ISSN:0008-4034    

DOI:10.1002/cjce.5450690301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractFree radical reactions, carried out in polymer melts, have become a popular method of chemically modifying polyolefins. The elementary free‐radical reactions which are relevant in the chemical modification of polyolefins at high temperatures in extruders, such as chain transfer to polymer via primary and polymer radicals, β‐scission, double bond addition and bimolecular termination, affect chain scission, long chain branching, crosslinking and grafting. This brief review will discuss some of the work focused on the kinetics and mathematical modelling of these react

ISSN:0008-4034    

DOI:10.1002/cjce.5450690302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractPolymer alloys and blends represent one of the fastest growing sectors of the plastics industry. To a large degree, the emphasis has now shifted from developing blends in the reactor to their creation through melt mixing on processing equipment such as extruders. As a result, intense activity is now being directed at controlling two particularly important considerations during melt processing: interfacial interactions and dispersed phase morphology. In this review, recent developments and trends in these two areas will be examined.

ISSN:0008-4034    

DOI:10.1002/cjce.5450690303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free‐radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R&D environment is discussed in terms of a CAD package for polymerization proces

ISSN:0008-4034    

DOI:10.1002/cjce.5450690304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractConditions under which fouling (polymer deposition) occurs in tubular polymerization reactors were studied using bulk methyl methacrylate polymerizations at 70°. It was demonstrated that reactor orientation and flow direction have a significant effect on fouling behaviour. Natural convection becomes increasingly important as concentration gradients in the reactor increase. Using the optimum reactor configuration determined in the first part of the study, a feasible operating region for the reactor was established, thereby permitting selection of conditions which will prevent reactor fouling

ISSN:0008-4034    

DOI:10.1002/cjce.5450690305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA non‐Newtonian mixture of monomers, their copolymer and pigment was dispersed into water with emulsifier by a rotor‐stator homogenizer (Brinkmann Polytron). Volume median diameters d50of the droplets, measured by Coulter Counter or optical microscopy, were typically 4–20 μm; d50was about inversely proportional to monomer fraction (0.2 to 1.0), or to rotor speed (4000 to 11000 rpm). Increasing the emulsifier from 0.1 % to 3% roughly halved d50; volume fraction of organic phase had little effect. Turbulent dispersion theory (Calabrese et al., 1986a, b), adapted to non‐Newtonian drops, represented the data but with different numerical constants. A high geometric standard deviation, around 1.7 but increasing slightly as monomer fraction decreased, may be due to non‐uniform turbulence and to the complexity of breakup at high

ISSN:0008-4034    

DOI:10.1002/cjce.5450690306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractVarious aspects of the use of extended Kalman Filters for tracking the states of continuous emulsion polymerization reactors are investigated. The importance of introducing meaningful nonstationary stochastic states to account for unknown impurities, initiator efficiencies, modelling errors, etc. is illustrated. The robustness of these state estimators to unmodelled and unmeasured disturbances, to modelling errors, and to input errors is evaluated. A procedure for selecting an optimal set of on‐line sensors is presented. The emulsion polymerization of styrene‐butadiene rubber (SBR) is used as the example sys

ISSN:0008-4034    

DOI:10.1002/cjce.5450690307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe influence of different aluminum alkyls (diethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri‐n‐hexylaluminum, tri‐n‐octylaluminum and isoprenylaluminum) on the ethylene polymerization activity of a laboratory prepared high‐activity SiO2/MgCl2‐supported TiCl4catalyst has been investigated. A slurry reactor (decane diluent) was used for measuring rates of polymerization. The average molar mass, the breadth of the molar mass distribution, the polymerization activity, and the shapes of the activity‐time profiles, were strongly dependent on the nature of the aluminum alkyl. For several of the cocatalysts used, the catalytic activity approached a constant value after a certain amount of time under reaction conditions. In this constant activity region, a first‐order dependence of the polymerization rate on the monomer concentration was found for all of the systems examined. However, the activation energy of the polymerization reaction was found to depend strongly on the type of cocatalyst

ISSN:0008-4034    

DOI:10.1002/cjce.5450690308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractDramatic changes occur during the initial stages of olefin polymerization over heterogenous catalysts. As polymer accumulates, the catalyst fragments and the void space within the growing particle becomes filled with polymer. The changing monomer transport rate to the active sites, dissipation of heat and stress with the particle, and eventually, dispersion of catalyst fragments within the growing particle can control the polymerization. We focus on the changes in, and influence of, polymer, catalyst and void morphology during the nascent polymerization for silica supported chromium oxide catalysts. We find that the course of the polymerization depends on the initial stages yet is seldom considered in polymerization models. We review several years of morphological characterization that identify the important physical phenomena which occur during nascent heterogeneous olefin polymerization.

ISSN:0008-4034    

DOI:10.1002/cjce.5450690309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractOn présente un modèle de copolymérisation de l'éthylène et d'une α‐oléfine qui décrit la consommation des monomères et la qualité du polymère produit, á savoir Mn, Mw, Mz, la distribution des masses moléculaires, les indices de branchement court et de doubles liaisons. Le modèle suppose qu'il existe plusieurs types de sites actifs (2 ou 3) et ne fait pas intervenir de limitation diffusionnelle. On l'applique á la copolymérisation en masse de l'éthylène et du butène‐1 sous haute pression et haute température. Les paramètres sont identifiés grǎce á des essai

ISSN:0008-4034    

DOI:10.1002/cjce.5450690310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY