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1.
Ethylene vinyl acetate (EVA‐45)/ethylene propylene diene terpolymer (EPDM) blend‐layered double hydroxide (LDH) nanocomposites have been prepared by solution blending of 1:1 weight ratio of EVA and EPDM with varying amounts of organo LDH (DS‐LDH). X‐ray diffraction and transmission electron microscopy analysis suggest the formation of partially exfoliated EVA/EPDM/DS‐LDH nanocomposites. Measurement of mechanical properties of the nanocomposites (3 wt% DS‐LDH content) show that the improvement in tensile strength and elongation at break are 35 and 12% higher than neat EVA/EPDM blends. Dynamic mechanical thermal analysis also shows that the storage modulus of the nanocomposites at glass transition temperature is higher compared to the pure blend. Such improvements in mechanical properties have been correlated in terms of fracture behavior of the nanocomposites using scanning electron microscopy analysis. Thermal stability of the prepared nanocomposites is substantially higher compared to neat EVA/EPDM blend, confirming the formation of high‐performance polymer nanocomposites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers  相似文献   

2.
The homogeneous dispersion of nanofillers in polymer matrices to form polymer nanocomposites remains a challenge in the development of high‐performance polymer materials for various applications. In the work reported, a stearate ion‐modified Mg? Al layered double hydroxide (St‐LDH) as nanofiller was incorporated in a silicone rubber (SR) matrix by solution intercalation and subsequently characterized. X‐ray diffraction and transmission electron microscopy studies confirm the formation of a predominantly exfoliated dispersion of St‐LDH layers of 75–100 nm in width and about 1–2 nm in thickness in the SR. Thermogravimetric analysis shows that the thermal degradation temperature of the exfoliated SR/St‐LDH (1 wt%) nanocomposites is about 80 °C higher than that of pure SR. Differential scanning calorimetric studies indicate that the melting and crystallization temperatures are higher by 4 and 10 °C for 5 and 8 wt% St‐LDH‐loaded SR nanocomposites compared to neat SR. A significant improvement of 97% in tensile strength and 714% in storage modulus and a reduction of 82% in oxygen permeability have been achieved at 3 wt% St‐LDH loading in SR. Copyright © 2011 Society of Chemical Industry  相似文献   

3.
Zn–Al–NO3–layered double hydroxide (Zn–Al–NO3–LDH) was prepared by the co-precipitation method at a constant pH of 7 and a ratio of Zn/Al = 4. A thermal treatment was performed for LDH at various temperatures. Powder XRD patterns showed that the layered structure of the LDH samples was stable below 200 °C, which was also confirmed by thermogravimetric (TGA) and differential thermal (DTA) analyses. Infrared spectra of the samples showed the characteristic peaks of LDH, and changes of these peaks were observed when thermal treatment was performed above 150 °C. Diffuse reflectance spectroscopy of the samples showed more than one energy gap at calcination temperatures below200 °C. In samples calcined at 200 °C and above only one energy gap was observed at approximately 3.3 eV. The photocatalytic activity was found to increase with the increase of the ZnO crystal size, which can be achieved by increasing the calcination temperature of the samples. Because of the presence of water molecules and anionic NO3 in the interlayer of the LDH, the dielectric response of the calcined LDH can be described by an anomalous low frequency dispersion using the second type of Universal Power Law for calcination temperatures below 200 °C. The dielectric response of the calcined LDH above 150 °C displays the dielectric relaxation behaviour of ZnO because of the formation of a ZnO phase in the LDH within this temperature range.  相似文献   

4.
The effects of different polypropylene (PP)‐g‐maleic anhydride polymers, used as compatibilizers, on the degree of exfoliation and co‐continuity of PP/ethylene‐propylene‐diene terpolymer (EPDM) thermoplastic elastomer (TPE)/clay nanocomposites were investigated. X‐ray diffraction and transmission electron microscopic micrographs showed that nanocomposites ranged from intercalated structure to a coexistence of intercalated tactoids and exfoliated layers. The observed significant increase in crystallization temperature (~20°C) could be beneficial for molding applications, because it means faster solidification and shorter cycle time. The rheological characteristic relaxation time of the compatibilizer correlated with the dispersion level in the nanocomposites. Solvent extraction and gravimetry measurements of continuity showed that compatibilizer affects the co‐continuity composition range through its effect on the dispersion level of nanoclays. At high EPDM concentration, the continuity of the thermoplastic phase for semi‐exfoliated TPE nanocomposites was higher than in the corresponding TPEs. Considering that TPE formation is the first step for thermoplastic vulcanizate production, where the thermoplastic phase should have a certain level of continuity, these results suggest that higher levels of EPDM could be incorporated into the semi‐exfoliated system before losing matrix continuity. It was also observed that there is a direct relation between the magnitude of the normalized stress growth viscosity overshoot and the continuity of TPE nanocomposites. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers  相似文献   

5.
3YTZP matrix composites containing 2.5 vol% of single‐walled carbon nanotubes (SWCNT) were fabricated by Spark Plasma Sintering (SPS) at 1250°C, following different processing routines with the aim of optimizing the SWCNTs dispersion throughout the ceramic matrix. Microstructural characterization of the as‐fabricated samples has been performed by means of scanning electron microscopy (SEM). The specimens have been crept at 1200°C to correlate creep resistance and SWCNTs distribution. There are no creep experimental results on these nanocomposites reported in literature. Mechanical results show that the incorporation of SWCNTs into a 3YTZP matrix produces an increase in the strain rate at high temperature with respect to monolithic zirconia. The creep resistance of these nanocomposites decreases with the improvement of the SWCNTs dispersion, where a smaller SWCNTs agglomerate size and consequently a higher concentration of carbon nanotubes surrounding the 3YTZP grain boundaries is found. This fact indicates that SWCNTs act as a lubricant making grain‐boundary sliding easier during deformation of these composites.  相似文献   

6.
Dynamically vulcanized thermoplastic elastomer (TPE) nanocomposites based on polypropylene (PP), ethylene‐propylene diene monomer (EPDM) and cloisite 15A were prepared via direct melt mixing in a co‐rotating twin‐screw extruder. The mixing process was carried out with optimized processing parameters (barrel temperature = 180°C; screw speed = 150 rpm; and feeding rate = 0.2 kg/hr). The formulation used to prepare the nanocomposites was fixed to 75/20/5 (PP/EPDM/Cloisite©15A), expressed in mass fraction. Effect of mixing sequence on the properties of vulcanized and unvulcanized (TPE) nanocomposites prepared under similar conditions was investigated using X‐ray diffraction (XRD) and a tensile testing machine. Results showed that the sequence of mixing does affect the properties of final TPE nanocomposites. Accordingly, nanocomposite samples prepared through mixing the preblended PP/clay masterbatch with EPDM phase, show better clay dispersion within the polymer matrix. J. VINYL ADDIT. TECHNOL., 22:320–325, 2016. © 2014 Society of Plastics Engineers  相似文献   

7.
Peroxide-cured metallocene polyethylene (mPE)/clay nanocomposites were prepared via melt mixing followed by hot press curing. The maleated compatibilizer, mPE grafted maleic anhydride (mPE-g-MA), was incorporated to improve the dispersion of various amounts of commercial organoclay (denoted as 20A). Experimental samples were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results indicated that there was an increase in dispersion with the addition of the compatibilizer. A measurable difference in the crystallization temperature, up to 9.5 °C, can be found for cured mPE reinforced with 5 phr clay in comparison cured mPE, indicating the promotion of crystallization kinetics through the addition of clay moiety. Taking 5 wt% loss as an index of thermal stability, the degradation temperature increased from 375.2 °C in cured mPE to 431.2 °C in the maleated 5 phr-loaded system, the highest improvement in all investigated cases. The Young’s Modulus and tear strength of maleated nanocomposites containing the compatibilizer at 9 phr clay content showed the highest values of up to 2 times increment compared those without clay, reflecting the increased interfacial interaction with the exploit of the compatibilizer.  相似文献   

8.
Pristine multiwalled carbon nanotubes (MWCNTs) along with the silane coupling agent were incorporated into ethylene propylene diene monomer (EPDM) rubber using dispersion kneader and two roller mixing mill to fabricate ablative nanocomposites used in hyperthermal environment encountered by space vehicle or rocket motor. The 1 wt% addition of MWCNTS in the rubber matrix has remarkably reduced the backface temperature elevation up to 40°C during the ablation testing of the ablatives. The linear and mass ablation resistances have been diminished up to 125% and 74%, respectively, while insulation indexes at 110°C backface temperature of the composite specimens have been elevated up to 51% with increasing the MWCNTS incorporation into the EPDM matrix. Thermal stability and heat absorbance capability of the polymer composites were progressed with increasing the filler to matrix ratio. Thermal conductivity/impedance of the ablatives have been conducted according to the ASTM E1225‐99 and D5470‐03, respectively to execute the effect of MWCNTs concentration on the thermal transport characteristics of the tested specimens. Tensile strength of the composite specimen was augmented up to 42% with increasing nanotubes to polymer ratio. Evenly dispersed MWCNTs in the polymer matrix, polymer pyrolysis, and voids formation in the ablated samples can be scrutinized in the scanning electron microscopy images. POLYM. ENG. SCI., 54:255–263, 2014. © 2013 Society of Plastics Engineers  相似文献   

9.
Monolithic 3YTZP and 3YTZP containing 2.5 vol% of single‐walled carbon nanotubes (SWCNT) were fabricated by Spark Plasma Sintering (SPS) at 1250°C. Microstructural characterization of the as‐fabricated 3YTZP/SWCNTs composite shows a homogeneous CNTs dispersion throughout the ceramic matrix. The specimens have been crept at temperatures between 1100°C and 1200°C in order to investigate the influence of the SWCNTs addition on high‐temperature deformation mechanisms in zirconia. Slightly higher stress exponent values are found for 3YTZP/SWCNTs nanocomposites (n~2.5) compared to monolithic 3YTZP (n~2.0). However, the activation energy in 3YTZP (Q = 715 ± 60 kJ/mol) experiences a reduction of about 25% by the addition of 2.5 vol% of SWCNTs (Q = 540 ± 40 kJ/mol). Scanning electron microscopy studies indicate that there is no microstructural evolution in crept specimens, and Raman spectroscopy measurements show that SWCNTs preserved their integrity during the creep tests. All these results seem to indicate that the high‐temperature deformation mechanism is grain‐boundary sliding (GBS) accommodated by grain‐boundary diffusion, which is influenced by yttrium segregation and the presence of SWCNTs at the grain boundary.  相似文献   

10.
The characterization, biocompatibility and hydrolytic degradation of poly(butylene adipate-co-terephthalate) (PBAT) and its nanocomposites based on 10 wt.% of an unmodified sepiolite and unmodified and modified montmorillonites and fluorohectorites were studied. All nanocomposites were prepared by melt blending using an internal mixer at 140 °C, showing a good level of clay distribution and dispersion into the PBAT matrix, especially those systems based on modified clays and sepiolite. The compression tests of all nanocomposites showed significant increases in the mechanical properties of PBAT matrix, associated to a reinforcement effect of nanoclays. An effective hydrolytic degradation of PBAT and nanocomposites in a phosphate buffered solution of pH 7.0 at 37 °C was also obtained. The addition of nanoparticles tended to delay slightly the hydrolysis of the polymer matrix in the early degradation stages; afterwards the presence of nanoparticles did not affect significantly the degradation trend of the polymer. Cytotoxicity tests, protein absorption analyses and complete blood count tests indicated that nanocomposites showed good biological safety: non-cytotoxicity, higher in vitro hemocompatibility than neat PBAT and non-negative hemostatic effects after contacting with blood. In general, these results showed that all the studied PBAT based nanocomposites could be very attractive for various tissue engineering applications, particularly to bone defects.  相似文献   

11.
Ethylene–propylene–diene terpolymer (EPDM)/silicone blend nanocomposites are prepared by solution method for the first time. EPDM and silicone rubber in their 50:50 (by weight) blend is intercalated within the silicate sheets of organically modified montmorillonite. Organic modification to the pristine sodium montmorillonite (Na‐MMT) surfaces is carried out by ion‐exchange reaction using hexadecyl ammonium chloride. The incorporation of such organic functional group makes Na‐MMT hydrophobic and expands the interlayer spacing between silicate sheets. The intercalated structure of EPDM/silicone blend nanocomposites is characterized by the X‐ray diffraction. Transmission electron microscopic characterization visualized the presence of both exfoliated and intercalated layered silicate in the polymer nanocomposites. The mechanical properties of the nanocomposites show a maximum improvement in tensile strength and elongation at break of 23 and 68%, respectively, compared with EPDM/silicone blend. The dielectric measurement demonstrates the increase in relative permittivity for the nanocomposite than the pure blend. The increase in the onset temperature of the thermal degradation of nanocomposites (∼52°C) corresponding to 1 wt% decomposition indicates the enhancement of thermal stability of (EPDM)/silicone blend due to interaction with silicates. POLYM. COMPOS., 35:1834–1841, 2014. © 2014 Society of Plastics Engineers  相似文献   

12.
Layered double hydroxide (LDH) is a new type of nanofiller, which improves the physicochemical properties of the polymer matrix. In this study, 1, 3, 5, and 8 wt % of dodecyl sulfate‐intercalated LDH (DS‐LDH) has been used as nanofiller to prepare a series of thermoplastic polyurethane (PU) nanocomposites by solution intercalation method. PU/DS‐LDH composites so formed have been characterized by X‐ray diffraction and transmission electron microscopy analysis which show that the DS‐LDH layers are exfoliated at lower filler (1 and 3 wt %) loading followed by intercalation at higher filler (8 wt %) loading. Mechanical properties of the nanocomposite with 3 wt % of DS‐LDH content shows 67% improvement in tensile strength compared to pristine PU, which has been correlated in terms of fracture behavior of the nanocomposites using scanning electron microscope analysis. Thermogravimetric analysis shows that the thermal stability of the nanocomposite with 3 wt % DS‐LDH content is ≈ 29°C higher than neat PU. Limiting oxygen index of the nanocomposites is also improved from 19 to 23% in neat PU and PU/8 wt% DS‐LDH nanocomposites, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

13.
The rubber nanocomposites containing ethylene vinyl acetate (EVA) having 60 wt % of vinyl acetate content and organomodified layered double hydroxide (DS‐LDH) as nanofiller have been prepared by solution intercalation method and characterized. The XRD and TEM analysis demonstrate the formation of completely exfoliated EVA/DS‐LDH nanocomposites for 1 wt % filler loading followed by partially exfoliated structure for 5–8 wt % of DS‐LDH content. EVA/DS‐LDH nanocomposites show improved mechanical properties such as tensile strength (TS) and elongation at break (EB) in comparison with neat EVA. The maximum value of TS (5.1 MPa) is noted for 3 wt % of DS‐LDH content with respect to TS value of pure EVA (2.6 MPa). The data from thermogravimetric analysis show the improvement in thermal stability of the nanocomposites by ≈15°C with respect to neat EVA. Limiting oxygen index measurements show that the nanocomposites act as good flame retardant materials. Swelling property analysis shows improved solvent resistance behavior of the nanocomposites (1, 3, and 5 wt % DS‐LDH content) compared with neat EVA‐60. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

14.
In this study, relatively large amounts of polypropylene (PP) and ethylene–propylene–diene (EPDM) were melt‐mixed with multiwalled carbon nanotubes (MWCNTs). Although the melt‐compounding method has many advantages, the uniform dispersion of carbon nanotubes in the polymer matrix is still the most challenging task. Because the electrical conductivity of composites is strongly influenced by the filler's state of dispersion and the extent of filler breakage during processing, the effects of the viscosity and processing conditions, such as the mixing time, rotor speed, and cooling rate, on the surface resistivity were studied. The PP/MWCNT nanocomposites displayed a high dependence of surface resistivity on the cooling rate, and the EPDM/MWCNT nanocomposites displayed a higher surface resistivity at the same content of MWCNTs and less dependence of surface resistivity on the cooling rate compared with PP/MWCNT nanocomposites. The increased surface resistivity of the EPDM/MWCNT nanocomposites was observed when EPDM with higher viscosity was used to prepare the EPDM/MWCNT nanocomposites. By increasing the rotor speed, lower surface resistivity was obtained in the PP/MWCNT nanocomposites. However, by increasing the rotor speed, a higher surface resistivity was obtained in the EPDM/MWCNT nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

15.
In this work, to inquire the impact of layered double hydroxide (LDH) nanoclay on functionalized poly(vinyl chloride) (PVC) through solution intercalation method, four kinds of nanocomposites were prepared. Mg-AL LDH and the obtained functionalize PVC composites were characterized through FT-IR, UV–Vis spectroscopy, TEM, XRD, contact angle, DSC, and UTM. Obtained results revealed that the functionalized PVC uniformly dispersed in the layer of LDH nanoclay. It is revealed that partially intercalated and disordered structure formed in PVC/LDH, PVC-TS (thiosulfate)/LDH, and PVC-S (sulfate)/LDH nanocomposites, whereas fully exfoliated structures formed in the PVC-TU (thiourea)/LDH nanocomposites. Further, it has been observed that the ultimate tensile strength for all the polymer nanocomposites enhanced with increased in the LDH content. These nanocomposites further exhibited higher thermal stability by at least by 51°C higher than the pristine PVC. Along with these, further it has been found that the functionalized PVC/LDH nanocomposites are proved to be effective as thermal stabilizer for PVC processing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48894.  相似文献   

16.
Multiwalled carbon nanotubes (MWCNTs) were dispersed and distributed via a co-rotating twin-screw extruder (TSE) in high (h)- and low (l)-molecular-weight amorphous and semicrystalline polylactides (PLAs) (aPLA and scPLA, respectively). Effects of PLA molecular weight and D-lactic acid equivalents content (D-content), as well as processing parameters, were examined on the MWCNT dispersion quality in PLA. The effectiveness of the MWCNT dispersion in various PLA matrices was investigated using scanning electron microscopy (SEM) and small-amplitude oscillatory and transient shear flow rheometry in the molten state. The results showed a better dispersion of MWCNTs in the low-molecular-weight PLA grades (aPLAl and scPLAl). In addition, better MWCNT dispersion was observed in aPLA grades when processed at a higher temperature of 190°C than at 150°C. At 150°C, while MWCNT bundles in aPLAl could be broken down, a good dispersion could not be achieved in aPLAh due to the lower molecular mobility at such a temperature. The electrical conductivity of the samples was also shown to increase as the MWCNT dispersion was improved. The existence of crystallites in scPLA-based nanocomposites, however, disrupted the connectivity of the MWCNTs and decreased the final electrical conductivity. The lower molecular weight aPLAl prepared at 190°C showed the highest electrical conductivity (~10−5 S/m) at a low loading of 0.5 wt.% MWCNTs.  相似文献   

17.
Talc-like filler with a layered structure having covalently bonded hexadecyl chain was synthesized and employed for the preparation of polyethylene nanocomposites. Thanks to the organic functionality, hexadecyl modified magnesium silicate melts at 44 °C and this peculiar property (characteristic) improves the dispersion of inorganic layers into the polymeric matrix. Transmission electron microscopy supports the formation of exfoliated polyethylene nanocomposites. The organo-modified talc greatly improves the stability on thermal oxidation of polyethylene.  相似文献   

18.
《Ceramics International》2020,46(15):23599-23610
High-energy ball milling was employed to prepare carbonated hydroxyapatite/silicon dioxide (CHA/SiO2) nanocomposites. Then, these nanocomposite powders were sintered at 900 and 1300 °C. XRD technique, FTIR spectroscopy and SEM were employed to examine the structure, molecular structure and microstructure of the sintered nanocomposites samples, respectively. Moreover, their mechanical properties were also measured. Furthermore, in vitro bioactivity and cytotoxicity of these nanocomposites were evaluated. The results indicated that the successive increases in SiO2 contents led to remarkable enhancement for densification behavior, mechanical properties and in vitro bioactivity of nanocomposites sintered at 900 °C. However, further increase in the sintering temperature to 1300 °C caused dramatic decreases in density and mechanical properties of nanocomposites. On the contrary, better bioactivity behavior was achieved. Amazingly, the obtained results revealed that the sample having the highest content of SiO2 and sintered at 900 °C had no toxic effects on bone-like cells while, that sintered at 1300 °C exhibited mild cytotoxicity. Based on the variations in the abovementioned properties, these nanocomposites can be used in different biomedical applications.  相似文献   

19.
A new synthetic route was applied to develop carbon nanofiber (CNF)–layered double hydroxide (LDH) hybrid through a noncovalent assembly using sodium dodecyl sulfate as bridging linker between magnesium–aluminum LDH and CNF and then characterized. Furthermore, this hybrid was used as nanofiller in thermoplastic polyurethane–acrylonitrile butadiene rubber (TN; 1:1 w/w) blend. Mechanical measurements showed that the 0.50 wt % hybrid loaded TN blend exhibited the maximum improvements in the elongation at break, tensile strength, and storage modulus of 1.51 times and 167 and 261% (25 °C), respectively. Differential scanning calorimetric analysis and thermogravimetric analysis showed maximum improvements in the melting temperature (5 °C), crystallization temperature (17 °C), and thermal stability (14 °C) in the 0.50 wt % surfactant modified carbon nanofiber–LDH loaded blend compared to the neat blend. Such enhancement in the properties of the TN nanocomposites could be attributed to the homogeneous dispersion, strong filler–blend interfacial interaction, and synergistic effect. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43470.  相似文献   

20.
Polyurethane acrylate (PUA) are widely used as coating for automobile industry. Making these coatings electrically conductive would open up new applications. Using thermally reduced graphene (TRG) and in-situ polymerization we have created PUA nanocomposites with an ultralow percolation concentration of 0.15 wt% (0.07 vol%) graphene. Urethane-acrylate oligomer (UAO) was synthesized and diluted by tripropyleneglycol diacrylate (TPGDA) to form flowable UAO/TPGDA mixture (UA). TRG was solvent-blended in UA to form uncured TRG/UA liquids and were polymerized by free radical polymerization with azobisisobutyronitrile (AIBN) initiator. Percolation concentrations of polymerized TRG/PUA nanocomposites occurred at 0.15 wt% (0.07 vol%), as determined by surface resistance measurements, bulk electrical conductivity, and modulus. TEM images revealed a homogeneous dispersion of TRG in PUA. Differential scanning calorimetry (DSC) was used to monitor the polymerization of TRG/UA uncured liquids and thermal properties of polymerized TRG/PUA nanocomposites. Polymerization heat, glass transition temperature, and polymerization temperature are independent of TRG loading, though polymerization temperature is ~10 °C lower in the absence of TRG.  相似文献   

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