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1.
Polyurethane/clay nanocomposites have been synthesized using Na+‐montmorillonite (Na+‐MMT)/amphiphilic urethane precursor (APU) chains that have hydrophilic polyethylene oxide (PEO) chains and hydrophobic segments at the same molecules. Nanocomposites were synthesized through two different crosslinking polymerization methods. One is UV curing of melt mixed APU/Na+‐MMT mixtures; the other is coalescence polymerization of APU/Na+‐MMT emulsions. These two kinds of composites had intercalated silicate layers of Na+‐montmorillonite by insertion of PEO chains in APU chains, which was confirmed by X‐ray diffraction measurement and transmission electron microscopy. These composite films also showed improved mechanical properties compared to pristine APU films. Although the two kinds of nanocomposites exhibited the same degree of intercalation and were synthesized based on the same precursor chains, these nanocomposite films had the different mechanical properties. Nanocomposites synthesized using APU/Na+‐MMT emulsions, having microphase‐separated structure, had greater tensile strength than those prepared with melt‐mixed APU/Na+‐MMT mixtures. Location of intercalated Na+‐MMT by PEO chains at the oil–water interface also could be confirmed by rheological behavior of the APU/Na+‐MMT/water mixture. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3130–3136, 2003  相似文献   

2.
The gas‐barrier properties of elastomer are of particular importance, especially for airtight applications. Poly(di‐isoamyl itaconate‐co‐isoprene) (PDII) is a newly invented and respectable biobased elastomer, but the barrier properties of PDII and its composites with carbon black and silica are not satisfying at all. Because there are abundant ester groups in PDII macromolecules and these groups can contribute to the homogeneous dispersion of layer silicates, we applied layered silicates, including montmorillonite (MMT) and rectorite (REC), into the PDII matrix to improve the air impermeability. MMT/PDII and REC/PDII composites were prepared by a cocoagulation method, and the air impermeability of the PDII elastomer was highly improved. The smallest gas permeability index reached 1.7 × 10?17 m2 Pa?1 s?1 at an REC content of 80 phr; this implied a reduction of 85.5%. A comparison of the two types of silicate/PDII composites showed that the MMT/PDII composites had better properties at low filler contents, whereas the REC/PDII composites had better mechanical and gas‐barrier properties at high filler contents. Other structures and properties of the composites were investigated by X‐ray diffraction, transmission electron microscopy, and dynamic mechanical rheology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40682.  相似文献   

3.
Polyacrylamide/sodium alginate modified montmorillonite (PAM/SA‐MMT) superabsorbent composites were synthesized by free‐radical polymerization under normal atmospheric conditions. They were characterized by X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). Their water absorbency and methylene blue (MB) adsorption behaviors were studied. Compared with PAM/MMT composites, PAM/SA‐MMT composites demonstrated greater water absorbency (863 g g?1 in distilled water and 101 g g?1 in 0.9 wt % NaCl solution) and higher adsorption capacity of 2639 mg g?1 for MB. The adsorption behaviors of the composites showed that the isotherms and adsorption kinetics were in good agreement with the Langmuir equation and pseudo‐second‐order equation, respectively. FTIR analysis suggested that the MB adsorption of PAM/SA‐MMT composites via a mechanism combined electrostatic, H‐bonding and hydrophobic interaction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40013.  相似文献   

4.
Biodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. In the present investigation blends of chitosan and gelatin with various compositions were produced as candidate materials for biomedical applications. Fourier transform infrared spectral analysis showed good compatibility between these two biodegradable polymers. The composite films showed improved tensile properties, highly porous structure, antimicrobial activities, low water dissolution, low water uptake and high buffer uptake compared to pure chitosan or gelatin films. These enhanced properties could be explained by the introduction of free ? OH, ? NH2 and ? NHOCOCH3 groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (? NH3+) of the chitosan and the carboxylate ions (? COO?) of the gelatin. Scanning electron microscopy images of the blend composite films showed homogeneous and smooth surfaces which indicate good miscibility between gelatin and chitosan. The leafy morphologies of the scaffolds indicate a large and homogeneous porous structure, which would cause increased ion diffusion into the gel that could lead to an increase in stability in aqueous solution, buffer and temperature compared to the gelatin/chitosan system. In vivo testing was done in a Wistar rat (Rattus norvegicus) model and the healing efficiencies of the scaffolds containing various compositions of chitosan were measured. The healing efficiencies in Wistar rat of composites with gelatin to chitosan ratios of 10:3 and 10:4 were compared with that of a commercially available scaffold (Eco‐plast). It was observed that, after 5 days of application, the scaffold with a gelatin to chitosan ratio of 10:3 showed 100% healing in the Wistar rat; however, the commercial Eco‐plast showed only a little above 40% healing of the dissected rat wound. Copyright © 2012 Society of Chemical Industry  相似文献   

5.
A new ternary nanocomposite has been developed using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate (16 Me‐MMT) from sodium montmorillonite (Na+‐MMT). Wide angle X‐ray diffraction and transmission electron microscopic analysis confirmed the intercalation of the polymer chains in between the organosilicate layers and the nanoscale distribution of 16 Me‐MMT in polymer matrix, respectively. The measurement of mechanical properties for 2–8 wt% of 16 Me‐MMT loadings showed a significant increase in tensile strength, elongation at break, and modulus at different elongations. Such an improvement in mechanical properties has been correlated based on the fracture behavior of nanocomposite by SEM analysis. Thermal stability of EPDM/EVA/layered silicate ternary nanocomposites also showed substantial improvements compared with the neat EPDM/EVA blend, confirming thereby the formation of a high performance nanocomposite. POLYM. ENG. SCI., 46:437–843, 2006. © 2006 Society of Plastics Engineers  相似文献   

6.
Because of high wear rate and low thermal deformation temperature, the generalization and application of polytetrafluoroethylene (PTFE) in the field of tribology is restrained to a certain extent. In order to improve the wear resistance and thermal stability of this self‐lubricating polymer, organic montmorillonite (OMMT) nanoparticle reinforced polyethersulfone (PES) and PTFE ternary composites were prepared by the cold molding and vacuum sintering technology. The effects of sodium montmorillonite (Na‐MMT) and OMMT on the microstructures, thermal stabilities and tribological properties of PTFE composites were comparatively studied. The results show that the thermal stability of the PES/PTFE composites is clearly improved by the incorporation of OMMT nanoparticles. Not only the friction coefficients but also the wear rates of OMMT/PES/PTFE composites are less than those of Na‐MMT/PES/PTFE composites under identical tribological tests. Of all these PTFE composites, the PES/PTFE composite containing 10.0 wt% OMMT nanoparticles exhibits the best friction and wear properties (μ = 0.14, k = 5.78 × 10?15 m3 N–1 m?1). This can be attributed to the existence of a polymer multicomponent layer consisting of PTFE, PES and OMMT on the composite surface as well as the formation of uniform PTFE transfer film on the worn surfaces of metal counterparts.  相似文献   

7.
BACKGROUND: The development of polymeric nanocomposites incorporating intercalated or exfoliated layered silicate clays into the organic matrix has been substantially motivated by the significant improvements induced by the presence of the inorganic component. Moreover, understanding and controlling the dispersion of inorganic layers into segmented polyurethane matrices by means of ionic interactions, and exploiting these interactions to enhance physicomechanical behaviour, could be of great interest in the field of polymer nanocomposites. RESULTS: New cationic polyurethane elastomers were prepared starting from poly(butylene adipate)diol (Mn = 1000 g mol?1), 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol and N‐methyldiethanolamine or N,N′‐β‐hydroxyethylpiperazine, used as potential quaternizable moieties. The characterization of the polymers was achieved using specific analyses employed for the macromolecular samples (Fourier transform infrared and 1H NMR spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography). An extension of our research on polymers reinforced with organically modified montmorillonite (OM‐MMT) in order to prepare hybrid composites with improved properties was performed and the resulting materials were characterized using TGA, X‐ray diffraction, atomic force microscopy and scanning electron microscopy. Also, the mechanical properties of the cationic polyurethane/OM‐MMT composites were investigated in comparison with the pristine ionic/non‐ionic polymers and their composites containing non‐ionic polymer blended with OM‐MMT or ionic polymer and unmodified MMT. CONCLUSION: The insertion of the organically modified clay into the polymeric matrix gave an improvement of the mechanical properties of the polyurethane composites, especially the tensile strength and stiffness of the hybrid materials. Copyright © 2009 Society of Chemical Industry  相似文献   

8.
Epoxy resin of bisphenol-C-formaldehyde (EBCF) was synthesized and its structure was confirmed by FTIR and 1HNMR techniques. Untreated jute and a 4 % sodium hydroxide-treated jute composites of EBCF, araldites (GY508 and GY6010) and their hybrid composites were fabricated by hand layup technique followed by compression-molding technique. Mechanical, electrical and water absorption behavior of the composites was studied by standard test methods. The composites showed good mechanical and electrical properties, excellent hydrolytic stability and almost identical water absorption tendency. To some extent, alkali-treated jute composites displayed improved mechanical properties and water absorption tendency. EBCF-based jute and hybrid composites showed comparable mechanical and electrical properties and water absorption behavior with araldite-based composites. Among jute–EBCF, jute–araldite and their hybrid composites, J–EBCF showed the highest impact strength (26 kg m?2), Barcol hardness (34), volume resistivity (2.7 × 10?11 Ω cm) and diffusivity (7.19 × 10?13 m2 s?2). J–GY-1 showed the highest tensile strength (43.7 MPa), flexural modulus (4.26 GPa), % equilibrium water absorption (19.36 %) and equilibrium water absorption time (480 h). Good mechanical and electrical properties and excellent hydrolytic stability of both types of the composites suggested their usefulness for low load-bearing housing, and electrical and marine applications. Thus, EBCF has found its commercial importance as that of the commercial araldite resins.  相似文献   

9.
Hydrogels with good mechanical and self‐healing properties are of great importance for various applications. Poly(acrylic acid)–Fe3+/gelatin/poly(vinyl alcohol) (PAA‐Fe3+/Gelatin/PVA) triple‐network supramolecular hydrogels were synthesized by a simple one‐pot method of copolymerization, cooling and freezing/thawing. The PAA‐Fe3+/Gelatin/PVA triple‐network hydrogels exhibit superior toughness, strength and recovery capacity compared to single‐ and double‐network hydrogels. The mechanical properties of the synthesized hydrogels could be tailored by adjusting the compositions. The PAA‐Fe3+/Gelatin/PVA triple‐network hydrogel with 0.20 mmol Fe3+, 3% gelatin and 15% PVA could achieve good mechanical properties, the tensile strength and elongation at break being 239.6 kPa and 12.8 mm mm?1, respectively, and the compression strength reaching 16.7 MPa under a deformation of about 91.5%. The synthesized PAA‐Fe3+/Gelatin/PVA triple‐network hydrogels have good self‐healing properties owing to metal coordination between Fe3+ and carboxylic groups, hydrogen bonding between the gelatin chains and hydrogen bonding between the PVA chains. Healed PAA‐Fe3+(0.20)/Gelatin3%/PVA15% triple‐network hydrogels sustain a tensile strength of up to 231.4 kPa, which is around 96.6% of the tensile strength of the original samples. Therefore, the synthesized triple‐network supramolecular hydrogels would provide a new strategy for gel research and expand the potential for their application. © 2019 Society of Chemical Industry  相似文献   

10.
To elucidate the improvement and the principle of graphene modification on the polyimide (PI), (3-aminopropyl) triethoxysilane-modified graphene (PMG), was designed and prepared by anchoring the (3-aminopropyl) triethoxysilane (APTS) chain on the graphene sheet surface, and used to synthesise PI composites by in situ polymerisation. The unique surface modification significantly improved the compatibility and dispersion of graphene in the PI matrix. Tensile strength and Young’s modulus of 1.0PMG/PI was 109.45?MPa and 1.73?GPa, which increased by 54.26 and 86.02% from neat PI, respectively. The tribological properties and mechanism were also discussed. The friction coefficient and wear rate of 1.0PMG/PI (0.287, 2.291×10?5mm3?Nm?1) decreased by 47.53% and 35.06%, respectively. This improvement of the tribological properties was mainly caused by the cooperative interaction of the improved mechanical and thermal properties of the composites and the high self-lubricity of modified graphene.  相似文献   

11.
Epoxy‐based composites containing sodium montmorillonite (MMT) modified by silylation reaction with 3‐aminopropyltriethoxysilane (A1100) and N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (A1120) were prepared. The effect of MMT chemical functionalization, as well as inorganic content and dispersion method (i.e., sonication or combination of sonication and ball‐milling) on the morphology and mechanical and thermal properties of composites was thoroughly investigated by X‐ray diffraction analysis, dynamic mechanical and tensile static analysis, nanoindentation measurements and cone calorimeter tests. Morphological characterization showed that the MMT particles are only slightly intercalated by epoxy molecules. Tensile stress, elongation at failure, and toughness of the epoxy composites based on silylated MMT were found to be improved. The presence of 1 and 3% wt/wt of A1100 and A1120 silylated MMT clays allowed the tensile elastic modulus to increase respectively, of about 10 and 15% with respect to the pristine epoxy matrix. The overall results showed that (1) the silylation of MMT clays is a valuable method to improve the interfacial interaction between filler and epoxy matrix and (2) the interfacial interaction plays a role more significant than the clay morphology (i.e., the extent of clay intercalation/exfoliation) over the composite properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

12.
Gelatin/montmorillonite (MMT) hybrid nanocomposite was directly prepared with unmodified MMT and gelatin aqueous solution. Thermal and mechanical properties of the composite were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile tests. The results indicated that an intercalated or partially exfoliated nanocomposite could be achieved, and the properties of the composite were significantly improved. A Tg peak of high temperature disappeared in the DSC curve of the composite, and the thermogravity and thermally decomposed rate decreased obviously. The tensile strength and Young's modulus were also improved notably, which varied with MMT content, as well as the pH of gelatin matrix. Meanwhile, SEM photographs showed a plasticizing trend of gelatin fracture surface due to intercalation with MMT. Furthermore, the wet mechanical behavior was initially studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1189–1194, 2002  相似文献   

13.
General-purpose polystyrene (GPPS)/graphite flake composites with a segregated structure were fabricated by newly developed binder mixing method, aiming at highly thermally conductive polymer composites. The coefficient of thermal conductivity of the GPPS/graphite composites can be easily improved to be 3.5?W?m?1?k?1 at a graphite flakes loading of 24.7?vol%, showing an improvement of more than 2,000% compared with pure GPPS. The thermal conductivity of the composites increased with the increasing particle size of graphite flakes, while the mechanical properties of composites are decreased with the increasing particle size of GPPS resin particles.  相似文献   

14.
Novel nanocomposite films based on poly(ethylene-co-acrylic acid) (PEAA) and zinc montmorillonite (Zn2+–MMT) were fabricated using a solution casting method with water as the solvent. Transmission electron microscopy indicated that Zn2+–MMT was distributed finely in the PEAA matrix. X-ray diffraction indicated that an ion exchange process occurs between Zn2+–MMT and PEAA. The nanocomposites filled with a low Zn2+–MMT loading increased the tensile strength and elongation at break. The significant improvements in these mechanical properties were attributed to the fine dispersion of Zn2+–MMT in the polymer and the covalent interaction between the polymer chains and Zn2+ cations. Thermogravimetric analysis and differential thermal calorimetry confirmed that PEAA formed a network through the presence of Zn2+ cations. A poly(ethylene-co-acrylic acid) zinc salt (PEAAZn) film by hot pressing was introduced for comparison. Zn2+–MMT improved the mechanical properties of the PEAA significantly compared to that of PEAAZn.  相似文献   

15.
Natural rubber nanocomposites were produced by melt‐mixing of natural rubber with organically modified silicates. For comparison, a pristine‐layered silicate and a nonlayered version [English Indian clay (EIC)] were also included in the study. The layered silicate used was sodium bentonite (BNT) and organoclays used were octadecylamine‐ modified montmorillonite (MMT‐ODA) and methyltallow bis‐2‐hydroxyethyl ammonium‐modified montmorillonite (MMT‐ TMDA). Accelerated sulfur system was used for the vulcanization of the nanocomposites. The dispersion of these silicates was studied by X‐ray diffraction and transmission electron microscopy. The organoclay‐incorporated composites exhibited faster curing and improved mechanical properties. The improvement in the mechanical properties of the composites followed the order MMT‐ODA > MMT‐TMDA > EIC > BNT. The property improvement was attributed to the intercalation/exfoliation of the organically modified silicates because of their high initial interlayer distance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2537–2543, 2006  相似文献   

16.
In this paper, we report the study of the interactions between a poly(propylene-g-acrylic acid) and an oxidized aluminium surface by IR spectroscopy. A deposit of a pure poly(acrylic acid) on the same surface is used as a model. Under free acid form (COOH) we demonstrate the formation of hydrogen bondings between the acrylic carboxyl groups and OH functions located at the surface of alumina. This is characterized by an IR absorption [v(c?o)] at 1733 or 1743 cm?1 when we observe the metal surface either after peeling of a PPg(OH) film initially pressed on it or after a deposit of PAA(OH). Under the carboxylate form (COO?), we observe two modes of interaction, the one purely ionic between COO? and Al3+ with an absorption located near 1550 cm?1 and the other of complex form between COO? and Al3+ giving a band near 1610 cm?1. The water molecules can play a major part, in particular in the first case (COOH) where they destroy hydrogen bondings in favor of the formation of ? COO? groups, interacting with the metal surface according to ionic or complex modes as above. © 1993 John Wiley & Sons, Inc.  相似文献   

17.
In this work, we have prepared a new granule hydrogel composites of natural biocompatible polymeric chitosan and gelatin (C-G). The gelatin side groups (hydroxyl and carboxyl) can attach with amine groups of chitosan, which improve the interlink crosslinking in the final nanocomposites. The diameter of the granuls is around 3?mm to 6?mm. Furthermore, in order to reinforce the mechanical properties of granules, for the first time, octa(ammonium chloride) substituted Polyhedral Oligomeric Silsesquioxane (POSS-(NH3+Cl?)8) has been used as a nanofiller in the structure of this nanocomposite. The effect of POSS-(NH3+Cl?)8 on mechanical stability and swelling behavior of hydrogels has been investigated in three pH of 1.2, 7.4 and 9.5, respectively. Results demonstrate that the C-G/POSS-(NH3+Cl?)8 granules in acidic pH has the maximum swelling percent. The encapsulation efficiency (EE) values for C-G granules in three pH of 1.2, 7.4 and 9.5 are obtained 65%, 58% and 53% and for C-G/POSS-(NH3+Cl?)8 sample are 59%, 52% and 48%, respectively, which conform with the swelling behavior of these hydrogels. According to the obtained results from Metronidazole (MTZ) release, the as-synthesized hydrogels may have intrinsic ability in the controlled release of drugs. The as-prepared hydrogels are characterized via FT-IR, SEM, TGA and XRD analysis.  相似文献   

18.
ZrB2/SiC composite ceramics were fabricated to improve the electrical conductive properties of SiC matrix. The debinding and sintering temperatures were determined by computation of Gibbs free energy. As a result, all the samples have the relative density above 99%, and have excellent mechanical and electrical properties. The effects of ZrB2 content on the microstructure, mechanical and electrical properties were systematically studied. With increasing ZrB2 content, as-prepared composites show great improvement in their mechanical properties. Importantly, the introduction of ZrB2 weakened varistor nonlinear characteristic of composite and reduced its resistivity. The reason is the evolution of grain boundary in conductive paths. The sharp decrease of resistivity indicates the formation of percolation paths. The percolation threshold at 1?mA?cm?2 obtained via percolation model is 10.7963?vol% (19.7098?wt%) ZrB2. This value is much less than conventional composites, because the percolation path originates from grain boundary breakdown other than continuous conductor chains.  相似文献   

19.
A toughened, semiconductive polyaniline/polyurethane (PANI/PU)‐epoxy nanocomposite was prepared using a conductive polymer, PANI, and a PU prepolymer‐modified diglycidyl ether of bisphenol A (DGEBA) epoxy. The formation of a nanostructure was confirmed by Fourier transform infrared spectroscopy and SEM. The mechanical properties of the composites were evaluated and compared with those of the corresponding matrix. The improvement in impact strength of the composites (especially in the PANI/PU(PPG2000)‐epoxy system) was explained after fracture surface analysis using SEM. DSC and TGA studies indicated that the thermal properties of these composites were comparable to those of DGEBA epoxy. A conductivity in the range 10?9–10?3 S cm?1 was obtained, depending on the testing frequency (103–107 Hz) and the PANI content incorporated. Copyright © 2006 Society of Chemical Industry  相似文献   

20.
In this work, novel polyvinyl alcohol (PVA)/intercalated montmorillonite (MMT) nanocomposite foams were fabricated by melt extrusion with fixed amount of foaming agent, and the structure and properties were investigated with X‐ray diffraction, transmittance electron microscope, differential scanning calorimetry, plate rheometer, scanning electron microscope, density analysis, and mechanical testing in detail. The results revealed that pristine MMT could be intercalated by PVA during melt‐extrusion. Both exfoliation and intercalation structure was formed in the composites. The strong interaction between PVA and MMT restricted the motion of PVA molecules, leading to the enhanced complex viscosity, storage modulus, and melt flow index, suggesting the improved melt elasticity and melt strength. The improved melt strength of PVA through MMT incorporation facilitated the foaming process. With the increase of MMT, cell rupture was limited and the thickness of cell‐wall decreased, leading to the decreased density. The homogeneous cells and the closed cell structure with the foaming density of 0.35 g/cm3 could be formed with 2 wt % MMT incorporation. With the increase of MMT, the tensile strength of PVA/MMT foams decreased because of the enlarged foaming ratio and decreased density. This work aims to pave a simple and convenient way to produce biodegradable foams. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42706.  相似文献   

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