摘要:

The stereoregularity of poly(methyl methacrylate) obtained with complex bases in various solvents was determined by1H-NMR spectroscopy. Polymethyl methacrylates produced by complex bases are mostly hetero and/or syndiotactic and obey Bernoullian statistics.

ISSN:0022-233X    

DOI:10.1080/00222338208056502

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Photopolymerization of methyl methacrylate (MMA) onto nylon 6 fiber by UV radiation in alcoholic solutions of water-methanol, water-ethanol, and water-n-propanol in the presence of fructose was investigated. The effects of monomer concentration, time of polymerization, fructose concentration, and effect of media have also been studied. Graft add-on (GAO) % greatly enhanced with an increase in monomer concentration and time. With fructose concentration it increases up to 15 mmol/L of fructose and thereafter falls. The GAO in the media is in the following order: W + M + F > W + E + F > W + P + F(W = water; M = methanol; E = ethanol; P = n-propanol). A probable mechanism has been suggested. It appears that the active site is formed on MMA which abstracts an H-atom from the nylon 6 backbone, giving rise to graft of MMA by mutual combination.

ISSN:0022-233X    

DOI:10.1080/00222338208056503

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The composition of copolymers formed at 50°C in ethyl acrylate/ styrene/azo-bis-isobutyronitrile/benzene systems of different composition was investigated. The experimental composition data (based on the elementary analysis of copolymers) were evaluated by the η-ζ transformation method. Finite monomer conversions were taken into account. The classical composition equation was found to describe the system under investigation. The reactivity ratios arep1= 0.152 ± 0.006;p2= 0.787 ± 0.023. The free radical copolymerization of ethyl acrylate and styrene has been investigated in benzene solution at 50°C. Our results on the initiation kinetics were disclosed in our recent publication [1]. Now we are reporting on our studies concerning the composition of ethyl acrylate/styrene copolymers.

ISSN:0022-233X    

DOI:10.1080/00222338208056504

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The copolymerization kinetics of the ethyl acrylate/styrene/azo-bis-isobutyronitrile/benzene/50°C system was found to deviate from the classical rate equation of copolymerization. The experimental results could not be interpreted by the diffusion theory, the penultimate effect, or the theory of electron donor-acceptor complexes. Our kinetic data were consistently described by the theory of hot radicals, and the 13 parameters characteristic for the copolymerization system were determined from an adequate number of data at different compositions by a nonlinear least-squares method.

ISSN:0022-233X    

DOI:10.1080/00222338208056505

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Graft copolymerization of methyl methacrylate (MMA), acrylonitrile (AN), and acrylamide (AA) on cellulose of low degrees of oxidation (effected through periodate treatment) was studied under photoactivation with visible light in limited aqueous systems. The degree of oxidation of the cellulose sample given in terms of copper number was between 0.25 (for the native cellulose) and 46. Increasing degree of oxidation initially produced higher overall % conversion or rate of polymerization. Overall grafting effects, i.e., % grafting and grafting efficiency, were also generally higher in oxycellulose than in unmodified cellulose. Effects of variations of time of polymerization, initiator content, and monomer content on overall grafting were also studied, and related data for the three monomer systems have been presented and compared. Percent grafting as high as 300–500% and grafting efficiency of the order of 80–95% were easily obtained.

ISSN:0022-233X    

DOI:10.1080/00222338208056506

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The radical copolymerization of vinylidene chloride (Vc, M1) with 3(2-methyl)-6-methylpyridazinone (I, M2) was carried out in benzene, ethanol, phenol, and acetic acid at 60 and 80°C. The monomer reactivity ratios were found to vary with the reaction conditions. The linear correlationships were obtained by plotting the values of log r1against those ofVC˭O andVC˭C of monomers determined in the solvents.

ISSN:0022-233X    

DOI:10.1080/00222338208056507

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Combustion is a complex phenomena involving a multiplicity of variables. Some important variables measured in flame tests follow [1]. In order to characterize ignition, such related parameters as ignition time, ease of ignition, flash ignition temperature, and self-ignition temperature are measured. For studying the propagation of the flame, parameters such as distance burned or charred, area of flame spread, time of flame spread, burning rate, charred or melted area, and fire endurance are measured. Smoke characteristics are studied by determining such parameters as specific optical density, maximum specific optical density, time of occurrence of the densities, maximum rate of density increase, visual obscuration time, and smoke obscuration index. In addition to the above variables, there are a number of specific properties of the combustible system which could be measured. These are soot formation, toxicity of combustion gases, heat of combustion, dripping phenomena during the burning of thermoplastics, afterglow, flame intensity, fuel contribution, visual characteristics, limiting oxygen concentration (OI), products of pyrolysis and combustion, and so forth. A multitude of flammability tests measuring one or more of these properties have been developed [2]. Admittedly, no one small scale test is adequate to mimic or assess the performance of a plastic in a real fire situation. The conditions are much too complicated [3, 4]. Some conceptual problems associated with flammability testing of polymers have been reviewed [5, 6].

ISSN:0022-233X    

DOI:10.1080/00222338208056508

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The application of peroxydiphosphate coupled with bivalent metal ions like Fe(n) and Mn(II) to induce graft copolymerization of methyl methacrylate onto cellulose fibers by varying the concentrations of monomer, initiator, acid, reducing agent, solvents, and temperature has been studied. The rate of grafting increases progressively with increasing monomer and reducing agent concentrations. The rate of grafting also increases with peroxydiphosphate concentration up to 10.0 × 10−3M and with sulfuric acid concentration up to 9.0 × 10−2M after which it decreases. The effects of addition of some solvents and temperature on graft yield were also studied. The effect of modified cellulose on the rate of grafting was also studied. Both systems have been investigated under identical conditions. A larger percentage of grafting was observed in the case of Mn(II) than of Fe(II). A suitable kinetic scheme has been developed, and rate equations have been derived.

ISSN:0022-233X    

DOI:10.1080/00222338208056509

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Asymmetric inductions have been achieved in the free radical additions of (1)l-menthyl mercaptoacetate to such prochiral olefins as crotonic acid, methyl crotonate, and a-methylstyrene (enantiofacedifferentiation), and (2) achiral thiols to g-menthyl and isobornyl crotonates (diastereoface differentiation).

ISSN:0022-233X    

DOI:10.1080/00222338208056510

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Mixed ligand complexes of bis(thioformohydroxamato) cobalt(II) with 1,10-phenanthroline and 2,2-bipyridyl have been synthesized, and their magnetic and spectral characteristics are reported.

ISSN:0022-233X    

DOI:10.1080/00222338208056511

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor