bluuebunny/crossref_metadata_2025 huggingface dataset:
Gelation of an epoxy resin and percolation theory
Authors: Serrano D. , Peyrelasse J. , Boned C. , Harran D. , Monge Ph.
Published: March 2011

The percolation theory has been applied to the isothermal hardening of the TGDDM‐DDS system (tetraglycidyldiaminodiphenyl‐methane‐diaminodiphenylsulfone). At each temperature, the variations of viscosity as a function of the extent of reaction are well described by a percolation law. The variations of the critical threshold and of the percolation parameter with temperature may be explained by a modification of the reaction mechanism. The percolation threshold is in agreement with the gel point defined on the experimental curves of the logarithm of loss modulus as a function of time log G″ = f(t).
Microwave crosslinking of epoxy/aromatic diamine systems: Process and characterization of the networks
Authors: Thuillier Françoise Marie , Jullien Henri
Published: March 2011

In order to determine the influence of the dielectric field intensity on the crosslinking reaction under microwaves, pulsed waves were used to cure epoxy‐amines systems, without catalyst. Cured resins were studied by Fourier transform infrared spectroscopy, 13‐C nuclear magnetic resonance and dynamic mechanical thermal analysis. Structural and mechanical properties were found to be influenced by parameters as pulse repetition period and peak pulse power.
Isocyanate blocking agents use in polyurethane processing
Authors: Camberlin Y. , Michaud P. , Pesando C. , Pascault J. P.
Published: March 2011

Difunctional isocyanates blocked with ϵ‐caprolactam and oximes are tested as curing agents in poly‐(urethane‐ureas) prepregs formulations. With ϵ‐caprolactam blocking agent the temperature of dissociation is around 20–40°C higher than with 2‐butanone oxime. Polymerizable blocking agents are proposed for the development of thick pieces. Simultaneous interpenetrating polymer networks are prepared and their morphology and physical properties are investigated using different technics.
Novel high temperature resins based on bis(4‐maleimido‐phenyl)methane
Authors: Zahir S. , Chaudhari M. A. , King J.
Published: March 2011

A novel high temperature thermosetting resin system based on the addition polymerization of bis (4‐maleimidophenyl)methane and o, o′‐diallyl‐bisphenol A is presented in this paper. This system offers the combination of easy solventless processing and the high temperature and toughness performance characteristics demanded for the fabrication of C‐fibre laminates. The mechanism of the polyaddition reaction is unusual. In a first step an ENE addition reaction of the maleimide to the allyl group occurs to give a 1:1 adduct with a propenyl phenol type of structure. This is then followed by a Diels‐Alder addition reaction of another maleimide functional group to the ENE adduct (by the so‐called Wagner‐Jauregg reaction) to give a densely crosslinked polymer with glass transition temperatures well over 280°C.
Retardation and relaxation behaviour of poly (ether‐block‐amide)s (PEBA) copolymers by thermally stimulated creep (TSCr) and current (TSCu)
Authors: Demont Philippe , Chatain Daniel , Lacabanne Colette , Glotin Michel
Published: March 2011

The retardation and relaxation behaviour of poly(ether‐block‐amide)s PEBA copolymers was investigated as a function of hard polyamide sequence length by using thermally stimulated creep (TSCr) and Current (TSCu). Two primary TSCr and TSCu peaks, called ßPE and ßPA were observed in the temperature range 150–300 K. The “low temperature” peak ßPE was characterized by a peak position T ßPE which depends poorly upon hard segment content as the corresponding DSC glass transition temperature TgPE. The peak position TßPA of the “high temperature” relaxation showed a progressive shift towards higher temperatures as the hard segment average length was increased as it is observed in series of pure polyamide oligomers. So, complex spectra suggest that an amorphous phase separation occurs in PEBA copolymers. The TSCr ßPE and ßPA modes were analysed by thermal sampling method (TS). The elementary TSCr processes isolated in the ßPE and ßPA distributed retardation modes were characterized by retardation times following a compensation law. The comparison of activation and compensation parameters confirmed the existence of a biphasic amorphous phase in PEBA.

In TSCr spectra, an additional peak, noted α, is observed at a temperature close to the DSC melting point TmPE of the poly(tetramethylene glycol) segments.
Properties of poly(vinyl chloride) crosslinked by new difunctional reagents
Authors: Gonnu Michel , Michel Michel
Published: March 2011

Alkaline and alkaline earth salts of either dimercaptans obtained by duplication of o‐mercaptobenzoic acid with α, ω‐diols or of o‐mercaptobenzoic acid have been synthesized. Their efficiency has been studied with respect to induction time before change in melt viscosity and crosslinking rate assessed with Haake plasticorder equipped with a Rheomix 600 internal mixer. Then efficiency with respect to crosslinking was also characterized by the assessment of the insoluble fraction in tetrahydrofuran.

Mechanical properties of uncrosslinked and crosslinked PVC were compared at different temperature through either static tests with high strain as creep and tensile tests or dynamic test in the elastic domain.

Except for creep resistance, crosslinking does not improve mechanical properties of plasticized PVC at temperature lower than 80°C if insoluble fraction in tetrahydrofuran is lower than 100 % by weight. Because chemical crosslinking leads to the existence of two interpenetrated networks, a physical one and a covalent one, the temporary physical network governs the properties until the melting of ordered domains, whereas the covalent network governs the properties if temperature rises above the melting temperature of the crystalline populations. To improve mechanical properties of crosslinked PVC at room temperature, the crosslinking density of the covalent crosslinks must be higher than the density of physical crosslinks. Such a situation is reached if insoluble fraction in tetrahydrofuran becomes 100 % by weight.
Ionomer‐like materials based on 4‐vinylpyridine copolymers
Authors: Jacovic M. S. , Favier J. C. , Janah H.
Published: March 2011

The purpose of this study is to examine the synthesis and to compare the rheological behaviour of ionomer‐like materials obtained by complexation of 4VP residues in statistical and block copolymers with ZnCl2. For statistical copolymers n‐butyl methacrylate was chosen as comonomer, while triblock copolymers involved butadiene (as central sequence). In spite of a different distribution of the 4VP residues along the chains, the complexed copolymers exhibited generally a rheological behaviour typical of that of ionomers. However, owing to this distribution and the poly‐dispersity, the morphology is quite different. The properties of statistical copolymers resulted from the formation of a mixture of multiplets and clusters. For the block copolymer, the Tg of the rubbery phase is close to that of polybutadiene (−84°C), but no relaxation is observed below 230°C and a two‐phase model is adequate in this case. The very large increase of the rubbery plateau is typical of that of a vulcanized rubber.
Synthesis and characterization of model block‐graft copolymers via anionic polymerization: Introduction of poly(isoprene) and poly(ethylene oxide) as graft chains
Authors: Se Kazunori , Watanabe Osamu , Isono Yoshinobu , Fujimoto Teruo
Published: March 2011

New architectural graft copolymers were prepared, that is, the graft chains were situated in terminal or center position of the backbone chain. These graft copolymers were termed block‐graft copolymers. Two different block‐graft copolymers were prepared from a “grafting onto” process and a “grafting from” process via living anionic polymerization. These backbone chains are poly(styrene), and the graft chains are poly(isoprene) and poly(ethylene oxide). The polymers were characterized by GPC measurements, osmometry, and ultracentrifugation. The block‐graft copolymers formed fine microphase separation structures. It was a morphological feature that an apparent volume fraction of the graft to the backbone might be higher than the real volume fraction.
The effect of photostabilizers on polymeric insulation used at high voltages
Authors: Bamji Soli , Bulinski Aleksander , Densley John
Published: March 2011

Polymeric insulation used in high voltage applications and subjected to divergent electric fields emits ultraviolet radiation due to electroluminescence. The chromophores present in the polymer initiate photo‐degradation of the material and, in dry environment, this leads to electrical treeing which causes premature failure of the insulation. The role of photostabilizers which can limit the photodegradation caused by ultraviolet radiation is studied for LDPE containing the usual and decreased concentration of air. Degassing or impregnating the polymer with an inert gas decreases the concentration of oxygen and prolongs the time to tree inception because the probability of forming excited or anionic oxygen is reduced.
Block copolymers with LC‐segments
Authors: Heitz W.
Published: March 2011

Liquid crystalline main chain polymers have outstanding properties concerning their modulus, thermal expansion, shear viscosity, and flame retardant behavior. It is of interest to introduce these properties into other polymers by the synthesis of block copolymers.
Influence of lateral substituents on thermal behavior and solubility of aromatic LC‐polyesters
Authors: Schmidt Hans‐Werner
Published: March 2011

Structure ‐ property relations of substituted para‐linked aromatic homopolyesters are reported. Thermotropic liquid‐crystalline substituted poly (1,4‐phenylene terephthalate)s with phase transition temperatures less than 230 °C and good solubility in common organic solvents have been synthesized. If a noncoplanar 2,2′‐disubstituted biphenylene moietyis combined with a monosubstituted phenylene moiety with sufficient bulky substituent, polyester with similar properties were obtained. Although these polyesters are soluble up to high concentrations, no lyotropic liquid‐crystalline behavior was observable.
Mesophase structure of flexible‐chain polymers
Authors: Antipov Evgenij , Kuptsov Sergei , Kulichikhin Valerij , Tur Dzidra , Plate Nikolaj
Published: March 2011

A structure of polyethylene (PE) and poly[bis(2, 2,2‐trifluoroethoxy)phosphazene] (PPh) has been studied by means of the X‐ray diffraction technique, scanning electron microscopy and differential scanning calorimetry. The polymers under investigation are examples of the organic and inorganic mesophase flexible‐chain polymers not containing the mesogenic groups. When heated above the melting point both polymers form the condis crystal mesophase state which is stable in a wide temperature range. The PE mesophase reveals the pseudohexagonal structure, while the structure of mesophase PPh has some peculiarities arising from the sharp increase in the chain stiffness within a certain temperature range. The PPh mesophase structure is characterized by the perfect one‐dimensional long‐range order of the monomolecular layers and by the short‐range order only along the two other directions within the layer. This structure may be due to the difference between the interactions of the inorganic backbones and regularly alternating side trifluoro‐ethoxy groups.
The cyclolinear polyorganosiloxanes ‐ a new class of mesomorphic polymers
Authors: Godovsky Yu. K. , Makarova N. N. , Kuzmin N. N.
Published: March 2011

The paper summarizes the recent achievements concerning the influence of the chemical structure and rigidity of cyclolinear polyorganosiloxane chains on the glassy, crystalline and mesophase behaviour with a special emphasis on the temperature range of mesophase stability and some thermal, X‐ray and optical characteristics of their mesophase state. The packing of macromolecules in the mesophase state is suggested.
Solid‐state polymerization of diacetylenes under the action of outside forces on crystalline monomer lattice
Authors: Gerasimov G. N. , Pankratov A. N. , Orlenko A. P. , Kozlova N. V. , Sinevitch E. A. , Teleshov E. N.
Published: March 2011

The polymerization of crystalline diacetylenes TS and DCH with different lattice structure was studied under high hydrostatic pressures (up to 4 kbar). It was shown that pressure increases the deformation of chain growing in monomer crystal. The features of such deformation depend on lattice structure that governs the influence of pressure on polymerization rate. We studied also polymerization of diacetylene HD crystals obtained in the pores of stretched polymer (PP). The field of polymer matrix influences the crystal state and the rate of polymerization. It was shown that the interaction of monomer crystals with the matrix leads to growth of more strained chains in these crystals.
Dielectric and pyroelectric properties of disubstituted diacetylenes
Authors: Dormann Elmar , Gruner‐Bauer Petra , Strohriegl Peter
Published: March 2011

The dielectric and pyroelectric properties of monomer and polymer single crystals of substituted diacetylenes carrying polar side groups are presented for four examples: NP/4‐MPU, TS/FBS, DNP and IPUDO. Large and anisotropic permittivities are generally observed. The symmetrically disubstituted diacetylenes IPUDO and DNP show spontaneous electric polarization despite of their symmetric molecular unit in polymer and/or monomer crystals at room or low temperature, respectively. Polar crystals of the unsymmetrically substituted diacetylenes NP/4‐MPU and TS/FBS can be grown from appropriate solvents. However, polymorphism is an obstacle to a systematic tailoring of dielectric properties of diacetylene single crystals.
Synthesis, structure, and properties of aromatic polysulfides
Authors: Sergeev Vladimir A. , Nedelkin Vladimir I. , Nesmeyanov A. N.
Published: March 2011

Polycondensation of haloaromatics and sodium sulfide has been studied. An increase in reactivity of functional groups, a change of the composition of the elementary polymeric unit with a change of the relative amounts of the monomers, and a key role of side‐reactions, i.e. intra(molecular) and macrocyclisation, have been revealed. Low‐melting isomeric poly(phenylene sulfides), as well as their derivatives, reactive telechelic oligomers, have been prepared. New methods of preparation of poly(arene sulfides) by transarylation of diphenyl sulfide, polymerisation of cyclic aromatic sulfides, or by direct polycondensation of arenes with sulfur under the action of AlCl3, as well as by polycondensation of aniline with sulfur in the absence of catalysts have been suggested. Structures and properties of newly prepared polymers have been studied.
Structure and superstructure of carbon fibres
Authors: Ruland W.
Published: March 2011

The structure of carbon fibres consists of stacks of carbon layers oriented parallel to the fibre axis. From X‐ray wide‐angle scattering studies (WAXS) one obtains various structural parameters characterizing the perfection of the stacking and the orientation of the layers. The latter is quantitatively related to the tensile modulus of the fibres. Small‐angle scattering studies (SAXS) are used to determine size, shape and orientation of microvoids. For carbon fibres with high heat treatment temperatures (HTT), a correlation between microvoid content and elongation at break is observed which indicates an optimum value for the microvoid content. Electrochemical intercalation is used to obtain information on the accessibility of the carbon layer structure.
Modern aspects of multicomponent copolymerization, quantitative theory
Authors: Kuchanov Semen I.
Published: March 2011

It is proposed to consider multicomponent copolymerization at high, monomer conversions proceeding from the theory of dynamic systems. A general approach based on such a consideration is suggested. This approach permits to make theoretical predictions of some fundamental properties of multicomponent copolymers taking data of only binary systems. The efficiency of this approach is clearly shown while predicting clarity and heat resistance of some terpolymers.
Complex formation and dynamics in polymer melts
Authors: Stadler Reimund , Freitas Liane De Lucca
Published: March 2011

The viscoelastic properties of polymer chains with a few number of pairwise associating functional groups are studied as a function of polymer molecular weight, degree of substitution and polymer concentration. As a model system, polybutadienes of narrow molecular weight distribution are used as starting materials. These polymer chains are modified by introducing few 1,2,4‐triazolidine‐3,5‐dione (urazole) groups U. These form defined dimeric hydrogen bond complexes U + U → U2.
Stabilisation of polymers by catalytic antioxidants
Authors: Scott Gerald
Published: March 2011

Two types of catalytic antioxidant are now recognised. The first involves the catalytic destruction of hydroperoxides to non‐radical products and the second consists of “stable” redox couples with the ability to remove both alkyl (CB‐A) and alkylperoxyl (CB‐D) radicals in autoxidising systems. The conditions under which both types of antioxidant can operate effectively are reviewed and the limitations to their activity are outlined.
Some aspects of polyethylene photooxidation
Authors: Gugumus François
Published: March 2011

The hydroperoxides produced by thermal oxidation of LDPE films were used to study their photolysis. Product analysis, kinetics of hydroperoxide decomposition and product formation as well as experiments with model compounds point to new mechanisms of hydroperoxide photolysis. Intermolecular as well as intramolecular decomposition mechanisms are proposed. In polyethylene, these reactions are essentially non‐initiating. In addition, it is confirmed that ketones such as those formed by oxidation of polyethylene do not have a significant initiating effect. Reactions of excited charge‐transfer complexes polyethylene‐oxygen are proposed to account for initiation of photo‐oxidation. One of these reactions yields trans‐vinylene groups and hydrogen peroxide whose direct decomposition or subsequent photolysis will generate hydroxyl radicals. It is found that this reaction is quenched very efficiently by small amounts of HALS (Hindered Amine Light Stabilizers) and by amines in general. It is postulated that quenching is due to energy transfer from the charge‐tranfer complex polymer‐oxygen to a charge‐transfer complex HALS‐oxygen or amine‐oxygen. The data available so far support such a mechanism.
Specific features of polymer oxidation
Authors: Shlyapnikov Yu. A.
Published: March 2011

A polymeric substance consists of long chainlike molecules forming complex non‐uniform structures. Both anisotropy of macromolecules and irregularity of their packing result in a marked deviation of polymer oxidation process from that of low‐molecular compounds.
Quantum effects in molecular dynamics and fracture kinetics of polymers
Authors: Slutsker A. I.
Published: March 2011

Molecular dynamics in crystallites of a number of polymers, such as polyethylene, nylon‐6, poly‐(vinyl alcohol), was studied at temperatures ranging from 4.2 to 400 K using the X‐ray diffraction technique. Thermal expansion of the lattice was measured by the temperature‐induced displacements of diffraction maxima. The thermal expansion coefficient was found to grow from 0 to ∼10−4 K−1, this fact being the evidence of the quantum statistics in the vibrational dynamics of straightened molecules over the whole temperature range. Characteristic temperatures of vibrations were estimated. The kinetics of fracture was studied using highly ‐ oriented nylon‐6 and KEVLAR‐49 fibers. Tensile strength (σr) was measured as a function of loading rate σ and temperature (T) in the range from 4.2 to 400–600 K. The observed specific features of the σr(σ) and σr(T) curves at low temperatures correspond to tunnel scission of stressed chain molecules.
Stabilization of low density polyethylene with sterically hindered derivatives of 4‐hydroxybenzoic acid
Authors: Seiffarth K. , Baeseler M. , Dahlmann J.
Published: March 2011

In comparison with other commercial light stabilizers, sterically hindered 4‐hydroxybenzoates are found to possess only a weak power, if they are used for low density polyethylene (LDPE). It is known that these benzoates exhibit significant synergistic effects together with 2‐hydroxybenzophenones and hindered amine light stabilizers in light stabilization of high‐density and linear low‐density polyethylene. The light stabilizing efficiencies of the above mentioned stabilizers and mixtures of them in different weight ratios are determined by weathering in a Xenotest 150 unit. Only small synergistic effects of about 15 −30% are found for light stabilizing LDPE. The effects can be explained by the stabilizing efficiency of sterically hindered 4‐hydroxybenzoates during processing. Combining of light stabilizing structure components like 2‐hydroxy‐benzophenone resp. 2, 2, 6, 6‐tetramethylpiperidine with sterically hindered 4‐hydroxybenzoates in one stabilizer molecule only, from the first mentioned combination, results a powerful light stabilizer. Its efficiency is the sum of the powers of the single structure components.
The role of air in the radiolytic degradation of polycarbonate
Authors: Gupta Mool C. , Pandey Rajbahadur R.
Published: March 2011

Bisphenol A polycarbonate (PC) was irradiated with Co‐60 γ‐rays at room temperature in presence of air or nitrogen. Changes were followed by IR and NMR spectroscopy as well as GPC, X‐ray diffraction, melting temperature, DTA, and isothermal TG. The changes observed include chain scission, chain branching/cross‐links, decrease in thermal stability, crystallinity and scission of the product. However, there are some differences in samples irradiated in presence of air as opposed to those irradiated in nitrogen, but many changes are similar. Air accelerates the radiolytic degradation of PC. The radiochemical yield of chain scission, G(s), increased to 0.20 from 0.13; the chain branching/cross‐links are less numerous as compared to those after irradiation in nitrogen the thermal stability decreases along with the temperature of that rate of maximum mass loss, crystallinity and the melting temperature. The chemical products in both air and nitrogen irradiations are almost identical. The formation of these products could be explained by multiple pathways‐free radical formation and by ring as well as side chain attack. The studies suggest that Fries' rearrangement is not an important pathway during the radiolytic degradation as compared with photodegradation.
Ageing characteristics of styrene‐butadiene rubber containing some sulfanilyl derivatives
Authors: Abdel‐Bary E. M. , Makar S. M. , Mousa A. N.
Published: March 2011

Styrene‐butadiene rubber (SBR) mixtures containing some sulfanilyl derivatives have been prepared. The effect of the latter compounds on the rate of vulcanization of SBR formulations as well as the ageing characteristics of corresponding vulcanizates were evaluated. In all cases, the efficiency of the compounds under investigation was correlated with their chemical structure. It was found that vulcanizates containing sulfanilyl thiourea compounds deteriorate to a lesser degree than those containing N‐isopropyl‐N'‐phenyl‐1, 4‐phenylenediamine (IPPD) as conventional antioxidant. In addition, the effect of the type of carbon black on the efficiency of such compounds as antioxidants was evaluated.
Mechano‐ions produced by mechanical fracture of solid polymers
Authors: Sakaguchi Masato , Kashiwabara Hisatsugu
Published: March 2011

It is said that the free radical caused by C‐C‐bond scission, homogeneous scission, is produced by mechanical degradation. In addition to free radicals, ionic species are produced due to the mechanical destruction of the polymers. Studies in our group concerning this problem are summarized. When the polymers were ground with tetracyanoethylene (TCNE) powder in a vibration glass ball mill in vacuum in the dark at 77 K, the TCNE anion radical (TCNE\documentclass{article}\pagestyle{empty}\begin{document}$ \bar . $\end{document}) was detected by electron spin resonance (ESR) method. The TCNE\documentclass{article}\pagestyle{empty}\begin{document}$ \bar . $\end{document} is formed by the abstraction of electrons by TCNE from the anion produced by a heterogeneous bond scission of carboncarbon bonds in the polymer main chain. The identification of TCNE\documentclass{article}\pagestyle{empty}\begin{document}$ \bar . $\end{document} was carried out by the spectral simulation on the basis of an anisotropic hyperfine tensor including a forbidden transition term. Several polymers were examined; polyethylene, polypropylene, poly(tetrafluoroethylene) and poly(vinylidene fluoride). The ratio of ionic species and free radicals is discussed.
The impact of external conditions on the structure of perfluorinated ion‐exchange membranes, determined by means of Mössbauer spectroscopy
Authors: Chibirova F. Kh. , Timashov S. F.
Published: March 2011

To ascertain the changes taking place in their submicrostructure after accelerated tests under the conditions of chlorine electrolysis, perfluorinated ion‐exchange sulfocationic membranes hydrolyzed by different techniques were investigated by means of Mössbauer spectroscopy on a Fe57 nucleus introduced into a membrane as a Fe3+ counter‐ion and precipitated into its submicropores in the form of superparamagnetic hydroxide particles. Information on the submicroporosity of the investigated polymeric membranes was thus obtained. Different techniques of membrane hydrolysis and the processes of both the passage of current (I ∼ 0.3 A/cm2) through them and of precipitation have been established to change radically the characteristic size of submicropores in the membrane, as well as their size distribution. Thermal treatment in air at T ≈︁ 423 K is shown to be accompanied by the Fe3+ ← Fe2+ ion reduction in the membrane.
Modification of polyolefins by antioxidants and stabilisers
Authors: Scott Gerald
Published: March 2011

The limitations of conventional antioxidants and stabilisers in polymers are associated with their migration into contacting fluids. This leads to toxicity in packaging and medicinal applications and loss of effectiveness in many engineering uses of polymers. Reactive processing procedures are being increasingly used to chemically attach antioxidants to polymers and the most successful of these involve the synthesis of bound antioxidant concentrates which can be used as macromolecular adducts for normal polymers. Present evidence suggests that a polymer modified by substantial concentration of antioxidants loses its physical identity and can be used in a range of other polymers. Future developments in which the additives are 100% bound to the polymer substrate are discussed.
Orientational drawing of polymers and their blends
Authors: Kuleznev Valeri N. , Vlasov Stanislav V. , Pirogovskaya M.
Published: March 2011

Pecularities of deformation of two‐phase blends is considered depending on drawing conditions and mechanical properties of each phase.

Significant anisotropy of mechanical properties of polymer blends film can take place because of particle orientation of dispersed polymer. This significant anisotropy exists also when there is no orientation of macromolecules in each phase. Possibility is demonstrated to regulate properties of each phase in polymer blends by addition of selective plasticizer which can act only on one polymer phase in two‐phase polymer mixture.
Localization of oxidation in polypropylene
Authors: Billingham N C
Published: March 2011

We review some of the available evidence to suggest that the oxidation of polypropylene is not a homogeneous process but is localised at several levels. Optical microscopy of oxidised polymer shows regions of high oxidation on the micron scale, sometimes associated with uneven distribution of catalyst residues. Atactic polymer is shown to oxidise more rapidly than isotactic and to be redistributed in the isotactic polymer during melt crystallization. Atactic polymer is shown by GPC to undergo random scission with the formation of terminal carbonyl groups; in contrast, the oxidation of isotactic polymers is non‐random. Finally, evidence is discussed to show that both the initiation of oxidation by peroxide decomposition and its termination by radical recombination follow complex kinetics.
Stabilization and modification op polyolefins used in medical articles
Authors: Gorelik B. A. , Sokolova L. A. , Grigoriev A. G. , Koshelev S. D. , Semenenko E. I. , Matiushin G. A. , Rychla L.
Published: March 2011

The thermo and radiation aging of polyolefins and their blends were studied. It was shown that near the inversion point of phase there is the most marked interaction between continuous and dispersed components of blend. This interaction results in an improvement of blend stability higher than expected. The investigation of the influence of supermolecular structure of PP stability revealed the small spherulite samples are more stable under irradiation in air than large spherulite ones. The possibility of obtaining composites of polyolefins and silicon liquids urns shown.
Photoinitiated crosslinking of polyethylene
Authors: Zamotaev P. V.
Published: March 2011

The main types of polyethylene (PE) crosslinking photoinitiators were examined. It was shown that the aromatic ketones and quinone are the best types of the photoinitiators for practical usage. The quantum yields of initiators' photoreduction and the crosslinking yields per one initiator molecule at the different stages of PE photochemical crosslinking were measured. The photoinitiators effectiveness dependence on their chemical structure was considered. The influences of the UV‐irradiation intensity, temperature, photoinitiators' concentration, some copolymers, polyfunctional monomers, peroxides additives on the photocrosslinking and photooxidation processes in PE were investigated.
The latest achievements in the field of degradation and stabilization of vinyl chloride (CO)polymers
Authors: Minsker K. S.
Published: March 2011

The achievements of the past years are associated, in the first place, with solution of the problems of the abnormally low stability and the new ways of effective stabilization of vinyl chloride (VC) (co)‐polymers. A generalized approach to the quantitative description of the degradation of VC polymers, taking into account the short‐ and long‐range effects of neighbouring groups, which are fundamental for the chemistry of the halogen‐containing polymers, has been elaborated. The principal effects of the polymer phase state and the solvent nature on the degradation rate of VC (co)polymers have been elucidated. This fact predetermines different approaches to the stabilization of the polymer products in creation of rigid and plasticized compositions, including those in solutions.
Vinyl chloride polymers and their use in polymer blends
Authors: Braun Dietrich , Böhringer Bertram
Published: March 2011

A short introduction to polymer‐polymer miscibility and to the prediction of the miscibility of polymers is given. The four main types of polymer‐modified poly(vinyl chloride) (plastification, impact modification, processing aids and heat deflection temperature modification) are explained by examples. The thermal stability of poly(vinyl chloride) in such blends is discussed; the effectivity of tin‐stabilizers may be higher in such blends than in pure poly(vinyl chloride).
Transport of organic vapors and liquids in poly(vinyl chloride)
Authors: Berens Alan R.
Published: March 2011

This paper reviews research since 1980 on the equilibria and kinetics of transport of small organic molecules in rigid and plasticized PVC. The forms of both the solubility isotherms and the sorption kinetics are shown to change as the PVC/penetrant system undergoes a glass‐rubber transition with an increase of either temperature or penetrant concentration. The isotherms are of “dual‐mode” form (concave to the activity axis) for the glassy state, and show an inflection to Flory‐Huggins form when the penetrant concentration exceeds Cg, the transition composition at the experimental temperature. The solubility at a given penetrant activity is governed primarily by the PVC/penetrant interaction parameter, χ. Sorption kinetics are Fickian for conditions producing small changes of concentration in either the glassy or rubbery state. For sorption into initially unplasticized PVC, kinetics are anomalous if the final penetrant concentration is between about Cg/2 and Cg, and Case II if Cg is exceeded. The magnitude of the Fickian diffusion coefficients depends largely on the geometric factors of molecular size and shape of the penetrant; this dependence is much steeper in the glassy than in the rubbery state. Recent results show that carbon dioxide displays both high diffusivity and substantial solubility in PVC under high pressure; this combination makes compressed CO2 uniquely useful in accelerating the absorption of low‐molecular‐weight additives into PVC.
Estimation of the degree of fusion of rigid PVC from thermal analysis measurements
Authors: Teh J.W. , Rudin A. , Cooper A.A. , Batiste J.L.H.
Published: March 2011

PVC that has been processed exhibits two endothermic peaks in DSC heating curves. These endotherms are separated by a temperature. Tc, which is characteristic of the maximum temperature reached in prior processing. The relative value of the lower temperature endotherm has been proposed as a measure of degree of gelation of unplasticized PVC. This measure is not exact, however, because it does not reflect the extent of breakdown of primary PVC particles. An alternative DSC measurement technique is proposed that reflects the degree of fusion more accurately. The nature of the various endotherms that are observed is a subject of speculation in this article.
Fire performance of poly(vinyl chloride) and its relation to fire hazard
Authors: Hirschler Marcelo M.
Published: March 2011

This paper discusses the most important parameters in terms of fire hazard and shows how PVC fares in relation to other polymers. The fire properties specifically addressed are: ignitability, flammability, flame spread, rate and amount of heat release, mass loss rate, smoke release and toxicity. Hydrogen chloride decay is also commented on, because it affects the toxicity of PVC smoke. The individual parameter most relevant to fire hazard is heat release. The two most useful tools for measuring rate of heat release (viz. the OSU and Cone calorimeters) are described. Results obtained from them are discussed.

Smoke can best be measured by combined parameters from rate of heat release calorimeters, rather than in the traditional static NBS smoke chamber.

Toxic hazard is being addressed by recognition that most smokes are of similar toxicity, so that the mass loss rate will, generally, govern the toxicity of smoke.

Not all fire tests are equally good representations of the probable consequences of a full‐scale fire. Fire hazard assessment is best carried out based on those test results most relevant to real fires; they can be obtained from small and full‐scale experiments and fire models.

The fire performance of PVC is excellent; PVC products generally represent low fire hazard in a scenario.
Rheological aspects in degradation and stabilization of poly(vinyl chloride)
Authors: Gonnu M. , Verney V. , Michel A.
Published: March 2011

Viscoelastic properties of PVC depend on temperature because of the existence of a physical temporary network. The main consequence of gel state within the range of usual processing temperatures is a heterogeneous dispersion of stabilizers. PVC is most sensitive to the dehydrochlorination in the state of the intermediate flow between particulate and molecular flow because of radicals arised from polymer chain scission caused by shear stress.
Properties of poly(vinyl chloride) blends with polycarbonates and chlorinated polyethylene
Authors: Braun D. , Böhringer B. , Herth J.
Published: March 2011

The miscibility of polycarbonates derived from Bisphenol A or 2,5,2′,5′‐tetramethyl‐Bisphenol A with poly(vinyl chloride), chlorinated poly(vinyl chloride), and vinyl chloride‐vinylidene chloride copolymers has been investigated. In miscible blends a shift of the position of the carbonyl absorption in the IR spectra indicates dipolar interactions between the polymers. The miscibility of chlorinated polyethylenes and reduced poly(vinyl chloride)s among each others demonstrates besides the importance of polar groups the influence of their distribution within the polymer chains for the compatibility of the polymers. The investigations on the miscibility have been carried out by differential scanning calorimetry, and by casting films with microscopical observation of the resulting structures.
Factors affecting dimensional stability of exterior vinyl products
Authors: Rabinovitch Elvira B.
Published: March 2011

Dimensional stability problems such as warpage, bowing, buckling and other changes in shape and size may occur when exterior building products (siding, windows) are heated by the sun. This paper describes the effects of material properties such as coefficient of thermal expansion, heat deflection temperature and heat buildup, caused by the sun, on dimensional stability of exterior building products. This paper also discusses the effect of profile design, such as thickness and width, on dimensional performance.
Study of poly(vinyl chloride) by inverse gas chromatography
Authors: Hattam P. , Cheng W. , Du Q. , Munk P.
Published: March 2011

Inverse gas chromatography (IGC) was used to investigate PVC to determine what information can be gathered using the technique. Standard IGC using a column of PVC‐coated support was performed at 120°C. The polymer‐solvent interaction coefficients for 25 probes were obtained and the polymer solubility parameter was determined. A 50/50 blend of PVC/poly(∈‐caprolactone) was studied to determine the polymer‐polymer interaction coefficient B23 and the solubility parameter of the blend. A nonstandard analysis using bulk, suspension‐polymerized PVC as the column packing was performed at 40°C, and the retention behavior compared with a computer simulation of Langmuir type adsorption.
Relaxation properties of plasticised poly(vinyl chloride) and PVC blends
Authors: Suvorova A.I.
Published: March 2011

The temperature‐frequency dependence of dielectric parameters for several PVC‐plasticizer systems and PVC blends was obtained. Kinetic and activation parameters and α‐relaxation spectra were estimated. The increase of the polar group number and size in the plasticizer molecules results in the narrowing of the relaxation spectra and in the increase of inner mobility of PVC segments. It was found for PVC‐ABS and PVC‐Paraloid blends that all relaxation characteristics depend on the miscibility of components. The results were also confirmed by the cloud point data.
Interaction of components in the poly(vinyl chloride) pilled in polymerization stage
Authors: Yushkova S.M. , Tager A.A.
Published: March 2011

The enthalpies of the interaction between PVC or its copolymers and different fillers introduced into the polymerization mass were estimated by the microcalorimetric techniques. For highly filled compounds, the strength of the polymer ‐ filler interaction depends on the chemical nature of both components. The determination of the interaction enthalpy makes it possible to choose a polymeric cover providing for the best interaction and to calculate the lowest amount of the polymer covering entirely the filler surface.
The structure of the poly(vinyl chloride) chain. I. Conformation of 2,4‐dichloropentane
Authors: Burda J. , Lukáš R.
Published: March 2011

Using semiempirical quantum chemical CNDO/2 and MNDO methods, hindered rotations of the carbon chain of 2,4‐dichloropentane stereoisomers were studied. The results obtained confirm the experimental finding that the most important structures of the racemic and meso form of 2,4‐dichloropentane are TT‐racemo (TT‐syndio), GG‐racemo (GG‐syndio) and TG‐meso (TG‐iso) conformers. A more detailed analysis of non‐bonding interactions showed, however, that the energetically most advantageous structures are the partly geometrically shifted TT‐syndio and TG‐iso conformers. In the case of the TT‐syndio conformation MNDO predicts a rotation of the carbon chain by 13.254°, which for the poly(vinyl chloride) chain explains the helical structure of syndiotactic sequences.
Emulsion polymerization of vinyl chloride, potassium persulfate decomposition
Authors: Georgescu Cecilia‐Speranţa , Butucea Victor , Sarbu Adrians , Ionescu Adrians , Deaconescu Ion , Hagiopol Cornel
Published: March 2011

Decomposition of potassium persulfate in sodium dodecyl sulfate solutions (of concentrations under and above CMC) and in the presence of poly(vinyl chloride) and vinyl chloride was studied. The decomposition rate has a maximum close to the CMC value of the final solutions. On the basis of experimental data a hemolytic mechanism in which a radical derived from dodecyl sulfate participates is proposed.
Dynamic ‐ mechanical properties of poly(oxypropylene)di‐amine‐diepoxide and poly(oxypropylene)triamine‐diepoxide networks and their relationship to the structure of elastically active network chains
Authors: Ilavský Michal , Hrouz Jaroslav , Šomvársky Ján , Dušek Karel
Published: March 2011

The effect of the initial mole ratio of reactive components on the shape and position of dynamic mechanical functions in the main transition and rubbery region was investigated for two series of networks made from poly(oxypropylene)diamine (D‐400)‐diglycidyl ether of Bisphenol A (DGEBA) and poly(oxypropylene)‐triamine (T‐403)‐DGEBA. The networks were prepared with an excess of amine groups up to the highest conversion of epoxy groups; the ratio rH = 2 [ NH2 ]0/ [E]0 ranged from unity to 2,1 for networks from D‐400 and from unity to 3,5 for networks from T‐403. By using the theory of branching processes, structural parameters of these networks were calculated, in particular, the molecular weights of elastically active network chains (EANC's) including dangling chains, of backbone EANC's and of dangling chains. A comparison between theory and experiment led to the following conclusions: (a) the mechanical behaviour in the rubberlike region can be described either by using an affine deformation model (front factor A = 1), or by means of a phantom model (A = (fe‐2)/fe, fe being functionality of the crosslink) with the contribution of permanent interchain interactions; (b) the temperature and frequency position of viscoelastic functions in the main transition region is conclusively affected by the concentration of EANC's; (c) the shape of visco‐elastic functions, especially of retardation spectra in the main transition and rubbery region, depends on the detailed structure of EANC's, but it cannot be decided from the result which structural parameter has the strongest effect on the shape of the functions.
Calculation of network parameters of crosslinked markovian polymer chains
Authors: Miller Douglas R.
Published: March 2011

Linear copolymer chains form in a chain‐addition reaction which includes initiation, homopropagation, crosspropagation, and termination by transfer, disproportionation, and combination. Chain growth obeys the Markov property. Multiple types of monomeric units are involved; some types have reactive sites, others do not. These chains are then crosslinked by a small monomer crosslinker which may have a polydispersed distribution of functionality and mass. The resulting network consists of soluble, pendant, and elastically effective fractions. Using classical Markov chain analysis techniques, various statistical properties of the polymer chains are computed. The gel point, weight fractions and other network properties can then be calculated. The effects of unequal rates of chain homopropagation and crosspropagation can be observed.
Siloxane network structures: Kinetics of gelation observed using nuclear magnetic resonance
Authors: Girard O. , Guillermo A. , Cohen‐Addad J. P.
Published: March 2011

Transverse nuclear magnetization properties of protons are investigated during the gelation of short poly(dimethylsiloxane) chains. Both the kinetics of the reaction and the amount of the gel fraction are characterized. The sol and gel fractions are distinguished “in situ” during the whole process by performing pseudo‐solid spin‐echoes and through a simple analysis of the relaxation shape.
Synthesis and properties of model ‐ micronetworks
Authors: Antonietti Markus , Bremser Wolfgang , Fölsch Karl J. , Sillescu Hans
Published: March 2011

Microgels are small network particles with overall dimensions in the 100nm‐region. Some experiments concerning the behaviour of cross‐linked matter can be more easily performed using the molecular nature of μ‐gels. In this publication, the synthesis and characterization by light and neutron scattering and dynamic‐mechanical shear experiments of two different types of μ‐gels are presented.
Showing a rheological effect of gelation on epoxy‐amine systems
Authors: Senhaji A. C. , Harran D.
Published: March 2011

The effect of gelation was studied on the rheological curves, during hardening of a resin subjected to sinusoidal shearing between parallel plates. The epoxy‐amine system was chosen for the moderate value of its maximum glass transition temperature Tg, ∞ which means that it is possible to avoid vitrification by operating at T > Tg, ∞. The shape of the variation curve of the storage modulus G' does not depend on temperature; G' obeys a single percolation law as a function of the reduced variable t/tgel. On the other hand, gelation leads to a fall in the growth rate of the loss modulus G” after the gel point. This effect increases with temperature and can become considerable at very high temperatures: in this case a minimum of G” between the gel point and the rubbery plateau can be observed. We have verified that this effect is indeed a rheological effect of gelation as it begins practically at the gel point determined on the storage modulus curves. Several qualitative conclusions are drawn, and the nature of this effect is discussed.
An alternative approach to rubber elasticity theory based on a lattice model
Authors: Schwarz Jürgen
Published: March 2011

An alternative rubber elasticity theory for bulk elastomers has been developed. It is based on the model of a cubic lattice which is filled completely with long flexible chains. The dependence of the configurational entropy on the orientation factor of Hermans has been derived for a uniaxial homogeneous orientation of the system. With the assumption of a constant stress‐optical coefficient, the dependence of the true stress Γ on the deformation λ = L/L0, with L the length of the sample, can be described approximately as τ ∝︁ in λ both for uniaxial extension and compression, which agrees quite well with experimental results on bulk elastomers.
Modelling and simulation of synthesis, microstructure and properties of emulsion copolymers
Authors: Guillot J.
Published: March 2011

Accurate investigations of batch homopolymerization and copolymerization allow to derive mechanisms for emulsion polymerization; if they are not actually general, they are assumed to be valid for a given co‐monomer system, at least. A lot of approaches have been devoted to the mathematical modelling of emulsion polymerization, with the objective to take into account all of the experimental parameters or only some of them. Many of these approaches are quite complex and assume that a huge number of parameters are known.