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1.
Pristine and functionalized multi-walled carbon nanotubes (MWCNTs) filled poly(dimethyl siloxane) (PDMS) composites were produced by two different methods, namely the solution mixing method and the mini-extruder method. The composites produced using the mini-extruder exhibit relatively higher tensile strength and higher thermal conductivity due to better nanotubes dispersion. On the other hand, the composites prepared via solution mixing have higher electrical conductivity and better thermal stability due to the high aspect ratio of nanotubes. Scanning electron micrographs of composites fracture surface revealed that composites produced by mini-extruder resulted shorter nanotube length, thus lowering the aspect ratio of MWCNTs. In general, functionalization of nanotubes increases the tensile strength, thermal conductivity, and thermal stability of the PDMS composites due to the improved interfacial adhesion and nanotubes dispersion.  相似文献   

2.
Aqueous spherical colloidal silica (CS) particles with a diameter of 15 ± 5 nm were modified with three different types of monofunctional silane coupling agents to prepare functionalized colloidal silica (FCS) particles. The effects of the surface chemistry of the FCS were studied as a function of the CS/FCS loading in the poly(dimethyl siloxane) (PDMS) polymer. The prepared PDMS–CS/FCS composites were investigated for their physical properties both in the cured and uncured states. The extent of filler–filler and filler–polymer interactions was found to vary with the type of functionalizing agent used to treat the surface of the CS. The filler–filler interaction appeared to be predominant in the PDMS–CS composites, and improved filler–polymer interaction was indicated in the case of the PDMS–FCS composites. The composites containing CS treated with methyltrimethoxysilane exhibited relatively better optical and mechanical properties compared to the other PDMS–FCS composites. This study highlighted the importance of judiciously choosing functionalizing agents to achieve PDMS–FCS composites with predetermined optical and mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

3.
Silicon carbide was incorporated in poly(dimethyl siloxane) (PDMS) in combination with multiwall carbon nanotubes (MWCNTs) to improve the thermal conduction behavior. The amount of silicon carbide was increased from 0 to 150 phr and the amount of MWCNTs was increased from 0 to 8 phr at a fixed amount of silicon carbide (150 phr). The thermal conductivity of the PDMS composite was increased with increasing amount of the MWCNTs and fine dispersibility of the incorporated MWCNTs was achieved without pretreatment. The rheological properties of the PDMS composites incorporating silicon carbide and MWCNTs were investigated and the activation energy of the composites was calculated during thermal decomposition using the Horowitz‐Metzger method. Importantly, unexpected thermal decomposition behavior as indicated by the reduction in activation energy from 361.63 to 194.18 kJ mol?1, namely acceleration of decomposition of the PDMS matrix caused by MWCNTs, was observed for the first time. Copyright © 2011 Society of Chemical Industry  相似文献   

4.
Crosslinked poly(dimethyl siloxane) (PDMS) fibers were fabricated by electrospinning in combination with a sol–gel process followed by heat treatment. Before and after heat treatment, the changes in the chemical and thermal properties of the electrospun PDMS fibers were examined by differential scanning calorimetry (DSC), equilibrium swelling tests, and contact angle measurements. There was no significant change in morphology and average diameter of the as‐spun PDMS fibers after heat treatment. The tensile properties of the as‐spun PDMS fibers mat increased with increasing heat treatment temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

5.
In this study, a series of aqueous polyurethane modified by poly(dimethyl siloxane) PDMS were synthesized, which were based on polyoxytetramethylene glycol (PTMG), isophorone diisocyanate (IPDI), dimethylol propionic acid(DMPA), and PDMS. The copolymer was characterized by FTIR and the fraction of hydrogen bonded carbonyl group was determined through decomposition of C?O stretching. Energy dispersive X‐ray analyzer (EDX) was used to investigate the siloxane concentration on the surface and bulk regions. The morphology of aqueous polyurethane before and after modification was studied by SAXS, including the interface between soft and hard micro‐domain, the size and shape of the dispersive particles, as well as the degree of the phase separation. Influence on the morphology structure of aqueous polyurethane in different type and content of organic silicone was studied. It was shown that the degree of hydrogen bonding and phase separation of aqueous polyurethane decreased after the introduction the PDMS resulted from the migration of PDMS to the surface of the film. Therefore, water resistance improved a lot after the introduction of PDMS with different structures, and the tensile strength and elongation of APDMS(PDMS terminated by hydroxyalkyl) decreased while those of EPDMS(PDMS terminated by hydroxyl polyether) appeared little increase at low content and than decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

6.
The monolayer behavior of different end-functionalized poly(dimethyl siloxane)s (PDMSs) and a block copolymer, poly(dimethyl siloxane-co-ethylene oxide) (PDMS-co-EO) spread on an oligomeric poly(ethylene glycol) (PEG) substrates, were studied by means of electrocapillary wave diffraction (ECWD). Over a relatively small temperature range (40–70°C), the damping constant was more dependent on temperature than on the wave vector. Different surface layer properties were observed for two PDMS: one terminated with a methyl group (PDMS-CH3) and the one terminated with a hydroxy group (PDMS-OH). PDMS-OH showed a larger reduction in surface tension compared to PDMS-CH3 because of a higher interfacial affinity with PEG, which indicated that its monolayer surface activity was weaker. A lower surface elasticity of PDMS-OH than that of PDMS-CH3 supported that conclusion. The block copolymer showed no surface activity, since the short siloxane moiety did not repel the strong interaction between PEG and the ethylene oxide.  相似文献   

7.
Polyurethane composites filled with carbon fibers (CF) and carbon nanotubes (CNT) were prepared by mixing and injection molding, and its mechanical as well as their thermal properties were investigated. Dynamic mechanical analysis (DMA), thermogravimetry analysis (TGA), and thermal conductivity tests were done, and the properties were evaluated as a function of the filler concentration. The storage modulus of the composites increased with fillers concentration, which also mean the increase of the stiffness, suggest a good adhesion between the polyurethane matrix and the fillers. Addition of more CF and CNT to the composites broadened and lowered the peak of tan δ specifies that the polyurethane composite became more elastic because there is a good adhesion between the fillers and the matrix. The addition of carbon fillers improves the thermal stability of the polyurethane. The inclusions of CNT show a better thermal stability when compared with CF. The addition of carbon fillers also increased the thermal conductivity of the polyurethane composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

8.
We present a comparative study aiming at comprehending the effect of ultraviolet/ozone treatment on the modification of poly(dimethyl siloxane) (PDMS) and poly(vinylmethyl siloxane) (PVMS) silicone elastomers networks (SENs). Both PDMS and PVMS SENs undergo dramatic changes in their properties when exposed to UVO. The surface chemical composition of both PDMS and PVMS at long UVO treatment times changes substantially and features a high density of hydrophilic groups. There are two major differences in behavior in the two classes of materials. First, relative to PDMS, the PVMS-based SENs get modified throughout the entire bulk. Second, the physico-chemical changes detected in PVMS take place on much shorter time scale relative to PDMS. These results are in accord with our earlier reports that indicated that when exposed to UVO, the topmost ≈5 nm of PDMS gets converted into a silica-like material, which then acts as a barrier for diffusion of atomic oxygen. In this case, the bulk of PDMS maintains its elasticity. In contrast, both the surface and bulk of PVMS films undergo substantial changes in properties when exposed to UVO. First, the surface modification of PVMS SENs takes place after only a few seconds of the UVO treatment. In addition, we register substantial modification of bulk properties, including the complete densification accompanied with increased bulk modulus. Likely, the susceptibility of the vinyl bonds to radical reactions is responsible for this effect.  相似文献   

9.
We fabricated a piezoresistive composite using multi-walled carbon nanotubes (MWCNTs) as a conductive filler and polydimethylsiloxane (PDMS) as a polymer matrix, which operated in the extremely small pressure range required for finger-sensing. To achieve a homogeneous dispersion of MWCNTs in PDMS, the MWCNTs were modified by a polymer wrapping method using poly(3-hexylthiophene) (P3HT). The percolation threshold of the composites was significantly lowered by the presence of P3HT. The electrical conductivity and piezoresistive sensitivity of the composite were found to strongly depend on the P3HT concentration. The well-dispersed P3HT-MWCNT/PDMS composite showed good piezoresistive characteristics in the 0–0.12 MPa pressure range.  相似文献   

10.
Several types of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers (PMMA‐g‐PDMS) were synthesized using macromonomer technology. Three types of PMMA‐g‐PDMS with different PDMS chain length were obtained. The effect of siloxane chain length on surface segregation of PMMA‐g‐PDMS/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate)[P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended on the PDMS chain length, significantly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1736–1740, 2002  相似文献   

11.
Hexagonal boron nitride (h‐BN) fillers were first coated with low‐molecular‐weight polydimethylsiloxane (PDMS) by solution dispersion and then treated in argon plasma for different times. The modified h‐BN fillers were characterized by high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and contact angle analysis. The results revealed that a thin PDMS film several nanometers thick was tightly coated on the surface of the h‐BN filler after plasma treatment, and this thin film could not be removed by 48 h Soxhlet extraction with n‐hexane at 120°C. Furthermore, the effect of plasma modification on the h‐BN filled silicone rubber composites was investigated. The results indicated that the plasma modification improved the interfacial interaction between h‐BN and the matrix, but hardly affected the distribution state of the h‐BN in the composites. The composites filled with the modified h‐BN exhibit significantly higher thermal conductivity than the composites filled with untreated h‐BN. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers  相似文献   

12.
Well defined AB block copolymers of polystyrene (PS) and poly(dimethyl siloxane) (PDMS) have been prepared with PS molecular weights in the range 8 800 to 43 600 and PDMS molecular weights in the range 2 400 to 48 000. Provided the PS and PDMS molecular weights have a ratio within the range 0.5 to 4.0, these block copolymers stabilize particles of poly(methyl methacrylate) in n-alkanes. The particle size over the range 0.1 to 0.5 μm may be varied by performing dispersion polymerizations of methyl methacrylate as a function of monomer content of the seed stage and as a function of the concentration, molecular weight and composition of the block copolymer. From silicon analyses of the poly(methyl methacrylate) particles, values of the surface area stabilized per PDMS chain were established. The results indicate complete surface coverage of the particles.  相似文献   

13.
In this study, microstructural features, mechanical properties, and electrical conductivity behaviors of thermoplastic composites prepared by using of cyclic olefin copolymer (COC) as matrix and various types of carbon nano materials, expanded graphite (EG), carbon nanofiber (CNF), and multi walled carbon nanotubes (CNT) as conductive fillers were investigated. Effects of using of double and triple filler combinations on the electrical properties of composites were also quantified in detail by measuring the bulk resistance of samples under alternating current with an impedance spectrometer. The electrical percolation values of fillers were found to be 20, 10, and 5 phr for the series of composites prepared with the EG, CNF, and CNT, respectively. It was obtained that the bulk resistances of percolated samples were dramatically decreased from 1014 ohm.cm to 103?104 ohm.cm. On the other hand, it was also found that the using of double and triple filler combinations provided much lower (about 101 ohm.cm) bulk resistance which corresponded to higher conductivity values than the highly filled composites including of 30 and 40 phr of EG. Based on the DMA measurements and the quantifying of elastic modulus values of composites in the rubbery region, it was found that the reinforcing effects of carbon nano fillers on the elastic modulus of composites decreased in the order of CNT>CNF>EG, depending on the aspect ratio (Af) values of fillers into the matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42313.  相似文献   

14.
A novel amphiphilic hydrogel based on poly(2‐methyl‐2‐oxazoline)‐b‐poly(dimethyl siloxane) (PMeOx–PDMS) block copolymer was developed. First of all, PMeOx–PDMS macromonomer was synthesized by coupling mono‐hydroxylated PMeOx with PDMS followed by end‐capping with methacrylate group. The structures of each step were characterized by NMR and titration. After that, silicone hydrogels were prepared by UV‐initiated copolymerization of PMeOx–PDMS macromonomer with monomers such as 2‐hydroxyethyl methacrylate in the presence of a crosslinker. Measurements of the hydrogels' water contact angle, equilibrium water content, and tensile properties showed that the hydrogels possessed better hydrophilic surface, higher water content, and better ion permeability with the increase of the content of the macromonomer PMeOx–PDMS. Meanwhile, the tensile strength and Young's modulus of the hydrogels decreased slightly. Protein adsorption tests showed that the hydrogels had strong antifouling ability after the incorporation of PMeOx. This newly described hydrogel demonstrated attractive properties to serve as ophthalmic biomaterial. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39867.  相似文献   

15.
This work reports on some results of research conducted on composite materials consisting of a butadiene–styrene (SBS) thermoplastic elastomer matrix filled with short carbon fibres previously subjected to oxidative treatment to increase the surface functionality. Scanning electron microscopy confirms the existence of interactions between the matrix and the fibre, which are not observed for commercial fibre fillers and which translate into mechanical strength increments, in terms of the Young’s modulus, tensile and tear strengths for the oxidized fibre composites. The stress–strain curves of the composites show yield point phenomena as strain is applied longitudinally to the main fibre orientation. In oxidized fibre composites the stress and strain coordinates are a function of the degree of oxidation (greater strain for more strongly oxidized fibre) and fibre strength (lower stress for longer treatment times). © 1997 SCI.  相似文献   

16.
ABSTRACT: In the present paper, we describe a new and original method to obtain transparent, siloxane-based composites, with high refractive index (up to 1.68). The method is based on the decomposition of Zn-siloxane, mixed with a poly-(dimethyl)-block-(phenyl)siloxane matrix in different ratios. It was found that after treatment of such mixed metal-containing polymer blend with H2S, the nanoparticles of ZnS are formed, with the size in a 1- to 5-nm range, which allow effective increase of the refractive index of the nanocomposite mixture with poly-(dimethyl)-block-(phenyl)siloxane without loss of film transparency. We succeded to increase the refractive index from 1.54 (pure matrix) up to 1.68 (composite with a ZnS content of 4.6 vol.%). The siloxane-based compositions are optically transparent, which makes it possible to use them as light-emitting diodes or solar cell sealants or adhesives.  相似文献   

17.
Multiwall carbon nanotube elastomeric composites: A review   总被引:3,自引:0,他引:3  
Nanostructured materials gained great importance in the past decade on account of their wide range of potential applications in many areas. A large interest is devoted to carbon nanotubes that exhibit exceptional electrical and mechanical properties and can therefore be used for the development of a new generation of composite materials. Nevertheless, poor dispersion and poor interfacial bonding limit the full utilization of carbon nanotubes for reinforcing polymeric media.In this paper, recent advances on carbon nanotubes and their composites will be presented through results of the author's research, essentially based on filled elastomeric networks. The intrinsic potential of carbon nanotubes as reinforcing filler in elastomeric materials will be demonstrated. It will be shown that, despite a poor dispersion, small filler loadings improve substantially the mechanical and electrical behaviors of the soft matrix. With the addition of 1 phr of multiwall carbon nanotubes in a styrene-butadiene copolymer, a 45% increase in modulus and a 70% increase in the tensile length are achieved. Straining effects investigated by atomic force microscopy and infrared and Raman spectroscopies, provide interesting results for the understanding of the mechanical behavior of these nanotube-based composites. All the experimental data lead to the belief that the orientation of the nanotubes plays a major role in the mechanical reinforcement. The strong restriction in equilibrium swelling in toluene with the MWNT content is not ascribed to filler-matrix interfacial interactions but to the occlusion of rubber into the aggregates. On the other hand, carbon nanotubes impart conductivity to the insulator matrix. Between 2 and 4 phr, the conductivity increases by five orders of magnitude reflecting the formation of a percolating network. Changes in resistivity under uniaxial extension completed by AFM observations of stretched composites bring new insights into the properties of these composites by highlighting the contribution of orientational effects.  相似文献   

18.
Multiblock copolymers consisting of poly(l ‐lactic acid) and poly(dimethyl siloxane) were prepared by the polycondensation of oligo(l ‐lactic acid) (OLLA) with dihydroxyl‐terminated oligo(dimethyl siloxane) and dicarboxyl‐terminated oligo(dimethyl siloxane). Copolymers with number‐average molecular weights of 18,000?33,000 Da and various content ratios of oligo(dimethyl siloxane) (ODMS) unit were obtained by changing the feed ratio of these oligomers. A film prepared from the copolymer with an ODMS content ratio of 0.37 exhibited two independent peaks at ?107°C and 37°C in the mechanical loss tangent for temperature dependence, suggesting the formation of microphase separation between the OLLA and ODMS segments. The film had a tensile strength of 3.2 MPa and a high elongation of 132%. The film also exhibited a high strain recovery even after repeated straining. The incorporation of dimethyl siloxane units as multiblock segments was confirmed to improve the flexibility of poly(l ‐lactic acid). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40211.  相似文献   

19.
X-ray photoelectron spectroscopy is used to study the surface segregation of siloxane in dilute blends of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers in poly(vinyl chloride)(PVC). The graft copolymers are found to be extremely efficient surface modifiers, which form, when added in amounts of 0.5% or more, a continuous siloxane overlayer on the surface of PVC. © 1995 John Wiley & Sons, Inc.  相似文献   

20.
采用一定粘度的聚二甲基硅氧烷为基体,加入适量填料和助剂,成功制备了室温硫化硅橡胶涂层。研究了气相法SiO2和交联剂对涂层材料的影响,并进行了TG和SEM测试。研究结果表明:填料的添加明显改善了涂层的力学性能和耐高温性能,拉伸强度迭1.42MPa,可耐温288℃;并且该涂层有较好的耐水和耐酸、盐性能,耐碱性能有待进一步改善。  相似文献   

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