bluuebunny/crossref_metadata_2025_split huggingface dataset:
Living polymerization of cyclic esters – a route to (bio)degradable polymers. Influence of chain transfer to polymer on livingness
Authors: Penczek Stanislaw , Szymanski Ryszard , Duda Andrzej , Baran Jolanta 
Published: October 2003

AbstractPolymerization of cyclic esters leads to (bio)degradable polymers of the increasing industrial importance. These polymerizations are of the living nature, although chain transfer to polymer with chain scission may cause deviations from the livingness and introduce structural differences (e.g. in end‐groups), important for physical properties. Two different systems are discussed. In the first one two living macromolecules react one with another and reproduce two living macromolecules, retaining the same reactivities and the same end‐groups. Polymerizations of ϵ‐caprolactone and lactide belong to this category. On the other hand, polymerization of cyclic carbonates proceeds with chain transfer, in which disproportionation of the living chains takes place: from two living macromolecules one “dead” and one “doubly active” can be formed. Conditions of retaining the livingness in terms of the ratios of the rate constants of transfer, reinitiation, and propagation are discussed.
Bioprocessing – no longer a field of dreams
Authors: Sawyer Daniel J. 
Published: October 2003

AbstractA Field of Dreams was a movie about baseball. The theme was “Build it and They Will Come.” Bioprocessing as an industry has been waiting for someone to step up to the plate and build a large business, based on the technology. The large business was necessary to bring about a revolution to move the Chemical and Plastics Industries towards a new business model, based on more sustainable practices. By providing a unique combination of properties in fiber and packaging applications, PLA was the obvious first choice for companies looking to make bioprocessing a commercial reality.
Microbial degradation of aliphatic polyesters
Authors: Tokiwa Yutaka , Jarerat Amnat 
Published: October 2003

AbstractPolyester‐degrading ability of actinomycetes obtained from culture collections was investigated by the formation of clear zones on polyester‐emulsified agar plates. Using 41 genera (43 strains) of actinomycetes with phylogenetic affiliations based on 16S rRNA sequences, poly(L‐lactide) (PLA)‐degraders were found to be limited to members of family Pseudonocardiaceae and related genera. On the other hand, poly(β‐hydroxybutyrate) (PHB)‐, polycaprolactone (PCL)‐, and poly(butylene succinate) (PBS)‐degraders were widely distributed in many families.
Trends in industrial polymer research
Authors: Warzelhan Volker , Brandstetter Franz 
Published: October 2003

AbstractIn the past decades a shift in paradigm took place in industrial polymer research for structural materials. Only a few new polymers based on new monomeric building blocks were developed. The main focus is now on tailoring improved “old polymers” with well‐defined structure and properties based on a set of low cost “old” monomers using controlled polymerization mechanisms.
Efficient and tailored polymerization of olefins and styrene by metallocene catalysts
Authors: Kaminsky Walter , Hopf Andreas , Arndt‐Rosenau Michael 
Published: October 2003

AbstractDifferent optimised new cs‐symmetric ansa zirconocenes were used for the homopolymerization of propene ‐ activated by methylaluminoxane (MAO) with an Al : Zr molar ratio of 2000. In a series of experiments, the polymerisation temperature was varied in a range from 0 to 60°C. The obtained syndiotactic polypropenes show highly isotacticities up to rrrr pentads of 98% and melting points of 150°C. Stereoselectivities are sensitive to the monomer concentration, showing decreasing syndiotacticities with decreasing propene concentration due to increasing amount of skipped insertion which is demonstrated for the zirconium catalyst.
Polyolefin: changing supply‐demand framework and new technology
Authors: Kitano Kissho , Sugawara Makoto , Matsuura Mitsuyuki 
Published: October 2003

AbstractPolyolefin industry is now under a remarkable change of international supply‐demand framework and its market is splitting into commodity and high performance products. It is getting more important for a material being harmless and comfortable, while the “life cycle cost”, which includes the cost during use and the recycle cost after use, is regarded as more important to evaluate a material. Those changes are accelerating the inter‐material penetration. Several examples of the material design and production technologies, which responded to the changing market needs and developed new applications of polyolefin, are discussed.
Grafting of polyolefins with maleic anhydride: alchemy or technology?
Authors: van Duin Martin 
Published: October 2003

AbstractNowadays, the process of maleic anhydride (MA) grafting and the application of MA‐grafted polyolefins are viewed as mature technologies. The chemistry and technology of modifying apolar polyolefins with the polar and reactive MA either in solution or in the melt were already explored as far back as the 1950s. Commercial applications exploit the improved adhesion of polyolefins to polar materials, both at the macroscopic scale and on the microscopic scale. However, it is hardly recognised that, from a scientific point of view, grafting has still a strong resemblance to alchemy. Both process and application technologies have been developed in a trial and error fashion. Only in the last decade the structure of MA‐grafted polyolefins has been elucidated and attempts to “look” inside the extruder during grafting were only recently successful. The first steps towards the development of sound chemical models are currently made. An overview will be given of the progress made in the various areas mentioned.
Novel copolymers via nitroxide mediated controlled free radical polymerization of vinyl chloride
Authors: Wannemacher Thomas , Braun Dietrich , Pfaendner Rudolf 
Published: October 2003

AbstractControlled free radical polymerization (CFRP) of vinyl chloride (VCM) and copolymerization with several comonomers have been studied in aqueous suspension. Therefore di‐tert‐butylnitroxide and three novel nitroxyl radicals were used as mediating agents. Copolymerization of VCM with styrene, partly combined with acrylonitrile, maleic acid anhydride and maleic acid imide as well as methyl methacrylate, n‐butyl methacrylate, butyl acrylate and butadiene have been achieved, demonstrating an efficient route for novel vinyl chloride copolymer architecture.
Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent system
Authors: Schut Jaap , Stamm Manfred , Dumon Michel , Galy Jocelyne , Gérard Jean‐François 
Published: October 2003

AbstractSyndiotactic polystyrene (sPS) is a new semi‐crystalline thermoplastic which is believed to fill the price‐performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290°C), an epoxy‐amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy‐amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic‐thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy‐amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy‐amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7‐9 min for low concentration blends, while it increases to 20‐45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions.
Controlled synthesis of block polyesters by reactive extrusion
Authors: Moad Graeme , Groth Andrew , O'Shea Michael S. , Rosalie Julian , Tozer Ramon D. , Peeters Gary 
Published: October 2003

AbstractThe synthesis of block copolyesters by combining transesterification resistant oligoesters with poly(ethylene terephthalate) is described. Critical factors in the synthesis include processing conditions (temperature), end groups and catalysts used in oligoester synthesis. It is necessary to achieve a balance between ease of incorporation/synthesis and transesterification resistance. The process is discussed with reference to poly(neopentyl isophthalate) as a representative transesterification resistant oligoester. The primary motivation for the work has been the development of higher barrier poly(ethylene terephthalate) useful for making monolayer beverage containers.
Synthesis and properties of poly(m‐carborane‐siloxane) elastomers
Authors: Patel Mogon , Swain Anthony C. , Skinner Anthony R. , Mallinson Leslie G. , Hayes Gerard F. 
Published: October 2003

AbstractOrganic boron polymers are of interest to AWE, and a significant improvement would be to make components from a single phase material that enables the boron content to be maximised and the elastomeric properties to be tuned to requirement. This paper is a summary of the work carried out towards the synthesis and characterisation of poly(m‐carborane‐siloxane) rubbers. These rubbers have been synthesised by the Ferric Chloride‐catalysed condensation reaction between dimethoxy‐m‐carborane terminated monomer and dichlorodimethylsilane. Phenyl modified and Phenyl‐vinyl modified variations have been synthesised in addition to the unmodified poly(m‐carborane‐siloxane) polymers. The unmodified poly(m‐carborane‐siloxane) shows some crystallinity but the modified versions are amorphous and have good elastomeric properties. Overall, the measured boron content is in close agreement to that expected from the repeat unit, suggesting the synthesised rubbers have been successfully prepared. It is also demonstrated that the carborane unit offers increased thermal stability and retention of ‘rubber‐like’ properties even after ageing at high temperature.
Impact modification of PA‐6 and PBT by epoxy‐functionalized rubbers
Authors: Lievana Emiliano , Karger‐Kocsis József 
Published: October 2003

AbstractGlycidylmethacrylate (GMA) grafted apolar (ethylene/propylene/diene ‐ EPDM) and polar (acrylonitrile/butadiene ‐ NBR) rubbers were melt blended with polyamide‐6 (PA‐6) and polybutylene terephthalate (PBT). The toughness of the blends containing 5, 10 and 50 wt.% epoxy functionalized rubbers was assessed by various methods (notched Charpy, perforation impact) as a function of temperature (T=23 and −40°C). The notched Charpy tests served to deduce the fracture toughness (Kc) and energy (Gc) data. It was established that EPDM‐g‐GMA is a slightly better impact modifier than is NBR‐g‐GMA albeit the latter polar rubber is more compatible with both matrices than the less polar EPDM‐g‐GMA. This finding was traced to the difference in the glass transition temperature (Tg of NBR is higher than that of EPDM) and to the dispersion of the epoxy functionalized rubbers.
Compatibilization of PA6/rubber blends by using an oxazoline functionalized rubber
Authors: Scaffalo R. , La Mantia F.P. , Bertani R. , Sassi A. 
Published: October 2003

AbstractThe compatibilization of blends of polyamide 6 with a nitrile butadiene rubber has been investigated. The procedure consists of two steps: modification of the nitrile groups of the rubber into oxazoline in the melt through condensation of ethanolamine with formation of a molecule of ammonia, followed by use of the modified rubber as a compatibilizing precursor which is melt mixed with the polyamide to produce the compatibilized blend. The modification reaction has been detected by NMR analysis and a rheological, mechanical and thermomechanical characterization has been carried out on the all the blends. The results indicate that the modification reaction occurs but the conversion of nitrile into oxazoline is relatively low. Use of the modified rubber in the preparation of binary polyamide/rubber blends, leads to an increase in viscosity, which is typical of compatibilized systems, and to enhanced tensile, impact and thermomechanical properties. These phenomena can be explained by the formation of in situ rubber/polyamide copolymers that act as compatibilizers, due to the reaction between oxazoline and the end groups of the polyamide. The presence of residual low molecular compounds, from the modification or from the purification of the rubber worsens all of the properties and inhibits the compatibilizing effect of the modified rubber.
Functionalization on polyamide complex with iodide: a review
Authors: Kawaguchi Akio , Tsurutani Naoki 
Published: October 2003

AbstractApplication with iodinated polyamide‐6 (iodine/PA‐6 complex) is introduced for modification of structure and functionality on the polyamide. Coordination between polyiodides (In− = 3, 5, ...) and the polyamide advances rapidly and drastically within polyiodide solutions even in bulky samples of the polyamide, and responsiveness in the complex with other molecules such as water is enhanced by coordination. Such response and variation of the structure of the complex can introduce novel functionality with other molecules or ions or salts into the polyamide or hydrophilic polymers.
Influence of processing method and components molecular structure on the phase behaviour of polyethylenes/dye blends
Authors: Pucci Andrea , Ruggeri Giacomo , Cardelli Camilla , Conti Giovanni 
Published: October 2003

AbstractThe phase dispersion of terthiophene alkyl derivatives on different polyethylene matrices was investigated. The PE affinity toward dichroic dyes with different structure, the effect of blending process and the influence of a polyolefinic compatibilizer on the homogeneity of host‐guest blends were comparatively investigated by calorimetry, DSC and SEM analyses. For these purposes, polyethylenes with different molecular weights and densities and EVAc were used as host matrices. The polymeric compatibilizer was prepared by radical functionalization of a commercial low density polyethylene. The dichroic nature of the guest phase allowed to perform UV‐Vis measurements in polarized light on oriented blend film samples. The dyes affinity toward PE is one of the key factor in obtaining oriented polyolefinic films with high optical performances for several applications.
Quantitative analysis of functional groups in HDPE powder by DRIFT spectroscopy
Authors: Földes Enikő , Szabó Zoltán , Janecska Ákos , Nagy Gábor , Pukánszky Béla 
Published: October 2003

AbstractFT‐IR spectra of ethylene homopolymers and ethylene/1‐hexene copolymers polymerized under different conditions were studied by transmission and diffuse reflection (DRIFT) spectroscopy. The absorbance spectra of film samples were compared with the DRIFT spectra of powders ground from the films. For determining the concentration of the methyl and unsaturated (vinyl, vinylidene and trans‐vinylene) groups of polyethylene powders the DRIFT spectra were calibrated by comparing the IR intensities of the corresponding bands measured by the two methods. The results proved that the effect of differences in scattering of the polymer powder originating from the irregularity of the top surface, as well as the size and shape of the particles can be eliminated by the use of a proper internal standard. Linear correlation was established between the logarithms of the normalized intensities measured in absorbance and Kubelka‐Munk units. In the case of polyethylene the selection of the internal reference band affects significantly the accuracy of the calibration due to the difference in the refractive indices of the crystalline and amorphous phases.
Reactive compatibilization of recycled low density polyethylene/butadiene rubber blends during dynamic vulcanization
Authors: Fainleib Alexander , Grigoryeva Olga , Starostenko Olga , Danilenko Inna , Bardash Lubov 
Published: October 2003

AbstractFor reactive compatibilization of the recycled LDPE with butadiene rubber (BR) an equal quantity of few couples of reactive polyethylene copolymer/reactive polybutadiene (1/1) were introduced into the corresponding phases before the dynamic vulcanization. The LDPE/BR thermoplastic dynamic vulcanizates (TDVs) produced using the poly(ethylene‐co‐acrylic acid), PE‐AA/polybutadiene terminated with isocyanate groups, PB‐NCO compatibilizing couple with different ratio of functional groups have demonstrated the best mechanical properties and have been characterized by X‐Ray analysis and DMTA measurements. For all of systems studied the increasing components compatibility due to the formation of the essential interface layer have been observed. The PB‐NCO modifier participates in two processes: it is co‐vulcanised with BR in rubber phase and reacts in the interface with the PE‐AA dissolved in LDPE. The amorphous phase of LDPE is dissolved by rubber phase, i.e. the morphology with dual phase continuity is formed that provides an improvement of mechanical characteristics of material obtained. The best combination of mechanical characteristics was obtained for LDPE(PE‐AA)/BR(PB‐NCO), PB‐NCO=7.5 wt.% per PB, COOH/NCO=1/1. The tensile strength and an elongation at break for these blends were 3.9 MPa and 353% and for the basic non‐compatibilized blend 3.2 MPa and 217%, relatively.
Creep relaxation and stress relaxation of PS‐HI/SEBS blends
Authors: Rek Vesna , Holjevac Grgurić Tamara , Jelčić Želimir 
Published: October 2003

AbstractFor the selection of the polymer materials and polymer blends for various fields of applications the stability of material under constant deformation and constant load are very important. In this paper, the copolymers high‐impact polystyrene, PS‐HI, styrene‐ethylene/buthylene‐styrene block copolymer, SEBS, and their blends PS‐HI/SEBS were investigated. The investigations were done by DMA analysis. The secondary viscoelastic functions, creep, creep modulus, stress and flexural relaxation modulus were investigated in creep and stress relaxation experiment at temperatures 25, 35, 45, 55 and 65°C during 1 h. The master curves were created by time‐temperature correspondence principle, TTC. The correlation of the secondary viscoelastic functions with time, temperature and content of the hard, PS, phase was discussed.
Processing and dynamic mechanical properties of PS‐HI/SEBS blends
Authors: Rek Vesna , Holjevac Grgurić Tamara , Jelčić Želimir 
Published: October 2003

AbstractThermoplastic elastomers have been successfully used as impact modifiers for thermoplastics. Dynamic mechanical properties and phase transitions are very important for their application. In this paper, the copolymers high‐impact polystyrene, PS‐HI, styrene‐ethylene/butylene‐styrene block copolymer, SEBS, and their blends PS‐HI/SEBS were investigated. Rheological behaviour of those samples during processing was followed by measuring the torque vs. time in the extruder Haake Record 90. The investigations were done by DMA analysis. The primary viscoelastic functions, the storage modulus, E` the loss modulus, Eˇ, and loss tangent, tgδ, were determined in the temperature range −150°C to 160°C. The correlation of the processing parameters and primary viscoelastic functions with content of the hard, PS, phase were discussed.
Study of the properties of rigid and plasticized PVC/PMMA blends
Authors: Belhaneche‐Bensemra N. , Bedda A. , Belaabed B. 
Published: October 2003

AbstractThe aim of this work is to study the structure‐properties relationship of rigid and plasticized PVC/PMMA blends. For that purpose, blends of variable compositions were prepared in the absence and in the presence of a plasticizer di (ethyl‐2 hexyl) phtalate or DEHP. The miscibility of the two polymers was investigated by differential scanning calorimetric analysis (DSC) and Fourier transform infrared spectroscopy. The weight loss from 30 to 600°C was investigated by thermogravimetric analysis (TGA). The thermal degradation under nitrogen at 185°C was studied and the amount of HCl released from PVC was measured by the pH method. Furthermore, the variation of mechanical properties such as tensile behavior, hardness and impact resistance was investigated for all blend compositions.
Cation‐exchange fabric prepared by electron beam‐induced graft copolymerization of binary monomer mixture
Authors: Bandar Yuliya , Kim Hong Je , Lim Yong Jin , Kravets Lyubov' 
Published: October 2003

AbstractApplying the electron‐beam preirradiation method in air the cation ‐ exchange fabric (CEF) containing sulfonic acid (R‐SO3H) groups was prepared by graft copolymerization of sodium styrenesulfonate with acrylic acid onto non woven polypropylene fabric. The effect of reaction conditions on the grafting yield and reaction mechanism was examined.The ion‐exchange properties towards Cu(II) and Co(II) ions of the CEF were investigated depending on the form of the CEF and a pH of the solution. It was found that the synthesized CEF contains both strong acid groups (R‐SO3H) and weak acid (R‐COOH) groups in almost equal proportion. The utilization of the CEF in Na+ form allows to make the best use of its ion‐exchange capacity.
Conformational aspects of segmented poly(ester‐urethanes)
Authors: Ioan S. , Cojocaru I.E. , Grigoras V.C. , Macocinschi D. , Filip D. 
Published: October 2003

AbstractSegmented poly(ester‐urethanes) containing hard and soft segments, were obtained from aromatic diisocyanates with thiodiglycol or diethylene glycol as chain extenders, and poly(ethylene glycol)adipate usig a multistep polyaddition process. Transition temperatures by differential scanning calorimetry and thermo‐optical analysis were employed to characterize polyurethane materials. Changes in the conformation of these polyurethanes were analyzed also, by viscometer measurements in N,N‐dimethyl‐formamide. The obtained data revealed that the thermal curves are influenced by the soft and hard segment structures in the temperature range studied.
UV stabilising synergies between carbon black and hindered light stabilisers in linear low density polyethylene films
Authors: Horrocks A. Richard , Liu Mingguang 
Published: October 2003

AbstractThe combined effects of selected carbon black pigments and hindered light stabilisers (HALS) on the UV stabilities of linear low density polyethylene film have been studied under UVA and UVB fluorescent radiation sources. While the presence of HALS do not change the chemistry of film photodegradation, whether they are low or high molecular variants, their presence significantly extends film lifetime relative to the sum of the effects of carbon black and HALS individually. These lifetime extensions may be defined in terms of a synergy factor defined with respect to film time to lose a specific percentage of a tensile property, namely t20, the time to lose 20% of initial elongation‐at‐break, or the carbonyl index associated with this condition.It is proposed that possible causes of this synergy are a result of the UV screening effect of the carbon black particles which provide lower concentrations of polymer radicals for the HALS component to interact with and/or an accompanying thermal stabilising effect by the latter as a consequence of the higher polymer local temperature during irradiation of pigmented films.