bluuebunny/crossref_metadata_2025_split huggingface dataset:
A heat resistant PIQ, polymer‐based interconnection using a multilevel lift‐off pillar fabrication
Authors: Sanséau P. , Schiltz A. , Nechtschein J. 
Published: March 2011

AbstractTo achieve a planar multilevel interconnection, we have developed a process using an improved lift‐off pillar fabrication technique in conjunction with a new kind of heat resistant polymer, a copolyimide‐isoindoloquinazolinedione polymer (PIQ). As spin‐on dielectric layer, the PIQ polyimide is shown to satisfy both the processing criteria and interconnection criteria (high thermal resistance, good planarization properties and excellent dielectric properties).
Findings pertaining to polyethylene photooxidation
Authors: Gugumus F. 
Published: March 2011

AbstractThe kinetics and mechanisms of photolysis of the hydroperoxides formed on thermal oxidation of polyethylene have been investigated. The difficulties to explain the results by the generally accepted decomposition mechanism based on homolytic splitting of the hydroperoxy bond are discussed. New mechanisms of hydroperoxide photolysis are proposed. The intermolecular reactions considered account for the main products found experimentally, ketones and trans‐vinylene groups. They are also in agreement with the kinetics of product formation. The intramolecular photolysis reactions envisaged seem to involve a small amount only of the hydroperoxides present in polyethylene after thermal oxidation. However, they affect directly the mechanical properties of the polymer because they involve main‐chain scission.
New approaches to reversible crosslinking in epoxy resins
Authors: Tesoro Giuliana C. , Sastri Vinod R. 
Published: March 2011

AbstractThe objective of the research is to investigate epoxy resins where crosslinks formed in curing reactions can be cleaved and reformed without significant sacrifice in resin properties. Experimental disulfide‐containing crosslinking agents have been selected for the study, including dihydrazides of dithiodicarboxylic acids (aliphatic and aromatic) and dithioaromatic diamines. Conditions for curing reactions and for subsequent cleavage of crosslinks by reduction have been determined in model systems and confirmed for a prototype epoxy resin. A comparative evaluation of cure kinetics, crosslink density, and thermal and mechanical properties has been carried out for resin cured with aromatic curing agents (dithiodianiline and methylenedianiline) and with aliphatic compounds (3, 3′‐dithiopropionic acid dihydrazide and hexamethylenediamine). It has been shown that in resin fully cured with disulfide‐containing crosslinking agents, crosslinks are ruptured by reduction, and re‐established by oxidation under mild conditions, or by reaction of thiol groups with bifunctional alkylating agents.
Thermal degradation of poly(p‐methylstyrene)
Authors: Luda Maria Paola , Guaita Marino , Chiantore Oscar 
Published: March 2011

AbstractThe thermal degradation behaviour, in the absence of oxygen, of poly(p‐methylstyrene) has been investigated. Monomer is the main product formed in the degradation process, together with different oligomers which have been identified and whose amounts have been determined. A reaction mechanism accounting for the formation of the degradation products, and similar to the mechanism established for polystyrene, is proposed. The main differences of the process comparing with polystyrene are the higher amount of monomer which is produced and the crosslinking structures which are formed at T < 400° C.
Polyfunctional esterisocyanates. Useful monomers for the synthesis of ordered polymers
Authors: Mormann Werner 
Published: March 2011

AbstractA number of mono‐ and difunctional esterisocyanates has been synthesised by the regioselective reaction of isocyanatocarboxylic acid chlorides with trimethylsilyl‐protected alcohols and phenols. The diesterdiisocyanates were reacted with short chain diols to sequential poly(diesterdiurethane)s and with piperazine to poly(diesterdiurea)s. The monoesterisocyanates were anionically polymerized to 1‐polyamides which show lyotropic liquid crystalline behaviour. The new products are characterized by spectroscopy, viscosimetry and thermal behaviour.
Rheological characterization and analysis of a bismaleimide matrix
Authors: Meissonnier Julien , Seferis James C. 
Published: March 2011

AbstractBismaleimide resins are becoming increasingly attractive as matrix materials for high‐temperature applications in continuous fiber reinforced composites. Their relative low viscosity as well as the low processing temperature makes them attractive candidates as matrices in high‐temperature applications while retaining the processing ease associated with epoxies. Traditional prepregging as well as autoclaving processes, especially for solvent free (hot melt) systems, are a viable way to proceed. However, the recent interest in toughened matrices makes these processing techniques difficult to specify and control. Specifically, during prepregging and autoclaving, the viscosity of the system must be specified from the initial stages of resin mixing through B‐staging and gelation all the way to the viscoelastic “solid” region. In this work, based on a series of well‐characterized bismaleimide resins, a generalized model for viscosity capable of describing matrix changes as it goes through the processing steps was developed. Measurements of viscosity by the different techniques were related through the model to provide a characterization scheme that may be applicable to both prepregging and lamination steps.
Thermal decomposition kinetics of polypropylene peroxides in the polymer matrix followed by ESR
Authors: Catoire B. , Verney V. , Michel A. 
Published: March 2011

AbstractOzonization creates peroxidic species, peroxides and hydroperoxides, in the bulk of polypropylene powder. Their characterization and chemical determination is delicate (135 °C in decalin). Moreover, the thermal decomposition kinetics of the reactive groups at various temperatures cannot be easily followed by usual methods. In order to follow the thermally induced radicals in the polymer matrix, we used the “spin trapping technique” in E S R. Concurrently we looked at the peroxidic decomposition exothermicity using a differential mode technique in D S C. The E S R data show that the spin trap technique can be used successfully to follow the thermal decomposition kinetics. The activation energy (100 kJ/mol) and rate constant values obtained with this technique are in good agreement with those found in the literature by other techniques. The relative thermogram technique in D S C allows to get information about peroxidic decomposition exothermicity.
Some features of the solid‐state polymerization of diacetylenes
Authors: Vinogradov G. A. , Guy M. I. , Gromov L. A. , El'Yashevitch M. M. 
Published: March 2011

AbstractSimple models of the initial polymerization stage and the polymerization kinetics are considered on the example of the solid state topochemical polymerization of diacetylenes. These models take into account the reaction specifity of the solid state process and the nonlinear character of the monomer units interactions.
Neutron and light scattering studies of polymer blends and block copolymers
Authors: Fischer E. W. , Jung W. G. 
Published: March 2011

AbstractThe structure of compatible polymer mixtures and its temperature dependence can be well described in many cases by the mean‐field approximation. Deviations with regard to the temperature dependence of the correlation length of concentration fluctuations can be explained by taking into account the spatial structure of the interaction potential. Concentration fluctuations and the microphase separation in diblock copolymers are in good agreement with theories based on the random phase approximation. In the two‐phase region the temperature dependence of the scattered X‐ray or neutron intensity is governed by the difference in the thermal expansion coefficients of the two components of the diblock copolymer. Photon correlation spectroscopy (PCS) yields valuable information on the concentration dependence of the mutual diffusion coefficient DAB.
The net distribution of elements in multiphase polymer materials via element‐specific electron microscopy
Authors: Cantow Hans‐Joachim , Kunz Martin , Klotz Stefan , Möller Martin 
Published: March 2011

AbstractApplications of the Electron Spectroscopic Imaging technique (ESI) within the field of multiphase polymer materials are discussed. Imaging with elastically scattered electrons as well as imaging with electrons with defined energy loss are presented. From the latter the net distribution of elements can be derived.Several examples are given: Glassy diblock copolymers polystyrene‐block‐poly(2‐vinyl pyridine), polyethylenes, interpenetrating networks, interdiffusion couples, blends of polystyrene and polystyrene‐graft‐poly(oxyethylene), carbon black reinforced natural rubber, and epitactic growth of poly(1‐pentenylene) on isotactic poly (propylene) surface.Visualization of the rigid amorphous phase in polyethylene is presented, as well as electron spectroscopic diffraction (ESD) of oriented PE. One of the features of ESI is due to the fact that discrimination between true morphology and artefacts is possible in an unbiased manner, even for minor details: Heavy metal staining is abandonable, and structural analysis by one element may be proved by analysis with other elements, which may be present in the sample or which may be added by chemical reaction or interaction with groups within the molecules.
Synthesis of new chelate ionites and some details of their metal ion interaction
Authors: Ergozhin E. E. , Utkelov B. A. 
Published: March 2011

AbstractThe synthetic methods for chelate ionite groups with 8‐quinolinol, 8‐quinolinethiol and some other thiols, thioethers or thioamides were developed, their sorbing and acid‐base properties being studied as well. The stability constants of complexes of metal ions with polymeric chelate groups were determined. A method to calculate the formation function of the complexes on the basis of potentiometric data was proposed. The experiments showed the synthesized sorbents to be applicable in the selective extraction of heavy metal ions from their solutions.
Interpolyelectrolyte complexes as a new family of enzyme carriers
Authors: Zezin A. B. , Izumrudov V. A. , Kabanov V. A. 
Published: March 2011

AbstractThe ability of nonstoichiometric interpolyelectrolyte complexes of dissolving in water and reversible precipitation, induced by the changes of conditions (pH, ionic strength of the solution) was used to create the reversibly soluble immobilized enzymes. The techniques of the enzyme inclusion (penicillin amidase, α‐chymotrypsin, urease etc.) in the interpolyelectrolyte complexes were worked out. It was shown that the application of the reversibly soluble immobilized enzymes allows: (1) to combine all advantages of the homogeneous catalysis with easy separation of enzyme molecules from the reaction mixture in the end of the process; (2) to increase significantly the thermostability of immobilized enzyme via its precipitation by pH decrease; (3) to protect the enzyme from high‐molecular‐weight inhibitors either in the precipitate or in a homogeneous solution; (4) to create self‐regulating enzyme systems in which an attainment of the certain conversion degree results in process termination; (5) to design reversibly soluble polyenzymatic systems.
Structure and superstructure in eutectoid copolymers
Authors: Kilian Hanns Georg 
Published: March 2011

AbstractSegregation of eutectic co‐units in eutectoid copolymers is behind of forming lamella‐shaped extended chain‐sequence crystals. These are as cooperative units inhomogeneous microphases (IMP). The mean thickness and the thickness distribution of the IMPs are uniquely related to the lengthdistribution of crystallizable sequences (c‐sequences): The primary elements of the colloid structure in eutectoid copolymers are therefore strictly determined by the chain structure. Clusters are formed comprising a finite number of nearly parallel IMPs alternated with amorphous layers. These clusters are the constitutive elements on the secondary level of the colloid‐structure. Hosemann's linear paracrystal is used for modelling the cluster structure and for describing X‐ray small‐angle pattern.
Kinetics of relaxation and unmixing in polymer blends as studied by x‐ray scattering
Authors: Strobl Gert 
Published: March 2011

AbstractConcentration fluctuations in polystyrene/poly(styrene‐co‐bromostyrene) blends and changes induced by temperature jumps were studied by small‐angle X‐ray scattering. Structure factors in thermal equilibrium show the form given by the random phase approximation. Kinetics of structure changes after T‐jumps within the homogeneous phase or jumps from the mixed state into the two‐phase region are in accordance with the predictions of latest theories, being described by a simple equation of motion. Application of the theory enables a determination of relaxation times dependent upon the wave vectors. At temperatures near to the glass transition, relaxation and growth become nonexponential.
New concepts in the physics and chemistry op solid polymers fracture
Authors: Zarkhin Lev S. , Manevitch Leonid I. , Enikolopian Nikolai S. 
Published: March 2011

AbstractElementary events in polymer fracture at the molecular level are the breakdowns of single polymeric chains. Breakdown of a stretched macromolecule is accompanied by its mechanical degradation. Comparison of experimental data on the molecular products of thermal and mechanical degradation points to significant distinctions between these two processes. Generation of highly excited (“hot”) molecular products of mechanical degradation by the growing crack cannot be explained in terms of the kinetic concept of polymer fracture. Elaborate theoretical analysis of polymeric chain breakdown and generation of “hot” molecular products in subpicosecond time range is made by numerical molecular dynamic simulation with a computer. The mechanisms of primary and secondary chain breakdowns are established. The principal initiators of breakdowns are localized nonlinear modes of the lattice soliton type. Generation of highly excited (“hot”) molecular products occurs at the initial stage of mechanical degradation (during≈1 picosecond after the first breakdown).
New aspects of the photo‐oxidation and photo‐stabilization of polymers
Authors: Geuskens Georges 
Published: March 2011

AbstractThe mechanism of the photo‐oxidation of an ethylene‐propylene random copolymer (EPM) has been compared with that of a styrene‐butadiene‐styrene block copolymer (SBS). The former is considered as a model for polyolefins that undergo chain scission on irradiation and the latter as a model for unsaturated rubbers that become cross‐linked. A hindered amine light stabilizer (HALS) that is a better inhibitor of the absorption of oxygen in SBS than in EPM is, however, less efficient to prevent formation of carbonyl groups and change of the mechanical properties. These results are discussed and an explanation is proposed.
Nature and relative contribution of luminescent species in the photodegradation of polyolefins
Authors: Kuroda Hideyuki , Osawa Zenjiro 
Published: March 2011

AbstractLuminescent species observed in the polyolefins were mainly foreign impurities, i.e., polynuclear aromatics (PNA) adsorbed from an ambient atmosphere. The luminescent species adsorbed under normal atmospheric conditions and an equivalent amount of PNA did not affect the photodegradation of high‐density polyethylene (HDPE). On the other hand, the extracted precipitates from HDPE accelerated the photodegradation of the polymer and, also, 3‐octanone slightly accelerated it, but little effect was observed in 1‐icosene. Therefore, the activity of impurities on the photodegradation of HDPE can be expressed in the following order:Extracted precipitates >> C=sO > PNA ∞ ‐CH=CH2
Macroscopic, microscopic and molecular aspects of fracture in polymers
Authors: Devries K. L. , Hornberger L. E. 
Published: March 2011

AbstractThe distribution of stress at macroscopic and molecular levels can dramatically affect mechanical properties. This paper explores both these aspects. In the first part, quenching operations for polycarbonate and polystyrene were shown to develop favorable residual stresses as well as structural alterations (as manifested by changes in density, hardness, DSC results, etc.). The changes in these glassy polymers can be accompanied by as much as an order of magnitude increase in impact strength and fatigue life. In the other phase of our study, various analytical methods were used to investigate phenomena associated with fracture in oriented semi‐crystalline polymers. In the studies reported here, the combined effects of stress and environmental agents on mechanical strength of nylon, polyethylene, and Kevlar fibers were measured. These results, in conjunction with investigations of bond rupture kinetics, suggest that fracture in these materials involve thermally activated chain scission in which the activation energy is aided by stress and the chemical environment. Different mechanisms appear to dominate fracture in spherulitic forms of chemically similar polymers.
Designing polymer additives to minimise loss
Authors: Billingham N. C. 
Published: March 2011

AbstractThe solubility of additives in polymers is shown to determine the state of the additive in a processed sample and the mechanisms by which it may be lost. The loss of additives is described in terms of a model which considers the effects of solubility, diffusion rate and volatility, and it is shown that the rate and mechanism of loss depends upon these quantities and upon the sample geometry. The effects of additive structure on loss mechanism and rate are discussed and the implications for additive design are reviewed.
Functional derivatives of sterically hindered amines. 1. Glycidyl compounds
Authors: Lustoň Jozef , Vašš František 
Published: March 2011

AbstractFour polymerizable glycidyl derivatives of sterically hindered amines were prepared from derivatives of 2, 2, 6, 6‐tetramethyl‐4‐hydroxypiperidine and 14, 16‐dioxo‐7, 15‐diazadispiro [5, 1, 5, 3] hexadecane. One of them is a stable nitroxyl derivative.
Physical model explaining the effect of physical ageing on dynamic mechanical and calorimetric properties of poly(methyl methacrylate)
Authors: Diaz‐Calleja R. , Perez J. , Gomez‐Ribelles J. L. , Ribes‐Greus A. 
Published: March 2011

AbstractUsing the theory of non‐elastic deformation based on a specific model for the mobility in amorphous polymers, an equation was obtained including the real and imaginary parts of the complex modulus and the heat capacity as a function of temperature and ageing time. Thus, the model is based on the calculation of time and temperature evolution of the population of “faults” (corresponding to an excess of enthalpy and entropy) in the structure. We employ the model with only one “characteristic” relaxation time obtained from a concept of hierarchical correlation. The parameters appearing in the equations for G* and cp are the same in each case and are obtained from classical experiments (mechanical spectroscopy, dilatometry, calorimetry, etc.), thus having a specific physical meaning. Dynamic loss tangent and specific heat of PMMA measured after different thermal histories involving isothermal ageing agrees quite well with the prediction of the model.
Thermal degradation of polyethylene
Authors: Piiroja Eduard , Lippmaa Helle 
Published: March 2011

AbstractThermal degradation of low‐density polyethylene (LDPE) in the temperature range from 450 to 525°C has been studied using a sieve‐bottom reactor with inert gas as heat‐transferring agent bubbled through the PE melt. Temperature dependence of the degradation rate was determined. Full degradation of LDPE into gaseous and wax‐like hydrocarbons (alkanes and 1‐alkenes) was achieved. Temperature rise and prolonging of the contact time increased the yield of the gaseous hydrocarbons and decreased the molecular weight of the wax‐like product.
Structural recovery of polymer glasses
Authors: Hutchinson J. M. , Ruddy M. 
Published: March 2011

AbstractThe structural recovery of polystyrene glasses subjected to thermal cycles in the glass transition region is studied by differential scanning calorimetry and by dilatometry. Three different types of behaviour are observed in respect of the peak in the specific heat capacity or thermal expansion coefficient on heating, and are found to be in full agreement with the predictions of the KAHR model. First, for well‐stabilized glasses, the dependence of the (main) peak temperature on heating rate and annealing time yields consistent values for the structure parameter x by means of the peak‐shift method. Second, for poorly‐stabilized glasses, the (upper) peak temperatures shift quite differently, but again consistently with theory. Third, for glasses intermediate between poorly‐and well‐stabilized conditions, both main and upper peaks can be observed simultaneously in the same endotherm.
High‐performance polyolefin composites by chemical modification
Authors: Rätzsch Manfred 
Published: March 2011

AbstractThe paper will give a short introducing survey on the present state of polyolefin and copolyolefin cross linking.The combination of high‐density polyethylene (PEHD) and polypropylene (PP) with elastomers, particularly with ethylene‐propylene terpolymer (EPDM), results in high‐impact strength PP (HI‐PP) and in thermoplastic elastomers (TPE) considered as high‐performance polyolefin composites (HP‐POC). By filling of PEHD and PP, HP‐POCs with increased stiffness, modulus, and abrasion resistance can be produced. They are cost ‐ advantageous substitutes for construction materials as, for example, ABS. Possibilities and limits are demonstrated by own investigations in this field.Best mechanical properties are obtained by reinforcement with fibres, particularly with glass fibres. Requirement for superior parameters is a chemical coupling between glass‐fibre surface or glass‐fibre size, respectively, and the PP matrix.A new adhesive agent on the basis of siloxane allows to reach high strength and toughness of the composites. The effect seems to be due to a better mutual penetration of the adhesive agent, the size, and the PP matrix. Outlooks will be given on the further development of HP‐POC in the field of reinforcement and reactive combination with other polymers.
Melting behaviour of gelspun/drawn polyolefins
Authors: Bastiaansen C. W. M. , Lemstra P. J. 
Published: March 2011

AbstractThe melting behaviour of gelspun/drawn UHMW‐PE and UHMW‐PP fibres was investigated. Unconstrained UHMW‐PE and UHMW‐PP fibres melt at 142°C and 170°C, respectively. Upon constraining, by holding the fibres at a fixed length or by embedding the fibres in a matrix, an increase in the melting temperature of both fibres is observed. In the case of UHMW‐PE fibres a solid‐solid phase transition in polyethylene at 155°C from the orthorombic to the hexagonal crystal structure occurs. Above 155°C, the fibres can not sustain any load. This solid‐solid phase transition at 155°C sets an upper limit to both the maximum curing and continuous use temperature of PE‐fibre reinforced composites. In gelspun/drawn UHMW‐PP, such a detrimental solid‐solid phase transition is absent, and therefore the increase in melting temperature can be utilized effectively. For example, heating of UHMW‐PP fibres for 30 minutes at 200°C does hardly affect the room temperature Young's modulus and tensile strength if the fibre is constrained during heating.
Radiation modification of semicrystalline polymers
Authors: Dobó J. 
Published: March 2011

AbstractThree problems of the radiation modification of polymers are dealt with. Different methods of grafting are compared with respect of the formation of true graft copolymer and homopolymer in the polyethylene‐styrene system; the prevention of the penetration of monomer by grafting polytetrafluoroethylene is shown; the mechanical properties of crosslinked ethylene polymers below and above the melting point are discussed.