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1.
A new type of polymeric curing agent (PCA) was synthesized to improve processing property, increase mechanical properties, and decrease volume shrinkage of silicone rubber. The PCA was prepared by co‐hydrolysis condensation of dimethyldiethoxysilane (DDS) and polyethoxysiloxane, then modified by hexamethylcyclotrisilazane (D3N). Commercial silica and tetraethoxysilane (TEOS) were used as controls simultaneously. The properties of polydimethylsiloxane (PDMS) composites were characterized by shear viscosity measurements, room temperature mass loss, linear volume shrinkage, stress‐strain tests, swelling behaviors and thermogravimetric analysis (TGA). PDMS composites using PCA show lower shear viscosity than those using commercial silica. Compared with the traditional PDMS/TEOS curing systems, PDMS/PCA curing systems behave relatively lower volume shrinkage, better reinforcement and thermal properties. In short, PCA acts as a good compromise in providing the best balance of processing property, volume shrinkage, mechanical properties and thermal stability in silicone rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

2.
This paper reports a comparative study of propylene–ethylene copolymer (EP) nanocomposites synthesized using zinc‐ion (Zn2+)‐coated nanosilica (ZNS) and the diglycidyl ether of bisphenol‐A (DGEBA, an epoxy resin)‐modified zinc‐ion‐coated nanosilica (EZNS) as nanofillers. These nanocomposites were prepared using the ‘melt mixing’ method at a constant loading level of 2.5 wt%. This loading level is much lower than that used for fillers in conventional composites. The EP nanocomposites were characterized using wide‐angle X‐ray diffractometer (WAXD), a thermo gravimetric analyzer (TGA), a differential scanning calorimeter (DSC), a dynamic mechanical analyzer (DMA) and scanning electron microscopy (SEM). DMA results showed a higher storage modulus for EP‐epoxy‐modified Zn2+‐coated nanosilica nanocomposite (EP‐EZNS) with respect to EP and EP‐Zn2+‐coated nanosilica nanocomposite (EP‐ZNS). In addition, TGA thermograms showed an increase in degradation temperature of EP in the presence of EZNS. Copyright © 2006 Society of Chemical Industry  相似文献   

3.
The effects of nanosilica type and its content on microstructure, mechanical properties, and rheology of thermoplastic polyurethane (TPU) nanocomposites were investigated. Three different types of silica which included: unmodified (Si-Un) and commercially modified with octylsilane (Si-OS) and polydimethylsiloxane (Si-PDMS) with 5, 10, and 15 wt% of all fillers, were prepared by solution casting method. Scanning electron microscopy (SEM) showed that surface treatment of nanosilica with OS and PDMS reduced the aggregation of particles and improved their dispersion at microlevel. The effect of adding nanoparticles on microdomain morphology of TPU was studied by transmission electron microscopy (TEM), infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The results demonstrated a relatively good interaction between the hard and soft segments in the presence of treated nanosilica that hindered the crystallization of hard segments in TPU. Thermogravimetric analysis (TGA) and tensile test showed that nanocomposites with treated nanosilica have better thermal stability and mechanical properties. The dynamic rheological studies indicated that nanocomposites containing Si-OS and Si-PDMS (with better dispersion and higher interface between the soft and hard domains in TPU) have improved viscoelastic properties in comparison with nanocomposites with untreated silica. In this study, dynamic frequency sweep data were correlated by a generalized Maxwell model and found that elastic constants of TPU chains were improved in the presence of modified silica nanoparticles.  相似文献   

4.
Three types of silane coupling agents, γ‐aminopropyltriethoxysilane, γ‐glycidoxypropyltrimethoxysilane, and γ‐methacryloxypropyltrimethoxysilane, were used as modifiers to modify the surface of the nanosilica, respectively, and the nanocomposites of the epoxy resin filled with nano‐sized silica modified by three silane coupling agents were prepared by physical blending. The properties of the modified silica nanoparticles were characterized by Fourier transform infrared spectrum and particle‐size analyzer. The microstructure, mechanical behavior, and heat resistant properties of the nanocomposites were investigated by transmission electron microscopy, scanning electron microscopy, thermo gravimetric analyses, differential thermal gravity, differential scanning calorimetry, and flexural tests. The results showed that these modifiers are combined to the surfaces of nanosilica by the covalent bonds, and they change the surface properties of nanosilica. The different structures of coupling agents have different effects on the dispersibility and stability of modified particles in the epoxy matrix. In comparison, the silica nanoparticles modified by γ‐glycidoxypropyltrimethoxysilane exhibit a good dispersivity. The nanocomposites with 4 wt% weight fraction nanosilica modified by γ‐glycidoxypropyltrimethoxysilane have higher thermal decomposing temperature and glass transition temperature than those of the other two composites with the same nanosilica contents, and they are raised by 43.8 and 8°C relative to the unmodified composites, respectively. The modified silica nanoparticles have good reinforcing and toughening effect on the epoxy matrix. The ultimate flexural strengths of the composites with 4 wt% nanoparticles modified by γ‐aminopropyltriethoxysilane, γ‐glycidoxypropyltrimethoxysilane, and γ‐methacryloxypropyltrimethoxysilane are increased by 10, 30, and 8% relative to the unmodified composites, respectively. The flexural fracture surfaces of modified composites present ductile fracture features. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers  相似文献   

5.
Surface modification of fumed nanosilica was performed by using n‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane as a coupling agent. Then, modified nanosilica was utilized in the preparation of polyurethane rigid foam. The characterization and the study of properties were done by some techniques, such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic mechanical analysis, and thermomechanical analysis. Also, tensile test was examined to evaluate the static mechanical properties. With the increasing of modified nanosilica, thermal and static mechanical properties were enhanced, but dynamic mechanical behavior was different from static mechanical behavior because of the different properties of interfacial domain and bulk matrix. The presence of functional groups on the nanosilica surface affected stoichiometry and reduced hard phase formation in bulk polymer. The decrease in glass transition temperature (Tg) confirmed this statement. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers  相似文献   

6.
This article reports a comparative study of polypropylene (PP) nanocomposites synthesized with nanosilica (NS) and diglycidyl ether of bisphenol A, an epoxy‐resin‐grafted nanosilica (ENS), as nanofillers. These nanocomposites were prepared with the melt‐mixing method at a constant loading level of 2.5 wt %; this loading level was much lower than that used for fillers in conventional composites. The effects of pure NS and ENS on the thermal, structural, mechanical, and dynamic mechanical properties of PP were analyzed with wide‐angle X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and scanning electron microscopy. The transmission electron microscopy studies showed a better dispersion of ENS in the PP matrix, that is, in the polypropylene‐epoxy‐resin‐grafted nanosilica (PP–ENS) nanocomposite, in comparison with NS in the PP matrix, that is, in the polypropylene–nanosilica (PP–NS) nanocomposite. Also, the thermogravimetric analysis results showed a higher thermal stability for PP–ENS than PP–NS. Furthermore, the dynamic mechanical analysis studies showed an increase in the elastic modulus and glass‐transition temperature for PP–ENS with respect to PP–NS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2117–2124, 2006  相似文献   

7.
The morphological structure, glass transition, mechanical properties, and dynamic mechanical properties of star‐shaped solution‐polymerized styrene‐butadiene rubber (SSBR) synthesized by a multifunctional organic lithium initiator and SiO2‐SSBR composite (N‐SSBR) prepared through adding a small amount of nanosilica modified by silane coupling agent to star‐shaped SSBR synthetic solution and co‐coagulating, and their nanocomposites filled with 20 phr nanosilica were investigated, respectively. The results showed that the silica particles were well dispersed with nanosize in N‐SSBR, which glass‐transition temperature (Tg) was 2°C higher than SSBR. N‐SSBR/SiO2 nanocomposite exhibited lower Payne effect and internal friction loss, higher mechanical properties, and its Tg was 2°C higher than SSBR/SiO2 nanocomposite. N‐SSBR might promote the dispersion of nanosilica powder in matrix and could be applied to green tire tread materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

8.
In this work, novel thermoresponsive shape memory composites based on glass fiber and nanosilica‐modified liquid crystalline epoxies (LCEs) with lateral substituent were prepared and characterized. According to the comprehensive analysis of polarized optical microscopy, wide‐angle X‐ray diffraction measurements, and tan δ data, the orientation of mesogen units were hindered by the introduction of nanosilica and lateral substituents of liquid crystalline epoxies, so that additional physical cross‐links except for similar chemical cross‐links emerged with the introduction of surface‐treated nanosilica. And the increased cross‐links could enhance the shape memory properties of the composites which could recover to their original state quickly in a time shorter than 30 s with high shape fixing ratios (>96%) and high shape recovery ratios (>98%), which indicated the composites could be applied into self‐deployable structural materials. Moreover, the reinforcement in the dynamic storage moduli, tensile modulus, and the tensile strength and shape memory properties indicated that glass fiber and nanosilica‐modified shape memory liquid crystalline epoxy composites could be high‐performance composites and could be used as new candidates for aerospace smart materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42616.  相似文献   

9.
In this article, nano‐zinc oxide (ZnO) filled ethylene propylene diene monomer (EPDM) composites are prepared, and the mechanical (static and dynamic) properties and thermal conductivity are investigated respectively, which are further compared with the traditional reinforcing fillers, such as carbon black and nano‐silica. Furthermore, influence of in‐situ modification (mixing operation assisted by silane at high temperature for a certain time) with the silane‐coupling agent Bis‐(3‐thiethoxy silylpropyl)‐tetrasufide (Si69) on the nano‐ZnO filled composites is as well investigated. The results indicate that this novel reinforcing filler nano‐ZnO can not only perform well in reinforcing EPDM but can also improve the thermal conductivity significantly. In‐situ modification with Si69 can enhance the interfacial interaction between nano‐ZnO particles and rubber matrix remarkably, and therefore contribute to the better dispersion of filler. As a result, the mechanical properties and the dynamic heat build‐up of the nano‐ZnO filled composites are improved obviously by in‐situ modification, without influencing the thermal conductivity. In comparison with traditioanl reinforcing fillers, in‐situ modified nano‐ZnO filled composites exhibit the excellent performance in both mechanical (static and dynamic) properties and better thermal conductivity. In general, our work indicates that nano‐ZnO, as the novel thermal conductive reinforcing filler, is suitable to prepare elastomer products serving in dynamic conditions, with the longer expected service life. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

10.
Nanosilica particles were dispersed into polymer diols by high pressure shearing homogenizer (HPSH), then polyurethane nanocomposites were prepared via in-situ polymerization of diphenylmethane diisocyanate (MDI) and polymer diols. FTIR analysis indicated that the -NCO groups of MDI had reacted with the hydroxy on the surface of nanosilica during in-situ polymerization. TGA suggested that polyurethane/nanosilica composites obtained by in-situ polymerization had better thermal stability than pure polyurethane. Meanwhile, the tensile and dynamic mechanical properties of the samples prepared by HPSH were superior to those by directly ultrasonic dispersing nanosilica, accompanied by more homogeneous dispersion of nanosilica particles in the polymer matrix.  相似文献   

11.
Zinc oxide (ZnO) nanoparticles were successfully prepared by a one‐step precipitation reaction in an aqueous solution of zinc acetate and sodium hydroxide with stearic acid (SA) as the modifying agent. Hydrophilic composites of poly(ethylene terephthalate) (PET), poly(ethylene glycol), and ZnO nanoparticles were prepared further by in situ polymerization. The surface modification of ZnO and the microstructure and properties of prepared nanoparticles were investigated by relative contact angle measurements (CA), Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy, and thermogravimetric analysis (TGA). Measurements of CA and XRD indicated that the surface‐treated ZnO was hydrophobic and had a significant improvement in crystallinity with SA. Compared with the nanocomposites filled with the pure ZnO, the modified ZnO exhibits a better dispersion in PET–PEG matrix. TGA results showed that the presence of modified ZnO nanoparticles can improve the thermal stability of PET–PEG matrix. CA and low field nuclear magnetic resonance methods were used to investigate the hydrophilic behavior of nanocomposites. The results revealed that modified nanoparticles had a positive effect on the bound water absorption. A simple model for the interactions between ZnO, SA, and PET–PEG matrix was proposed. POLYM. COMPOS., 37:1830–1838, 2016. © 2015 Society of Plastics Engineers  相似文献   

12.
Fly ash (FA) is a porous ceramic, which has proved to have some favorable functions. In this article, we have prepared a series of fly ash filled composites, where the polyurethane‐(PU) modified epoxy (EP) was acted as the matrix. With the purpose of characterizing the effect of the content of PU in the matrices and the surface‐treatment (ST) of fly ash particulates on the dynamic mechanical properties of composites, Fourier transform infrared spectral analysis (FTIR), microstructure observation, impact property test as well as dynamic mechanical analysis (DMA) were systematically investigated. With FTIR test, it can be found that the chemical reactions occur, and new chemical structures are formed between EP and PU, and the functionalized groups existing on the surface of fly ash particulates can also be detected. In fractographs observation of composites, it can be seen that the silane coupling agent improves the interfacial bonding conditions between fly ash particulates and the matrix. Impact property test result reveals that PU improves the toughness of EP. Dynamic mechanical analysis of the composites is carried out from ?40 to 150°C using a tension‐compression mode. Results show that the composites, whose matrices are with 10 and 20 wt % PU, may possess better dynamic mechanical properties as compared with the other composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

13.
Pristine diatomite was first purified by acid treatment and then modified with γ‐methacryloxy propyl trimethoxysilane molecule (KH570) to introduce hydrophobic chains on the surface of acid‐treated diatomite. Fourier‐transform infrared spectroscopy and thermogravimetric analysis (TGA) indicated that the silane coupling agent (KH570) was successfully grafted on the diatomite through covalent bonding. The digital photos showed that the silanization process changed the surface property of the diatomite. The poly(vinyl chloride) (PVC)/pristine diatomite and PVC/modified diatomite composites were prepared via two‐roll mill. The thermal stability and mechanical properties of PVC composites were investigated by TGA, mechanical properties tests, and dynamic mechanical analysis. The results showed that the thermal stability of the composites improved and maximum weight loss temperature (Tmax) of the PVC composite with 1 phr modified diatomite was about 20°C higher than that of PVC composite without diatomite. The PVC/modified diatomite composites exhibited better mechanical properties owing to the stronger interfacial interaction between PVC matrix and modified diatomite. But the impact strength reduced sharply when the addition of diatomite was more than 1 phr. The reason of the phenomenon is that the diatomite plays the role of defects in PVC and it works against the absorption of impact strength energy. It was proved by the results of scanning electron microscopy. J. VINYL ADDIT. TECHNOL., 25:E39–E47, 2019. © 2018 Society of Plastics Engineers  相似文献   

14.
This study explored the modifying effects of wood flour (WF) with citric acid (CA) on the rheological and mechanical properties of WF/high density polypropylene (HDPE) composites. WF was treated with CA, which acts a cross‐linking agent and melt‐blended with HDPE with a twin‐screw extruder. Injection molding was used to make tensile and impact tests samples. The rheological properties of the blends were characterized using a Haake microcompounder, torque‐, capillary‐, and rotational‐rheometer, respectively. Results show that the thermal stability of WF decreased after treatment. Compared with those of untreated composites, the tensile strength, elongation‐at‐break, and impact strength of the composites treated with 5% CA were reduced by 6%, 14%, and 16%, respectively. This reduction was attributed to embrittlement of WF, which may negatively influence the mechanical properties of the resulting composites. Scanning electron microscopy revealed better dispersion of CA‐treated WF in the composites than the untreated WF. For composites treated with 5% CA, the melt torque, viscosity, moduli, and shear stress decreased significantly, indicating an improvement in processibility. This improvement is attributed to uniform dispersion of the modified WF, as well as to better interfacial adhesion between WF and the matrix. Results suggest that treating WF with CA shows promise for improving the processibility of highly filled thermoplastic composites via extrusion/injection molding processing. POLYM. COMPOS., 37:553–560, 2016. © 2014 Society of Plastics Engineers  相似文献   

15.
In this work, sugarcane bagasse fibers were used as filler in composites having recycled high‐density polyethylene (PEr) as matrix. Because of the poor interaction between fibers surface and the PEr, the surface of bagasse was chemically modified. This modification consists of washing with water at 80°C, a mercerization process using sodium hydroxide and acetylation reaction with acetic anhydride. The chemical modification was characterized by Fourier transform infrared–horizontal attenuated total reflectance (FTIR‐HATR) and 13C nuclear magnetic resonance spectroscopies (NMR), thermogravimetric analysis (TGA), and scanning electronic microscopy (SEM). The composites were prepared from modified and unmodified fibers into PEr matrix, containing 5, 10, and 20% (w/w) of fiber. The samples were processed by extrusion and molds were prepared by injection process in order to perform mechanical tests. These materials were analyzed by SEM, TGA, and the water uptake was evaluated. Also, their mechanical properties were analyzed. Morphological analysis indicated that the chemical modification of sugarcane bagasse increased the compatibility between matrix and reinforcement. Tensile, flexural, and impact tests showed that the mechanical properties of the composite were improved compared to PEr due to the presence of the fibers. POLYM. COMPOS., 35:768–774, 2014. © 2013 Society of Plastics Engineers  相似文献   

16.
Mechanical and dynamic mechanical properties of a waste rubber powder‐filled high‐density polyethylene (HDPE) composite are investigated. Rubber powder is surface‐modified with acrylamide (AAm) using ultraviolet. Rubber powder and HDPE are extruded using a single‐screw extruder and maleic anhydride‐grafted polypropylene is added as a compatibilizer to improve the adhesion between rubber powder and HDPE. The tensile stress and strain of AAm‐grafted rubber powder/compatibilizer/HDPE composites always exhibit higher values than those of unmodified rubber powder/HDPE composites. Surface modification of rubber powder is shown to decrease the magnitude of the tan δ of the HDPE composite. Higher values of the notched Izod impact strength of a surface‐modified rubber‐filled composite is observed compared to those of unmodified rubber‐filled composite. Experimental results show that acryl amide‐grafted rubber powder reacts with maleic anhydride and it results in improved mechanical properties of the HDPE composite. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2595–2602, 2000  相似文献   

17.
A series of novel polydimethylsiloxane (PDMS) composites were prepared using octa[(trimethoxysilyl)ethyl]‐POSS (OPS) as cross‐linker and fumed silica as reinforcing filler. The cross‐linked networks, morphologies, thermal and mechanical properties of these novel PDMS composites were examined by attenuated total reflection infrared spectroscopy and the extraction/swelling experiment, scanning electron microscope, thermogravimetric analysis, and universal tensile testing machine, respectively. It was found that both the resistance to thermal degradation and mechanical properties of the novel PDMS composites were improved greatly by adding fumed silica. The prominent improvements in resistance to thermal degradation and mechanical properties of novel PDMS composites were likely attributed to the enhanced interaction of PDMS chains and aggregated particles resulted from synergistic effect between POSS and fumed silica. Meanwhile, we also found that the resistance to thermal degradation of the PDMS composites was lowered slightly with the further increment in loading fumed silica, but their mechanical properties were enhanced. The slight decrease in trend of the resistance to thermal degradation of the novel PDMS composites was likely ascribed to the increasing amount of hydroxyl groups resulting from fumed silica. And the improving mechanical properties were mainly attributed to the increasing interaction of PDMS chains and aggregated particles originated from synergistic effect between POSS and fumed silica. POLYM. COMPOS., 34:1041–1050, 2013. © 2013 Society of Plastics Engineers  相似文献   

18.
The properties of nano‐zinc oxide master batch filled butadiene styrene rubber (SBR) systems were researched in comparison with those of common zinc oxide and nano‐zinc oxide filled systems. First, the nano‐zinc oxide master batch was prepared and the cure characteristics of three different kinds of zinc oxide filled SBR composites were studied; second, the mechanical properties and wear resistance were compared; then, the improved mechanical properties were confirmed by dynamic mechanical properties and transmission electron microscopy. Finally, the zinc oxide amount reducing mechanism was analyzed. Results show that nano‐zinc oxide master batch filled SBR system has better mechanical properties than those of nano‐zinc oxide and common zinc oxide filled systems, which is due to the improved dispersion by master batch mixing technology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 922–930, 2006  相似文献   

19.
Composites of polydimethylsiloxane (PDMS) rubber modified by three kinds of polyhedral oligomeric silsesquioxanes (POSSs) as well as fumed silica were prepared through solution blending and then open two‐roll mill blending with curing agent. Subsequently, the influences of POSS on mechanical and thermal properties of the resulting composites were investigated in detail. The addition of POSS significantly enhanced the tensile strength and elongation at break of the composite but lowered the tensile modulus, which could be ascribed to the interruption of silica–silica and silica–PDMS interactions. Octamethylsilsesquioxane (OMS)/silica/PDMS and octaphenylsilsesquioxane (OPS)/silica/PDMS composites did not show desirable mechanical and thermal properties. Nevertheless, heptaphenylvinylsilsesquioxane (VPS)/silica/PDMS composite with 5 wt % VPS exhibited enhanced glass transition temperature (Tg), mechanical properties, and thermal stability. Further studies revealed that more VPS unfavorably affected properties of the composite. Scanning electron microscope and X‐ray diffraction demonstrated that owing to the grafting reaction, 5 wt % VPS in the rubber matrix could form microcrystal domains the most effectively. Thus, the improved mechanical properties and thermal stability just resulted from the the formation of microcrystal domains and the increase in stiffness of PDMS chains because of the graft of VPS onto PDMS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42173.  相似文献   

20.
The effect of electron beam irradiation on the technical properties of fly ash (FA) and nano fly ash (NFA)‐filled waste polyethylene (WPE) composites have been investigated in this article. It is observed that the FA/NFA at 5 wt% imparted enhanced technical properties. The modified composites were prepared by three different methods (1) modification of WPE matrix first by grafting with maleic anhydride (MA) and preparing the composite (2) Preparing WPE‐FA/NFA composites and subjecting to electron beam irradiation. (3) Subjecting the FA/NFA to electron beam radiation first and then preparing composites with WPE. Of the three methods, the composite prepared and then electron beam irradiated gave the best balance in the physico‐mechanical properties. The tensile and flexural strength of WPE increased from 21.2 MPa and 25.4 MPa to 33.0 MPa (57.8%) and 45.8 MPa (72%) respectively at 5 wt% FA‐filled WPE composites, which further increased to 34.5 MPa (65%) and 47.7 MPa (87.8%) respectively with 5 wt% of NFA‐filled WPE composites, after electron beam irradiation. The thermal stability was enhanced upon electron beam irradiation of the composites. The dynamic mechanical properties reveal that the storage modulus reaches the highest value for the irradiated composite corroborating with the flexural modulus throughout the temperature range studied. The fractured surfaces were examined under SEM and were correlated with the mechanical properties. The results indicate that FA/NFA reinforced WPE composites act as an excellent stress raisers preventing crack propagation and enhancing the performance properties on electron beam irradiation. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers  相似文献   

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