Addition Of Coupling Agent Research Articles

Refratários contendo carbono: propriedades, características e variáveis em sua composição

Por seu singular conjunto de propriedades e características, os refratários contendo carbono têm sido fundamentais para que a indústria siderúrgica alcance seus atuais níveis de produtividade. Apesar disso, investir no desenvolvimento desses materiais continua a ser necessário, sobretudo devido à crescente pressão para que o setor siderúrgico torne seus processos mais seguros e sustentáveis, objetivos esses que dependem diretamente do desempenho dos refratários utilizados ao longo da cadeia produtiva do ferro e do aço. Assim, com o intuito de indicar oportunidades de desenvolvimento ainda não exploradas, bem como de examinar as linhas de pesquisa que têm obtido êxito em aumentar a eficiência dos refratários contendo carbono, este trabalho faz uma ampla revisão dos possíveis constituintes destes materiais, tais como ligantes, fontes de carbono e aditivos diversos. Das inovações recentemente divulgadas, analisa-se o uso de adições combinadas de agentes antioxidantes e TiO2 para promover o desenvolvimento de fases com morfologias especiais (como whiskers), e a descoberta de aditivos que possibilitam a grafitização do carbono produzido pelas resinas termofixas. Este último avanço é particularmente significativo, pois proporciona às resinas uma capacidade antes exclusiva do piche de alcatrão, ligante que vem sendo evitado pelas condições insalubres que causa tanto no ambiente da indústria siderúrgica como refratarista. Já entre as possibilidades de inovação cogitadas, destaca-se a adição de agentes de acoplagem aos refratários resinados com o objetivo de otimizar, sobretudo, a sua processabilidade. Tal avanço seria especialmente desejável para os concretos refratários resinados, materiais que atualmente possuem aplicações limitadas, mas que atraem grande interesse por suas diversas vantagens em relação aos produtos pré-conformados, o que os leva a ser um importante foco para novos desenvolvimentos.

Novel cork–polymer composites reinforced with short natural coconut fibres: Effect of fibre loading and coupling agent addition

Composites from high density polyethylene filled with cork powder and coconut short fibres, in two different ratios, were prepared in a twin-screw extruder followed by compression moulding process. The main motivation of this work was to improve the mechanical performance without compromising the use of high weight percentage of natural component used in the preparation of cork-based composites. The morphology of the hybrid composites were more homogeneous in the presence of the coupling agent (CA) displaying enhanced fibre–matrix adhesion. Moreover, the use of CA based on maleic anhydride promotes a mechanical reinforcement effect on the tensile properties , including the elongation at break . The addition of coconut fibre resulted on an increase of 27% in elastic modulus and 47% in the tensile strength when compared with the unreinforced cork-based (50–50) wt.% composite. This work clearly shows that the addition of 10 wt.% of short-coconut fibres, randomly distributed, can be effectively used as reinforcing strategy of cork-based composite materials, preferably in the presence of 2 wt.% of CA.

Improving fibre/matrix interface through nanoparticles

strength controls several mechanical properties of composite materials, in particular the matrix-dominated ultimate parameters. In the last thirty years an impressive number of experimental and modelling efforts have been focused on the understanding of fibre/matrix interfacial bond with the aim to improve it. Over the years, two main strategies emerged for polymer composites: i) the development of specific fibre sizings/coatings/treatments and/or ii) the addition of coupling agents to the matrix resin. In the recent years new strategies came to light: in fact, the availability of various types of nanoparticles offered the possibility to tailor the fibre/matrix interactions at a nanoscale level. In particular, some recent investigations proved that nanoparticles homogeneously dispersed in a polymer matrix can play a beneficial role on the fibre/matrix interfacial adhesion in several types of structural composites. For example, the introduction of organo-modified clays in an epoxy matrix led to the formation of a stronger interface with E-glass fibres, with an increase of the interfacial shear strength of about 30% for a filler content of 5 wt% (DOI: 10.1177/ 0021998311420311). Concurrently, the evaluation of the fibre/matrix contact angle revealed an improved wettability when organo-modified clays were added, and a simultaneous enhancement of the fracture toughness of the resin matrix. This approach could be also adopted to add specific functional properties to composite materials, such as damage controlling capabilities (DOI: 10.1016/j.compositesa.2012.03.019). Another approach relies on the possibility to confine nanoparticle in the interfacial region, with the advantage of localizing their presence in the area where stress transfer takes place, thus reducing the overall quantity of nanoparticle required. As an example, a sizing containing single or multi-walled carbon nanotubes has been used for coating glass fibres (DOI: 10.1016/j.compscitech.2007.10.009). Two simultaneous results have been reached, to ‘heal’ surface flaws and to enhance interfacial adhesion in a polypropylene matrix, indicating nanotube related interfacial toughening mechanisms. An amazing amount of research has gone, and still goes, into the understanding of the properties of nanoscale particles and their usage to improve engineering materials. Development of polymer composites can surely benefit from this research, including the ‘old issue’ of fibre/matrix interface.

Transparent polyimide nanocomposites with improved moisture barrier using graphene

A facile technique was developed to improve the water barrier properties of transparent polyimide (PI) films. Transparent and organo-soluble PI films were synthesized from an alicyclic tetracarboxylic dianhydride (bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride) and an aromatic diamine (3,4′-oxydianiline) in a co-solvent of dimethylacetamide (DMAc) and γ-butyrolactone via a one-step process. Thermally reduced graphene (RG) was then blended with the PI in DMAc solution to fabricate PI/RG nanocomposite films without the addition of coupling agent. With the incorporation of only 0.1 wt% highly exfoliated RG in the PI matrix, the resultant PI/RG-0.1 nanocomposite exhibited a superior barrier to moisture and retained high transmittance in the visible light region. The surface of PI/RG was more hydrophobic than that of pure PI and simultaneously the water vapor transmission rate was significantly reduced to 13 g m−2 day−1 for the PI/RG-0.1 nanocomposite compared to 181 g m−2 day−1 for pure PI. Notably, the PI/RG-0.1 nanocomposite also exhibited favorable thermal stability with a lower coefficient of thermal expansion and a higher thermal degradation temperature compared to pure PI. The easy processing of PI solution and RG nanosheets, the good orientation of RG in PI and the excellent barrier and thermal properties of PI/RG make the transparent PI nanocomposite films potential substrate materials in flexible electronic applications.

Preparation of PDMS-ormosil and its application in miniemulsion polymerization

With the assistance of ultrasound, octamethylcyclotetrasiloxane (D4) and slight silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) were sufficiently mixed with silica sol, and the in situ ring-opening polymerization of D4 on the surface of silica nanoparticles, catalyzed by dodecylbenzene sulfonic acid (DBSA), was enhanced as well. Thus, polydimethylsiloxane (PDMS)-modified silica (PDMS-ormosil) mixture was obtained. A slight addition of silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) could significantly enhance the modified efficiency. The PDMS-ormosil mixtures were directly dispersed in the mixed monomer methyl methacrylate and butyl methacrylate. Then, miniemulsion polymerizations of acrylate monomers containing PDMS-ormosils were carried out, with free PDMS as hydrophobe and neutralized DBSA as emulsifier, both preexisted in the PDMS-ormosil mixture. Thus, the troubles of separation, purification, and redispersion in the traditional techniques can be omitted. Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscope, scanning electron microscope, and water contact angle tests were utilized to demonstrate that nanocomposite particles with a core–shell structure were synthesized; when the silica content was 3 wt% of the monomers, the average particle size was 97 nm, and the generated PDMS improved the hydrophobicity of the nanocomposite latex.

Characterization, Physical and Mechanical Properties of Polypropylene/Wood-Flour Composites

Wood polymer composites (WPCs) were made with pine and polypropylene matrix (PP). Samples of WPCs were processed through melt compounding and hot-press moulding with different formulations of wood flour content and addition of coupling agent. This study focuses on the improvement of the mechanical properties of WPCs through the addition of compatibilizers. Generally fiber/matrix bonding or a strong interaction is required to ensure an appropriate transfer of stresses and satisfactorily physical properties. The effect of wood content and coupling agent like Maleic anhydride grafted polypropylene (MAPP) on the thermal behavior was monitored by DSC, water uptake and thickness of swelling during 2 months. The results exhibited increase of these two physical properties with wood flour content and coupling agent. In the thermal behavior, wood plays the role of nucleating agent. During the cooling step, the crystallization begins earlier than in pure PP and the percent of crystallization increase with wood amount. The effects of the reinforcements on the mechanical properties of the composites as well as the effect of compatibilization on the composite properties were highlighted. The mechanical study revealed the positive effect of coupling agent MAPP on interfacial bonding permitting better stress transfer from matrix to fiber.

Natural Fibres as Reinforcement Strategy on Cork-Polymer Composites

Cork powder, the most important sub-product of cork processing, combined with thermoplastic matrixes like, high density polyethylene (HDPE), offer a new class of cork-polymer composite (CPC) materials with high added-value. Therefore, reinforcing strategies must be considered to increase the mechanical performance, especially when high content of cork powder is added to the formulation. Coconut fibres have several advantages, such as, low density, renewable source, low cost and biodegradability. The use of these fibres on the reinforcement of CPC materials will not only contribute to improve the mechanical performance but also for increasing the amount of natural component present on the final composition. The main goal of this work was to prepare HDPE/cork (50-50 wt.%) composites reinforced with discontinuous coconut fibres (5 and 10 wt.%) with and without the addition of coupling agent (2 wt.%) by extrusion. The developed reinforced cork based composites were characterized regarding its morphology and mechanical performance. Optical micrographs have shown a homogeneous distribution of the fibres. The coupling agent effect on CPC performance was also investigated. The tensile strength and tensile modulus of the reinforced composites were significantly improved with the addition of coupling agent. The use of 10 wt.% of coconut fibres in the presence of coupling agent promote an increase on maximum tensile strength of around 41 % comparing with the HDPE/cork (50-50 wt.%) composites. Scanning electron microscopy (SEM) micrographs of the tensile fractured specimens confirmed that the use of coupling agent promoted the interfacial adhesion between the fibres and the thermoplastic matrix. Since, like cork powder, coconut fibres have good thermal and acoustic properties, we consider that the novel reinforced CPC herein described have high potential to be used in building and construction systems and other structural 3D applications.

Rheological and Kinetic Characterization of UV Photopolymerizable Formulations as a Function of the Boehmite Nanoparticle Content

Several innovative photopolymerizable siloxane-modified acrylic formulations were characterized, both in presence or absence of organically Boehmite (OMB) nanoparticles, in order to assess their rheological and kinetic behavior. The experimental formulations were mainly intended for the surface protection of porous stones or wood elements. The importance of the experimental investigation lies in the specific requirements necessary for the proposed applications, i.e. the innovative UV coatings developed should possess adequate viscosity, photopolymerization reaction rate and time. The kinetics of the radical photopolymerization mechanism, induced by UV radiations, was studied by calorimetric analysis and FTIR spectroscopy as function of the mixtures composition and test conditions (air or nitrogen atmosphere). The addition of a silane coupling agent or a high molecular weight polysiloxane monomer to the acrylic resin was found to reduce the heat of reaction. On the other hand, the presence of Boehmite nanoparticles in the UV photopolymerizable formulations does not seem to modify the reactivity of the siloxane-modified acrylic formulations. The effect of the presence of oxygen on the kinetic reaction was also investigated and correlated to the composition of the systems. Finally, the viscosity of the formulations was studied at ambient temperature with a parallel plates rheomether as a function of composition and shear rate. The viscosity curves were also fitted according to theoretical models as function of shear rate and composition, obtaining a good agreement between experimental data and model predictions.

Epoxy monoacrylate synthesis and photopolymerization in a thiol-ene/cationic hybrid system

Thiol-ene/cationic hybrid materials were designed and synthesized to address the challenges of the low glass transition temperature (Tg) and low storage modulus of thiol-ene materials. Two bifunctional monomers with methacrylate and epoxy groups were synthesized via a semiesterification reaction and characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The resultant bifunctional monomers were used as coupling agents in two thiol-ene/cationic hybrid systems that comprised tetrafunctional thiol, trifunctional/ difunctional ene, and difunctional epoxycyclohexyl monomers. Real-time Fourier transform infrared spectroscopy, which was applied to monitor the conversion of the functional groups, indicated that both thiol and alkene conversion improved upon the addition of the coupling agent while allyl conversion decreased slightly after irradiation for 120 s. Dynamic mechanical analysis indicated that the storage modulus and Tg values of the thiol-ene/cationic hybrid materials with coupling agents were higher than those of thiol-ene materials in both rigid and flexible systems, respectively.

에폭시/마이크로실리카/나노실리카 혼합 콤포지트의 열적, 전기적 특성

The epoxy/micro-and nano-mixed silica composites(EMNC) systems were prepared and the AC insulation breakdown strength was evaluated. Glass transition temperature (Tg) and crosslink density were also measured by dynamic mechanical analyzer(DMA) in order to correlate them with the electrical and mechanical properties, and the effect of silane coupling agent on the electrical properties was also studied. Electrical properties and crosslink density of epoxy/micro-silica composite were noticeably improved by addition of nano-silica and silane coupling agent, and the highest breakdown strength was obtained by addition of 0.5~5 phr of nano-silica and 2.5 phr of silane coupling agent, and the highest tensile and flexural strength were obtained by addition of 2.5 phr of nano-silica.

Effects of Coupling Agents on the Mechanical Properties of the Calcium Carbonate-Plastic Composite Packaging Materials

Mechanical properties of the calcium-plastic composite have a great influence on the containers. The main factors affecting the mechanical properties are the process and material formulations. This paper mainly describes its impact of the addition of coupling agent. Under the usage of analysis of variance on single factor experiment, the mechanical properties of the calcium carbonate-plastic composite with three different coupling agents (silane, titanate and aluminate) were studied in the same test conditions. The results show that: The type and quantity of the coupling agent effect a lot on the mechanical properties of the composite. The silane coupling agent is the most suitable for calcium carbonate-plastic composite packaging materials, and the compatibility of calcium carbonate and polyethylene can be improved. When the silane coupling agent was at a 2.25 wt. % concentration, the tensile and flexural strength were improved obviously, especially the tensile strength increased by 23.24%, but the impact strength improved slightly.

Polymer Adhesion to Geopolymer via Silane Coupling Agent Additives

Silane coupling agents were successfully incorporated into alkali‐activated aluminosilicate geopolymers (GP) through simple mixing into the precursor liquid. This allowed for synthesis of thick coatings with meaningful long‐term shear and tensile adhesion to organic polymer substrates. Adhesion of GP to high‐impact polystyrene sheets and extruded polystyrene foam was quantitatively evaluated. GP drying shrinkage and coating‐substrate thermal expansion mismatch were identified as the major obstacles to adhesion, and these were mitigated by the easy yielding of polystyrene foam. The coupling agent‐modified GP experienced decreased splitting strength, but Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy were used to verify that the coupling agent addition did not inhibit geopolymerization.

Effect of coupling agents on thermal, flow, and adhesion properties of epoxy/silica compounds for capillary underfill applications

Abstract In this study, the different silane coupling agents were added to epoxy/silica systems. The effects of the type of silane coupling agent in the epoxy/silica compounds on the thermal, flow and adhesion properties were investigated. The curing behavior was examined by differential scanning calorimetry (DSC), and the flow properties of the epoxy compounds were evaluated from penetration rate measurements. The adhesion strength as a mechanical property was determined by die shear strength testing. The silane coupling agent type had a significant effect on the thermal, flow and adhesion properties. The coefficients of thermal expansion (CTE) and adhesion of the DGEBF epoxy/SiO 2 systems could be enhanced by the addition of silane coupling agents. In addition, the penetration rate was increased by the addition of a coupling agent except for the CA-A coupling agent. This was interpreted in terms of the reactive functional groups and dispersion forces resulting in coupling agents on the interfaces between the DGEBF epoxy resin and silica.

Effects of hot water treatment of raw bark, coupling agent, and lubricants on properties of bark/HDPE composites

Hot water treated and untreated black spruce bark (BSB) and trembling aspen bark (TAB) fibers were combined with high density polyethylene (HDPE) to produce bark thermoplastic composites by extrusion. Bark fibers of three size categories (fine, medium, and coarse) were used at contents of 50% and 60% based on oven dry weight. The effects of hot water treatment of raw bark and the addition of coupling agent (MAPE) and lubricants (OP-100, talc) on the flexural and tensile properties of bark/HDPE composites were investigated. Results showed a significant impact of hot water treatment on tensile properties of composites made with BSB and on tensile and flexural strength of composites made with TAB. The addition of coupling agent and lubricants significantly improved the flexural and tensile strength properties of bark/HDPE composites but reduced toughness and strain.

Mechanical Properties of Recycled Polypropylene/SBR Rubber Crumbs Blends Reinforced by Birch Wood Flour

In this work, recycled polypropylene (PP) and regenerated styrene butadiene rubber (SBR) from used tyres rubber crumbs were combined to produce polymeric blends. The compounds were prepared via twin-screw extrusion to measure their mechanical behaviour for different SBR compositions (0 to 40%). Also, the addition of birch flour (0 to 40%) and coupling agent (0 to 5 phr) content were studied. The results showed that tensile strength and modulus of the blends were substantially improved after incorporation of wood flour. The torsion modulus also increased with birch content. However, the tensile strain at break of PP/birch wood composites decreased with both wood and coupling agent contents, showing a decrease in ductility of the composites. Adding the elastomer phase did not improve the properties. The results showed that adding a coupling agent was found to be effective in improving the wood flour-PP interface, while less improvement was observed for the rubber-PP surface adhesion. The tensile strength of PP/birch composites improved by more than 60%, while the torsion and tensile moduli of the composites improved by only 10% in some cases.

Toughening of unmodified polyvinylchloride through the addition of nanoparticulate calcium carbonate and titanate coupling agent

AbstractPVC/CaCO3 polymer nanocomposites of differing compositions were produced using a two‐roll mill and compression molding. In all formulations, 0.6 phr of titanate was incorporated to assist dispersion during processing. The morphology was observed using transmission electron microscopy, and the static and dynamic mechanical and fracture properties were determined. Fracture toughness examination was performed according to strain energy release test method. The presence of nanometer‐sized CaCO3 particles led to a slight decrease in the tensile strength but improved the impact energy absorption, storage modulus, and fracture toughness. The use of titanate coupling agent softened the polymer matrix and reduced the matrix's modulus. Fracture surface examinations by scanning electron microscopy showed that the coupling agent improved particle–matrix bonding and inhibited void formation around the particles. Finite element analysis suggested that the improved particle–matrix bonding reduced the matrix's plasticity around the particles, which decreased the toughening efficiency of the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of surface modifiers and surface modification methods on properties of acrylonitrile–butadiene–styrene/poly(methyl methacrylate)/nano‐calcium carbonate composites

AbstractNano‐calcium carbonate (nano‐CaCO3) was used in this article to fill acrylonitrile–butadiene–styrene (ABS)/poly(methyl methacrylate) (PMMA), which is often used in rapid heat cycle molding process (RHCM). To achieve better adhesion between nano‐CaCO3 and ABS/PMMA, nano‐CaCO3 particles were modified by using titanate coupling agent, aluminum–titanium compound coupling agent, and stearic acid. Dry and solution methods were both utilized in the surface modification process. ABS/PMMA/nano‐CaCO3 composites were prepared in a corotating twin screw extruder. Influence of surface modifiers and surface modification methods on mechanical and flow properties of composites was analyzed. The results showed that collaborative use of aluminum–titanium compound coupling agent and stearic acid for nano‐CaCO3 surface modification is optimal in ABS/PMMA/nano‐CaCO3 composites. Coupling agent can increase the melt flow index (MFI) and tensile yield strength of ABS/PMMA/nano‐CaCO3 composites. The Izod impact strength of composites increases with the addition of titanate coupling agent up to 1 wt %, thereafter the Izod impact strength shows a decrease. The interfacial adhesion between nano‐CaCO3 and ABS/PMMA is stronger by using solution method. But the dispersion uniformity of nano‐CaCO3 modified by solution method is worse. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Isocyanate Modification of Wood Fiber in Enhancing the Performance of its Composites with High Density Polyethylene

This study is focused on the modification of wood fiber by using a reactive diisocyanate (toluene diisocyanate, TDI) linker to couple wood fiber with cetyl alcohol and the investigation of its effects on mechanical properties of wood fiber–HDPE composites. The reaction of TDI with wood fiber and then cetyl alcohol resulted in the formation of new urethane bonds assessed by FTIR analysis. Therefore, TDI ended cetyl alcohol was used as a coupling agent in the preparation of wood fiber/ HDPE composite. The outcomes showed that the addition of such coupling agents resulted in greater reinforcement of composites, as indicated by the improvement in mechanical properties. Tensile strength of prepared composites increased by almost 64%, whereas 47% increase in flexural strength and 113% increase in impact properties was observed. However, the moisture absorption of the composites decreased by about 43%. All chemically treated composites showed lower moisture uptake than the untreated composites. This may be due to chemical treatment of wood fiber which reduces its hydrophilicity. These chemical treatments promote interfacial adhesion of fiber and HDPE matrix. Furthermore, scanning electron microscopy (SEM) revealed the improved morphology of the fractured surfaces of composites.

Study of erosion resistance and mechanical properties of unsaturated polyester based nano-composites

The addition of spherical and platelet shaped nano-particles in polymer composites has been shown to increase the electrical erosion resistance of insulation systems. Previous studies have mainly focused on the performance of epoxy based nano-composites and there are currently no studies evaluating the performance of ambient cured unsaturated polyester (UPR) nano-composites for their electrical erosion resistance. The present study focuses on the performance of UPR nano-composites with respect to their electrical erosion resistance as well as other mechanical and thermal properties. It was shown that the use of spherical particles showed the greatest increase in the erosion resistance of the resultant composites, however, the platelets showed the greatest increase in mechanical properties. Further, the optimum concentration of nano-particles, irrespective of particle morphology, was found to be between 0.5 and 1.5 pph with respect to erosion resistance and mechanical properties. Addition of a silane coupling agent was found to increase the properties of the resultant composites further, with respect to electrical erosion resistance and mechanical properties upto an optimum concentration. Further increase in coupling agent concentration resulted in a decrease in performance due to a decrease in the crosslinking density of the composites.

Effects of coupling agents on thermal behavior and mechanical properties of wood flour/polypropylene composites

The efficiency of two coupling agents in wood-polymer composites was investigated in this study. Thermal behavior of neat polypropylene, wood flour/polypropylene composite, maleated anhydride polypropylene-reinforced wood-polymer composite, and oxidized polypropylene-reinforced wood-polymer composite was investigated by means of differential scanning calorimetry and scanning electron microscopy in order to obtain information on the dispersion of the wood flour in the polymeric matrix, on the crystallization kinetics of polypropylene, and the macrostructure of its composites. The results confirm the expected nucleant effect of wood with and without the coupling agents used. The wide angle X-ray diffraction patterns indicated enhanced compatibility between polypropylene and wood with the addition of coupling agent. As a coupling agent, maleated anhydride polypropylene had a better performance in wood-polymer composites than polypropylene oxide and neat polypropylene because of its stronger interfacial bonding. Coupling agents help overcome the polarity disparity increase. All the results showed that with maleated anhydride polypropylene, oxidized polypropylene or without any coupling agent, wood flour acted as nucleating agent and increased the crystallization rate of polypropylene. For the composites, wood with maleated anhydride polypropylene was a more effective nucleating agent for polypropylene than wood with oxidized polypropylene. The mechanical properties were evaluated and the samples with coupling agent showed superior results like tensile and flexural properties.