bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chain‐cycle equilibrium in the course of the polycondensation of aldehydes with α,ω‐dithiols
Authors: Sensfuß Steffi 
Published: April 2003

AbstractThe course of the proton catalysed solution polycondensation of aromatic aldehydes and α,ω‐dithiols (C6–C8) has been investigated by the use of benzaldehyde/triethylene glycol dithiol or hexamethylene dithiol. Too long reaction periods lead to a polymer degradation under the conditions of synthesis. It is caused by a complex polymerization equilibrium between cyclic, oligomeric and polymeric mercaptals after removal of the reaction water. The chain propagation simultaneously proceeds via open‐chain and cyclic intermediates. The polymers may be transformed into cycles and vice versa. The chain‐cycle equilibrium preferably takes place in solvents like CH2CI2, CHCI3 or benzene, but hardly in dioxane or DMSO.Polymercaptals derived from aromatic dithiols (4,4′‐thiodibenzenethiol) and benzaldehyde analogously undergo chain scission under weakly acidic conditions (CH2CI2, reflux). However, in this case a mixture of linear and cyclic mercaptal structures is presumably formed.
Polystyrol und styrolcopolymere
Authors: Gausepohl Hermann , Warzelhan Volker 
Published: April 2003

AbstractPolystyrene is with a present day sales volume of 8,5 million tons a year one of the most important thermoplastics worldwide. Its unique property profile makes polystyrene an ideal material for housings, refrigerator inliners and demanding packaging applications, when transparency and/or surface quality as well as stiffness are important. Its economic success is due to its favourable price/performance ratio and also not least to its excellent processability as an amorphous material.In this contribution the versatility and potential for innovation of polystyrene and its copolymers are discussed. Using standard and impact modified polystyrene, it is shown how the maturity of the polymerisation process, the broad spectrum of product modifications as well as processing know how of this class of materials have helped to promote the breakthrough of this product to an acknowledged plastic material.Modern polystyrene variations are increasingly meeting the special property requirements of other materials, like for example high heat resistant PPE/PS‐I blends, weather resistant ASA and AES plastics, tough and crystal clear star polymers or hydrogenated and unhydrogenated elastomers.A special feature of polystyrene is that it is one of the few monomers which can be polymerised using all the known methods for vinyl monomers to produce high molecular weight products. Thus the newest polymerisation techniques using metallocene catalysed and anionic polymerisation methods lead to products with the property profile of engineering plastics.Polystyrene will continue to grow in the future and thus increase in importance, especially while it can be easily depolymerised and in the form of styrene monomer recycled.
Polyamide, polyester und polyoxymethylen. Die klassischen technischen kunststoffe und ihre perspektiven
Authors: Heym Manfred 
Published: April 2003

AbstractPolyamide, polyester and polyoxymethylene having presently a worldwide sales volume of 2,4 million tons a year are important engineering thermoplastics. Based on their special property profiles they are mainly used in the automotive and electronic industry for high performance functional parts. This contribution presents polymerisation processes, properties, and selected new developments for these polymer classes.Semiaromatic polyamides due to their dimensional stability and thermal resistance lend themselves to applications which were so far reserved for thermosets or metals. Glass fiber reinforce polyamides designed to have the highest possible heat ageing resistance can take important functions under the hood. A polyamide blend used as a material for exterior body parts is key to light weight cars with strongly reduced fuel consumption. Halogene free flame retardant polyamide increases fire safety and environmental safety in flame sensitive applications.Polybutyleneterephthalate as the technically most important polyester offers new perspectives in blends with amorphous polymers leading to lower distortion and better surface quality in glass fiber reinforced parts. Polybutylenenaphthalate is widening the range of application of polyesters towards higher temperatures. Copolyesters derived from polybutyleneterephthalate are biologically degradable and are therefore promising materials for fermentable foils.Polyoxymethylene copolymers show an outstanding combination of stiffness, dimensional stability, friction and wear as well as resistance against hot water and fuel.As a result of their excellent properties and the existing potential for further improvements polyamide, polyester and polyoxymethylene will continue to grow above average in the future.
Sind polyurethanwerkstoffe ein reifes gebiet?
Authors: Müller Peter 
Published: April 2003

AbstractThe world‐wide production of polyurethanes has exceeded 6 mio. metric tons in 1994. Compared with the produced amounts of large‐scale thermoplastics such as PE, PVC, PP and PS, polyurethanes keep the 5th place.Polyurethanes (PUR) are segmented polymers, which can be synthesized from preformed building blocks in a modular unit construction system. The chemical modules and the various possibilities of combination will be discussed here.Tailor‐made polyurethane materials can be divided into two main‐fields of application: foams and compact PUR.The main constituents of polyurethane materials are diisocyanates and polyols. These key‐ chemicals are well characterised with respect to their technological, economical and ecological properties. Taking into account the availability, the masses of production and the experiences that have been collected with the PUR main constituents, these PUR precursors seem to be very mature already.In contrast to this, the PUR‐materials made from these building blocks still offer numerous novel problem‐solutions, resulting from the variability of the diisocyanate‐poly‐addition reaction: PUR materials are most commonly segmented into several phases. The formation of hard‐ and softsegments can be easily demonstrated by looking at thermoplastic polyurethanes (TPU). A deeper understanding of this phase separation and the molecular organisation within these materials promises to realize prospectic polymeric architectures with new and improved properties. PUR materials will still be able to offer new answers to future requirements in balancing economical and ecological needs. By looking at the life‐cycles of soft and hard‐foams, polyurethane‐coatings and thermoplastic PUR‐elastomers, this contribution will adress the question: “Is PUR‐chemsitry still a challenging field?”
Polymethacrylate‐werk‐ und wirkstoffe mit breiter anwendung
Authors: Wunderlich Winfried 
Published: April 2003

AbstractThe industrial application of polymethacrylates includes plastic materials such as the classical PMMA for transparent sheets and moulded parts as well as functional polymers, which are widely used as processing aids or modifying agents. The adaption of their properties to specific needs of the market can easily be reached because of the broad variability of methacrylic chemistry. Improved and new properties result from tailor made structures on the molecular and supramolecular level. Products like macromonomers, polymeric tensides or thermoplastic elastomers are examples of this.The discovery of the compatibility of polymethacrylates with other polymers extend their application in blends and coextruded products. This was particularly supported by new developments in processing and extrusion technique. The progress in chemistry, physics and technology promotes a continuous growth of the polymethacrylates and their introduction into new uses. This is proved by examples from various applications.
Fire‐retardant action of potassium nitrate in polyamide 6
Authors: Levchik Sergei V. , Levchik Galina F. , Camino Giovanni , Costa Luigi , Lesnikovich Anatolii I. 
Published: April 2003

AbstractThe addition of 10–20 wt.‐% of potassium nitrate (KNO3) to polyamide 6 (PA 6) improves the fire retardance of the polymer. The thermal decomposition behaviour of the PA 6/KN03‐mixture was studied using thermogravimetry, differential scanning calorimetry and thermal volatilisation analysis. Solid products of the thermal decomposition of the mixture were analysed by infrared spectroscopy, X‐ray diffraction and electron paramagnetic resonance. It was found that KNO, prevents flowing and dripping of the melt and promotes charring on the surface of the polymer which decreases its fire hazard and improves its fire retardance. On the other hand, KNO3 exothermally reacts with PA 6 in the condensed phase and supplies oxygen to the gas phase which increases the combustibility of PA 6. The mechanism of the chemical interaction of KN03 with PA 6 is discussed.
Effect of tricalcium phosphate, hydroxyethyl methacrylate, and ethylene glycol dimethacrylate on the mechanical properties of acrylic bone cement
Authors: Yang Jen‐Ming , Lu Charng‐Shing , Hsu Ying‐Gev 
Published: April 2003

AbstractThe effects of the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) on the properties of standard surgical Simplex‐P radiopaque bone cement have been investigated. The fracture surface after tensile test was studied by scanning electron microscopy. The influence of these components on the temperature rise during polymerization was investigated. It was found that the tensile strength, the bending strength, and the compressive strength decreased with increasing TCP content, whereas the inverse was observed for the Young's modulus. The tensile strength slightly increased with increasing HEMA content and then it levelled off when the HEMA content was higher than 15 wt.‐%. It seemed that there were maximum tensile, bending and compressive strengths when 2 wt.‐% EGDMA (in HEMA) was added. Polymerization occurred more rapidly when HEMA and EGDMA were added, whereas the inverse result was found with TCP.
pH‐sensitivity of the swelling of a chitosan‐pectin polyelectrolyte complex
Authors: Yao Kang De , Tu Haili , Cheng Fa , Zhang Jing Wu , Liu Jing 
Published: April 2003

AbstractThis paper deals with a novel polyelectrolyte complex (PEC) of two natural polyelectrolyte ligands, i.e. chitosan (CS) and pectin (PTn). The composition and its effect on the swelling properties of this CS‐PTn PEC were studied. The results reveal that the swelling of the polyelectrolyte complex is connected with its composition and is also affected by the degree of deacetylation of CS and the methoxy degree of PTn.
The relative physical and thermal properties of polyurethane elastomers. Effect of chain extenders derived from dihydroxynaphthalene
Authors: Liaw Der‐Jang 
Published: April 2003

AbstractPolyurethane elastomers were synthesized based on polyols such as poly(caprolactonediol) and poly(tetramethylene glycol), diisocyanates such as diphenylmethane‐4,4′‐diisocyanate (MDI) and dicyclohexylmethane‐4,4′‐diisocyanate (HMDI), and two dihydroxynaphthalenes (DHNs) and their brominated derivatives used as chain extenders. The effects of the chemical structures of the chain extenders on the physical and thermal properties of the polyurethanes were investigated. Because of the higher degree of phase mixing of the 1,5‐DHN unit, the 1,5‐DHN‐based polyurethanes have higher Tg values and higher dynamic properties than 2,7‐DHN‐based polyurethanes. Introduction of bromine atoms increased the flame retardance. However, the large free volume of bromine atoms restricted the rotation of DHNs, thus, directly decreasing the degree of phase‐mixing and crystallinity of the polyurethanes. Introducing bromine atoms also decreased the mechanical and dynamic properties and increased the solubility of the polyurethanes.
Chemical stability of some poly(amide imide) type polymers
Authors: Hamciuc Elena , Hamciuc Corneliu , Airinei Anton , Bruma Maria 
Published: April 2003

AbstractThe stability of some heterocyclic poly(amide imide)s in acidic and alkaline medium was compared to the structurally related polyimide and poly(amide imide)s without other heterocyclic groups. All the polymers have high stability in acidic medium. The introduction of additional heterocycles such as 1,3,4‐0xadiazole or phenylquinoxaline into the macromolecular chain of a poly(amide imide) increases substantially the resistance to alkaline medium. Polyamides containing imide rings only in the side chain are more stable to hydrolysis than related polyamide having imide units in the main chain.
Analysis of the chemical composition of poly(ε‐caprolactam)‐block‐polybutadiene copolymers by photoacoustic FTIR spectroscopy and by FT Raman spectroscopy
Authors: Schmidt Pavel , Roda Jan , Nováková Václava , Pastor José M. 
Published: April 2003

AbstractThe chemical composition of poly(ε‐caprolactam)‐block‐polybutadiene copolymers (PCL‐PBD) was investigated by FT infrared spectroscopy with photoacoustic detection and by FT Raman spectroscopy. The derived calibrations were used for the estimation of content of butadiene units in the PCL‐PBD fractions soluble and insoluble in 2,2,2‐trifluoroethanol.
Synthesis and modification of a trifunctional epoxy resin with amino‐terminated poly(dimethylsiloxane)s for semiconductor encapsulation
Authors: Shieh Jeng‐Yueh , Ho Tsung‐Han , Wang Chun‐Shan 
Published: April 2003

AbstractA high‐performance trifunctional epoxy resin based on the triglycidyl ether of tris (4‐hydroxyphenyl)‐methane (TETM) was synthesized by the condensation of 4‐hydroxybenzaldehyde with phenol followed by epoxidation with epichlorohydrin. The structure of TETM was confirmed by mass spectra, infrared and nuclear magnetic resonance spectroscopy. Amino‐terminated poly(dimethylsiloxane)s were used to reduce the stress of the trifunctional epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The dispersed silicone rubbers effectively reduce the stress of cured epoxy resins by reducing the coefficient of thermal expansion and flexural modulus while the glass transition temperature was hardly depressed.
Zur Kinetik der stabilisierten Fällungs‐polymerisation eines Kationischen Monomeren in wäßrigen Natriumchlorid‐Lösungen
Authors: Hildebrandt Volker , Reichert Karl‐Heinz 
Published: April 2003

AbstractDie Kinetik der stabilisierten Fällungspolymerisation des kationischen Monomeren N‐(2‐Methacryloyloxyethyl)‐N,N‐dimethylbenzylammoniumchlorid (MADAMBQ) in wäßrigen Natriumchlorid‐Lösungen wurde mittels Reaktionskalorimetrie untersucht. Polyethylenoxid höherer Molmasse wurde als Stabilisator eingesetzt. Die Reaktionsgeschwindigkeit ist über einen größeren Umsatzbereich nahezu konstant und fällt anschließend mit dem Umsatz annähernd linear ab. Die Teilchengrößenverteilung der gebildeten Dispersion ist bimodal mit Teilchen von etwa 1 bis 30 μm Durchmesser.Zur Beschreibung des Geschwindigkeitsverlaufs der Fällungspolymerisation wird ein Modell vorgeschlagen, das die Polymerisation in der Wasser‐ sowie in der Polymerphase berücksichtigt. Die Teilchenbildung soll durch homogene Nukleierung erfolgen. Es wird angenommen, daß die Konzentration des Monomeren in den Phasen durch ein Nernstsches Verteilungsgleichgewicht bestimmt wird. Zu Vergleichszwecken wurde auch die Polymerisation von MADAMBQ in Lösung und als nicht stabilisierte Fällungspolymerisation durchgeführt.
Starpolymers by soft‐hard‐soft block copolymers
Authors: Kéki S. , Bogács C. , Bogács L. , Daróczi L. , Zsuga M. 
Published: April 2003

AbstractA novel synthesis of starpolymers from a soft‐hard‐soft triblock has been reported. The triblock was obtained by adding isobutene (IB) “in situ” to the living styrene (S) polymerization mixture initiated by the p‐dicumylchloride/TiCl4/pyridine system. Microphase separation was observed by transmission electron microscopy and differential scanning calorimetry. Treatment of the PIB‐PS‐PIB triblock with CCI4 in the presence of AICI3 led to the starpolymer and the number of arms was estimated by size‐exclusion chromatography to be 20.
Specialty polymeric membranes, 7. Pervaporation separation of benzene/cyclohexane mixtures with nylon 6‐graft‐poly(oxyethylene) membranes
Authors: Yoshikawa Masakazu , Takeuchi Susumu , Kitao Toshio 
Published: April 2003

AbstractNovel membrane materials for pervaporation separation of benzene/cyclohexane mixtures were prepared by the introduction of oligo(oxyethylene)s, such as diethylene glycol, poly(ethylene glycol) 200 (PEG200) and poly(ethylene glycol) 400 (PEG400) onto Nylon 6. The polymeric membranes from modified Nylon 6 thus prepared showed permselectivity toward benzene. Some membranes exclusively permeated benzene from benzene/cyclohexane mixture.
Water‐swellable rubbers containing powdery poly(acrylamide) hydrogel
Authors: Hron Petr , Vymazalova Zdenka , Lopour Petr 
Published: April 2003

AbstractHydrophilic composite materials were prepared by combining powdery poly(acrylamide) hydrogel with various technical rubbers (natural rubber, chlorobutyl rubber, EPDM rubber). The dependence of the quality of the dispersions of powdery hydrogel in rubbers on the method of dispersion was studied and properties (swelling capacity in water, mechanical characteristics) of the composites were measured. The natural rubber/hydrogel composites showed the best swellability (>80 vol.‐%). The mechanical properties of the composites are comparable to those of the unmodified rubbers, both in the dry and water‐swollen state.
Allylic polymers from resin acids
Authors: Bicu Ioan , Mustaţǎ Fǎnicǎ 
Published: April 2003

AbstractAn unsaturated adduct has been synthesized by the Diels‐Alder reaction between resin acids and diallyl maleate. The obtained polymerizable product can be used both as monomer in the formation of allyl polymers and crosslinking agent. The monomer and its polymers were investigated by usual physical and chemical methods. The synthesized polymers present a linear structure, possibly associated with intramolecular cyclization at low molecular weights, or a three‐dimensional structure at high conversions. They are fairly thermostable substances with carboxylic groups in the polymer chain.
Toughened thermosetting bismaleimides: Molecular structure, morphology and mechanical properties
Authors: Abbate M. , Martuscelli E. , Musto P. , Ragosta G. 
Published: April 2003

AbstractA 4,4′‐bis(maleimido)diphenylmethane resin was modified by adding a thermoplastic poly(ether imide) commercially available as Ultem 1000. A second system investigated was formed by a Kerimid resin and a maleimido‐terminated butadiene‐acrylonitrile copolymer (ITBN). For this system the kinetics of the curing process of the blend matrix with and without the rubber modifier was investigated at different temperatures by FTIR spectroscopy.A marked increase of the toughness parameters Kc and Gc was found for both the investigated systems. However, morphological analysis showed a complete phase separation and a complex morphology for the thermoplastic modified resin, while a homogeneous, single‐phase system was obtained after rubber modification by ITBN.
Radical polymerization of poly(butyl acrylate) in the presence of poly(L‐lactic acid), 1. Synthesis, characterization and properties of blends
Authors: Avella Maurizio , Errico Maria Emanuela , Immirzi Barbara , Malinconico Mario , Martuscelli Ezio , Paolillo Livio , Falcigno Lucia 
Published: April 2003

AbstractPoly(L‐lactic acid) is a biocompatible polyester, semicrystalline, thermoplastic, with low versatility in mechanical properties. To overcome this problem, a reactive blending procedure was performed by grafting an acrylic rubber, n‐butyl acrylate, via water suspension polymerization onto poly(L‐lactic acid) dissolved in an organic solvent. It was possible to isolate the copolymeric phase formed from the two polymers and characterize it by using NMR and DSC techniques. Mechanical tests on blends gave no satisfactory response, probably because the rubbery phase is composed essentially of viscous linear macromolecules, not able to perform elastic properties. Work is in progress to modify the synthetic pathway to incorporate diacrylates in order to realize a rubbery phase at least partially cross‐linked.
Products of the reaction of 4,4′‐bis(mercaptomethyl)benzophenone with halogenalkane acids and halogenalkane diols as new monomers
Authors: Podkościelny Wawrzyniec , Kultys Anna 
Published: April 2003

AbstractA few new thiodicarboxylic acids and thiodiols were obtained by condensation reaction of 4,4′‐bis(mercaptomethyl)benzophenone (BMMB) with some halogen acids or halogen alcohols, respectively, in aqueous sodium hydroxide solution.By melt polycondensation of one of these acids, i.e. benzophenone‐4,4′‐bis‐(methylthioacetic acid) (BBMTAA) with 1,5‐pentanediol, a new linear polyester was obtained, and by melt polyaddition of one of these diols, i. e. benzophenone‐4,4′‐bis(methylthiohexanol) (BBMTH) with hexamethylene diisocyanate (HDI) a new linear polyurethane was obtained.The structures of monomers and polymers were confirmed by elemental analysis and FT‐IR and 1H NMR spectroscopy. The polymers were studied to describe their physicochemical, thermal and mechanical properties.
Tin‐coupled styrene‐butadiene rubbers (SBRs). Relationship between coupling type and properties
Authors: Quiteria Valentín Ruiz‐Santa , Sierra Carmen A. , Gómez‐Fatou Jose M. , Galán Carmen , Fraga Luisa M. 
Published: April 2003

AbstractFollowing the development of new SBRs for tyre applications, several kinds of tin‐polymer bonds (styryl‐, butadienyl‐, isoprenyl‐ and α‐methylstyryltin) have been studied, in both branched and linear chains.Dynamic‐mechanical properties of the carbon black vulcanizates have been analyzed to establish a relationship between structural parameters of polymers and compound properties. The filler‐polymer interaction parameter, defined by a ratio of mechanical and dynamic terms, has been used for the evaluation of the compounds. The introduction of different types of tin‐polymer bonds, in branched and linear chains of the SBRs, implies an improvement in the hysteresis properties of the vulcanizates as well as a modification of the interaction parameter.
A novel spin‐finishing method for antistatic modification of polyester fiber. Surface reaction onto amine‐containing copoly(amide‐ethers) blended with polyester fiber
Authors: Sano Yoshiyuki , Lee Chan Woo , Kimura Yoshiharu , Saegusa Takeo 
Published: April 2003

AbstractCopoly(amide‐ethers) containing two types of tertiary amine units were made as antistatic modifiers for poly(ethylene terephthalate) (PET) fibers. The filaments of the copolymers were melt‐spun and reacted with three alkylating agents in order to quaternize the tertiary amine into a sulfo‐betaine, a carbobetaine, and an ammonium ion. The apparent electric resistivity of the filaments was greatly reduced by this reaction, being in the range of 106 to 108 Ω/cm. However, because these quaternized copolymers incurred decomposition during blend spinning with PET, a blend PET fiber containing one type of copoly(amide‐ether) was melt‐spun and subjected to quaternization of the amino groups as well as to surface crosslinking with various alkylating and epoxy agents. The quaternized blend fibers obtained showed improved antistatic properties compared with the original blend fiber. Particularly, the fibers crosslinked with epoxy compounds were found to have the best antistatic properties that had ever been attained with this type of modification. The antistatic properties were retained even after dyeing, because both hydrophilic and ionic groups had been effectively immobilized on the surface. Since this quaternization and crosslinking could be conducted on‐line with spinning and drawing within a short reaction time, this modification technique is called “spin‐finishing method”, which should be superior to the conventional methods in terms of cost performance and productivity.