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991.
992.
The UV‐curable urethane‐acrylates based on 2‐hydroxyethyl methacrylate (HEMA)‐terminated polyurethane (PU) for lithographic and coating applications are investigated in this study. Series of PU prepolymers were made from 4,4‐diphenyl methane diisocyanate (MDI), poly(propylene oxide) glycol (PPG 400), poly(butylene adipate)glycol (PBA 500), or poly(tetramethylene oxide) glycol (PTMO 1000) and are terminated with HEMA. The 2,2‐azobisisobutyronitrile (AIBN) was used as a UV‐initiator under air atmosphere. The curing kinetics of HEMA‐terminated PU film were studied. The curing analysis, using FTIR and reaction kinetics, indicate the reaction rate equation correlates well with the film thickness [T], initiator concentration [I], unreacted double bond concentration [C?C], and exposed energy [E] of the reaction system. The kinetic rate equation for the UV‐curable reaction can be written as © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3162–3166, 2004 相似文献
993.
Summary: Blends of single‐site catalysed ethylene‐α‐butene (C4VLDPE) and ethylene‐α‐octene (C8VLDPE) copolymers were prepared by melt extrusion. The phase morphology, thermal and mechanical properties of the blends have been investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile test and dynamic mechanical analysis (DMA). Depending on the composition and thermal history, significant differences in structure and behaviour were found. It was also found that some degree of co‐crystallization occurred for quenched blends; whereas most of the oven slowly cooled blends showed two well‐defined melting peaks, indicating that the slow cooling favoured partial segregation of the fractions with different degrees of branching to form two morphologies. Moreover, SEM revealed morphology of the thinner crystals distributed in‐between the thicker sheaf‐like crystals for the slowly cooled blends with 20–50% C8VLDPE. Therefore, the synergism in mechanical properties for the blends with 20–50% C8VLDPE is due to a combination of larger crystal size, more complete phase separation and interfacial interaction produced by the segregation effect of the slow cooling treatment. DMA studies showed that the storage modulus increased as the addition of C8VLDPE and modulus for the slowly cooled blends are about twice those measured for the quenched ones, indicating higher stiffness of the blends. The smooth shift of β relaxation temperature with addition of C8VLDPE for both sets of blends confirmed the miscibility in the amorphous phase.
SEM image of the C4VLDPE‐C8VLDPE (50/50) blend after oven slow cooling treatment. 相似文献
994.
The synthesis and application of polybenzoxazine adsorption resin was studied. First, the precursor was synthesized by the solventless method. And then a kind of spherical and granular polybenzoxazine resin was obtained using reverse‐phase suspension polymerization technique in the process of solidification. Besides, the influence of dispersion medium, the volume ratio of precursor to medium, the solidification temperature, and the agitation speed were studied in detail in the process of polymerization. Second, the spherical shape of the polybenzoxazine resin was identified by scanning electronic microscope and the thermal stability of resin was measured by thermogravimetric analysis. Finally, the adsorption capacity of the spherical resin on pyridine was studied in cyclohexane systems. The correlation coefficient of Langmuir adsorption constant temperature line was bigger than 0.99, which indicated that the equilibrium sorption date was coincident with the Langmuir isotherm equation. And the saturated adsorptive capacity of dried resin achieved 222.2 mg g?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
995.
Silyl‐crosslinked urethane elastomer modifying epoxy resin has drawn much interest. Here the triethoxysilyl‐terminated polycaprolactone elastomer (PCL‐TESi) modifying diglycidylether of bisphenol A epoxy resins (DGEBA) system was chosen, and then the effect of the type of curing agent on the phase structure of the studied epoxy resin system was investigated. The modified systems were obtained with different phase structures by varying the formulations of the curing agent. It was experimentally shown that with the addition of aminosilane (KBE‐9103), the crosslinked density was greatly increased. The cured system also showed from SEM and TEM analysis that addition of KBE‐9103 increased the compatibility between the PCL‐TESi and DGEBA, which made the ductility of the system decrease, but also indicated from TEM that addition of much KBE‐9103 made the reacted silicone particles coagulate each other. The state of phase separation from TEM in the cured system was theoretically explained. These would serve the deeper studies of the mechanism of silyl‐crosslinked urethane elastomer modifying epoxy resin in the future. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 611–619, 2005 相似文献
996.
Polyurethane dispersion coatings containing phosphate and siloxane chains were evaluated for their self‐assembling properties for a single‐coating system. Dynamic contact angles (DCAs) and X‐ray photoelectron spectroscopy (XPS) were used to study the coating–air interface. The siloxane chains were the predominant species on the surfaces of the coatings. The wetting properties of the coating–air interface were reversed when the coated panels were immersed in an ionic solution, and the decrease in hydrophobicity was linear with time. Results from XPS and DCA analyses were similar. The self‐assembling properties of the coatings could be useful in the development of hydrophobic coatings from hydrophilic polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 893–899, 2003 相似文献
997.
998.
Mei‐Rong Huang Sheng‐Xian Li Zhi‐Qing Dong Wei Feng Xin‐You Wang Shu‐Ying Gu Yan‐Hui Wu Xiang‐An Huang 《应用聚合物科学杂志》2002,83(14):3013-3021
Several multilayer thin low‐density polyethylene (LDPE) films were fabricated by blown thin film having a thickness of 7 μm and an area of 130 cm2. They were characterized for their oxygen‐enrichment performance from air by a constant pressure–variable volume method in a round permeate cell with an effective area of 73.9 cm2. The relationship between oxygen‐enrichment properties, including oxygen‐enriched air (OEA) flux, oxygen concentration, permeability coefficients of OEA, oxygen, nitrogen, as well as separation factor through the multilayer LDPE films, and operating parameters, including transfilm pressure difference, retentate/permeate flux ratio, temperature, as well as layer number, are all discussed in detail. It is found that all of the preceding oxygen‐enrichment parameters increase continuously with an increase of transfilm pressure difference from 0.1 to 0.65 MPa, especially for the trilayer and tetralayer LDPE films. The oxygen concentration and separation factor appear to rapidly increase within the retentate/permeate flux ratio below 200, and then become unchangeable beyond that, whereas the OEA flux and the permeability coefficients of OEA, oxygen, and nitrogen seem to remain nearly constant within the whole retentate/permeate flux ratio investigated, especially for the monolayer and bilayer LDPE films. The selectivity becomes inferior, whereas the permeability becomes superior, as the operating temperature increases from 23 to 31°C. The highest oxygen concentration was found to be 44.8% for monolayer LDPE film in a single step with air containing oxygen of 20.9% as a feed gas and operating pressure of 0.5 MPa at a retentate/permeate flux ratio of 340 and 23°C. The results demonstrate a possibility to prepare an oxygen‐enriching membrane directly from air, based on the easily obtained thin LDPE films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3013–3021, 2002; DOI 10.1002/app.2331 相似文献
999.
A combination of crosslinked poly(4‐vinylpyridinium)chloride [P4‐H]Cl ( I ) and sodium nitrite or quaternized crosslinked poly(N‐methyl‐4‐vinylpyridinium)nitrite [P4‐Me]NO2 ( II ) was used as effective nitrosating agents for the N‐nitrosation of secondary amines under mild and heterogeneous conditions in moderate to excellent yields. The spent polymeric reagents can usually be removed quantitatively and regenerated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1064–1067, 2007 相似文献
1000.
The kinetics of curing for a modified bismaleimide (BMI) resin was investigated to ascertain a suitable cure model for the material. The resin system used in this study was composed of 4,4′‐bismaleimidodiphenylmethane (BMIM) and 0,0′‐diallyl bisphenol A (DABPA, DABA). The BMIM was the base monomer and the DABPA was the modified agent. A series of isothermal DSC runs provided information about the kinetics of cure in the temperature range 170–220°C. Regardless of the different temperatures, the shape of the conversion curves was similar, and this modified BMI resin system underwent an nth‐order cure reaction. Kinetic parameters of this BMI resin system, including the reaction model, activation energy, and frequency factor, were calculated. From the experimental data, it was found that the cure kinetics of this resin system can be characterized by a first‐order kinetic model. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3338–3342, 2004 相似文献