ISSN:0323-7648    

DOI:10.1002/actp.1995.010460401

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractSupramolecular structures based on 4‐(3,5‐dioxo‐1,2,4‐triazolidin‐4‐yl) benzoic acid (U4A) units act as effective junction zones in functionalized polybutadienes, resulting in the formation of thermoplastic elastomers. The dynamics on a molecular scale of the phenyl rings have been probed by2H‐NMR. In the polymeric system, there are three spatially separated environments, which are reflected in the mobility of the polar units. Phenyl rings which are incorporated in the structures are either rigid or undergo 180° phenyl flips. The small fraction of free functional groups move isotropically and their mobility is coupled to the dynamics of the polybutadiene matrix. In two model compounds, where the polymer backbone is replaced by a 1‐butenyl (tBu‐dU4A) or a C12H24‐chain (C12‐dU4A), the packing of the single molecules is more perfect, resulting in better‐defined dynamics of the molecules. The one‐dimensional2H‐NMR spectra can be described quantitatively assuming a distribution of correlation times over 3 decades for the C12‐dU4A and 2 decades for the tBu‐dU4A, respectively. From the average jump rates the activation energies are determined as 101 kJ/mol and 102 kJ/mol. The geometry of the motional processes is defined by the environment in the clusters up to the order‐disorder transition temperature as determined by DSC. The two‐dimensional spectra of the model compounds show an elliptical exchange pattern, indicating well‐defined slow 180° phenyl fl

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460402

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractCrystallization of polytetrafluoroethylene (PTFE) from the melt state has been studied by wide angle X‐ray scattering (WAXS), small angle X‐ray scattering (SAXS) and differential scanning calorimetry (DSC) experiments, supported by scanning electron microscopy (SEM) observations. Isothermal crystallization of PTFE (between 315 °C and 325 °C) is analyzed and compared with PTFE cooled at 1 °C/min taken as the reference. We establish a TTC (time, temperature, crystallization) diagram and point out the time and temperature dependence of both crystallite thickness and crystallinity. It appears that the crystallization occurs in a very narrow temperature range. We assign the morphological changes to different crystal growth regimes in the range of

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460403

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThree triblock copolymers of nylon‐6 (Ny6) and aromatic poly(sulfone ether) (PSuE) were investigated relative to their morphology and their thermal properties. Generally, the nylon blocks of the three Ny6‐PSuE‐Ny6 samples were very short (between 5 and 16 monomer units). Heterogeneous, microphase‐separated morphologies could be observed for all samples, independent of the processing conditions, i.e., solvent casting or melt cooling. However, the process conditions were highly influential on the formation of the supramolecular structures (i.e., spherulites), especially when the crystallizable block wa

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460404

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe characteristic parameters for three different equation‐of‐state (EOS) theories have been determined for polystyrene and low‐molecular weight polyisoprene using pressure‐volume‐temperature (PVT) data. Basically two procedures for the calculation of characteristic parameters were applied. The characteristic parameters were calculated, firstly, from coefficients of expansion, compressibilities and densities, and secondly, by fitting the corresponding EOS toPVTdata minimizing the sum of the squares of the differences between experimental and calculated pressures. The characteristic parameters obtained by the two methods are compared with regard to their ability to describePVTdata. A comparison of the three different EOS theories reveals that, for describing polymeric liquids, the modified cell model of Dee and Walsh is superior to the theory of Flory, Orwoll and Vrij as well as to the lattice fluid theory of Sanchez and Lacombe. Finally, formulae are given to convert the characteristic parameters from one theory into those o

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460405

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe applicability of the coil‐strand‐transition model to describe the deformation of hard elastic polymers was studied by deformation and relaxation tests of hard elastic polyethylene and hard elastic polypropylene samples in different liquids. It was found that within the model the calculated values of the fibril diameter, the contribution of surface stress and the total stress are in agreement with measurements. The dominance of energetic contributions to the stress was also confir

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460406

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractA study was made of the changes in density, thermal resistance and mechanical and dielectric properties of a number of epoxy polymers cured at high hydrostatic pressure. The possibility of controlling characteristics under pressure is shown. The most important is the change in the glass‐transition temperature; the effect of pressure on the mechanical properties and thermal resistance is smal

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460407

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractPhenyl glycidyl ether (PGE) as well as ε‐caprolactam (CL) can be polymerized by cationic initiators. For the present work, Mg(ClO)4ċ2 H2O was used. The formation of different oligomer structures depends strongly on the reaction conditions if both monomers are oligomerized in a one‐pot reaction. HPLC,13C‐NMR and FT‐IR studies showed that not only were homooligomeric products of PGE formed, but also products from phenyl glycidyl ether and ε‐caprolactam. Homopolymerization of CL does not occur. Mixtures of diglycidyl ether of bisphenol A (DGEBA) and CL in the presence of catalytic amounts of magnesium perchlorate yield clear and homogeneous castings withTg=96 to 100°C. These networks include<10% dioxane‐ and water‐ext

ISSN:0323-7648    

DOI:10.1002/actp.1995.010460408

出版商:Akademie Verlag GmbH    

年代:1995

数据来源: WILEY