bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling the kinetics of the precipitation polymerization of acrylic acid
Authors: Avela Arno , Poersch Hans‐Günter , Reichert Karl‐Heinz 
Published: April 2003

AbstractA kinetic model for the free‐radical precipitation polymerization of acrylic acid in toluene was developed and verified experimentally by using an isothermal reaction calorimeter. The model predicts the rate of polymerization accurately up to complete conversion in the temperature range of 40 to 60°C.
SEC on cellulose nitrate: DP‐Ve relationship and evaluation of different methods to determine the calibration parameters
Authors: Soubelet O. , Presta M. A. , Marx‐Figini M. 
Published: April 2003

AbstractThe calibration behaviour of the system cellulose nitrate‐μ‐Styragel‐THF has been studied using about 30 different calibration samples prepared by defined acid catalyzed degradation of cotton cellulose. The samples covered a range of DP between 150 < DP < 8000. It is shown that the DP‐Ve relationship is characterized by the existence of three subsequent stages. Consequently, two sources of errors in the DP‐Ve calibration must be taken into consideration. One refers to the methods as such to elaborate the calibration parameters, and the other one arises by neglecting that the DP‐Ve relationship involves 3 distinct stages. The extent of the two classes of errors in regard to the exactness of the determined molecular weight averages and molecular weight distributions is discussed.
The influence of sepiolite on the compatibility of semicrystalline polymer blends
Authors: Acosta José Luis , Herrero Consuelo R. , Morales Enrique 
Published: April 2003

AbstractMelting point depression analysis in polymer blends allows the determination of the polymer/polymer interaction parameter X23 of these systems. This work deals with the influence of a filler, like sepiolite, on the compatibility of two systems such as polyvinylidene fluoride/polymethylmethacrylate and polyvinylidene fluoride/polystyrene through the analysis of this parameter X23. The results obtained demonstrate the compatibilizing effect of sepiolite at high filler loadings.
Water‐Soluble polyamides as potential drug carriers. I. Poly(α,β‐D,L‐asparthydrazide‐CO‐D,L‐ornithine)
Authors: Meirim Maria G. , Neuse Eberhard W. , Parisi Frank 
Published: April 2003

AbstractThe polycondensation of d,l‐aspartic acid with Nδ‐phthaloyl‐l‐ornithine in phosphoric acid at 185°C gives rise to the formation, in 60 — 75% yield, of random copolymers of the poly(d,l‐succinimide‐co‐Nδ‐phthaloyl‐D,L‐ornithine) type 6 possessing inherent viscosities (DMF) in the range of 5 — 15 ml g−1. Copolyimides of the same compositions 6 and comparable chain lengths are obtained from aspartic acid and the copper chelate of the phthaloylornithine. Treatment of copolymers 6 with hydrazine hydrate in DMF leads to N‐deprotection and opening of the intrachain succinimide rings with formation of hydrazide side groups. The resultant polyamides are of the poly(α,β‐d,l‐asparthydrazide‐co‐d,l‐ornithine) type 7. Shorter reaction periods give incomplete hydrazinolytic ring opening, and the remaining succinimide units are cleaved hydrolytically during the subsequent aqueous workup, thereby transforming into aspartic acid units. The polyamides so formed possess the general poly(α,β‐d,l‐asparthydrazide‐co‐α,β‐d,l‐aspartic acid‐co‐d,l‐ornithine) structure 8 Both types 7 and 8 are soluble in water and, in this medium, give inherent viscosities of 5 — 14 ml g−1. The potential drug‐anchoring capabilities of these amine‐functionalized polyamides are demonstrated by coupling reactions with model carboxylic acids.
Antioxidants and stabilizers, 111. Regeneration mechanism of the antioxidant action of N‐isopropyl‐N′‐phenyl‐1,4‐phenylenediamine
Authors: Taimr Ludĕk , Prusíková Milus̆e , Pospís̆il Jan 
Published: April 2003

AbstractIn connection with the investigation of the mechanism of antioxidant action of antidegradants in hydrocarbon polymers under the conditions of a relative deficiency of oxygen, scavenging of a model alkyl (1‐cyano‐1‐methylethyl,R°) was studied with Nisopropyl‐N′‐phenyl‐1,4‐phenylenediamine (Ia)For abbreviations see p. 11.
and its oxidation product, i.e. Nisopropyl‐N′‐phenyl‐1,4‐benzoquinonediimine (IIa). While pure Ia and IIa do not react with the radical R° almost at all, their mixture is able to scavenge R° effectively. The reaction is further accelerated with acids. The alkyl R° combines with the antidegradant molecule in two ways, one of which leads to the substitution at the nitrogen atom between the aromatic rings, giving rise to VIa, while the other consists in the substitution of phenylene, leading to VIIIa. The product VIa is labile, and at vulcanization temperatures it readily splits off olefin in a neutral medium, being regenerated to Ia. In the presence of acids this reaction proceeds even at lower temperatures. In the other product, i.e. in VIIIa, the alkyl R° is bound firmly, but due to the presence of the nitrile group, VIIIa is readily cyclized by the effect of acids, and an indoline derivative X is formed. The formation of VIIIa is a model of the formation of an “unextractable fraction” of antidegradant Ia in the stabilization of hydrocarbon polymers. Investigations based on the isolation of reaction products bear at the same time evidence of the possibility of regeneration of an effective antioxidant in the stabilized substrate.
Wetterbeständigkeit von polymeren: Messung der photochemischen abbauprozesse und der schutzwirkung anorganischer pigmente mittels physikalischer untersuchungsmethoden
Authors: Kämpf G. 
Published: April 2003

AbstractThe 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

AbstractWhen 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

AbstractIsothermal 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

AbstractLow‐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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractLeather 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractSIS 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

AbstractA 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

AbstractDynamic 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

AbstractN,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.