溶液插层法制备PPC/OMMT纳米复合材料及性能表征

通过溶液插层法制备了聚甲基乙撑碳酸酯/有机蒙脱土(PPC/OMMT)纳米复合材料,采用X射线衍射仪、热失重分析仪、透射电子显微镜(TEM)、动态力学性能测试仪(DMA)等对PPC/OMMT的性能进行了表征.XRD和TEM测试表明,OMMT均匀分散于PPC基体中并形成了插层型的纳米复合结构;DMA分析结果表明,复合材料的...     

Preparation and characterization of poly(vinyl chloride) calcium carbonate nanocomposites via melt intercalation

Calcium carbonate was synthesized by in situ deposition technique and its nano size (35–60 nm) was confirmed by transmission electron microscopy (TEM). Composites of the filler CaCO₃ (micro and nano) and the matrix poly(vinyl chloride) (PVC) were prepared with different filler loadings (0–5 wt%) by melt intercalation. Brabender torque rheometer equipped with an internal mixer has been used for preparation of formulations for composites. The effect of filler content both nano- and micro level on the nanostructure and properties is reported here. The nanostructures were studied by wide angle X-ray diffraction and scanning electron microscopy. The mechanical, thermal, and dynamic mechanical properties of PVC/micro- and nano-CaCO₃ composites were characterized using universal testing machine, thermogravimetric analyzer, and dynamic mechanical analyzer. The results of thermal analysis indicated that the thermal stability of PVC/nano-CaCO₃ composites was improved as compared with corresponding microcomposites, and that of pristine PVC and maximum improvement was obtained at 1 and 3 phr loadings. However, the tensile strength decreased significantly with increase loading of both nano- and micro-CaCO₃, whereas storage modulus and glass transition temperature increased significantly.     

Biodegradable poly(propylene carbonate)/montmorillonite nanocomposites prepared by direct melt intercalation

Intercalation-exfoliated nanocomposites derived from poly(propylene carbonate) (PPC) and organo-modified montmorillonite (OMMT) were prepared by direct melt blending in an internal mixer. The nano-scale dispersion of the OMMT layers within the PPC matrix was verified using wide angle X-ray scattering and transmission electron microscopy technologies. Static mechanical properties were determined by using a tensile tester. The PPC/OMMT nanocomposites with lower OMMT content showed an increase in thermal decomposition temperature when compared with both pure PPC and the composites prepared from un-modified MMT. Dynamic mechanical analysis indicated that nano-scale OMMT dispersed well within PPC matrix and therefore enhanced the storage modulus of the composites.     

Preparation and characterization of poly(methyl methacrylate)-clay nanocomposites via melt intercalation: Effect of organoclay on thermal, mechanical and flammability properties

The PMMA nanocomposites were prepared by melt processing method. The influence of organoclay loading on extent of intercalation, thermal, mechanical and flammability properties of poly(methyl methacrylate) (PMMA)-clay nanocomposites were studied. Three different organoclay modifiers with varying hydrophobicity (single tallow vs. ditallow) were investigated. The nanocomposites were characterized by using wide angle X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. The intercalation of polymer chain within the silicate galleries was confirmed by WAXD and TEM. Mechanical properties such as tensile modulus (E), tensile strength, percentage elongation at break and impact strength were determined for nanocomposites at various clay loadings. Overall thermal stability of nanocomposites increased by 16-17 °C. The enhancement in T_g of nanocomposite is merely by 2-4 °C. The incorporation of maleic anhydride as compatibilizer further enhanced all the properties indicating improved interface between PMMA and clay. The flammability characteristics were studied by determining the rate of burning and LOI.     

Preparation and characterization of gold/poly(vinyl alcohol)/MoS2 intercalation nanocomposite

Gold-molybdenum disulfide nanocomposites were prepared by means of exfoliation of a layered host and subsequent in situ oxidation–reduction of the intercalated auric compounds, using the interlayer of MoS₂ as the nanoreactor and poly(vinyl alcohol) (PVA) molecules as the dispersant. The nanocomposites were characterized by means of powder X-ray diffraction, Fourier transformation infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The electrical conductivity of the Au/PVA/MoS₂ nanocomposites at various temperatures was investigated. Results indicated that Au and PVA were intercalated in the layered MoS₂, at an interlayer distance of 2.072 and 0.928 nm. The intercalation of Au and PVA led to a significant increase in the electrical conductivity value of MoS₂, while the electrical conductivity value of the intercalation nanocomposites decreased with decreasing temperature.     

Preparation and characterization of melt processed poly(l-lactide)/layered double hydroxide nonocomposites

This work reports the fabrication and physical properties of biodegradable poly(l-lactide) (PLLA) composites containing a fraction of unmodified layered double hydroxides (LDH–NO₃) and γ-polyglutamate-modified layered double hydroxides (γ-LDH) by melt blending process. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) experimental results showed that the original LDH–NO₃ with the certain amount of aggregates was unevenly dispersed throughout the PLLA matrix. Conversely, γ-LDH allows the formation of an intercalated nanocomposite. Although the water vapor permeability of the PLLA/LDH systems was decreased with increasing the loading of LDH, the barrier property of PLLA reinforced with γ-LDH is superior to that of PLLA-L composites. The effects of both LDHs on mechanical and thermal properties of PLLA were also investigated.     

原位乳液插层法制备PBA/OMMT纳米复合母料及其在ABS中的应用

通过原位乳液插层法制备高有机蒙脱土(OMMT)含量的聚丙烯酸丁酯/有机蒙脱土(PBA/0MMT)纳米复合物,将其作为母料与ABS进一步熔融插层制得力学性能良好的ABS/OMMT纳米复合材料,并通过XRD、TGA和TEM等对材料进行了表征.结果表明:制得的PBA/OMMT母料为插层型纳米复合物,OMMT片层间距从2.38nm增大到3.85nm;采用母料法制备ABS/OMMT纳米复合材料,ABS链段易插层进入OMMT层间,使OMMT片层在ABS基体中达到剥离并以纳米尺度均匀分散,较好地保持了ABS的缺口冲击强度.     

The intercalation of poly(methyl methacrylate)/aluminophosphate nanocomposites and the properties improvement

Poly(methyl methacrylate) (PMMA)/dodecylamine templated lamellar aluminophosphate (DDA-LAP) intercalated nanocomposites are prepared by in situ bulk polymerization of MMA. The intercalated structure is characterized. With the intercalation of DDA-LAP in PMMA matrix, the glass-transition temperatures of nanocomposites (T_g) are increased. The nanocomposites obtained keep relatively high transparency in optical property and have a significant improvement in mechanical properties and thermal stability. The mechanism for the properties enhancement is investigated. The strong interfacial interaction between the aluminophosphate layers and the PMMA chains, the homogeneously distribution and the graphitized char formation during heating are three key roles for the properties improvement.     

Dielectric properties of montmorillonite clay filled poly(vinyl alcohol)/poly(ethylene oxide) blend nanocomposites

Organic–inorganic nanocomposites of poly(vinyl alcohol) (PVA)–poly(ethylene oxide) (PEO) blend filled with montmorillonite (MMT) nanoclay up to 10 wt.% concentration were synthesized by aqueous solution-cast technique. The complex dielectric function, electrical conductivity, electric modulus and impedance spectra of the nanocomposites were measured in the frequency range 20 Hz–1 MHz at ambient temperature. A direct correlation was observed between the real part of dielectric function and the mean relaxation time of the polymer chain segmental dynamics, with the exfoliated and intercalated MMT clay structures, and the extent of miscibility between PVA and PEO due to hydrogen bonded bridging through exfoliated MMT clay nanosheets. The large increase of dielectric relaxation time revealed that the dispersed exfoliated nanoscale MMT clay in the polymers blend matrix produces a large hindrance to the polymer chain dynamics. Results confirm that the real part of dielectric function of the nanocomposites can be tailored by varying amount of MMT clay filler for their use as nanodielectric materials in the microelectronic technology.     

Crosslinked aqueous dispersion of silylated poly (urethane–urea)/clay nanocomposites

Stable water-borne crosslinked silylated poly (urethane–urea) (CSPU)/clay nanocomposites, reinforced with various amounts of the organically modified clay, were prepared by a polyaddition reaction of toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI), polytetramethylene glycol and dimethylol propionic acid. This was followed by end-capping the free NCO groups of the PU prepolymer with phenylamino propyl trimethoxysilane and self-crosslinking. The particle size, viscosity and storage stability of these nanocomposites were measured. The particle size and viscosity of the IPDI-based nanocomposites were higher than the TDI-based ones. Intercalation of the silicate layer in the CSPU matrix were conformed by X-ray diffraction pattern and transmission electron microscopy studies. The mechanical properties of the SPU/clay nanocomposites were tested by tensile, dynamic mechanical, and nano-indentation measuring techniques and the respective properties were found to be enhanced by the reinforcing effect of organophilic clay. Modulus and hardness increased with an increase in the clay content in the CSPU matrix. Thermal stability, water and xylene resistance of the nanocomposites increased, as compared to pure CSPU and these properties increased with an increase in clay content. The mechanical properties, water and xylene resistance of the TDI-based nanocomposites were higher compared to the IPDI-based nanocomposites. A marginal reduction in transparency was observed with the addition of clay. Storage stability results confirmed that the prepared nanocomposite dispersions were stable.     

Nanostructure and morphology of poly(vinylidene fluoride)/polymethyl (methacrylate)/clay nanocomposites: correlation to micromechanical properties

Nanocomposites based on poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) with untreated clay were prepared in one step by reactive melt extrusion. Chemical reactions took place between the polymer matrices, the inorganic clay particles, and three reactive agents, leading to the PVDF/PMMA/clay nanocomposites. The microstructure characterizations were carried out by differential scanning calorimetry and wide-angle X-ray scattering (WAXS). The mechanical behavior was investigated by tensile experiments, impact tests, and microhardness measurements. The morphological characterization was carried out by optical and atomic force microscopy (AFM). The decrease of the melting and crystallization temperatures of the PVDF with the increasing PMMA content is attributed to the interactions between the oxygen of the PMMA carbonyl group and the PVDF’s hydrogen atom. WAXS analysis shows that there is neither an intercalation step nor total exfoliation in any composition. As the PMMA content increases, WAXS diagrams show either the PVDF α-crystallographic form, both, α- and β-forms, or only the β-form. For PMMA contents higher than 40 wt%, the materials became amorphous. The microhardness of the samples decrease for a PMMA content up to 20 wt%. The study by optical microscopy and AFM illustrates the significant effect in the presence of clay on the film’s surface morphology.     

Preparation and properties of biodegradable poly(L-lactide)/octamethyl-polyhedral oligomeric silsesquioxanes nanocomposites with enhanced crystallization rate via simple melt compounding

Biodegradable poly(l-lactide) (PLLA)/octamethyl-polyhedral oligomeric silsesquioxanes (ome-POSS) nanocomposites were prepared via simple melt compounding at various ome-POSS loadings in this work. Scanning and transmission electron microscopy observations indicate that ome-POSS were homogeneously dispersed in the PLLA matrix. Effect of ome-POSS on the nonisothermal crystallization behavior, isothermal melt crystallization kinetics, spherulitic morphology, crystal structure, dynamic mechanical properties, and thermal stability of PLLA in the nanocomposites was investigated in detail. It is found that the presence of ome-POSS enhances both nonisothermal cold and melt crystallization of PLLA in the nanocomposites relative to neat PLLA. The overall isothermal melt crystallization rates are faster in the PLLA/ome-POSS nanocomposites than in neat PLLA and increase with increasing the ome-POSS loading; however, the crystallization mechanism of PLLA remains unchanged. The nucleation density of PLLA spherulites is enhanced, while the crystal structure of PLLA is not modified in the PLLA/ome-POSS nanocomposites. The storage modulus has been apparently improved in the PLLA/ome-POSS nanocomposites with respect to neat PLLA, whereas the glass-transition temperatures vary slightly between neat PLLA and the PLLA/ome-POSS nanocomposites. The thermal stability of PLLA matrix is reduced slightly in the PLLA/ome-POSS nanocomposites.     

Thermal and morphological characterization of poly(ethylene terephthalate)/calcium carbonate nanocomposites

Nanocomposites composed of poly(ethylene terephthalate) (PET) filled with calcium carbonate particles of nanometer scale were prepared by polymerizing the polyester in the presence of the nanosized fillers. Besides plain calcium carbonate, carbonate nanoparticles coated with stearic acid were also used, in order to improve the compatibility between the polymeric matrix and nanofillers. Morphological analysis evidenced a good dispersion of both the nanopowders into the PET matrix, especially in the case of coated calcium carbonate. The strong interfacial adhesion between the two phases is also responsible for the increase of the glass transition and melting temperatures in the nanocomposites compared to plain PET. Finally, non-isothermal crystallization studies revealed that the coated CaCO₃ is a good nucleating agent for PET. Analysis of non-isothermal crystallization data with the Ozawa theory was successful for plain PET and PET/un-CaCO₃, but this method failed to describe the dynamic solidification of the PET/c-CaCO₃ nanocomposite.     

Preparation and characterization of bio-nanocomposites based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and CoAl layered double hydroxide using melt intercalation

In this study, the exfoliated bio-nanocomposites based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3,4)HB) and cobalt-aluminum layered double hydroxide (LDH) were prepared via melt intercalation. The thermal stability, thermal combustion and thermo-mechanical properties for these bio-nanocomposites were systematically investigated. The formation of an exfoliated structure was confirmed by X-ray diffractometry and transmission electron microscopy analysis. The microscale combustion calorimetry results show that the heat release capacity (HRC) of the bio-nanocomposites is an important parameter of the fire hazard which is significantly reduced with the addition of LDH. The storage modulus of the bio-nanocomposites with small amount of LDH is remarkably enhanced measured by dynamic mechanical analysis.     

Improving the mechanical properties of thermoplastic starch/poly(vinyl alcohol)/clay nanocomposites

Thermoplastic starch/poly(vinyl alcohol) (PVOH)/clay nanocomposites, exhibiting the intercalated and exfoliated structures, were prepared via melt extrusion method. The effects of clay cation, water, PVOH and clay contents on clay intercalation and mechanical properties of nanocomposites were investigated. The experiments were carried out according to the Taguchi experimental design method. Montmorillonite (MMT) with three types of cation or modifier (Na⁺, alkyl ammonium ion, and citric acid) was examined. The prepared nanocomposites with modified montmorillonite indicated a mechanical improvement in the properties in comparison with pristine MMT. It was also observed that increases in tensile strength and modulus would be attained for nanocomposite samples with 10%, 5% and 4% (by weight) of water, PVOH and clay loading, respectively. The clay intercalation was examined by X-ray diffraction (XRD) patterns. The chemical structure and morphology of the optimum sample was also probed by FTIR spectroscopy and transmission electron microscopy (TEM).     

Characterization of electrospun poly(p-dioxanone) and poly(p-dioxanone)/clay nanocomposite fibers

PPDO was successfully electrospun into continuous, ultrafine fibers by using DMSO as solvent for the first time. The concentration of PPDO in DMSO and the electrospinning temperature were optimized. PPDO/LAP nanocomposites were also electrospun in DMSO. At 70 degrees C, ultrafine PPDO fibers were obtained from 35 wt% solution and the PPDO/LAP nanocomposite fibers were yielded from 55 wt% solution. Electrospun fibers of the PPDO/LAP nanocomposites showed higher degree of crystallinity due to the presence of embedded nanoparticles.     

Crystal form and phase structure of poly(vinylidene fluoride)/polyamide 11/clay nanocomposites by high-shear processing

Polyamide 11 (PA11)/clay, Poly(vinylidene fluoride) (PVDF)/clay and PVDF/PA11/clay nanocomposites were prepared by melt processing using a high shear extruder. Two types of organoclay with different modified alkyl tails and different polarities were used for PA11 and PVDF nanocomposites. PA11 nanocomposites derived from an organoclay having one alkyl tail show a well-exfoliated morphology but no crystal form transformation, whereas those derived from an organoclay having two alkyl tails give a little worse clay dispersion with the clear alpha to gamma crystal form transition with the addition of the clay. In contrast, the PVDF composites derived from the two organoclays result in a poor dispersion. In addition, PVDF/PA11 blend nanocomposites with a novel morphology have been fabricated using the high-shear extruder. It was found that the clay platelets were selectively dispersed in the PA11 phase with the size of larger than 200 nm, while no clay platelets were located in the PVDF phase and in the PA11 nanodomains with the size of smaller than 200 nm. Moreover, the addition of organoclay shows significant effects on the phase structure of PVDF/PA11 blends.     

Preparation and characterization of chitosan/poly(vinyl alcohol)/poly(vinyl pyrrolidone) electrospun fibers

Ultrafine fibers of chitosan/poly(vinyl alcohol)/poly(vinyl pyrrolidone) (CS/PVA/PVP) were prepared via electrospinning. The structure and morphology of CS/PVA/PVP ultrafine fibers was characterized by the Fourier transform infrared (FT-IR) spectroscope and scanning electron microscope (SEM). Furthermore, the effects of the concentration of PVA, PVP and the electrospinning voltage on the morphology of ultrafine fibers were investigated the the SEM. When the concentration of PVA was at the range of 30wt%–40wt%, ultrafine fibers could be obtained. The diameter distributions of ultrafine fibers decreased when the electrospinning voltage increased from 20 to 30 kV. The rough surface fibers could be obtained after etching with CHCl₃.