摘要:

AbstractAdvances of radical initiation systems and their initiation mechanisms in vinyl polymerization through peroxycompound and amine systems as well as photo‐induced charge transfer initiation in the presence of amine are briefly reviewed which is concerned with some generalization regarding to the role of amine in the form of aminium radical in such vinyl radical polymerizatio

ISSN:0258-0322    

DOI:10.1002/masy.19920630105

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

ISSN:0258-0322    

DOI:10.1002/masy.19920630106

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractTwo methods for modification of polymer surfaces by photoinitiated grafting have been developed and applied to films and fibers of synthetic polymers, e.g. polyethylene and polypropylene with acrylic monomers. In the batch process the substrate is enclosed in a cell containing initiator and monomer vapor. UV light through a quartz window initiates the grafting reaction by exciting the initiator (e.g. benzophenone). The grafting reaction is slow (1 to 3 min) due to the inefficient transfer of initiator and monomer through vapor phase. In the continuous process the substrate is presoaked in a solution of initiator and monomer and then drawn into a reactor “on line” where the substrate is irradiated by UV light through a quartz window. The grafting takes place in the very thin surface layer of solution on the substrate. The grafting efficiency is high (70–80% of the polymer formed is grafted) and the process is rapid (5–15 s due to the efficient transfer of initiator and monomer through the liquid phase. The continuous surface grafting process is promising for industrial appli

ISSN:0258-0322    

DOI:10.1002/masy.19920630107

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractSix kinds of new ceric ion redox initiation systems for vinyl radical polymerization and two kinds of macromolecule graft copolymerization by ceric ion have been briefly reviewed in this paper. The initiators include ceric ion/acetanilide, ceric ion/alkyl phenylcarbamate, ceric ion/4‐methoxysuccinyltoluidine, ceric ion/aliphatic aldehyde, ceric ion/aromatic aldehyde, ceric ion/diketone systems. Macromolecules such as poly(ether‐urethane) and macromolecules having active pendant groups were selected for graft copolymerization with acrylamide initiated by ceric

ISSN:0258-0322    

DOI:10.1002/masy.19920630108

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractSome itaconic acid derivatives were prepared and polymerized, in which itaconic acid (IA),β‐monoalkyl itaconates (mRI), dialkyl itaconates (DRI),N‐substituted itaconamates (IAE), itaconamides (IAm), itaconic anhydride (IAn),N‐alkylitaconimides (RII), andN‐(alkyl‐substituted phenyl)itaconimides (RPhII) are included. The polymerization reactivity was examined, and discussed in relation to the structure of the monomers. The structure and some properties of the resulting polymers were investigated. Some citraconic acid (CA) and mesaconic acid (MA) derivatives were also polymerized, and their reactivities were compared with the corresponding IA d

ISSN:0258-0322    

DOI:10.1002/masy.19920630109

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractHigh resolution ESR spectra of polystyrene radical at various conversion in the bulk polymerization have been determined. The propagation and termination rate coefficients during the whole process of polymerization were evaluated from the conversion and the propagating radical concentration determined by ESR. It was found that the propagating radical has two stable conformations. The reduction of the radical activity with the conversion is partly resulting from the wrapping effect which is due to the far slower segment relaxation and the very rapid propagation.

ISSN:0258-0322    

DOI:10.1002/masy.19920630110

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe Interval II kinetics and compartmentalization effect of emulsion polymerization of styrene with the seeds of five radii (r=40.2, 51.3, 76.5, 99.7 and 252.0 nm) have been studied. The kinetic parameters, i.e., the rate coefficients ρ, K and C which refer, respectively, to the entry of free radicals into latex particles, the exit of free radicals from the particles and the bimolecular termination of free radicals within the particles; nssand nss(thermal), the average number of free radicals per particle in the steady state and in the thermally induced background polymerization, respectively, are obtained. The propagating rate coefficient kp, the termination rate coefficient kt, as far as possible, are calculated in the runs.From this work, it can be concluded that the kinetic behavior, the kinetic parameters and the compartmentalization effect of emulsion polymerization are greatly influenced by the latex particle size

ISSN:0258-0322    

DOI:10.1002/masy.19920630111

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of polymeric network formation via free radical mechanisms is an attractive research area because there are many phenomena which are not well understood and in addition, the commercial potential for crosslinked systems is great. Recently, a large research/development program was initiated at the McMaster Institute for Polymer Production Technology (MIPPT) to investigate the fundamentals and applications of polymeric network, in particular, the kinetics of synthesis via free‐radical mechanisms and network characterization. The research on crosslinking involved both theoretical developments and experimentation. Herein is provided a comprehensive summary of this work.In the experimental polymerization, two comonomers, methyl methacrylate (MMA) / ethylene glycol dimethacrylate (EGDMA) and acrylamide (AAm) / N,N‐methylene bisacrylamide (Bis), as model systems were studied in considerable detail. Measurements included: monomer conversions, radical concentrations, sol/gel fractions, crosslink densities (equilibrium swelling and swollen‐state13C‐NMR) over the entire range of divinyl monomer levels as a function of polymerization time. In the polymer modification, high density polyethylenes were crosslinked using peroxides and γ‐radiation. For this system, crosslinking and chain scission occur simultaneously.In the theoretical studies, it was shown that in general, network formation by free‐radical mechanisms is highly irreversible requiring that the classical equilibrium gelation theories after Flory/Stockmayer be generalized. The general model which was developed using the pseudo‐kinetic rate constant method predicts the existence of a crosslink density distribution (crosslink density of a primary polymer chain depends on its birth time) with a variance which can vary widely depending on network synthe

ISSN:0258-0322    

DOI:10.1002/masy.19920630112

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractVarious factors affecting the molecular weight of poly ((vinylidene chloride)‐co‐(vinyl chloride)) were studied in the paper. Mathematical models correlating intrinsic viscosity of the copolymer with concentrations of 1,2‐dichloroethane and initiators, and temperature were proposed and may be used to control the molecular weight of the copo

ISSN:0258-0322    

DOI:10.1002/masy.19920630113

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe non‐steady state theory for the kinetics of free radical polymerization taking no account of gel‐effect is reviewed. Considering the facts that the monomer consumption in chain propagation is much higher than that in chain initiation and the rate constant of chain termination is much larger than that of chain propagation or transfer, a few very close approximations are introduced to solve the set of kinetical differential equations of free radical polymerization. The expressions for various molecular parameters, such as the molecular size function, the number‐ and weight‐average degrees of polymerization and the dispersity, are derived. In accord with the non‐steady state theory, the curves of free radical decay with reaction time or monomer conversion and the molecular parameters mentioned can be predicted from the reaction conditions. Several numerical examples

ISSN:0258-0322    

DOI:10.1002/masy.19920630114

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY