摘要:

AbstractThe addition of tricresyl phosphate,N‐phenyl‐2‐naphthylamine, and 4,4′‐dichlorodiphenyl sulfone to polysulfone causes changes in thermal and mechanical properties of the glassy mixtures associated with antiplasticization, i.e., reduction in glass transition temperature and increase in stiffness. These changes are also found to be accompanied by reductions in sorption of carbon dioxide and the permeability coefficients for helium, carbon dioxide, and methane at low diluent concentrations with reversal of these trends at higher levels as also occurs for the mechanical properties. Detailed analyses of data for carbon dioxide are given in terms of the dual sorption and mobility models often used for glassy polymers. The mobility for gas transport was found to decrease with diluent addition. The major cause for the decreased sorption is the reduction in glass transition temperature accompanying addition of the diluents. The changes in transport behavior approximately parallel the changes in mechanical behavior. These trends are not even qualitatively correlated with estimates of the excess volume changes associated with addition of the diluents to po

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250501

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe propensity for various diluents to cause antiplasticization of poly(phenylene oxide) was examined and compared with similar responses for polysufone. Of the diluents used, none resulted in significant stiffening of poly(phenylene oxide) at 35°C relative to what was observed for polysulfone in an earlier paper. However, these diluents did cause substantial reduction in gas sorption levels and permeability coefficients. The latter is consequently a more sensitive indicator of changes in molecular motions of glassy polymers caused by diluents. The permeability response of adding low molecular weight diluents is compared with that of adding a high molecular weight polymer, polystyrene, to poly(phenylene oxide). The data were analyzed and interpreted along lines used in the companion paper for polysulfone

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250502

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractPrevious papers have shown that antiplasticization of polysulfone and poly(phenylene oxide) by low molecular weight diluents is accompanied by substantial reductions in permeability to gases like helium, carbon dioxide, and methane because of reduced mobility in the glass. These effects are not explained even qualitatively by the extent of volume contraction on mixing for these mixtures. However, as shown here, a simple free volume treatment provides an excellent correlation of these effects. Free volume was computed from measured specific volume and an estimate of the volume at the absolute zero of temperature of the material from a group contribution method. Application of this approach to the mechanical stiffening associated with antiplasticization is suggested. The basis and limitations of this analysis are discussed.

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250503

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractCompatibility or miscibility of a polyethersulfone (ICI: Victrex 100P) and a tetrafunctional epoxy (Ciba‐Geigy: MY‐720), cured with an aromatic anhydride, has been studied using scanning electron microscopy, x‐ray microanalysis, and dynamic mechanical spectroscopy. Fracture toughness of epoxy and a blend of epoxy and polyethersulfone has been measured using three point bend tests (ASTM: E‐399‐81). Fracture surfaces were examined by x‐ray microanalysis for detecting concentration of sulfur, present in polyethersulfone, in the matrix and precipitated phase. The influence of the morphology of the epoxy/polyethersulfone blend on its fracture toughness and toughening mechanism has been studied. Fracture toughness values of unmodified and modified cured epoxy resin were evaluated as a function of test

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250504

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe influence of the molecular weight of the primary chains and of crosslinking density on the viscoelasticity of polyisoprene and polybutadiene vulcanisates has been examined by subjecting these materials to double‐step extensions in opposite directions. The stress peaks caused by these sudden retractions are well described by a model derived from the Curro–Pincus treatment of the disengagement pendant chains from a net of obstacles. These topological interactions do not appear to be derived from discrete chain entanglements but from diffuse interspersion effects between the pendant chains and the chemical junctions of the netwo

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250505

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe solubility and mesophase behavior are investigated for block copolymers of poly(p‐benzamide) (PBA), the polyterephthalamide ofp‐aminobenzhydrazide (PABH‐T), and PBA and poly(m‐phenylene isophthalamide) (MPD‐I) dissolved inN,N‐dimethylacetamide (DMAc) containing 3% LiCl. The block copolymers, whose synthesis and characterization were described in the previous paper in this series, included samples prepared by the two‐step and multistep copolycondensations. The first of these methods yields a considerable amount of the flexible homopolymer (PABH‐T) and also some of the rigid homopolymer. The flexible homopolymer can be removed from the block copolymer by extraction with dimethyl sulfoxide (DMSO), whereas precipitation may offer a way to remove the rigid homopolymer. The results observed for the block copolymers are compared with those for the homopolymers and mixtures of homopolymers. The apparent solubility of the PBA/PABH‐T block copolymers obtained by the two‐step method is unusually large but decreases toward the value observed for mixtures after the flexible homopolymer had been extracted with DMSO. Labile adducts involving PABH‐T and/or the block copolymer appear to be capable of forming a single mesophase. This offers a most interesting approach to the preparation of composite materials involving rigid

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250506

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe dynamic mechanical properties of homogeneous copolymers of ethylene with 1‐butene, 1‐octene, and 1‐octadecene prepared by means of a vanadium‐based catalyst system have been determined. The 1‐butene copolymers show α′ and α transitions in the 20–60°C temperature range, whereas the 1‐octene and 1‐octadecene copolymers show single α transitions. The intensity of the β transition increases with comonomer content in 1‐butene and 1‐octene copolymers and also with the amount of interfacial material present. In ethylene‐1‐octadecene copolymers, this intensity is comparatively low, even though there is about 20% interfacial material present. The implications of these results with regard to the nature of inte

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250507

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThermochromism and solvatochromism of solutions of poly(3‐alkylthienylenes) are reported. The experimental results indicate the presence of two coexisting phases: polymer in solution and polymer in microcrystalline aggregates. From the concentration independence of the thermochromism, it is concluded that the transition is fundamentally driven by a single chain mechanism, and that the aggregation (microcrystallization) of the poly(3‐alkylthienylene) macromolecules can occur only after the single chain conformational change has occur

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250508

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractDiffraction patterns of oriented blends of isotactic polypropylene (iPP) and polyethylene (PE) published recently by several authors are analyzed on the basis of a unique epitaxial relationship between the iPP and PE crystal lattices. The contact planes are (100)PEand (010)iPP, and the PE chains lie at 50° to the iPP chain axis, parallel to the helical path of the iPP helices, which is formed by rows of side‐group methy

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250509

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe band texture of a thermotropic cellulose derivative, trifluoroacetoxypropylcellulose, was studied by optical microscopy. The texture consists of parallel, long, thin, black lines when viewed between crossed polarizers with one polarizer parallel to the shear direction. These lines are perpendicular to the shear direction. Their optical properties indicate that the molecules are cooperatively oriented and this orientation director alternates from 0° to ±45° from the shear direction, with most of them at ±45°. This band phenomenon is identical to that observed with thermotropic nematic copolyes

ISSN:0887-6266    

DOI:10.1002/polb.1987.090250510

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY