摘要:

AbstractIn the case of grafting by preirradiation method, the presence of air during preirradiation by gamma rays has practically no influence on the percent grafting, whereas the presence of water decreases the activity to a great extent. ESR studies of preirradiated cotton and rayon show that the active species for the grafting are not peroxides but free radicals even when the irradiation is carried out in air. The number of scissions of chemical bonds of the cellulose molecule by the irradiation is found to be practically independent of the degree of polymerization and microstructure of the initial cellulosic fiber; the presence of air also has no effect on the degradation. In the case of styrene grafting, breaking strength of single fibers remains substantially unchanged by the grafting, but the increase of denier by the grafting results in a drop of tenacity (g/den) of the single fibers. It is true that cellulosic fibers become hydrophobic by the grafting of styrene, but the tendency to absorb water calculated on the cellulose basis increases by the increasing percent graft. This may be the reason for the rather low wet tenacity of the styrene grafted cellulosic fibers.

ISSN:0449-2994    

DOI:10.1002/polc.5070370103

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe types of long‐lived free radicals formed in predried cellulose I and cellulose II, after irradiation in a nitrogen atmosphere at 25°C by γ‐radiation from 60Co, were resolved by selectively scavenging some of the radicals and then recording the ESR spectra generated. The effects of anhydrous ammonia (both gas and liquid), water, solutions of sodium hydroxide, and temperature of heating on the ESR spectra generated by the irradiated celluloses were recorded. Most of the free radicals formed in the irradiated celluloses are apparently trapped in the amorphous or less ordered regions of the cellulosic structure. About 70% of the radicals formed in irradiated cellulose I and about 90% of the radicals formed in irradiated cellulose II are scavenged by contacting the samples with water. The ESR spectra of the free radicals scavenged by water are almost identical for both irradiated celluloses. Contact of the irradiated celluloses with ammonia (liquid) scavenged most of the trapped free radicals. It also appears likely that the long‐lived free radical sites in the highly ordered regions in both irradiated celluloses are the same. As shown by the effects of orientation of irradiated cellulosic fibers in the magnetic field on the ESR spectra recorded, differences in spectra for the irradiated celluloses are probably related to conformations of the trapped radicals which are dependent on differences in crystal lattice types of cellulose I

ISSN:0449-2994    

DOI:10.1002/polc.5070370104

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe graft copolymerization of ethyl acrylate from methanol‐water solutions with γ‐irradiated cotton cellulose I and II was investigated by electron spin resonsance spectroscopy and by the formation of cellulose‐poly(ethyl acrylate) copolymer. The rate and extent of graft copolymerization reactions in these heterogeneous systems were dependent on conditions of storage of the irradiated celluloses prior to reaction, the composition of the methanol‐water solutions, reaction time, agitation during the reaction, and cellulose crystal lattice type. Agitation of the heterogeneous system during reaction decreased both the rate and extent of copolymerization. From water the extent of copolymerization of ethyl acrylate with irradiated collulose I was greater than with cellulose II; from methanol the extent of copolymerization with irradiated cellulose II was greater than with cellulose I. From methanol(40 vol‐%)‐water(60 vol‐%) maximum extent of copolymerization occurred with both irradiated celluloses; however, the extent of copolymerization was less with irradiated cellulose II than with cellulose I. The extent of copolymerization was directly related to the initial concentration of free radicals in the irradiated cellulose. However, a fraction of the radicals, about 10% of the maximum concentration in cellulose obtained at a dosage of 5.2 × 1019eV/g, was apparently in the highly ordered regions of the cellulosic structure. These radicals were not scavenged and did not initiate copolymeriz

ISSN:0449-2994    

DOI:10.1002/polc.5070370105

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe radiation induced grafting of monomers to cellulose using a variety of solvents by the mutual irradiation technique is discussed. The monomers studied were styrene, 15 substituted styrenes, methylmethacrylate, vinyl acetate, and the vinylpyridines. The types of substituents examined included o‐, m‐, and p‐halogen derivatives, also the alkylstyrenes and certain methoxy monomers. The effect of wetting and nonwetting solvents in the grafting reaction was also investigated. A Trommsdorff effect (accelerated grafting) has been observed in certain systems at low doses and dose rates. The effect of oxygen, nitrogen, and vacuum on the Trommsdorff peak is discussed. The role of additives in the grafting of styrene is considered. The additives examined include aromatic and nonaromatic compounds, also typical free radical scavengers such as hydroquinone and thiourea. With certain additives sensitization is observed. A model for the grafting mechanism is proposed involving charge transfer bonded species. The role of energy transfer and free radical processes in the copolymerization reaction is also disc

ISSN:0449-2994    

DOI:10.1002/polc.5070370106

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe grafting of the cellulose with vinyl monomers in the absence of the radical initiators was studied. The nature of the grafting medium and of the promoters was varied. The obtained copolymers have been investigated by chemical and physical‐chemical methods. The mechanism of the grafting was discusse

ISSN:0449-2994    

DOI:10.1002/polc.5070370107

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

年代:1972

数据来源: WILEY

摘要:

AbstractA review is attempted of the inorganic redox systems in the context of free radical graft polymerization. Metal ion‐H2O2 redox systems are considered as part of the spectrum of such inorganic and organic reagents used for the purpose. It is emphasized that the chemistry of these latter systems in particular is much like the radiation chemistry of aqueous solutions caused by high energy ionizing radiations. On the other hand, these systems involve low energy and therefore are less damaging to the substrate and relatively more specific. The reactivity of free radicals in these systems varies subtly with the system and the medium. It is observed that only ceric ion method and [Fe(II); Fe(III)] ‐H2O2 system are most successful in grafting onto cellulosic materials. Attention is paid to the features which makes these systems so useful. Concrete results from ESR study are presented which underline the nonspecific nature of various free radical producing systems including radiati

ISSN:0449-2994    

DOI:10.1002/polc.5070370108

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

年代:1972

数据来源: WILEY

摘要:

AbstractGraft copolymerization of polar vinyl monomers onto cellulose in the presence of oxidizing agents, ceric ion, and radiation has been presumed to be solely the result of propagation from radical sites generated on the cellulose. The uncatalyzed polymerization and graft copolymerization of methyl methacrylate in the presence of cellulose and water has been presumed to involve the formation of a cellulose‐water‐monomer complex with the resultant generation of a covalently bonded monomer radical which then propagates in the usual manner. The formation of grafted alternating copolymer from the radiation induced polymerization of styrene‐acrylonitrile and butadiene‐acrylonitrile, the radical catalyzed polymerization of styrene‐methyl methacrylate and styrene‐acrylonitrile‐ZnCl2as well as the uncatalyzed polymerization of butadiene‐methyl methacrylate in the presence of cellulose and water indicates the participation of comonomer charge transfer complexes in the graft copolymerization. It is proposed that cellulose acts as a complexing agent for the activation of acceptor monomers and as a matrix for the alignment of acceptor monomer complexes (A*−A‐cellulose‐water) and donor‐acceptor comonomer complexes (D+−A‐cellulose‐water). Polymerization of the complexes is initiated spontaneously or by radicals generated on the cellulose although the latter do not become incorporated into the polymer chain. Graft copolymerization results from termination of the growing polymer chains on cellulose by i

ISSN:0449-2994    

DOI:10.1002/polc.5070370109

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

年代:1972

数据来源: WILEY

摘要:

AbstractSome esters like metallated cellulose monoethyl malonate were used as macromolecular initiators for grafting of some vinyl monomers and the obtained products were characterized.

ISSN:0449-2994    

DOI:10.1002/polc.5070370110

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

年代:1972

数据来源: WILEY

摘要:

AbstractNew amino aromatic esters and ethers of cellulose were synthetized. Then grafting processes were performed on these derivatives by using acrylic, methacrylic and N‐vinyl pyrolidone monomers. Finally, chemical structure and physicomechanical properties were determined. Industrial experiments proved the utility of this grafting metho

ISSN:0449-2994    

DOI:10.1002/polc.5070370111

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe mutual irradiation technique in vacuo has been used to study the grafting (G) of styrene to regenerated cellulose film in a dioxan/water medium and the simultaneous homopolymerization (H). The initial rates RGand RHare both found to be directly proportional to the concentration of styrene, but the ratio of the rate constants kP2/ktis ca. 105times greater in grafting than in homopolymerization (58 cf. 3.3 × 10−41. mole−1sec−1). Bimolecular termination is indicated in both cases by the observed dependences of RGand RHon (intensity)0.5. The degrees of grafting utilized to determine RGwere shown to be apparent values only, since extraction of ungrafted cellulose yielded products in which the true degrees of grafting were all some ten times greater.From ESR spectra of cellulose irradiated in air a value of 1.6 was derived for G (radical) and there was some evidence of scission. Corresponding spectra of cellulose irradiated in vacuo gave G(radical) = 2.9, but no evidence of scission. The radical, formed by hydrogen abstraction, was shown to be located at the C1atom. However, evidence for scission in cellulose irradiated (in the presence of dioxan/water) in vacuo and in air was provided by measurements of intrinsic viscosity, values of 13.5 and 24.6, respectively being derived for G(sci

ISSN:0449-2994    

DOI:10.1002/polc.5070370112

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

年代:1972

数据来源: WILEY