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Showing papers in "Polymer Bulletin in 2003"


Journal ArticleDOI
TL;DR: In this article, a nucleophilic substitution reaction of 2,6-dichlorobenzonitrile with resorcinol and with varying mole proportions of resorbinol and hydroquinone was used to synthesize polyether nitrite copolymers.
Abstract: Polyether nitrite and its copolymers were synthesized by nucleophilic substitution reaction of 2,6-dichlorobenzonitrile with resorcinol and with varying mole proportions of resorcinol and hydroquinone. The polymers were characterized by different physico-chemical techniques. Thermogravimetric studies showed that all the polymers were stable up to 400°C with a char yield of above 48% at 900°C in N 2 atmosphere. The glass transition temperature was found to increase with increase in concentration of hydroquinone units in the polymer; however no trend was observed in their crystalline melt temperatures. Copolymer composition was determined using FT-IR technique. Crystallinity of the polymers was also studied using wide angle X-ray diffraction.

81 citations


Journal ArticleDOI
TL;DR: In this paper, single-site calcium initiators containing chelating tmhd (H-tmhd = 2,2,6,6-tetramethylheptane-33-dione) ligands were synthesized and applied for the ring-opening polymerization of L-lactide and e-caprolactone.
Abstract: Single-site calcium initiators containing chelating tmhd (H-tmhd = 2,2,6,6-tetramethylheptane-33-dione) ligands [(THF)Ca(tmhd)]2[μ-N(SiMe3)2](μ-tmhd) (2) and [(THF)Ca(tmhd)]2[μ-OCH(Me)Ph](μ-tmhd) (3) have been synthesized and applied for the ring-opening polymerization of L-lactide and e-caprolactone. Both 2 and 3 were highly reactive and promoted a fast polymerization of L-lactide and e-caprolactone to high monomer conversions under mild conditions (THF as a solvent, room temperature). More importantly, results showed that the ring-opening polymerizations of lactides and lactones initiated by either 3 or 2 in the presence of equivalent 2-propanol are living, to provide polymers and block copolymers of controlled molecular weights and tailored end-groups. The polymerizations were first-order in monomer up to high conversions, in which the in situ initiating system 2/2-propanol revealed no induction period and much faster polymerization kinetics as compared to 3.

72 citations


Journal ArticleDOI
TL;DR: The synthesis of a salicylate-based poly(anhydride-ester) was optimized to improve the overall efficiency and quality of the polymer to include dynamic mixing, which yields polymer with increased molecular weights on both the milligram and gram scale.
Abstract: The synthesis of a salicylate-based poly(anhydride-ester) was optimized to improve the overall efficiency and quality of the polymer. First, a new approach for the preparation of the polymer precursor minimizes the overall number of synthetic steps and increases the overall yield. Second, the melt-polymerization apparatus was modified to include dynamic mixing, which yields polymer with increased molecular weights on both the milligram and gram scale.

66 citations


Journal ArticleDOI
TL;DR: In this paper, conditions for complex formation of some transition metal salts and emeraldine base of polyaniline were investigated, and the obtained macromolecular complexes have been characterized by the UV-Vis-IR spectroscopy.
Abstract: Conditions for complex formation of some transition metal salts and emeraldine base of polyaniline were investigated, and the obtained macromolecular complexes have been characterized by the UV-Vis-IR spectroscopy. It was found that complex formation conditions are dependent on both the cation and anion of the inorganic salt used, as well as on the solvent environment. In some cases, formation of the complex occurred in the form of a precipitate directly in the solution. In other cases, no precipitate was observed in the solution, however, the complex was recognized during film casting from the polyaniline – inorganic salt solution. Electronic absorption spectra for both precipitates and films for the majority of samples possessed features characteristic of the protonated, emeraldine salt form of the polymer. However, IR absorption spectra were different from the protonated polyaniline form. Based on the obtained data, the model of the macromolecular polyaniline – transition metal salt complex is proposed.

51 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of a biocompatible electrostatic complex was investigated and a conductimetric method was proposed to control the complex formation. But the degree of association of the complex is determined and the role of the auto-dissociation of the chitosan hydrochloride on the formation is discussed.
Abstract: This paper concerns the formation of a biocompatible electrostatic complex; a conductimetric method is proposed to control the complex formation. The dissociation of chitosan in acidic medium is considered and the method for determination of the degree of acetylation is revisited. The degree of association of the complex is determined and the role of the auto-dissociation of the chitosan hydrochloride on the formation of the complex is discussed. The complex formed is very stable and cooperative for low degree of acetylation of the chitosan. The stability of the complexes formed is tested as a function of the pH. The role of the different parameters involved are examined (degree of acetylation of chitosan, external salt concentrations).

49 citations


Journal ArticleDOI
TL;DR: In this paper, a ring-opening polymerization of 2-methyl-2-oxazoline using various octafunctional POSS as an initiator with changing the feed ratio of POSS to 2-moxy-2.oxazolines was proposed.
Abstract: Hybrid star-shaped polyoxazolines having POSS core were prepared by ring-opening polymerization of 2-methyl-2-oxazoline using various octafunctional POSS as an initiator with changing the feed ratio of POSS to 2-methyl-2-oxazoline. The core-first method, which uses an active multifunctional core to initiate growth of polymer chains, was applicable to make hybrid POSS-core star-shaped polyoxazolines. The kinetic rate of the polymerization and the structures of hybrid star-shaped polyoxazolines were characterized by gas chromatography (GC) and 1H NMR, respectively. Their thermal properties were investigated in detail by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

48 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used a sulfide complex of Ti(III) chloride and 1,2-bis(hexylthio)ethane for atom transfer radical polymerization (ATRP) of styrene.
Abstract: Ti(III) compounds (halides and n-butoxide) along with several mono-, bi-, and tridentate ligands have been studied for the first time in the atom transfer radical polymerization (ATRP) of styrene. The important advantage of titanium compounds is the white color of the Ti(IV) ions (Ti in the highest and air stable oxidation state) which ensures the absence of coloring in the final polymer. The better control over polymerization was realized when conditions increasing the reactivity of the intermediate Ti(IV) species and decreasing their steady state concentration were maintained. This occurred when chlorides were replaced with bromides (which decreased the bond strength), and when ligands with low donor ability were employed. Using a sulfide complex of Ti(III) chloride and 1,2-bis(hexylthio)ethane allowed styrene polymerization with kinetic and molecular weight characteristics inherent to ATRP.

47 citations


Journal ArticleDOI
TL;DR: In this article, the residual weight and new IR peaks of the clay, which is treated by in-situ polymerization, imply that the hydroxy group of intercalant takes part in the polymerization of allylester resin.
Abstract: Allylester resin tethered to layered silicate was synthesized by in-situ polymerization method and was cured by tert-butylperbenzoate (TBPB) directly. We ascertained the existing of carbonyl and benzyl groups which come from diallyl terephtalate in the gallery of layered silicates using the thermogravimetric analysis (TGA) and FT-IR. The residual weight and new IR peaks of the clay, which is treated by in-situ polymerization, imply that the hydroxy group of intercalant takes part in the polymerization of allylester resin. Also, its nanocomposite was characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns and TEM photographs indicate that the basal spacing (d 001 ) of the nanocomposite made by in-situ polymerization is larger than those of the nanocomposite made by a simple mixing.

40 citations


Journal ArticleDOI
Naoki Hasegawa1, Arimitu Usuki1
TL;DR: In this paper, a novel scheme for controlling the nanostructures of organic polymer materials by using nanoparticles as templates was proposed and spontaneous formation of arranged microdomain structures in block copolymers controlled by clay silicate layers dispersed at the nanometer level.
Abstract: We propose a novel scheme for controlling the nanostructures of organic polymer materials by using nanoparticles as templates and we also demonstrate a spontaneous formation of arranged microdomain structures in block copolymers controlled by clay silicate layers dispersed at the nanometer level. Block copolymer-layered silicate nanocomposites were prepared by melt compounding of hydrogenated styrene-butadiene-styrene triblock copolymer with organophilic layered silicates intercalated with stearylammonium. Their morphologies were observed by transmission electron microscopy. The triblock copolymer microdomain structures were found to be arranged along the dispersed silicate layers. Such structures did not exist in the original block copolymer. TEM images suggest that the formation of the arranged microdomain structures are induced and controlled by the interaction of the silicate layers, which act as templates. It is thought that these controlled nanostructures were formed through the selective absorption of the polystyrene segments on dispersed silicate surfaces followed by segregation of each segment.

39 citations


Journal ArticleDOI
TL;DR: Aqueous ATRP of SSNa has been investigated in the presence of initiator, 2-bromo-2-methylpropionate (l), mediated with Cu(I)Br/bpy as discussed by the authors.
Abstract: Aqueous ATRP of SSNa has been investigated in the presence of initiator, 2-bromo-2-methylpropionate (l), mediated with Cu(I)Br/bpy. When using water only as a polymerization solvent, some deviations from the living behaviors were observed, including a bimodal molecular weight dictribution. It was found that the competitive coordination effect of water could be suppressed by using Cu(11)Br or Variation of polymerization solvent. The addition of Cu(II)Br with the ratio of Cu(I)/Cu(II)= 1 was found to give the Optimum results with 92% conversion achieved in approximately 60 min, leading to a polymer with a molecular weight close to the theoretical with a polydispersity index=1.20. Using mixture of water and methanol with the ratio of water/methanol=30/20 wt% also suppressed the formation of the high molecular weight fraction and more than 95 % conversion was achieved in 80 min. SEC of the resulting polymer was monodisperse with a polydispercity index = 1.21.

37 citations


Journal Article
TL;DR: In this article, a novel class of materials exhibiting negative Poisson's ratio (NP) is presented, and the microstructure and deformation mechanism of NP materials are analyzed by comparing with the conventional polymer materials.
Abstract: A novel class of materials exhibiting negative Poisson's ratio—a popular research field of materials science in recent years, is presented. By analyzing the microstructure and deformation mechanism of negative Poisson's ratio materials and comparing with the conventional polymer materials, detailed interpretation of special physical properties are given in this paper. Meanwhile, it should be pointed out that this kind of materials has the bright prospect of applications and practical significance.

Journal ArticleDOI
TL;DR: In this paper, the essential work of fracture (EWF) was applied to unplasticised polyvinyl chloride (uPVC) films and energy partition analyses were carried out applying two different approaches (yielding and initialization) which differ in the treatment of stored elastic energy.
Abstract: Unplasticised poly(vinyl chloride) (uPVC) films have been tested using the essential work of fracture (EWF) method. Influence of loading rate and film thickness on the tensile properties and work of fracture parameters was evaluated. In addition, energy partition analyses were carried out applying two different approaches (“yielding” and “initiation”), which differ in the treatment of the stored elastic energy. Results showed less effect of the film thickness and deformation rate (

Journal ArticleDOI
TL;DR: In this paper, poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) using benzoyl peroxide (Bz2O2) as the initiator.
Abstract: Poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) using benzoyl peroxide (Bz2O2) as initiator. Fibers were swelled in dichloroethane (DCE) for 2 h at 90 °C to promote the incorporation and the subsequent polymerization of 4-VP onto PET fibers. Variations of graft yield with time, temperature, initiator and monomer concentrations were investigated. Percent grafting was enhanced significantly by increasing Bz2O2 concentration up to 2 × 1 0 -3 mol/L and then decreased upon further increase in initiator concentration. Increasing the 4-VP concentration up to 0.6 mol/L improves the graft yield significantly. The optimum temperature and polymerization time was found to be 50 °C and 2 h respectively. Further changes in properties of grafted PET fibers such as moisture absorption capacity and intrinsic viscosity were determined. Grafted PET fibers were charactarized by thermogravimetric analysis and scanning electron microscopy (SEM). Molar mass of the grafted chains was also determined.

Journal ArticleDOI
TL;DR: In this paper, Me2Si(2MeBenzlnd)2ZrCl2/MAO supported on these nanoparticles is suitable for the homopolymerization of ethylene, resulting in excellent product morphologies and high activities.
Abstract: Novel organic nanoparticles functionalized with nucleophilic polypropyleneoxide (PPO) chains on their surfaces for supporting metallocene catalysts in heterogeneous olefin polymerization are presented The nanoparticles (60–100 nm) were obtained by miniemulsion polymerization of styrene, divinylbenzene and PPO functionalized styrene It is demonstrated that Me2Si(2MeBenzlnd)2ZrCl2/MAO supported on these nanoparticles is suitable for the homopolymerization of ethylene, resulting in excellent product morphologies and high activities lt is shown that by varying the MAO/Zr ratios and Zr concentrations the activities and productivities of the catalysts as well as the qualities of the polyethylene products can be tuned These new supported catalysts are also suitable for the copolymerization of ethylene with several comonomers (1-hexene, 1-octene, 1-decene or norbornene) As the obtained product properties like crystallinity, melting temperature or bulk density match the results of silica supported systems, these organic nanoparticles can be considered as alternative carriers in comparison to the established inorganic ones

Journal ArticleDOI
TL;DR: In this article, a cyclic acetal functionalities were added to polyvinyl alcohol (PVA) to obtain temperature-responsive copolymers, which were characterized by 1D (1H, 13C, DEPT) and 2D (COSY) NMR techniques as well as viscometry.
Abstract: In order to obtain novel temperature-responsive copolymers, poly(vinyl alcohol) (PVA) was chemically modified by introducing cyclic acetal functionalities in the polymer chain. The acetalization reaction was carried out with acetaldehyde in water The degree of acetalization was controlled in the range 10–25% by the initial aldehyde concentration. The copolymers obtained were characterized by 1D (1H, 13C, DEPT) and 2D (COSY) NMR techniques as well as by viscometry. The thermo-responsive properties were evaluated by measuring the cloud point temperature (Tcp) of the aqueous copolymer solutions.

Journal ArticleDOI
TL;DR: In this article, the effects of γ-rays on different PEs using the ESR, FTIR and DSC spectra were studied. And they found that the chemical reactions produced during radiation as well as during the storage time are mainly scission and crosslinking and/or branching.
Abstract: We study the effects of γ-rays on different PEs using the ESR, FTIR and DSC. The changes in the ESR and FTIR spectra after irradiation is studied. We found that the chemical reactions produced during radiation as well as during the storage time are mainly scission and crosslinking and/or branching. The percentage of each of these reactions was determined by the Charlesby-Pinner equation and we concluded that they depend on the linearity of the PE.

Journal ArticleDOI
TL;DR: In this paper, conductive composites from carbon black/poly(butyl methacrylate) (CBPBMA) are synthesized through polymerization filling and the experimental results indicate that relatively low percolation threshold (∼6wt%) is associated with the composites.
Abstract: Conductive composites from carbon black/poly(butyl methacrylate) (CBPBMA) are synthesized through polymerization filling. The experimental results indicate that relatively low percolation threshold (∼6wt%) is associated with the composites. When the composites are exposed to good solvent vapors of the matrix polymer, the electric resistance of the composites drastically increases by over lo4 times. In the case of poor solvent vapor, however, the electrical response of the composites is rather weak, demonstrating selective gas sensibility. In addition, environment temperature exerts great influence on the responsivity of the composites against organic vapors. The higher the temperature, the faster and the stronger the electrical response. It was also found that the response of electric resistance of the composites against good solvent vapors is provided with sufficient reproducibility and stability. It can thus be concluded that the CB/PBMA composites can be used as promising gas sensing materials in practice.

Journal ArticleDOI
TL;DR: In this article, polyimide/silica hybrid materials were prepared via a novel sol-gel route using silicic acid oligomer (SAO) extracted from water glass.
Abstract: Polyimide/silica hybrid materials were prepared via a novel sol-gel route using silicic acid oligomer (SAO) extracted from water glass. The decomposition temperatures of the hybrid samples were higher than pure polyimide. The transparency of the hybrid films could be maintained at up to 40 wt.-% silica content with the addition of γ-aminopropyltriethoxysilane (APTES). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results confirmed the formation and dispersion of nanometer-scale size of inorganic particles within polyimide matrix with APTES. The coefficients of thermal expansion (CTEs) of the hybrid films were lower than pure polyimide and decreased with the increasing content of silica.

Journal ArticleDOI
TL;DR: In this article, a novel synthetic procedure for the preparation of block copolymers based on the combination of diphenylethene mediated controlled radical polymerization and radical promoted cationic polymerization is described.
Abstract: A novel synthetic procedure for the preparation of block copolymers based on the combination of diphenylethene (DPE) mediated controlled radical polymerization and radical promoted cationic polymerization is described. In the first step, the controlled polymerization of styrene (St) and methyl methacrylate (MMA) in presence of DPE yields polymers with various structures of diphenylethyl units in the main chain. Upon heating these prepolymers undergo scission to give polymeric radicals. Oxidation of these radicals by onium salts such as diphenyliodonium heaxfluorophosphate (Ph2I+PF6 −) and N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP+PF6 −) yields reactive cations capable of initiating cationic polymerization of cyclohexene oxide (CHO). Block copolymer structure was confirmed by IR and NMR spectral measurements and GPC analysis.

Journal ArticleDOI
TL;DR: In this paper, a series of temperature responsive water-soluble poly(glycidol-co-GCL acetate) copolymers of different molar masses and chain topology (linear and comb-like) were synthesized.
Abstract: Polymers of glycidol (2,3-epoxypropanol-1) of different molar masses (between 2˙104 and 2˙105) and chain topology (linear and comb-like) were synthesised and used to obtain a series of temperature responsive water-soluble poly(glycidol-co-glycidol acetate)s. The degree of the substitution of the hydroxyl groups with the acetate groups influences the solution behaviour of the obtained copolymers, the cloud point may be controlled between +4°C and +lOO°C.

Journal ArticleDOI
TL;DR: In this paper, the results of doping polyaniline with dodecylbenzenesulphonic acid and reprocessing with polystyrene sulphonic acid (PSS) in an internal mixer, to obtain a conductive polymer blend (PAni-DBSAPSS).
Abstract: Polyaniline, PAni, has very promising industrial applications because of its good environmental stability, low cost and simple synthesis. Polyaniline doped with organic protonic and polymeric acids shows improved solubility and processability by conventional methods. In this work we report the results of doping polyaniline with dodecylbenzenesulphonic acid (PAni-DBSA) and reprocessing with polystyrene sulphonic acid (PSS) in an internal mixer, to obtain a conductive polymer blend (PAni-DBSAPSS). This investigation of the blend properties focused on the thermal stability, calorimetric behaviour and resulting electrical conductivity.

Journal ArticleDOI
TL;DR: In this paper, the influence of the surface of organic nanoparticles used as supports in metallocene catalysed olefin polymerization is investigated, and it is suggested that a higher amount of polypropylene oxide (PPO) chains on the support could result in a stronger network between the different nanoparticles due to the enhanced interaction of the PPO with the methylaluminoxanes so that the diffusion of the ethylene monomer to the active metal sites is hindered.
Abstract: In this paper the influence of the surface of organic nanoparticles used as supports in metallocene catalysed olefin polymerization is investigated. Several latex particles with different amounts of polypropylene oxide (PPO) chains on the surface were synthesized by miniemulsion polymerization and used as supports for the Me2Si(2MeBenzInd)2ZrCl2 / MAO complex. These catalysts were applied in heterogeneous ethylene polymerization. It was observed that longer PPO chains on the supports coordinated more metal sites than shorter ones to give catalysts with higher activities. An increased amount of PPO chains on the supports, however, led to catalysts with lower activities. It is suggested that a higher amount of PPO chains on the support could result in a stronger network between the different nanoparticles due to the enhanced interaction of the PPO with the methylaluminoxanes so that the diffusion of the ethylene monomer to the active metal sites is hindered.

Journal ArticleDOI
TL;DR: In this paper, acrylic acid and N-isopropylacrylamide were grafted from their binary mixtures in water onto polytetrafluoroethylene filament γ-preirradiated in air.
Abstract: Acrylic acid and N-isopropylacrylamide were grafted from their binary mixtures in water onto polytetrafluoroethylene films γ-preirradiated in air. Effects of preirradiation dose as well as temperature of grafting on efficiency of this process were investigated, the optimal values of dose and temperature were 20 kGy and 50 °C, respectively. The calculated monomers reactivity ratios by their graft copolymerization (r1 and r2 ) were 0.35 and 0.01, respectively. The grafted copolymers exhibited a temperature-responsive character in the range of 17-30 °C.

Journal ArticleDOI
TL;DR: The potato phosphorylase-catalyzed polymerization of α-D-glucose-1-phosphate (G-1P) onto poly[styrene-block-(4-vinylbenzyl maltohexaoside)] was performed at the molar ratios of [G-l-P]0 and [maltohexaose]0 of 35, 80, and 250.
Abstract: The potato phosphorylase-catalyzed polymerization of α-D-glucose-1-phosphate (G-1-P) onto poly[styrene-block-(4-vinylbenzyl maltohexaoside)] (1) was performed at the molar ratios of [G-l-P]0 and [maltohexaose]0 of 35, 80, and 250. The product was found to be soluble in dimethyl sulfoxide, which was a good solvent for amylose, and showed the complex-formation with iodine, indicating that the product was assignable to poly[styrene-block-(styrene-graft-amylose)] (2). The quantitative analysis of the liberated phosphoric acid gave the average degree of polymerization o f the glucose unit (n) as 27, 5 1, and 180 for 2-I, 2-II, and 2-III, respectively.

Journal ArticleDOI
TL;DR: In this article, the Atom Transfer Radical Polymerization (ATRP) of vinyl monomers mediated by a new class of ruthenium alkylidene catalysts containing a 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene and a Schiff base ligand was examined.
Abstract: In this study we examine the Atom Transfer Radical Polymerization (ATRP) of vinyl monomers mediated by a new class of ruthenium alkylidene catalysts containing a 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene and a Schiff base ligand. A controlled radical polymerization can also be achieved with the corresponding cationic complexes using both toluene and a watedtoluene mixture as solvent. Our results point out that with these cationic complexes the solvent is crucial for the activity and controllability of the metal-catalysed polymerization. In aqueoudorganic biphasic conditions these cationic systems are active in the radical polymerization of hydrophobic monomers such as methyl methacrylate, methyl acrylate and styrene and polymers with controlled molecular weights and narrow molecular weight distributions are obtained.

Journal ArticleDOI
TL;DR: In this article, the thermal behavior of some HNBR blends with CPE, PVC, CR and NBR at three temperatures, 150, 170 and 190°C, is presented.
Abstract: In this paper thermal behavior of some HNBR blends with CPE, PVC, CR and NBR at three temperatures, 150, 170 and 190°C is presented. Changes in characteristic IR bands, gel fraction, and chlorine content were assessed. Some mechanistic differences between the studied systems, regarding the involvement the depletion of chlorine and modification in gel content, were pointed out. Cyclization of nitrile structure was also observed by means of 2240 cm−1 band ascribed to >C=NH. Kinetic considerations are presented.

Journal ArticleDOI
TL;DR: In this article, a nanocomposites with poly(butylene terephthalate)(PBT) incorporated between the montmorillonite (MMT) layers were synthesized from DMT and butane diol by using an in-situ interlayer polymerization approach.
Abstract: The nanocomposites with poly(butylene terephthalate)(PBT) incorporated between the montmorillonite (MMT) layers were synthesized from dimethyl terephthalate (DMT) and butane diol (BD) by using an in-situ interlayer polymerization approach. The PBT nanocomposites were melt spun at different organoclay contents to produce monofilaments. The existence of clay layers in the PBT was confirmed by using X-ray diffraction and transmission electron microscopy, and those layers were found to be disperse on a nanometer scale. The thermal properties of the layered structures of the hybrids were found to be more stable than those of pure PBT. These improved thermal properties of the nanocomposites might arise from an extensive and strongly bonded interface between the organic and the inorganic components. Moreover, the addition of only a small amount of organoclay was enough to improve the mechanical properties of the PBT hybrid fibers.

Journal ArticleDOI
TL;DR: In this article, the elastic behavior of swollen ionic poly(acry 1amide) (PAAm) gel beads was investigated as a function of the bead diameter, and it was observed that the effective crosslink density of PAAm gel beads produced in the same synthesis batch increases with increasing bead diameter.
Abstract: Summary The elastic behavior of swollen ionic poly(acry1amide) (PAAm) gel beads was investigated as a function of the bead diameter. For this purpose, an experimental setup was designed to measure the modulus of hydrogel beads. An inverse suspension polymerization technique was used to obtain spherical beads of sizes 3 to 11 mm. It was observed that the effective crosslink density of PAAm gel beads produced in the same synthesis batch increases with increasing bead diameter, which was attributed to the inverse suspension polyinerization condition.

Journal ArticleDOI
TL;DR: In this article, isotactic polypropylene (PP) and nitrile rubber (NBR) blends, in the composition range of 10-30-wt % NBR content were studied, with special reference to the effect of blend ratio, dynamic vulcanization and compatibilization.
Abstract: Rheological behavior of isotactic polypropylene (PP) and nitrile rubber (NBR) blends, in the composition range of 10–30-wt % NBR content were studied, with special reference to the effect of blend ratio, dynamic vulcanization and compatibilization. All blends were prepared in a twin-screw extruder. Capillary Rheometry was employed. Pseudoplastic behavior of blends was favored by increasing rubber content. The incorporation of NBR into PP lowered activation energies. Compatibilization of unvulcanized blends did not produce significant changes on flow behavior. Dynamically vulcanized blends provide unique processing characteristics that enable to perform well in both injection molding and extrusion.

Journal Article
TL;DR: In this article, the mechanism, kinetics and characteristics of the living radical polymerization with reversible addition\|fragmentation chain transfer (RAFT) are reviewed in detail The principles of selecting a proper RAFT agent for a given polymerization, and the synthesis process of the agent are presented briefly Additionally, the development and application of the RAFT polymerization were summarized
Abstract: In this paper, the mechanism, kinetics and characteristics of the living radical polymerization with reversible addition\|fragmentation chain transfer (RAFT) are reviewed in detail The principles of selecting a proper RAFT agent for a given polymerization, and the synthesis process of the agent are presented briefly Additionally, the development and application of the RAFT polymerization were summarized