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101.
Achintya Kumar Sen Bibha Mukherjee A. S. Bhattacharya L. K. Sanghi P. P. De Anil K. Bhowmick 《应用聚合物科学杂志》1991,43(9):1673-1684
An attempt is made to develop a novel series of cable sheathing compounds with variation in chlorine content and sufficient fire retardance and unique low-smoke characteristics. These are prepared by blending PVC and functionalized polyolefins in different compositions. PE and EPDM have been functionalized by grafting dibutyl maleate (DBM) using DCP as initiator. FRLS compounds made from PVC-functionalized polyolefin blends possess the special characteristics of low-smoke, low-acid-gas generation, increased fire retardance, and improved volume resistivity, which are much better in comparison with a typical PVC sheathing compound. Thermoplastic elastomer (TPE) based nonhalogen FRLS compounds are also reported. The mechanisms for grafting, polymer-polymer and polymer-filler interactions have been presented. 相似文献
102.
In a recent communication it was shown that the pressure losses during the solid phase compaction of a polymeric powder could be predicted from a simple relationship of the form: where is a function of the geometry of the compact. This has now been explored in more detail and it has been found that for PVdC and PVC the factor K is dependent on the rate of compaction and the die surface finish but is independent of compaction pressure and die diameter. To illustrate the effect of the pressure losses on the structural uniformity of the compacts, microhardness measurements were taken at a large number of points across a section of each sample. A computer plot of hardness contours provided a picture of the homogeneity of the sample which could be related to the compaction conditions and average density of the compact. 相似文献
103.
Anil Kumar 《应用聚合物科学杂志》1987,34(2):571-585
The differential equations governing the molecular weight distribution (MWD) in step-growth polymerization are coupled and nonlinear and a large number of them must be solved simultaneously to keep the truncation error low. In this work, these equations have been decoupled so that they can be solved sequentially. The solution of these is independent of the truncation error and there is considerable saving of computation time. To demonstrate the efficiency of the algorithm, the formation of polyethylene terephthalate (PET) in batch reactors with ethylene glycol evaporating has been analyzed. The feed to the reactor is taken as polymer with its oligomers present according to the Flory's distribution. The effect of pressure and temperature of the reactor on the progress of polymerization has been modelled and evaluated. The amount of ethylene glycol distilled, the concentrations of the first five oligomers Q1 to Q5, the number average chain length, and the polydispersity index of the polymer have been determined. It is shown that the reduced pressure and increased temperature reduce the concentration of the condensation product in the reaction mass, thus pushing the polymerization in the forward direction. Lastly the CPU time on Dec 1090 using this algorithm is only 0.40 s compared to about 10 min for similar computations using other existing methods. 相似文献
104.
R.L. Paul 《Electrochimica acta》1978,23(10):991-994
A design for a motor-speed controller of low cost and high precision, is presented. It makes possible the regulation of the rotation speed of a series-wound electric motor to an accuracy of ± 1.5 rpm over the range 15 to 5000 rpm. The design incorporates a digital display of the rotation speed, and provides for the programming of the speed by an external voltage source. 相似文献
105.
Sykes EC Han P Kandel SA Kelly KF McCarty GS Weiss PS 《Accounts of chemical research》2003,36(12):945-953
Adsorbate interactions and reactions on metal surfaces have been investigated using scanning tunneling microscopy. The manners in which adsorbates perturb the surface electronic structure in their vicinity are discussed. The effects these perturbations have on other molecules are shown to be important in overlayer growth. Interactions of molecules with surface steps are addressed, and each molecule's electron affinity is shown to dictate its adsorption sites at step edges. Standing waves emanating from steps are demonstrated to effect transient molecular adsorption up to 40 A away from the step edge. Halobenzene derivatives are used to demonstrate how the surface is important in aligning reactive intermediates. 相似文献
106.
Racemicezo-brevicomin, racemic frontalin, and myrcene were released at two proportions (51400 and 111), each at three levels (1 ×, 10 ×, and 100 ×) in a ponderosa pine forest in central California. The 51400 mix was based on an estimate of the relative amounts released from a ponderosa pine under attack by the western pine beetle,Dendroctonus brevicomis. MoreD. brevicomis were trapped at a source of the three compounds released at 51400 than were trapped at a source released at 111, at all three levels, but this difference was statistically significant only at the 1 × and 10 × levels. Sex ratio of trapped beetles and distribution of catch at the source of attractant and 5 m away apparently did not differ between relative release rates.Coleoptera: Scolytidae.Trade names are mentioned solely for information. No endorsement by the U.S. Department of Agriculture is implied. 相似文献
107.
Paul Mulvaney 《Israel journal of chemistry》1993,33(1):89-94
The redox chemistry of thallium clusters in aqueous solution has been investigated by pulse radiolysis and γ-radiolysis. Using Ru(bpy)32+ as a redox indicator, it is shown that the redox potential of the Tl42+/+ couple is more positive than −1.27 V NHE, and that the Tl+/Tl2+ couple's redox potential is more negative than −1.27 V NHE. Ru(bpy)3+ reduces Tl42+ with a second-order rate constant of 6±2 × 108 M−1s−1. Metallic particles of thallium are predicted to have a surface plasmon absorption band at 205 nm in water. The reduced Tl content in a sol can be measured by air-free titration with CCl4 or methylviologen. 相似文献
108.
Phase behavior of blends of aliphatic polyesters with a vinylidene chloride/vinyl chloride copolymer
A series of aliphatic polyesters having CH2/COO ratios from 2 to 14 in their repeat units were blended with a copolymer of vinylidene chloride containing 13.5% by weight of vinyl chloride. Blends of polyesters having CH2/COO < 4 did not form completely miscible amorphous phases, whereas polyesters having CH2/COO ≥ 4 did form completely homogeneous amorphous phases for all temperatures below the decomposition point except for the polyester with CH2/COO = 14 which showed reversible phase separation on heating, i.e., lower critical solution temperature behavior. Interaction parameters were estimated by melting point depression and by analog calorimetry. The behavior reported here is qualitatively similar to that reported earlier for blends of aliphatic polyesters with poly(vinyl chloride), polyepichlorohydrin, polycarbonate, styrene–allyl alcohol copolymers, and the hydroxy ether of bisphenol A. 相似文献
109.
This paper presents a comparative study how reactor configuration, sludge loading and air flowrate affect flow regimes, hydrodynamics, floc size distribution and sludge solids-liquid separation properties. Three reactor configurations were studied in bench scale activated sludge bubble column reactor (BCR), air-lift reactor (ALR) and aerated stirred reactor (ASR). The ASR demonstrated the highest capacity of gas holdup and resistance, and homogeneity in flow regimes and shearing forces, resulting in producing large numbers of small and compact flocs. The fluid dynamics in the ALR created regularly directed recirculation forces to enhance the gas holdup and sludge flocculation. The BCR distributed a high turbulent flow regime and non-homogeneity in gas holdup and mixing, and generated large numbers of larger and looser flocs. The sludge size distributions, compressibility and settleability were significantly influenced by the reactor configurations associated with the flow regimes and hydrodynamics. 相似文献
110.
Recycling of waste plastics as a blend of generic types is attractive since a difficult separations problem is avoided. However, blends of incompatible polymers are frequently very brittle and cannot be considered for many applications. Additives which modify the blend to give it ductility may provide a solution to this problem. Chlorinated polyethylene (CPE) made by a slurry process has been suggested for this application by Schramm and Blanchard. Further documentation of the effectiveness of this approach is given here. Addition of CPE to such a blend generally increases the elongation at break and the energy to break very dramatically with ordinarily some loss in strength and modulus. This approach works most effectively in blends of high polyethylene and poly(vinyl chloride) content. Three grades of CPE were studied here which revealed that the specific structure of the CPE molecule is a factor. The effectiveness of CPE for blend modification is believed to derive from the graded molecular structure acquired during chlorination. 相似文献