bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shear and tensile creep of thermoplastics at finite strains
Authors: Ballard John W. , Darlington Michael W. 
Published: April 2007

AbstractThe shear and tensile creep behaviour of polypropylene and low‐density polyethylene has been determined for a range of stress levels and creep times from 5 to 105 seconds. The data at finite strains have been correlated using the concept of shear on octahedral planes. When the experimental 100 second shear strains were matched to those predicted from the tensile tests, the experimental and calculated shear creep curves remained coincident, even in tests where the shear strains reached 8% and the materials were highly non‐linear viscoelastic. Manipulation of data in the literature for two amorphous polymers suggests a different pattern of behaviour and this is related to differences in the affect of the hydrostatic component of stress in the tensile tests on the creep response of the four polymers.
The provision of useful mechanical properties in polymeric materials
Authors: Baer Eric 
Published: April 2007

AbstractThis paper describes four aspects of the work which has been performed by individuals within my research group during the past five years. The first subject discussed is the effect of pressure and environment on the yield and fracture behaviour of plastics. Secondly, a description is given of micro deformation processes in amorphous polymers, with emphasis on the control of the transition from the crazing to the shear banding modes of irreversible deformation. The third subject discussed emphasises the importance of the adhesive bond in composite materials. In addition to the usual concern with chemical interactions at the interface, some recent work is described showing the importance of moulded‐in thermal stresses which can be controlled by process history. Finally, a more sophisticated multi‐composite system is dealt with, which is found in nature; namely, the relationships between hierarchial organisation and mechanical function in tendon. Whether, as a result of understanding biological composites of this type, innovative synthetic materials will immerge makes for interesting speculation at the present time.All of the subjects described contain many unsolved questions, and I am hopeful that these will provide us with useful and interesting territory for research in the future.
The detergent stress‐cracking of polythene
Authors: Owen D. Roger J. , Haward Robert N. , Burbery Anthony 
Published: April 2007

AbstractWhenever the fracture of a polymer is preceded by crazing or other types of cavity formation, energy must be supplied both for local yielding and for the generation of a new surface. However previous calculations for rigid glassy polymers have shown that the surface energy contribution required for the formation of a craze, compared with that associated with plastic and elastic strains is small. In order to study this problem further, we have now made a finite element analysis of the cavitation of an elastic‐plastic solid introducing a surface energy term. This shows that the ratio of the plastic energy requirement to surface energy depends, not unexpectedly, on (I) the ratio of yield stress/ surface tension and (II) cavity size. Thus for polymers with a low yield stress such as polythene, the surface tension becomes significant if the hole diameter is below 100 nm. In these circumstances crazing and cracking is predictably accelerated by dilute aqueous detergents which do not need to penetrate the polymer, provided of course that the detergent has access to the cavities.Hole growth also depends on the extent of orientation hardening during plastic strain and this contributes to the greater stress crack resistance of high molecular weight polythene. The occurrence of a larger amount of plastic deformation on the fracture surfaces of high molecular weight polymer has been demonstrated by Harman for high density polythene and is confirmed here in scanning electron micrographs of low density material.Other electron micrographs show that very small cacities are indeed formed when high density polythene is broken in the coventional detergent stress cracking test, thus accounting for the accelerating effect of the detergent.
Polymeric Silver Ligands
Authors: De Winter Walter , Pollet Robert 
Published: April 2007

AbstractLow molecular silver ligands are generally known and commonly used as ingredients in photographic baths and emulsions. Polymeric silver ligands on the contrary have been studied much less for these purposes although certain advantages connected to their application can be observed. The polymeric ingredients can indeed exert photographic effects which are not exhibited by the ligand group of the monomer (polydentation). The hydrophilic character can be accurately adapted by a judicious choice of the comonomer. Finally diffusion fastness, an important property for multilayer materials, can be imparted without losing the interesting photographic effects.
Light Scattering from Copolymer Solutions
Authors: Ali Sabz 
Published: April 2007

AbstractA new type of copolymer from para‐aminobenzoic acid and 6‐aminohexanoic acid was obtained by reacting the monomers in four different mole ratios. The polycondensation was carried out at 80d̀C with triphenyl phosphite as the initiator in N‐methyl‐2 pyrrolidone/pyridine mixture. The molecular weights of unfractionated and fractionated samples were determined by light scattering techniques in solvents of varying refractive index. From the values of second virial coefficient it is concluded that the solvent power for copolymer increases with increasing aminohexanoic acid mole fraction in the case of dichloroacetic acid and trifluoroacetic acetic acid while in dimethyl acetamide it decreases.
Water Soluble Polymers for Medicine
Authors: Kálal Jaroslav , Drobnik Jaroslav , Kopeček Jindřich , Exner Josef 
Published: April 2007

AbstractA number of general reviews have already been published on this topic and so the authors will present information on their approach and some results obtained.Polymers for medical uses are a traditional field at the Institute of Macromolecular Chemistry. However, crosslinked hydrophilic polymers ‐ so called hydrogels ‐ were the prevailing object in the past. Either as soft highly swollen materials for prothesis ‐ like soft contact lenses ‐ or heavily crosslinked macroporous beads designed as special sorbents or carriers of biologically active groups. Only a few years ago a research programme on soluble polymers was focussed mainly on general problems. The overall view about the main directions of the authors research is schematically presented on Fig. 1. It also shows the two types of polymers the authors are using in their experiments. The first one poly[N(2‐hydroxypropyl)methacrylamide]3a was chosen from the set of N‐substituted acryl‐and methacrylamides4 because of simple preparation and purification of the monomer. The other is a polyamide (polypeptide) described by Neri et al. in 1973.5 It is more hydrophilic and provides a good possibility to prepare a whole set of derivatives from a common polymeric intermediate ‐ polysuccinimide.
Polyester‐Polyether Block Copolymers II. Thermal and Mechanical Properties of Poly(hexamethylene terephthalate)/Poly(oxytetramethylene) Block Copolymers
Authors: Ghaffar Abdul , Goodman Isaac , Peters Raymond H. 
Published: April 2007

AbstractThe melting and crystallisation behaviour of crystalline phases in poly (hexamethylene terephthalate)/poly(oxytetramethylene) block copolymers have been investigated in relation to copolymer composition and polyether block molecular weight (m.w.). In contrast to that in corresponding homopolymer blends, the polyester crystallinity in the block polymers is greatly reduced by incorporation of polyether units, though some persists even at low polyester contents. Concomitant changes in the glass transition temperatures show part of the polyester component to form a homogeneous component of the amorphous phase.The mechanical properties change with composition in parallel with the changes in copolymer crystallinity and Tg. Copolymers with 20‐60 w % of poly(oxytetramethylene) units of m.w. 2000 are highly extensible elastomers. Those with higher m. w. polyether blocks have higher modulus and strength but suffer a serious loss of properties at 60d̀C.The observations are interpreted in terms of a model in which polyester crystallites (and polyether crystallites also, for the higher m. w. polyether blocks) are supported within an amorphous matrix by tie‐molecules whose nature changes with the copolymer compositions. The results are compared with those for analogous polyester‐polyethers having different structural components.
Polyester‐Polyether Block Copolymers III. Supramolecular Texture in Poly(hexamethylene terephthalate)/Poly(oxytetramethylene) Block Copolymers and Related Homopolymers and Blends
Authors: Ghaffar Abdul , Goodman Isaac , Peters Raymond H. , Segerman Ephraim 
Published: April 2007

AbstractOptical and electron microscopy and small‐angle X‐ray scattering have been used to investigate the texture of poly(hexamethylene terephthalate)/poly(oxtetramethylene) multi‐block copolymers. The findings are consistent with a substantial separation of the combined sub‐species into separate phases, and with the aggregation of the alkylene terephthalate ‘hard’ segment blocks into crystalline forms analogous to those of the homopolymer alone and connected by microfibrillar units. The observations are correlated with the mechanical properties of the copolymers in terms of a ‘string of beads’ model, and compared with existing knowledge of phase‐separation morphology in other families of block copolymers. Some investigation has also been made into the morphology of poly(hexamethylene terephthalate) and poly(oxytetramethylene) homopolymers and their blends crystallised from the melt. The results are considered in relation to the properties of the corresponding copolymers.
The Reaction of Plumbonacrite (Basic Lead Carbonate) with Hot DOP, and the Stabilisation of Plasticised PVC
Authors: Michell E. W. John 
Published: April 2007

AbstractThe basic lead carbonate ‘plumbonacrite’, 6PbCO3.3Pb(OH)2.PbO, has been reacted with di‐2‐ethyl hexyl phthalate (dioctyl phthalate, DOP), C6H4(COOC8H17)2 at 180d̀C under nitrogen. Anhydrous monobasic lead orthophthalate, PbO.Pb6H4(COO)2, was the only product detected by X‐ray powder diffraction (X.R.P.D.). These studies are related to previous work on reactions taking place in hot polyvinyl chloride (PVC) blends containing DOP plasticiser and basic lead stabilisers. It is concluded that plasticiser stabiliser interaction can play a significant role in stabilising PVC against thermal decomposition, and that efficient stabilisation takes place largely by a free‐radical exchange mechanism. Characteristic X.R.P.D. data are tabulated for anhydrous monobasic lead orthophthalate, and for monobasic lead orthophthalate monohydrate, PbO. PbC6H4(COO)2‐ H2O, which can be made in aqueous suspension and which converts to the anhydrous salt at 180d̀C. X.R.P.D. data are also given for dibasic lead orthophthalate, 2PbO.PbC6H4(COO)2.1/2H2O, which is well known as a stabiliser for PVC, and which might have been expected to form in these experiments, (but did not in fact do so).
On the Applicability of Gardon's Equations for the Calculation of Particle Size in Emulsion Polymerisation
Authors: Dunn Alexander S. , Al‐Shahib Walid A. G. R. 
Published: April 2007

AbstractGardon's revision of the Smith‐Ewart theory of emulsion polymerisation makes it possible to calculate the average particle size of the latex produced from the conditions used for the polymerisation at least for monomers with a low monomer transfer constant. Good agreement has been found between the calculated particle sizes and the turbidity averages measured by light scattering for polystyrene latices prepared with various emulsifiers. However the theory neglects the effect of the ionic strength of the aqueous phase although Gardon's own results show this to be a significant parameter: increase of ionic strength increases the average size of the latex particles by reducing electrostatic stabilisation. The difference between the total and the micellar surfactant concentration is significant for surfactants with relatively high critical micelle concentrations and a considerable improvement in agreement between measured and calculated particle sizes is found when the concentration of micellar surfactant is used in the calculation. The theory requires the reaction rate to depend on the 3/5ths power of the concentration of micellar surfactant and although this would appear to have been satisfactorily verified experimentally, replotting of the extensive series of precise results published by Bartholome, Gerrens, Herbeck and Weitz shows that the double logarithmic plot is not actually linear. This is probably the result of a slow change of micelle size as the surfactant concentration is increased.
The Effect of Acid Acceptors on the Temperture Activated Creep of a Vinylidene Fluoride/Hexafluropropene/Tetrafluoroethylene Terpolymer (Viton B)
Authors: Barton John M. 
Published: April 2007

AbstractCreep under compressive stress, modulus, and solvent swelling characteristics were determined with a thermomechanical analyser for a vinylidene fluoride/hexafluropropene/ tetrafluoroethylene elastomer at various temperatures. Significant creep occurs above 200d̀C where the elastomer undergoes oxidative degradation. The rubber was compounded with various metal oxides and hydroxides as acid acceptors, and the effect of these on creep at elevated temperatures was studied. At 250d̀C MgO, CaO and Ca(OH)2 were all found to produce a relatively low creep rate compared to that of a control sample.
The Efficiency of Polymer Fractionation at Lower Critical Solution Temperatures
Authors: Wolf B. A. , Bieringer H. F. , Breitenbach J. W. 
Published: April 2007

AbstractThe efficiency of a single fractionation step (i.e. of the partition of a given polymer sample between the coexisting phases which form when its solution demixes) is governed by the variation of the mass ratio of the individual P‐mers with chain length. These dependences have been measured for the system dimethoxymethane/diethylether/ polystyrene which exhibits lower critical solution temperatures by means of the Baker‐Williams method and by means of g.p.c. Their comparison with the results of previous investigation on systems showing upper critical solution temperatures reveals no thermodynamic differences in the aptitude of upper and lower critical solution temperatures for fractionation from dilute solutions.The extension of the molecular weight distribution into the low molecular weight region by the addition of oligomer, answered the question whether the monomer concentration in the coexisting phases is practically identical, as predicted by classical theories, or larger by a factor of nearly ten in the polymer‐rich phase, as extrapolated from the information concerning the polymer. The direct observation yields intermediate values which demonstrate that the variation of the logarithm of the partition coefficient with the degree of polymerisation P cannot be represented by a linear function with sufficient accuracy when a broader range of molecular weights is considered; in this case it is necessary to replace P by P2/3.
Intermolecular interactions in blends of functionalised propylene polymers with poly(vinylchloride) or polystyrene
Authors: Benedetti Enzo , Posar Francesco , D'Alessio Aldo , Vergamini Piergiorgio , Aglietto Mauro , Ruggeri Giacomo , Ciardelli Francesco 
Published: April 2007

AbstractAtactic and isotactic polypropylene (APP and IPP), and ethylene‐propylene copolymers (EP). functionalised by reacting the molten polymer with diethylmaleate (DEM) in the presence of dicumylperoxide (DCP). have been blended with poly(vinylchloride) (PVC) and polystyrene (PS). These mixtures have been investigated by means of infrared spectroscopy at different compositions in the region of carbonyl absorption. The features of this last band in the mixture suggest the occurrence of intermolecular interactions involving mainly the carbonyl groups of the functionalised polymer and the methine hydrogens of PVC.
Ring‐opening polymerisation of bicyclo[2.2.2]oct‐2‐ene
Authors: Hamilton James G. , Ivin Kenneth J. , Rooney John J. 
Published: April 2007

AbstractBicyclo[2.2.2]oct‐2‐ene has been polymerised by ring opening using a catalyst consisting of (mesitylene)W(CO)3/EtAlCl2/2,3‐epoxynorbornane/Me4Sn and a trace of norbornene. The polymer was characterised by 13C n.m.r. and contained 32% cis double bonds, with a somewhat blocky cis/trans double bond distribution.
Studies on the structural features of sodium alginate entrapped Kluyveromyces marxianus NCYC179 cells used for alcohol production from whey permeate
Authors: Marwaha Satwinder S. , Kennedy John F. 
Published: April 2007

AbstractAlginate‐entrapped living Kluyveromyces marxianus NCYC179 cells were successfully used in alcohol production from whey permeate. Using 10% whey lactose as substrate, an alcohol production efficiency of 81.5–84.9% and 84.0–88.2% with cell viability maintenance between 82.8–84.3% and 81.0–84.3% of the immobilised cells during the monitoring periods, in batch (six repeat runs) and continuous (23 days of experimenting time) systems, respectively. The immobilised samples remained stable during the course of fermentation with no leakage of K. marxianus cells into the surrounding medium in the case of the batch system. However, slight leakage after 10 days of continuous run in the continuous process was recorded. The scanning electron microscopic studies of the beads containing entrapped yeast cells and sections or crushed samples of the beads carried out at the start and termination of fermentation in both the processes (batch and continuous) revealed that the immobilisation procedure does not influence any morphological change in the entrapped cells during the prolonged periods of fermentation. Moreover, the gel matrix structure was also found to be unaffected by the fermentation conditions employed during the course of present studies.
Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)
Authors: Varma D. S. , Agarwal Radha , Varma Indra K. 
Published: April 2007

AbstractCopolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (Tg). melting points (Tm) and crystallisation temperatures (Tc) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in Tg, Tm and Tc. The as‐prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.
Deuterium magnetic resonance studies on strained selectively deuterated elastomers
Authors: Gronski Wolfram , Emeis Detlef , Brüderlin Alfred , Jacobi Marly Maldaner , Stadler Raimund , Eisenbach Claus D. 
Published: April 2007

AbstractThe lineshape analysis of the 2H nuclear magnetic resonance of uniaxially strained poly(1,4‐butadiene) networks deuterated homogeneously and selectively at network junctions shows that the orientation of chain segments attached to crosslinks is larger than the average segmental orientation. In addition, it is shown that the molecular effective extension ratio of all elastically effective chains is smaller than the macroscopic extension ratio, and short chains are stretched to a higher extent than long chains. The deviation from the affine deformation behaviour and the onset of inhomogeneous deformation of individual chains takes place at the transition from the Gaussian to the non‐Gaussian network. In the Gaussian regime the segmental orientation varies with the inverse of the molecular weight of elastically effective chains in agreement with molecular theories of rubber elasticity. 2H n. m. r. spectra of a thermoplastic poly(styrene‐b‐butadiene‐b‐styrene) block copolymer carrying selectively deuterated butadiene segments at the block boundaries reveal an enhanced mobility of these segments under deformation. 2H n. m. r. experiments on amorphous segmented polyurethanes selectively deuteratured in hard and soft segments, respectively, show that the elasticity in these samples is achieved by physical crosslinks formed by very small highly mobile aggregates of hard segments dispersed in the soft phase. Within the hard domains two processes for motion due to phenyl groups in 4. 4'‐methylenebis(phenylisocyanate) units and CH2 groups in 1. 4‐butanediol units can be discriminated.
Bimodal networks and networks reinforced by the in situ precipitation of silica
Authors: Mark James E. 
Published: April 2007

AbstractThe goal of primary interest in these investigations was the development of novel methods for preparing elastomeric networks having unusually good ultimate properties. The first technique employed involves endlinking mixtures of very short and relatively long functionally‐terminated chains to give bimodal networks. Such (unfilled) elastomers show very large increases in reduced stress or modulus at high elongations because of the very limited extensibility of the short chains present in the networks. The second technique employs the in situ precipitation of reinforcing silica either after, during, or before network formation. The reaction involves hydrolysis of tetraethylorthosilicate, using a variety of catalysts and precipitation conditions, and the effectiveness of the technique is gauged by stress‐strain measurements carried out to yield values of the maximum extensibility, ultimate strength, and energy of rupture of the filled networks. Information on the filler particles thus introduced is obtained from density determinations, light scattering measurements, and electron microscopy.
Interpenetrating polymer networks
Authors: Frisch Harry L. 
Published: April 2007

AbstractInterpenetrating polymer networks (IPNs) composed of two or more chemically distinct networks are not only intrinsically interesting as examples of macromolecular chemical topological isomerism but are in practice useful means of controlling mutual miscibility and phase morphology in crosslinked polymers. We will first review briefly the synthesis and properties of such IPN systems. This will be followed by an outline of a phenomenological theory of the phase stability and linearised theory of spinodal decomposition of binary, chemically quenched, low crosslink density IPNs recently developed by K. Binder and the author. Finally, we will discuss some aspects of the synthesis of ternary IPNs and the thermochromic properties of IPNs containing a crosslinked polydiacetylene.