bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the effect of stereoregularity and chain branching on thermal properties of multiple steam sterilized poly(vinyl chloride)
Authors: Jayabalan M. , Sreenivasan K. , Nair P. D. , George B. K.
Published: April 2003

Multiple steam sterilization drastically affects the micromorphology of poly(vinyl chloride) (PVC). Stereoregularity as well as chain branching of sterilized PVC samples varies in covered and uncovered samples. Attenuated total reflectance (ATR) spectral studies confirm these variations which are exhibited by the peaks at 1428 cm−1 and 1434 cm−1 for stereoregularity and by the peak at 1378 cm−1 for chain branching.

Differential scanning calorimetry (DSC) studies of sterilized samples indicate that the changes in the glass transition temperature (Tg) are not linear with the changes in syndiotacticity. Variation in the length of chain branches have a predominant effect over the variations in syndiotacticity: short chain branches and long chain branches offer higher and lower Tg, respectively, though the degree of syndiotacticity is the same in both cases.
Synthese von wachsartigen polyethylenen durch reaktion von ethylen mit aluminiumalkylen unter hochdruck
Authors: Grünig Heinz , Luft Gerhard
Published: April 2003

Für die Synthese von Polywachsen wie auch im Hinblick auf den Einsatz von Aluminiumalkylen bei der Hochdruckpolymerisation von Ethylen mit Ziegler‐Katalysatoren wurde die Reaktion von Ethylen mit Trihexylaluminium, Trioctylaluminium und Tetraisobutylaluminoxan unter Drücken von 500 bis 1250 bar und Temperaturen von 160 bis 230°C untersucht. In diskontinuierlichen Versuchen wurde der Einfluß von Druck und Temperatur auf die Produktverteilung sowie die Ausbeute gemessen. Es wurde festgestellt, daß hoher Druck und niedrige Temperature die Bildung längerkettiger Oligomerer begünstigt. Ausbeute und Reaktionsgeschwindigkeit nehmen mit steigender Temperatur, Ethylen‐ und Aluminiumalkylkonzentration zu. Die Hochdrucksynthese kann ohne Lösungsmittel durchgeführt werden.
Kristallisation, umkristallisation und schmelzen der β‐modifikation des polypropylens
Authors: Varga József , Garzó Gábor , Ille Attila
Published: April 2003

Die β‐Modifikation eines auf spezielle Weise pigmentierten und stabilisierten Polypropylen‐Typs wurde durch einen nicht isotherm geführten Kristallisationsprozeß in reiner Form dargestellt. Das Schmelzverhalten der β‐Modifikation ist stark von der thermischen Vorgeschichte — vor allem von der Rückkühltemperatur — abhängig (Memoryeffekt). Der Schmelzvorgang von Proben, die bis unterhalb eines kritischen Temperaturwertes (T) zurückgekühlt werden, wird von einer βα‐Umkristallisierung überlappt, wobei die Stärke der Überlappung von der während der Kristallisierung angewandten Kühlgeschwindigkeit, von der Schmelzgeschwindigkeit und von der Temperatur des Rückkühlens abhängt. An Proben, die bei der anisothermen Kristallisation bis zu einem Temperaturwert von TR ≥ 383 K zurückgekühlt werden, tritt keine βα‐Umkristallisierung auf, die β‐Modifikation schmilzt für sich allein. Während des Schmelzvorganges der β‐Modifikation kann eine innerhalb der β‐Modifikation ablaufende Umkristallisierung beobachtet werden. Das Temperaturintervall der βα‐und der ββ‐Umkristallisierung ist von den Versuchsbedingungen abhängig, so daß einmal der eine oder andere Prozeß überwiegt. In gewissen Fällen treten beide Umkristallisierungsvorgänge im Verlauf des Schmelzvorganges auf.
Untersuchungen zur massepolymerisation von vinylchlorid mit dem initiatorsystem tri‐n‐butylbor/sauerstoff bei −15°C
Authors: Braun D. , Bezdadea E. , Dethloff M.
Published: April 2003

Das Initiatorsystem Tri‐n‐butylbor/Sauerstoff (TNBB/O2) wurde zur Massepolymerisation von Vinylchorid bei ‐15°C verwendet. Der Einfluß der Tri‐n‐butylbor‐Konzentration, des Molverhältnisses von Tri‐n‐butylbor zu Sauerstoff und der Reaktionszeit auf den Umsatz, die Grenzviskosität ([η]) und die Molekulargewichte (M̄n, M̄w) wurde ermittelt. Die Struktur der hergestellten PVC‐Proben wurde in bezug auf Defektstellen und Taktizität mittels 1H‐NMR‐Spektroskopie untersucht und die thermische Stabilität für alle PVC‐Proben bestimmt. Anhand dieser Untersuchungen wird ein Initiierungsmechanismus für die Polymerisation vorgeschlagen, die vor ailem durch Butylradikale gestartet wird.
Grafting onto preformed networks using thermolabile azo functions, I. Synthesis and characterization
Authors: Nuyken Oskar , Dyckerhoff Lutz , Kerber Robert
Published: April 2003

The terpolymerization of the three monomers (3‐vinyl phenylazo)methylmalodinitrile (1), (3‐vinyl phenylazo)phenylsulfid (2) or 1‐(3‐vinylphenylazo)‐1,1′‐diphenyl methylacetate (3) with methyl methacrylate and butanediol‐1,4‐dimethyacrylate leads to networks in which the thermolabile azo groups remain intact. Both, the azo monomer and the crosslinking agent are essentially quantitatively incorporated into the network before the conversion of the third monomer is complete. The networks have been characterized in terms of their swelling in benzene, chlorobenzene, and methacrylonitrile.
Grafting onto preformed networks using thermolabile azo functions, II. The grafting reaction
Authors: Nuyken Oskar , Dyckerhoff Lutz , Kerber Robert
Published: April 2003

In order to graft methacrylonitrile onto preformed networks containing thermolabile azo groups, the monomer was used to swell the networks and then the temperature raised to the decomposition temperature for the azo groups. The unusually high grafting efficiencies yields (ε) achieved are explained in terms of both the differences in the reactivities of the primary radicals formed and side reactions, which lead to additional grafting sites. As an aid to understand the dependence of monomer conversion on that of the initiator a kinetic model is discussed, which involves the consideration of the polymerization taking place both in the homogeneous phase and within the polymer pearls, which can be treated as isolated reactors.
The dynamic mechanical behaviour of blends of polyphenylene sulfide with acetylene terminated sulfone
Authors: Zeng Hanmin , He Guoren , Yang Guicheng
Published: April 2003

The dynamic mechanical behaviour of blends of poly(phenylene sulfide) (PPS) with the acetylene terminated sulfone bis(4‐(4‐ethynylphenoxy)phenyl)sulfone (ESF) was investigated by torsional braid analysis (TBA). A uniform dispersed system of ESF/PPS may be obtained by a solution process at 200°C, and can be maintained during the heat treatment up to 400°C. The increase of Tg of the blended system was found to be inappreciable by one‐step and short time (e.g. 1 h) heat treatment, whatever the ESF fraction is. By a long term heat treatment or by step‐curing, the Tg of the system may be raised from 180 to 220°C, in company with the increase of rigidity at 300°C, compared with pure PPS. The flexural modulus and interlaminar shear strength of continuous unidirectional carbon fibre composites with a blended matrix of ESF/PPS = 10/90 are significantly higher than those of composites with pure PPS matrix.
Polymerization of lactams, 82. Cationic copolymerization of 6‐caprolactam with 12‐dodecanelactam
Authors: Gomola Rudolf , Kondelíková Jaroslava , Králíček Jaroslav
Published: April 2003

The cationic copolymerization of 6‐caprolactam with 12‐dodecanelactam initiated by a compound of anhydrous phosphoric acid with 6‐caprolactam was studied at 260°C and various initial ratios of comonomers. The copolymerization rate decreased with increasing content of 12‐dodecanelactam in the initial mixture. The early phase of copolymerization was characterized by an increased amount of formed oligomers, which was probably supported by the presence of 12‐dodecanelactam. On the other hand, 6‐caprolactam suppresses the reactivity of 12‐dodecanelactam in copolymerization.
Durability of radiation sterilized polymers, V. Depression of molecular weight and melting point by oxidation
Authors: Yoshii Fumio , Makuuchi Keizo , Ishigaki Isao
Published: April 2003

Molecular weight and melting point of polypropylene degraded by irradiation sterilization were measured. The sterilization of polypropylene with a dose of 2.5 Mrad reduces its molecular weight by one third. The decrease in molecular weight of the polypropylene irradiated in vacuum was far smaller than that for samples irradiated in air. The melting point was shifted to lower temperatures with increasing dose. This corresponds well to the decrease in molecular weight. For irradiated copolypropylene, a new peak appeared in the differential scanning calorimetry diagram at a lower temperature and its intensity increased with the dose. Copolypropylene, the crystallinity of which is lower than that of homopolypropylene, was more stable in the mechanical properties compared to irradiated homopolypropylene. However, scission by irradiation occurred in copolypropylene as well as in homopolypropylene. Thus, it was concluded that the ratio of amorphous and crystalline parts in the polymer has an important influence on mechanical properties of irradiated polypropylene.
Fe2+‐thioureadioxide‐H2O2 induced polymerization of various vinyl monomers with flax fibres
Authors: Abou‐Zeid N. Y. , Waly A. , Higazy A. , Hebeish A.
Published: April 2003

Fe2+‐thioureadioxide‐H2O2‐redox system induced polymerization of various vinyl monomers with flax, alkali‐treated flax, and partially carboxymethylated flax was investigated. Monomers used included glycidyl methacrylate (GMA), methyl methacrylate (MMA), 2‐hydroxy ethylmethacrylate (2‐HEMA), and acrylonitrile (AN). The polymerization reaction was carried out under a wide range of conditions including temperature (50–90°C), H2O2 concentration (0.01–1%), monomer concentration (20–200%, based on sample weight), and time (5–120 min). Results obtained led to the following conclusions:

Raising the polymerization temperature from 50 to 60°C increases the percent polymer add‐on while the latter decreases by further increase in temperature, irrespective of the substrate and monomer used. The percent polymer add‐on increases by increasing monomer concentration from 20 to 200% and by increasing H2O2 concentration up to 0.1%, then decreases upon using higher H2O2 concentrations due to faster rate of termination. For a given polymerization condition, the percent polymer add‐on follows the order partially carboxymethylated flax > alkali treated flax > flax. Monomer reactivity follows the order: GMA > 2‐HEMA > MMA > AN.

Poly(GMA)‐containing flax retains its free epoxy rings practically intact, provided that the add‐on is low (ca. 10%). Involvement of these functional groups in reactions with the functional groups of flax occurs at higher percent add‐on (ca. 50–100%).
Thermal and photodegradation of vinyl chloride/vinyl bromide copolymers
Authors: Braun Dietrich , Böhringer Bertram , Iván Béla , Móri Erzsébet , Kelen Tibor , Tüdős Ferenc
Published: April 2003

Vinyl chloride/vinyl bromide (VC/VBr) copolymers have been synthesized by radical copolymerization in bulk. Conversion increases and molecular weight of the copolymers decreases with increasing VBr in the feed. This indicates that VBr is a chain transfer agent in VC/VBr copolymerization systems. In accordance with the lower thermal stability of the vinylbromide homopolymer (PVBr), thermal degradation experiments show that the stability of the copolymers significantly decreases with increasing VBr content. It has been found that the initial rate of dehydrohalogenation is an exponential function of VBr content during thermal degradation of VC/VBr copolymers. In separate experiments, HBr evolved during degradation has been determined by a bromide selective electrode. The initial dehydrobromination rates of VC/VBr copolymers containing higher fractions of VBr are markedly higher than the initial dehydrochlorination rates. This clearly indicates the lower thermal stability of VBr monomer units compared with VC units. UV and visible spectra of degraded VC/VBr copolymers show that the absorption and the average length of polyenes are higher for samples with higher VBr content.

Dehydrohalogenation curves obtained during photodegradation of VC/VBr copolymers show a faster initial phase followed by a slower stationary phase. The initial rate of dehydrohalogenation is higher for copolymers containing higher fractions of VBr, whereas these copolymers reach the slower stationary phases at lower extents of dehydrohalogenation.
Study of phenolic copolymer/nonionic polymer interactions and formation of interpolymer complexes
Authors: Chatterjee S. K. , Yadav D.
Published: April 2003

Interpolymer complex formation between poly(vinyl pyrrolidone) (PVP) and poly(ethylene oxide) (PEO) with a phenolic copolymer has been studied by several methods, e. g. viscometry, potentiometry, conductometry, and IR spectra. Formation of interpolymer complexes of definite stoichiometries were observed by these methods. Interactions between the component polymers have been explained in terms of their structure and the stoichiometries of the complexes have been correlated with the composition of the phenolic copolymer.
Polymer blends, 3. Preparation and evaluation of the blends of shellac with polyamideimide from rosin
Authors: Kundu Achintya K. , Ray Sabyasachi Sinha , Mukherjea Ram N. , Maiti Sukumar
Published: April 2003

Polymer blends were prepared from shellac and polyamideimide. The polyamideimide was synthesized by reacting rosin maleic anhydride Diels‐Alder adduct with 4,4′‐diamino diphenylmethane. The compatibility of these blends was studied by solubility parameter, heat of mixing data, solution viscosity, and differential scanning calorimetry. It was found that the composition of 40 : 60, shellac : polyamideimide produces a compatible blend. The thermal behaviour of the blends was investigated.
Water‐soluble copolymers, XXIII. Copolymers of acrylamide with N‐(1,1‐dimethyl‐3‐oxobutyl)‐N‐(n‐propyl)acrylamide: Synthesis and characterization
Authors: McCormick C. L. , Blackmon K. P.
Published: April 2003

The copolymerization of acrylamide (AM) with N‐(1,1‐dimethyl‐3‐oxobutyl)‐N‐(n‐propyl)acrylamide (PDAAM) has been studied in the range from 5 to 20% PDAAM in the feed. The copolymer compositions have been determined from elemental analysis and 13C‐NMR. Reactivity ratio studies have been performed and the value of r1 r2 determined to be 2.20. The molecular weights of the copolymers were found to decrease with increasing PDAAM content in the feed. The copolymer microstructures were predicted from the experimentally determined reactivity ratios. These model structures are utilized for assessment of structure/dilute solution property relationships reported in a subsequent paper in this series.
Water‐soluble copolymers, XXIV. Copolymers of acrylamide with N‐(1,1‐dimethyl‐3‐oxobutyl)‐N‐(n‐propyl)acrylamide: Solution properties
Authors: McCormick C. L. , Blackmon K. P. , Elliott D. L.
Published: April 2003

Solution properties of copolymers of acrylamide (AM) with N‐(1,1‐dimethyl‐3‐oxobutyl)‐N‐(n‐propyl)acrylamide (PDAAM) of known molecular weight have been studied as a function of composition, added electrolytes, and polymer concentration. Arrhenius‐type studies have been performed by viscometry and NMR to assess the effects of temperature. Phase separation studies have also been performed using turbidimetry. The solution properties of the AM‐PDAAM copolymers are dictated by the presence of intramolecular hydrophobic interactions. These interactions may result in decreased hydrodynamic dimensions relative to polyacrylamide of similar molecular weight.
Sorption and diffusion of dibasic acid dyes in nylon 6
Authors: Praptowidodo Veronica S. , Hamada Kunihiro , Iijima Toshiro
Published: April 2003

Sorption and diffusion of dibasic acid dyes in Nylon 6 films were investigated at 333, 343, and 353 K. The results obtained are successfully explained by means of a bimodal mechanism consisting of partition and ion‐exchange. The concentration dependence of the diffusion coefficient was interpreted using this model. The temperature dependence of the characteristic values of the partition coefficient and the equilibrium constant of ion exchange are discussed.
Effect of γ‐irradiation on the electrical properties of cellulose nitrate
Authors: Amin M. , Mounir M. , Darwish K. A.
Published: April 2003

Two types of cellulose nitrate were studied; the red cellulose nitrate LR‐115 type 2 and the light pink CA 80–15 samples (Kodak, France). The samples were exposed to different doses of γ‐rays from a 60Co‐source (from 0.1 – 0.3 Mrad) at room temperature. Conductivity and dielectric constant measurements were carried out. For both nitrate samples (CA 80–15, LR‐115), the electrical conductivities are high in comparison with the unirradiated ones for a dose of 0.1 Mrad, but there is a slight change between 0.1 and 0.2 Mrad doses for CA 80–15 samples while the electrical conductivity is found to be less for 0.3 Mrad due to the damage in the plastic network. Also for the samples LR‐115 the electrical conductivity is lower for doses of 0.2, 0.3 Mrad than that for 0.1 Mrad dose. We notice that the glass transition temperature (Tg) of cellulose nitrate is clearly affected by γ‐irradiation as judged from the anomalies in σ(T) for the two samples which contain different amounts of the pigment. Irradiation of LR‐115 samples resulted in a higher dielectric constant for 0.1 Mrad dose and a lower one for 0.2, 0.3 Mrad doses, but still higher relative to the fresh sample. The dielectric constant of irradiated CA 80–15 samples (0.1, 0.2 Mrad) is found to be high relative to the fresh sample, but for 0.3 Mrad dose the dielectric constant is lower than that of the fresh one.
Immobilization of trypsin on poly(alginic acid‐g‐glycidyl methacrylate‐co‐hydroxy ethyl methacrylate)
Authors: Reddy C. Raghuram , George Anne , Reddy C. Rami
Published: April 2003

To synthesize a matrix for the immobilization of enzymes, alginic acid, a naturally occurring polysaccharide has been chosen as the backbone, and glycidyl methacrylate (GMA) and 2‐hydroxy ethyl methacrylate (HEMA) as monomers for graft copolymerization. HEMA was used to introduce hydrophilic character which would have been lost during the introduction of the hydrophobic monomer glycidyl methacrylate into alginic acid. Immobilization of trypsin onto this matrix takes place by covalent bonding. The temperature optimum of the immobilized enzyme was found to be 35°C and it was most stable at pH 8.
The diels‐alder reaction and copolymerization of halogenated N‐phenylmaleimides with dienes
Authors: Lokaj Jan , Pivcová Hana , Hrabák František
Published: April 2003

The course of the Diels‐Alder reaction of N‐(2,4,6‐tri‐bromophenyl)maleimide (I) with 2‐methyl‐1,3‐butadiene (Ip) and of N‐(2,4,6‐trichlorophenyl)maleimide (II) with Ip, 2‐chloro‐1,3‐butadiene (Cp), and butadiene (Bt) in CHCl3 was investigated. For the I‐Ip addition, the reaction order was determined with respect to both components, and the activation energy was calculated. The Diels‐Alder adducts thus obtained were characterized by elementary analysis, by 1H‐ and 13C‐NMR spectra, specific volume contractions, melting points, solubilities, and polymerization abilities. Copolymers of I and II with Ip, Cp, Bt, and 2‐methylpropene (Ib) were prepared, and their composition was determined. The copolymerization and Diels‐Alder addition of I‐Ip and II‐Ip occurring in parallel were investigated, and the participation of these two processes in the total reaction was discussed.
Polymerization characteristics of a dye of anthraquinone
Authors: Hrabák František , Lokaj Jan , Tkaczyk Martin , Morozova Elena , Eliseeva Valentina , Chuiko Leonid , Voloshin Gennadii
Published: April 2003

A technical dye of the anthraquinone type was analyzed by GPC, mass spectroscopy, and elemental analysis. Along with the polymerizable component, N‐[4‐amino‐3‐methoxyanthraquinonyl‐(1)] methacrylamide (I), it contained a saturated admixture, N‐[4‐amino‐3‐methoxyanthraquinonyl‐(1)]‐2‐chloro‐2‐methylpropionamide (II). The homopolymerization of I was carried out, and admixture II was isolated and characterized. The copolymerization of the dye with styrene and methyl methacrylate was verified, and the retardation effect of II on the polymerization of these monomers was evaluated.
On the inclusion copolymerization of some vinyl and diene monomers in different types of matrices
Authors: Schneider Ch. , Greve H. H. , Bohlmann H. P. , Rehbold B.
Published: April 2003

The inclusion copolymerization of various vinyl monomer systems was studied in a thiourea and perhydrotriphenylene matrix while that of a disubstituted butadiene system was investigated in canals of thiourea, perhydrotriphenylene, deoxycholic acid and β‐cyclodextrine. The results were compared with those obtained for the corresponding free copolymerization especially with regard to copolymer composition. In all vinyl monomer systems inclusion copolymerization leads to the same copolymer composition as is found in the free process. On the other hand, in case of the diene system, the copolymer composition of the inclusion products is remarkably different from that of the copolymers formed by the free reaction; the former is always nearly ideal statistic independent of the nature of the host. Inclusion homopolymerization can successfully be carried out with monomers where the free radical polymerization is prevented by allylic inhibition.
Alternierende copolymere über komplexierte monomere
Authors: Eisenbach C. D. , Bülow U. , Daum U. , Fürderer B. , Schmidt F. G. , Fischer H. , Ulmschneider D.
Published: April 2003

Die unter präparativen Aspekten wichtigste Erkenntnis der Untersu‐chungen ist, daß die Copolymerisation ürber komplexierte Monomere iiber den gesamten Verlauf kontrolliert werden kann, und nicht– wie in der Literatur beschrieben – spontan einsetzt; von grundsltzlich‐ er Bedeutung ist der totale Ausschluß van Oxidationsmitteln (Sauer‐stoff, organische Peroxide) im System bevor die Polymerisation ge‐startet wird. Die Polyreaktion weist viele Merkmale der klassischen, nach einem Radikalkettenmechanismus ablaufenden Polymerisation auf, und sowohl Umsatz als auch Molgewichte köronnen durch entsprechende Wahl der Reaktionskomponenten und –bedingungen iiber einen weiten Bereich kontrolliert werden; zu einem umfassenden Verständnis der Elementarschritte der Polyreaktion sind jedoch noch weitere Unter‐suchungen erforderlich. Was die Eigenschaften der alternierenden Co‐polymeren anbelangt, so hat die Charakterisierung der synthetisier‐ten Polymeren gezeigt, daß das Eigenschaftsprofil deutlich von dem statistischer Copolymerer abweicht.Die Autoren danken dem Bundesministerium für Forschung und Technologie für diefinanzielle UnterstCitzung dieser Arbeiten. Den Herren Prof. Dr. H. Cherdron und Dr. L.L. Boöhm danken wir fürr wertvolle Hinweise und Diskussionen.
Giessfolien mit kristallinen TCNQ‐radikalionensalzen: Ein neuer weg zur erhöhung der elektrischen leitfähigkeit
Authors: Hocker Jürgen , Jonas Friedrich , Müller Hans‐Klaus
Published: April 2003

The electrical conductivity of conventional polymers like, for example, polycarbonate can be increased many magnitudes by adding suitable radical ion salts based on tetracyanoquinodimethane. The formation of suitable crystal structures like dendrites, fibrous crystals and whiskers plays a vital rôle in this: the crystalline precipitation must form a three‐dimensional network throughout the entire polymer matrix, and can only be produced by crystallization from solution. Given an ideal distribution of crystals in the films, additions of approx. 0.5 % by weight will give conductivities of up to 10−3 S/cm. Unlike conventional anti‐static agents (hydrophilizing agents), crystalline radical ion salts give films electrically conductive properties which are practically independent of atmospheric humidity. The films behave like electrical semiconductors and have a positive temperature gradient. In view of the small amount of additive required, these modified polycarbonate films can be used as transparent packaging films whose anti‐static properties are unaffected by atmospheric moisture.
The construction of new proteins
Authors: Mutter Manfred , Altmann Karl‐Heinz
Published: April 2003

Recent progresses in the elucidation of the folding mechanism and topology of proteins revealed that the formation of folding units with specific topological features is not restricted to a unique primary sequence. This finding presents the basis for the design of polypeptides having the propensity to fold into a tertiary structure that can be achieved by the assembly of peptide blocks exhibiting stable secondary structures. Conformational studies on model peptides show that Aib containing peptides with chain‐lengths of 12‐15 residues are able to form stable amphiphilic helices in solution. On the other hand, oligopeptides with alternating hydrophilic and hydrophobic residues are capable for β‐structure formation for chain‐lengths of 6‐8 residues. Those amphiphilic secondary structures have been used as building‐blocks for the design and synthesis of artificial folding units, their amphiphilic nature acting as major driving force for intramolecular folding. Spectroscopic data obtained for two polypeptides designed as βαβ‐models actually suggest a folded conformation of these molecules in aqueous solution. The implications of these findings for the design of biologically active folded polypeptides are discussed.
Thermotropic liquid crystalline polymers
Authors: Wendorff Joachim H. , Zimmermann Hans J.
Published: April 2003

Rigid chain molecules have the tendency to display fluid liquid crystalline phases within a limited temperature range. This range depends on the particular chemical structure of the chain molecules. The chain rigidity as well as the intrinsic dynamical and elastic properties of the liquid crystalline melt can successfully be used to obtain high strength, high stiffness polymers, which can be melt processed. The rigid chain polymers display unusual thermodynamical, dynamical, structural, rheological and mechanical properties.
Polymere hochleistungs‐faserverbundwerkstoffe
Authors: Lang R. W. , Stutz H. , Heym M. , Nissen D.
Published: April 2003

Advanced polymer‐matrix composites are defined as materials consisting of continuous high strength, high modulus fibers, aligned and embedded in a polymeric matrix. Due to their low density they exhibit specific mechanical properties (i.e., strength/density and stiffness/density) that considerably exceed those of high strength metals, which demonstrates their great potential for lightweight structural components. The primary reinforcement materials are various types of carbon fibers, aramid fibers and glass fibers. While these are commonly combined with epoxy resins, many new matrix systems with distinct property profiles, including heat resistant thermoplastics, have been developed recently. This paper presents an overview of this rapidly developing field covering principles of composite‐property improvement, synthesis and processing of the constituent materials, and processing and manufacturing techniques to combine fibers and matrix to produce a composite laminate or part. Several mechanical composite properties critical for structural design and performance are discussed in terms of the contribution of and interaction between the fiber and matrix constituent.
High performance thermoplastics
Authors: Hergenrother Paul M.
Published: April 2003

Thermoplastics are currently receiving considerable attention for potential use as structural resins in aerospace vehicles. These materials offer an attractive combination of chemical, physical and mechanical properties. Perhaps the most important advantage offered by the thermoplastics over the new toughened thermosets in composite applications is the potential of low cost manufacturing. However, many problems must be resolved with the thermoplastics before they find extensive use in aerospace composite applications. As part of an effort on improved thermoplastics for use as structural resins, NASA Langley Research Center has been intimately involved in research on polyimides, polyarylene ethers, and polyphenylquinoxalines. Several new semi‐crystalline polyimides with high adhesive properties [e.g. Ti/Ti tensile shear strength @ 25°C of 54.1 MPa] and high fracture energies (GIc) [e.g. 6600 J/M2] are under evaluation. New polyarylene ethers offer glass transition temperatures ranging from 114 to 280°C, crystalline melt temperatures of 275 to 400°C, fracture energies (GIc) as high as 6300 J/M2, and good processability. Ethynyl groups were placed on the ends of arylene ether oligomers and subsequently cured to provide materials with excellent adhesive properties and solvent resistance. In the polyphenyl‐quinoxaline family, various new homo, co and crosslink polymers display improved processability, good mechanical properties, and higher use temperature. The chemistry (structure/property relationships), mechanical and physical properties of these new thermoplastics are discussed herein.
Chain‐extended flexible polymers
Authors: Lemstra P. J. , Bastiaansen C. W. M. , Meijer H. E. H.
Published: April 2003

High‐strength/high‐modulus structures such as fibres, tapes and rods can be produced currently on the basis of intrinsically flexible macromolecules. The prime example amongst these new developments is gelspinning of high‐molecular‐weight polyethylene resulting in fibrous structures possessing tenacities of 3–4 GPa and corresponding moduli up to appr. 150 GPa. The basic aspects of chain‐extension for polyethylene will be discussed in relation to the various routes toward oriented/extended PE structures as well as recent developments concerning the utilization of other flexible polymeric systems for the production of high‐strength/high‐modulus fibres.
Polymere als substrate für optische plattenspeicher
Authors: Hennig Jürgen
Published: April 2003

At the moment PMMA and PC are generally used as substrates for ROM optical discs. In several cases inorganic glass is preferred for DRAW and E‐DRAW information carriers especially because of its high‐barrier characteristics. The benefit of PMMA having low sensitivity to orientation birefringence is opposed by the disadvantage of high water absorption causing warp. It is just the inverse situation with PC. So a polymer material would be desirable which exhibits low optical anisotropy and simultaneously reduced water absorption. The anisotropy problem could possibly be solved regarding additivity of bond polarizabilities within the monomer units, i. e. compensating positive and negative anisotropies by copolymerisation or blending. Reduced water absorption means avoiding polar groups. Polymers are scarcely real barriers against O2 and H2O vapor compared to metals and inorganic glass. PAN and PVDC could be relatively effective as thin layers.
Unvernetzte epoxid‐amin‐additionspolymere, 16. HPLC‐analyse und 13C‐NMR‐spektroskopie von telechelen (diglycidylether‐bisphenol A)‐anilin‐prepolymeren
Authors: Klee Joachim , Hörhold Hans‐Heinrich , Tänzer Wolfram , Fedtke Manfred
Published: April 2003

Es wird über die Herstellung von telechelen Diglycidylether‐Bisphenol A (DGEBA)‐Anilin‐Prepolymeren mit sekundären Aminoendgruppen und ihre Eigenschaften berichtet. Mittels HPLC an LiChrosorb RP‐18 wird die Zusammensetzung der im Zuge der Oligoaddition entstandenen Prepolymermischungen analysiert und ihre chemische Struktur durch C, H, N‐Analysen, M̄n‐Werte (Dampfdruckosmometrie, VPO) und 13C‐NMR‐Spektren belegt.
Influence of synthesis conditions of porous copolymers of 1,4‐DI(methacryloyloxymethyl) naphthalene with divinylbenzene on their structure, 1. Influence of mol composition of monomers
Authors: Matynia T. , Gawdzik B.
Published: April 2003

Porous sorbents for gas chromatography obtained by the copolymerization of two crosslinking agents (1,4‐di(methacryloyloxymethyl)naphthalene and divinylbenzene) in the presence of a two‐component diluent were studied. In order to establish the influence of synthesis conditions on their internal structure, surface areas, pore size distributions, pore volumes as well as polarity of packings were investigated. The influence of 1,4‐di(methacryloyloxymethyl)naphthalene concentration on the surface area was determined for the polymer obtained in the presence of a constant volume ratio of diluents to monomers. The influence of volume ratio of diluents to monomers on pore volume was studied for three series of polymers containing mole fractions of the polar monomer for 0.2, 0.5, and 0.8.
Study of CU(II)‐methacrylic acid — methacrylamide copolymer interactions and formation of metal‐copolymer complexes
Authors: Chatterjee S. K. , Gupta S. , Sethi K. R.
Published: April 2003

The methacrylic acid‐methacrylamide copolymer has been synthesized and characterized by known methods. The interaction of the copolymer with a typical transition metal ion (e.g. Cu2+) has been studied by several experimental techniques, e.g. viscometry, potentiometry, conductometry, IR, and UV spectrophotometry. Formation of metal‐copolymer complexes of distinct stoichiometries have been predicted, and some schemes of complexation have been suggested to explain the mode of interaction between the components.
Graft copolymerization of methyl methacrylate onto jute fibers. Studies on vanadium (V)‐cyclohexanol redox system
Authors: Mohanty A. K. , Singh B. C. , Misra M.
Published: April 2003

Graft copolymerization of methyl methacrylate (MMA) onto natural jute (chemically modified) was studied using V5+ ‐cyclohexanol redox initiator system. The effects of time, concentration of metal ion (V5+), monomer (MMA), substrate, amount of jute fibers, temperature, and acid concentration on graft yield have been studied. The effects of some organic solvents and inorganic salts on graft yield have also been studied. A grafting mechanism is proposed and an expression has been derived for the reaction rate. Grafting has improved the thermal stability and the light fastness of jute fibers dyed with basic dyes. IR spectra of the natural jute (chemically modified) and grafted jute have been taken. More than 170% graft yield could be achieved with the present system.
Enantioface differentiation by using soluble chiral polymers having 2,3‐exo‐bornanediol groups
Authors: Liu Jui‐Hsiang
Published: April 2003

Soluble linear polymers containing 2,3‐exo‐dihydroxy‐3‐endo‐p‐tolyl‐3‐bornyl groups prepared by reaction of lithiated linear polystyrenes with (‐)‐2‐exo‐hydroxy‐3‐bornanone, are treated with lithium aluminium hydride to form complexes which can be used as reducing reagents. The highest enantioselectivity compared with those cases using crosslinked polystyrene as carrier and chiral low molecular weight compounds is achieved by linear polystyrene having chiral groups. The advantages of soluble polymer‐bound chiral reagents are discussed. The effect of alcohols, the reaction temperature, the sort of solvents, and the molar ratio of the reagent to ketone on the asymmetric reduction is also discussed.
Graft copolymerization of unsaturated segmented polyurethanes with 2‐hydroxyethyl methacrylate
Authors: Egboh Sunday H. O.
Published: April 2003

Relatively high molecular weight unsaturated segmented polyurethane synthesized from poly(ethylene glycol), methylene bis(4‐phenyl isocyanate), cis‐2‐butene‐1,4‐diol, and butane‐1,4‐diol was modified by graft copolymerization reaction. 2‐Hydroxyethyl methacrylate (HEMA) monomer was grafted onto the unsaturated segmented polyurethane using 2,2′‐azobisisobutyronitrile (AIBN) as initiator in N,N‐dimethylformamide (DMF) as solvent. The graft copolymers were isolated by selective solvent extraction in a Soxhlet apparatus. The effect of reaction time, initiator concentration, reaction temperature, and monomer concentration on the graft yields has been examined. The graft yields were enhanced by increased monomer concentration and reaction temperature.
Effect of pressing on the diffusional properties of polyacetylene
Authors: Chen Show‐An , Chan Wu‐Chung , Li Liang‐Shun
Published: April 2003

Pressing of polyacetylene films before (or after) sorption of dopant can reduce significantly the rate of sorption (or desorption) due to reduced effective surface area and pore size, as is found in the experiments of vapour sorption and desorption of hexane and iodine. On exposure to air, the pressed films have significantly lower oxidation rates at 120°C than the unpressed ones.
Effect of copolymers modifying PVC on its physical and mechanical properties and its UV‐radiation resistance. VIII. Thermal and photochemical stability of PVC films containing polystyrene and their permeability
Authors: Kamińska A. , Kaczmarek H.
Published: April 2003

The influence of a polystyrene (PS) content of 1–5% in PVC films on their thermal stability, permeability of air and photooxidation, crosslinking, and photodehydrochlorination induced by 253.7 nm wavelength radiation was investigated.

It was found that a small amount of PS in PVC films causes an increase of the permeability of air through these films and does not affect their thermal stability, but evidently improves their photochemical resistance hampering the photodehydrochlorination, crosslinking and photooxidation of PVC.

These degradation processes change the thermal stability of the samples. Smaller changes observed in samples containing PS confirm its photostabilizing effect on PVC. Visible differences between the values of thermal parameters depending on the efficiency of photochemical reaction point out the sensitivity of derivatographic measurements on conversion of PVC caused by UV‐radiation.
Miscibility of chlorinated polymers with epoxidized natural rubber II. Blends with chlorinated polypropylene and with poly(vinylidene chloride‐alkyl acrylate) copolymer
Authors: Kallitsis John K. , Kalfoglou Nikos K.
Published: April 2003

The compatibility of epoxidized natural rubber (at the 50 mol‐% oxirane level) (ENR) with chlorinated polypropylene (CPP) and a poly(vinylidene chloride) copolymer (PVDCC) was investigated in the complete composition range. Phase‐contrast microscopy revealed microheterogeneities attributed to the existence of gel particles in the solution‐cast films. A more uniform phase distribution was obtained in hotpressed films.

Dynamic mechanical spectroscopy and DSC results indicated that both systems are miscible at the segmental level. Ultimate elongation increases at significant (>50 wt.‐%) ENR levels.

The blend modulus dependence on composition supports the view that synergistic effects are present. These can be explained by postulating the existence of intermolecular interactions predicted using suitable models proposed to interpret the compositional variation of Tg.
Syntheses and characterization of polycondensation products derived from ß‐(4‐ethoxyphenyl)glutaconic acid and diols
Authors: Patel Nita R. , Patel Rajni M.
Published: April 2003

Unsaturated polyesters (3a—f) were prepared by condensing ß‐(4‐ethoxyphenyl)‐glutaconic acid (1a) with various diols (2a—f). The polycondensates were characterized by IR, TG, DSC, VPO, and elemental analysis. All polymers were found to decompose in the range of ∼200° to ∼600°C. The kinetic parameters and the stability of the resins are reported.
Synthesis and characterization of resorcinol‐cinnamaldehyde resins
Authors: Žigon Majda , Šebenik Anton , Osredkar Uči , Vizovišek Ivan
Published: April 2003

The mechanisms and kinetics of the reaction between resorcinol and cinnamaldehyde were studied by means of 13C‐NMR spectroscopy, HPLC, and GPC. In the first step the addition of resorcinol to the double bond and to the carbonyl group of cinnamaldehyde takes place. In the second step of reaction the lower molecular weight oligomers form compounds with groups with molecular weights between 1500 and 2500. The red coloured resin reacts at temperatures above 150°C with crosslinking agents to form an insoluble and highly crosslinked product.
Application of a modified polytetrafluoroethylene powder in diaphragms for alkali chloride electrolysis
Authors: Lunkwitz Klaus , Ferse Armin , Handte Dietmar , Klatt Bruno , Horx Manfred
Published: April 2003

A shape retaining asbestos diaphragm which is well suited for alkali chloride solution electrolysis can be obtained from sintering of a mixture of asbestos and a modified polytetrafluoroethylene powder. The usual different polymers of tetrafluoroethylene are not suitable as additives to asbestos diaphragms, whereas an irradiation process permits the production of a modified polytetrafluoroethylene powder which has proved its worth as a component in the diaphragm composition. With reactants present during the irradiation process, functional groups which reduce the water repellency of the polytetrafluoroethylene are incorporated into the polymer. The parallel process of partial polymer chain degradation simultaneously provides an intense reduction of the melt viscosity of the polytetrafluoroethylene so that a composite structure with asbestos can be formed by sintering.
Photo‐oxydation d'elastomères EPDM et EPM en présence de systèmes photosensibles, 2. Rôle de la benzophénone et de ses dérivés
Authors: Bousquet Jean‐Alain , Fouassier Jean‐Pierre
Published: April 2003

Une étude de la photo‐oxydation d'élastomères de type poly[éthyléne‐co‐propéne‐co‐(1,4‐hexadiéne)] (EPDM) et poly(éthyléne‐co‐propéne) (EPM) amorçée dans le proche UV‐visible par la benzophénone (BP) et quelquns de ses dérivés parasubstitués (4‐méthoxy‐BP, 4‐chloro‐BP) a permis l'élaboration d'un schéma réactionnel détaillé. Le comportement photochimique des photo‐amorçeurs dans les milieux élastomère est décrit avec précision (nature et quantité des photoproduits formés) grâce à l'emploi d'une méthode originale de dosage spectrométrique IR. Les processus réactionnels prépondérants sont mis en valeur ainsi que leur dépendance vis à vis d'une part, des propriétés spécifiques du photo‐amorçeur et d'autre part, de la structure et de la composition chimique de l'élastomère.
Photo‐oxydation d'elastomères EPDM et EPM en présence de systèmes photosensibles, 3. Rôle de la benzophénone à l'etat greffé
Authors: Bousquet Jean‐Alain , Fouassier Jean‐Pierre
Published: April 2003

La photo‐oxydation à λ = 313 nm d'un poly[éthyléne‐co‐propéne‐co‐(1,4‐hexadiéne)] (EPDM) greffé contenant en faible quantité des motifs benzophénone, a été étudiée en calculant les rendements quantiques des réactions observées. Il ressort de la comparaison avec les systèmes mélangés que le greffage du photosensibilisateur favorise plus nettement la formation des produits d'oxydation et des coupures de chaînes que la réticulation. Une deuxième comparaison avec un autre système greffé — un EPDM phénylé — permet de montrer que la propagation des hydroperoxydes inactifs dépend fortement de la nature des groupements photosensibles impliqués.
Morphology of glassy polymers grafted onto polybutadiene in relation to monomer diffusivity and initiator solubility
Authors: Beati Enrico , Pegoraro Mario , Pedemonte Enrico
Published: April 2003

The morphology of polybutadiene grafted in emulsion with vinylchloride, methylmethacrylate, styrene, was examined by transmission electron microscopy. The morphology depends on synthesis conditions. Solubility of initiators in the monomers or in water, diffusivity of monomers in the rubber and transfer mechanism during the polymerization were found to be important factors in determining the morphology. New experimental data of diffusion coefficients of the monomers in polybutadiene are given. A special technique was used for liquid VC diffusivity measurements.
Radiation grafting of hydrophilic monomers onto poly(4‐methylpentene‐1), I. Grafting of acrylic acid
Authors: Soebianto Yanti S. , Yoshii F. , Makuuchi K. , Ishigaki I.
Published: April 2003

Radiation grafting of acrylic acid (AAc) onto poly(4‐methylpentene‐1) (TPX) with different crystallinity has been investigated under various conditions. Free radicals formed by pre‐irradiation of TPX in vacuum were more stable than those in the presence of air and might initiate the grafting reaction if come in contact with the AAc. Grafting yields increased with increasing preirradiation dose, grafting temperature, and concentration of AAc. Lower crystalline TPX (24%) showed a higher initial grafting rate compared with higher crystalline one. The distribution of grafting was observed by X‐ray microanalyzer. The grafting reaction proceeded gradually with time from the surface of the film to the inner part. In high crystalline TPX (34%) the grafting distribution in the final stage depended on the film thickness, while in lower crystalline TPX it was homogeneous regardless the film thickness.
Interpenetrating polymer networks from castor oil based polyurethane and poly(methyl methacrylate), III
Authors: Patel Mayur , Suthar Bhikhu
Published: April 2003

Liquid prepolyurethanes (PPU) were obtained from castor oil and toluene‐2,4‐diisocyanate under different experimental conditions varying NCO/OH ratio. All these prepolyurethanes were subsequently interpenetrating with poly(methyl methacrylate) made by radical polymerization initiated with benzoyl peroxide. The novel PPU/PMMA interpenetrating polymer networks were obtained as though films by transfer moulding. They were characterized by thermal studies (DSC and TGA) and mechanical properties viz., tensile strength, modulus of elasticity, and percent elongation at break. The morphological behaviour was analyzed by scanning electron microscopy.
Synthesis and characterization of poly(keto‐amines). 3. poly(keto‐amines) containing phenolic groups
Authors: Patel Surekha V. , Patel Hasmukh S. , Patel Shanti R.
Published: April 2003

Self polycondensations of 5‐amino‐2‐hydroxyphenacyl chloride (5A2HP), 3‐amino‐4‐hydroxyphenacyl chloride (3A4HP), and 4‐amino‐2‐hydroxyphenacyl chloride (4A2HP) are carried out in nitrobenzene using pyridine as an acid acceptor. The poly(keto‐amines) thus formed are characterized by elemental analysis, IR spectral studies, estimation of M̄n by non‐aqueous conductometric titration and/or by VPO method, by measurement of solution viscosity in formic acid, and by TGA in air. All three poly(keto‐amines) are reduced to poly(amines) by Wolf‐Kishner reduction. The poly(amines) thus formed are characterized and compared.

Polymeric metal chelates of poly(keto‐amines) derived from 5A2HP and 3A4HP with various metal ions are prepared and characterized.
Enantioface differentiation by chiral polymers having (+)‐5,6‐exo‐bornanediol moieties, I. Synthesis and polymerization of (+)‐5,6‐exo‐dihydroxybornyl methacrylate
Authors: Liu Jui‐Hsiang , Lin Shyuh‐Rurng
Published: April 2003

A series of bornane derivatives was synthesized. Both new Chiral monomers (+)‐5,6‐dioxobornyl methacrylate and (+)‐5,6‐exo‐dihydroxybornyl methacrylate were prepared from (+)‐borneol. The free‐radical polymerization of both new monomers was carried out at 60°C for 6 h in various organic solvents. The conversion of the polymerization was found to be affected by the kind of solvent, and the lowest conversion was attained in (‐)‐menthol.
Characterization of acrylonitrile‐butadiene‐styrene terpolymers by computer aided FT‐IR spectroscopy
Authors: Fischer G. , Lüderwald I. , Ottenbreit P.
Published: April 2003

The fast identification and accurate characterization of acrylonitrile‐butadienestyrene (ABS) terpolymers by computer aided Fourier transform infrared spectroscopy is described. Samples are prepared as films from chloroform suspensions and identified by a library search routine after FTIR measurement. Calibration curves of monomer specific absorptions obtained from physical mixtures of a known terpolymer with different amounts of the corresponding homopolymers are used to quantify the incorporation ratios of unknown ABS systems.
p‐Chlorostyrene oligomers. Preparation, structure, and stereochemistry
Authors: Kiji Jitsuo , Konishi Hisatoshi , Okano Tamon , Ajiki Eijiro
Published: April 2003

The dimer and trimer obtained by the pyrolysis of poly(p‐chlorostyrene) were 2,4‐di(p‐chlorophenyl)‐1‐butene and 2,4,6‐tri(p‐chlorophenyl)‐1‐hexene, respectively, while those obtained by the cationic oligomerization of p‐chlorostyrene were trans‐1,3‐di(p‐chlorophenyl)‐1‐butene and a diastereomeric pair of trans‐1,3,5‐tri‐(p‐chlorophenyl)‐1‐hexene.
Polymer protected reagents, 1. Esterification with polymer bound AIPO4
Authors: Fernández‐Sánchez C. , Marinas J. M.
Published: April 2003

The advantageous use of a polymer protected reagent ‐AlPO4 as a mild catalyst for esterification was studied.