bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface tension and mechanical properties in polyolefin composites
Authors: Pukánszky Béla , Fekete Erika , Tüdós Ferenc 
Published: March 2011

AbstractPolyolefin composites were prepared with CaCO3 fillers of different specific surface area. The fillers were surface treated with stearic acid between 0 and 100% surface coverage. As an effect of the treatment, surface tension of the fillers and also polymer/filler interaction decreased. The relation between interfacial interaction and mechanical properties of the composites was analysed by the equation developed earlier to describe the composition dependence of the tensile yield stress. The characteristics of the interphase were calculated, its yield stress decreases and thickness increases with increasing surface coverage. Reversible work of adhesion can be successfully related to the tensile yield stress, but a more complicated correlation exists between the thickness of the interphase and the strength of the interaction than assumed earlier. Other mechanical properties also change with the surface treatment; modulus and strength decrease and extensibility increases with decreasing polymer/filler interaction.
Effect of fiber treatment on mechanical properties of polypropylene‐wood fiber composites
Authors: Raj R. G. , Kokta B. V. , Daneault C. 
Published: March 2011

AbstractPolypropylene (PP) was reinforced with chemi‐thermomechanical (CTMP) pulp and wood flour. Different chemical treatment of the fiber a) polyethylene‐poly‐(phenyl isocyanate), b) silane A‐172 and c) epolene was carried out to improve the bonding between the polymer and fiber. PP reinforced with CTMP pulp and wood flour showed a decrease in stress values as the concentration of fiber increased in the composite. Tensile modulus generally increased with filler loading and was not much affected by fiber treatment. Experimental results of the composites were compared with theoretically predicted values.
Free volume conception op dispersed systems and formation of highly loaded composites
Authors: Kuleznev Valery N. , Kandyrin Leonid B. 
Published: March 2011

AbstractThe present paper deals with the study of the interrelationship between the structure and properties of a relatively new class of promising polymeric materials ‐ highly loaded composites with a liquid thermoset hinder, hardened in the course of processing. One of the main targets when creating these composites is the development of formulations containing a maximum amount of dispersed filler, while retaining, at the same time, the optimum complex of properties.
Vinyl chloride suspension polymerisation and the control of polymer properties
Authors: Smallwood P. V. 
Published: March 2011

AbstractA number of poly(vinyl alcohols), used in the suspension polymerisation of vinyl chloride, have been fractionated and characterised. The most effective had the highest molecular weight and contained the most unsaturation. The more insoluble fractions gave the best balance of product properties. Reactor sampling experiments have been used to determine the mechanism of polymerisation. In most polymerisations, the final grain size is determined by factors that control the coalescence and break‐up of the monomer droplets during the first 15% conversion. It is suggested that the structure within the grains is controlled by the formation of a continuous network of PVC primaries which retards droplet contraction.
Advances in the investigation of vinyl chloride (CO)polymerization kinetics
Authors: Mrázek Zdenêk , Lukáš Rudolf 
Published: March 2011

AbstractGas chromatographic determination of unreacted monomers in periodically taken samples of a heterogeneous reaction mixture was applied in an investigation of the kinetics of suspension homopolymerization of vinyl chloride and of its copolymerization with 1‐olefins. Examples are given of the application of the method in a kinetic description of the synthesis of various types of PVC (K values 58–70), in the testing of various initiators and in the optimization of recipes and reaction conditions of the copolymerization of vinyl chloride with propene. The results presented in the form of conversion curves and time dependences of the reaction rates are discussed.
Configurational and conformational control of chemical modification and thermal degradation of poly(vinyl chloride)
Authors: Millán José‐Luis , Martínez Gerardo , Mijangos Carmen , Gómez‐Elvira José Manuel 
Published: March 2011

AbstractIn the light of some earlier works on nucleophilic substitution on poly(vinyl chloride) (PVC) in solution, a conformational mechanism is proposed. It considers the TT isotactic diad conformation to be the only reactive species and the reaction to be controlled by the conformational equilibria that make such conformation available. As a result all the isotactic and the heterotactic triads are capable of reacting provided that they adopt the GTTG− and the GTTT conformation, respectively. Since the replacement of a definite fraction of isotactic triads, which are assumed to be of the GTTG− conformation, results in an enhanced thermal and photochemical stability, the lability of some chlorines at such triads is proved. Further arguments in favour of the conformational mechanism are afforded through recent results of i) substitution studies in the melt and in aqueous suspension with phase transfer catalysts, ii) accurate 13C NMR measurements of triad variation with degree of substitution.
The fate of organotin stabilisers in poly(vinyl chloride) (PVC) under processing conditions and during thermal degradation
Authors: Müller Hermann A. 
Published: March 2011

AbstractQuantitative 119Sn‐NMR spectroscopy is a valuable tool to identify and determine quantitatively all organotin species which are formed in PVC during processing or a thermal degradation test by reaction with the polymer or by subsequent ligand exchange reactions between different organotin compounds. By this method conversion rates of monoalkyltin and dialkyltin isooctylthioglycolates in PVC have been determined as a function of the duration of thermal treatment. It is shown that organotin stabilisers can also react with lubricants and other additives to compounds like R2Sn(SR)(OCOR) during the processing of PVC, thus influencing the efficiency of the stabilising action.
High heat applications for ELIX® 300 modified rigid PVC in injection moulding, extrusion, calandering and blow moulding
Authors: Mayrhofer P. 
Published: March 2011

AbstractELIX® 300 resins ‐ impact modified styrene maleic anhydride terpolymers ‐ allow for improvements in practical heat distortion resistance of PVC to temperatures over 100°C whilst adding impact resistance and maintaining its chemical resistance and fire retardancy. This paper describes what is meant by practical heat distortion resistance and how the semi‐compatible nature of PVC/ELIX® 300 blends helps to meet higher in‐use temperature requirements. Main properties of PVC/ELIX® 300 blends as a function of concentration and K‐value of the PVC, considerations concerning formulations and the influence of compounding techniques on morphology and properties are discussed and some practical application examples are given.
Application problems of PVC materials irradiated with high doses
Authors: Hell Z. , Junaković Z. , Ranogajec F. , Dvornik I. , Barić M. 
Published: March 2011

AbstractRadiation crosslinking of PVC in the presence of triallyl cyanurate as a sensitizer, dioctyl phthalate as a plasticizer and lead and tin stabilizers was examined. Standard methods of testing PVC materials were used. Direct relations between crosslinking extent, elongation, and Vicat softening temperature changes were found. Lead stabilizers proved to be more efficient than tin stabilizers. The influence of radiation dcse on immediate and long‐term changes of PVC was investigated.
Structure defects and thermal stability of poly(vinyl chloride)
Authors: Zegelman V.I. , Titova V.A. , Pomerantseva E.Gr. , Taikova T.A. , Zilberman E.K. 
Published: March 2011

AbstractThe presence of polyene and peroxide structures in PVC and their contribution to the rate of thermal decomposition were determined using a large number of commercial suspension PVC samples. Two types of PVC having conjugated ‐C=C‐bonds with different reactivity towards dienophiles were found. Polymer samples of the first type react with chlorine, organic phosphites and maleic anhydride under mild conditions whereas the second type PVC under the same conditions reacts only with chlorine. The obtained data show that polyene structures in these two types of PVC are of cis and trans configuration, respectively. It was also demonstrated that the contribution of diene and peroxy groups to the rate of PVC thermal decomposition is greater than the contribution of any other anomalous structures.
Characteristics and applicational properties of peroxide suspensions
Authors: Westmijze Hans 
Published: March 2011

AbstractPeroxide suspensions are liquid initiators for the manufacture of PVC with the following characteristics: low viscosity (50–500 mPa.s), good pumpability, small average particle size (5–20 μm), good dissolution rate in vinyl chloride and complete safety. Possible applicational advantages are: marginally faster polymerization, higher porosity and lower fish‐eye level of PVC. A review is given of possible causes of fish‐eyes. One of the causes is an inhomogeneous distribution of initiator over vinyl chloride droplets. An explanation of the low fish‐eye level realized with peroxide suspensions, is that (because of good dispersability in water and a small average particle size) a homogeneous distribution of the peroxide over vinyl chloride droplets is obtained in an early stage of the process.
Networks from cyanic acid esters and glycidyl ethers
Authors: Bauer M. , Bauer J. 
Published: March 2011

AbstractPolycyanurates were prepared by polycyclotrimerization of aromatic dicyanates in bulk. The reaction kinetics and the resulting build‐up of a trifunctional network was modelled. Modified polycyanurates were synthesized by a co‐reaction of dicyanates with diglycidyl ethers. The statistics of the resulting network building process was modelled by cascade theory combined with a model of the kinetics of structural elements. The good agreement between theory and experiment is shown.
Network formation in an epoxy system: A kinetics, viscometric and viscoelastic study
Authors: Feve Michel 
Published: March 2011

AbstractA purely aliphatic diepoxy‐diamine system has been used. It is well suited for a gelation study because the chemistry is very simple and the glass transition temperature of the obtained rubber is more than 50 degrees lower than the curing temperature. The kinetics equation, established using isothermal differential scanning calorimetry (DSC) runs, agree well with that suggested by R.J.J. WILLIAMS et al. (1984). The viscoelastic behaviour, monitored by dynamic mechanical analysis, exhibits three successive zones: viscous liquid, viscoelastic material, elastic solid. Gelation occurs in the second one, the duration of which is very short. At the gel point, we observe the behaviour described by CHAMBON & WINTER (1985): tgδ is independent of the frequency;η* and G', respectively, are proportional to ω−1/2 and ω1/2. The high values of viscosity displayed by the viscometer are wrong and the measured torque derives from the elasticity of the material.
Cooperative diffusion in partially neutralized poly(acrylic acid) gels
Authors: Ilmain F. , Candau S. J. 
Published: March 2011

AbstractPoly(acrylic acid) networks swollen with water and having different ionization degrees and different polymer concentrations, were investigated using elastic and quasi‐elastic light scattering. The scattered intensity was found to vary as the ratio of the polymer concentration to the ionization degree, which shows that the osmotic pressure is dominated by counterion entropy. The behavior of the cooperative diffusion coefficient cannot be explained by the scaling theories and involves an unexpected variation of the frictional coefficient with polymer concentration.
Mechanical and swelling equilibrium characterization of high cis‐1,4‐polyisoprene networks
Authors: Queslel Jean‐Pierre , Monnerie Lucien 
Published: March 2011

AbstractEquilibrium stress‐strain relationships in uniaxial extension for high cis‐1,4‐polyisoprene (Shell IR 307) networks were obtained by extrapolation of relaxation measurements to infinite time through a Bernstein‐Kearsley‐Zapas (BKZ) constitutive equation. Three series of networks were investigated, each series being characterized by its polymer precursor molecular weight. The influence of cross‐linking density was studied through varying amounts of dicumyl peroxide as cross‐linking agent. These results were used to test Flory and Erman's recent molecular theory of networks with constraints on junctions.Swelling equilibrium experiments with benzene and cyclohexane were performed on these networks and were in agreement with the mechanical analysis. The polymer‐solvent interaction parameter for the system cis‐polyisoprene + cyclohexane was estimated to be 0.31 at 20°C in the range 0 to 0.2 of polymer volume fraction.
Electron microscopy investigations of the morphology of a polyester‐polyurethane
Authors: Schraders Sigurd , Li Xuan , Guo Fanxiu , Liu Yong , Luo Jijiang , Xu Duanfu 
Published: March 2011

AbstractIn the current paper the morphology of a slightly crosslinked polyester‐polyurethane (hard‐segment content ca. 33 wt.‐%) is studied by means of transmission electron microscopy (TEM).A new staining technique based on ruthenium tetroxide was applied. This new technique allows the unambiguous visualization of the typical microdomain structure of the polyurethane and also of a wide size spectrum of globular hard‐segment‐rich domains which result from phase separation in the early stage of preparation.The hard‐segment‐rich microdomains have a size between 1.5 and 10 nm while the globular domains span a size spectrum from 10 to 2000 nm.
Principles of the van der Waals network concept: Time‐dependent processes
Authors: Kilian Hanns‐Georg 
Published: March 2011

AbstractThe leading ideas behind the van der Waals modification of the Gaussian network are explained including a discussion of the meaning of the van der Waals parameters. The utility of approach is demonstrated in terms of a representation of deformations, of networks under different strains and of the heat exchanged during extension. The interpretation of stress‐strain experiments carried out on bimodal end‐linked model networks leads to a characterization of the width of the chain‐length distribution in rubbers. Finally, it is shown that the non‐linear visco‐elastic response in stress‐strain cycles of natural rubber can be understood within the framework of the classical thermodynamics of irreversible processes. The time dependent stress‐strain behaviour is fairly well described in the temperature regime of rubber‐elasticity by using a discrete small‐strain shear‐relaxation spectrum.
Chaotic dynamics and entropy elastic forces of chain molecules
Authors: Winkler R. G. , Reineker P. 
Published: March 2011

AbstractThe dynamic behaviour of a phantom molecular chain, consisting of mass points connected by mass‐less rigid rods, is investigated in two dimensions. The end points of the chain are fixed in space. The dynamics of the molecule are determined by Newton's equations of motion. Their numerical solution is represented in form of Poincaré sections and shows deterministic chaos. It is shown that the forces of constraint, acting on the fixed end points, fluctuate in time. The time average of these forces is calculated as a function of the extension of the chain.
A mean‐field approach of the theory of topological constraints in polymer melts and networks
Authors: Heinrich Gert , Straube Ekkehard 
Published: March 2011

AbstractA new mean‐field concept is discussed for the topological constraints in polymer melts and networks. The constraining potential is assumed to be determined by the dependence of the free energy of the surrounding chains on the position of the considered chain. The concept is applied to polydisperse systems, in which a new criterion is derived to describe the onset of the influence of entanglement effects.
Distribution functions in elasticity
Authors: Eichinger B. E. , Shy L. Y. , Wei Gaoyuan 
Published: March 2011

AbstractThe formation of a gel or elastomer entails the linking together of molecules to form a contiguous random network that has macroscopic dimensions. Forces are propagated in networks along polymer chains and through junctions to other chains. It is important to understand the structure of the force constant matrix that describes a system as complicated as this, even in the case where the potential energy is approximated by a simple harmonic function. This force constant matrix was first formulated by James, but because it is a large random matrix, very little progress can be made in the analysis of its properties. We have opted to approach this problem with the use of large scale computations that are based upon simulations of the formation of networks. Subsequent evaluation of the eigenvalue spectrum of the matrix lends considerable insight into the equilibrium and dynamic properties of elastomers. For present purposes this analysis is couched in terms of the calculation of the probability distribution of the gyration tensor for a phantom network in which non‐bonded interactions are not considered.
Syntheses and reactions of azo‐group containing networks
Authors: Nuyken Oskar , Grunow Arthur , Pampus Gottfried 
Published: March 2011

AbstractAzo monomers of the general structure magnified image have been terpolymerized with styrene and butadiene (I) to form azo‐group containing rubber (SBR).Copolymerization of butadiene and acrylonitrile with 3 yields azo group containing nitrile rubber (II). Networks are formed, if the copolymerization of butadiene and acrylonitrile is carried out in the presence of divinylbenzene (DVB) (III) or in the presence of DVB and 3 (IV). Thermolysis or photolysis of the polymeric azo initiators (I, II) yields networks without addition of a low molar‐mass crosslinking agent. Heating or irradiation of the azo‐containing pre‐network (IV) increases the network density.Heating a mixture of (II) or (IV) with natural rubber yields polymer blends which are stabilized by covalent links between the different polymers. The network characterization was carried out by swelling experiments.The incorporation of the azo monomers into the azo copolymers is almost ideal under “cold rubber” conditions, meaning that the composition of the products does not change with conversion.
The macroporous network of “bead cellulose” and its response to crosslinking with epichlorohydrin
Authors: Loth Fritz , Philipp Burkart 
Published: March 2011

AbstractMacroporous hydro‐ and xero‐gels of bead cellulose, prepared by thermal coagulation of cellulose xanthate after emulsification in an organic liquid immiscible with water, and subsequent decomposition to cellulose II have been modified by crosslinking with epichlorohydrin during the process of preparation as well as afterwards in different states of drying. The changes in network structure, depending largely on the ratio of crosslinking to total add‐on of epichlorohydrin, are interpreted by the counteracting effects of a “structure tightening” and a spacer action.
Establishing mechanisms for emulsion polymerizations
Authors: Casey Brendan S. , Maxwell Ian A. , Morrison Bradley R. , Gilbert Robert G. 
Published: March 2011

AbstractEmulsion polymerization systems are so complex that different workers often believe contradictory mechanisms for ostensibly the same system. A number of case studies are examined wherein data have been obtained that are able to refute mechanistic postulates (as distinct from supporting a mechanism by showing that a mathematical model incorporating it is able to reproduce a limited range of data). These examples are: (1) particle nucleation (refutation of micellar entry); (2) free radical desorption (refuting its unimportance for systems with insoluble monomers, and showing that the transfer/diffusion mechanism for this process is suspect); (3) entry (refutation of 100% initiator efficiency); (4) propagation (refutation of the assumption that the propagation rate coefficient (kp) drops to zero at the glass transition); and (5) termination (refutation of the assumption that dependence on lengths of each chain can always be ignored).
On the initiation mechanism in emulsion polymerization systems
Authors: Bartoň Jaroslav 
Published: March 2011

AbstractThe problem of the locus of initiation in conventional emulsion polymerization is discussed on the basis of the literature survey (copolymer composition in the early stages of emulsion polymerization, particle size distribution). The idea of homogeneous nucleation of polymer particles even for non‐polar monomers is supported by recent studies of emulsion polymerization in the presence of oil‐soluble inhibitor. The method of the oil‐soluble inhibitor was also used for inverse emulsion polymerization systems. The studies have brought new experimental evidence for the locus of initiation in classical as well as in inverse emulsion polymerization systems. It seems now reasonable to accept the idea that in conventional emulsion polymerization systems the locus of initiation is the water phase. In inverse emulsion polymerization systems the results point to the phase boundary between the continuous phase and (oil‐soluble part of) inverse micelles as the main locus of initiation for the systems with oil‐soluble initiator.
Preparation and characterization of core‐shell latexes
Authors: Hergeth Wolf‐Dieter , Schmutzler Klaus , Wartewig Siegfried 
Published: March 2011

AbstractPolymeric dispersions with a concentric core‐shell structure of the latex particles were obtained by a two‐stage emulsion polymerization technique. Conditions for the formation of shells on polymeric seeds are discussed. SANS and SAXS investigations were carried out in order to verify the core‐shell structure of the particles. DSC and IR measurements indicate the existence of an interfacial layer between core and shell polymers. The results are transferred to emulsion polymers containing inorganic filler particles.
Radical polymerization in micelles of surface‐active monomers
Authors: Egorov Vladislav 
Published: March 2011

AbstractPhoto‐ and thermoinitiated radical polymerization was investigated in solution and micelles of cationic surface‐active monomers in water. Kinetics of this process depend on the structure of micelles. Polymerization proceeds in aqueous solution of monomers, in their lamellae and spheric micelles, but doesn't occur in anisotropic ones. The polymerization rate in spheric micelles increases with the decrease of counterion size in the “head” and/or the length of the “tail” in monomer molecule. This results from the decrease of the rate of bimolecular termination reaction due to the increase of the density of micelles.