Presence Of Coupling Agent Research Articles

The coupling agents’ effects on the BSA intercalated into montmorillonite

The effects of surface modification on montmorillonite (MMT) were illustrated in order to produce the composite material with premium properties. MMT was treated with two coupling agents: glutaraldehyde (GA) and γ-methacryloxy-propyl-trimethoxy silane (KH570). The effects of different coupling agents on MMT and protein interaction were investigated by XRD, FT-IR, TGA, UV-Vis, etc. The results of structure characterization indicated that KH570 modification could change the surface crystal structure of MMT. However, GA reacted with amino groups of Bovine serum albumin (BSA) and the ordered layer structures of MMT were not completely destroyed. Coupling agents could greatly increase the amounts of BSA intercalated and the effect of KH570 is better than that of GA. And, the optimum concentrations of KH570 and GA were 2% and 6%, respectively. The rate of weight loss increased by about 12% after MMT was pretreated with coupling agents. The possible reason is that coupling agent treatment makes the structure of MMT more accessible to protein absorption and helps to stabilize the protein structure. Moreover, the presence of coupling agents can reduce the direct chemical interaction between BSA and MMT, which results in increasing protein desorption.

Preparation of Crack-Free Nanocomposite Ceramic Membrane Intermediate Layers on α-alumina Tubular Supports

The objective of this work was to develop a crack-free membrane intermediate layer on tubular ceramic supports via dip-coating. TiO2 submicron powder, Boehmite as a coupling agent, and SiO2 nanopowder as low melting-point sintering aid were used to deposit a thin and crack-free nanocomposite layer onto α-Al2O3 supports. Effects of key parameters such as solid content, number of coated layers, the presence of coupling agent, and a low melting point nanopowder on physicochemical properties like the thickness, microstructure, pore size, pure water flux, and gas permeance of the final modified ceramic supports were investigated. The obtained results showed that after twice coating of support in 3 wt.% bidispersed TiO2-Boehmite suspension, the pore size of the alumina substrate, ∼0.6 micron, was reduced to ∼0.1 by the uniform membrane intermediate layers with low permeation resistance could be prepared. Moreover, by adding SiO2 nanopowder, sintering temperature of intermediate layers decreases considerably (1000 to 700°C).

Tensile and impact properties of polypropylene/microcrystalline cellulose treated with different coupling agents

The effects of different coupling agents, silane aminopropyltriethoxysilane and maleic anhydride-grafted polypropylene (MAPP), on the mechanical properties of polypropylene (PP)/microcrystalline cellulose (MCC) composites were determined and compared. The composites with low filler loadings, up to 12 wt.%, were prepared via melt-mixing in a twin screw extruder followed by injection moulding. All composites were characterized by tensile and impact tests. It is observed that the addition of MCC slightly decreased the tensile strength but the MAPP composites showed higher tensile strength than the silane composites. In contrast, the silane improved the Young’s Modulus at higher filler content. Additionally, the impact properties increased with the presence of coupling agents. These results indicate that both coupling agents affected the mechanical properties of the composite in different ways associated with different filler content.

Continuous glass fiber reinforced wood plastic composite in extrusion process: Mechanical properties

This paper presents an experimental study on the material development where wood plastic composites (WPCs) were reinforced with continuous glass fibers (continuous hybrid WPC) at a low volume fraction. The continuous glass fiber reinforced WPC (CGFR-WPC) were produced in cylindrical profiles via an extrusion process. Experiments were carried out to investigate the effect of wood content, volume fraction of continuous glass fiber and the presence of coupling agent on the mechanical properties of the final products. Three point bending, tensile and impact tests were carried out on the extruded specimens. The results revealed an outstanding improvement in all the mechanical properties, where applying a low fraction of continuous reinforcement via incorporating six rovings of (continuous) fiber reinforcements into the WPCs, maximum increase in flexural, tensile and impact strength were observed to be 2.3, 5.9 and 20 times, respectively. Achieving these large increases in properties via conventional variations in processing and material parameters has not been reported. It is interesting to note that, when applying a larger number of reinforcements, presence of coupling agent in WPCs, exhibited a negative effect on the tensile properties.

Microwave-acceleration of Carboxamides Formation Using Water Soluble Condensing Agent DMT-MM or DCC

Amide linkages are present in key natural products and in many biologically active molecules. Therefore, the formation of amide bonds is important to both synthetic chemists and biologists. Approximately 66% of all preliminary screening reactions in industrial medicinal chemistry laboratories involve amide formation. Although many methods have been developed for amide synthesis, a procedure for the direct coupling of amines with an acid in the presence of coupling agents without prior activation would be useful for building small-molecule libraries and for key steps in total syntheses. Condensing agents such as carbodiimides or other activating agents are generally employed under dry conditions. However, the condensing agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4methylmorpholium chloride (DMT-MM) can be used to prepare carboxamides in alcohol or water. This reaction is technically simple and relatively easy to implement, requiring only a mixing of acids, amines, and DMTMM in MeOH or H2O. The synthesis of DMT-MM is also relatively simple, and it can be prepared from CDMT (2chloro-4,6 dimethoxy-1,3,5-triazine) and N-metheylmorphorine (NMM) in THF. The current report describes the application of microwave-induced acceleration to further improve the reaction conditions for amide synthesis using DMT-MM. Highspeed synthesis using microwave technology has attracted considerable attention in organic chemistry. Microwave irradiation provides advantages over conventional heating for chemical transformations, including accelerated reaction rates (and consequently reduced reaction times), higher yields, and cleaner reactions. These advantages led us to evaluate the use of microwave irradiation for amidation reactions involving less reactive secondary and primary amines with acid in the presence of DMT-MM. We also compared the effectiveness of dicyclohexylcarbodiimide (DCC), a well-known condensing reagent, when coupled with microwave irradiation versus classical thermal methods. The reactions were performed by dissolving amines, carboxylic acids, and the condensing agent in solvent, followed by irradiation in a temperature-controlled microwave oven. For comparison, the same reactions were carried out under conventional heating conditions. The amidation of 2-phenylethylamine (a primary amine) with substituted benzoic acid in the presence of DMT-MM in MeOH gave a yield of over 90% products within 25 min at 110 C with microwave irradiation. The reaction time with conventional heating was seven times that with microwave irradiation, and the yield was less than 10-20% of the yield with the microwave-assisted method. The reaction of piperidine (a secondary amine) with benzoic acid afforded a 91% yield within 30 min at 150 C with microwave irradiation; note the higher reaction temperature and longer reaction time compared with those of the primary amine reaction. Amidation of piperidine with substituted benzoic acid in the presence of DCC with pyridine in THF yielded more than 60% products within 25 min at 120 C with microwave irradiation. Thus, DMT-MM was a much more effective coupling agent than DCC. Further increases in reaction temperature were limited by the potential of solvents for producing an explosive atmosphere within the micro-

Behaviour of Rice-Byproducts and Optimizing the Conditions for Production of High Performance Natural Fiber Polymer Composites

This present study deals with evaluating some available rice by-products, such as rice straw and rice husks, as a fiber component in manufacturing of high performance natural fiber polymer composites (NFPC). The utilization of these undesirable wastes will contribute to the reduction of the environmental impact of waste disposal by burning. Two matrices (thermoset and thermoplastic) were used. Optimization of manufacture conditions of polyester-based thermosetting polymer composites was carried out through examine the effects of fibers to polymer ratio, amounts of catalyzed and initiator, fraction size of fibers and substituting one fibers by another, as well as time, temperature and pressure of pressing. The possibility of styrene containing polyester solution on improving the fiber interface via in situ grafting and enhancing the strength and water resistance of the produced NFPC was also evaluated, in comparison with that produced from using thermoplastic matrix (polypropylene) in presence of coupling agent. The production of this valuable product (NFPC) by this simple procedure, which not needs special devices (twin extrusion with heater), and chemicals to improve the compatibility between fibers and polymer matrix, will ensure reasonable profits and direct impacts on the Egyptian economy in general and rice growers in particular.

Preparation and Properties of Nanocomposites Consist of Carbon Black N220 and Epoxy Resin

The nanometer carbon black (CB) N220 of different content was employed to prepare carbon black N220/epoxy resin (CB N220/EP) composites by filling-mixing method. The structure of CB N220 and its dispersion in epoxy resin were analyzed by TEM and tensile fracture surface of the composites was analyzed by SEM. Experimental results showed that CB N220 was dispersed in epoxy resin homogenously in the form of CB particles and it formed a good interface with epoxy resin in the presence of coupling agent (KH-550). Using of CB N220 enhanced the mechanical and thermal properties of the composites, for tensile strength, elongation at break, impact strength and flexural strength of the composites filled with 2 wt% CB N220 reached a maximum values( 82Mpa、3％、20 KJ•m-2、107Mpa), a rise of 32.3％、39.6％、88.7％、10.3％, respectively, compared to pristine epoxy resin.

Combined effect of nanoclay and alumina addition on structure, TGA, DMA characteristics of nanoclay, and alumina-filled polypropylene nanocomposites

A series of PP-MA- g-PP/MA- g-EPR – clay/alumina – titanate nanocomposites with varied proportions of clay and alumina composition, maintaining the matrix modifier and coupling agent composition constant, were prepared by melt blending. Two different modifiers, maleic anhydride (MA)-grafted polypropylene (PP) and MA-grafted EPR, along with coupling agent are used in order to improve the dispersibility of reinforcing filler. The resultant nanocomposites in presence and absence of matrix modifiers and coupling agent were compared for their dynamic mechanical and thermal properties. The morphology of nanocomposites was studied by X-ray diffraction and high-resolution scanning electron microscopy. Most of the cases, the combination of intercalated and exfoliated nanocomposites was obtained. Particularly for the sets with titanate, coupling agent showed better dispersion of reinforcing filler. The resultant nanocomposites showed an increase in storage modulus and tan δ values in presence of coupling agents. This reflected as an improvement in load-bearing capacity and stiffness of nanocomposite in dynamic mechanical analysis studies. The matrix modifiers and coupling agent very effectively influenced the thermal transition of nanocomposites. Blending of matrix modifier and addition of reinforcing filler reduced the melting temperature of nanocomposites because of reduction of crystallinity matrix in presence of filler and modifier, whereas incorporation of coupling agent brought the melting temperature back the almost original value of virgin PP. The thermal stability of PP improved 16–37°C by incorporation of reinforcing filler along with coupling agent.

Effect of Silane Coupling Agents on Rice Straw Fiber/Polymer Composites

The effect of coupling agents and electron beam (EB) irradiation dose on the mechanical properties of composites made from rice straw fibers and polymers have been studied. Samples were made by hot pressing of mix composition at 130°C. The pressed samples were subjected to electron beam irradiation dose ranged from 10 to 50 kGy. Increasing the electron beam irradiation dose increased the value of flexural strength, modulus of elasticity and impact strength. It was also observed that, the properties of composites containing γ-aminopropyltrimethoxy silane (A-1100) are lower than those of composites containing N-(2aminoethyl)-3-amino propyltrimethoxy silane (A-700) coupling agents. These are attributed to a hydrogen bonding formation between the amine or protonated amine and the hydroxyl groups of rice straw fibers. The presence of coupling agents in the composites during the EB irradiation process produce a more free radicals which are enough to form a chemical bonding between the rice straw fiber and polymer. The thickness swelling and water absorption values decrease with increasing the EB irradiation dose with presence of coupling agents in the composite.

Synthesis of polyetherimide/silica hybrid membranes by the sol–gel process: influence of the reaction conditions on the membrane properties

Hybrid polyetherimide (PEI)–silica membranes were synthesized. The aim was to obtain improved materials for gas separation media. The inorganic material was prepared via the sol–gel method through the hydrolysis of tetraethoxysilane (TEOS). The influence of the reaction conditions on the final membrane morphology and properties were studied. Scanning electron microscopy (SEM), energy-dispersive X-ray analysis (SEM–EDX), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the PEI and PEI–silica composite membranes. The evolution of TEOS hydrolysis and the condensation processes were verified by FTIR studies. The silica–polymer interaction was also analyzed. The SEM micrographs showed how the membranes distinct morphologies depended upon synthesis parameters and preparation techniques (presence of coupling agent, TEOS polymerization in situ or not, silica content and membranes redissolution). The permeation rates of CO2, CH4, O2, N2, and H2 through the pure polymer and hybrid membranes were measured and showed an increase of gas permeability for hybrid membranes but, the CO2/CH4 and O2/N2 selectivities decreased compared to PEI membranes.

Highly Filled Polypropylene Rubber Wood Flour Composites

In this research, polypropylene composites filled with Hevea Brasilliensis wood flour at filler content up to 60 wt% were prepared and investigated in order to determine the effects of polymer melt flow rate (MFR), number of reprocessing times, filler size, and filler content on thermal and mechanical properties. The results reveal that the composites of polypropylene with higher melt flow rate (lower viscosity) provided greater values of flexural and tensile properties. The study additionally exhibits the recyclability potential without losing mechanical properties. Furthermore, both flexural and tensile modulus increased, while both flexural and tensile strength decreased with increasing wood flour contents. In addition, the average particle size of wood flour that was suitable for improving the mechanical properties was approximately 200-300 μm. In the last section of the research, the effects of maleic anhydride grafted polypropylene (MAPP) coupling agent were investigated. It is worth noting that, the flexural strength and tensile strength of highly filled composites with MAPP at 5 wt% (based on wood flour) were approximately 110% and 87% higher than those of the composites without MAPP, respectively. In the presence of coupling agent, the enhancement of interfacial adhesion was analyzed using scanning electron microscope (SEM).

Thermal and thermo‐oxidative degradation study of a model LDPE/EVA based TPE system: Effect of nano silica and electron beam irradiation

AbstractThe effect of nano‐silica on the thermal degradation behavior of Low density polyethylene‐poly(ethylene‐ co‐vinyl acetate) (LDPE‐EVA) based thermoplastic elastomeric (TPE) system was monitored using thermo gravimetric analysis (TGA) in nitrogen and oxygen atmospheres (air), respectively. The pristine nano silica was melt‐blended with the LDPE‐EVA system at different loadings by varying the sequence of addition. In one of the compositions, coupling agent (Si69) was used. In nitrogen, thermal stability of such systems remained unchanged. However, in oxygen atmosphere, the TGA thermograms reflected a dramatic change. A two staged degradation was observed for all the samples. The enhancement in thermal stability particularly upto the low conversion levels was interpreted in terms of the barrier effect of silica particles on the O2 flow into the sample. The activation energies of degradation up to lower range of conversions were determined by nonisothermal and isothermal kinetic analyses. These were found to register a similar trend for various systems studied. Upon electron beam irradiation of such filled LDPE/EVA systems at controlled doses (20 and 40 kGy), the thermal stabilities were enhanced marginally. Overall, the thermal stabilities of the TPE nanocomposites are the function of sequence and extent of nano silica addition, presence of coupling agent and extent of irradiation. POLYM. COMPOS., 31:1387–1397, 2010. © 2009 Society of Plastics Engineers

Enhancement of interfacial properties of basalt fiber reinforced nylon 6 matrix composites with silane coupling agents

In this work solution surface treatment was applied for producing basalt fiber reinforced PA6 matrix composites. Beyond scanning electron microscopy, static and dynamic mechanical tests, dynamic mechanical analysis of composites was used for qualifying the interfacial adhesion in a wide temperature range. The loss factor peak height of loss factor is particularly important, because it is in close relationship with the mobility of polymer molecular chain segments and side groups, hence it correlates with the number and strength of primary or secondary bondings established between the matrix and the basalt fibers. It was proven, that the interfacial adhesion between basalt fibers and polyamide can be largely improved by the application of silane coupling agents in the entire usage temperature range of composites. The presence of coupling agents on the surface of basalt fibers was proven by Fourier transform infrared spectroscopy. The best results were obtained by 3-glycidoxypropyltrimethoxysilane coupling agent.

Mechanical Properties of PP Composites Reinforced with BCTMP Aspen Fiber

In this work we investigated the effect of incorporating wood fibers (bleached chemi-thermo-mechanical pulp of aspen, BCTMP) on the properties of a hybrid composite material made from maleated polypropylene (MAPP) and Nanoclay (NC) or not. The effects of morphological structure of polypropylene (PP) and the molecular weight (Mw) and maleic anhydride graft level (MA%) of MAPP were also performed to evaluate the improvements of each independent factor (MAPP, Dicumyl peroxide-DCP and NC). In our case, the size of wood fiber had little effect on the impact and tensile strength. High Mw and low MA% MAPP contributes homo-PP hybrids with better performance, either impact or tensile. In addition, wood fiber gives the hybrids, based on both homo-polypropylene (homo-PP) and co-polypropylene (co-PP), without the presence of coupling agent, similar behaviors of impact and tensile strengths. However, the impact and tensile strength of the hybrids mentioned above are improved in the presence of coupling agent. NC weakens the impact strength of composites with/without the reinforcement of wood fiber, coupling agent, and DCP. It shows different behaviors of tensile with improvement of tensile for hybrids with wood fiber, coupling agent, and DCP but impartation for nanocomposites without additives. Moreover, the behavior of tensile is in concordance to the changes of elongation as well as toughness. Furthermore, DCP leads to negative effects on the impact and tensile, as well as toughness of the hybrids when fiber is present, but exhibits better resistance deformation extension which is in concordance with the increase of modulus. In addition, there is a little increase in plasticity.

Effects of rice husk (RH) particle size, glass fiber (GF) length, RH/GF ratio, and addition of coupling agent on the mechanical and physical properties of polypropylene‐RH‐GF hybrid composites

AbstractPolypropylene (PP) hybrid composites based on rice husk (RH) with different particle size and glass fiber (GF) with different length were prepared. The composites were subjected to mechanical and water immersion tests. From the results obtained, it was found that the mechanical properties of the hybrid composites were strongly dependent on the size of RH particle and length of GF. It could be further enhanced with the presence of coupling agent. In this study, two types of coupling agents, i.e., Epolene E‐43 (E‐43) and 3‐(trimethoxysilyl)‐propylmethacrylate (TPM), were employed. In general, E‐43 imparted significant improvement in the mechanical properties. From the water immersion results, it was found that the hydrophobicity of the composites was increased with the presence of coupling agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Influence of interfacial adhesion on the structural and mechanical behavior of PP‐banana/glass hybrid composites

AbstractHybrid composites of polypropylene (PP), reinforced with short banana and glass fibers were fabricated using Haake torque rheocord followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both fibers into PP matrix resulted in increase of tensile strength, flexural strength, and impact strength upto 30 wt% with an optimum strength observed at 2 wt% MAPP treated 15 wt% banana and 15 wt% glass fiber. The rate of water absorption for the hybrid composites was decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has been analyzed to investigate the interfacial properties. An increase in storage modulus (E′) of the treated‐composite indicates higher stiffness. The loss tangent (tan δ) spectra confirms a strong influence of fiber loading and coupling agent concentration on the α and β relaxation process of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out through differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA), indicated an increase in the crystallization temperature and thermal stability of PP with the incorporation of MAPP‐treated banana and glass fiber. POLYM. COMPOS., 31:1247–1257, 2010. © 2009 Society of Plastics Engineers

Synthesis, ex Vivo and in Vitro Hydrolysis Study of an Indoline Derivative Designed as an Anti-Inflammatory with Reduced Gastric Ulceration Properties

The compound 1-(2,6-dichlorophenyl)indolin-2-one (1), planned as a pro-drug of diclofenac (2), was easily synthesized in 94% yield by an intramolecular reaction in the presence of coupling agent (i.e., EDC). Compound 1 showed anti-inflammatory and analgesic activity without gastro-ulcerogenic effects. The chemical and enzymatic hydrolysis profile of the lactam derivative 1 does not indicate conversion to diclofenac (2). This compound is a new non-ulcerogenic prototype for treatment of chronic inflammatory diseases.

Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.

Mechanical properties of teak wood flour‐reinforced HDPE composites

AbstractMechanical properties such as tensile and impact strength behavior of teak wood flour (TWF)‐filled high‐density polyethylene (HDPE) composites were evaluated at 0–0.32 volume fraction (Φf) of TWF. Tensile modulus and strength initially increased up to Φf = 0.09, whereas a decrease is observed with further increase in the Φf. Elongation‐at‐break and Izod impact strength decreased significantly with increase in the Φf. The crystallinity of HDPE also decreased with increase in the TWF concentration. The initial increase in the tensile modulus and strength was attributed to the mechanical restraint, whereas decrease in the tensile properties at Φf > 0.09 was due to the predominant effect of decrease in the crystallinity of HDPE. The mechanical restraint decreased the elongation and Izod impact strength. In the presence of coupling agent, maleic anhydride‐grafted HDPE (HDPE‐g‐MAH), the tensile modulus and strength enhanced significantly because of enhanced interphase adhesion. However, the elongation and Izod impact strength decreased because of enhanced mechanical restraint on account of increased phase interactions. Scanning electron microscopy showed a degree of better dispersion of TWF particles because of enhanced phase adhesion in the presence of HDPE‐g‐MAH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Mechanical behavior of agro‐residue‐reinforced polypropylene composites

AbstractIn this research, fully environment‐friendly, sustainable and biodegradable composites were fabricated, using wheat straw and rice husk as reinforcements for thermoplastics, as an alternative to wood fibers. Mechanical properties including tensile, flexural, and impact strength properties were examined as a function of the amount of fiber and coupling agent used. In the sample preparation, three levels of fiber loading (30, 40, and 50 wt %) and two levels of coupling agent content (0 and 2 wt %) were used. As the percentage of fiber loading increased, flexural and tensile properties increased significantly. Notched Izod results showed a decrease in strength as the percentage of fiber increases. With addition of 50% fiber, the impact strengths decreased to 16.3, 14.4, and 16.4 J/m respectively, for wheat straw‐, rice husk‐, and poplar‐filled composites. In general, presence of coupling agent had a great effect on the mechanical strength properties. Wheat straw‐ and rice husk‐filled composites showed an increase in the tensile and flexural properties with the incorporation of the coupling agent. From these results, we can conclude that wheat straw and rice husk fibers can be potentially suitable raw materials for manufacturing biocomposite products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009