bluuebunny/crossref_metadata_2025 huggingface dataset:
Wetterbeständigkeit von polymeren: Messung der photochemischen abbauprozesse und der schutzwirkung anorganischer pigmente mittels physikalischer untersuchungsmethoden
Authors: Kämpf G.
Published: April 2003

The photochemical degradation of polymers (commonly known as UV degradation) takes place in two stages: First, there is the primary process comprising the rapid formation of radicals caused by quanta of visible light; this involves the dissociation of polymer chain molecules and/or the activation of polymer chain molecules respectively of additives, colorants and impurities contained in the polymer. The secondary process consists in oxidation reactions with singulett‐oxygen generated by energy‐transfer and/or between the polymer radicals thus formed and adsorbed oxygen, as a result of which gradual degradation of the polymer takes place.

An investigation of these individual reactions using a combination of selected physical test methods leads to an unterstanding of the entire reaction sequence involved in photo‐oxidative degradation. This knowledge provides a basis for systematically improving the weather‐resistance of polymers by modifying their basic polymeric structure or through the controlled use of UV absorbers, quenchers, radical interceptors and antioxidants.

The physical test methods themselves are divided into two categories: techniques used for investigating the primary processes (ultra short‐time spectroscopy, ESR) and those used to investigate the secondary processes (XPS, FT‐IR, UV/VIS et al.).

With pigmented polymers, attention is focussed on borderline cases in the use of photoactive and photoinactive pigments: as a result of “photocatalytic oxidation”, photoactive pigments (e.g. TiO2 anatase) lead to additional degradation reactions which take place at the same time as the UV degradation reaction. Photoinactive pigments (e.g. high‐grade TiO2‐rutile and iron oxide pigments), on the other hand, exhibit negligible or no photocatalytic oxidation and, by absorbing UV radiation, provides better protection for the polymer against UV degradation.

This paper gives an overview of the above‐mentioned physical methods of investigating primary and secondary photochemical processes, taking a thermoplastic material (Polycarbonate) as an example. A description is also given of the photocatalytic oxidation reations which can take place if pigmented polymers are used, and there is a discussion of the degradation‐inhibiting effects of inorganic pigments.
Material wear and erosion at the surface of plastics caused by weathering
Authors: Frank Oliver
Published: April 2003

When exposed to the weather (moderate climate, Darmstadt), polymethylmethacrylate (PMMA) experiences weight changes, depending on the seasonal humidity, but no material loss. Polycarbonate (PC) on the other hand, and to a lesser degree PC with a “weather skin”, shows marked weight changes when exposed to artificial weathering (Xenotest 1200), which set in with some delay.

Surface profile measurements across the borderline between exposed and covered material provide no evidence of material wear in the case of PMMA. With PC, and to a lesser degree with PC protected by a “weather skin”, wear does occur in the region of several μm. The extent of this material wear, which normally sets in with considerable delay after first exposure, is in good agreement with our weight loss measurements. The correlation between outdoor weathering and Xenotest weathering period (shortest wavelength 300 nm) is linear for all degrees of wear (time acceleration factor 13).

Contrary to PMMA, scanning electron micrographs of PC show degradation morphologies dependent on the type of weathering which first develop after a certain weathering period.

The degradation of PC occurs in two steps. Immediately after first weathering an embrittlement of the surface sets in, caused by molecular weight reduction and the formation of short‐chain degradation products. Moreover, as a result of weathering‐related dry/wet cycles and temperature fluctuations, the reduced elongation at break is exceeded locally and eventually cracking at the surface occurs, surface roughness and material loss increase and the gloss reduces.
Ageing behaviour of hot‐water pipes of polybutene‐1
Authors: Kramer E. , Koppelmann J. , Guendouz N.
Published: April 2003

Isothermal Differential Thermal Analysis was used to test the thermooxidative stability of pipes of polybutene during internal pressure tests at 110°C. At low hoop stresses and long testing times pipe failure was exclusively caused by thermooxidative degradation of the polymer.

The stabilizer distribution in the initial state and its alteration during the pressure tests could easily be measured by isothermal DTA. Leaching of antioxidants from pipe walls could be detected. The decrease of residual thermooxidative stability was degressive.

Degradation of pipe material started from the exterior pipe wall. Molecular weight of polybutene decreased rapidly after stabilizer exhaustion which could be observed by isothermal DTA.
Polyethylene recycling during processing
Authors: Jelčič Ž. , Mlinac‐Mišak M. , Turkalj D. , Bravar M.
Published: April 2003

Low‐density polyethylene was recycled in blown‐film production using own factory scrap material. The amounts of the addition of recycled materials to the virgin polyethylene were established, having in mind the fullfilmet of the requirements for quality performances of the obtained films.

In the second part of the paper several successive injection‐mouldings were made on the same low‐density polyethylene. Along with the mechanical characteristics of the obtained reprocessed polyethylene samples, the newly developed method for measuring thermally stimulated depolarization current (TSDC) was evaluated. It was found that the polyethylene samples reprocessed several times differ between themselves also by the fact that the current peaks appeared at some characteristic polymer temperatures, depending on the number of reprocessing cycles, and in lesser degree also, depending on the abcence or the presence of a heat stabilizer.
Possibilities for predicting the change in properties of polyolefins at natural ageing
Authors: Peeva Lili , Fileva Blagovesta , Evtimova Sonya , Tsveteva Vichra
Published: April 2003

A base of experimental data on the ageing of commerial grade plastics is created. In includes assorted physical and chemical properties of plastics and their changes at natural ageing. An automated system for storing and processing of the experimental data is designed. Processing involves mathematical modeling of the changes in properties that aids in empirical prediction. The possibilities of the system are verified with experimental results from a 5‐year ageing period of PE‐LD and PE‐HD. The results show a good agreement between the predicted and real data for selected models.
The thermal stability of rigid polyurethane foam in insulating pipes
Authors: Rek Vesna , Hace Drago , Braver Mladen , Jagodar Andrija
Published: April 2003

The rigid polyurethane, PUR, foam was prepared by reacting diphenylmethane diisocyanate, MDI, with aliphatic correactants of polyether type.

The insulating pipe was made by moulding technic. The PUR pipe was subjected to isothermal aging by special equipment which was constructed for this purpose in order to study the structural changes in PUR foam under various temperatures and to define the maximal temperature at which it might be used as insulation in insulating pipes.

The structural changes of PUR foam were studied by means of spectrophoto‐metric measurement and thermal analysis.

The evidence of thermal degradation of PUR foam has been found. Its course and intensity depend upon the temperature and differ throught the verticale cross‐section of the insulating pipe.

The correlation between chemical changes of PUR foam and its physical properties are also discussed.
Bewitterung von schwermetallfreien PVC‐fensterprofilen
Authors: Imhof J. , Stern P. , Egger A.
Published: April 2003

The weathering behaviour of lead/barium/cadmium‐respectively barium/cadmium‐stabilized profiles has been compared with new developed profiles which are free from heavy metals, the so‐called HMF profiles.

The weathering tests have been made out doors, in Xenotest 450, QUV(A), and QUV(B). The colourmetric values (ΔE, ΔL, ΔA, ΔB) and the loss of brightness were measured in dependence of weathering time. The results of QUV(A) measurements were not suitable for practical application, but the findings of the total colour difference of QUV (A) measurements correlate very well with the results of out door weathering. With respect to the surface attack HMF‐stabilized profiles are equivalent to the lead/barium/cadmium standard profiles or even superior. The colourmetric behaviour of the new developed HMF profiles is equivalent to the lead/barium/cadmium standard profiles.
Alterung und degradation des leders
Authors: Bajza Ž. , Kovačević V. , Vuković T. , Tucaković‐Mujagić L.
Published: April 2003

Leather has been an important natural polymer undergoing aging when exposed to physical (temperature, radiation) and chemical (oxygen, water, metal ions) deteriogens. Degradation of collagen and changes of mechanical properties of leather are the consequences. The aging has been influenced by tan process, by changes of pH due to chemical degradation and by losses of fat due to extraction or blooming. The understanding of degradation process taking place in leather is necessary for the restoration of aged products from leather having a historical value.
Processing stabilization of polyolefins
Authors: Drake W. O. , Pauquet J. R. , Todesco R. V. , Zweifel H.
Published: April 2003

The response of a HDPE, a L‐LDPE and a PP homopolymer to processing conditions and processing stabilizer formulations in the 220°C to 280°C temperature range was investigated. The technique of multiple extrusion was used. Melt flow and melt flow ratio were measured after the first, third and fifth extrusion pass. In the case of the HDPE and the L‐LDPE, degradation by cross‐linking was the predominant reaction and the molecular weight distribution showed a significant broadening compared to the virgin samples. The PP homopolymer degraded by chain scission. By adding a multifunctional hindered phenol and a hydrolysis resistant phosphite, all polymers could be efficiently protected against degradation on processing. For the HDPE and the L‐LDPE, increased amounts of phosphite provided increased processing stability at constant phenol concentration. A 4:1 ratio of phosphite to phenol exhibited the best performance. The most efficient ratio for protecting melt flow of the PP homopolymer was found when a two to one ratio of phosphite to phenol was added.
Mechanisms and kinetics of photostabilization of polyolefins with hals
Authors: Gugumus F.
Published: April 2003

The HALS stabilization mechanisms usually envisaged do not explain the experimental facts. New mechanisms are proposed instead. They include quenching of excited charge‐transfer complexes (CTC) polymer‐oxygen by CTC HALS‐oxygen. In addition, the formation of CTC between peroxy radicals and NH‐HALS is of prime importance. These CTC HALS‐peroxy radicals can either react photolytically after absorption of UV radiation or with a second peroxy radical, thus promoting termination between two peroxy radicals.

Initiation of photooxidation in HALS stabilized polyethylene involves usually CTC HALS‐oxygen throughout the useful lifetime of the polymer. In contrast to that, initiation of photooxidation in HALS stabilized polypropylene is classical and due to photolysis of tertiary hydroperoxides.

The formal kinetics based on the mechanisms envisaged explain the experimental results observed with HALS stabilized polyethylene and polypropylene. On the one hand, they concern, the performance of HALS: in polyethylene it is a linear function of the square root of HALS concentration whereas in polypropylene it increases linearly with HALS concentration as long as the last does not become too high. On the other hand, the experimental facts explained, concern the decrease of the HALS concentration during W exposure of HALS‐stabilized polyethylene and polypropylene. The decrease is first order in both polymers but is independent of the initial HALS concentration in polyethylene, whereas it decreases with increasing initial HALS concentration in polypropylene. This is in agreement with the corresponding initiation mechanisms envisaged for polyethylene and polypropylene.
Stabilization of polypropylene by esters of 2,2,6,6 ‐ tetramethyl 4‐piperidinole
Authors: Považancová Marta , Danko Peter , Karvaš Milan , Klimová Marta , Čaučík Pavol , Durmis Július
Published: April 2003

The effect of the substituents R and X in esters of 2,2,6,6‐tetramethyl‐4‐piperidinole of the general formula 1
magnified image
on their stabilizing efficiency in polypropylene was investigated. As the substituents R, the aliphatic alkyls CH3 (CH2)n were used, where n=0‐16, X=H. By the derivative where R is an alkyl with 13 to 17 carbon atoms the affect of the substituent X was also investigated where X is H, 0, OH, OR. Both the thermooxidation and photooxidation stability of PP were found to be increased with the increasing chain length R. The effect of the substituents X is various. Both and stabilizers have high efficiency during the processing of PP. At the long‐term thermooxidation stress, the , and derivatives are more efficient than compounds which are the most efficient against the effect of the ultraviolet radiation and photooxidation.
Einfluss von verarbeitungsbedingungen und additiven auf die abbaureaktionen von SIS‐blockcopolymeren
Authors: Knobloch Gerrit
Published: April 2003

SIS block copolymers are used particularly as polymer component in hot melt adhesives. During compounding at temperatures of 170–180°C undesired viscosity decrease occurs occasionally.

For that reason the influence of additives and the role of compounding conditions, particularly the oxygen concentration, on the degradation of SIS has been investigated.

It was found that primary antioxidants are unable to reduce the degradation of SIS under anaerobic or oxygen deficient conditions, but they are very effective when excess of oxygen is present in the system (e.g. an open mixer or mill).

C‐radical scavengers reduce the chain scission reaction at high oxygen concentrations, too, but accelerate the decrease of the molecular weight under inert gas atmosphere.
Depolarization current of a novolac p‐fluorophenol‐formaldehyde resin
Authors: Topić Mladen , Katović Zvonimir
Published: April 2003

A Novolac p‐fluorophenol‐formaldehyde (NFF) resin was prepared by condensation of p‐fluorophenol with formaldehyde. DSC showed the glass transition effect or coinciding endothermal peak depending upon the thermal history of samples. It is supposed that the peaks are caused by breaking of the intermolecular bondings in the resin during the glass transition. The bondings are formed in the resin during the storage at room temperature. Thermally stimulated depolarization current (TSDC) measurements were carried out in the temperature range of 290 to 350 K, with the samples having an average number molecular weight M̄n of 375 and 434. TSDC curves mainly showed the dipolar relaxation α peaks. The influence of poling temperatures, the influence of M̄n, the activation energy Ea, and the physical ageing of the samples were investigated. Physical ageing was determined as the reciprocal polarizability Rp vs. time of ageing. Samples. with higher M̄n showed a higher glass transition temperature, a lower Ea, and a higher increase in Rp than the sample with lower M̄n. The increase in M̄n increased the rigidness of NFF samples. The effects are attributed to the strong hydrogen bonding. The comparison with analogous results in novolac phenol‐formaldehyde resin without fluorine is given.
Influence de l'epaisseur de l'adhésif et du vieillissement sur les propriétés mécaniques dynamiques d'un assemblage: Adhésif structural/acier inoxydable
Authors: Bourahla Hamid , Lenoir Jeanine , Romand Maurice , Chauchard Jean
Published: April 2003

Dynamic mechanical properties of bounded joints—stainless steel/epoxy adhesive—are investigated as a function of the thickness of the adhesive and aging conditions. The viscoelastic properties of the bounded joints have been investigated by Dynamic Thermo Mechanical Analysis (DTMA).

The glass transition temperature (Tg) showed a dependence on both the chemical/electrochemical pretreatments of the substrate and the thickness of the adhesive in the bounded joint. The crosslinking density in the adhesive thus seemed more important in the interfacial region than in adhesion bulk.

The water uptake induces a plasticization of the adhesive and a decrease in Tg. The most stable bounded joints were obtained by carrying out sulfochromic acid anodization as a pretreatment step. The most important stability of the bounded joints was obtained with the sulfochromic anodization of the substrate.
Unvernetzte epoxid‐amin‐additionspolymere, 25. Oligoether‐diamine als elastifizierende comonomere für lineare epoxid‐amin‐additionspolymere
Authors: Klee Joachim , Hürhold Hans‐Heinrich , Flammersheim Hans‐Jörgen
Published: April 2003

N,N'‐Dibenzyl‐3,6‐dioxaoctandiamin‐1,8 und drei analoge sekundäre Diamine mit langen aliphatischen Ethergruppierungen (EDA) sind hergestellt und mit Bisphenol‐A‐diglycidylether DGEBA polymerisiert worden. Der lineare Charakter der Additions‐polymerisation wurde durch die Molmassenverteilung, Mw/Mn = 2, sowie elementaranalytische und spektroskopische Untersuchungen der Additionspolymeren und ihrer Hydroxylderivate (Acetate, Dicarbonsäurehalbester, Urethane) belegt.

Durch ein verbessertes Reaktionsmodell wurde die Epoxid‐Amin‐Reaktion in ausgezeichneter Übereinstimmung mit dem Experiment (Zeit‐Umsatz‐Kurve und dynamische Wärmekapazitätsmessung) bis zum höchsmöglichen Umsatz beschrieben. Das Reaktionsmodell berücksichtigt die nichtkatalysierte Reaktion und eine durch Addukt‐OH‐Gruppen katalysierte Parallelreaktion.
Graft polymerization of 4‐vinylpyridine onto cellulosic fibres by the ceric ion method, I. The reaction time effect
Authors: Leza M. Lourdes , Casinos Ismael , Guzmán Gonzalo M. , Bello Antonio
Published: April 2003

A study was made of the time affecting the ceric ion induced grafting of 4‐vinylpyridine (4‐VP) onto partially carboxymethylated cotton (PCMC) having different degrees of substitution (D.S.). For comparison the same monomer was grafted onto cotton and mercerized cotton. The grafting parameters of these copolymerization reactions were determined. The graft yields for PCMC were significantly higher than those for unmodified cotton and mercerized cotton. The degree of crystallinity of the graft copolymers and of the unmodified cotton and PCMC samples was determined by the X‐ray method. The crystallinity index decreased with the presence of grafted polymer. The reaction time effect of the grafting of 2‐VP on cotton was also studied.
Light induced polymer and polymerization reactions, 35. Influence of monomer structure and binder composition on the photoinduced polymerization of multifunctional acrylic esters
Authors: Timpe Hans‐Joachim , Strehmel Bernd
Published: April 2003

Photocalorimetry, differential scanning calorimetry and ESR‐spectroscopy were used to analyse the photoinduced polymerization of multifunctional acrylic esters in various polymeric binders. Limiting conversion, maximal polymerization rate, inhibition time, and the time necessary to reach the maximum of the polymerization reaction rate were used to compare the reactivity of the photopolymer systems investigated in this work. Significant correlations exist between the limiting conversion and chemical structure of the acrylic esters used. A relation was also found between the glass transition temperature and oxygen permeability of the binder and the limiting conversion measured calorimetrically. A good correlation does not exist for the other reactivity parameters, because other factors such as phase change and changing diffusion conditions can have a complex influence on those values.
Oberflächenstrukturierung polymerer fasern durch UV‐laserbestrahlung. 6. Zur vermeidung von vergilbungen bei der laserbehandlung von polymeren
Authors: Knittel Dierk , Schollmeyer Eckhard
Published: April 2003

Es wird gezeigt, daß die Ausbildung einer Schicht von verfärbenden Lasercrackprodukten – wie sie bei der Laserbehandlung von trockenen Polymeren gebildet wird – durch Imprägnierung mit verschiedenen Lösungsmitteln während der Laserbearbeitung verhindert werden kann. Die Ausbildung einer laserinduzierten Mikrostrukturierung der Polymeroberfläche wird davon nicht beeinflußt. Es läßt sich damit auch bei stärkeren Energiedichten der Laserbehandlung ein hoher Weißgrad aufrechterhalten.

Zur Verhinderung der Vergilbung sind Wasser, Alkohole, Ether und wäßrige Tensidlösungen als Imprägniermedien während der Laserbestrahlung vorteilhaft einsetzbar.
Matériaux composites à base de bois retifié II. Etudes des propriétés mecaniques de differents mélanges
Authors: May J. F. , Guyonnet R. , Bourgois J.
Published: April 2003

Divers matériaux composites à base de bois de pin rétifié ont été préparés. Leurs propriétés mécaniques sont comparées à celles des matériaux composites développés a l'aide de charges minérales (oxyde de zinc, silicate de magnésium, verre) ou organique (farine de pin naturel) et de matrices apolaires (polypropyléne) ou polaires (polychlorure de vinyle, poly(acrylonitrile‐butadiéne‐styrene)) pour différents taux de charges. Le comportement des melanges varie avec la nature du polymére: amélioration des propriétés mécaniques avec le bois rétifié et les resines polaires. Une généralisation de I'interprétation de ces différences de comportement, basée sur l'existence d'intéractions fibre‐matrice, est proposée. Des mesures de gonflement et de reprise de masse en milieu humide des composites préparés confirme l'interêt de l'utilisation du bois rétifié comme charge des matiéres plastiques polaires.
Solution properties of polyacrylic esters. II. Evaluation of unperturbed dimensions
Authors: Penzel Erich , Goetz Norbert
Published: April 2003

According to existing well‐known theories unperturbed dimensions can be calculated from light scattering and viscosity measurements. The statistical segment Am proposed by Kuhn is a good measure for the flexibility of an unperturbed polymer coil. With the data reported in part I of the dependence of the radius of gyration and the Staudinger index, respectively, on the molecular weight, Am was calculated for nine polyacrylic esters and poly(acrylic acid). Poly(acrylic acid) with Am = 13,6 Å has the highest flexibility. The stiffness of the polymer chain is increased with growing C‐number of the alcohol. Branching in the alcohol further increases the stiffness of the polymer chain.
Analysis of the linear methods for determining copolymerization reactivity ratios, VIII. A critical reexamination of radical copolymerization of methylmethacrylate or styrene
Authors: Braun Dietrich , Czerwinski Wojciech K. , Tüdős Ferenc , Turcsanyi Béla , Kelen Tibor
Published: April 2003

The reactivity ratios of selected methylmethacrylate or styrene copolymerisation systems have been reviewed in terms of the extended Kelen‐Tüdős method. r‐values, together with their 95% confidence limits have been calculated. Quantities δ and Q, suitable for classification of the systems, have been applied. Of the 71 reevaluated methylmethacrylate systems 40 (56.3%) were found to belong to class I and 20 (28.2%) to class I(!), i. e. 60 (84.5%) systems for which the conventional copolymerisation equation was found to be adequate. For 3 (4.2%) systems belonging to class II the two‐parameter model does not hold and 8 (11.3%) systems were related to class III, i. e. systems for which the experimental data are inconsistent and the published r‐values meaningless. 32 styrene copolymerisation systems were reevaluated with the following classification: 19 (59.4%) systems in class I, 5 (15.6%) systems in class I(!), 2 systems in class II and 6 (18.8%) in class III.
A new approach to welding and lamination of polyamides
Authors: Avramova Nadka , Fakirov Stoyko
Published: April 2003

An attempt is made to provide a simple and inexpensive method for the lamination of polyamides. A new application of a known reaction – methoxymethylation of polyamides – is proposed: creation of chemical bonds at the interfacial boundary between two contacting surfaces, i. e. welding and lamination of polymides. Commercial polyamide‐6 films are used in this study. As a result of the creation of methylene bridges between neighboring amide groups welding of the films takes place. After the pressing for 30 h of films coated in a methoxymethylation solution, the welding is so strong that during the mechanical tests, instead of delamination, breaking of the films outside the overlapped area occurs.
Studies of the surface structure of plasma‐modified fillers and their application in PVC and PP compounds
Authors: Cai Shide , Ji Gending , Fang Jianglin , Xue Gi
Published: April 2003

Fillers for PVC and PP compounds have been treated by microwave plasma. FT‐IR photoacoustic spectroscopy studies show that the plasma polymer sheath on filler's surface contains CC, CH2, CH3 groups, etc. X‐ray photoelectron spectroscopy studies reveal that interfacial chemical bondings exist between silica and the organic coating. Application of plasma‐treated fillers in PVC and PP compounds gives rise to materials of good mechanical properties and low cost.
SBS/VP homograft membrane for oxygen enrichment
Authors: Yang Jen‐Ming , Hsiue Ging‐Ho
Published: April 2003

The grafting of 4‐vinyl pyridine (VP) onto styrene‐butadiene‐styrene triblock copolymers (SBS) by homografting irradiation with dissolved oxygen was studied. Homograft membranes of various degree of grafting were prepared from a casting solution of grafted copolymer in benzene. The mechanical properties of membranes, gas permeability, and the effect of operating temperature on gas permeation were investigated.

The degree of grafting of 8.4% was the largest at an irradiation time of about 15.5 h. It was smaller at both shorter and longer duration because of the interference of dissolved oxygen. It was found that the tensile strength and elongation of SBS‐g‐VP were similar to those of SBS. The stress relaxation of SBS‐g‐VP was slower than that of SBS, and this might be due to the formation of rigid microphase separation domain of poly(4‐vinyl pyridine), which acted as permanent crosslinking points to reduce the stress relaxation.

Using the properties of high flux of SBS and high O2/N2 selectivity of poly(4‐vinyl pyridine), the performance of gas permeation of 4‐vinyl pyridine homografted SBS membrane was studied. The selectivity of SBS‐g‐VP membrane increased with increasing degree of grafting. However, it was done at the expense of a decrease in the gas permeability.

When the operating temperature of gas permeation increased, the permeability of oxygen and nitrogen increased, and the O2/N2 permeability ratio decreased. The activation energy (Ep) for gas permeation through different degree of grafting of SBS‐g‐VP membrane (obtained by the Arrhenius law) increased with increasing degree of grafting. For ungrafted SBS membrane, Ep was 5.5 kcal/mol for oxygen and 7.2 kcal/mol for nitrogen. For 8.4% grafting degree SBS‐g‐VP membrane, Ep for oxygen and nitrogen, were 6.5 and 8.1 kcal/mol, respectively.
Optische Methoden zur Charakterisierung von hochpolymeren Fasern. 2. Kennzeichnung von Oberflächen durch Specklemeßmethoden.
Authors: Eickmeier Achim , Bahners Thomas , Kleemann Wolfgang , Schollmeyer Eckhard
Published: April 2003

Die Oberflächenrauheit ist eine der wesentlichen Eigenschaften textiler Materialien, die sowohl deren Gebrauchs‐ als auch Verarbeitungsverhalten beeinflußt. Die vorgestellten Specklemeßmethoden sind kohärent‐optische Streulichtmeßmethoden, die zur integralen, berührungslosen und zerstörungsfreien Erfassung von Oberflächenstrukturen herangezogen werden. Die Untersuchungen werden mit Verfahren der Specklekontrastmessung und der Korrelation dichromatischer Specklemuster durchgeführt. Sie erstrecken sich auf transparente Dielektrika (Mattglas, Plexiglas und Polyester folie), um zunächst sicherzustellen, daß die Eigenschaften der Specklefelder auch für Hochpolymere erhalten bleiben. Als Ausblick wird die Anwendung von Specklemeßmethoden auf textile Werkstoffe in den drei Ebenen Filament bzw. Faser, Garn und Gewebe diskutiert.
Urease immobilized polyethylene‐g‐acrylic acid membrane for urea sensor
Authors: Hsiue Ging‐Ho , Wang Chee‐Chan , Chen Chin‐Yun , Chang Chi‐Jung
Published: April 2003

A new type of polymer support for immobilizing urease was investigated. The starting copolymers which grafted acrylic acid onto polyethylene (PE‐g‐AA) were prepared via gamma ray irradiation induced grafting under controlled conditions by postirradiation procedures. The optimum conditions for coupling urease to PE‐g‐AA were established and the physical properties of the support affecting the immobilized enzyme activity were studied.

A water soluble carbodiimide (CMC) was used as a condensing agent to immobilize urease. The activities of the resulting enzyme membranes were very high. The hydrophilicity of the support and the activity of the enzyme membrane were proportional to the degree of grafting. Its linear detecting range was 60–400 ppm.
A search for optimal acrylic carriers for immobilization of penicillin acylase
Authors: Kolarz Bożena N. , Trochimczuk Andrzej , Bryjak Jolanta , Wojaczynska Maria , Dziegielewski Kazimierz , Noworyta Andrzej
Published: April 2003

Acrylic carriers were obtained by aminolysis of nitrile or ester groups in copolymers or terpolymers synthesized from acrylonitrile, acrylic esters and divinylbenzene or ethylene dimethacrylate in the presence of a mixture of inert diluents. The influence of the supermolecular structure of these carriers, generated during the suspension polymerization by adding a mixture of inert diluents, on the carrier properties was observed. Acrylic carriers for immobilization of penicillin acylase should be obtained from either porous or ‘sol’‐type copolymers which aquire after aminolysis the structure of expanded gel.
The effect of conditions of mixing of polypropylene/ethylene‐propylene elastomer blends on their morphological structure and impact strength
Authors: Fortelný Ivan , Michálková Danuše , Koplíková Jaroslava , Navrátilová Edita , Kovář Josef
Published: April 2003

The dependence of morphological structure and notch impact strength of polypropylene/ethylene‐propylene elastomer blends on conditions of mixing was investigated. Two types of polypropylene and two types of ethylene‐propylene elastomer having different viscosities were used. At low rates and short times of mixing the samples contain both regions showing fine dispersion and regions showing large elastomeric inclusions surrounded with pure polypropylene. With increasing rate and time of mixing the large inclusions gradually disappear. The conditions of mixing which are necessary for reaching a homogeneous structure of the blends depend on viscosities of the components. The independence of particle size of the rate of mixing in homogeneous samples is discussed on the basis of a dynamic equilibrium between the break up and coalescence of droplets. The notch impact strength of the individual samples of the same blend is determined by the size and number of inhomogeneities (large inclusions) in the given sample.
Stress relaxation behaviour of liquid crystalline solutions of ethyl celluloses with different molecular weight in m‐cresol
Authors: Suto Shinichi , Sasaki Kiyoo , Tateyama Shinichiro
Published: April 2003

The stress relaxation behaviour of liquid crystal‐forming ethyl celllulose (EC) solutions in m‐cresol was determined by means of a cone‐plate type viscometer at 30°C. The effect of molecular weight (MW) on the behaviour was also determined. The relaxation behaviour could be fitted with the following equation:

where σi and σf are steady‐state shear stresses at shear rate \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma _{\rm i}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma _{\rm f}$\end{document}, σ(t) is time‐ dependent stress, A1 and A2 are constants, τ1 and τ2 are relaxation times, t is time, and tc is a characteristic time. When log σ* was plotted against time, one straight line was obtained for isotropic solutions, whereas anisotropic solutions yielded two straight lines. This suggests that the liquid crystalline solutions have two separate relaxation processes: Process 1 has a relatively short relaxation time, and process 2 has a long one. The parameters τ1, τ2, and A2 were greatly dependent on polymer concentration, combination of \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma _{\rm i}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma _{\rm f}$\end{document}, and MW, whereas A1 was independent thereof and was close to unity. The process 1 was supposed to be valid for individual molecules, and process 2 for liquid crystalline domains or randomly aggregated or entangled molecules.
Einige offene Fragen in der Rheologie der Polymerschmelzen
Authors: Wagner Manfred H.
Published: April 2003

Dieser Beitrag, der sich auf die Rheologie homogener, isotroper Polymerschmelzen beschränkt, gibt eine zusammenfassende Darstellung wesentlicher Erkenntnisse bei der Entwicklung einer rheologischen Zustandsgleichung und weist auf zwei offene Fragestellungen hin, die z. Z. Themen aktueller Forschung sind. Diese sind erstens der Zusammenhang zwischen linear‐viskoelastischem Relaxationszeitspektrum und dem molekularen Aufbau einer Polymerschmelze, und zweitens die Formulierung einer rheologischen Zustandsgleichung für allgemeine biaxiale Dehnungen.
Synthesis and characterization of ethylenediaminecellulose‐poly(glycidyl methacrylate) anion exchanger
Authors: Abou‐Shosha M. H. , Ibrahim N. A.
Published: April 2003

The synthesis of ethylenediamine‐cellulose‐poly(glycidyl methacrylate) anion exchanger was achieved by the reaction of ethylenediamine with cellulose‐poly(glycidyl methacrylate) copolymer. The effect of time, temperature, epoxy content, liquor ratio, ethylenediamine concentration and percent neutralization of the amine by acetic acid is reported. Reaction conditions were selected to synthesize an anion exchanger having a capacity of 196 meq/100 g. Potentiometric titration showed that this exchanger is a weak base anion exchanger having a pKb of 8.4, and its replaceable groups consisted of about 37.5% as primary amino groups and 62.5% as a mixture of both secondary and tertiary amino groups. Durability to use as well as water solubility of the prepared exchanger were investigated.
FTIR‐ATR study of interactions in polymer blends containing polyesterurethane
Authors: Sack Stephan , Haudel Gottfried
Published: April 2003

Molecular interactions such as especially hydrogen bondings are considered to play a key role in polymer compatibility. In this study binary blends produced by extrusion of a MDI based segmented polyesterurethane (TPU) together with styrene‐acrylonitrile and acrylonitrile‐butadiene‐styrene copolymers, respectively, could be investigated without additional sample preparation using the infrared spectroscopic sampling technique of attenuated total reflection (ATR). With increasing content of the nitrile group containing polymers in the blends urethane carbonyl groups completely hydrogen bonded in the pure TPU are liberated. “Free” NH groups, however, are not detectable in the NH stretching region of the ATR spectra of the blends. The interpretation of the obtained spectral effects occurring in the blends is supported by experiments with N‐butyl‐carbamideacid‐methylester as model compound with an urethane linkage. The presented results lead to the conclusion, that intermolecular hydrogen bonding involving urethane NH groups and nitrile groups of the other polymers in the blends has been arised. Quantitative differences of these interactions between the two kinds of blends investigated in this study are discussed.
X‐ray scattering investigations of acrylonitrileethylene oxide block copolymers
Authors: Kwiatkowski Ryszard , Wlochowicz Andrzej , Wódka Tadeusz
Published: April 2003

Wide angle (WAXS) and small angle (SAXS) X‐ray scattering studies are reported on block copolymers of acrylonitrile with ethylene oxide. A distinct structural similarity between the copolymers and acrylonitrile homopolymer has been found. Considerable porosity of the copolymers has been shown. The porosity very largely governs the scattering power. It was found that the pores are three dimensional “particles” (scattering exponent α = 4), probably with smooth surfaces (surface fractal dimension ds = 2).
Beziehungen zwischen herstellung, struktur und mechanischen eigenschaften bei elastmodifizierten, schlagzähen styrolpolymeren
Authors: Michler Goerg H. , Hamann Bernd , Runge Jürgen
Published: April 2003

Kautschukhaltige Polystyrole mit unterschiedlichem Schlagzähigkeitsniveau, hergestellt durch Variation der Polymerisationsbedingungen, wurden hinsichtlich ihrer Morphologie und Zähigkeit eingehend untersucht. Auf der Grundlage transmissionselektronenmikroskopischer Strukturuntersuchungen wurden charakteristische Merkmale der Kautschukteilchen ermittelt und sechs Strukturtypen definiert. Mit Hilfe der Untersuchung gedehnter dünner Proben in einem 1000 kV‐Höchstspannungs‐Elektronenmikroskop wurden mikromechanische Prozesse, insbesondere die Craze‐Bildung, die die Eigenschaft der Zähigkeit vor allem bestimmt, analysiert. Die quantitative Auswertung dieser Untersuchungen führte nicht nur zu einer qualitativen, sondern auch zueiner quantitativen Korrelation zwischen der Größenverteilung der Kautschukpartikel und der Zähigkeit der Proben.
Untersuchung der molmassenverteilung von harnstoff‐formaldehyd‐leimharzen durch GPC gekoppelt mit lichtstreuung
Authors: Billiani Johann , Lederer Klaus , Dunky Manfred
Published: April 2003

Es wurden UF‐Harze mit verschiedenen Kondensationsgraden durch unterschiedlich lange saure Kondensation hergestellt und mittels Gelpermeationschromatographie (GPC), gekoppelt mit einem Kleinwinkel‐Laserlichtstreugerät (LALLS), untersucht. Aus den Konzentrations‐ bzw. Lichtstreukurven kann die jeweilige Molmassenfunktion IgMw(V) sowie das Molmassengewichtsmittel berechnet werden. Dieses steigt mit fortschreitender Kondensation analog zur Trübungstemperatur der einzelnen Kondensationsstufe deutlich an und liegt im Bereich von einigen Tausend bis über 100000g/mol. Zusätzlich wurde festgestellt, daß in UF‐Harzen Molmassen bis ca. 500000g/mol enthalten sind; dabei handelt es sich offensichtlich um Aggregate, die nicht nur durch physikalische Wechselwirkungen hervorgerufen werden.
Grafting of 2‐(dimethylamino)ethyl methacrylate on linear low density polyethylene in the melt
Authors: Song Zhiqiang , Baker Warren E.
Published: April 2003

Grafting of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) on linear low density polyethylene (LLDPE) in the melt has been studied through measurements of monomer conversion, the degree of grafting and the grafting efficiency. Results show that the grafting of DMAEMA on LLDPE can be carried out in the melt at temperatures as low as 90°C even though the melting point of the LLDPE is as high as 120°C. When the grafting reaction is carried out at too low or too high temperature, a low degree of grafting is observed. High reaction temperature favoured crosslinking of the polymer as indicated by decreasing melt flow index. Most of the grafts were obtained during the early period of the reaction (before 3 min under the reaction conditions used). Further increase in reaction time increased crosslinking and also produced more homopolymer, thus decreasing the grafting efficiency. Organic peroxides are effective initiators for the grafting reaction over a broad range of half‐lives while azo initiators do not produce grafting.
Thermal degradation of poly(vinyl chloride) blends
Authors: Braun Dietrich , Böhringer Bertram , Knoll Wolfgang , Eidam Norbert , Mao Weiyou
Published: April 2003

Poly(vinyl chloride) was mixed with various poly(methacrylate)s and polycarbonates by combined precipitation from common solutions. The thermal stability of the samples was measured at 180°C under nitrogen, the HCl evolved was detected by conductometry.

UV‐Vis‐spectra of degraded samples were measured to investigate the influence of the poly(methacrylate)s on the lengths of polyenes formed during the degradation of poly(vinyl chloride).

The experiments show that the nature of the ester group is the dominating factor for the thermal stability of poly(vinyl chloride) in these blends. Poly(n‐butylmethacrylate) exhibits the best stabilization for poly(vinyl chloride) in this series. Polycarbonates with a higher glass transition temperature than the temperature of degradation destabilize poly(vinyl chloride).

Stabilization experiments with dibutyltin‐bis(isooctylthioglycolate) show a costabilizing effect of the poly(methacrylate)s and polycarbonates.
Herstellung von dispersionen anionischer polyurethane mit COO− ‐gruppen und NH ‐gegenionen
Authors: Lorenz O. , Brocker J. , Haulena F.
Published: April 2003

In Dispersionen aus anionischen Polyurethanen, die das Triethylammoniumsalz der 2,2‐Dimethylolpropionsäure als Kettenverlängerungsmittel enthalten, läßt sich durch Zugabe von Ammoniak eine weitgehende Verdrängung des Triethylamins erreichen. Aus elektrostatischen Gründen ist nämlich in den in der Sternschen Schicht lokalisierten Ionenpaaren NH fester gebunden als NH(C2H5). Bei der thermischen Behandlung der Filme tritt Basenabspaltung ein, dabei erfolgt die Abgabe von Ammoniak deutlich schneller als die von Triethylamin. Die Spannungswerte der mit teilmethyliertem Hexamethylolmelamin vernetzten Proben sind daher um so höher, je mehr Triethylamin durch Ammoniak ersetzt wurde.
Compression creep of molten polystyrene
Authors: Aleman J. V.
Published: April 2003

Viscoelastic parameters of polystyrene (PS) melt in compression creep have been measured in an lnstron capillary‐rheometer.

Bulk compression creep compliance B(t) shows plateau regions in the molten state (B1) and the glassy state (Bg), both decreasing with increasing stress. Shifting of B(t) curves provides master curves suitable to analysing the total (superposed elastic and viscous deformations) bulk compression behaviour. The steady‐state creep compliance (Bs) allows to describe the recoverable elastic energy (Be) and seems to be related to the extrusion die swell (B/B). Volume viscosity (ηk) decreases with decreasing stress (P), increasing compression rates (k) and decreasing temperature (T).
Variation in molecular weight and molecular weight distribution of aged iPP filaments as revealed by HTGPC
Authors: Sadiku Emmanuel Rotimi , Peacock Norman
Published: April 2003

Experiments on the molecular weight variations of physically, room temperature aged isotactic polypropylene (iPP) filaments were done using the High Temperature Gel Permeation Chromatography (HTGPC). Evidence emanating from the studies indicates a very marginal change in molecular weight of the materials during aging.

The granules of the materials were chosen as the reference standard. Based on the polydispersity D = Mw/Mn of the granules, filaments of commercial grades GYE 47 and PXC 31399 were characterized between an aging period ranging from 2 weeks to 8 months. The filaments of the GYE 47 grade have their distributions D lowered on the average by about 12%. On the other hand, those of the PXC 31399 grade have a less definite trend in change, but on the average, D is lowered by about 20%. The distributions of this latter grade are highly scattered over the period of aging. The GYE 47 grade shows a reduction in the distribution of a near asymptotic nature. It is believed that the disparity in the trend of change of D between the two samples could be attributed to their relative thermodynamic stability with the PXC 31399 grade being less stable.
Studies on the properties of glass fiber reinforced epoxy composites of DGEBA / epoxidized polyhydric alcohols with or without fortifier
Authors: Patel Rasmika H. , Patel Ranjan G.
Published: April 2003

Differential scanning calorimetry (DSC) technique was used to study the curing reaction of diglycidyl ether of bisphenol A (DGEBA) resin and different di‐ and trifunctional polyhydric alcohols with phthalic anhydride as curing agent and triethylamine as catalyst with or without fortifier. The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied as well. Activation energies of curing reactions range within 75.1 to 88.3 kJ mol−1. The cured products have good thermal stability; the composites have good mechanical strength, electrical insulation properties and chemical resistance. 36 to 53% improvement in flexural strength has been observed when fortifier was added to the DGEBA‐diluent systems.
Study of multicomponent complexes between polycarboxylic acid, transition metal ions and non‐ionic polymers
Authors: Chatterjee S. K. , Khan A. M. , Ghosh Sudipta , Yadav D.
Published: April 2003

Multicompoent complexes of a typical polyelectrolyte like poly(acrylic acid) (PAA) have been prepared by incorporating transition metal ions (e. g. Cu(ll) and Ni(ll)) and non‐ionic polymers (e. g. PVP, PEO) in the polyelectrolyte chain in a definite sequence. The formation of these complexes has been studied by several techniques, such as viscometry, potentiometry, conductometry, and IR spectroscopy. A scheme is suggested to explain the mode of formation of such complexes.
Propriétés électriques et adhésion aux interfaces polypropylène greffé‐aluminium
Authors: Lavielle Lisette , Prévot Jean‐Louis , Schultz Jacques
Published: April 2003

L'étude des caractéristiques intensité‐potentiel en courant continu pour des assemblages films de polypropylènes greffés‐aluminium permet de proposer un modèle électrique de I'interface polymère‐métal, associant une barrière de Schottky constante à une charge d'espace modulée selon le niveau d'adhésion. Cette charge d'espace est liée à l'afflux des groupements carboxyliques greffés sur le polypropylène vers la surface de l'aluminium. La présence d'une interphase dans l'adhésion entre polyoléfine et métal est ainsi prise en compte dans les mesures électriques.
Termination reaction in the chain oxidation of caprolactam
Authors: Lánská Božena , Makarov Genadii G. , Šbenda Jan
Published: April 2003

The oxidation of caprolactam initiated with 0.008‐0.82 mol/kg 1,1′‐azo‐di(cyclohexane carbonitrile) was studied in the temperature range 80–98°C. At the conversion lower than 3%, caprolactam hydroperoxide, adipimide, and hydrogen peroxide were determined in the oxidation products. Depending on the initiator concentration, the kinetic chain length of oxidation ranged between 3 and 30. The formation rate of hydrogen peroxide was equal to one half of the rate of initiation reaction, i. e. to one half of the rate of bimolecular termination in the steady state. It may be assumed that hydrogen peroxide is formed by the bimolecular termination reaction. This is in agreement with the fact that hydrogen peroxide was not found in the thermally initiated oxidation of caprolactam which proceeded with the kinetic chain length more than 300. Another product of the bimolecular termination reaction of caprolactam peroxy radicals is adipimide, which is also formed by their monomolecular decomposition.