α,β,β-Trifluoroethylenesulfonyl fluoride (TFESF) was grafted onto polyethylene (PE) film by a simultaneous-irradiation method. The influences of the grafting conditions were analyzed kinetically. The dependencies of the grafting rate on the dose rates and monomer concentrations ranging from 10 to 75% were found to be of 1 and 0 order, respectively. The overall activation energy for the graft polymerization was 2.05 × 104 J/mol. The grafting rate was found to be independent of the film thicknesses ranging from 25 to 100 μm. 相似文献
A method to generate a porous region near the surface of a polymer is suggested. In this method the region near the surface is swollen by immersing the polymer for a short time in a solvent. Subsequently, the polymer is introduced in a nonsolvent (for the polymer) that is, however, miscible with the solvent. The formation of the porous region is a result of (1) the swelling accompanied by the disentanglement of the surface molecular chains, and the dissolution of some of them during the immersion in the solvent, and (2) the rapid extraction of the solvent from the swollen region by the nonsolvent. The porous surface provides a matrix into which a second incompatible monomer can be polymerized so that the two otherwise incompatible polymers can adhere to one another. 相似文献
Understanding the structure/property relationship in polymer/layered silicate nanocomposites is of great importance in designing materials with desired properties. In order to understand these relations, a series of polylactide (PLA)/organically modified layered silicate (OMLS) nanocomposites have been prepared using a simple melt extrusion technique. Four different types of OMLS have been used for the preparation of nanocomposites, three were modified with functionalized ammonium salts while fourth one was a phosphonium salt modified OMLS. The structure of the nanocomposites in the nanometer scale was characterized by using wide-angle X-ray diffraction and transmission electron microscopic observations. Using four different types of layered silicates modified with four different types of surfactants, the effect of OMLS in nanocomposites was investigated by focusing on four major aspects: structural analysis, thermal properties and spherulite morphology, materials properties, and biodegradability. Finally, we draw conclusions about the structure/property relationship in the case of PLA/OMLS nanocomposites. 相似文献
High-purity Si3N4 (with 2.5 wt% glassy SiO2) doped with 0 to 450 at.ppm of Ca was prepared as a model system to investigate the effects of grain-boundary segregants on fracture phenomenology at 1400°C. Subcritical crack-growth (SCG) resistance as well as creep resistance was degraded significantly by the presence of a small amount of Ca. The internal friction of the doped materials exhibited the superposition of a grain-boundary relaxation peak and a high-temperature background, and the apparent viscosity of the grain-boundary film was determined from the peak. Based on these experimental data, the fracture mechanism at 1400°C was divided into three regions: "brittle," SCG, and creep failure as a function of both external strain rate and Ca concentration, C Ca. From the investigation of the C Ca dependence of the critical strain rate for the transition from "brittle" to SCG fractures, the SCG phenomenon is suggested to be triggered by small-scale, grain-boundary sliding. The C Ca dependence of "steady-state" creep rate was far from the theoretical dependence of diffusional creep via a solution-precipitation mechanism. The discrepancy was interpreted to be due to the presence of an impurity-insensitive creep component. This component may correspond to the lowest limit of the tensile creep rate in Si3N4 polycrystalline materials containing intergranular glassy-SiO2 film. 相似文献
Summary: Polyacrylonitrile (PAN) particles with micro‐size ranges (0.15–2 μm) were prepared by emulsion and dispersion polymerizationa and in supercritical carbon dioxide media. The PAN particles were blended with Nylon 6 (PA6) at 220 °C by using a miniature mixer; it was found that melt‐mixing was possible for PAN‐rich compositions as high as 70 wt.‐%. Blends were characterized by scanning electron microscopy, IR, viscosity measurements, differential scanning calorimetry, and dynamic mechanical thermal analysis (DMTA). The size and shape of original PAN particles were retained in PAN/PA6 blends. The useful range to blend PAN particles size was less than 1 μm in terms of shape retention of the PAN particles in blends. Blends with 40 wt.‐% PAN content were found to be melt‐processable. The elastic modulus was higher for PAN/PA6 blends than pure PA6.
SEM photograph of PAN‐SC/PA6 blend with a 40/60 weight ratio. 相似文献
Summary Since the long-chain fatty acid sucrose diesters inevitably produced in the synthesis of monoesters are only slightly soluble
in water, no important use can be found for them at the present time except as oilsoluble emulsifying agents.
In order to exploit new uses we have attempted to improve their solubility in water by introducing oxyethylene radicals into
the molecule.
The addition reaction of ethylene oxide with the sucrose diesters was carried out in an autoclave in the presence of alkaline
catalysts. With the reaction temperature maintained between 100–130° the pressure decreased as the reaction proceeded, and
one to two hours were required to consume the ethylene oxide used.
The addition products are yellow or orange oily materials soluble in water. Aqueous solutions showed good surface-active properties. 相似文献
α-Methylenemacrolides having various groups, such as aromatic, ether, and amine, were enzymatically, anionically, and radically polymerized. The polymerization with the lipase catalyst successfully afforded polymers only through the ring-opening process, whereas the vinyl polymerizations selectively proceeded by using anionic and radical initiators. The polyesters obtained by the enzymatic polymerization have a polymerizable methacrylic methylene group in the main-chain, in addition to the aromatic and polar groups, and were further radically polymerized to quantitatively produce a cross-linked polymer gel. 相似文献
The change in morphology and interface quantities have been analyzed for an immiscible polymer blend during reactive processing. A model polymer/polymer combination, hydroxy-terminated poly(ε-caprolactone)/liquid rubber with α, ω-carboxy groups, was employed. The blend was subjected to light scattering measurements, ellipsometry, and gel permeation chromatography (GPC). Size reduction of the dispersed phase during processing was followed by a systematic decrease in the correlation distance ζ and an increase in the specific interfacial area Ssp, both by the Debye-Bueche plot of light scattering profiles. Also observed was the time variation of the volume fraction of interface Vλ estimated as a product of the Ssp and the interfacial thickness by ellipsometry. The changes in ζ, Ssp, and Vλ with processing were accelerated when a coupling agent,γ-aminopropyltriethoxysilane (APS), was added. The amount of block copolymer formed in-situ in the APS-loaded system was estimated by GPC with RI and UV detectors. For the size reduction kinetics in both APS-loaded and -unloaded systems, Rittinger's law was found to be applicable. 相似文献