bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and hydrolytic stability of model poly(ester urethane ureas)
Authors: Fambri Luca , Penati Amabile , Kolarik Jan
Published: April 2003

Hydrolysis of poly(ester urethane ureas) (PURUs) is a complex phenomenon which impedes the analysis of the relationships between their composition and hydrolytic stability. Hydrolytic stability of PURUs decreases due to rising (i) polyol acidity, (ii) content of ester groups, (iii) flexibility and (iv) hydrophilicity of the backbones; molar mass of polyols does not seem to have any appreciable effect on it. Negative influence of ether groups (which have better hydrolytic stability than ester groups) is probably linked to the increase in the backbone flexibility and, consequently, to easier access of water molecules to ester groups. Positive effect of aromatic rings in polyols can be ascribed to enhanced rigidity of the backbones as well as to increased hydrolytic stability of adjacent ester groups due to the resonance effect. It can be presumed that the mentioned effects will superpose and simultaneously predestine the resulting hydrolytic resistance. Considering the observed tendencies, it is possible to qualitatively predict the trends how the hydrolytic stability will respond to changes in PURUs composition.
Curing of unsaturated polyester resins with low exotherm peak
Authors: Penczek Piotr , Rudnik Ewa , Arczewska Bogumiła , Ostrysz Ryszard
Published: April 2003

The curing behavior of an unsaturated polyester resin with low exotherm peak was studied by a standard procedure and by differential scanning calorimetry (DSC). A copper salt and α‐methylstyrene were used as the polymerization retarders. The influence of the retarders on the exotherm peak temperature, gelation time, exothermic heat and the polymerization kinetics was investigated.
Obtention de composites fibres de verre‐polyesters par voie photochimique
Authors: Medenouvo F. , Fouassier J. P.
Published: April 2003

L'élaboration des fibres de verre renforcées par des matériaux composites à base de polyester/styrène par l'utilisation d'un procédé photochimique est présentée ainsi que le choix d'un système photoamorceur efficace capable d'initier la réaction de polymérisation. Les propriétés mécaniques des laminates ainsi traités sont similaires à ceux obtenus par l'utilisation d'un processus conventionnel. L'efficacité du mélange de photosensibilisateurs, photoamorceurs et additifs est discutée.
Photooxidation of poly(vinyl chloride) at 254 nm in the absence and presence of phthalate plasticizers
Authors: Denizligil S. , Schnabel W.
Published: April 2003

Irradiation of neat PVC at λinc = 254 nm under air induces the formation of conjugated double bonds, (CHCH)n (quantum yield ϕ ≈︁ 1.6 · 10−4 for n = 3). Simultaneously, CCl bonds are split (ϕ ≈︁ 8 · 10−2). With the aid of FTIR spectroscopy the following oxidation products were detected: OH, CHCHC(O), CHClCH2C(O)OH, CHClCH2C(O)H, CHClC(O)CHCl, CHClC(O)Cl. Irradiation of PVC plasticized with about 42 wt.‐% phthalate results in similar chemical changes. However, to some extent the chemical alterations are due to an indirect radiation effect. PVC, isolated from plasticizer after irradiation, was found to contain phthalate fragments attached to the polymer. Moreover, in plasticized PVC the formation of carbonyl groups is enhanced as was evidenced regarding the generation of CHCIC(O)CHCl groups. On the other hand, cleavage of CCl bonds and intermolecular crosslinking is retarded by phthalates. The exposure gel doses for unplasticized and plasticized PVC are 3 · 10−5 and 2 · 10−4 Einstein cm−2, respectively.
Elastomeric properties of ethylene/propylene copolymers prepared by zirconocene/methylaluminoxane catalysts
Authors: Banzi Viviano , Angiolini Luigi , Caretti Daniele , Carlini Carlo
Published: April 2003

Ethylene/propylene copolymers (EPM) have been prepared by a liquid propylene suspension process, using homogeneous catalysts based on nonbridged zirconocenes and methylaluminoxane (MAO). When bis(η5‐cyclopentadienyl)zirconium dichloride (Cp2ZrCl2), bis(η5‐cyclopentadienyl) dimethyl zirconium (Cp2ZrMe2) and bis(η5‐cyclopentadienyl), dibenzyl zirconium (Cp2ZrBz2) were used as catalyst components, EPM having low average molecular weight (MW) were in general obtained in low yield. On the contrary, a very large improvement of productivity and MW was observed when bis(η5‐indenyl)zirconium dichloride (Ind2ZrCl2) and bis(η5‐indenyl) dimethyl zirconium (Ind2ZrMe2) as well as bis(η5‐tetrahydroindenyl)zirconium dichloride [(IndH4)2ZrCI2] were employed in combination with MAO. In particular, this last catalytic system allowed one to obtain EPM with a narrower distribution of MW in addition to the above characteristics. Better performances, in terms of rheological and elastomeric properties, were also found for the crude and vulcanized samples prepared by (IndH4)2ZrCl2/MAO catalyst.
Inner surface and void system of regenerated cellulose fibers
Authors: Schurz Josef , Lenz Jürgen , Wrentschur Erich
Published: April 2003

Both the inner surface and the void system of different cellulose regenerate fibers are investigated with X‐ray small angle scattering. Thereby it turns out that all fibers have a void system of 0.01 to 0.1% (volume fraction 10−4–10−3). However, the amount of the void system has little influence on the mechanical properties. Rather, it is the shape of the voids and their orientation which proves essential. It is found that elongated voids, probably well oriented, are responsible for superior mechanical properties. This explains also improved textile properties of lyocell fibers of the NMMO type.
Reaction calorimetric investigation of the ring‐opening polymerization of ε‐caprolactone
Authors: Rafler Gerald , Bonatz Eckhard
Published: April 2003

The ring‐opening polymerization of ε‐caprolactone was investigated by means of the Mettler RC1 reaction calorimeter. In the range of small and medium monomer conversions this method can successfully be used for the determination of the course of the bulk polymerizations. The experimental results obtained by calorimetric and gravimetric method, respectively, are compared and the course of the polymerization is discussed in dependence on the reaction parameters (initiator, temperature).
Comparative studies of chemical kinetics of an epoxy‐amine system
Authors: Eloundou Jean Pascal , Feve Michel , Harran Daniel , Pascault Jean Pierre
Published: April 2003

Chemical reaction kinetics of an aliphatic diepoxy‐diamine system (DGEBD/4D) has been studied between 50°C and 95°C by two different calorimetric techniques; DSC in isothermal conditions on the one hand, conservation in thermostated tubes with successive extractions of samples studied by DSC in the dynamic temperature mode on the other hand.

Experiments show that the kinetics determined by isothermal DSC are systematically faster than those obtained with the other technique, this advance starting during the initial phase of the reaction. We show that this gap comes from the mass difference between the samples used in the two techniques, and can be explained by two different reasons. On the one hand, there appears a delay in the attainment of the thermal equilibrium at the beginning of the kinetics in the thermostated tubes, the samples having a greater mass. On the other hand, experiments have shown that there is a catalytic effect caused by the contact of reactive system with air (probably due to the action of atmospheric water). The area/volume ratio of samples being greater for samples studied by isothermal DSC, the catalytic effect is favoured to a greater extent in the case of this technique, which induces a faster rate of reaction at the beginning of the kinetics.

So, as the kinetic curves x = f(t) have different forms, they are described by different kinetic models. The Spacek‐model adequately describes the kinetic curves determined by isothermal DSC, with exponent values p = 1.20 and q = 0.45. The curves obtained by the technique of conservation in thermostated tubes are well described by the second order autocatalytic model, the ratio of the reactivities of primary and secondary amines having the value n = 1.1.

Furthermore the Tg variation curve with the extent of reaction in the thermostated tubes agrees very well with the equation proposed by Pascault and Williams.
Kinetic study on depolymerization by glycolysis of poly(ethylene terephthalate) with bisphenol A
Authors: Wang Ding‐Chang , Chen Liu‐Wang , Chiu Wen‐Yen
Published: April 2003

Glycolysis of poly(ethylene terephthalate) with bisphenol A at high temperature (190°C–230°C) was carried out in an autoclave reactor. Kinetic study on depolymerization of glycolysis was conducted. The reaction temperature and the ratio of bisphenol A to poly(ethylene terephthalate) played the key roles on the reaction rate and the extent of glycolysis. For describing the kinetic behavior properly, a mechanism consisting of six principle equilibrium reactions was proposed. Based on this mechanism, the kinetic parameters were obtained through the Runge‐Kutta numerical integration. Excellent agreements between the calculated values and the experimental data were achieved, thus verified the appropriateness of the proposed mechanism.
Surface modification of a polypropylene film by microwave plasma and the adhesion of a vacuum‐deposited aluminium layer
Authors: Garby L. , Chabert B. , Sage D. , Soulier J. P.
Published: April 2003

In order to improve the adhesion properties of polypropylene on a thin aluminium layer deposited under vacuum, a superficial modification of the polymer has been carried out by exposing the polymer surface to a microwave plasma from gas of different nature and composition.

The concentration of the present species in the sample proximity (downstream) has been measured by emission spectroscopy.

Superficial polymer modifications have been analysed by ESCA and by measuring contact angles with polar and apolar liquids. The adhesion measurements have been performed by pull‐off tests.

The wettability increase has been attributed to the creation of a very thin superficial layer which is partially soluble in methanol and includes carboxylic and ethylenic functions being observed by ESCA.

Wettability and adhesion depend on the composition of the gas mixture used. They increase with the atomic oxygen quantities which are created in the discharge and carried away in post‐discharge by the gas flow. A relationship has been established between the tensile stress values obtained by the pull‐off test and the polar interaction values measured during dewetting.
Effects of reactive diluents on mechanical and physical properties of a UV curable acrylated urethane prepolymer
Authors: Yildiz Emel , Güçlü Hande , Yildirim Hüseyin , Kuyulu Abdülkadir , Güngör Attila
Published: April 2003

In this study, the dependence of the mechanical properties of a UV curable acrylated urethane on reactive diluent types and their amounts was investigated. The acrylated urethane prepolymer was synthesized from isophorone diisocyanate (IPDI), an aliphatic diisocyanate, and polypropylene glycol monomethacrylate (PPGMMA) by stepwise addition reaction. UV sensitive mixtures containing N‐vinylpyrrolidinone (NVP), thiodiethylene glycol diacrylate (TDGDA) and isobornyl acrylate (IBoA) as reactive diluents were irradiated by UV light. An increase in reactive diluent content, either TDGDA or IBoA, caused an increase in tensile strength and a decrease in elongation values. In contrast, above a certain concentration a decrease in tensil strength was observed when NVP was used as reactive diluent.

The water absorption capacities of the UV curable acrylated urethane films were observed to depend on type and amount of reactive diluent that was used. Thermooxidative properties of the films were also improved by incorporation of reactive diluents into formulations.
Thermolysis of poly(diaryl diazosulfide)s
Authors: Nuyken Oskar , Lang Armin
Published: April 2003

Poly(diaryl diazosulfide)s and model diaryl diazosulfides of the general structure aryl‐NNS‐aryl' are tested for their thermostability. Thermolysis in solution is followed by means of UV spectroscopy. At the beginning of the decay most model diazosulfides follow first‐order kinetics, but show an acceleration of the decay rate in the further course of the thermolysis. In contrast to the models the decomposition of the corresponding polymers cannot be described by first‐order kinetics, except one example (P 1).

Thermogravimetry studies show weight losses of 8–12% in the range between 80 and 150°C depending on the structure of the models and polymeric diazosulfides. These values correspond with the content of azo function in these compounds, therefore it is assumed that nitrogen is split off under these reaction conditions.
Studies of polyimide/copper interface and its improvement by a two‐component primer
Authors: Dong Jian , Ji Gending , Xue Gi
Published: April 2003

The inhibition of the imidization of polyamic acid, a precursor of polyimide, in the presence of Cu, was confirmed by the incorporation of Cu2+ ions in polyamic acid films. It was found that the imidization reaction was incomplete below 300°C but decomposition took place when heating above 300°C. Pretreating the Cu surface with a two‐component primer solution containing polybenzimidazole and 2‐mercaptobenzimidazole can make the imidization proceed without retardation and avoid the decomposition above 300°C. By choosing appropriate surface treatment systems, one can achieve the improvement of adhesion between PI and Cu substrate.
Syntheses, morphology and dynamic mechanical properties of AB crosslinked polymers based on vinyl‐terminated polyurethanes/allyl novolac resin
Authors: Chiang Wen‐Yen , Chang Dong‐Meau
Published: April 2003

Vinyl‐terminated polyurethane (VTPU) was prepared from the PU prepolymer and methacrylamide. The prepolymers were prepared by reacting 4,4′‐diphenylmethane diisocyanate (MDI) with poly(tetramethylene oxide) (PTMO), whose molecular weight is M̄n = 600–700 (this polymer is called VTU1) and M̄n = 1900–2100 (VTU2), respectively. The AB crosslinked polymers (ABCPs) were synthesized from VTPU and allyl novolac resin, synthesized by substituting the hydroxy group of a phenolic resin with the allyl group. For these ABCPs, the phenomena of phase mixing was investigated and confirmed through dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The tensile strength of these ABCPs were improved and accorded with their structures and viscoelastic properties and morphology.
Polarization characteristics of poly(vinyl alcohol) films containing metal iodide
Authors: Yosomiya Takatoshi , Suzuki Yosuke , Yosomiya Ryutoku
Published: April 2003

The polarization properties of iodine complex layer deposited by oxidation of poly(vinyl alcohol) (PVA) containing metal iodide were investigated. Heat‐resistant polarizing films with high polarization efficiency were produced by oxidizing and stretching the PVA containing metal iodide. The results indicate that i) the polarization efficiency of a polarizing film prepared by oxidation of a PVA film containing 1 mmol or more of potassium iodide (KI)/g PVA at 0°C for 120 s in a 10 wt.‐% aqueous solution of H2O2 and a degree of stretching of 400% is high, ii) the heat resistance of the polarizing film in this experiment is higher than that of a filter prepared from a commercial PVA film.
Modified styrene‐diene‐styrene triblock copolymers for oxygen permeation
Authors: Yang Jen‐Ming , Hsiue Ging‐Ho
Published: April 2003

The grafting of vinylpyridine (VP) or 1‐vinylimidazole (VIm) onto styrene‐diene‐styrene triblock copolymer (polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) and polystyrene‐block‐polyisoprene‐block‐polystyrene (SIS)) by radiation‐induced graft copolymerization was studied. The cohesive properties of modified styrene‐diene‐styrene copolymers were calculated according to the group contribution method of Fedors. The changes of properties of modified styrene‐diene‐styrene copolymers reduced the gas permeability of oxygen and nitrogen through copolymer membranes, but increased the O2/N2 selectivity. The morphology of polymeric complexed membranes, which were prepared by complexing (N,N′‐disalicylidene ethylenediamine) cobalt(II) (CoS) with modified SIS and SBS, were studied by means of transmission electron microscopy and optical polarizing microscopy. It was found that the gas permeability was related to the morphological structure of modified styrene‐diene‐styrene block copolymer.
Emulsion polymerization of butyl acrylate induced by sodium lauryl sulfate/hydroxymethane sulfinate
Authors: Wang Cheng Chien , Kuo Jen Feng , Chen Chuh Yung
Published: April 2003

Hydroxymethane sulfinate (sodium formaldehyde sulfoxylate, SFS) along with sodium lauryl sulfate (SLS) was used to induce the aqueous polymerization of n‐butyl acrylate (n‐BA). The reaction rate, molecular weights and latex stability with those two compounds were found to be promising. However, the polymerization involved a significantly limited conversion and broad dispersity in molecular weights and particle sizes. The polymerization behavior, depending on factors such as the concentrations of SFS, SLS and n‐BA was different from that of traditional emulsion polymerizations. The rate dependence on the reaction temperature was described well by the Arrhenius equation, and the overall activation energy of polymerization thus obtained was 43 kJ/mol, which is close to that of redox‐induced polymerizations.
Synthesis and characterization of low‐viscosity fluoropolyether‐based segmented oligomers
Authors: Scicchitano Massimo , Turri Stefano , Tonelli Claudio
Published: April 2003

Six oligomeric polyols having a common perfluoropolyether chain end‐capped by different hydrogenated segments containing hydroxylic groups were synthesized and their properties described. The general scheme for the synthesis of these polyols involved the etherification of the fluoropolyether diol precursor (ZDOL) with epoxides or dibromoalkanes. The former reaction gave directly the polyolic derivatives, while the latter yielded the fluorinated dibromoderivative which could be converted to polyols through the reaction with malonate and final reduction.

The viscosity of these oligomers was measured and its dependence on temperature, solvent concentration and hydroxylic end‐groups content was established. The exceptionally low Tg and viscosity together with the good miscibility with common solvents make these polyols very interesting as “resins” suitable for high‐solid coatings.
Increasing of the adhesive properties of poly(propylene) by surface modification
Authors: Novák Igor
Published: April 2003

The applied surface modification methods aim at an increase of the hydrophilicity and the free surface energy (FSE) of isotactic poly(propylene) (iPP).

It was shown that for this purpose it is possible to use UV irradiation during 1–2 min, depending on the distance of the source of irradiation from the polymer surface [50, resp. 100 mm]. By the simultaneous effect of phosphorus trichloride (PCl3) and UV irradiation on the polymer surface the FSE was increased by 29% compared to the unmodified polymer and the mechanical work of adhesion was six times the original value. It was found that the application of strong oxidizing agents, such as potassium permanganate (PPM) and ammonium peroxodisulfate (APS), resulted in an increase of the FSE of iPP by 16 to 19%. The efficiency of the modification depends on the time of the modification by aqueous solutions of the oxidizers, as well as on the concentration of the solution. The FSE of iPP modified by UV irradiation does not change with the time after the modification.
Investigation of primers reducing the pink‐ring formation in multilayer printed circuit boards
Authors: Hong S. G. , Wang T. C. , Hong C. M.
Published: April 2003

A rapid and easy screening test was applied to assess the capability of various formulated primers to reduce the defect of pink rings in multilayer printed circuit boards. The mixtures of silanes with multifunctional silanol groups (crosslinkers) and 3‐glycidoxypropyl‐trimethoxysilane

Systematic name: 3‐(2,3‐Epoxypropoxy)propyl‐trimethoxysilane.

(referred to as silane C) or N‐(2‐aminoethyl)‐3‐aminopropyl‐trimethoxysilane

Systematic name: 3‐[N‐2‐aminoethyl]aminopropyl‐trimethoxysilane.

(silane B) were proved to be effective in reducing the pink rings. The performance of the mixed silanes using silane A and crosslinkers with aromatic groups were better than other formulated primers which was partly attributed to less amounts of hydrophilic groups and better integrity in the primer films. A developed primer consisting of siloxane compounds had the best performance. The online test confirmed the results from the screening test and demonstrated the feasibility of the designed screening test in assessing the performance of primers. The results of FTIR spectroscopy and thermogravimetric analyses confirmed that the effective primers coated on the copper oxides could improve the curing reaction and the thermal oxidative stability of the epoxy/CuO system.
Preparation and characterization of polymer dispersed liquid crystal films using photosensitive polymers
Authors: Liu Jui‐Hsiang , Chen Ming‐Zeng , Wang Yu‐Fang
Published: April 2003

4‐Butyl‐N‐(4‐methoxybenzylidene)aniline (MBBA) and 4‐butyl‐N‐(4‐ethoxybenzylidene)aniline (EBBA) liquid crystals were synthesized. To investigate the applications of hydrophilic monomers and polymers on the field of polymer dispersed liquid crystal (PDLC) films, 2‐hydroxyethyl methacrylate (HEMA) and acrylic acid (Aa) were selected as monomers for the polymer matrix. To prepare the PDLC films, MBBA, EBBA, and commercial liquid crystals ZLI‐2444, 2452, 2459 and BDH‐E7 were mixed with HEMA, Aa and photosensitive materials and then irradiated by UV light. The electrooptical behavior and the microstructure of the PDLC films were investigated by He‐Ne laser and scanning electron microscopy (SEM), respectively. The effects of UV‐light irradiation and monomer ratio on the electrooptical behavior of PDLC films, and the reproducibility and storage stability of the PDLC films were investigated.
Dispersion polymerization of styrene and methyl methacrylate initiated by poly(oxyethylene) macromonomeric azoinitiators
Authors: Yildiz Ufuk , Hazer Baki , Capek Ignác
Published: April 2003

Macromonomeric poly(oxyethylene) azoinitiators (macroinimers) MIM‐400 and MIM‐1500 were synthesized and characterized by IR and NMR spectroscopy and DSC techniques. The dispersion polymerizations of styrene and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimers (MIM‐400 and MIM‐1500) in water/ethanol were investigated at 60°C. The rate of polymerization was found to increase with increasing concentration of MIM and the increase was more pronounced in the styrene system. In the range of medium conversions the rate of polymerization was found to be proportional to the 1.7th and 1.6th power of [MIM‐400] and [MIM‐1500] for MMA and to the 2.5th power of [MIM‐400] for styrene, respectively.
Grafting fast blue BB onto maleated EPR using reactive extrusion
Authors: Maier Christian , Lambla Morand
Published: April 2003

In order to create a tracer to be used in the determination of residence time distributions, Fast Blue BB dye was grafted onto a maleated ethylene‐propylene rubber (EPRMA). The dye included a phenylamine group, which was reacted with the cyclic anhydride group (CA) on the EPRMA. Reasonably high conversions were obtained in a batch mixer within a short amount of time (less than 10 min). The reaction was then conducted on a co‐rotating self‐wiping twin‐screw extruder, where the dye had to be diluted in 1‐methyl‐2‐pyrrolidone in order to be injected. Although ideal from the point of a carrier medium for the injection and devolatilization, it tended to interfere in the equilibrium relationship between the CA group and its hydrolized form, dicarboxylic acid, and thus in the amidification. Optimizing the screw geometry involved moving the melt seal upstream so that the devolatilization could be performed as soon after the injection as possible.
Differentialkalorimetrische untersuchungen an chloriertem polyethylen und chloriertem polyvinylchlorid
Authors: Hößelbarth Bernd
Published: April 2003

Durch Chlorieren in Lösung hergestelltes Polyethylen (PE‐C) zeigt im amorphen Bereich (Chlorgehalt ≥ 30 Gew.‐%) eine kontinuierliche Erhöhung der Glastemperatur Tg mit steigendem Chlorgehalt. Diese Tg‐Chlorgehalt‐Funktion wurde verglichen mit der Tg‐Chlorgehalt‐Funktion des PVC‐C. Es wurde festgestellt, daß die Δcp‐Werte, gemessen bei Tg, in Abhängigkeit vom Chlorgehalt ein Maximum aufweisen, und zwar bei 50 Gew.‐% Chlor für PE‐C und bei 60 Gew.‐% Chlor für PVC‐C.
Synthesis and characterization of copolymers from acrylic and methacrylic acid with 2‐methylaziridine by spontaneous copolymerization
Authors: Rivas B. L. , Pizarro G. del C. , Tagle L. H. , Radic D.
Published: April 2003

2‐Methylaziridine (MAz) as a nucleophilic monomer and acrylic acid (AA) and methacrylic acid (MA), respectively, as electrophilic monomers were copolymerized in the absence of initiator at various feed ratios. Copolymers were characterized by elemental analysis, FT‐IR and 1H‐NMR spectroscopy. The monomer reactivity ratios were determined by the Fineman‐Ross and Kelen‐Tüdős methods. Values of r1 and r2 were found to be less than unity for MAz‐AA, and MAz‐MA, corresponding to random copolymers with the tendency to the alternance. For all the copolymers the thermal decomposition with 10% weight loss is higher than 430 K. The reaction order for degradation of all copolymers was zero. The kinetic parameters of the decomposition were determined for all copolymers.
Are microencapsulated antioxidants a feasible technology?
Authors: Billingham N. C. , Garcia‐Trabajo P.
Published: April 2003

We consider the possibility of stabilising a polymer by using a low‐molecular‐weight, mobile and soluble antioxidant, trapped in a small volume fraction of encapsulating material so that it is released into the surrounding polymer to compensate for consumption or loss. Two models are discussed. In the “matrix” model, the additive is dissolved in an encapsulant and its release is controlled entirely by the diffusion coefficient in the encapsulant. In the “balloon” model, the pure additive is surrounded by a wall of encapsulant, through which it permeates into the surrounding polymer. Modelling of the two cases allows the required diffusion or permeation coefficients to be calculated for any chosen loss time. It is found that purely diffusion‐controlled loss would require improbably low diffusion coefficients, whereas the required permeabilities for balloon models are accessible. It is difficult to imagine a system for which the temperature coefficient of loss rate would be low enough to allow elevated temperature processing without loss of the additive.
Search for the sources of color in thermally aged, weathered and γ‐ray irradiated bisphenol a polycarbonate
Authors: Factor Arnold
Published: April 2003

Bisphenol A polycarbonate (BPA‐PC) is an important high performance engineering thermoplastic well known for its outstanding combination of toughness, transparency and heat resistance. These properties make it an idel material for demanding applications where it is exposed to external stresses such as elevated temperatures, ultraviolet light and γ‐ray sterilization. However, on extended exposure to these conditions, BPA‐PC slowly degrades, turning progressively more yellow, eventually leading to a decrease in its physical properties. Over the years, there has been numerous studies made to understand these degradative processes so as to better design more stable BPA‐PC formulations. In this paper, this chemistry is briefly reviewed along with more recent work in this area with a special emphasis on the efforts made to identifying the actual chemical species responsible for the observed yellow color and the chemistry responsible for their formation.
Heterogeneous photooxidation of solid polymers
Authors: Gardette Jean‐Luc
Published: April 2003

Photooxidation of polymer can undergo heterogeneous effects, a complication which impacts attempts to extrapolate artificial accelerated tests to natural outdoor exposures. The main cause of heterogeneous degradation results from oxygen diffusion‐limited effects. Several experimental techniques can be used to monitor macroscopic heterogeneous oxidation in polymers. These techniques are based on i.r. spectroscopy: micro FTi. r. spectroscopy permits to determine oxidation profiles in polymer materials till a resolution around 10 microns and photoacoustic (PAS) ‐FTi. r. spectroscopy is an interesting method for analyzing the oxidation of the surface layers.
Aspects of stabilization with phosphorous antioxidants in polymers
Authors: Haruna T.
Published: April 2003

As plastics are being used in a variety of applications, demands on a greater level of processing stability are increasing. Phosphites are noteworthy as effective processing stabilizer and the performance of phosphite antioxidants can be correlated to the chemical structure of phosphites. Cyclic phosphite esters derived from 2, 2′ methylene bis‐2, 4‐di‐tert‐butylphenol and some commercially available phosphites were submitted to comparative studies. Decomposition of cumene hydroperoxide, melt flow of polypropylene and consumption of additives after multiple extrusions were investigated to understand the activity of phosphites as process stabilizers in polypropylene.

This study suggests that phosphites play an important role in process stabilization when used in combination with sterically hindered phenols, and that the activity of phosphites may be predicted by their reactivity on hydroperoxide.
Pyrolysis with respect to recycling of polymer
Authors: Kaminsky W.
Published: April 2003

Most plastics are produced from oil and have a high potential as hydrocarbon sources for the chemical industry. Pyrolysis is a practicable way to pyrolyze mixed plastics. The fluidized bed pyrolysis has turned out to be particularly advantageous. 25 to 45 percent of product gas with a high heating value and 30 to 50 percent of an oil rich in aromatics, could be recovered. The oil is comparable to that of a mixture of light benzene and bituminous coal tar. Up to 60 percent of ethene and propene are produced by using mixed polyolefins as feedstock. Under appropriate conditions the pyrolysis could be successful on the market.
Degradative extrusion as a pretreating process for chemical recycling of plastics waste
Authors: Michaeli W. , Lackner V.
Published: April 2003

Chemical conversion processes can also be used for the recycling of plastics waste. The plastics, however, must be adapted to chemical recycling processes by liquefaction and dehalogenation. A reprocessing method for plastics waste has been developed, which pretreats these waste fractions by degradative extrusion. The polymers are cracked in an extruder under the influence of thermal and mechanical energy and with the introduction of degradation‐promoting additives. Decomposition products such as halogens are eliminated and recovered in a defined manner through degassing and also a sufficient reduction of the melt viscosity was carried out by molecular degradation.
New evaluating methods of environmental‐stress degradation and weathering for plastics and rubbers
Authors: Ohishi Fujio
Published: April 2003

Several new methods are proposed here for evaluating ESD (Environmental‐Stress Degradation) and weathering of plastics and rubbers. Conclusively, the new methods proposed proved to be applicable.
Recycling and restabilization of polymers for high quality applications. An Overview
Authors: Pfaendner R. , Herbst H. , Hoffmann K. , Sitek F.
Published: April 2003

Mechanical recycling of thermoplastics for high value applications is directly associated with restabilization. The state of the art of processing‐, long term heat‐ and light stabilization of recyclates in different polymers (e.g. PP, PP/EPDM, HDPE, LDPE, PS, PVC and various blends) with examples from packaging, distribution, automotive and construction industry is shown. Because of predamage and impurities, recyclates degrade faster and differently compared with virgin polymers and, therefore, specially designed stabilizer systems are required according to the previous damage, subsequent application and type of polymer. Recommendations for restabilization include combinations of phenolic antioxidants and phosphites as well as HALS compounds or “Recyclostab” stabilizer systems.
Photodegradation of UV absorbers: Kinetics and structural effects
Authors: Pickett James E. , Moore James E.
Published: April 2003

When poly(methyl methacrylate) films containing UV absorbers are exposed to UV light, the absorbers undergo photodegradation resulting in loss of absorbance. If the data extend for less than one half‐life, both zero and first order kinetic treatment give fairly linear fits, but the rate constants so derived are dependent on the initial absorbance of the films. When the zero order rate constants are corrected to account for the higher rate of degradation near the surface compared with the bulk that occurs in highly absorbing films, consistent “infinite absorption” zero order rate constants are derived. The inhomogeneous degradation is due to only the highly absorbed, higher energy light contributing significantly to the degradation. For the benzophenone and benzotriazole classes of absorber, at least 65% of the degradation is due to light with wavelengths < 350 nm. Structural variations generally caused only small differences in the rates of degradation of these classes of absorbers unless the substitutions disrupted the intramolecular hydrogen bonds that are critical for stability. If the hydrogen bond is weakened, the absorber is less stable.
Organophosphorus antioxidants action mechanisms and new trends
Authors: Schwetlick Klaus , Habicher Wolf D.
Published: April 2003

Phosphite and phosphonite esters can act as antioxidants by three basic mechanisms depending on their structure, the nature of the substrate to be stabilized and the reaction conditions. All phosph(on)ites are hydroperoxide‐decomposing secondary antioxidants. Their efficiency in hydroperoxide reduction decreases in the order phosphonites > alkylphosphites > arylphosphites > hindered arylphosphites. Five‐membered cyclic phosphites are capable of decomposing hydroperoxides catalytically due to the formation of acidic hydrogen phosphates by hydrolysis and peroxidolysis in the course of reaction. Hindered aryl phosphites can act as chain‐breaking primary antioxidants being substituted by alkoxyl radicals and releasing hindered aryloxyl radicals which terminate the radical chain oxidation. At ambient temperatures, the chain‐breaking antioxidant activity of aryl phosphites is lower than that of hindered phenols, because the rate of their reaction with peroxyl radicals and their stoichiometric inhibition factors are lower than those of phenols. In oxidizing media at medium temperatures, however, hydrolysis of aryl phosph(on)ites takes place giving hydrogen phosph(on)ites and phenols which are effective chain‐breaking antioxidants.

2,2,6,6‐Tetramethyl‐ and 1,2,2,6,6‐Pentamethylpiperidinyl phosphites and phosphonites (HALS‐phosph(on)ites) surpass many common phosphites, phenols and HALS compounds as stabilizers in the thermo‐ and photo‐oxidation of polymers. Their superior efficiency is probably due to an intramolecular synergistic action of the HALS and the phosph(on)ite moieties of their molecules.
Polymers from renewable resources, VI. Synthesis and characterization of thermosetting resins derived from cashewnut shell liquid/formaldehyde/substituted aromatic compounds
Authors: Sahoo S. K. , Swain S. K. , Mohapatra D. K. , Nayak P. L. , Lenka S.
Published: April 2003

A large number of resins have been synthesized by reacting cardanol, a constituent of cashewnut shell liquid, with formaldehyde and substituted aromatic compounds in the presence of acidic and basic catalysts. The resins have been characterized by IR spectra. They were shown to be selective ion exchangers for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behaviour of the resins has been studied and a plausible degradation mechanism has been suggested.
The role and utilization of tetrachlorosilane/ethanol reagent in the crosslinking of poly(p‐vinylacetophenone)
Authors: Abdelaal Magdy Y. , Elmorsy Saad S.
Published: April 2003

Polystyrene has been modified through its acetylation into poly(styrene‐co‐vinylacetophenone) in a good yield. The obtained copolymer was then treated with tetrachlorosilane/ethanol reagent leading to the formation of triphenylbenzene units, either as crosslinking nodes or as pendent groups, and silyloxy derivatives of the acetyl groups attached to the styrene units as well as some unreacted acetyl groups. The percentages of the composition of all products were determined as well as silicon content.
Diffusion von wasserdampf durch feinschichtharze
Authors: Seycek Otakar , Scherz Norbert
Published: April 2003

Als Modell für die Gelcoat‐ oder Topcoatschicht eines glasfaserverstärkten Laminates wurden dünne, planparallele Platten definierter Dicke aus zwei Gelcoatharztypen (Isophthalsäure‐Neopentylglykol‐ (UP) und Phenacrylat‐Harz (PHA) auf Basis von Bisphenol A) gegossen, und es wurde der Einfluß der Unterhärtung sowie der Harzverdünnung mit Styrol auf die Wasserdampfdurchlässigkeit dieser Platten untersucht. Die Harzverdünnung führt in beiden Fällen zu einem evidenten Anstieg der Permeationskoeffizienten P. Die Unterhärtung (Aushärtungsgrade um 97%) und anschließende Extraktion des nicht auspolymerisierten Styrols läßt beim UP die Permeabilität von Wasserdampf ebenfalls ansteigen, beim PHA wurde dagegen ein leichtes Sinken des Permeationskoeffizienten verzeichnet. Die Ergebnisse werden im Zusammenhang mit den Unterschieden in der Kinetik der Aushärtungsreaktion beider Harztypen diskutiert.
Mechanical behaviour of PS/PVC blends compatibilized with block‐graft copolymers based on poly(styrene‐block‐butadiene)
Authors: Braun D. , Fischer M.
Published: April 2003

Blends composed of polystyrene (PS) and polyvinylchloride (PVC) are incompatible due to unfavourable interactions. Consequently, their mechanical properties such as impact strength and elongation at break are only very poor. The key to successfully influence the properties of such heterogeneous blends lies in the control of the interface. High interface tensions and an insufficient phase adhesion often lead to coarse phase morphologies which are thermodynamically and kinetically unstable. However, with radically synthesized, tailor made block‐graft copolymers P(S‐b‐(B‐g‐CHMA, MMA)) based on a styrene/butadiene two‐block copolymer P(S‐b‐B) which are grafted with poly(cyclohexylmethacrylate) (PCHMA) or poly(methylmethacrylate) (PMMA), the phase morphology can be markedly refined and the blends surprisingly show ductile behaviour. Thus, the impact strength of so modified PS/PVC 1 : 1 blends is about ten times higher than in the unmodified case and is thereby similar to impact modified PS.

Electron microscopy (SEM, TEM) reveals that the modified PS/PVC blends owe their improved mechanical properties to the interface selectivity of the block‐graft copolymers and therefore to a superior phase adhesion.
Synthesis and characterization of poly(amideimide)s containing aliphatic diamine moieties
Authors: Yi Mi Hie , Jin Moon Young , Choi Kil‐Yeong
Published: April 2003

New poly(amideimide)s (PAI) containing aliphatic diamines as comonomers were synthesized by polycondensation of trimellitic anhydride chloride with mixed diamines. Preliminary results of copolymerization with various alicyclic diamines suggested that isophoronediamine (IPDA) is more preferable as a comonomer for PAI. The copolyamide imides with IPDA showed that IPDA is more rigid than mbisaminophenoxydiphenylsulfone

Systematic name: 4,4′‐Sulfonylbis(1,3‐phenylenoxy)dianiline.

(m‐BAPS) and 4,4′‐diaminodiphenyl ether (ODA), but less than m‐phenylenediamine (m‐PDA). And they showed good mechanical properties with 105 ∼ 118 MPa of tensile strength and Tg's were ranged 232 ∼ 301 °C depending on molecular weight and comonomers. The solubility was improved due to the aliphatic character of IPDA in the copolymers. Rheological properties were also improved compared with conventional PAI. The melt viscosity of the copolymers ranged 1.6 · 103 ∼ 2.1 · 103 Pa · s, thus, the reported PAIs may be considered to be new candidates for melt processable high‐performance polymer materials.
Rationelle stärkeacetat‐synthesen
Authors: Reinisch Gerhard , Radics Ute , Roatsch Birgit
Published: April 2003

Mit Kaliumcarbonat als Aktivator werden aus Hochamylosestärke (HAS) mit überschüssigem Acetanhydrid bei Reaktionszeiten von 1 – 2 h in hohen Ausbeuten Produkte mit hohen Durchschnittssubstitutionsgraden (DS) erhalten.

In N‐Methyl‐2‐pyrrolidon können HAS mit stöchiometrischen Mengen Acetanhydrid und mit nichtflüchtigen starken organischen Basen wie 4‐Dimethylaminopyridin oder 1,4‐Diazabicyclo[2.2.2]octan als Katalysatoren in Reaktionszeiten von weniger als 1 h und in hohen Ausbeuten zu Acetaten mit DS < 2 umgesetzt werden.
Triazine‐based polymers, 3. Synthesis and characterization of polyamines
Authors: Braun D. , Ghahary R. , Ziser T.
Published: April 2003

A series of 16 triazine‐based polymines was synthesized by interfacial polycondensation, using various dichlorotriazine derivatives and diamines as monomers. The effect of the reaction parameters temperature, reaction time, concentration of monomers, type of organic solvent and type of base on the reduced specific viscosity and yield of polyamines was investigated. Solubilities, glass transition temperatures and thermogravimetric data were determined. Dynamic‐mechanical thermal analyses of two polyamines are reported.
Steam‐exploded wheat straw fibers as reinforcing material for polypropylene‐based composites. Characterization and properties
Authors: Avella Maurizio , Bozzi Claudio , dell'Erba Ramiro , Focher Bonaventura , Marzetti Annamaria , Martuscelli Ezio
Published: April 2003

Composites of wheat straw fibers with polypropylene (iPP) and maleic anhydride modified polypropylene (iPPMA) were prepared.

Before being mixed with polypropylene matrices, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosic materials. Such changes are able to enhance the interactions with the thermoplastic matrix.

Compared with iPP, the modified matrix (iPPMA) has shown higher mechanical performances (tensile and impact behavior) and a remarkable decrease of water absorption, that is one of the main drawbacks of natural fiber composites.

Finally, the presence of covalent bonds between maleic anhydride and steam‐exploded (STEX) fibers, by means of an esterification reaction, produced during the melt‐mixing process, can explain the resulting good interfacial adhesion found in iPPMA‐based composities.
Determination of branching in polybutadienes, poly(1,3‐butadiene‐co‐1‐octene) and poly(1,3‐butadiene‐co‐1‐dodecene)
Authors: Mähner C. , Kaulbach R. , Lechner M. D. , Nordmeier E. H. , Gehrke K.
Published: April 2003

This paper deals with the determination of long‐chain branching in polybutadienes, poly(1,3‐butadiene‐co‐1‐octene), and poly(1,3‐butadiene‐co‐1‐dodecene). These polymers were synthesized by polymerization using a neodym and aluminium‐based catalyst system. Short‐chain branches were introduced by incorporating olefins into the polybutadienes, leading to an improvement of their mechanical properties. The polymers were examined by static and dynamic light scattering, viscosimetry, and gel permeation chromatography. These measurements yield the g‐, h‐, and gη‐factors. The olefin incorporation was performed to increase the degree of branching. But this could not be shown clearly. It is also possible that the degree of branching increases because the polymer molar mass or the width of polymer molar mass distribution (MMD) increases. Thus, branching due to the olefin incorporation may be simulated. To analyse the influence of olefines on the degree of branching more exactly, one would need polymers having identical molar mass and MMD. Moreover, it is possible, depending on whether octene and dodecene chains are long enough, that they can be detected by means of long‐chain branching (LCB) analysis. A decrease of the Lewis acid concentration in the catalyst system changes the MMD and the degree of branching. If the system contains two active centres the MMD is bimodal, whereas if there is only one active centre the MMD is unimodal. In addition, a reduction in Lewis acid concentration leads to an excess of Al(i‐But)3in the catalyst system. Since Al(i‐But)3is a carrier for branching reactions the degree of branching increases.
Radiation‐induced graft polymerization of vinyl monomers onto polyamide‐6
Authors: Kaur Inderjeet , Misra B. N. , Barsola Raghuvir
Published: April 2003

Radiation‐induced graft copolymerization of 4‐vinyl pyridine (VP) and a binary mixture of VP and acrylonitrile (AN) onto polyamide‐6 (PA6) fiber has been studied. Optimum reaction conditions leading to maximum percentage of grafting have been evaluated. The graft copolymers have been characterized by IR spectroscopy, thermogravimetric analysis and also by studying the dyeing behaviour of the grafted and ungrafted fiber. It has been observed that, although the thermal properties of fibers had changed upon grafting, the dyeing behaviour, with respect to the total dye uptake, did show only little improvement.
Synthesis and properties of chelate polymers of Cu(II), Ni(II), Co(II), Mn(II) and Zn(II) with a schiff's base of 5,5′‐methylene‐bis(3,3′‐dinitrosalicylaldehyde) with 1,6‐hexanediamine
Authors: Patel M. N. , Sutaria D. H. , Patel S. D.
Published: April 2003

The synthesis, characterization and coordination aspects of the title polymer ligands are reported. The polymeric chelates were prepared by polycondensations of transition metal ions (M) with a poly(Schiff's base) (L). The analytical data propose a (ML)n formula for the chelates. All the polychelates are stable and insoluble in common organic solvents. The geometry around the central metal ion in each chelate is proposed on the basis of measurements of magnetic susceptibilities and UV reflectance spectra. The ligand field splitting parameters 10 Dq, the interelectronic repulsion parameter B, the nephelauxetric parameter β and ligand field splitting energies (L.F.S.E.) have been calculated for Ni(II) and Co(II) chelates. All chelates are resistant to moderately concentrated acids and dilute alkalies at ambient temperature. They exhibit thermal stabilities to varying degrees. IR spectra show that the ligand usually coordinates via the carbonyl oxygen (C=O) and the phenolic OH with replacement of hydrogen by metal ions.
Air plasma treatment of polyacrylonitrile porous membrane
Authors: Bryjak Marek , Gancarz Irena , Krajciewicz Adam , Pigłowski Jacek
Published: April 2003

The effect of plasma treatment of porous polyacrylonitrile membranes is discussed. It is shown that air plasma increases the surface polarity at low‐energy treatment and gradually diminishes it when the energy is increased. When the plasma is set at energies of 12, 30 or 60 W, etching of polymers dominates. Pore diameters of the membranes increase and their distribution functions become broader. When plasma of higher energies (120 or 180 W) is used, the effect of changes of the pore distribution disappears. Membranes modified with plasma of 60, 120 or 180 W do not differ in their porous structure. A simple method of an evaluation of pore diameter distribution function is presented.
Verwendung von schwefelhaltigen salzen für die homogene sulfatierung von polysacchariden im system dimethylformamid/N2O4
Authors: Torgaschov Wadim I. , Gert Evgenij W. , Bildjukewitsch Alexander W. , Kaputskii Fjodor N.
Published: April 2003

Sulfatations of cellulose and of other types of polysaccharides by the salts of acids H2SnO2n+1 and H2SnO3n+1 in DMF/N2O4 medium have been carried out. Uniformly substituted biologically active sulfates of polysaccharides have been obtained.