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1.
The role of nanoclays and TiO2 nanoparticle loadings were investigated on low density polyethylene crystalline structure, in addition to studying packaging film properties such as barrier, thermal and mechanical properties. The polymer crystal study indicated for the orthorhombic crystal phase and about 20% lower degree of crystallinity for nanocomposites containing more than 2 wt.% TiO2 nanoparticles. Based on the X-ray diffraction technique, the dispersion of nanoclays was improved to almost good degree of clay exfoliation with the company of 4 wt.% TiO2 nanoparticles. In agreement with XRD results, the TEM morphological studies mainly suggest that TiO2 has a helpful effect on nanoclay exfoliation. The increase in degradation temperature of nanocomposites may be attributed to the formation of inorganic char on polymer melt. The barrier properties of TiO2/clay nanocomposite packaging films depend mainly on nanoclay loading with an unclear trend from TiO2 nanoparticles. The increase in elastic modulus and the yield stress of nanocomposite films showed great effects on film mechanical properties by nanoclays.  相似文献   

2.
Mixtures of tetrahydrofuran (THF) and carbon dioxide (CO2) were identified as new solvent systems for polysulfone. The miscibility and density of polysulfone in binary fluid mixtures of THF and CO2 were investigated from 300 to 425 K at pressures up to 70 MPa. The influence of the CO2 and polysulfone concentrations was studied, with the concentrations of the other two components kept constant. At a 4.5 wt % polymer concentration, the demixing pressures in a 10 wt % CO2 and 90 wt % THF mixture increased with temperature (310–425 K) from 15 to 40 MPa. With increasing CO2 concentration (from ca. 10 to 14 wt %), a significant increase (from 15 to 70 MPa at 310 K) was observed in the demixing pressures. Furthermore, with an increasing amount of CO2, the nature of the phase boundary shifted from lower critical solution temperature behavior to upper critical solution temperature behavior. The influence of the polymer concentration was studied in the 0–5 wt % range at two CO2 levels, with solvent compositions of 10 wt % CO2 and 90 wt % THF and 13 wt % CO2 and 87 wt % THF. The system with a higher level of CO2 (13 wt %) showed highly unusual phase behavior: on pressure–composition and temperature–composition diagrams, the system displayed two distinct regions of miscibility. In the system with 10 wt % CO2, the distinct regions of miscibility that were observed in the system with 13 wt % CO2 partially overlapped and led to a W‐shape phase boundary. The densities of the polymer solutions were measured from the one‐phase region through the demixing point into the two‐phase region at a constant temperature. No significant change in density was found around the phase boundary; this indicated that the coexisting phases had similar densities, as is often the case with liquid–liquid phase separation in polymer solutions under high pressure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2357–2362, 2002  相似文献   

3.
In order to investigate whether the particle sizes of inorganic additives in polymer have an influence on the flame‐retardant and other properties of the polymer, five types of Mg3Al–CO3 layered double hydroxide (LDHs) with particle diameters of 80–100, 200–350, 500–550, 550–600, and 700–900 nm were synthesized using a hydrothermal method. The obtained Mg3Al–CO3 LDHs were treated using the aqueous miscible organic solvent treatment method to give highly dispersed platelets in Polypropylene (PP). The thermal stability, flame retardancy, and mechanical properties of the PP/AMO–LDH nanocomposites were investigated systematically. The results showed that the thermal stability and flame retardancy of PP could be improved after incorporating AMO–LDHs. The temperature at 50% weight loss (T0.5) of PP/LDH (700–900 nm) nanocomposites with a LDH loading of 15 wt % was increased by 57 °C. When the LDHs loading was 40 wt %, the peak heat release rate (PHRR) of the PP/LDH nanocomposites with small LDHs particle sizes (<350 nm) was decreased by ca. 58%. The limiting oxygen index was increased by 5% for PP/LDH (80–100 nm) nanocomposites. The response surface regression results also indicated that both LDH particle size and loading have influence on PHRR, heat release capacity, tensile strength, and elongation at break. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46204.  相似文献   

4.
Translucent AlN ceramics with 0‐2 wt.% MgF2 additive were prepared by spark plasma sintering. AlN powder was heated temporarily up to 2000°C, before holding at 1850°C for 20 minutes in N2 gas. The sintered ceramics consisted of a single phase of hexagonal AlN, and showed a transgranular fracture mode. The total transmittance was improved remarkably by the additive, to reach 74% at a wavelength of 800 nm for 1 wt.% MgF2. For 2 wt.% MgF2, the transmittance was slightly lower than that for 1 wt.% MgF2, and an absorption band was observed apparently at around 400 nm. The addition of MgF2 along with the temporary heating at higher temperatures than the sintering temperature contributed to improve the transmittance remarkably.  相似文献   

5.
Layered double hydroxide (LDH) containing different metal constituents (Zn, Co, and Ni) was intercalated with different organic anions and has been used as fillers in low-density polyethylene (LDPE), and its thermal and flammability behavior was evaluated. The best thermal stability (∆T0.5 = 21 °C) was obtained with the LDPE-Ni/Al-dodecyl sulfate (4 wt %) nanocomposite. Addition of hydrophobic LDHs systematically decreases the enthalpy of melting and crystallization compared to the neat polymer. In LDPE-Co/Al-dodecyl sulfate (2 wt %) nanocomposite, the melting and crystallization enthalpies declined by about 45 J/g, indicating a good interaction of the filler with the polymer matrix. A reduction of 20% of the flammability for the LDPE-Ni/Al-stearate (4 wt %) nanocomposite was obtained. On the other hand, Zn–Co LDH as filler in LDPE nanocomposite did not affect effectively the same property. In an innovative study, results indicate that different metal constituents and interlayer anion of LDH as filler can change thermal and flammability properties of the polymer nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48737.  相似文献   

6.
A novel polymer membrane with nanosized pore structures has been prepared from the direct copolymerization of acrylonitrile (AN) with a polymerizable nonionic surfactant in water‐in‐oil (w/o) or bicontinuous microemulsions. This polymerizable surfactant is ω‐methoxy poly(ethylene oxide)40 undecyl‐α‐methacrylate macromonomer [CH3O (CH2CH2O)40 (CH2)11 OCO(CH3)CCH2, abbreviated: C1‐PEO‐C11‐MA‐40]. Besides PEO macromonomer, AN, and crosslinker ethyleneglycol dimethacrylate, the microemulsion system contained varying amount of water that formed w/o microemulsions having water droplet structures and bicontinuous microemulsions consisting of interconnected water channel. The polymerized membranes prepared in this study have pore radii ranging from 0.38 to 2.4 nm as evaluated by PEG filtration. The pore size appears to vary linearly with water content in precursor microemulsions. But a sharp change in the gradient of the linear relationship is observed around 25 wt % water content. Membranes made from bicontinuous (>25 wt % water) microemulsion polymerization have a larger and interconnected (open‐cell) nanostructures. In contrast, much smaller closed‐cell (disinterconnected) nanostructures were obtained from w/o (<25 wt % water) microemulsion polymerization and the membrane exhibited a permselectivity toward water in pervaporation separation of high ethanol (>50 wt %) aqueous solutions. The separation factor (α) for 95% ethanol aqueous solution by the membrane derived from the microemulsion containing 10 wt % water is about 20. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2785–2794, 2000  相似文献   

7.
Nano-sized silica/polysulfone (PSf) flat sheet asymmetric MMMs with high CO2 permeance for CO2/N2 separation were fabricated by dry/wet phase inversion method using N, N-dimethylacetamide (DMAc) and tetrahydrofuran (THF) as solvents and ethanol as additives. The results indicated that the addition of nano-silica on the polymer matrix resulted on reduced membrane performance due to void formation and particle agglomeration. Optimum membrane performance was obtained at the following fabrication parameters: 22 wt.% PSf, 31.8 wt.% DMAc, 31.8 wt.% THF, 14.4 wt.% ethanol, 20 s evaporation time, and 0 wt.% silica loading, with CO2/N2 selectivity of 15.6 and CO2 permeance of 14.2 GPU.  相似文献   

8.
The aim of this study is to investigate the effect nanosilica and nanoalumina has on nanoparticle release from industrial nanocomposites due to drilling for hazard reduction whilst simultaneously obtaining the necessary mechanical performance. This study is therefore specifically designed such that all background noise is eliminated in the measurements range of 0.01 particles/cm3 and ±10% at 106 particles/cm3. The impact nano-sized SiO2 and Al2O3 reinforced polyester has on nanoparticle aerosols generated due to drilling is investigated. Real-time measurement was conducted within a specially designed controlled test chamber using a condensation particle counter (CPC) and a scanning mobility particle sizer spectrometer (SMPS). The results show that the polyester nanocomposite samples displayed statistically significant differences and an increase in nanoparticle number concentration by up to 228% compared to virgin polyester. It is shown that the nanofillers adhered to the polyester matrix showing a higher concentration of larger particles released (between 20 – 100 nm). The increase in nanoparticle reinforcement weight concentration and resulting nanoparticle release vary considerably between the nanosilica and nanoalumina samples due to the nanofillers presence. This study indicates a future opportunity to safer by design strategy that reduces number of particles released concentration and sizes without compromising desired mechanical properties for engineered polymers and composites.

© 2017 American Association for Aerosol Research  相似文献   


9.
Nanoparticles of stabilized ZrO2 in a single cubic phase by 5–20 at.% (of total metal cations) Cr3+/Cr4+ addition are obtained through a chemical method using a polymer matrix made of sucrose and polyvinyl alcohol. On heating at 250–900 °C in air, the polymer network decomposes and burns out leaving behind a dispersed microstructure in 10–25 nm diameter particles of cubic ZrO2 in spherical shape. A modified microstructure comprises of 10–14 nm crystallites of dispersed tetragonal phase, or both tetragonal and monoclinic phases, in cubic phase appear on a prolong (2 h or larger) heating of precursor at 900–950 °C. Particles in tetragonal ZrO2 are in acicular shape, while the monoclinic phase is in the shape of platelets. The Cr3+/Cr4+ additive facilitates formation of cubic phase in small particles on a controlled decomposition and combustion of precursor. It stabilizes small particles by inhibiting their growth by forming a thin amorphous surface layer over them.  相似文献   

10.
Ultrafine dry powder coating technology creates biocompatible polymeric coatings for implants. Nanoparticles (nTiO2) modify flow to prevent agglomeration and create homogenous coatings. Since polyester‐based coatings require the potentially harmful 1,3,5‐triglycidyl isocyanurate (TGIC) curing agent, this study's objective was to develop alternative TGIC‐free formulations. Epoxy and epoxy/polyester (1:1) hybrid mixtures were enriched with CaO (5% w/w) and nTiO2 (0.5% w/w), as functional additives and flow modifiers, respectively. Epoxy‐TiO2 and Hybrid‐TiO2 mixtures were prepared with micron‐sized TiO2 (25% w/w) to enhance biocompatibility. Polymer chips and additives were combined in a high‐shear mixer and passed through a sieve (35 µm) to yield ultrafine particles that were sprayed (20 kV) onto metal sheets and cured (200 °C). Particle size analyses showed that all formulations were ultrafine (D 0.5 < 35 µm), and epoxy/polyester/TiO2 mixtures were the smallest (D 0.5 = 16.34 µm). Angles of repose, avalanche and resting indicated reduced flowability when epoxy was enriched with TiO2 and/or polyester, although all formulae were highly flowable. Elemental mapping of coatings showed a predominance of carbon (C) and oxygen (O) from resin polymer, and elevated titanium (Ti) in the TiO2 enriched surfaces. However, calcium (Ca) clusters were higher on the epoxy/polyester Hybrid coatings. Optical microscopy showed human mesenchymal cells (ATCC CRL‐1486) attached and spread out, and Alizarin Red staining showed mineral deposits in 2–4 week cultures, particularly on epoxy/polyester/TiO2 Hybrid surfaces. These epoxy resin‐based formulations were effective TGIC‐free substitutes for ultrafine dry powder coatings on implants. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43960.  相似文献   

11.
Dispersion and exfoliation of single wall carbon nanotubes (SWNTs) have been studied in poly(acrylonitrile) (PAN), poly(p‐phenylene benzobisoxazole) (PBO) solutions, and composite fibers using transmission electron microscopy. As a result of polymer assisted dispersion and exfoliation, the average SWNT bundle diameter in SWNT/PAN (5/95) was 11 nm, while the average diameter for the pristine SWNT bundles was about 30 nm. High resolution TEM of SWNT/PBO (10/90) composite fibers did not reveal the presence of SWNT aggregates or bundles, suggesting SWNT exfoliation as individuals. On the other hand, both oriented and unoriented nanotube bundles have been observed in SWNT/PBO samples containing 15 wt % nanotubes. Carbon nanotubes are 105 times more radiation resistant than flexible polymers such as polyethylene, and 103 times more resistant than highly radiation resistant polymers such as PBO. Therefore in the high resolution TEM study of nanotube/polymer composites, nanotubes can be observed long after the polymer has been damaged by electron radiation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 985–989, 2005  相似文献   

12.
The effect of nanoparticles on nonisothermal polymer crystallization was investigated using poly(ethylene terephthalate) (PET) nanocomposites with alumina (Al2O3) nanoparticles of average size 38 nm. The filler content in the nanocomposites was varied from 0 to 10 wt %. The interparticle spacing was observed to decrease (as expected) with an increase in loading of the nanoparticles. Contrary to previous reports in the literature on semicrystalline polymer‐based composites with micron‐size and macroscale particles, our differential scanning calorimetry, transmission electron microscopy, and X‐ray studies showed that the addition of the nanoparticles did not cause heterogeneous nucleation of PET crystals in nanocomposites containing up to 3 wt % Al2O3. This is attributed to the nanoparticle curvature being comparable to the radius of gyration of the polymer. The addition of the nanoparticles was found to disrupt the spherulitic morphology of the PET because of their physical presence and their proximity to one another. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

13.
In this study, the polyethylene oxide (PEO)/SiO2 nanoparticles (NPs) nanocomposite films with various SiO2 NPs concentrations were prepared using an in situ formation of NPs in the polymer matrix for self-cleaning antireflected surface applications. The effect of SiO2 NPs in PEO/SiO2 NPs nanocomposite films on the structural, morphological, chemical, thermal, optical, and electrical properties of PEO/SiO2 NPs nanocomposite films was performed. According to the x-ray diffraction and the differential scanning calorimetry analysis, the crystallinity degree of the nanocomposite films decreases by increasing the SiO2 NPs concentrations. The bandgap energy of PEO/SiO2 NPs nanocomposite films decreases from 3.95 to 3.55 eV as the SiO2 NPs concentration increases up to 10 wt.%. The average electrical conductivity of the PEO/SiO2 NPs nanocomposite films increases from 5.1 × 10−7 to 2.0 × 10−6 S/cm as the SiO2 NPs concentration increases up to 10 wt.%. The refractive index decreases to 1.64 at 550 nm for the PEO/SiO2 NPs nanocomposite films with 10 wt.% of SiO2 NPs, and the water contact angle decreases to around 0° after thermal treatment, which confirms that the PEO/SiO2 NPs nanocomposite films can be used as self-cleaning antireflected surfaces.  相似文献   

14.
The synthesis of poly(ethylene terephthalate) (PET)/layered double hydroxide (LDH) nanocomposites through microwave methods has been investigated. To enhance the compatibility between the PET polymer and the LDH, dodecyl sulfate was intercalated in the lamellar structure. The organo‐LDH structure was confirmed by powder X‐ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR). PET nanocomposites were prepared with 0–10 wt % of LDH content by in situ microwave‐assisted polymerization. PXRD was used to detect the formation of the exfoliated PET/LDH nanocomposites. Transmission electron microscopy was used to observe the dispersed layers and to confirm the exfoliation process. FTIR spectroscopy confirmed that the polymerization process had occurred. TG and DTA are used to study changes in thermal stability of the nanocomposites, which resulted enhanced by well dispersed LDHs layers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

15.
The vitrification line for the ternary system of polysulfone (PSf)/N‐methyl‐2‐pyrrolidinone (NMP)/water was determined by differential scanning calorimeter (DSC) measurements with varying compositions. Pure PSf showed both α‐ and β‐transition temperatures (Tg = 187.5°C, Tg = −21.4°C). The Tg of PSf decreased with increasing solvent concentration. The Tg of PSf decreased linearly with the addition of NMP in the concentration range of 70–90 wt % polymer. The vitrification line was indicated in the phase diagram for the ternary system of PSf/NMP/water at 15 and 60°C. As the temperature is increased, a high polymer concentration was needed to reach the vitrification condition. The vitrification composition of the polymer in the binary system of PSf and NMP was 72.0 wt % at 15°C and 79.8 wt % at 60°C. We also found that the slope of the vitrification line changed with the temperature and that a small amount of water (10–20 wt %) can induce the vitrification of the polymer solution in the PSf/NMP/water system at 15°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 431–438, 1999  相似文献   

16.
Blends of polycaprolactone (PCL)/gelatinized starch and polybutylene succinate adipate/gelatinized starch have been prepared in various ratios and their phase morphology and thermal/mechanical properties have been analyzed. For both the PCL/plasticized starch and polybutylene succinate adipate/plasticized starch blends the resistance to impact increased with increasing polyester content, and the tensile modulus reached a maximum at around 80 wt % polyester content. In blends containing up to 70 wt % polyester (as observed by scanning electron microscopy) a hierarchical dispersion of the gelatinized starch phase was observed (distinct domain sizes of those less than 5 μm and those greater than 15 μm) and in the blends containing 70–90 wt % polyester a more singular dispersed phase of gelatinized starch was observed within the polyester matrix. Dynamical mechanical analysis results showed some phase mixing was present in the PCL/gelatinized starch blends noted by the appearance of an additional tan δ peak located between the glass transition temperatures of the respective components and broadening of the low temperature transition corresponding to the Tg of the polyester (possibly the result of a starch‐rich polyester phase) with some overlap with the low temperature β transition of the gelatinized starch itself. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 802–811, 2007  相似文献   

17.
The introduction of polyhedral oligomeric silsesquioxane (POSS) particles which act as heterogeneous nucleation agent was applied to improve the cellular morphology of nanocellular polyetherimide (PEI) foams. The loading of POSS particles increases the solubility and diffusivity characteristics of gases in nanocomposite sheets by changing the distribution of the free volume and enlarging the unoccupied volume in polymer matrix. When the range of content of POSS particles is 0.2?~?1.0 wt. %, the range of the calculated surface tension of PEI/scCO2 (γ mix ) and radius of the critical nucleus (r*) are 30.98?~?28.14 mN/m, and 6.88?~?6.25 nm, respectively. However, the small aggregated POSS particles are favour of heterogeneous nucleation bacause the actual diameter of the aggregated POSS particles is approximate to twice r*, so the addtion of 0.5 wt. % POSS to PEI matrix presents excellent heterogeneous nucleation performance for foaming. The average cell size of 0.5 wt. % POSS/PEI nanofoams compared with neat PEI decreases from 108 to 66 nm and the cell density increses from 5.96?×?1014 to 3.34?×?1015 cells/cm3.  相似文献   

18.
Nanocomposites of poly(vinyl alcohol) (PVA) with Mg‐Al layered double hydroxides (LDHs) were prepared with different compositions, viz., 2, 4, 6, and 8 wt %, of LDH, by solution‐intercalation method. The effect of LDH contents on thermal, physicomechanical, and morphological property of PVA films were investigated. Differential scanning calorimetric analysis reveals that LDH layers promote a new crystalline phase for PVA. The tensile analysis of PVA/LDH nanocomposites indicates reduction in tensile strength and modulus with change in LDH concentration and moisture. The microstructure analysis by optical microscopy and scanning electron microscopy demonstrates exfoliation and dispersion of LDHs in the PVA matrix in a disorderly fashion. The primary focus of the present investigation is to explore the potential of LDHs as nanofiller in a polyhydroxy polymer without surface modification. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

19.
Nanocomposite films were prepared through the blending of polyimide (PI) with octaphenyl silsesquioxane (OPS) and an amino‐functionalized analogue, octaaminophenyl silsesquioxane (OAPS), with a solution‐casting method. Although the PI–OPS composites showed visible phase separation at 5 wt %, the PI–OAPS composites were transparent with visible phase separation occurring only at 50 wt % OAPS. The interfacial interactions and homogeneity of the composites were characterized with scanning electron microscopy (SEM) and dynamic mechanical analysis. SEM analysis showed a uniform fracture surface for OAPS composites at concentrations up to 20 wt %. Interestingly, OAPS‐rich particles with sizes of less than 1 μm were formed within the PI matrix for the 50 wt % composite. The PI–OAPS composites showed higher glass‐transition temperatures (Tg's) than the pure PI. The PI–OPS composites showed a Tg lower than that of the pure PI, and this suggested poor interfacial interactions. The slightly enhanced thermal stability of PI–OAPS composites (up to 20 wt %) was attributed to the inherent thermal stability of OAPS at higher temperatures. There were small increases in the modulus and strength for the composites with respect to the base polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

20.
This article reports the cointercalation of acrylic acid (AA) and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) in the interlayer region of Mg2Al layered double hydroxide (LDH) and the application of this inorganic–organic composite material in the field of water superabsorbent. The monomers of AA and AMPS were cointercalated into galleries of Mg2Al−LDH (denoted as AA−AMPS/LDH) with various molar ratios by ion‐exchange method, which was confirmed by powder X‐ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and elemental analysis. The polymer‐based superabsorbent was prepared through in situ free‐radical aqueous copolymerization of AA and AMPS, with AA−AMPS/LDH as additive, N,N′‐methylenebisacrylamide (NMBA) as crosslinker and potassium persulfate (KPS) as initiator. The composition of this poly(AA‐co‐AMPS)/LDH was demonstrated as a good water superabsorbent. The LDH content, water absorbency, thermal stability, and swelling rate of this superabsorbent were also investigated in detail. Results showed that the incorporation of a 5 wt % AA−AMPS/LDH into polymer matrix increased its water absorbency significantly by 27.7% (in water) and by 51.5% (in 0.9 wt % NaCl solution). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

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