摘要:

AbstractSorption isotherms of nonionic dyes with two amino groups (one anthraquinone dye and two azo dyes) on various polymers from water were measured at 40–90°C (Nylon‐6 and cellulose film) and at 95°C (polyester microfiber). The isotherms were curved, convex to upward, in the range of low dye concentrationCsin water and almost linear in the range of medium to saturatedCs. The isotherms measured at low temperature (40°C for cellulose, 40–60°C for Nylon‐6, and at 95°C for polyester) were satisfactorily described by considering three concurrent modes of sorption. They are Nernst type partitioning and bimodal Langmuir sorption (sorption by the higher affinity sites with a small saturation value and that by the lower affinity sites with a large saturation value). However, for the sorption of the anthraquinone dye and one azo dye by Nylon‐6 film at high temperature (80–90°C), the amount of dye sorbed by the high affinity site decreased to negligibly small. Accordingly, the isotherms were expressed well by simple dual‐sorption model. © 1995

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330201

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry and torsional braid analysis investigations of the phase diagram ofcis‐1,4‐polyisoprene/polybutadiene blends as a function of the polybutadiene microstructure were reported by several authors. Polybutadienes containing a high vinyl content were shown to be miscible withcis‐1,4‐polyisoprene on the DSC spatial scale, whereas polybutadienes containing a low vinyl content were immiscible. In this article, we used variable‐temperature determinations of1H NMR free induction decays and low‐temperature, high‐resolution solid‐state13C NMR measurements of proton spin‐lattice relaxation times in the rotating frame to probe the phase behavior of thecis‐1,4‐polyisoprene/polybutadiene blends at the smaller spatial scale of the NMR technique. Blends ofcis‐1,4‐polyisoprene with a polybutadiene having a large number of vinyl 1,2 linkages appeared to be miscible on the molecular scale, in spite of small regions in which the polybutadiene component is not uniformily dispersed in the other polymer. On the contrary, blends in which the polybutadiene has a low content of vinyl 1,2 sequences were phase separated over the whole temperature range considered and no intermixed regions could be detected. The limiting case was observed with the polybutadiene containing 33 wt % vinyl 1,2 units, for which miscibility on a molecular scale is highly dependent on the blend composition. ©

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330202

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of drawing on creep parameters (modulus, viscosity, and retardation time) of polyoxymethylenedrawn fibers were examined on the basis of a series‐parallel, four‐element, mechanical model. These parameters increased with the draw ratio. The change in the modulus was the same between the series and parallel components. This was true also for the viscosity, although the change in the viscosity was much greater than that in the modulus. This means that the series and parallel components are deformed in the same mode by drawing. The parallel viscosity increased with elapsed loading times according to an experimental power function; this was also derived from the usual rate equation for viscosity change in the amorphous component. In contrast, the series viscosity remained unchanged over the short creep range due to an extremely larger value than that of the parallel. © 1995 John Wiley&Sons,

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330203

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe interaction of small molecules such as cyclohexane, tetrahydrofuran, and acetonitrile with styrene‐divinylbenzene copolymer gel beads were investigated by13C‐NMR spectroscopy. When the gel content was 0.1–0.3 g/mL, the13C‐NMR spectrum of the solvent displayed two peaks. A sharp peak at lower magnetic field was assigned to the free solvent, and a broad one to the solvent affected by the gel. This signal splitting is attributed to the upfield shift caused by aromatic rings of styrene units in the polymer chain. The nitrile carbon of acetonitrile showed the largest upfield shift. The mobility of small molecules in gel beads was also investigated using the nuclear magnetic relaxation method. In the case of good solvents for gel beads, the mobility was affected by the cross‐linking density, whereas poor solvents exhibited little dependence of the cross‐linking density. © 1995 John Wil

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330204

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractA study was undertaken of the effect of sample preparation conditions, especially moisture content, annealing conditions, and degree of neutralization, on the dynamic mechanical properties of poly(styrene‐co‐sodium methacrylate) ionomers. Water plasticizes the ionic cores; however, very small amounts of water do not affect the cluster glass transition mechanism. The study of the annealing effect showed that the morphology of ionomers is fixed during sample molding. No clustering was observed in samples below a degree of neutralization of 50%, possibly due to a decrease in the lifetime of the multiplets. The 50 and 75% neutralized samples showed weak clustering, with the cluster tan δ peaks shifting to higher temperatures with increasing degree of neutralization. The addition of neutralizing agents causes an increase in the size of multiplets; as a result, the strength of the electrostatic interaction between ion pairs increases. The 100–150% neutralized samples showed identical tan δ peaks and also very similar SAXS peaks. Therefore, it is speculated that excess NaOH resides in or near the multiplets and does not affect the electrostatic interaction between ion pairs. The 200–300% neutralized samples showed increased flow above the clusterTg, as well as a strong small‐angle upturn in the SAXS profile. In agreement with previous results, it appears that in these materials, the excess NaOH resides in the hydrocarbon phase in the form of NaOH crystals, which can act as sites on which the carboxylate ion pairs can reside temporarily; the binding, however, is believed to weaken at high temperatures, which allows flow to occur. The 200% overneutralized Ba2+sample showed the clusterTgat much higher temperatures than the 100% neutralized sample, which implies that, for this sample, the stability of the multiplets is higher. © 1995 John Wil

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330205

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAliphatic polyamides (Nylon‐66 and a Nylon‐6, ‐66, ‐610 terpolymer) were isothermally precipitated from formic acid solution by immersing in an aqueous nonsolvent bath or a solvent/nonsolvent mixture. Depending on the composition of the polymer solution and nonsolvent bath, phase separation by nucleation and growth can be initiated for a liquid‐liquid phase separation process, a crystallization process or a combined process. Under certain conditions, crystallization of Nylon‐66 results in a membrane with a uniform skinless microporous structure that was rapidly wetted by water. In contrast, liquid‐liquid phase separation produces a polyamide film with largely unconnected cellular voids that is as a result not wetted by water. © 1995 John W

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330206

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAn analysis is presented, which describes the isothermal ternary diffusion process encountered in the formation of the aliphatic polyamide membranes such as Nylon‐66 by direct immersion‐precipitation of a polymeric solution in a nonsolvent bath. A material coordinate is employed to derive the mass transfer equations for the membrane solution. The convective mass transfer in the coagulation bath is taken into account by solving the hydrodynamic boundary layer equations. Diffusion coefficients were measured and used to deduce ternary phenomenological coefficients. The computed results are found to agree with measured precipitation times and with membrane morphologies observed by scanning electron photomicrographs. © 1995 John Wiley&Sons,

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330207

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe room temperature phase of the physical/chemical vapor‐deposited statistical co‐oligomer VDF/TrFE(70/30) has been characterized by different experimental methods such as small‐angle x‐ray scattering, wide‐angle x‐ray diffraction, size‐exclusion chromatography, infrared absorption and optical refractometry. The characterization of the elastic properties was carried out using high‐performance Brillouin spectroscopy in connection with special scattering geometries. The co‐oligomer VDF/TrFE(70/30) was obtained by cracking the parent statistical copolymer and subsequently vapor depositing the shortened chains on highly oriented PTFE substrates (PIA‐technique). The room temperature phase of the resulting oriented waxy crystal mats of VDF/TrFE(70/30) is predominantly ferroelectric. The physical properties are very different to those of similarly PIA‐preparedn‐alkanes, perfluoroalkanes, and blockfluoroalkanes. The microstructure of VDF/TrFE(70/30) is interpreted in terms of partially crystalline nano‐sized structures giving rise to a marked freezing process below room temperature. ©

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330208

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractContrast for transmission electron microscopy (TEM) of microphase‐separated saturated hydrocarbon diblock copolymers has been obtained using ruthenium tetroxide (RuO4). This technique exploits differences in the rate of transport of the oxidizing stain in rubbery amorphous versus semicrystalline, or glassy, microdomains. Rapid quenching from above the melting (Tm), or glass transition (Tg) temperature is shown to preserve the equilibrium melt morphology in poly(ethylene)‐poly(ethyl‐ethylene) (PE‐PEE), poly(ethylene)‐poly(ethylene‐propylene) (PE‐PEP), and poly(vinylcyclohexane)‐poly(ethyl‐ethylene) (PVCH‐PEE) diblock copolymers; PE melts at 108°C, PVCH is glassy up to about 140°C, while PEE and PEP remain rubbery down to approximately‐20°C and −56°C, respectively. Treatment of ultrathin sections of the quenched specimens with RuO4vapor led to welldefined TEM images, that revealed microdomain type and order. These results are consistent with SANS data taken under equilibrium conditions.

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330209

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractInfrared spectroscopy has been used to determine the porosity of polymer nanofoams produced from block copolymers of an aromatic polyimide with either poly(propylene oxide) or poly(α‐methyl styrene). It is shown that, with an independent measurement of the film thickness, both the absorption bands and the interference fringes can yield an accurate measure of the void content. The results obtained are in quantitative agreement with density gradient methods. © 1995 John Wiley&Sons,

ISSN:0887-6266    

DOI:10.1002/polb.1995.090330210

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY