摘要:

AbstractDynamic mechanical thermal analysis and calorimetric studies are reported on blends of poly(ethylene oxide) (PEO) with poly(N‐vinyl pyrrolidone) (PVP) between 80% and 40% PEO. DMTA curves show a peak corresponding to a phase of pure PEO and another peak which can be attributed to blended material. The calorimetric analysis shows an appreciable melting point depression and a marked decrease in the crystallization rate as the PVP content increases. The melting point depression follows the Nishi‐Wang equation, giving an interaction parameter of −0.50. These studies suggest the existence of microphases in the

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271301

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractOrganic materials in general and polymers in particular have traditionally been considered as to be phosphors and have been ruled out as materials which could be useful in dosimetry of ionizing radiations by thermoluminescence. Some results reported during the past decade suggested possibilities of organic phosphors with good thermoluminescence characteristics. Experiments were undertaken to exploit the various possibilities. The results show that “crystalline polymers” can have adequate thermoluminescence properties to be useful in dosimetry. It is suggested that further studies on thermoluminesence in crystalline polymers and highly drawn fibers of high polymers will prove fruit

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271302

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractSolid‐state coextrusion has been used to prepare uniaxially drawn films from isotropic poly(ethylene 2,6‐naphthalate) (PEN) of a minimum degree of crystallinity (ca. 5%) both below and above its glass transition temperatureTg. The onset of cold crystallization (Tc) of the drawn films has been studied as a function of the extrusion temperature (ET) and the draw ratio (EDR). It has been shown thatTcdecreases markedly on draw, as much as 95°C, and, at constant draw ratioTcgoes through a minimum in theTgregion. For undrawn PEN, annealing below 153°C has no significant effect onTc. To evaluate the crystallization rate constant (k) and the activation energy (Ea) of the drawn specimens, a nonisothermal DSC procedure has been used. With increasing EDR,kincreases markedly andEagoes down over threefold compared with the undrawn polymer. At high ET, strain‐induced crystallization has also been shown to play an important role in loweringEafor cold crystallization. Thermal shrinkage aboveTmindicates a high elastic recovery, underlining the efficiency of deformation, ca. 93%, achieved by solid‐state co

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271303

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA Raman‐mechanical technique was used to study the relationship between stress distribution and fiber orientation in model composites. Our experimental data generally were consistent with most simplistic mechanical models. A more complete analysis, using the Eshelby equivalent inclusion method, fitted our experimental data exceptionally well. For large applied strains, compressive failure occurred for fibers which were oriented at high angles relative to the draw direction. This occurred because of the lateral shrinkage associated with the matrix when the sample was stretched. The effect of fiber end geometry on the stress distribution for these misaligned fibers was the same as observed earlier. Tapered‐end fibers generally carried loads more efficiently in composites than blunt‐end f

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271304

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractCO2sorption and transport were investigated for the polyimide prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐diaminodiphenyl sulfone (DDS). The morphology of films did not change on annealing above the glass transition temperature and remained amorphous unlike the polyimide prepared from BPDA and 4,4′‐oxydianilline (ODA). This seems to be due to the strong hindrance to rotation of the sulfonyl linkage. Sorption and transport data were analyzed according to the dual‐mode model. Solubility, diffusion, and permeability coefficients at 20 atm and 80°C for BPDA‐DDS polyimide were substantially equal between as‐cast and annealed films and were 1.7, 2.2, and 3.7 times greater, respectively, than for the as‐cast films of the BPDA‐ODA polyimide. The higher solubility was due to larger values of the Henry's law solubility constantkD, Langmuir capacity constantC ′H, and the Langmuir affinity constantb. The sorption and transport properties were compared with those for amorphous glassy aromatic polymers including other polyimides. The relation ofk,C ′H,b, and the diffusion coefficients in the Henry's law population and the Langmuir population (DDandDH) with other properties of the polymers were discussed. ValuesDDandDHfor BPDA‐DDS polyimide were much larger than expected from

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271305

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe free energy of an inhomogeneous polymer‐polymer‐solvent system has been obtained by extending Debye's approach for a polymer‐solvent system. Our ternary result reduces to Debye's result for a binary polymer‐solvent system and to McMaster's result for a binary polymer‐polymer system at the appropriate limits. Like Debye's work, we neglect the entropic gradient contribution to free energy. Based on the ternary result we suggest a generalized expression for the free energy of multiple polymers dissolved in a common solvent. This expression is used to find the free energy of an inhomogeneous polydispersed polymer‐sol

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271306

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThis article describes dielectric properties of complex Zn(II) salts of ethylene‐methacrylic acid copolymer (5.4 mol% methacrylic acid) withn‐hexylamine. In all samples, the β′ relaxation near 340 K and γ relaxation near 170 K are observed. These are assigned, respectively, to micro‐Brownian molecular motion of long segments aboveTgand to local molecular motion of short segments belowTg. The dielectric results indicate that ionic clusters are not formed in thes

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271307

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA method in which the dissolution of a miscible polymer pair is traced in a differential scanning calorimetry cell is described. The polymer blend is initially prepared as an heterogeneous system with microdomains of one component embedded in the continuous matrix of the second polymer. Annealing the system in the DSC cell above the glass‐transition temperature causes a spontaneous mixing of the polymer pair which can be observed by the progressive shift of theTgs of both components until they merge. The time scale for dissolution and aspects of mass‐transport phenomenon are thus determined for the specific blend, cellulose acetate‐poly(styronephosphonate ester). Rather sharp progressive shifts of theTgs are shown to prevail without significant broadening of the transition curve (ΔTg). Mass‐transport analyses supported by electron microscopy observation of the blend, before and after annealing, suggest that the domain sizes remain nearly unchanged and the physicochemical makeup of the phase boundary interfaces determines the time scale of dissolution in the system. A model from which mean‐value diffusion coefficients are calculated for both components at different annealing temperatures i

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271308

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA procedure is described which allows α,ω‐dicarboxylic acid polybutadiene to be end‐neutralized using a stoichiometric amount of a transition metal acetate. In a nonpolar solvent, the solution viscosity of this new class of carboxylato telechelic polymers depends on the neutralization degree of the acid end groups in such a way that the progress of the neutralization may be compared with that of a polycondensation reaction. In contrast to Cu(II), the Zn, Ni, Co, and Mn carboxylate endgroups promote very early gelation of toluene solutions when the polymer concentration increases. The particular behavior of Cu(II) can only be explained by a difference in the coordination number compared with the other elements of the first transition series. The dependence of the solution viscosity on the atomic number of the element cannot be completely accounted for so far. Nevertheless, an electrostatic association of the cupric carboxylate end groups can be disregarded, since the solution viscosity is independent of the polarity of the solvent in the range of 2.28

ISSN:0887-6266    

DOI:10.1002/polb.1989.090271309

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY