Herein, two nanoparticles with different dimensions, spherical carbon dots (C-dots) and sheetlike hectorite clay, were used as physical crosslinkers to fabricate C-dots-clay-poly(N-isopropylacrylamide)nanocompositehyd...Herein, two nanoparticles with different dimensions, spherical carbon dots (C-dots) and sheetlike hectorite clay, were used as physical crosslinkers to fabricate C-dots-clay-poly(N-isopropylacrylamide)nanocompositehydrogels (coded as C-dots-clay-PNIPAm hydrogels). The mechanical properties, fluorescence features and thermal-responsive properties of the C-dots-clay-PNIPAm hydrogels were evaluated. The experimental results indicate that synergistic effects of C-dots and hectorite clay nanoparticles are able to significantly enhance mechanical properties of the hydrogels. The hydrogels can be stretched up to 1730%with strength as high as 250 kPa when the C-dots concentration is 0.1wt%and the clay concentration is 6wt%. The hydrogels exhibit complete self-healing through autonomic reconstruction of crosslinked network a damaged interface. The hydrogels show favorable thermal-responsive properties with the volume phase transition around 34℃. In addition, the hydrogels are endowed with fluorescence features that are associated with C-dots in the hydrogels. It can be expected that the as-fabricated C-dots-clay-PNIPAm hydrogels are promising for applications in sensors, biomedical carriers and tissue engineering.展开更多
In this paper, a comparative study on the fracture toughness of woven glass fibre reinforced polypropylene, chopped glass fibre reinforced polypropylene and nanoclay filled polypropylene composites is presented. Nanoc...In this paper, a comparative study on the fracture toughness of woven glass fibre reinforced polypropylene, chopped glass fibre reinforced polypropylene and nanoclay filled polypropylene composites is presented. Nanoclays (Cloisite 15A) of 1 wt. % to 5 wt. % were filled in polypropylene (PP) matrix and they were subjected to fracture toughness stu-dies. The specimen with 5 wt. % nanoclay showed 1.75 times and 3 times improvement in critical stress intensity factor (KIC) and strain energy release rate (GIC), respectively, over virgin PP. On the other hand, 3 wt. % nanoclay PP composites showed superior crack containment properties. These structural changes of composite specimens were examined using Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) methods. It showed that exfoli-ated nanocomposite structures were formed up to 3 wt. % nanoclay, whereas, intercalated nanocomposite structures formed above 3 wt. % nanoclay in the PP matrix. Furthermore, the woven fibre reinforced PP composites demonstrated superior crack resistant properties than that of clay filled nanocomposites and chopped fibre PP composites. However, KIC and GIC values for woven fibre composites were lesser than that of chopped fibre composites. Moreover, KIC and GIC values for both nanoclay filled PP composites and woven fibre composites are comparable even though the clay filled PP demonstrated catastrophic failure. Also, the crack propagation rate of PP-nanoclay composites is comparable to that of chopped fibre composites.展开更多
A study of a typical intercalated structure of a thermotropic liquid crystalline polymer(TLCP)with organoclay was performed to elucidate the influence of intercalated organoclay on the TLCP molecules,especially on the...A study of a typical intercalated structure of a thermotropic liquid crystalline polymer(TLCP)with organoclay was performed to elucidate the influence of intercalated organoclay on the TLCP molecules,especially on their liquid crystallinity,thermal and rheological properties.The intercalated structures were confirmed in TLCP and organoclay formed molecular interactions with TLCP molecules in the system.Such intercalated structures caused the glass transition temperature of the nanocomposite to become invisible in thermal measurement and also caused loss of liquid crystallinity.The TLCP molecules inside the organoclay galleries showed higher thermal stability and transition temperatures,but the orderly structure of the TLCP molecules outside the galleries was destroyed by the organoclay,causing the TLCP to display lower thermal stability and transition temperatures than pristine TLCP.At 185℃,where TLCP is in the nematic phase,the nanocomposite had three orders of magnitude higher viscosity in the linear viscoelastic region than that of TLCP,with chain mobility and relaxation time slowed due to the intercalated effects in the nanocomposite.Steady shear altered the domain sizes and oriented the highly anisotropic organoclay layers or tactoids along the shear direction.展开更多
Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na+-montmorillonite (NMMT). Studies of XRD,SEM and TEM ind...Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na+-montmorillonite (NMMT). Studies of XRD,SEM and TEM indicated well-dispersed NMMT platelets in the films prepared. The ideal dispersity achieved was thought to be the result of aqueous compatibility between CEAR molecules and NMMT platelets and the result of the water-involved process as well. The modulus and strength of the polymer/clay nanocomposite coatings tested by tensile testing and nano-indentation were effectively improved compared to those of the virgin CEAR film. In addition,the adhesion strength,flexibility and water-resistance represented by Chinese national standard (GB) kept the best grades.展开更多
The interlayer surface of MgAl layered double hydroxide （MgAl-LDH） was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions （DS） to get MgAl（H-DS） LDH, and then the MgAl（...The interlayer surface of MgAl layered double hydroxide （MgAl-LDH） was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions （DS） to get MgAl（H-DS） LDH, and then the MgAl（H-DS） was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared （PTIR） spectroscopy, X-ray diffraction （XRD）, ion chromatography, transmission electron microscopy （TEM）, and thermogravimetry analysis （TGA）. The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of （001） XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 ℃ and a higher thermal stability above 370 ℃than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl（H-DS） can be 42 ℃ higher than that of LLDPE at 40% weight loss.展开更多
This paper focuses on the micromechanical study of the tensile property of Polymer-Clay Nanocomposites (PCN). Polypropylene (PP) filled with nanoclay is chosen as the PCN. Measurements of optical dispersion parameters...This paper focuses on the micromechanical study of the tensile property of Polymer-Clay Nanocomposites (PCN). Polypropylene (PP) filled with nanoclay is chosen as the PCN. Measurements of optical dispersion parameters (as discussed by Basu et al., namely, exfoliation number (ξn), degree of dispersions (χ) and agglomerate %) in PCN system were carried out using Transmission Electron Microscopy (TEM) and Optical Microscopy (OM). The experimentally obtained tensile modulus is compared with theoretically obtained modulus values from the optical dispersion parameters and observed a close matching between these values. Also, the tensile values are compared with other standard theoretical models and observed that the results obtained from optical dispersion parameters are suited well with experimental results.展开更多
The epoxy nanocomposites with similar amines （CH3（CH2）17NH2 and CH3（CH2）17N（CH3）301） treated montmorillonite clays have been investigated by wide-angle X-ray scattering, transmission electron microscopy （TEM...The epoxy nanocomposites with similar amines （CH3（CH2）17NH2 and CH3（CH2）17N（CH3）301） treated montmorillonite clays have been investigated by wide-angle X-ray scattering, transmission electron microscopy （TEM）, differential scanning calorimetry （DSC） and thermal gravimetric analysis （TGA）. Different nanocomposite structures, intercalation and exfoliation were formed by the reaction of octadecyltrimethylammonium chloride-exchanged and octadecylamine-exchanged clays with epoxy resin and phenalkamine as the curing agent, respectively. Results showed that the exfoliated nanocomposite can be obtained when octadecylamine with the lower polarity was used as a modifier. However, the intercalated nanocomposite can be obtained when octadecyltrimethylammonium chloride with higher polarity was used as a modifier.展开更多
Expanded graphite,prepared from the rapid heating of graphite intercalated compound,was blended with polystyrene via the intercalation and the in situ polymerization of styrene.SEM,STM and etc were used to characteriz...Expanded graphite,prepared from the rapid heating of graphite intercalated compound,was blended with polystyrene via the intercalation and the in situ polymerization of styrene.SEM,STM and etc were used to characterize the nanostructure of the expanded graphite the composite of polymer/expanded graphite,and the changes of the nanostructure during the rolling process.The graphite formed the nanostructure during the expanding process of the GIC.The nanosheets were confirmed to have been dispersed in polystyrene matrix with the thickness of 10～30 nm.The conductivity of PS/expanded graphite composite was sensitive to the rolling process.The intensive rolling caused great decrease in its conductivity,due to the destruction of conducting network.展开更多
A poly(methyl acrylate)(PMA)/ZnAl layered double hydroxide(ZnAl-LDH) intercalation nanocomposite is synthesized by in situ polymerization of methyl acrylate with ogano-modified ZnAl-LDH(O-ZnAl-LDH). Its structure and ...A poly(methyl acrylate)(PMA)/ZnAl layered double hydroxide(ZnAl-LDH) intercalation nanocomposite is synthesized by in situ polymerization of methyl acrylate with ogano-modified ZnAl-LDH(O-ZnAl-LDH). Its structure and morphology are confirmed by X-ray diffraction(XRD) and transmission electron microscopy(TEM) image. The d 001 of O-ZnAl-LDH is expanded to 2.85 nm after polymerization from 2.63 nm, which indicates the intercalation of PMA chains into the galleries of O-ZnAl-LDH. The (001) diffraction of PMA/ZnAl-LDH nanocomposite is broad due to the exfoliation of some O-ZnAl-LDH layers. The TEM image shows that the most of the layers of O-ZnAl-LDH are stacked with a distance of about 3 nm while some of them are exfoliated and dispersed disorderly in the PMA matrix.展开更多
基金the National Natural Science Foundation of China(Nos.51873167 and 50803048)the 2018 National College Students Innovation and Entrepreneurship Training Program Project Funding(No.20181049701035)。
文摘Herein, two nanoparticles with different dimensions, spherical carbon dots (C-dots) and sheetlike hectorite clay, were used as physical crosslinkers to fabricate C-dots-clay-poly(N-isopropylacrylamide)nanocompositehydrogels (coded as C-dots-clay-PNIPAm hydrogels). The mechanical properties, fluorescence features and thermal-responsive properties of the C-dots-clay-PNIPAm hydrogels were evaluated. The experimental results indicate that synergistic effects of C-dots and hectorite clay nanoparticles are able to significantly enhance mechanical properties of the hydrogels. The hydrogels can be stretched up to 1730%with strength as high as 250 kPa when the C-dots concentration is 0.1wt%and the clay concentration is 6wt%. The hydrogels exhibit complete self-healing through autonomic reconstruction of crosslinked network a damaged interface. The hydrogels show favorable thermal-responsive properties with the volume phase transition around 34℃. In addition, the hydrogels are endowed with fluorescence features that are associated with C-dots in the hydrogels. It can be expected that the as-fabricated C-dots-clay-PNIPAm hydrogels are promising for applications in sensors, biomedical carriers and tissue engineering.
文摘In this paper, a comparative study on the fracture toughness of woven glass fibre reinforced polypropylene, chopped glass fibre reinforced polypropylene and nanoclay filled polypropylene composites is presented. Nanoclays (Cloisite 15A) of 1 wt. % to 5 wt. % were filled in polypropylene (PP) matrix and they were subjected to fracture toughness stu-dies. The specimen with 5 wt. % nanoclay showed 1.75 times and 3 times improvement in critical stress intensity factor (KIC) and strain energy release rate (GIC), respectively, over virgin PP. On the other hand, 3 wt. % nanoclay PP composites showed superior crack containment properties. These structural changes of composite specimens were examined using Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) methods. It showed that exfoli-ated nanocomposite structures were formed up to 3 wt. % nanoclay, whereas, intercalated nanocomposite structures formed above 3 wt. % nanoclay in the PP matrix. Furthermore, the woven fibre reinforced PP composites demonstrated superior crack resistant properties than that of clay filled nanocomposites and chopped fibre PP composites. However, KIC and GIC values for woven fibre composites were lesser than that of chopped fibre composites. Moreover, KIC and GIC values for both nanoclay filled PP composites and woven fibre composites are comparable even though the clay filled PP demonstrated catastrophic failure. Also, the crack propagation rate of PP-nanoclay composites is comparable to that of chopped fibre composites.
基金funded by a grant from the Research Grant Council of Hong Kong,Grant No.HKUST6256/02.
文摘A study of a typical intercalated structure of a thermotropic liquid crystalline polymer(TLCP)with organoclay was performed to elucidate the influence of intercalated organoclay on the TLCP molecules,especially on their liquid crystallinity,thermal and rheological properties.The intercalated structures were confirmed in TLCP and organoclay formed molecular interactions with TLCP molecules in the system.Such intercalated structures caused the glass transition temperature of the nanocomposite to become invisible in thermal measurement and also caused loss of liquid crystallinity.The TLCP molecules inside the organoclay galleries showed higher thermal stability and transition temperatures,but the orderly structure of the TLCP molecules outside the galleries was destroyed by the organoclay,causing the TLCP to display lower thermal stability and transition temperatures than pristine TLCP.At 185℃,where TLCP is in the nematic phase,the nanocomposite had three orders of magnitude higher viscosity in the linear viscoelastic region than that of TLCP,with chain mobility and relaxation time slowed due to the intercalated effects in the nanocomposite.Steady shear altered the domain sizes and oriented the highly anisotropic organoclay layers or tactoids along the shear direction.
基金Supported by the National Natural Science Foundation of China (Grant No. 50572044)the 973 Project (Grant No. 2006CB605207-2)
文摘Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na+-montmorillonite (NMMT). Studies of XRD,SEM and TEM indicated well-dispersed NMMT platelets in the films prepared. The ideal dispersity achieved was thought to be the result of aqueous compatibility between CEAR molecules and NMMT platelets and the result of the water-involved process as well. The modulus and strength of the polymer/clay nanocomposite coatings tested by tensile testing and nano-indentation were effectively improved compared to those of the virgin CEAR film. In addition,the adhesion strength,flexibility and water-resistance represented by Chinese national standard (GB) kept the best grades.
基金Project supported by the National Natural Science Foundation of China （No. 50373039） and the National Key Basic Special Foundation （No. 2001CB409600） of China.
文摘The interlayer surface of MgAl layered double hydroxide （MgAl-LDH） was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions （DS） to get MgAl（H-DS） LDH, and then the MgAl（H-DS） was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared （PTIR） spectroscopy, X-ray diffraction （XRD）, ion chromatography, transmission electron microscopy （TEM）, and thermogravimetry analysis （TGA）. The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of （001） XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 ℃ and a higher thermal stability above 370 ℃than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl（H-DS） can be 42 ℃ higher than that of LLDPE at 40% weight loss.
文摘This paper focuses on the micromechanical study of the tensile property of Polymer-Clay Nanocomposites (PCN). Polypropylene (PP) filled with nanoclay is chosen as the PCN. Measurements of optical dispersion parameters (as discussed by Basu et al., namely, exfoliation number (ξn), degree of dispersions (χ) and agglomerate %) in PCN system were carried out using Transmission Electron Microscopy (TEM) and Optical Microscopy (OM). The experimentally obtained tensile modulus is compared with theoretically obtained modulus values from the optical dispersion parameters and observed a close matching between these values. Also, the tensile values are compared with other standard theoretical models and observed that the results obtained from optical dispersion parameters are suited well with experimental results.
基金support from the National Key Technology R&D Program(Grant No.2012BAB15B00)State Grid Practical Project-Investigation on the key technologies on developmentapplication of anticorrosive material of power transmission and transformation equipment(Grant No.521820130014)for supporting these studies
文摘The epoxy nanocomposites with similar amines （CH3（CH2）17NH2 and CH3（CH2）17N（CH3）301） treated montmorillonite clays have been investigated by wide-angle X-ray scattering, transmission electron microscopy （TEM）, differential scanning calorimetry （DSC） and thermal gravimetric analysis （TGA）. Different nanocomposite structures, intercalation and exfoliation were formed by the reaction of octadecyltrimethylammonium chloride-exchanged and octadecylamine-exchanged clays with epoxy resin and phenalkamine as the curing agent, respectively. Results showed that the exfoliated nanocomposite can be obtained when octadecylamine with the lower polarity was used as a modifier. However, the intercalated nanocomposite can be obtained when octadecyltrimethylammonium chloride with higher polarity was used as a modifier.
文摘Expanded graphite,prepared from the rapid heating of graphite intercalated compound,was blended with polystyrene via the intercalation and the in situ polymerization of styrene.SEM,STM and etc were used to characterize the nanostructure of the expanded graphite the composite of polymer/expanded graphite,and the changes of the nanostructure during the rolling process.The graphite formed the nanostructure during the expanding process of the GIC.The nanosheets were confirmed to have been dispersed in polystyrene matrix with the thickness of 10～30 nm.The conductivity of PS/expanded graphite composite was sensitive to the rolling process.The intensive rolling caused great decrease in its conductivity,due to the destruction of conducting network.
文摘A poly(methyl acrylate)(PMA)/ZnAl layered double hydroxide(ZnAl-LDH) intercalation nanocomposite is synthesized by in situ polymerization of methyl acrylate with ogano-modified ZnAl-LDH(O-ZnAl-LDH). Its structure and morphology are confirmed by X-ray diffraction(XRD) and transmission electron microscopy(TEM) image. The d 001 of O-ZnAl-LDH is expanded to 2.85 nm after polymerization from 2.63 nm, which indicates the intercalation of PMA chains into the galleries of O-ZnAl-LDH. The (001) diffraction of PMA/ZnAl-LDH nanocomposite is broad due to the exfoliation of some O-ZnAl-LDH layers. The TEM image shows that the most of the layers of O-ZnAl-LDH are stacked with a distance of about 3 nm while some of them are exfoliated and dispersed disorderly in the PMA matrix.
