Summary: An organic‐inorganic hybrid material consisting of a 3‐(methacryloxy)propyl functionalized SiO2/MgO framework was synthesized. This hybrid was successfully reacted with styrene, butyl acrylate and butyl methacrylate via a free radical emulsion polymerization to form polymer composites. The polymer composites were investigated by means of FT‐IR spectroscopy, TGA, DSC and rheometry. It is shown that the polymer is linked covalently to the organic/inorganic hybrid. Although the polymer content is rather low, the composites exhibit a polymer‐like character and enhanced mechanical properties compared to the corresponding homopolymers.
Novel polyurethane (PU) composites were prepared, based on hybrid inorganic/organic phosphazene‐containing microspheres. The FT‐IR spectra have shown that the microspheres have been linked with PU matrix. The microstructure of the composites is investigated by SEM. In comparison with PU, the glass transition temperatures and thermal stability of the composites are increased. The results from tensile testing of the composites have indicated that tensile strength is improved and elongation at break is almost invariable. The investigation on the surface properties of the composites showed that the water contact angles are obviously increased by adding 2 and 4 wt.‐% microspheres to the matrix.
This work aims at improving the interfacial bonding between polyamide‐12 and CNFs. CNFs were oxidized and dispersed in polyamide‐12 giving rise to polymer nanocomposites. The oxidation caused an increase in the specific surface area and structural defects of the fibers, as indicated by surface area and Fourier‐transform Raman spectroscopy. The nanocomposites exhibited improved thermal and thermo‐oxidative stabilities. The oxidized nanofibers had marginal effect on the crystallinity and crystallization of the polyamide‐12. An over‐proportional enhancement of stiffness due to the fibers could be achieved. In spite of these improvements the fiber/polymer adhesion should be further improved.
The influence of talc loading on phase morphology of PLA/PCL/talc composites and improvement in resulting properties are reported. Talc‐based composites of PLA/PCL blends were prepared by melt blending. SEM analysis demonstrates that PLA appears as discrete domain phase, while PCL acts as a bulk phase in the blend. Talc addition decreases PLA domain sizes and voids in the matrix. This results in significant improvement of oxygen and water vapor barrier properties of composite by 33 and 25%, respectively, at 3 wt.‐% talc loading. DSC shows that talc acted as nucleating agent for PCL phase in the composite and improves its crystallinity. Various theoretical models based on dispersion and filler geometry are used to predict the tensile modulus and oxygen permeability.
Epoxy/BaTiO3 hybrid materials are prepared as good candidates for organic capacitors. The hybrid system is cured by using camphorquinone and a iodonium salt through a free‐radical promoted cationic polymerization using a long‐wavelength tungsten halogen lamp. The cured films are fully characterized. Morphological characterization shows a well‐dispersed inorganic phase within the organic matrix. Electrical characterization demonstrates a linear increase of the dielectric constant with increasing filler content, while low dielectric loss values are obtained.
Large positive thermal expansion in polymers is one of the major drawbacks in using polymers in applications where the sample dimensions play an important role. In this paper, we report a method to vary the thermal expansion of PMMA‐based polymer composites by blending with a negative thermal expansion material, PbTiO3. It is shown that the thermal expansion coefficient of the composite can be tailored by suitably adjusting the ratio of polymer and ceramic filler. The coefficient of thermal expansion has been measured using temperature‐dependent step‐height measurements via confocal microscopy. Using SEM, it is shown that the ceramic particles are homogeneously dispersed in the polymer matrix if the composite is obtained by the polymerization of the suspension of PbTiO3 in the monomer MMA. Composite formation is confirmed using XRD and Raman spectroscopy. To estimate the technological viability of such composite films, preliminary results of stress‐strain measurements are also presented.
Summary: The flex‐fatigue life of carbon‐black‐filled SBR was dramatically improved by incorporation of 4–5 phr nanodispersed clay. Addition of clay did not decrease the degree of crosslinking of the composite but improved the hysteresis and tearing energy. ESEM observation of the flexing‐fracture morphology indicated that nanodispersed clay layers had the advantage over carbon black in that they could blunt the crack.
Effect of the clay amount on the flex fatigue life of the composites. 相似文献
The synthesis of silver nanoparticles attached on the surface of a hollow cornet‐like polymer matrix which served as a reductant and host matrix is described. This hybrid organic/inorganic macromolecular matrix is exhibiting anion‐exchange properties, porous structure and hollow morphologies, and absorptions in the visible light region. Due to the anion‐exchange property and the 3D orientation of the macromolecular chains the material is defining a new functional organic/inorganic hybrid. For the synthesis of nanoparticles, no other reducing agents were used and silver nanoparticles with a mean diameter of less than 20 nm were attached on the surface of the polymer, thus inheriting the composite with high antibacterial activity tested in bacterial strains and yeasts.
Summary: Contact‐mode AFM adhesion strength measurements were employed in order to investigate the capability of PBBMA FR as an adhesion promoter in PP composites. The reactive FR exhibited superior coupling properties in comparison to conventional coupling agents such as PP‐g‐ma introduced in reinforced PP composites.
AFM image showing the recess carved out by the AFM tip in a PBBMA layer deposited on glass treated with APS. 相似文献
Summary: Novel poly(cyclotriphosphazene‐co‐sulfonyldiphenol) microtubes were successfully prepared via one‐pot synthesis using special templates generated in situ during the polymerization. The templates could be easily removed by dissolution in water. This approach overcame the multi‐step nature of general template methods. The as‐synthesized microtubes were 1–3 µm in width, about 100 µm in length and contained hexagon‐shaped channels. IR and NMR spectroscopies confirmed the covalently crosslinked chemical structure of the polymer tubes, and the tubes are thus mechanically and thermally stable. The polymer microtubes are of interest for use as chemical or biological sensors, controlled release and delivery of drugs, tissue engineering materials, absorbants and many other microscale investigations.
SEM images of triethylamine hydrochloride crystals produced in situ during formation of the tubes (left) and the polymer microtubes (right). 相似文献
In order to establish the structure‐property relationship in the case of clay containing polymer nanocomposites, detailed understanding of silicate layers dispersion into the polymer matrix is necessary. In this study, biodegradable poly[(butylene succinate)‐co‐adipate] (PBSA) was chosen as a model polymer and the nanocomposite of PBSA with organically modified montmorillonite (OMMT) was prepared via the melt‐mixing in a batch mixer. The degree of dispersion of silicate layers in the PBSA matrix was investigated by means of wide angle X‐ray diffraction, small angle X‐ray scattering, high‐annular‐angle‐dark‐field scanning transmission electron microscopy, and high resolution transmission electron microscopy combined with electron tomography. Results demonstrated the homogeneous dispersion of clay platelets in the PBSA matrix. However, the true exfoliation of silicate layers in the polymer matrix is quite difficult to achieve, although there are strong favourable interactions between the polymer matrix and the OMMT surface.
Summary: This study investigated the physico‐mechanical properties, odor and VOC emission of bio‐flour filled PP bio‐composites with different pozzolan contents. On increasing the pozzolan content, the tensile and flexural strengths of the bio‐composites were not significantly changed, whereas the impact strength and water absorption increased slightly and the odor intensity decreased due to the absorption of thermal degradation gases of PP and bio‐flour at the pore surface of the pozzolan. The VOC emission of the bio‐composites, analyzed by GC‐MSD, was mainly due to PP oxidation and the thermal degradation of bio‐flour during the extrusion process at high manufacturing temperatures. With increased pozzolan content, other organic compounds of the bio‐composites were not significantly changed, but the toluene emission of the bio‐composites was decreased. SEM and SEM/EDX mapping techniques were employed to investigate the porous form and the pozzolan distribution in the bio‐composites. From these results, we concluded that the addition of pozzolan in the bio‐composites was an effective method for reducing their odor and VOC emission without any reduction in mechanical properties.
This review presents the state of the art regarding the improvement of scratch resistance of polymeric coatings. In particular, our attention is focused on the effect of inorganic nanometric fillers on the scratch resistance of organic coatings. Two main strategies are described for the achievement of such nanostructured hybrid organic/inorganic coatings: either a top‐down or a bottom‐up approach.
Transparent polyimide (PI) and chemically modified graphene nanocomposite films are prepared from solutions of pyromellitic dianhydride (PMDA)/4,4′‐oxydianiline (ODA) poly(amic acid) with various amounts (0.2–0.8 wt%) of graphene carboxylic acid (GCA) in DMAc. The GCA is synthesized by modifying chemically oxidized graphene (COG) with many carboxylic acid groups (–COOH) and is well‐dispersed in DMAc, the organic solvent most frequently used for PI synthesis. The GCA sheets in the PI/GCA composite films are well‐dispersed and aligned two‐dimensionally in the direction parallel to the PI films, which enhances the mechanical properties of the nanocomposite films.
Organic/inorganic hybrid nanocomposite coatings were prepared through a dual‐cure process involving the cationic photopolymerization of a vinyl ether based system and the condensation of an alkoxysilane inorganic precursor. All formulations produced transparent cured films characterized by high gel contents. An increase in glass transition temperature and an increase in storage modulus above Tg in the rubbery plateau were observed with increasing TEOS content in the photocurable formulation. TEM micrographs showed that the organic and inorganic phases were strictly interconnected with no macroscopic phase separation; the sizes of the silica domains in the polymeric matrix were 3–5 nm.
A comparative study of the preparation and properties of composites of PCL with cellulose microfibres (CFs) containing butanoic‐acid‐modified cellulose (CB) or PCL grafted with maleic anhydride/glycidyl methacrylate as compatibilizers, is reported. The composites are obtained by melt mixing and analyzed using SEM, DSC, TGA, XRD, FT‐IR, NMR and tensile tests. An improved interfacial adhesion is observed in all compatibilized composites, as compared to PCL/CF. The crystallization behavior and crystallinity of PCL is largely affected by CF and CB content. Composites with PCL‐g‐MAGMA display higher values of tensile modulus, tensile strength and elongation at break.
The inherent properties of poly(lactide), a biocompatible and biodegradable polymer, are concurrently improved by the incorporation of a small amount of surface functionalized carbon nanotubes. A new method has been used to functionalize the CNTs' outer surface with hexadecylamine. A composite of PLA with functionalized CNTs has been prepared by melt‐extrusion. FT‐IR spectroscopy, Raman spectroscopy, DSC, and optical microscopy are used to investigate the thermal and mechanical property improvement mechanism in f‐CNTs containing PLA composite.
Natural fiber reinforced polymer composites are lightweight, economical and available in a variety of forms. They have low densities, comparable material properties, high molding flexibility and are environmentally friendly, making them a conceivable alternative to traditional fillers like mica, calcium carbonate and glass. By modifying either the resin system or the natural fiber, biocomposites can be designed for different applications ranging from products of commodity to aerospace, examples including electroactive papers, fuel cell membranes, controlled drug release mechanisms and biosensors. This review aims to analyze the advancement in the application of cellulose based materials in different sectors with a discussion of fundamental research in these areas.
Natural biomaterials were used to improve the biocompatibility of synthetic biopolymers. PCL was electrospun with natural biopolymers, silk fibroin, and small intestine submucosa. Due to increased electrical conductivity, the diameter of the composite fibers highly depended on the amount of SIS in the polymer solution. PCL/SF/SIS electrospun composites exhibited various synergistic effects, including enhanced mechanical properties and incredibly improved hydrophilicity compared to those of pure PCL and PCL/SF fibers. An initial cell attachment test demonstrated that the interactions between PC‐12 nerve cells and the PCL/SF/SIS composites were more favorable than those between PC‐12 cells and a PCL/SF composite.
Summary: A study of the structure–property relationships for nanocomposites prepared by melt compounding from ethylene–acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be independent of clay loading, in the range of 2–50 phr, and to change with the molecular architecture of the matrix polymer. An indication that the excess surfactant present in some of the clays, and the organic material added in others to expand the interlayer spacing, were expelled from the clay galleries during melt blending and acted as plasticisers for the matrix polymer, was obtained from WAXD and rheological characterisations.
TEM micrograph of the nanocomposite of EAA1 with 11 phr of 15A. 相似文献
