Characterization and properties of activated nanosilica/polypropylene composites with coupling agents

In this work, nanosilica/polypropylene composites containing 1 wt% of silica nanoparticles were prepared by melt mixing in a Thermo Haake internal mixer. Prior compounding, nanosilica was subjected to surface activation using sodium hydroxide (NaOH) solution. The effectiveness of the activation process was evaluated by measuring the amount of hydroxyl groups ( OH) on the surface of nanosilica via titration method and supported by FTIR analysis. Two coupling agents namely 3‐aminopropyl triethoxysilane (APTES) and neopentyl (diallyl)oxy, tri(dioctyl) phosphate titanate (Lica 12) were used for surface treatment after activation process. The mechanical properties of polypropylene matrix reinforced with silica nanoparticles were determined by tensile and impact test. Hydroxyl groups on the nanosilica surface played an important role in enhancing the treatment with silane coupling agents. To increase the amount of hydroxyl groups on the nanosilica surface, the optimum concentration of NaOH is 1 mol%. Tensile strength, tensile modulus, and impact strength of nanosilica/PP composites improved with activation process. As the coupling agent is concerned, APTES coupling agent is more pronounced in enhancing the mechanical properties of the composites when compared with Lica 12 coupling agent. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of coupling agents on thermal and electrical properties of mica/epoxy composites

The influence of 3-aminopropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, and neoalkoxytric(dioctyl pyrophosphato)zirconate on thermal expansion behavior, dielectric strength, and arc resistance of mica/epoxy composites has been investigated. The addition of mica up to 30% resulted in the reduction of thermal expansion with respect to neat resin. However, the coefficient of linear thermal expansion of 30% mica treated with aminosilane was the least among the various coupling agent-coated filler/epoxy composites. Mica (30%)/epoxy composites showed the highest dielectric strength values (26 kV/mm), but the highest arc resistance was obtained in zirconate-treated mica (30%)/epoxy composite. © 1995 John Wiley & Sons, Inc.     

Effect of coupling agents on the mechanical properties of mica/epoxy and glass fiber/mica/epoxy composites

The effect of coupling agents, two silane and one zirconate, on the mechanical properties of mica/epoxy and glass fiber/mica/epoxy composites has been investigated. The results showed that tensile modulus and flexural strength and modulus values were improved by the surface treatment of the coupling agents. The property retention was also found to be better in the case of coupling agent-treated mica/epoxy samples after boiling in water for 2h. In the case of glass fiber/mica/epoxy composites, the flexural modulus and interlaminar shear strength values improved with increase in mica content, but the effect of coupling agents was not pronounced.     

偶联剂对淀粉/丁苯橡胶复合材料性能的影响

采用乳液共混法制备了淀粉/丁苯橡胶(SBR)以及间苯二酚甲醛树脂(RF)改性淀粉/SBR复合材料,考察了偶联剂对2种复合材料硫化特性、力学性能的影响,并用扫描电镜观察了其相态结构。结果表明,各种偶联剂都能在一定程度上提高淀粉/SBR复合材料的拉伸强度和撕裂强度,其中γ-氨基丙基三乙氧基硅烷(KH-550)和N-β(氨基乙基)-γ-氨丙基三甲氧基硅烷(KH-792)的增强效果最为显著;采用RF对淀粉进行改性,RF改性淀粉/SBR复合材料的力学性能较之淀粉/SBR复合材料的力学性能有了进一步提高。橡胶相与淀粉相界面结合的改善是RF改性淀粉/SBR复合材料力学性能提高的主要原因。     

Structure and properties of polyurethane/nanosilica composites

Nanosilica particles were directly introduced into polyester polyol resins through in situ polymerization and blending methods, then cured by isophorone diisocyanate (IPDI) trimers to obtain nanocomposite polyurethanes. FTIR and TGA analyses indicated that more polyester segments had reacted with silica particles during in situ polymerization than during the blending method, accompanied by higher T_g and more homogeneous dispersion of nanosilica particles in the polymer matrix from in situ polymerization. Maximum values in T_g, tensile properties, macrohardness, abrasion resistance, and UV absorbance were obtained when the particle size of silica was about 28 nm. The polyurethane/nanosilica composites obtained by in situ polymerization generally had better mechanical properties than those by the blending method except for some unexpected macrohardness at relatively high silica content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1032–1039, 2005     

Effect of silane coupling agents on the properties of pine fibers/polypropylene composites

In the present work, PP‐based composites, reinforced with surface modified pine fibers, have been prepared. The surface of the fibers has been treated with several silane derivatives bearing specific functionalities. ? NH₂, ? SH, long aliphatic chain, and methacrylic group were chosen as functionalities of the silane derivatives for evaluating the compatibility with the polymer matrix. Mechanical analysis, contact angle and XPS spectra, SEM microscopy, and water uptake measurements were used as characterization techniques for evaluating the nature of composites. XPS as well as contact angle measurements demonstrated that pine fibers and silane derivatives were effectively coupled. The mechanical analysis showed an increase in Young's and flexural moduli, by 12% and 130% respectively, and nonsignificant changes in the ultimate tensile strength were noted after surface modification. Water uptake measurements revealed a low water absorption by the materials, always lower than 2 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3706–3717, 2007     

Effect of filler partitioning on the mechanical properties of TPO/nanosilica composites

Nanosilica (SiO₂) is used as a reinforcing filler in PP/elastomer thermoplastic polyolefin (TPO) blends containing ethylene‐octene polyolefin elastomer (POE), ethylene‐propylene rubber (EPR), and maleated EPR. The localization and dispersion of the filler are controlled by adding maleated derivatives to the matrix or the dispersed phase. A separated morphology, consisting of SiO₂ residing in the PP matrix, is necessary to achieve improvements in modulus. Filled TPOs containing POE have the best performance and exhibit improved moduli while retaining high values of elongation. J. VINYL ADDIT. TECHNOL., 13:147–150, 2007. © 2007 Society of Plastics Engineers     

Effect of silane‐coupling agents on interfacial properties of CF/PI composites

In this article, to form a structure‐controlled interface, carbon fiber (CF) surfaces were first activated by plasma technique and then hydroxylated by LiAlH₄ treatment, and then were reacted with a suit of silane‐coupling agents terminated with desired functional groups to form thin films, which further reacted with polyimide (PI) resin to generate a strong adhesion interface. The morphology, structure, and composition of CF surfaces before and after treatment were investigated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS), respectively. The results of FTIR and XPS analysis showed that silane‐coupling agents were successfully chemisorbed onto the CF surfaces by the hydrolysis and condensation reactions. The interfacial shear strength of the CF/PI microcomposites was evaluated by the microbond technique. The results showed that the types of the interfacial functional groups, especially the vinyl end groups in vinyltriethoxysilane (VS), which can react with PI resin, had very significant influence on the improvement of the interfacial adhesion properties of composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Study on the mechanical properties and microstructure of high-performance carbon fiber/epoxy composites

A high-toughness epoxy has been prepared using carboxyl-terminated butadiene acrylonitrile (CTBN) as a toughening agent to modify the AG-80 epoxy resin. High-performance carbon fiber/epoxy (CF/EP) composites are fabricated using the CTBN-toughened epoxy resin as the matrix and two types of CF, namely, T800SC and T800HB, as reinforcement. The mechanical properties of the matrix, surface properties of the CFs, tensile properties, and fracture morphologies of the composites are systematically investigated to elucidate the key factors influencing interfacial bonding in high-performance CF/EP composites. The results reveal that the most significant improvement in toughness is achieved when the CTBN content is 6.90 wt.% in the epoxy resin. Owing to the high content of polar functional groups and excellent surface wettability of T800SC, the T800SC/EP composite exhibits superior mechanical properties compared with the T800HB/EP composite.     

Effect of coupling agents on the mechanical properties of fly ash/polyester particulate composites

Fly ash (FA)/general purpose unsaturated polyester resin (GPR) particulate composites were made. The effect of the surface treatment of FA with two different silane coupling agents (CAs) on the mechanical properties, such as the tensile, flexural, compressive, and impact strengths and hardness, of FA–GPR composites were studied. The properties of FA–CA–GPR were also compared with that of GPR and CaCO₃–GPR. An enhancement in the tensile, flexural, compressive, and impact strengths and a decrease in the tensile and flexural moduli were observed when FA was surface treated with CA. Hardness also increases with CA‐treated FA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1755–1760, 2001     

Effect of different coupling agents on chemical structure and physical properties of vinyl acetate/wood polymer composites

This research investigated the effect of chemical modification with vinyl acetate in combination with different coupling agents (maleic anhydride, 3-(trimethoxysilyl) propyl methacrylate and glycidyl methacrylate) on chemical structure and physical properties of poplar wood. Samples were impregnated with chemicals using vacuum-pressure method following by vinyl acetate. Fourier transform infrared analysis results confirmed cell wall chemical modification, that was more obvious for glycidyl methacrylate ones. Dimensional stability of resultant composite enhanced via crosslink formation between modified wood and polymer, which affected by cell wall modification rather than in situ polymerization. In comparison of coupling agents, glycidyl methacrylate mostly improved the physical properties of wood as well as combined modified composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47467.     

Effect of nanosilica with different interfacial structures on mechanical properties of polyimide/SiO2 composites

In this article, the effects of coupling agent, silica particle size, and particle shape on the mechanical properties of polyimide (PI) were studied by molecular dynamics (MD) simulations, and the effect of SiO₂ surface treated with coupling agent on the mechanical properties of PI was investigated by experiment. At the same doping volume fraction (5%), the simulation results show that the surface interaction energy between the matrix and particle gradually increases with the radius of the embedded nanoparticles. Meanwhile, the interface interaction energy and mechanical properties of the sphere-type were significantly higher than the ones of other shaped nanoparticles. Moreover, the simulations were compared with the experimental results; atomic force microscopy and scanning electron microscopy images can verify that after being treated with coupling agent, interface interaction between nanosilica and PI enhances quite a little. The mechanical experimental results show that the tensile strength and elasticity modulus of pure PI, unbonded (UB) PI/SiO₂, and bonded PI/SiO₂ films are 34.47 and 1.13, 36.46 and 1.32, and 66.20 MPa and 1.72 GPa, respectively. It is indicated that the coupling agent plays a crucial role in nanocomposites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48595.     

Comparison of primary and secondary aminosilance coupling agents in anhuydride-curde epoxy fiberglass composites

Fourier transform infrared spectroscopy (FT-IR) has been utilized to investigate the interfacial chemical bonding at the interfaces of the aminosilanes and the nedic methyl anhydiride cured epoxy matrix in fiber-reinforced composites. It is found that the nedic methyl anhydride can react with γ-aminopropyltriethoxysilane (APS) and N-methylaminoproplytrimethoxysilane (MAPS). In comparing the relative reactivities of two coupling agents to the epoxy resin, the secondary aminosilance has a higher reactivity than the primary aminosilance. An elevated temperature is required for the copolymerization to take place between the silane and the epoxy resin. The results indicate that covalent bonds form at the coupling agents. The molecular structure of the interface in MAPS treated fiberglass reinforced composites is different from that of the APS treated fiber composites. In addition, an accelerated copolymerization initiated by the coupling agent treated surface is also found in the resin interphase which may be important in determining the mechanical properties of the composites.     

Effect of coupling agents on the degradation of polypropylene/fly ash composites

Composites containing 50% wt fly ash (sourced from the UK and South Africa) in polypropylene homopolymer (manufacturer stabilized for general purpose use) have been prepared by using batch and continuous methods. The effect of the following coupling agents were investigated on the photo‐ and thermal‐decomposition of the composite materials: Lubrizol Solplus C800 (an unsaturated carboxylic acid), γ‐methacryloxypropyl trimethoxy silane (γ‐MPS), 1,3‐phenylene dimaleimide (BMI), and maleic anhydride‐grafted‐polypropylene (m‐PP). High melt, thermal‐, and photo‐stability was favored when the matrix was coupled to the filler surface by monomeric coupling agents that were expected to adsorb in a close packed layer on the fly ash surface. Further improvements were observed in cases where the coupling agent could also self‐polymerize. m‐PP did not lead to increased stability due to its low adsorption density on the fly ash surface. The relatively high water/acid soluble transition metal ion content of the UK sourced fly ash did not appear to affect stability under the test conditions employed in this study. The South African sourced fly ash had a higher level of quartz and mullite together with a high level of group 1 and 2 metals. The latter in particular may have led to debonding of the coupled interfacial region from the filler surface and possible adsorption of stabilizers on the pristine surface. This resulted in the South African fly ash generally possessing poorer resistance to oxidation than the UK fly ash. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39974.     

Effect of nanosilica and microsilica on microstructure and hardened properties of cement pastes and mortars

Abstract

This paper reports the effects of nanosilica (nS), microsilica (silica fume, SF) and their simultaneous use (nS+SF) on “both” the microstructure of cement pastes and the mechanical properties of mortars. After water curing at 21°C for 7, 28 and 90 days, samples with water/binder w/b ratio of 0·35 were characterised by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and compressive strength test. Single or mixed mineral additions did not generate “any” distinct hydration phases compared to the reference material without additives. A decrease in the calcium hydroxide contents in later curing ages indicated a pozzolanic effect of nS and SF. The chemical action promoted by nS together with the physical effect due to the small particle size distribution given by SF result in higher compressive strength and better hardened properties, suggesting the synergistic action of nS+SF compared with single additions.     

Electrical conductivity of epoxy/silicone/carbon black composites: Effect of composite microstructure

The objective of this work is to study the effect of electrical conductivity and physical‐mechanical properties of carbon black (CB) filled polymer composites. This goal is achieved by synthesizing epoxy/silicon phase separated blend structure of composites filled with CB. The percolation threshold of epoxy/silicone/CB composites decreased and the total conductivity increased compared to the pure epoxy/CB composite. A threefold increase was obtained with tensile strength of epoxy/silicone/CB composite with 25 wt% of silicone and 5 wt% of CB in comparison with epoxy/CB systems. This composite has conductivity of about 10⁻⁶ S/cm, which is six orders of magnitude higher than for epoxy/CB composites at the same concentration of CB. POLYM. COMPOS., 35:2234–2240, 2014. © 2014 Society of Plastics Engineers     

Bifunctional coupling agents for improved mechanical properties in fiberglass/polyethylene composites

Two bifunctional compounds, 12‐azido‐1‐diazo‐2‐dodecanone (A) and 1‐diazo‐17‐octadecene‐2‐one (B), show an ability to act as coupling agents in fiberglass/polyethylene composites. Under appropriate conditions the diazoketone functional groups in both A and B react with hydroxyl groups on a fiberglass surface, whereas the azide group in A and the alkene group in B form bonds with the plastic matrix during processing. FTIR and NMR spectroscopy were used to study the decomposition of each of these compounds under heat and UV light. Each treatment resulted in a relatively fast decomposition of the diazoketone functional group, along with a slower reaction of the azide and alkene groups. Thus it was possible to react the diazoketone end of these compounds with a fiberglass surface, without affecting the azide or alkene functional groups on the other ends of the molecules. In samples of treated fiberglass containing compounds A or B and mixed by extrusion with polyethylene, the mechanical properties of the composites had improved properties over composites containing untreated samples of fiberglass. With A as the coupling agent, both the tensile properties and Izod impact showed changes that indicated that a bifunctional bridge was formed between the fiberglass and polyethylene phases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2562–2578, 2002     

Effect of fillers on electrical properties of epoxy composites

The effect of fillers such as glass, ferrite, and carbon on the dielectric properties of epoxide resin along with conductivity has been studied as a function of frequency (1–100 kHz) and temperature (30–200°C). The glass transition temperature is not much affected by the presence of the fillers. The observed higher values of dielectric permittivity and loss in the case of filled polymers are attributed to Maxwell–Wagner–Sillars polarization.     

Effect of polymer/filler interactions on the structure and rheological properties of ethylene-octene copolymer/nanosilica composites

The microstructure and rheology of melt compounded ethylene-octene copolymer (EOC) nanocomposites, containing different types of functionalized matrices and nanosilica particles, were investigated. The EOC matrix was functionalized via silane grafting, using monofunctional (vinyltriethylsilane-VTES) or bifunctional (vinyltriethoxysilane VTEOS) silane agents, to prepare EOC-g-VTES and EOC-g-VTEOS respectively. Two different types of silica were used, unmodified (SiO₂), or modified with octylsilane (oct-SiO₂). Depending on the matrix/filler combination, different types of polymer/filler interactions were present in these composites. The formation of covalent bonds between the VTEOS functionality and the hydroxyl groups present at the surface of the particles, generated strong polymer/filler interactions, resulting in improved filler dispersion. The presence of polymer/filler interactions was confirmed by bound polymer measurements. TEM micrographs revealed a fractal-like composite structure, which agreed with the exponents determined through small angle oscillatory shear rheometry (SAOS). Rheological properties in the melt state revealed significant differences, depending on the types of matrix and filler used. Time-sweep experiments showed pronounced time-dependence indicative of a tendency toward aggregation for the EOC-g-VTES-based composites. On the contrary, strong polymer/filler interactions between EOC-g-VTEOS and oct-SiO₂ resulted in a stable response. During strain-sweep experiments the EOC-g-VTEOS-based composites exhibited a higher critical strain for the onset of non-linearity, indicative of stronger adhesion between the fillers and the matrix. DMA measurements showed that more energy is dissipated during the glass transition in the composites with enhanced polymer/filler interactions.     

Surface‐activated nanosilica treated with silane coupling agents/polypropylene composites: Mechanical,morphological, and thermal studies

This work reports the mechanical, morphological, and thermal properties of the polypropylene (PP) nanocomposites containing nanosilica (nano‐SiO₂) which were treated by different functional group silane coupling agents. Four types of silane coupling agents namely aminopropyltriethoxy silane (APTES), glycidyloxypropyltrimethoxy silane (GPTMS), trimethoxysilylpropyl methacrylate (TMPM), and dichlorodimethyl silane (DCMS) were used to modify the surface‐activated nanosilica. To enhance the effectiveness of the coupling, nanosilica was chemically activated and analyzed through FTIR and X‐ray photo electron spectroscopy (XPS). The highest tensile strength was recorded by the activated nanocomposites treated with APTES followed by nanocomposite treated with GPTMS, TMPM, and DCMS, respectively. The addition of silane coupling agents into nano‐SiO₂/PP system further improved the tensile modulus of the PP nanocomposites. From the transmission electron microscopy (TEM) analysis, activated nanosilica treated with APTES showed better nanosilica dispersion in the PP matrix and lesser agglomeration occurred when compared with the other silane coupling agents which were used in this study. Surface activation process does not effectively increase the degree of crystallinity and thermal stability on the PP nanocomposites. However, with the assistance of the surface treatment, it was found that the thermal behavior of the PP nanocomposites had been enhanced. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers