bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclohexane‐polystyrene revisited
Authors: Kleintjens Ludo A. , Koningsveld Ronald , Chermin Hubert A. G. , Huggins Maurice L. 
Published: April 2007

AbstractA semi‐empirical interaction function previously used in the quantitative description of critical miscibility data for the system cyclohexane/polystyrene is reconsidered in terms of molecular parameters. The empirical part of the function has approximately the same magnitude as correction terms which, owing to the dependence of the average randomness of orientation of molecules and polymer segments on the composition of the liquid, have to be applied to the combinatory entropy of mixing. Such a treatment largely ignores excess volume effects. These have been quantitatively dealt with by Flory et al., who had to bring in an empirical entropy correction whose order of magnitude may prove to be compatible with the orientational entropy contributions mentioned above. A full treatment in terms of molecular parameters seems within reach, but this will have to take the variation of the segment density distribution with concentration into account.
Reactive polymers XIV. Hydrolysis of the epoxide groups of the copolymer glycidylmethacrylate — ethylenedimethacrylate
Authors: Hrudková Hana , Švec František , Kálal Jaroslav 
Published: April 2007

AbstractHydrolysis of the epoxide groups of the copolymer glycidylmethacrylate ‐ ethylenedi‐methacrylate in variously concentrated sulphuric acid solutions was studied. An approximate activation energy of hydrolysis, 41 kJ mol−1, was determined from the temperature dependences. For the sake of comparison the effect of pH on the degree of hydrolysis over the whole range of pH values was examined, and the importance of the results with respect to other reactions of the copolymer used was discussed.
Poly(mono n‐alkyl itaconic acid esters): Their preparation and some physical properties
Authors: Cowie John M. G. , Haq Zia 
Published: April 2007

AbstractA series of poly(mono n‐alkyl itaconic acid esters), with ester chain lengths varying from methyl to decyl, were prepared by emulsion polymerisation. The materials are all hard brittle glassy polymers at ambient temperatures and undergo a dehydration reaction in the range 430 K to 450 K. Dynamic mechanical measurements showed the presence of at least three other damping maxima: an Δ‐transition at 90−95 K, a δ‐transition at 190–200 K and a γ‐transition at 240–260 K. The ε is associated with motion in the hydrocarbon part of the side chain, while the δ and γ transitions are associated with relaxations involving the carboxyl and alkoxycarbonyl groups respectively. Glass transitions were only detectable in higher esters. The thermal stability of the polymers is also briefly discussed.
Some aspects of the thermal stability of poly(alkyl itaconic acid esters)
Authors: Cowie John M. G. , Haq Zia 
Published: April 2007

AbstractThe thermal stability of members of several series of polyitaconates has been assessed using thermogravimetric and thermal volatilisation techniques. From these data general degradation patterns have been established. The poly (di‐n‐alkyl itaconates) are stable up to 570K before chain breakdown occurs. The poly(mono‐n‐alkyl itaconates) are less stable and undergo a dehydration/de‐esterification reaction at 430K which results in the formation of anhydride structures. This reaction can be suppressed by the formation of the salts. In the copolymers, salt formation also leads to increased stability but the range of copolymers studied was too restricted to draw general conclusions about their thermal behaviour.
Kinetics of the epitaxy and the over‐growth of polyoxymethylene from molten state on needle‐like single‐crystals
Authors: Iguchi Masatoshi , Watanabe Yasushi 
Published: April 2007

AbstractKinetic studies have been made on the over‐crystallisation of polyoxymethylene on needle‐like crystals, which takes place cylindrically around the needles by forming a pile of lamellar crystallites, using the ordinary spherulitic crystallisation as reference. The growth kinetics were investigated, by means of microscopy and differential scanning calorimetry (DSC), and the resultant structure was examined by small‐angle X‐ray scattering and melting temperature measurements. The discontinuity found for their theoretical plot was assumed to be attributable to the difference in the type of crystallisation. The lamellar surface free energies obtained for the over‐growth were smaller than those for the spherulitic growth, i.e., σe = 42.1 and σs = 2.94 erg/cm2 against σe = 53.4 and σs = 4.97 erg/cm2. The epitaxy effect was elucidated from the analysis of DSC curves during cooling and the combined free‐energy, σeσs = 89.4 erg2/cm4, was estimated for the initial deposit on the needle surface.
Eutectic solidification of the quasi binary system of isotactic polypropylene and 1, 2,4, 5‐tetrachlorobenzene
Authors: Smith P. , Alberda Ekenstein G. O. R. Van , Pennings A. J. 
Published: April 2007

AbstractThis paper describes a study on eutectic solidification of the quasi binary system of un‐fractionated isotactic polypropylene and the faceted growing diluent 1,2,4,5‐tetrachlorobenzene. According to the Flory‐Huggins theory of melting point depression the phase diagram of the present system does not exhibit a eutectic point for equilibrium conditions. However, under experimental circumstances a simple “eutectic‐type phase diagram” was found, in which the location of the eutectic point was determined by kinetics to a large extent. The very nature of the eutectic solidification process was found to depend critically on the rate of cooling. At cooling rates lower than 0.5°C/ min the simultaneous crystallisation of the polypropylene and the tetrachlorobenzene proceeded in an uncoupled manner, producing a microstructure consisting of randomly mixed polypropylene spherulites and diluent needles with a characteristic dimension of about 0.1 mm. At speeds of cooling exceeding 0.5°C/min coupled growth of the polymer and the solvent occurred, forming a unique eutectic microstructure of curved diluent crystals homogeneously dispersed in a polymer matrix. The transverse dimension of these particular tetrachlorobenzene crystals was found to be in the micron range.
Copolymers of 4‐vinyl pyridine with fluorinated acrylates: Part II ‐ the evaluation of some cationic derivatives as detergent aids
Authors: Carson Phillip A. , Fennah Geoffrey , Bevan Geoffrey 
Published: April 2007

AbstractCationic derivatives of the title copolymers are water‐soluble, materials which adsorb onto fabrics when applied from aqueous solution and render the substrate oleophobic and hence more resistant to staining by oily soils. The effects of the polymer finish on soil‐removal and redeposition during washing are discussed.
The effect of fibre surface treatment, resin type and fabrication process on the interlaminar shear strength of carbon fibre composites
Authors: Judd Nigel C. W. 
Published: April 2007

AbstractSome data related to the preparation of carbon fibre composites is summarised.A limited investigation concerned with presenting markedly different fibre surfaces to the resin by coating with metals and stearic acid is also described.There are carbon fibre surface treatments which lead to improved shear strength, but it is not clear how they are affecting the fibre surface. It also seems likely that some facets of the processing technique can have a large effect on composite quality as indicated by shear strength measurements.The difficulties in interpreting results and identifying sources of variability points to the advisability of statistically planned experiments to assess the significance of changes when investigating possible materials and processing improvements.
Implication of solvent structure in the interaction of poly (vinylalcohol) and short chain monohydric alcohols
Authors: Wardlaw Graham C. , Humphrey Stephen , Eagland Donald 
Published: April 2007

AbstractViscosity and density data have been obtained for aqueous solutions of a monodisperse sample of 90% hydrolysed poly (vinylalcohol) PvOH and for solutions of PvOH in short chain alcohol/water mixtures. The results are interpreted in terms of a ‘dynamic’ flowing volume and a ‘static’ partial molar volume for the macromolecule. Changes in the size of the dynamic and static volumes of the polymer in alcohol/water solvent mixtures are shown to correlate closely with reported changes in the degree of solvent structure. A tentative explanation of the role of solvent structure in the solution behaviour of the polymer is proposed.
Studies on pectins I. Light‐scattering and w
Authors: Smith Janet E. , Stainsby George 
Published: April 2007

AbstractAn enzyme digestion technique for obtaining the scatter from pectin molecules in solution is described and evaluated. Weight average molecular weights, w, calculated from the pectin scatter, are considerably higher than literature values obtained via sedimentation equilibrium experiments, but the present results are preferred. Limited comparison with a number average value, n, obtained osmometrically, suggests that pectins can be extremely poly disperse with w/n = 11, for example. The relationship of intrinsic viscosity to molecular weight is a complex function of composition.
Crystallization of polyethylene oxide III
Authors: Afifi‐Effat Amr M. , Hay James N. 
Published: April 2007

AbstractThe crystallisation kinetics of high molecular weight fractions of polyethylene oxide have been measured dilatometrically and also with a polarising light microscope. In general, marked deviations from the Avrami equation with exponent of 3.0 are observed which cannot alone be accounted for either in terms of rejection of low molecular weight molecules or secondary crystallisation by which crystal perfection occurs. Anomalies in nucleation, and the presence of induction periods, are present, which can account for the apparent low values of the Avrami exponent, i.e. 2.0.
Influence of orientation on polyester fibres
Authors: Brody Harry 
Published: April 2007

AbstractThe technological applications and the associated molecular mechanisms of various levels of orientation in polyester fibres are discussed. The inherent birefringence of these fibres is high and therefore the orientation is easily measurable, while their behaviour is very sensitive to small changes in orientation. In particular, practical properties such as strength, productivity and ease of bulking are very dependent on the spun yarn orientation before the drawing operation takes place, but for completely different reasons. Polyester fibres can be pretreated in terms of orientation in such a way that an extremely high spontaneous extension can be obtained, a property which can be used for bulking. It is shown that variations in low levels of orientation can have profound industrial implications.
Studies on the gel—sol transition and some gel characteristics of photographic gelatine
Authors: Tar Ildikó , Fodor Zsolt , Wolfram Ervin 
Published: April 2007

AbstractStudies have been made on gelatine gels containing inorganic salts and ionic surfactants, with the aim of learning about factors that influence the structural make‐up of hydrogels. Gel‐sol transition temperature, Tm, was studied by a micro capillary‐visco‐meter, gel‐elasticity, E, by applying unidirectional compression and gel‐hardness (rigidity), H, by using Röths micro penetrometer. An attempt was made to describe the results quantitatively. The equation lg Tm = k c + b was found to fit the data on gelation and analogous equations proved to be valid for both the E vs. c and the H vs. c relations. This is true for the different chlorides in the whole concentration‐range studied, but for sulphates over a limited concentration range only. The specific effect of the latter reveals itself mostly in the changes of Tm and H. As ΔH was not altered significantly by the cosolutes used it is concluded that ΔS plays the essential role in the described effects.
Emulsion polymerisation of styrene in the presence of hydrocarbon diluents
Authors: Blackley David C. , Haynes Alan C. 
Published: April 2007

AbstractResults are given for the effects of four hydrocarbon diluents (benzene, toluene, ethylbenzene and cyclohexane) upon the rate of emulsion polymerisation of styrene at 50°C, upon the particle size of the resultant latex, and upon the intrinsic viscosity of the polymer produced. The aromatic diluents were found to have a much greater effect in reducing the rate of polymerisation than can be accounted for by mere dilution of the monomer. For these diluents, the rate of polymerisation is approximately third order in initial concentration of monomer in the oil phase as a whole. Cyclohexane is far less effective as a retarder of polymerisation, the rate being approximately first order in monomer concentration in the oil phase. Particle size determinations indicate that the reductions in rate are due primarily to a reduction in the rate of polymerisation at each locus, rather than to a reduction in the number of reaction loci. The intrinsic viscosity of the polymer produced tends to fall with the rate of polymerisation. These observations are consistent with the view that aromatic diluents cause severe retardation of polymerisation because they diminish the Trommsdorff ‘gel’ effect at the reaction loci. This view is in turn shown to be consistent with a reaction mechanism in which, in the case of styrene‐rich systems at least, the growing polymer particles do not attain equilibrium with the monomer droplets.
Charge‐transfer complexes as polymerisation inhibitors: III. Studies on the mechanism of inhibition and retardation of styrene polymerisation by N, N‐dimethylaniline‐chloranil complexes
Authors: Yassin Ahmady A. , Rizk Nadia A. 
Published: April 2007

AbstractThe mechanism of inhibition and retardation of the sensitised polymerisation of styrene has been investigated using the charge‐transfer complexes of N, N‐dimethylaniline (DMA) with chloranil. The results support the idea that the inhibition reactions involve electron‐transfer from the growing chains to the quinone to form polymeric cations and semiquinone anions. The latter are the actual inhibiting species and the inhibiting efficiency is determined by the extent to which they are found as kinetically independent species in the polymerising system. The inhibition reactions should accordingly be considered as oxidation‐reduction processes in which the growing chains are the electron‐donors.
Theory of neck development in tensile tests on thermoplastics
Authors: Mills Nigel J. 
Published: April 2007

AbstractA one‐dimensional finite element model is used to relate the constitutive equation of a thermoplastic with the phenomena observed when it is tensile tested. Predictions are made of the temperature distribution in a propagating neck, and in particular PVC is shown to be liable to thermal fracture in fast tensile tests. The neck geometry is shown to be an important factor in stable, high speed, neck propagation.
Mechanical properties of polystyrene/ethylene‐propylene copolymer blends
Authors: Barentsen Willem , Heijdenrijk Paul J. , Heikens Derk , Piet Piet 
Published: April 2007

AbstractSome mechanical properties of blends of polystyrene (PS) and ethylene‐propylene‐rubber (EP) were derived from stress‐strain and impact measurements. The strength and impact properties are improved by adding EP‐g‐PS graftcopolymer, prepared by reacting PS with EP, to the blends. It is assumed that the EP‐g‐PS graftcopolymer acts as an adhesive at the interface between the thermoplast and the rubber phases. The addition of the graftcopolymer reduces the dimensions of the dispersed rubber particles.High values of impact strength at reasonable values of tensile moduli could be reached by replacing EP for a smaller or larger part by EP‐g‐PS copolymer.These kinds of EP‐modified PS blends had much higher impact values than those of comparable PS blends containing low density polyethylene (1 dPE) and 1dPE‐g‐PS graftcopolymer or this graftcopolymer only. It seems attractive to ascribe these results to the non‐crystallinity of the PE‐g‐PS as compared with the crystallinity of 1dPE in 1dPE and in 1dPE‐g‐PS. However some caution seems recommendable as EP‐modified PS fractures with microshear whereas, the PE‐modified PS shows crazing.
The effect of rolling on the mechanical properties of polymers with phenylene groups in the main chain
Authors: Macnulty Basil J. 
Published: April 2007

AbstractThe changes occurring, in mechanical properties particularly, when polymers with phenylene groups in the main chain are subjected to uniaxial rolling have been investigated. All properties can be enhanced by the process under the correct conditions. The anisotropy of the specimens at various reduction ratios have also been measured and an explanation of the behaviour on a molecular basis is suggested.
Variation of yield stress with orientation in oriented polyethylene
Authors: Burnay Suzana G. , Groves Geoffrey W. 
Published: April 2007

AbstractHigh density polyethylene with a single crystal texture has been used to examine the variation of yield stress with orientation in both tension and compression. The Coulomb yield criterion, which has previously been applied to yield data in oriented polyethylene, must be rejected since the experimental data can only be fitted over a limited range of orientation in tension only. The von Mises criterion, as modified by Hill 12 for anisotropic materials, appears to give a reasonably good fit to the tensile data. However, further consideration of the theory with respect to the compressive data shows that the criterion is not applicable. The pressure dependent yield criterion proposed by Caddell et al13 also appears unable to predict the experimentally observed tensile and compressive behaviour. A three‐part criterion previously applied to fibre‐composites 11 gives a good fit to the tensile data; this model also predicts the changeover from ductile to brittle behaviour observed in tensile specimens with θ > 70d̀ (θ is the angle between the tensile axis and the molecular axis). None of the yield criteria examined have been able to explain satisfactorily the lack of any marked degree of anisotropy in compression.
Fracture of particulate filled polymers
Authors: Kendall Kevin 
Published: April 2007

AbstractThe addition of particulate mineral fillers to polymers confers certain mechanical property improvements automatically. Stiffness increases, creep diminishes and distortion at elevated temperatures is often reduced. However, the fracture energy of a polymer, as measured in impact, cracking or tearing tests, may vary quite unpredictably when filler is incorporated. In some special cases the fracture energy increases when small amounts of filler are added although it falls away again at higher volume loadings. This enhancement of polymer toughness by filler is an example of reinforcement. More generally the addition of filler causes a continuous and drastic reduction in fracture energy, resulting in a brittle, weak product.This paper seeks to explain the common degrading effect of filler on polymer fracture energy by considering the progress of a crack through the composite material. The crack travels through regions of polymer and also along the interfaces between polymer and filler. Experiment demonstrates that, although fracture of the polymer regions absorbs considerable energy, fracture of the interfaces usually requires very little. These weak interfaces do not resist cracking and are the cause of brittleness in particulate filled systems.This idea was quantified for thermoplastics such as low density polyethylene and poly (methylmethacrylate) filled with colloidal silica by twin‐roll milling. Where the interfacial adhesive energy was much smaller than the polymer fracture energy, the composite toughness dropped as predicted when filler was added. The particle size, the nature or dispersion of the filler, and the crystallinity of the polymer used, had little influence on this phenomenon, as pointed out theoretically.The crucial parameters influencing the fracture energy of the filled polymer were found to be the volume fraction of filler and the interfacial adhesion between polymer and filler. By chemical treatments the adhesive energy between filler and polymer was raised until the interface was almost as tough as the polymer itself. In this case the filled polymer showed good fracture toughness, lending further support to the theory.
The short and long term performance of polymers in different environments
Authors: Andrews Edgar H. 
Published: April 2007

AbstractThe behaviour of polymeric solids in contact with different environments is considered. A thermodynamic viewpoint is adopted and worked out in terms of chemical reactions, physical processes and the interaction between the two.It is shown that chemical attack alone does not normally cause serious loss of physical properties, but that a combination of chemical and physical (or physico‐chemical) interactions between polymer and environment can lead to rapid deterioration.An understanding of these processes, and their synergistic effects, is essential in designing against environmental failure.
Relationship between structure and mechanical properties in rubber‐toughened epoxy resins
Authors: Bucknall Clive B. , Yoshii Toshiya 
Published: April 2007

AbstractToughened polymers were prepared by adding CTBN rubbers to DGEBA‐type epoxy resins. Structure was varied by altering the type and concentration of hardener, the initial molecular weight of the resin, the amount of Bisphenol A added, and the conditions of cure. Electron microscopy showed that these factors affected both particle size and degree of phase separation: rapid curing inhibited phase separation, and produced small particles. Increasing the molecular weight of the resin, either directly or by reaction with Bisphenol A, improved phase separation. Dynamic mechanical measurements of rubber phase volume proved possible, although Tg of the CTBN rubber coincided with a β process in the epoxy resin. Fracture resistance, measured by GIC, increased linearly with rubber phase volume. Creep and yield behaviour were also affected by the degree of phase separation.
Unsolved problems in the fracture of homogeneous thermoplastic
Authors: Haward Robert N. 
Published: April 2007

AbstractThe steps which occur when a homogeneous polymer breaks are considered with reference to plane strain and plane stress conditions. Under plane strain fracture generally seems to take place by cavitation and crazing, though the reason for the different measured energies of crack propagation are not well understood. Other obscure steps concern the basic reason for crazing and the mechanism of craze separation. The mechanism by which polymer separates after yielding by a simultaneous process of crack propagation and plastic straining is also largely unknown as is the reason why non strain softening uniformly extending polymers appear to generate dispersed voids.Only the thermal fracture process seems to raise no fundamental difficulties.
The influence of liquid environmental media on the mechanical behaviour of thermoplastics
Authors: Pütz Dieter , Menges Georg 
Published: April 2007

AbstractThermoplastic materials, having a high chemical stability, are used on a very large scale in corrosive environmental media. Nevertheless, in many cases unexpected failure occurs, since valid construction guide‐lines are missing.For this reason, in the present work a deformation‐related dimensioning criterion is presented, based on the appearance of first irreversible material‐damage.Further, the sorption‐, swelling‐, short‐term‐ and creep‐behaviour of PMMA in the presence of distilled water are described and discussed. Finally, mathematical and graphical procedures for the determination of the creep‐strain under different loading and environmental conditions are shown and explained.