摘要:

AbstractThe properties of many kinds of solid material (e.g., ionic crystals, quartz, etc.) appear to have only a tenuous correlation with those of the isolated individual atoms or molecules of which they are made. In macromolecular substances, however, thanks primarily to the great strength of covalent bonds, such correlations are strong and indeed essential to fundamental understanding of structure‐property relationships. With certain exceptions, such as polypeptides and polynucleotides with their remarkable helix‐coil transformations, the conformational properties of macromolecules in liquid or amorphous environment are only secondarily dependent on the nature or concentration of diluents; and in many cases the molecular conformation observed in the crystalline state is also the most stable conformation of the isolated chain. There are also strong correlations between the rates of conformational change for isolated macromolecules in dilute solution and various non‐equilibrium properties of polymeric substances in bulk.During the past decade, great progress has been made in the analysis and prediction of macromolecular conformations. Detailed accounts may be found in the books by VOLKENSTEIN, by BIRSTEINand PTITSYN, and by FLORY. By combination of several types of experimental evidence with semi‐empirical and theoretical considerations, it has been possible to construct fairly reliable potential energies governing the conformations of a wide variety of chain molecules. An important simplifying feature of the results is that for many purposes it is sufficient to focus attention on the various minima of the potential energy, corresponding to the so‐called rotational‐isomeric states. Another essential feature is that as a rule one finds strong interdependence of the rotational states of adjoining bonds in the chain backbone; a simple example is found in the “pentane effect” for paraffin chains, which renders highly improbable the occurence of two successivegaucherotations of opposite sense. An important exception is seen in polyamides, where the essentially rigid planarity of the amide link allows independence of the rotations of the immediately adjacent bonds. Inclusion of other rigid or semi‐rigid elements in the chain backbone, such as the rings in cellulose and in terephthalate polyesters, leads to similar effects, but in detail each chain issui generis. The conformations of chains bearing asymmetric centers (e.g.,PVC, polypropylene) depends strongly on tacticity and stereoregularity.For the discussion of non‐equilibrium properties at a fundamental level, the maxima (barriers between minima) of the conformational potential energy also play an essential role, but at present most theories of viscoelasticity, for example, are based on less realistic models, such as beads‐and‐springs, random‐flight chain, KRATKY‐PORODwormlike chain, etc. The elaboration of these models and their relation to the detailed molecular structure is current

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220101

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractStarting with a nondefective bundle of macromolecules (the ideal crystal) one gets a low‐defective bundle (the real crystal) by introduction of stable defects (kinks, torsional defects, jogs and folds) which are compatible with the intra‐ and intermolecular potential. The cooperative statistical treatment of this bundle reveals – under a certain condition – a first order transition, connected with a jump in defect‐concentrations. This transition corresponds in most cases to the melting of the polymer, in some polymers (e. g. trans‐polybutadiene) it splits up into a solid state transition (large kinkblocks without torsions) and the melt transition (small kinkblocks, torsional defects, jogs and folds). In the case of polyethylene the bundle model has been shown to explain quantitatively the transition data (Tm, ΔHm, ΔVm) as well as the expansion coefficient and the compressibility of the melt together with their dependence on static pressure. The calculated short‐range order also is in accordance with the X‐ray and electron diffraction data. By introduction of cooperatively arranged gauche‐areas (for planar molecules) the meander model is established which guarantees the isotropy of the melt. Assuming the bundle diameter (calculated to about 50 Å which is in the range of the observed superstructure in amorphous polymers) to be constant during crystallization a lamellae‐structure results in which the meander thickness is determined by the crystallization temperature. This two phase meander model is in accordance with the experiment and implies the key to the understanding of molecular motions in polymers. This will be shown by a quantitative molecular interpretation of the relaxation processes (secondary, main and crystalline relaxation) in a polymer as well as of its deformation behaviour (parae

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220102

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220103

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractIm mechanischen Verhalten teilkristalliner Fasern überlagern sich die elastischen und plastischen Eigenschaften der amorphen und der kristallinen Anteile. Die Art der Überlagerung hängt von der Kolloidstruktur ab, d. h. von der gegenseitigen räumlichen Kristallitanordnung sowie von den Mechanismen der Kraftübertragung von Kristallbereich zu Kristallbereich.In einem qualitativen Überblick werden einige der z. Z. diskutierten Modelle für die Kolloidstruktur sowie für die Kraftübertragung durch interkristalline Kettensegmente (tie molecules) zusammengestellt und mit den mechanischen Fasereigenschaften in Zusammenhang gebracht. Vergröbernd kann gesagt werden, daß das elastische Verhalten im wesentlichen durch die Eigenschaften der amorphen Bereiche gegeben ist, während das plastische Faserverhalten (das u. a. bei der Texturierung und dem Knitterverhalten eine wesentliche Rolle spielt) in höherem Maße zusätzlich auch von der Eigenschaft der Kristallbereiche abhängt. Schallgeschwindigkeitsmessungen liefern wesentliche Informationen zum Mechanismus der Kraftübertragung zwischen benachbarten K

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220104

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractThe development of the polymer chemistry during the last decade is characterized by the existence of several new methods of polymerization, e. g. the isomerization polymerization of aliphatic hydrocarbons, the oxidative catalytic polymerization of aromatics, the photochemical polyaddition, the 1.3 and 1.4 dipolar polycycloadditions, the two step polycondensation processes. Some of these methods have already been applied on an industrial scale. Simultaneously new catalytic procedures were discovered, some of which permit stereoregular copolymerization, and very recently stereo‐elective polymerization. These different aspects will be considered successively.The isomerization polymerization in which the chain growth is characterized by alternate addition isomerization steps, is illustrated by several examples, and compared to the polymerizations with previous monomer isomerization, as in the case of β‐olefins.The stepwise oxidative coupling of different 2.6 disubstituted phenols, with oxygen in the presence of amine complexes of copper salts is considered from kinetic and structural point of view and compared with the oxidative FRIEDEL‐CRAFTS reaction on aromatic hydrocarbons.Two types of photochemical polyadditions are considered on the basis of the cyclomerization reaction, in which cyclobutane rings are formed by dimerization of olefins (in solution and in the solid state), and of the reductive dimerization, e. g. of bisarylketones into polypinacols.The use of 1.3 dipolar cycloaddition for the synthesis of heterocyclic rings containing polymers is illustrated and some properties of these polymers are described. Similarly the 1.4 DIELS‐ALDER cycloaddition is exemplified by the synthesis of polyphenylenes as described from biscyclopentadienones or (and) bis‐phenylenebispyrones and diethinylbenzene.Only short mention will be made on the synthesis of thermally stable polymers by polyheterocyclization, e. g. single strand benzoxazole‐ and benzthiazole‐imide copolymers and Kapton fibre, and double strand ladder polypyrrolone‐anthrachinone fibres. New catalytic procedures are finally briefly commented as far as they offer possibilities for the synthesis of new polymers and regular copolymers. Some properties of these new polym

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220105

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractPoly‐α‐amino acid fibre being rich in β‐form has a silky quality. The fibre being rich in α‐form becomes woolly. When there is a strong interaction force through side chains of poly‐α‐amino acid molecules, the polymer solution is not spinnable regardless of the film forming ability. As it is difficult to spin a strong fibre directly from a polymer in α‐form, the spinning solution should contain some parts of random coil in the α‐form and the fibre molecules should be oriented in a parallel with the axis by stretching. Finally, most of the remaining β‐ or random‐parts should be retransformed into the α‐form. The β‐form of poly‐L‐alanine is most stable and most analogous to silk, but most of β‐form in poly‐L‐leucine stretched fibre is transformed into the α‐form in boiling dioxane and the woolly character appears. The character of poly‐α‐amino acid fibres seems to depend on the contents of α‐ and β‐form. Poly‐L‐leucine fibre in the α‐form is stable in boiling water and it seems to be unnecessary to introduce a cystine bridge into the fibre to maintain a woolly character. By copolymerizing a small amount of methionine

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220106

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractAn outline is given of the developments and the present knowledge of the flame resistance of fibres. The principles of flame‐resistance are only partly – mainly qualitatively – understood. There is certainly room for much more fundamental research.The development of flame‐ resistant textile fibres was a highly pragmatic one. Further progress will be largely determined by public regulations and legislations.In the field of flame‐retarding additives to existing materials a number of spectacular successes have been achieved, but they relate mainly to cellulose fibres.The development of new flame‐resistant synthetic fibres has made great progress in the last ten years. A very interesting new achievement is the development of a nonflammable chelated polymer, poly‐(terephthaloyl‐oxalic‐bisamidrazone), which is here described for the first time and which may well prove to be the first representative of a new class of polym

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220107

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractMaterials having gained importance over the past decade are – in addition to the developments of high temperature‐resistant polymer fibres – various types of fibrous materials, being distinguished by their resistance to temperatures exceeding 1000°C. These materials are in general inorganic compounds formed into fibres by special shaping methods. The distinguished properties of some of these fibre types are high mechanical strength, oxidation resistance, electrical conductivity and light weight, apart from their temperature resistance.The main processes used for their manufacture are: drawing of very fine filaments, vapour deposition of compounds in the form of fibres, and spinning of inorganic filaments by the viscose process.This paper discussed metal fibres and fine filaments as well as oxide, carbide and nitride filaments of the third and fourth group of the periodic system of elements, as far as they are of importance.Also discussed will be fibres of boron, silicon carbide, silicon nitride and boron carbide being representative of the vapour deposition process and also fibres of aluminium oxide, titanium oxide, silicon dioxide being representative of the viscose process, as well as other types.Only a small amount of fibres are being produced by the mentioned processes. Carbon fibres are made in general by full thermal decomposition of infusible, organic fibres in inert atmosphere. Their manufacture will be detailed together with their properties and various fields of application.Concepts of the chemistry of thermal decomposition will be illustrated and also the connections between the structure of the basic materials and those of carbon fil

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220108

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractEs werden die Korrelationen zwischen der Struktur und den mechanischen Haupteigenschaften von hochorientierten linearen Polymeren und Schichtpolymerstrukturen (Fasern, Folien, nadelartigen Kristallen) dargelegt. Für das Studium einer strukturellen Abhängigkeit der mechanischen Eigenschaften werden als typisches Beispiel verschiedene lineare Polymere (Polyäthylen, Polypropylen, Polyvinylalkohol, Polyacrylnitril, Polyamide, Polyäther, Cellulose, aromatische Polymere) und Schichtstrukturen (Graphit, Bornitrid, Siliziumkarbid) betrachtet, die einen verschiedenen Molekülbau und verschiedene Werte intermolekularer Wechselwirkung besitzen. Es wird eine Reihe von physikalisch‐mechanischen Kenndaten der Fasern aus den oben erwähnten Polymeren ihrer Struktur gegenübergestellt.Es werden die Methoden zur Berechnung von Festigkeits‐ und Elastizitätseigenschaften hochorientierter Polymermaterialien auf Basis ihrer Strukturkenndaten angeführt. Die mechanischen Grenzwerte der orientierten Polymersysteme sind genügend hoch. Die theoretische Festigkeit (bei 0° K) liegt, für verschiedene Polymere im Bereich von 600 bis 13 000 kp/mm2.Auf der Grundlage der Angaben über die Temperatur‐ und Zeitabhängigkeit der Festigkeit von hochorientierten Polymeren werden die Werte einer maximal erzielbaren Festigkeit, d. h. die Festigkeitswerte der Proben mit einer idealen Struktur bei einer bestimmten Temperatur und Dauer der Deformation abgeschätzt. Diese Werte betragen ca. 1/3 bis 4/5 vom theoretischen Festigkeitswert (bei Raumtemperatur und Deformationsdauer ca. 10 Sekunden).Die Größe von Grenzelastizitätsmoduln der orientierten linearen Polymeren erreicht 25 000 kp/mm2und der von Schichtstrukturen uber 100 000 kp/mm2.Ferner werden experimentelle Angaben über physikalisch‐mechanische Eigenschaften von Polymermonokristallen und praktisch erzielte mechanische Eigenschaften von Chemiefasern zusammengestellt sowie Korrelationsverhältnisse zwischen der Festigkeit und den Elastizitätseigenschaften von orientierten Polymermaterialien betrachtet.Es werden auch Angaben über die Anisotropie mechanischer Eigenschaften von orientierten Polymeren als Funktion der Anisotropie ihrer Struktur und der Heterodynamik von energetischen Wechselwirkungen angeführt.Zum Schluß werden die Hauptbedingungen analysiert, die die Verwendbarkeit verschiedener Polymerer zur Herstellung von Hochmodul‐ und hochfesten faser

ISSN:0003-3146    

DOI:10.1002/apmc.1972.050220109

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY