摘要:

AbstractThe rheological behaviour of cellulose diacetate films preliminarily oriented in ethanol has been studied under conditions of constant stress and constant load in the range of temperatures from 40 to 60°C. The analysis of the flow curves shows that the observed effects can be explained in terms of “a negative longitudinal viscosity”. This is probably caused by the occurence of a mesophase in the material. A method for measuring of “the negative longitudinal viscosity” is

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340701

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractA thermodynamic analysis of nucleation during the crystallization of oriented polymer melts was performed. It is based on a model of the structure of the amorphous state of polymers and takes into account the generalized effect of such defects as loops and tie‐chains on the end surface of the nuclei being formed. Equations are derived for various parameters characterizing the process of orientational crystallization. It is found that loops or folds which can remain on the nucleus surface even at high degrees of orientation may lead to an increase in the potential barriers to nucleation and a decrease in the melting temperatur

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340702

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractA theory of the superheating phenomenon, i.e. the increase of the melting temperatureTm, of oriented samples of flexible‐chain polymers with the heating rate, is presented. Calculations show thatTmis higher on heating under isometric conditions than under equilibrium conditions. Analysis of the kinetics of melting suggested that the reason for superheating is the incomplete relaxation of amorphous chain parts. Moreover,Tmincrease with the heating rate tending to the value ofTmunder isometric condition

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340703

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractDie anionische Acrylnitril‐Polymerisation wird in unpolaren Lösungsmitteln untersucht. Als Initiatoren dienen unabhängig synthetisierte aktive Vinylpyridin‐Oligomere bzw. ‐Polymere (2‐VP, 4‐VP). Die Effektivität der Initiierung und die Höhe des Umsatzes werden in Abhängigkeit von der Natur des Initi

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340704

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractKinetics and topochemistry of emulsion polymerization of styrene or its copolymerization with acrylonitrile in the presence of seed polybutadiene latex and tert‐dodecyl mercaptan (TDM) as a molecular weight controller depend upon two basic factors: reaction of TDM and potassium persulphate as initiator increasing initiation rate and a possibility of radical output from micelles and particles as a result of chain transfer acts. The latter predominates because in the majority of cases the process rate decreases when concentration of TDM increases. When polymerization is carried out without the formation of new particles it allows to increase the efficiency of monomer grafting on polybutadiene. Simultaneously the molecular weight of the non‐grafted polymer is controlled on the preset le

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340705

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractAuf der Grundlage von Lichtstreumessungen im Weit‐ und Kleinwinkelbereich wurde eine Teilchengrößenanalyse an monomodalen PVC‐Dispersionen unterschiedlicher Teilchengröße und Polydispersität durchgeführt. Die Bestimmung der Verteilungsparameter der untersuchten Systeme erfolgte nach einer einfachen Auswertemethodik im Rahmen der Rayleigh‐Debye‐Näherung aus den experimentellen Streukurven mit anschließender Mie‐Korrektur für mittlere TeilchengrößenD>300 nm. Anhand eines Vergleichs der ermittelten und korrigierten Verteilungsparameter mit den Ergebnissen einer Anpassung theoretischer Streukurven an die experimentellen Streuwerte wurde eine Abschätzung der Genauigkeit der durchgeführten Teilchengr

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340706

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractResults of an IR spectroscopic investigation of polypropylene fibres modified by a polymeric additive are presented. A reproducible process of KBr pellet preparation from fibre samples is described. The ratio of absorbances of a characteristic absorption band of the additive and a structurally independent absorption band of polypropylene was analyzed. The fibre diameter significantly influences the absorbance ratio. The content of additive and its distribution was determined in fibre samples prepared under various mixing conditions in the extruder.

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340707

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractEin neues kinetisches Modell zur Beschreibung der Emulsionspolymerisation von Monomeren, die zur Kettenübertragung neigen, wird vorgestellt. Als Grundlagen für die Modellentwicklung dienten Diffusions‐ und Wahrscheinlichkeitsbetrachtungen. Es werden u. a. Beziehungen zur Berechnung der mittleren Radikalzahl pro Teilchen, der Radikalkonzentration in der wäßrigen Phase, der kinetischen Kettenlänge und der Teilchenneubildung ang

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340708

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractThe structural changes in the formation of coatings from oligomers depending on the chemical composition and the structure of the oligomers, the adhesive strength between polymer and support, the curing conditions and the kind of modifying additives, were investigated. The oligomers are shown to be associated systems. The polymerization proceeds in several steps and is accompanied by a non‐monotoneous increase of the physico‐mechanical characteristics due to chemical reactions in the initial stage, particularly within the supramolecular structure, and subsequent formation of chemical bonds between the structural elements. As a consequence of the adhesive interaction with the surface of the support an irregular structure is formed in perpendicular direction of the film. The number of curing steps and the irregularity of the structure are increased by addition of active fillers and the formation of coatings from mixed oligomers. The curing process involves physicochemical processes of various kind (removal of solvent, polymerization reaction with air oxygen etc.). The modification of oligomers by additives promoting the formation of a homogeneous ordered structure in the liquid phase and its fixation in the coatings improves essentially the mechanical properties of the coatings and reduces the time of their format

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340709

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractChanges of the fine structure of wool caused by treatment with vapour and aqueous solution of ammonia are analysed. Crystallinity degree and crystallite size were found to increase, while the general orientation, as characterized by birefringence and texture, was reduced. Character and intensity of these changes depend first of all on the medium used and on its concentration.

ISSN:0323-7648    

DOI:10.1002/actp.1983.010340710

出版商:Akademie Verlag GmbH    

年代:1983

数据来源: WILEY