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101.
A new aromatic diamine monomer containing benzoxazole substituents was prepared by a multistep synthesis starting from 1,4‐dibromo‐2,5‐difluorobenzene. The diamine was polymerized with commercial aromatic dianhydride or dicarboxylic acid chloride monomers to provide several different poly(amic acid)s and polyamides with their inherent viscosities in the range of 0.24–0.46 dL/g. Thermal properties of these polymers including thermal imidization of poly(amic acid)s into polyimides were investigated by using FTIR, DSC, and TGA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 178–185, 2004 相似文献
102.
In this work mathematical models were developed to represent the kinetics of volume changes of fluid spaces associated with
infusion of Ringer’s solution. During infusion of Ringer’s solution, the human body is assumed to be characterized by the
two-fluid space model which has second volume space in addition to the first volume so that fluid exchanges between these
two spaces are possible. Various infusion types were tested to accommodate different medical situations. Volunteers were given
Ringer’s solution and the changes in blood hemoglobin were detected. From the comparison with experimental data, the two-fluid
space model was found to represent adequately the kinetics of human volume expansion during infusion of Ringer’s solution. 相似文献
103.
High‐density polyethylene (HDPE) beads were successfully surface‐crosslinked in a modified plasma reactor. The modified plasma reactor treats large amounts of beads, which are uniformly surface‐crosslinked. In this study, effects of the gas pressure, radio‐frequency (RF) power, and the treatment time on the degree of surface crosslinking were systematically investigated. Degree of surface crosslinking was measured by solvent extraction method (boiling xylene method, BXM). The gel content of plasma‐treated HDPE increases from 0.0 to 1.05% within 10 min at 100 mTorr, 200 W. FTIR and DSC analyses show that the crosslinked layer after plasma treatment is limited only at HDPE surface without changing the bulk thermal property of HDPE. Through the analysis of FTIR, it was confirmed that main peaks corresponding to CH2 bands were decreased and two peaks corresponding to CF2 and CF3 were observed after plasma surface modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2921–2929, 2002; DOI 10.1002/app.10295 相似文献
104.
Kyung-Ju Choi Joseph E. Spruiell James L. White 《Polymer Engineering and Science》1989,29(21):1524-1527
The present paper describes an analysis of the orientation developed in biaxially stretched polystyrene films in terms of the kinematics of the process and a viscoelastic constitutive equation. It was possible to achieve reasonable agreement of predicted and experimental birefringences through use of a convected Maxwell model and the Rheo-Optical Law. 相似文献
105.
Hyun Ju Lim Sung Jun Lee Han Gon Choi Jung Ae Kim Chul Soon Yong Sung Soo Han Seok Kyun Noh Jinho Jang Won Seok Lyoo 《应用聚合物科学杂志》2007,106(5):3268-3272
High‐molecular‐weight atactic poly(vinyl alcohol) (a‐PVA) gels loaded with (R,S)‐2‐(3‐benzoylphenyl)propionic acid (ketoprofen) were prepared from 5, 6, 7, and 8 g/dL solutions of a‐PVA with a number‐average degree of polymerization of 4000 in an ethylene glycol/water mixture with an aging method to identify the effect of the initial polymer concentration on the swelling behavior, morphology, and thermal properties of a‐PVA gels. Then, the release behavior of ketoprofen from a‐PVA gels was investigated. As the polymer concentration decreased, the ability for network formation decreased, and the degree of swelling of the a‐PVA gels increased. In addition, the enthalpy increased with an increase in the a‐PVA concentration, but the melting temperatures of the gels prepared at different initial polymer concentrations were the same; this indicated that tighter gel networks would be formed by a higher polymer chain density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
106.
Tae Hwan Kim B. Ramachandra Jung Sik Choi M. B. Saidutta Ko Yeon Choo Sun-Dal Song Young-Woo Rhee 《Catalysis Letters》2004,98(2-3):161-165
Methanol selective oxidation to formaldehyde over a modified Fe-Mo catalyst with two different stoichiometric (Mo/Fe atomic ratio = 1.5 and 3.0) was studied experimentally in a fixed bed reactor over a wide range of reaction conditions. The physicochemical characterization of the prepared catalysts provides evidence that Fe2(MoO4)3 is in fact the active phase of the catalyst. The experimental results of conversion of methanol and selectivity towards formaldehyde for various residence times were studied. The results showed that as the residence time increases the yield of formaldehyde decreases. Selectivity of formaldehyde decreases with increase in residence time. This result is attributable to subsequent oxidation of formaldehyde to carbon monoxide due to longer residence time. 相似文献
107.
Four temporarily solubilised azo disperse dyes based on 1-substituted-2-hydroxypyrid-6-one were synthesised and characterised. The dyes showed high extinction coefficients and had a yellow shade on polyester fabric. They were successfully applied to polyester without the use of dispersants and the optimum pH was found to be 5. It was found that the dyes could be alkali-cleared due to ionisation of the dye under mild alkaline conditions. The dyes exhibited good to excellent fastness properties on the polyester fabric. 相似文献
108.
Although carbon fiber epoxy composite materials have excellent properties for structures, the joint in composite materials often reduces the efficiency of the composite structure because the joint is often the weakest area in the composite structure.
In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed.
From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints. 相似文献
In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed.
From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints. 相似文献
109.
110.
Hyoung Jin Choi Yong Woo Inn Myung S. Jhon 《Korean Journal of Chemical Engineering》1994,11(3):145-152
Polymer migration is a generally well-known phenomenon in a flow field, and it has been verified that the sources of such
phenomena are nonhomogeneity of the flow, concentration effects and hydrodynamic interactions between the polymer molecules.
In addition, temperature effects were found to be another source of polymer migration. The Langevin equation for a polymer
molecule was first derived from single chain dynamics using a kinetic theory for the bead-spring elastic harmonic dumbbell
model, as described in part I (reference [1]). In this paper the diffusion equation and concentration profile of the polymer
molecules induced by a temperature gradient are obtained from the Fokker-Planck equation. A new differential operator is also
introduced to calculate the concentration profile. From the concentration equation obtained in the general flow geometry,
we find that in dilute polymer solution there are significant effects on the polymer migration not only due to the nonhomogeneity
of the flow field but also due to temperature gradients. 相似文献