摘要:

AbstractPure and modified polycyanurates are known for about 20 years. Up to now an important number of different special products was developed. Composites which base on polycyanurate resins show a high thermostability, stability against humidity and chemicals, and excellent electrical insulating properties. The resins are used as adhesives, binders for laminates, casting resins, and for other applications.

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430601

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe temperature and frequency dependences of electric conductivity of hydroxyethylcellulose, carboxymethylcellulose, 2.5 cellulose acetate, and cellulose triacetate have been investigated in the temperature range from 20°C to 150°C and in the frequency range from 0.5 to 100 kHz. The studies are completed by DTA measurements. The glass transition temperature and the values of the activation energies have been determined and discussed with respect of the structure of the cellulose derivative

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430602

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe evaluation of the long periods and crystallite lengths of original and pretreated solvent spun cellulose fibres revealed that they consist of about 90% crystalline cellulose in the direction of the fibre axis. In the case of high wet modulus viscose fibres this percentage is only 50–60%. The intensity of the long period of solvent spun fibres is lower than that of the high wet modulus viscose fibres corresponding to a smaller difference between their crystalline and amorphous orientation factors. There is existing a significant correlation between this difference and the intensity of the long perio

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430603

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractPolyanion‐polycation interactions between the free base poly(ethylene imine) and poly(acrylic acid, sodium salt) were investigated in dependence on polymer concentration of the components. At very low polymer concentration between 0.003% and 0.15% we observed a small range of phase separation, because of predominantly non‐Coulombic interactions, determined by using a method combination, consisting of potentiometry, conductometry and turbidimetry. By increasing the polymer concentration no phenomena of phase separation could be observed but a significant viscosity increase above the level of the components in dependence on the molar ratio of cationic to anionic functional groups as well as the molecular weight of the components. The results of NMR spectroscopic investigations in combination with density measurements are discussed with regard to a model of interaction at high concentrati

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430604

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe characterization of polyelectrolytes is demonstrated by combination of different ultracentrifuge methods with laboratory as well as technical poly(diallyl dimethyl ammonium chloride) samples. Low speed sedimentation equilibrium in an analytical ultracentrifuge was used to determine the molecular weight averagesMwandMz. The method was shown to be applicable even in case of partly aggregated solutions and the amount of aggregates was established. Equilibrium sedimentation in a density gradient of a preparative ultracentrifuge allows to separate linear and branched parts. While structural uniform polymers are distributed in a Gaussian band, nonuniformities lead to deformations of distribution curves. With mathematical curve analysis structural portions can be determined.

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430605

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractPhysical properties of a new polymer blend obtained by mixing poly‐D(—)(3‐hydroxybutyrate) (PHB), a crystalline polymer with interesting properties of biodegradability and biocompatibility, with uncrystallizable atactic poly(epichlorohydrin) (PECH) were studied. PHB/PECH blends, obtained by casting solution, were analysed by thermomechanical and X‐ray analysis, viscoelastic measurements, and on the basis of strength and elongation measurements. It was concluded that the crystalline region of PHB plays an important role of crosslinks, and amorphous PECH filled between the crystalline regions plays a role of plasticizer. A single dynamic loss modulus, corresponding to the glass transition temperature, implies the miscibility between crystalline PHB and amorpho

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430606

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractLight scattering is employed to determine cloud point curves of polystyrene (PS)/poly(vinyl methyl ether) blends over a large range of PS molecular weights. All blends investigated display lower critical solution temperature (LCST) behaviour. The LCST shifts to lower temperatures and smaller PS contents with ascending disparity of the constituent's molecular masses. Thermodynamics of the blends has been rationalized in terms of an equation‐of‐state theory. Relevant parameters can be calculated. Both enthalpy of mixing and excess volume turn out to be negat

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430607

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractHydrogels (crosslinked polymers with a defined content of water) from hydrophilic methacrylates and perfluorobutyl methacrylate were prepared by radical polymerization, followed by swelling in buffered isotonic sodium chloride solution. The obtained hydrogel samples have been characterized by their linear expansion to hydration, weight‐percent hydration, refractive index, extractables, percent transmission of visible light, and oxygen permeability. Such hydrogels are interesting as contact lens material

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430608

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractAromatic poly(oxadiazole)s are a class of heterocyclic polymers that show excellent thermal and chemical stability. Also, their electrical and optoelectrical properties are of interest. Here, a short review is given about recent results in the field of aromatic poly(oxadiazole)s elaborated in our research groups that emerged from the former Institute of Polymer Chemistry in Teltow‐Seehof. New aspects are described regarding the technology of poly(oxadiazole) synthesis via the oleum route. In detail the structures of poly(p‐phenylene‐1,3,4‐oxadiazole) in solution as well as in solid state are described. Moreover, the electrochemical behaviour and the dynamic‐mechanical properties are

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430609

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe contribution of three and four scattering events to the third‐order concentration coefficientk3is evaluated up to order 0(11) of the reciprocal particle distance. A value ofk3=6.091 is obtaine

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430610

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY