Types Of Coupling Agents Research Articles

Interfacial compatibility of wood flour/polypropylene composites by stress relaxation method

AbstractTo investigate the interfacial compatibility of wood flour/polypropylene (PP) composite, compressive stress relaxation curves at different temperatures (26, 40, and 60°C) were determined at various wood contents (0, 20, 30, 40, 50, 60, and 70%) without coupling agent and further determined at wood contents of 50 and 60% by using maleic anhydride grafted polypropylene (MAPP) and silane as coupling agents. The apparent activation energy (▵E) was also calculated according to the Eyring's absolute rate reaction theory. The results showed that the stress relaxed faster at higher temperatures. ▵E of wood flour/polypropylene composites without coupling agent showed the highest value at wood content of 40%, suggesting that the best interfacial compatibility between wood and PP occurred at 40% wood content. Adding coupling agents increased ▵E obviously at higher wood contents (50 and 60%). With the increasing loading level of coupling agents, ▵E increased at first and then decreased gradually or finally reached a constant level depending on the type of coupling agent. The optimal loading of coupling agent corresponding to the highest ▵E value was related to wood content and the type of coupling agent. Within the experimental conditions used in this study, the optimal loading level for MAPP was 2% at both wood contents while for silane it was 1.5% and 2% at wood content of 50 and 60%, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Comparative study of maleated polypropylene as a coupling agent for recycled low‐density polyethylene/wood flour composites

AbstractThe effects of the type of coupling agent and virgin polypropylene (PP) content on the mechanical properties and water absorption behavior of recycled low‐density polyethylene/wood flour (WF) composites were investigated. The fractured surfaces of these recycled wood/plastic composites (rWPCs) were examined to gain insight into the distribution and dispersion of WF within the polymer matrix. The results indicate that the use of 100% recycled polymer led to inferior mechanical properties and to a greater degree of moisture absorption and swelling when compared to recycled polymer–virgin PP wood/plastic composites. This could have been related to the poor melt strength and inferior processability of the recycled polymer. The extent of improvement of the mechanical properties depended not only on the virgin PP content in the matrix but also on the presence of maleic anhydride (MA) modified PP as the coupling agent. Higher concentrations of MA group were beneficial; this improvement was attributed to increased chemical bonding (ester linkages) between hydroxyl moieties in WF and anhydride moieties in the coupling agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Improving the Interfacial Adhesion of Highly Filled PP—Bagasse Composites Designed by Taguchi Method

In the present article, three different types of coupling agents at various concentrations were used to prepare high-content polypropylene/bagasse composites (65—75 wt%). Maleated polypropylene (PP-g-MA), glycidyl methacrylate-grafted polypropylene (PP-g-GMA), and thermoplastic starch (TPS) were chosen as the coupling agent to generate these wood—plastic composites in a lab-scale counter rotating twin-screw extruder. The changes in the morphological, thermal, and mechanical properties were investigated. Morphological studies showed that the fiber dispersion, wetting, and interfacial tension were improved in the presence of PP-g-MA and PP-g-GMA. Flexural properties, impact resistance, and heat deflection temperature of samples increased with incorporation of PP-g-MA and PP-g-GMA. The Cox’s model used to predict the flexural modulus exhibited a good fitting with the experimental data. With increasing coupling agent content; the thermo-mechanical properties of the composites were improved. The compatibilizing effect of PP-g-MA and PP-g-GMA is more obvious than TPS.

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

Development of Recycled Polypropylene Matrix Composites Reinforced with Fly Ash

Utilization of recycled polypropylene obtained from post-consumer products and fly ash particles, obtained as a by-product from thermal power plants, has environmental as well as economical benefits for society. A valuable addition can be made to these waste materials by converting them into composite materials. In this study, an attempt has been made to develop a composite material from RPP and fly ash in 1 : 1 weight ratio, using two types of coupling agents. A silane coupling agent (VTMO) and a maleated polypropylene (Epolene G 3003) were used as the coupling agents. The composites were characterized for their flexural properties, water absorption behavior, and thermal degradation behavior. There was a significant improvement in properties when VTMO was used as the coupling agent compared to Epolene.

Use of Sawdust in Polyethylene Composites

In this study, composites were made with wood sawdust residues and a polyolefin. Experiments were carried out in order to analyze different parameters for processing the composites. The parameters analyzed were the sawdust/polymer ratio and the type of coupling agent. The sawdust and the polymer were mixed in a single extruder in order to produce profiles. The results showed that the composites made of HDPE and sawdust had good mechanical properties, suitable for industrial applications. These results, together with the availability of the residues in the northeast of Rio Grande do Sul state, (Brazil), makes these composites a good alternative for the use of residues.

Effect of Processing Conditions and Coupling Agents on ABS/SGF Composites Properties

Different samples of acrylonitrile-butadiene-styrene (ABS)/short glass fiber (SGF) composites were prepared. Varying processing conditions such as rotor rate, fiber volume, coupling agent type and amount, and also temperature were applied in order to investigate the effect of different factors on the final properties of the composite produced. All samples were tested physically, mechanically, and morphologically to investigate the effect of varying parameters mentioned above. The best fiber concentration, coupling agent, and temperature were found in a 30 wt% SGF composite coupled with 3 wt% of fiber tricholorovinyle silane and processed at 190°C (rotor rate = 80 rpm) which showed the best properties compared with other samples.

Microstructure and dynamic mechanical analysis of extruded layered silicate PVC nanocomposites

AbstractThe nanostructure and dynamic mechanical properties of polyvinyl chloride (PVC) and the bentonite nanocomposites have been investigated. Nanocomposites with 5 wt% concentration of bentonite were prepared by melt extrusion followed by two‐roll‐milled processing. Atomic force microscopy (AFM) and wide‐angle X‐ray scattering (WAXS) were utilized to study the micro and nanostructure of the two‐roll‐milled sheets. The nanocomposites were compounded with two types of coupling agents: KZTPP® and Tamol 2001®. Optical microscopy showed that the materials remained optically transparent, i.e. they did not show evidence of nanoclay agglomeration. The WAXS patterns of PVC‐bentonite‐KZTPP nanocomposite were anisotropic, suggesting flow‐induced preferred orientation of the nanoplates. Moreover, the 001 reflection of the bentonite was shifted toward smaller angles, suggesting that the nanoplates were intercalated by the macromolecules. On the other hand, the WAXS patterns of PVC‐bentonite‐Tamol 2001 nanocomposite remained isotropic and did not show evidence of bentonite, suggesting exfoliation of the nanoplates. The nanocomposites showed an increase in glass transition temperature Tg, with the sequence Tg,PVC < Tg,KZTPP < Tg,Tamol 2001. Moreover, dynamic mechanical analysis (DMA) showed an increase in mechanical moduli and activation energy (and a decrease in the intensity of the mechanical damping Tan δ) following the same sequence. Interestingly, the improvement in mechanical moduli became more pronounced above the glass transition temperature. Copyright © 2008 John Wiley & Sons, Ltd.

Surface modification of bagasse fibers by silane coupling agents through microwave oven and its effects on physical, mechanical, and rheological properties of PP bagasse fiber composite

AbstractPolypropylene/bagasse fiber composites were prepared by compounding polypropylene (PP) with bagasse fibers as reinforcing filler. Surfaces of fibers were modified through the use of silane coupling agents (Vinyltrimethoxysilane and γ‐Glycidoxypropyltrimethoxysilane). The fiber coating was performed by mixing of silane with fibers and cured through microwave oven in presence of catalyst. It was found that modification of surface fiber will change the physical, mechanical, morphological, and rheological properties of composite. It was observed from scanning electron microscopy that fiber adhesion to matrix has been improved and so as dispersion. Addition of fibers increases the melt viscosity in unmodified fibers but reduced the melt viscosity for modified fibers and even the viscosity is lower at higher loading compared with unmodified fibers. The tensile strength and tensile modulus increased in modified fibers compared with the unmodified on the same loading, but elongation at break decreased. The effect of coupling agent on properties of filled PP depend on the content of coupling agents and optimum amount was achieve through measurement of water absorption. Two types of coupling agents were used, one as A‐171 [CH2CHSi (OCH3)3] and second one as A‐187 [CH2OCHCH2O (CH2)3Si(OCH3)], the first one shows better adhesion to the fibers and improvements in mechanical properties are much better compared with the second one. POLYM. COMPOS., 28:713–721, 2007. © 2007 Society of Plastics Engineers

Role of Maleated Coupling Agents on the Interface Adhesion of Polypropylene—Wood Composites

The main accomplishment of compounding wood-flour with thermoplastics is an increase in rigidity and specific strength. Filler—matrix interactions play a key role in the composite performance and the strength of the interface is determined by the nature of the coupling agents employed. The coupling efficiency of maleated polypropylene (PP-MAH) with varying MAH content and melt flow index in polypropylene—wood composites has been investigated. A method based on a simplified single rule of mixtures aiming to compare differences in interface adhesion in the presence of PP-MAH is proposed in terms of relaxation spectra of polypropylene—wood composites obtained by dynamic-mechanical thermal analysis (DMTA). The criterion is an attempt to determine an adhesion factor as derived from the relative mechanical damping (tan δ) of the composite as a function of the filler content and temperature. Experimental results deviate from model predictions possibly owing to assumptions of wood-flour as a rigid filler as well as neglect of an interphase volume fraction and its damping characteristics. However, good correlations of coupling efficiency and yield properties have been found for wood composites with homopolymer and copolymer matrices within a range of varying wood-flour content and type of coupling agent. Further evidences of improved matrix—filler interactions, wettability, and filler dispersion in the presence of the PP-MAH are observed by scanning electron microscopy.

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

AbstractPoly(methyl methacrylate) (PMMA)/Titanium oxide (TiO2) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO2 particles. Before polymerization, the TiO2 particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO2 via covalent bond bindings. The structure of the obtained PMMA/TiO2 composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO2 particles. Based on these facts, several factors affecting the resulting PMMA/TiO2 composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO2, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO2 composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006

Effect of Various Coupling Agents on Properties of Alumina-filled PP Composites

The effect of coupling agents on the properties of alumina-filled polypropylene (PP) has been studied. Several types of coupling agents such as silane Z-6020 ((Aminoethylaminopropyl) trimethoxysilane), 3-GPS (3-(Glycidyloxypropyl) trimethoxysilane), and titanium dioxide powder (TiO2) were employed either during compounding or before compounding i.e., at pre-treatment stage. The silane coupling agent was first diluted into ethanol in appropriate ratio and subsequently dried before compounding. In the case of titanate, the powder was directly mixed with alumina-PP compound during mixing using Brabender internal mixer. Series of mechanical tests such as tensile and flexural testing were carried out using Instron model 3366 machine in accordance to ASTM D368 and D790-92 respectively. It has been found that the tensile strength of alumina-filled PP composite has increased considerably when both types of coupling agents are added. PP filled alumina composite with titanium as coupling agent showed a greater value of tensile strength as compared to silane-treated and untreated alumina-filled PP composites. Similarly, the flexural strength recorded was higher as compared to the untreated system with silane-treated alumina-filled composites showing the most positive results of all the systems. Consequently, study on the impact properties showed that titanium has notably improved the impact resistance of alumina-filled PP composite as compared to silane-treated composite. Study on the scanning electron micrograph revealed that improved texture on the treated composite has allowed greater plastic deformation to occur with improved adhesion and interaction between filler and matrix.

On engineering of properties of wood-polypropylene composite

New materials based on wood have the advantage in the sense that their properties can be engineered so as to correspond to user demands. The properties which can be engineered are those relating both to their utilisation and machining, in particular - the tensile strength, elongation at break, modulus of elasticity and impact resistance. The research at the Faculty of Forestry and "Hipol" Chemical Industry related to the new type of wood-polypropylene composite. The content of wood filler was varied in the range between 40% and 70% mass contents of beech wood flour. After the highest tensile strength at 50% of filler content was determined, the effect of the wood filler origin was also examined at this content value. Therefore, wood flour of beech, poplar, acetylated pine and the waste MDF was used. The influence of the composition of the wood filler (beech combined with MDF, poplar and acetylated pine) in comparison with pure polypropylene matrix was also examined, as well as the effect of the type of coupling agent. Hopefully, the results obtained in this study might serve as the initial data for production of easily machined high-strength composites.

Flour rice husk as filler in block copolymer polypropylene: Effect of different coupling agents

AbstractFlour rice husk (FRH) was employed as a filler in block copolymer polypropylene (PPB) in order to prepare polymer‐based reinforced composites. Four coupling agents were selected to modify the surface of the rice husk in the composite materials, including two types of functionalized polymers [PP homopolymer grafted with maleic anhydride (MA‐PP) and an elastomer styrene–ethylene–butadiene–styrene triblock copolymer grafted with MA (MA‐SEBS)] and two bifunctional organometallic coupling agents (silane and titanate with linear low‐density polyethylene as a carrier). The influence of each type of coupling agent on the interfacial bonding strength was studied by dynamic mechanical analysis, scanning electronic microscopy, and rheological tests. The results showed that strong interactions were formed between the coupling agents and the filler surface. The addition of a coupling agent with an elastomeric carrier (MA‐SEBS) increased the loss tangent and reduced the storage modulus of the composite. A similar but less intense effect was observed for the titanate coupling agent. However, an antagonistic performance was obtained when MA‐PP and silane were employed as coupling agents. In addition, when the percentage of MA‐SEBS was increased, the impact properties of FRH/PPB blends were improved and the strength was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1823–1831, 2006

The effect of fiber surface treatments on the tensile and water sorption properties of polypropylene–luffa fiber composites

Abstract The effects of coupling agents on the mechanical, morphological, and water sorption properties of luffa fiber (LF)/polypropylene(PP) composites were studied. In order to enhance the interfacial interactions between the PP matrix and the luffa fiber, three different types of coupling agents, (3-aminopropyl)-triethoxysilane (AS), 3-(trimethoxysilyl)-1-propanethiol (MS), and maleic anhydride grafted polypropylene (MAPP) were used. The PP composites containing 2–15 wt% of LF were prepared in a torque rheometer. The tensile properties of the untreated and treated composites were determined as a function of filler loading. Tensile strength and Young's modulus increased with employment of the coupling agents accompanied by a decrease in water absorption with treatment due to the better adhesion between the fiber and the matrix. The maximum improvement in the mechanical properties was obtained for the MS treated LF composites. The interfacial interactions improved the filler compatibility, mechanical properties, and water resistance of composites. The improvement in the interfacial interaction was also confirmed by the Pukanszky model. Good agreement was obtained between experimental data and the model prediction. Morphological studies demonstrated that better adhesion between the fiber and the matrix was achieved especially for the MS and AS treated LF composites. Atomic force microscope (AFM) studies also showed that the surface roughness of LFs decreased with the employment of silane-coupling agents.

Network density control in epoxy–silica hybrids by selective silane functionalization of precursors

AbstractFollowing previous work on the compatibilization of organic–inorganic hybrids through coupling reactions with the precursor components, the present study evaluates the relative efficiency of different types of coupling agents on the morphology and properties of epoxy–silica hybrids. In particular, this investigation compares the effects of introducing trialkoxysilane functional groups at the chain end (using amine‐ and mercapto‐silanes) with similar types grafted in the middle of the chain of the constituent resin (using an isocyanate silane). The use of coupling agents with a basic character (amine silane type) brings about the formation of denser networks in both constituent phases of the resulting epoxy–silica hybrid, which is manifest through a large increase in the Tg and a more extensive suppression of the molecular relaxations within the glass transition regions. Increasing the number of alkoxysilane functional groups at the chain end, with the use of a bis‐aminosilane, has a relatively minor effect on the morphology and dynamic mechanical spectra of the resulting epoxy–silica hybrids. It was also found that while the incorporation of small amounts of a high molecular weight epoxy resin causes considerable plasticization of the organic phase, much larger amounts of organic (aliphatic) co‐agent within the siloxane phase are required to deteriorate those properties that are related to the inorganic character of the hybrid material. © 2005 Wiley Periodicals, Inc. Adv Polym Techn 24:91–102, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20033

Wood‐fiber/high‐density‐polyethylene composites: Coupling agent performance

AbstractThe coupling efficiency of seven coupling agents in wood–polymer composites (WPC) was investigated in this study. The improvement on the interfacial bonding strength, flexural modulus, and other mechanical properties of the resultant wood fiber/high‐density polyethylene (HDPE) composites was mainly related to the coupling agent type, function groups, molecular weight, concentration, and chain structure. As a coupling agent, maleated polyethylene (MAPE) had a better performance in WPC than oxidized polyethylene (OPE) and pure polyethylene (PPE) because of its stronger interfacial bonding. A combination of the acid number, molecular weight, and concentration of coupling agents had a significant effect on the interfacial bonding in WPC. The coupling agents with a high molecular weight, moderate acid number, and low concentration level were preferred to improve interfacial adhesion in WPC. The backbone structure of coupling agents also affected the interfacial bonding strength. Compared with the untreated composites, modified composites improved the interfacial bonding strength by 140% on maximum and the flexural storage modulus by 29%. According to the statistical analysis, 226D and 100D were the best of the seven coupling agents. The coupling agent performance was illustrated with the brush, switch, and amorphous structures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 93–102, 2005

Maleated wood-fiber/high-density-polyethylene composites: Coupling mechanisms and interfacial characterization

Chemical coupling of maleated polyethylene (MAPE) copolymers at the interface in wood-fiber/high-density-polyethylene (HDPE) composites was investigated in this study. FTIR and ESCA analyses presented the evidence of a chemical bridge between the wood fiber and polymeric matrix through esterification. The feature peak of esterification occurred in the range between 1800 and 1650 cm−1 at FTIR spectra. Succinic and half succinic esters were the two primary covalent bonding products to cross-link the wood fiber and thermoplastic matrix. Maleated composites had a remarkable shift on most O1s and C1s spectra in respect to the wood, HDPE, and untreated composites. The binding energy of maleated composites at C1s and O1s spectra was around 282 eV and 530 eV, respectively. The mass concentration of chemical components at the interface was related to the coupling agent type, structure, and concentration. According to the FTIR and ESCA analyses, the coupling mechanisms of MAPEs were proposed. The interfacial morphology in wood-fiber/HDPE composites was illustrated with the pinwheel models based on SEM observations.

Compatibilization of a polyolefin blend through covalent and ionic coupling of grafted polypropylene and polyethylene. I. Rheological, thermal, and mechanical properties

AbstractA polypropylene/high‐density polyethylene blend containing 70 wt % polypropylene was prepared and compatibilized via the addition of maleic anhydride grafted polypropylene and polyethylene. The functionalized polymer chains were coupled with two types of coupling agents. Dodecane diamine formed covalent bonds with the maleic anhydride, whereas two metallic salts, zinc acetate and sodium hydrogenocarbonate, formed ionic interactions with the carboxylic functions produced by the hydration of the anhydride cycle. The coupling of the grafted polyolefin chains was successfully realized by a single operation in a twin‐screw extruder. The coupling agents were efficient in improving the elongation at break and impact properties of the studied blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 312–320, 2005

Reactive blends of polyamide 6 with polyester elastomer using coupling agents

AbstractIn situ compatibilized melt blends of polyamide 6 (PA‐6) with polyester elastomer (PEL) were prepared in a corotating twin‐screw extruder using two types of coupling agent (CA): diglycidyl ether of bisphenol A (DGEBA) and 1,4‐phenylene bis(2‐oxazoline) (PBO). The notched impact strength of PA‐6 and PA‐6/PEL blends increased with the addition of coupling agent, especially DGEBA, and the maximum impact toughening of the blend was obtained with 0.6 mol % DGEBA, the composition of minimum domain size observed from SEM. Viscosities of the untreated blends increased over those of the base resins at low frequencies. Viscosities of both the base resins and the blends increased with the addition of CA, and the effect was much more pronounced with DGEBA, especially for PA‐6 and PA‐6–rich blends. The crystallization temperature (Tc) of PEL increased over 10°C, whereas the Tc of PA‐6 decreased by 2–3°C in the blends. With the addition of coupling agents, the crystallization melting temperature (Tm) and Tc of PA‐6 decreased by up to 5°C with DGEBA, implying that the crystallization of PA‐6 is disturbed by the in situ formed PA‐6–CA–PEL or PA‐6–CA–PA‐6 type copolymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3966–3973, 2004