bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactive compatibilization of blends of PET and PP modified by GMA grafting
Authors: Pracella Mariano , Chionna Donatella 
Published: August 2003

AbstractThe melt radical grafting of glycidyl methacrylate (GMA) onto isotactic polypropylene (PP) was carried out in Brabender internal mixer and the influence of reaction procedure, radical initiator concentration and addition of co‐monomer (styrene) on the grafting efficiency was examined. The viscosity, the thermal behaviour and melt rheology of PP‐g‐GMA samples was then analysed as a function of grafted GMA content. Blends of poly(ethylene terephthalate) (PET) with PP and PP‐g‐GMA (5.2 wt% GMA), prepared in internal mixer, were characterised by SEM, DSC and melt viscosimetry. The morphological analysis of PET/PP‐g‐GMA blends (80/20, 50/50 w/w) pointed out a marked improvement of phase dispersion (with particle size of about 0.6 μm for 80/20 blend) and interfacial adhesion, as compared to non‐compatibilized PET/PP blend. The results of mixing torque and thermal analysis supported the occurrence of in‐situ compatibilization reaction between epoxy groups of GMA modified PP and carboxyl end‐groups of PET in the melt.
Reactively and physically compatibilized immiscible polymer blends: stability of the copolymer at the interface
Authors: Harrats Charef , Dedecker Kristof , Groeninckx Gabriel , Jérôme Robert 
Published: August 2003

AbstractThis paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene‐maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence.In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co‐continuous two‐phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes.
Morphology of reactive PP/PS blends with hyperbranched polymers
Authors: Pionteck Jürgen , Pötschke Petra , Proske Norbert , Zhao Hanying , Malz Hauke , Beyerlein Detlev , Schulze Ulrich , Voit Brigitte 
Published: August 2003

AbstractTo study the efficiency of different mechanism for reactive compatibilization of polypropylene/polystyrene (PP/PS) blends main chain or terminal functionalized PP and terminal functionalized PS have been synthesized by different methods. While the in‐situ block and graft copolymer formation results in finer phase morphologies compared to the corresponding non‐reactive blends, the morphology development in the ternary blend system PP/PS + HBP (hyperbranched polymer) is a very complex process. HBP with carboxylic acid endgroups reacts preferably with the reactive sites of the oxazoline functionalized PS (PS‐Ox) and locates mainly within the dispersed PS‐Ox phase. A bimodal size distribution of the PS‐Ox particles within the oxazoline modified PP (PP‐Ox) matrix phase is observed with big PS‐Ox particles (containing the HBP as dispersed phase) and small PS‐Ox particles similar in size like the unimodal distributed particles in the non‐reactive PP‐Ox/PS‐Ox blends. Factors influencing the morphology are discussed.
Compatibilized blends of thermoplastic polyurethane (TPU) and polypropylene
Authors: Lu Qi‐Wei , Macosko Christopher W. , Horrion Jacques 
Published: August 2003

AbstractCompatibilized blends of thermoplastic polyurethane (TPU) and polypropylene (PP) were developed using amine (primary or secondary) functionalized PP's (PP‐g‐NH2 or PP‐g‐NHR). The strategy of reactive compatibilization is based on fast reactions between amine functional groups and urethane linkages or traces of free isocyanates released by thermal degradation of TPU. Excellent compatibilization between TPU and PP was confirmed by rheological, morphological, and mechanical properties. Much finer domain size, higher interfacial adhesion, and more stable morphologies were clearly observed by scanning electron microscopy. Significant improvements in the overall mechanical properties (tensile, tear, abrasion) imply significantly more reaction between TPU and PP phases in the two TPU/PP blends containing PP‐g‐NH2 or PP‐g‐NHR than a TPU/PP blend using PP‐g‐MA as a compatibilizing agent.
Biodegradable compositions by reactive processing of aliphatic polyester/polysaccharide blends
Authors: Dubois Philippe , Narayan Ramani 
Published: August 2003

AbstractCommercially available biodegradable aliphatic polyesters, i.e., high molecular weight poly(ϵ‐caprolactone) (PCL) and polylactide (PLA), were melt blended with a well‐known natural and biodegradable polysaccharide: starch either as corn starch granules or as thermoplastic corn starch after plasticization with glycerol. Conventional melt blending yielded compositions with poor mechanical performances as a result of lack of interfacial adhesion between the rather hydrophobic polyester matrix and the highly hydrophilic and moisture sensitive starch phase. Interface compatibilization was achieved via two different strategies depending on the nature of the polyester chains. In case of PLA/starch compositions, PLA chains were grafted with maleic anhydride through a free radical reaction conducted by reactive extrusion. The maleic anhydride‐grafted PLA chains (MAG‐PLA) allowed for reinforcing the interfacial adhesion with granular starch as attested by TEM of cryofracture surface. As far as PCL/starch blends were concerned, the compatibilization was achieved via the interfacial localization of amphiphilic graft copolymers formed by grafting of PCL chains onto a polysaccharide backbone such as dextran. The PCL‐grafted polysaccharide copolymers were synthesized by controlled ring‐opening polymerization of ϵ‐caprolactone proceeding via a coordination‐insertion mechanism. These compatibilized PCL/starch compositions displayed much improved mechanical properties as determined by tensile testing as well as a much more rapid biodegradation as measured by composting testing.
Solvent activity changes and phase separation during crosslinking of coating films
Authors: Dušková‐Smrčková Miroslava , Dušek Karel , Vlasák Petr 
Published: August 2003

AbstractChanges in solvent activity and thermodynamic stability of a system undergoing crosslinking in the presence of a solvent are modeled by combination of branching theory with thermodynamics of polymer solutions and swelling of a crosslinked polymer. The system is considered as a quasiternary one in which the solvent, polydisperse soluble polymer (sol) and crosslinked network, respectively, represent the components. Crosslinking brings about growth of polymer structures but also changes in polymer‐solvent interactions. The results are compared with onset of phase separation and changes in evaporation rates from films formed from a hydroxy‐functional star oligomer and triisocyanate.
Ternary phase separation in polyurethane elastomers with immiscible soft segments
Authors: Mormann Werner , Zhang Chenxi 
Published: August 2003

AbstractPolyurethane elastomers with two immiscible hard‐segment polyols have been synthesized from homogeneous prepolymer mixtures, to obtain incompatibility on a molecular scale from reaction driven phase separation. Miscibility of a series of different soft‐segment polyols and of their prepolymers with 4,4′‐diisocyanatodiphenyl methane (MDI) has been investigated by cloud point analysis. UCST‐behavior was observed for all binary combinations of polyols and of prepolymers; prepolymer formation lowered UCST with respect to polyols with the option to adjust it by further addition of MDI. Polyurethane elastomers have been synthesized and characterized with respect to their thermal, mechanical and viscoelastic (DMTA) behavior. Broad temperature ranges of loss factor above 0.1 were observed from polyurethanes with two immiscible soft‐segment polyols. Rebound resilience, however, was still significant at room temperature, because of the low transition temperatures of the polyols used. Introduction of a third partially miscible component, a hard‐segment from tetraethyleneglycol and MDI gave materials with a loss factor above 0.1 over a temperature range from −50 to 120 °C and higher. The studies proved that the concept of intimate mixing of immiscible soft‐segments in polyurethanes works for the design of viscoelastic materials with good damping properties.
Thermodynamic analysis of the reaction‐induced phase separation in model systems based on blends of a rubber in diepoxide / monoamine precursors
Authors: Zucchi Ileana A. , Galante María J. , Borrajo Julio , Williams Roberto J.J. 
Published: August 2003

AbstractThe reaction‐induced phase separation in blends based on a carboxyl‐terminated poly(butadiene‐co‐acrylonitrile) rubber (CTBN), dissolved in diglycidyl ether of bisphenol A (DGEBA) ‐ benzylamine (BA) monomers, was studied. The polymerization kinetics was followed by size exclusion chromatography, for both the neat DGEBA‐BA system and for blends containing 10 wt% CTBN. No effect of CTBN addition on the polymerization rate was observed within experimental error. The kinetics could be fitted with a model based on the presence of non‐catalytic and OH‐catalyzed reactions and assuming equal reactivity of primary and secondary amine hydrogens. Cloud‐point conversions were determined at 60, 70 and 80 °C. The Flory‐Huggins model provided a reasonable fitting of experimental data using an interaction parameter depending exclusively on temperature, and taking polydispersities of both linear polymers into account. Linear epoxy/amine systems may be used to test the reliability of thermodynamic theories in more complex situations (e.g., modifiers with a broad distribution of molar masses or mixtures of several modifiers).
DGEBA monomer as a solvent for syndiotactic polystyrene
Authors: Schut Jaap , Stamm Manfred , Dumon Michel , Gérard Jean‐François 
Published: August 2003

AbstractSyndiotactic polystyrene (sPS) has to be processed at high temperatures (i.e. >290°C due to its melting point of 270°C), which approaches its degradation temperature. We aim to facilitate the processing of sPS by lowering its melt temperature and viscosity with a curable epoxy/amine model system as reactive solvent, which will result in a thermoplastic‐thermoset polymer blend. As a first step we therefore investigated the melting behaviour of sPS in epoxy monomer, established its phase diagram, and investigated the crystalline form of sPS in these mixtures. DGEBA epoxy monomer is found to be a solvent for syndiotactic polystyrene at temperatures above 220°C. The DGEBA‐sPS phase diagram was established by means of DSC, on the basis of crystallization and melting peaks. The form of the curve in the phase diagram indicates that DGEBA is a poor solvent for sPS. In WAXS studies of blends only the β crystalline form was detected, not the δ form, thus no sPS‐DGEBA polymer‐solvent compounds (clathrates) were detected. However, DGEBA can still serve as a monomer for improved processing as it depresses the crystallization temperature by 20 to 60 K upon addition of 20 to 90 wt% DGEBA respectively, while a 16 to 45 K melting peak depression can be observed by adding 20 to 90 wt% DGEBA.
Dielectric in situ sensor monitoring of phase separation and changes in the state of each phase
Authors: Kranbuehl D. , Rogozinski J. , Warner J. , Best P. , Pascault J.P. , Sautereau H. , Boiteux G. , Seytre G. 
Published: August 2003

AbstractFrequency dependent dielectric measurements have been used to monitor and characterize the phase separation process and changes in state of each phase. The measurements are made in situ using a micro planar sensor. They can be made both in the laboratory as well as in an industrial production or use environment. Two examples are presented. The first is monitoring the onset of phase separation, the buildup in Tg and change in composition of each phase during “reactive processing” of a high performance thermoplastic (TP) PPI, thermoset precursors (TS) DGEBA‐MCDEA intially homogeneous blend. The second example involves monitoring the stability, onset of phase separation, as a function of temperature on a mineral oil, stearyl alcohol, water, sufactant emulsion used in the cosmetic industry.
In situ real‐time monitoring of a diglycidyl ether of bisphenol a epoxy resin modified with poly(etherimide)/polysulphone blends by simultaneous dielectric/near‐infrared spectroscopy
Authors: Kortaberria G. , Arruti P. , Mondragon I. 
Published: August 2003

AbstractSimultaneous dielectric and near infrared measurements were performed in “real‐time” to follow polymerisation reactions on blends of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin with 4,4′‐diaminodiphenylmethane (DDM) hardener and a mixture of polysulphone (PSU) and polyetherimide (PEI) as modifier. All the blends had a 10 wt% of PSU/PEI mixture. The effect of the PEI/PSU ratio in the mixture was studied. Monitoring of the α‐relaxation (related to vitrification) was performed by dielectric measurements, while epoxy conversion was followed by near infrared spectroscopy. The effect of the PEI/PSU ratio on this behaviour was studied, as well as that of the curing temperature. Obtained results were compared with that of the blends with neat PSU and PEI as modifiers.
Processability and chemical resistance of the polymer blend of thermoplastic polyurethane and polydimethylsiloxane
Authors: Damrongsakkul Siriporn , Sinweeruthai Ratirat , Higgins Julia S. 
Published: August 2003

AbstractThis work is aimed to develop the melt blend of thermoplastic polyurethane (TPU) and polydimethylsiloxane (PDMS) and to study the effect of the chemical resistance on the tensile properties and morphology of the blends. The master batch blends at 2% of PDMS with 98% of TPU were firstly prepared by an internal mixer and then the blends of TPU/PDMS were prepared by melt mixing using a twin screw extruder. The maximum PDMS content that can be mixed with TPU was found to be no higher than 1%. Higher PDMS content leaves an unmelted TPU fraction in the blends due to the short residence time in the twin screw extruder. The resultant blends show an increase in the elongation at break up to 30% and in Young's modulus up to 40% at the optimum PDMS concentration of around 0.6%‐0.8%, beyond which these properties diminish. The ultimate tensile strength and the energy to break are decreased by about 20% and 10%, respectively. The Scanning Electron Micrographs of the blends show dispersed phases of PDMS in a TPU matrix. The domain size of the PDMS phase becomes smaller when increasing PDMS content from 0.2% to 0.8%. The morphology of the fractured surface of TPU/PDMS blends shows less fibrous characteristics with increasing PDMS content in the blends.For the study of the effects of chemical resistance on the tensile properties and morphology of TPU/PDMS blends, two chemical reagents, sulfuric acid (H2SO4, 3% v/v) and sodium hydroxide (NaOH, 10% w/v) are selected. The results on the relationship of chemical resistance to tensile properties and morphology of the blends show that NaOH solution has a stronger effect on the tensile properties and morphology of virgin TPU and the blends than H2SO4 solution. The ultimate tensile strength and the energy to break of virgin TPU after base immersion was found to be strongly decreased, which could be caused by the base hydrolysis of the polyester soft segment of polyurethane. The effect of PDMS content in the blends on the base resistance and tensile properties is similar to results before immersion, i.e. the effective PDMS content in the blends that can generally improve tensile properties of the blends after immersion in NaOH does not exceed 0.8%. The results are in agreement with the weight loss of TPU/PDMS blends after base immersion and the morphology of the fractured surface of TPU/PDMS blends after base immersion that exhibit very small amounts of a fibrous character. There are also some small particles detached at the surface. This could be the result of an occurrence of a corrosive reaction between the sample surface and NaOH solution.
Effect of fillers on fire retardancy of intumescent polypropylene blends
Authors: Almeras X. , Le Bras M. , Poutch F. , Bourbigot S. , Marosi G. , Anna P. 
Published: August 2003

AbstractAddition of Ammonium Polyphosphate/Polyamide‐6 system is known to provide flame retardancy in many polymers blends via an intumescent process. Particulate fillers (talc and calcium carbonate) are used in large quantities in PP. Combination of fillers in PP can modify the properties of the polymeric matrix. This study investigates the effect of fillers (talc and calcium carbonate) on the fire performance of the Polypropylene/Ammonium polyphosphate/Polyamide‐6 blend. It is shown that the fire performance strongly depends on the nature of the filler used. Talc increases and calcium carbonate decreases in the fire performance of the blend.
Water sorption and electrical/dielectric properties of organic‐inorganic polymer blends
Authors: Mamunya Yevgen , Kanapitsas Athanasios , Pissis Polycarpos , Boiteux Gisele , Lebedev Eugene 
Published: August 2003

AbstractOrganic‐inorganic polymer blends (OIPB) were obtained by reaction of organic and inorganic oligomers. The organic oligomer was synthesized with 2,4‐toluene diisocyanate (TDI) and oligooxypropylene glycols (OPG) with various molecular weights (MW). The inorganic component was a water solution of sodium silicate. The OIPB obtained are hydrophilic and have great water sorption ability (the relative weight of sorbed water reaches 2000 %). The kinetics of water sorption and the changes of electrical conductivity during sorption were studied. Sorption ability, and mechanical, electrical and dielectric properties of OIPB depend on molecular weight of OPG: conductivity increases with increasing MW, whereas the sorption ability correlates with the mechanical properties. The influence of the inorganic phase content on the electrical and dielectric properties was studied as well.
Structure and dielectric properties of a thermoplastic blend containing dispersed metal
Authors: Zois Haralampos , Mamunya Yevgen P. , Apekis Lazaros 
Published: August 2003

AbstractIn the present work broadband dielectric relaxation spectroscopy measurements were employed to investigate the dielectric properties of polymer composites. A polyethylene/polyoxymethylene (PE/POM) thermoplastic blend was used as a matrix, while the inclusions were iron (Fe) particles. For comparison, the two pure polymers‐ PE and POM‐ were used as a matrix, too. In the PE/POM‐Fe composites, the polymer matrix is two‐phase and the filler particles are localized only in the POM phase, resulting in an ordered distribution of the dispersed filler particles within the blend. In PE‐Fe and POM‐Fe composites, the filler spatial distribution is random. The behaviour of all the composites studied is described in terms of the percolation theory. The PE/POM‐Fe composites, based on the PE/POM blend, demonstrate different electrical behaviour compared to that of POM‐Fe and PE‐Fe systems. The percolation threshold value of the PE/POM‐Fe composites was found much lower than that of the other two systems. The results were related to the microstructure of the composites. A schematic model for the morphology of the composites studied has been proposed. This model explains the peculiar behaviour of the PE/POM‐Fe composites by taking into account the ordered distribution of the filler particles in a binary polymer matrix. Optical microscopy photographs confirm this model.
Characterization of extruded ethylene‐vinyl alcohol copolymer based barrier blends with interest in food packaging applications
Authors: Lagarón J.M. , Giménez E. , Altava B. , Del‐Valle V. , Gavara R. 
Published: August 2003

AbstractBased on previous work a number of optimum extruded blends with high contents of a high barrier ethylene‐vinyl alcohol copolymer were selected and characterized in terms of phase morphology, water sorption and barrier properties. Blend components were an ethylene vinyl‐alcohol copolymer (EVOH with 32 mol% ethylene), an amorphous polyamide (aPA) and a nylon‐containing ionomer. A fine two phase structure was found for these blends in all cases. However, Raman spectroscopy results indicated a poor interface interaction between the blend components in the case of the EVOH/aPA blends. Higher interface interaction had been previously found in the dry EVOH/ionomer blends. Equilibrium moisture solubility and diffusion were found to be higher than expected from simple additivity. However, the oxygen transmission rate was found to be clearly lower than expected from the rule of mixtures, particularly under dry conditions, fitting closely a simple Maxwell model.
Androgen‐independent expression of adrenomedullin and peptidylglycine α‐amidating monooxygenase in human prostatic carcinoma
Authors: Jiménez Nuria , Abasolo Ibane , Jongsma Johan , Calvo Alfonso , Garayoa Mercedes , van der Kwast Theodorus H. , van Steenbrugge Gert J. , Montuenga Luis M. 
Published: August 2003

AbstractMost of the locally advanced and metastatic prostate carcinomas (PCs) treated with antiandrogenic therapy eventually become refractory to this treatment. Locally produced factors may control prostate tumor biology after androgen withdrawal. Adrenomedullin (AM) is expressed in the prostate and could control cell growth in androgen‐independent conditions. AM needs to be amidated by the enzyme peptidylglycine α‐amidating monooxygenase (PAM) to become fully active. The objective of the present study was to analyze whether the expression of preproadrenomedullin (preproAM) and PAM in PC is regulated by androgens. For this purpose, human in vitro and in vivo PC models were grown in the presence or absence of androgens, and the expression of AM and PAM was examined by immunohistochemistry, Western blotting, RT‐PCR, and Northern blotting. Furthermore, immunohistochemical analysis of AM in clinical specimens was performed to test if its expression is related to Gleason score and antiandrogenic therapy. In PC cell lines and xenografts, mRNA and protein AM levels were similar in the presence or absence of androgens. PAM expression seemed to be induced by androgen‐withdrawal. Our results in clinical samples showed no relationship between AM expression and Gleason score or antiandrogenic treatment. In conclusion, our results demonstrate that preproAM and PAM expression in the human prostate is androgen‐independent. In addition, we also report for the first time the expression of a novel PAM transcript in PC, which has not been previously described in other tissues. © 2003 Wiley‐Liss, Inc.