 0.5% and 0.3% by weight respectively. The resulting polymer composite showed high water absorbency of about 785 g/g and 103 g/g of 1% NaCl solution with above 90% retention ability at 50 oC.     

连续纤维增强含二氮杂萘酮联苯结构聚芳醚砜酮树脂基复合材料的界面

利用射频感性耦合冷等离子体(ICP)处理技术改性连续纤维表面,分别采用X射线光电子能谱(XPS)、原子力显微镜(AFM)及动态接触角分析(DCA)系统研究了等离子体处理时间、放电气压、放电功率等工艺参数对连续碳纤维、芳纶纤维和对亚苯基苯并二噁唑(PBO)纤维的表面化学成分、表面形貌、表面粗糙度及表面自由能的影响.研究结...     

Effect of graphene quantum dots on photoluminescence property of polyvinyl butyral nanocomposite

Design and development of new photoluminescence system are much in demand for various engineering and technological applications. The present investigation focused on the influence of graphene quantum dots (GQDs) dispersion in the polyvinyl butyral (PVB) matrix. The structural and chemical interaction of GQD‐dispersed PVB composites was confirmed by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), micro‐Raman spectroscopy, ultraviolet and visible (UV‐Vis), and photoluminescence (PL) techniques. Chemical interaction between the functional groups leads to PL quenching at 455 nm. Changes on crystallite size and interplanar spacing hinders on the structural properties of the nanocomposite. Raman spectroscopy reveals the decrease in D/G intensity ratio influenced by GQD loading wt% in the polymer system. The dispersion and occupied network of GQD in the PVB matrix was confirmed by optical polarizing microscopy (OPM), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Effect of electrical conductivity of composites as a function of temperature has been verified. Decrease in direct bandgap as a function of GQD loading confirms the promising PL properties of the prepared composite system. Thus GQD‐derived composites may further be developed as a membrane for improved PL property.     

Synthesis and properties of clay-based superabsorbent composite

A novel superabsorbent composites based on acrylic acid, acrylamide, and inorganic clay mineral-attapulgite were synthesized through a solution polymerization to improve water and saline absorbencies. The superabsorbent composite was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The effects of saline solutions, amount of initiator, crosslinker and attapulgite on the water absorbency of superabsorbent composites were investigated. The water retention test of superabsorbent composites were also carried out. The superabsorbent composite exhibited improved water and saline absorbencies compared with that of crosslinked poly(acrylic acid-co-acrylamide) superabsorbent polymer. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% reaches more than 1400 g H₂O/g and 110 g H₂O/g in distilled water and 0.9% NaCl solution, respectively.     

Improvement of PBO fiber surface and PBO/PPESK composite interface properties with air DBD plasma treatment

The interface of fibrous composites is a key factor to the whole properties of the composites. In this study, the effects of air dielectric barrier discharge (DBD) plasma discharge power density on surface properties of poly(p‐phenylene benzobisoxazole) (PBO) fiber and the interfacial adhesion of PBO fiber reinforced poly(phthalazinone ether sulfone ketone) (PPESK) composite were investigated by several characterization methods, including XPS, SEM, signal fiber tensile strength, interlaminar shear strength, and water absorption. After the air DBD plasma treatment at a power density of 41.4 W/cm³, XPS analysis showed that some polar functional groups were introduced on the PBO fiber surface, especially the emergence of a new oxygen‐containing group (?O–C = O group). SEM observations revealed that the air DBD plasma treatment had a great influence on surface morphologies of the PBO fiber, while the signal fiber tensile strength results showed only a small decline of 5.9% for the plasma‐treated fiber. Meanwhile, interlaminar shear strength value of PBO/PPESK composite was increased to 44.71 MPa by 34.5% and water absorption of the composite decreased from 0.46% for the untreated specimen to 0.27%. The results showed that the air DBD plasma treatment can effectively improve the properties of the PBO fiber surface and the PBO/PPESK composite interface. Results obtained from the above analyses also showed that both the fiber surface and the composite interface performance would be reduced when an undue plasma discharge power density was applied. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,adsorption and adhesive properties of a cationic amphiphilic block copolymer for use as compatibilizer in composites

In this work, the objective was to synthesize a compatibilizer that can electrostatically adsorb onto cellulose fibers, in fiber-based composites, to enhance the interaction between the fibers and non-polar polymer matrices. This physical route to attach the compatibilizer onto and thereby modify a fiber surface is convenient since it can be performed in water under mild conditions. Polystyrene (PS) was used for the high molecular weight, non-polar, block and poly(dimethylamino)ethyl methacrylate (PDMAEMA) was used as the polar block, which was subsequently quaternized to obtain cationic charges. The block copolymer self-assembles in water into cationic micelles and the adsorption to both silicon oxide surfaces and cellulose model surfaces was studied. The micelles spread out on the surface after heat treatment and contact angle measurements showed that the contact angles against water increased significantly after this treatment. AFM force measurements were performed with a PS probe to study the adhesive properties. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglements between the polystyrene blocks at the treated surface and the probe. This demonstrates that the use of this type of amphiphilic block copolymer is a promising route to improve the compatibility between charged reinforcing materials, such as cellulose-based fibers/fibrils, and hydrophobic matrices in composite materials.     

Octahedral oligomeric silsesquioxane (OAPS and OG) - Polyimide hybrid nanocomposite films: Thermo-mechanical,dielectric and morphology properties

Abstract

The nano-sized SQS based polyimides have been successfully synthesized with different oxide groups such as phosphineoxide, sulfone and siloxane as in the backbone of polymer. The SQS-Polyimide nanocomposites prepared through the condensation process using amine and epoxy functionalized SQS as precursor. The presence of SQS in the resulting polyimide nanocomposites was confirmed by FTIR and XRD analyses. The presence of SQS and greatly enhances the char yield to an extent of 16% when compared to that of neat polyimide. The incorporation of SQS into polyimide lowered the value of dielectric constant from 3.31 to 2.09 at 1?MHz and the value of thermal expansion coefficient from 56.6 to 42.7?ppm/K. The composites sample prepared using 20?wt% SQS possess the lowest value of dielectric constant and CTE value. The hydrophobic nature of SQS contributes to lower the water uptake of composites from a value of 2.76 (neat polyimide) to 2.42 for POS-PI containing 20?wt% SQS. Further, the SQS polyimide composite systems possess the enhanced values of thermal stability and glass transition temperatures according their percentage weight. Data obtained from different studies, it is suggested that these hybrid composites can be used as an effective insulation materials for high performance microelectronics applications.     

Surface grafting of bamboo fibers with 1,2-epoxy-4-vinylcyclohexane for reinforcing unsaturated polyester

The present study focused on the surface treatment of bamboo fibers (BFs) with a bifunctional monomer, 1,2-epoxy-4-vinylcyclohexane (EVC), in the presence of N, N-dimethylbenzylamine as the catalyst, which results in the grafting of the fibers with C=C bonds on the surface. The modified BFs carrying C=C bonds were used to prepare bamboo fibers reinforced unsaturated polyester (UPE) composites by hand lay-up compression molding. Hence, chemical connections between the modified-fibers and UPE resins were formed via the free-radical polymerization of the C=C bonds during the preparation of the BFs–UPE composites. XPS analysis proved that the EVC was covalently bonded onto BFs. XRD analysis revealed that EVC-grafting did not alter the crystal structure of the fibers, but slightly decreased their crystallinity degrees. SEM images indicated an markedly improved interfacial adhesion between BFs and UPE matrices after fiber modification, which significantly increased the tensile strength, flexural strength, flexural modulus, storage modulus, glass transition temperature, and water resistance of the resulting BFs–UPE composites.