摘要:

AbstractThe thermal degradation of polytetrafluoroethylene has been studied in a closed reaction system over a temperature range from 480 to 580°C. The initial stages of gas formation follow a first order law. If the dimerization of monomer to octafluorocyclbutane is taken into account, the rate constants for polymer degradation can be represented by k = 6.3·1019e−78,000/RTmi

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850101

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractA study was made of the spectroscopic changes produced in thin polyvinyl chloride films when irradiated in vacuum at room temperature with UV, and γ‐radiation. At doses up to 2·1022quanta/g. PVC of UV radiation (2200–3400 Å.), or 100 Mrad of γ‐rays, the kinetic plots for increased absorbance throughout the UV‐visible spectrum brought about by these two radiations are fully superimposable. In terms of absorbed energy units needed to produce the same spectroscopic changes (and hence the same conjugated unsaturation or the same HCl evolution), it was thus found that γ‐radiation is about 13 times as efficient as UV radiation. This result, for films containing some 3 to 5% residual ketonic solvent, correlates very well with corresponding literature data on the photo‐ and radiation chemical evolution of HCl from solvent‐free PVC. The quantum yield for the former process is shown to be independent of wavelength below 3400 Å., which is the effective photochemical cut‐off wavelength. The area under the UV‐visible spectrum, as well as the solar absorptivity, reaches a maximum value after a UV dose of ab

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850102

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractHigh resolution nuclear magnetic resonance spectra of a number of a number of samples of poly(vinyl chloride) have been obtained. The methinyl proton spectrum consists of three quintets which have been assigned to isotactic, heterotactic and syndiotactic triads. Determinations of the relative numbers of each triad in several samples of polyvinyl chloride indicate that the degree of stereoregularity is not strongly affected by changes in polymerization solvent or temperature.The various conflicting analyses which have been previously suggested for the polyvinyl chloride methylene proton spectrum are also discussed. The 100 Mc.‐spectrum of poly(α‐deuterovinyl chloride) indicates that the methylene proton spectrum consists of two overlapping triplets from isotactic and syndiotactic diads. The possibility that the methylene proton spectrum is complicated by the presence of branching in poly(vinyl chloride) is also sugge

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850103

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractHigh resolution NMR‐spectra of polypropylene, poly(3,3,3‐d3‐propylene), and poly(1,1‐d2‐propylene) have been obtained and analyzed. Although the methinyl proton spectrum is not influenced by the stereochemical configuration, differences do appear in the methylene proton spectrum which can be related to tacticity. By comparison of calculate methylene proton spectra assuming different ratios of isotactic and syndiotactic diads with the observed spectra, it is possible to obtain information about the tacticity of polypropylene samples. This method of obtaining information about polymer configuration should be generally useful for polymers which have complex NM

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850104

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractHigh resolution NMR‐spectra of poly(vinyl alcohol) samples have been obtained and analyzed. The methinyl proton spectrum consists of three quintets whose intensity can be related to the number of isotactic, heterotactic, and syndiotactic triads. The methylene proton spectrum consists of two triplets from isotactic and syndiotactic diads. The NMR‐spectra indicate that poly(vinyl alcohol) prepared by hydrolysis of poly(vinyl acetate) is essentially atactic, poly(vinyl alcohol) obtained from poly(vinylt‐butyl ether) is predominately isotactic, and poly(vinyl alcohol) from poly(vinyl trifluoroacetate) is slightly syndiotactic. The influence of conformation on the NMR‐spectrum of poly(vinyl alcohol) is also briefly di

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850105

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractN‐Vinylsuccinimid und N‐Vinylpyrrolidon besitzen ein Eutetikum bei dem Molverhältnis 3,4/6,6. Beim Eutektikum ist die Copolymerisationsgeschwindigkeit größer als in Ausgangsgemischen, deren Zusammensetzung von der des Eutektikums abweicht. Die Zusammensetzung des entstandenen Copolymeren stimmt in jedem Fall mit der des Eutektikums überein. Die Zusammensetzung des in fester Phase entstandenen Copolymeren weicht von derjenigen ab, die der aus den relativen Reaktionsfähigkeiten bestimmten entsprechen würde. Dies beweist, daß die physikalische Struktur des festen Zweikomponentensystems die Zusammensetzung des entstandenen Copolymeren bestimmt. In unterkühlter, flüssiger Phase ist die Copolymerisationsgeschwindigkeit des Gemisches, dessen Zusammensetzung der des Eutektikums entspricht, noch größer als in fester Phase; die Zusammensetzung des entstandenen Copolymeren liegt zwischen derjenigen des in flüssiger Phase und der des im festen Eutektikum entstehen

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850106

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractFor the polymerization of norbornene, three modes of reaction have been known: vinyl polymerization (I) and ring‐opening polymerizations givingtrans(II) andcis(III) double bonds.In the present study, the polymerization by modified ZIEGLERtype catalysts was carried out. Modification was obtained by the addition of several LEWISbase compounds as the third component to the binary system of metal alkyl and titanium tetrachloride. The AlEt3/TiCl4(2.5/1), AlEt3/TiCl4(1/1), and LiAlEt3Bu/TiCl4(2.5/1) systems induce the norbornene polymerization giving polymers consisting mostly of the units (I) + (II), (I) and (II), respectively. These three systems were transformed by the addition of some LEWISbases into the species which give high molecular weight polymers consisting exclusively of the ring‐opened units (II) and (III). The modification by LEWISbase is prominent in the region of the base/TiCl4ratio of 2 t

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850107

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractCopolymerization of phenyl isocyanate with ethylene oxide was investigated under several conditions. The polymers obtained with AlEt3alone or the AlEt3‐H2O system as catalyst were found to be composed of two types, that is polyethylene oxide and alternate copolymer of phenyl isocyanate with ethylene oxide. The copolymer was found to have acetalic units in the polymer chai

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850108

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractIt was found that tetrafluoroethylene copolymerizes with isobutene and a crystalline, alternating copolymer could be obtained over a wide range of the monomer composition in the copolymerization.The copolymerizations were carried out by60Co‐γ‐ray irradiation at −45 and −78°C. The monomer reactivity ratios, r1(C4H8) and r2(C2F4), were determined from an elementary analysis of the copolymers to be 0.2 and 0 at −45°C., respectively; while the reactivity ratios at −78°C. could not be determined exactly, but were roughly estimated to be r1(C4H8)≅r2(C2F4)≅0.The alternating tendency of this copolymer may be due to the opposite polarities of the monomers, that is, the electron with‐drawing property of the fluorine atoms of tetrafluoroethylene and the electron‐donating property of methyl groups of isobutene.It may suggested from the monomer composition dependence of the copolymerization rate that the termination reaction takes place mainlyviaa degradative chain transfer of the growing radical to isobutene at a high isobutene concentration

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850109

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY

摘要:

AbstractDer Einfluß des Rührens und der Kammervolumina auf den osmotischen Druck an semipermeablen und nicht‐semipermeablen Membranen wird an Polyäthylenglykolen unterschiedlichen Molekulargewichtes in Lösungsmitteln hoher und niedriger Viskosität an Cellophan‐600‐, Ultracella fein‐ und Glas‐Membranen untersucht. Das Kammervolumen hat bei semipermeablen Membranen entgegen der in der Literatur vertretenen Meinung keinen Einfluß auf die Einstellgeschwindigkeit, kann sich aber bei gewissen Auswertetechniken bei nicht‐semipermeablen Membranen auswirken. Rühreffekte sind bei der von uns verwendeten dynamischen Methode (Messung zur Versuchszeit 0) bei Cellophan 600 und Glas nicht feststellbar, wohl aber bei der sehr durchlässigen Ultr

ISSN:0025-116X    

DOI:10.1002/macp.1965.020850110

出版商:Hüthig&Wepf Verlag    

年代:1965

数据来源: WILEY