The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The structural characterization, by X-ray diffraction and solid-state 13 C n.m.r. CPMAS, of copolymers of propylene with small amounts of ethylene and 1-butene, synthesized with a single centre syndiospecific catalyst, is presented. The effect of the presence of comonomeric units on the polymorphic behaviour of syndiotactic polypropylene is discussed. In the as-prepared samples, the...
Blends of nylon 6 with the liquid crystal copolyester Vectra have been prepared from the melt with different compositions, and their thermal behaviour has been analysed by differential scanning calorimetry (d.s.c.) and X-ray diffraction (WAXS) using syncrotron radiation, as a function of temperature and thermal treatment. The structural properties of these blends have been found to be very sensitive...
The miscibility of poly(epichlorohydrin)/poly(N-vinyl-2-pyrrolidone) (PECH/PVP) blends was investigated by 13 C cross-polarization combined with magic-angle sample spinning and high-power dipolar decoupling (CP/MAS/DD) techniques. Intermolecular cross-polarization and the downfield shifting of the carbonyl resonance of PVP indicate intermolecular hydrogen bonding. 1 H T 1...
Macromolecular interpolymer complexes were prepared by blending concentrated equimolar solutions of chitosan and poly(4-N-methacrylamidobenzoic acid) and evaporation of the solvents. The products obtained presented the structure of interpolymer complexes as indicated by FTIR spectroscopy. The thermal treatment of the solid products at 120 o C gives rise to a partial dehydration together...
This study concerns the problems encountered in the molecular characterization of ultra-high molar mass (UHMM) hyaluronan samples. The determination of the molar mass distribution of UHMM polymers is fairly difficult. Shear degradation and non-newtonian flow are the main difficulties in the fractionation on SEC columns. Considering these difficulties, the samples have remained previously characterized...
The brittle-tough transition of rapid crack propagation in pressurised polyethylene pipes is examined. The transition is correlated with the presence of shear lips. Two new tests are described and then used to examine the mechanism of shear lip formation. The mechanism is found to be largely governed by the post-yield drawing behaviour of the polyethylene and is sensitive to both rate and temperature...
The well-defined α,ω-dibromopropyl polyisoprene-block-polystyrene-block-polyisoprene copolymer was prepared by coupling of corresponding triblock dianion end-capped with 1,2-diphenylethylene with a large excess of 1,3-dibromopropane. End-to-end ring closure of the α,ω-dibromopropyl triblock copolymer was performed by interfacial condensation between the aqueous phase (1,6-diaminohexane) and the organic...
A series of aromatic poly(1,3,4-oxadiazole)s, PODZs, was prepared either by direct polycondensation of dicarboxylic acids with hydrazine sulfate using the polyphosphoric acid/methanesulfonic acid mixture, or by thermal cyclodehydration of the corresponding poly(hydrazide)s. Various aromatic diacids containing flexible p-oxyphenylene joints and/or bulky isopropylidene or hexafluoroisopropylidene groups...
Magnetic orientation of poly(ethylene-2,6-naphthalate) [PEN], reported in the previous paper, was studied in detail. Birefringence, X-ray and infrared analyses were carried out on the samples quenched at different periods of the crystallization time during the crystallization at 255 o C in the magnet (6T). These analyses showed that the orientation observed in the birefringence measurements...
Macroscopic shrinkage behaviour and microstructural changes in PET as-spun fibres prepared by a normal cooling and by a 'Controlled Threadline Dynamics' (LIB) process have been investigated as a function of temperature. For normally cooled spun fibres, the shrinkage and microstructural changes may be respectively divided into two steps with increasing temperature. A significant shrinkage in the...
In our previous study, we proposed a new expression for the configurational energy of mixing taking into account non-random mixing effect and chain-length dependence of the polymer. But our model can not predict lower critical solution temperature (LCST) behaviours of liquid-liquid equilibria for binary polymer solutions.In this study, we extend our previous model to describe LCST behaviours of binary...
Nuclear magnetic resonance spectroscopy (n.m.r.), dynamic mechanical thermal analysis (d.m.t.a.) and AC impedance techniques have been used in combination to probe the effect of electrolyte composition in an archetypal solid polymer electrolyte (SPE). A series of solid polymer electrolytes (SPEs) based on a urethane-crosslinked trifunctional poly(ethylene glycol) polymer host containing dissolved...
The chain-end groups of the polypropylene (PP) polymerized without addition of molecular hydrogen over a MgCl 2 .TiCl 4 .dioctylphthalate/Et 3 Al catalyst system consisted of n-butyl, n-propyl, vinylidene and vinyl groups in addition to ethyl and i-butyl groups which were detected in the PP prepared under the same polymerization conditions except for the addition of diphenyldimethoxysilane...
Condensation of the dianion of the bisaminonitrile α,α'-dicyano-α,α'-bis(dimethylamino)-m-xylene (8) with bis[p-(p-fluorobenzoyl)phenyl] ether (9) and 2,6-dibromopyridine (12) yielded the corresponding new poly(bisaminonitrile)s poly{oxy-p-phenylenecarbonyl-p-phenylene-[α,α'-dicyano-α,α'-bis(dimethyl amino)-m- xylyl]-p-phenylenecarbonyl-p-phenylene} (10) and poly[α,α'-dicyano-α,α'-bis(dimethylamino)-m-xylyl-2,6-pyridinediyl]...
Well-characterized polystyrene macromonomers containing a norbornene unit at the chain end were prepared by capping living polystyrene with exo-5-norbornene-2-carbonyl chloride. The macromonomers were then ring opened polymerized using well-defined Schrock molybdenum initiators, Mo(N-2,6-i-Pr 2 C 6 H 3 )(OCMe 3 ) 2 (CHR) where R is CMe 3 or CMe ...
A new biodegradable poly(l-aspartic acid-co-poly(ethylene glycol)) having pendant amine functional groups was synthesized by the melt polycondensation reaction of prepolymer prepared from N-(benzyloxycarbonyl)-l-aspartic acid anhydride (N-Z-l-aspartic acid anhydride) and poly(ethylene glycol). The synthesized polymer was characterized by FTi.r., 1 H n.m.r., d.s.c., g.p.c. and solubility....
Tough polymers (especially crystalline polyolefins) tend to show brittle behaviour, with a pronounced drop in fracture toughness, at high crack speeds. Since this effect is of special industrial importance, the High Speed Double Torsion test has been developed to measure it. Extracting fracture resistance data from the test demands accurate dynamical stress analysis of the specimen, but bulk strains...
The cationic polymerization of N-vinylcarbazole (NVC) can be initiated directly by montmorillonite (MMT) The polymerization has been studied with MMT in solid phase and NVC at melting temperature (> 64 o C) or in benzene solution at 50 o C. By repeated benzene extraction of the PNVC-MMT reaction product, an intercalcate of PNVC in MMT has been isolated. I.r. spectral analysis...
Two mesogenic monoepoxides, nematogenic 4-(2,3-epoxypropoxy)-4'-ethoxy-biphenyl (1) and smectic-A 4-butoxyphenyl-4-(2,3-epoxypropoxy)-benzoate (2) were synthesized and reacted with 4,4'-diaminobiphenyl (3), or 4-aminophenyl-4-aminobenzoate (4) to obtain model compounds for the chain extended and branched intermediates (cross-link sites) formed in the amine curing of epoxides. All epoxy/amine-adducts...
Different ABS systems, produced by means of different polymerisation techniques (emulsion and mass polymerisations) and with different microstructural features were characterised and studied. Elastoplastic fracture mechanics tests were performed in order to compare the effects of the different morphologies of the dispersed phase on the mechanical responses. The plastic deformation mechanisms that...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.