bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bimodality and Increased Amount of Crosslinker Enhances Tensile Properties of the Silicone Networks
Authors: Shah Gul Bali 
Published: August 2014

AbstractThe effect of bimodality i.e. blending short and long chain (0 to 80 % w/w) silicone prepolymers, and that of concentration of the crosslinker on the tensile properties such as percent elongation at break (%Eb), ultimate tensile strength (UTS), 100 % modulus and elastic modulus (E) has been investigated. It was found out that the greater amount of crosslinker used for crosslinking provide an additional reinforcement to the silicone network whereas bimodality further significantly accentuates this effect. Remarkably, the %Eb of the silicone networks was found to increase to an average of 2.4 times than that of the monomodal network, cured in each of the three series of bimodal networks cured with 3.9, 9.1 and 12.3% of crosslinker. The optimum property in each case was observed at about 70 mol % of P100. The over all order of sensitivity of these properties up to about 70 mol % of short chain prepolymer has been observed to be as: %Eb > UTS > 100% modulus > elastic modulus. It has been shown that in addition to the previously published reports the tensile properties are acutely dependent not only upon the degree of crosslinking and primary molecular weight; but also on bimodality and crosslinker concentration for preparation of the unfilled silicone polymer networks. The concept of phase inversion (or phase transition) associated with the optimum properties in polymer blends has for the first time been applied to the bimodal polymer networks. It has been observed that the maxima in tensile properties generally corresponds to phase inversion which takes place at 0.5 volume fraction (70 mol %) of short chain (P100) prepolymer which is in accordance with the literature for other systems.
Synthesis and Characterization of Porous Crosslinked Copolymers for Oil Spill Sorption
Authors: Abdel-Azim Abdel-Azim A. , Abdul-Raheim A. Mahmoud , Atta Ayman Mohamady , Brostow Witold , El-Kafrawy A. Fawzy 
Published: August 2014

AbstractCinnamoyloxy ethyl methacrylate (CEMA) was copolymerized with different monomer feed ratios of octadecyl acrylate (ODA) and crosslinked using azobisisobutyronitrile (AIBN) as the initiator and N,N’,N”-trisacryloyl melanine (AM) or N,N’,N”,-trismethacryloylmelanine (MM) crosslinkers. The networks are characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). For crosslinked CEMA/ODA copolymer sol fraction values are lower when MM is used rather than AM. The thermal stability of crosslinked network increases with increasing ODA concentration and also in the presence of MM crosslinker, a consequence of higher crosslinking density. SEM results show a porous structure; micropores are formed when ODA contents increases. According to DMA results, the flexibility of the network is enhanced by incorporation of MM rather than AM. Since our crosslinked networks are both flexible and porous, they are applicable as oil sorber networks to alleviate pollution from oil spills.
Particle Morphology of Epoxidised Natural Rubber Latex Prevulcanized by Peroxide System
Authors: Suteewong Teeraporn , Tangboriboonrat Pramuan 
Published: August 2014

AbstractEpoxidised natural rubber (ENR) latex could be prevulcanized by employing tert-butyl hydroperoxide/fructose system. By applying the phase transfer/bulk polymerization/ transmission electron microscopy (TEM) technique, the uniform crosslink distribution in peroxide-prevulcanized (PP) ENR particle was observed. However, the membrane layer of protein-lipid complex, originally existing at rubber particle surface, could not be detected. Results implied that the alkoxy radicals penetrated throughout the rubber phase. The diffusion rate of radicals should be equal to that of vulcanization. Under TEM, the uniform mesh-like particle and cluster of the rubber chains were observed in PP(NR/ENR) while micrographs of PP-NR/PP-ENR blends showed only the crosslinked particles whose structure correlated well with that of PP-NR.
Study of Mechanical Properties and Morphology of PA 6/PO Blends Compatibilized by PO Grafted with Itaconic Acid
Authors: Xijun Liu , Zhaohua Jiang , Wenming Zhu 
Published: August 2014

AbstractTwo different types of polyolefine (PO) grafted with itaconic acid as a reactive compatibilizer, polypropylene (PP) grafted with itaconic acid (PP-g-ITA) and high density polyethylene (HDPE) grafted with itaconic acid (HDPE-g-ITA), PP and HDPE grafted with copolymer of itaconic acid and styrene (PP-g-(ITA-St) and HDPE-g-(ITA-St)) were prepared by melt graft technique through reactive type twin-screw extruder. FT-IR and thermal analysis were used to characterize the structure of the graft copolymer. The graft ratio (GR) and melt flow rate (MFR) were determined by non-aqueous titration and melt flow rate analyzer. The effect of the concentration of monomer and initiator dosage on GR and MFR of graft copolymer were studied. Then polyamide 6 (PA 6) blends, PA 6/PP (PA 6/HDPE), that compatibilized with PP-g-ITA (HDPE-g-ITA) were prepared. The morphology of the blends was analyzed by SEM, DSC and Molau tests and the mechanical properties of which were characterized by tensile, impact, and bend tests. The results of mechanical property showed that the impact strength of blends was increased by 50% and 70% after PP-g-ITA and HDPE-g-ITA was used as compatibilizer, but the MFR of blends was decreased. The SEM photographs indicated that the accession of compatibilizer obviously improved binding state between two phases in blends, the size of dispersed phase was reduced evidently and the interface became indistinct. DSC results demonstrated that in the case of PP-g-ITA, glass temperature (Tg) of PA 6 matrix in blends was ascended, melt point (Tm) was improved a little, crystallinity (Xc) was decreased, Tm and Xc of PP phase was increased; With the accession of HDPE-g-ITA, Tm of PA 6 matrix and HDPE phase had almost no change, Xc of PA 6 matrix was decreased and Xc of HDPE phase was increased.
Modeling of Precipitation Polymerization I: The Method of Finite Molecular Weight Moments
Authors: Bouhendi H. , Haddadi-Asl V. , Rafizadeh M. , Safinejad A. 
Published: August 2014

AbstractPrecipitation polymerization method is a non homogeneous method in which polymer chains are separated from continuous phase as polymer particles. In this method, all polymerization reactions occur in continuous and polymer dispersed phases based on simultaneous polymerization theory. Hunkeler theory is a perfect "simultaneous polymerization" theory that predicts molecular weights and the rate of polymerization for precipitation polymerization of hydrophilic monomers. In this paper, finite moment method is used to predict features of precipitation polymerization. This model is able to predict number and weight average degree of polymerization in dispersed and continuous phases, polydispersity index (PDI) for two phases and volume fraction of primary and secondary particles. Experimental results are in agreement with the properties of dispersed phase; weight and number average degree of polymerization in the dispersed phase is more than that of degrees of polymerization in the continuous phase. The PDI of polymer formed in the dispersed phase is equal to 2 and that of PDI in the continuous phase is less than 2. Furthermore Hunkeler mathematical model is reviewed critically.
Novel acrylic copolymers: synthesis, characterization and antimicrobial studies.
Authors: Patel Hetal , Patel Mitesh , Patel Kirit , Patel Rajni 
Published: August 2014

AbstractThe monomer 2,4-dichloro phenyl acrylate (2,4-DCPA) was synthesized from 2,4-dichlorophenol and characterized by conventional methods. The homopolymers of 2,4-DCPA and its copolymers with 8-quinolinyl methacrylate (8- QMA) in different feed ratio were prepared by free radical polymerization using dimethyl formamide (DMF) as a solvent and 2,2’-azobisisobutyronitrile (AIBN) as an initiator. The resulting polymers were characterized by Infrared Spectroscopy. UV spectral data were employed to obtain the reactivity ratios of the monomers, 2,4-DCPA and 8-QMA. The results showed that 2,4-DCPA is more reactive than 8- QMA. Average molecular weights and intrinsic viscosities determined by Vapour pressure osmometer (VPO) lies in the range of 7900 to 10890 and 0.021-0.036 dl.g-1 respectively. Thermal analysis shows that thermal stability of copolymers increases with the increase of 2,4-DCPA. The copolymers also showed antimicrobial activity which increased with increase in 8-QMA content.
Influence of Electron Beam Irradiation on PP/Clay Nanocomposites Prepared by Melt Blending
Authors: Nejad Shahryar Jafari , Ahmadi Seyed Javad , Abolghasemi Hossein , Mohaddespour Ahmad 
Published: August 2014

AbstractIn this research, the melt blending technique was used to prepare various polypropylene (PP) based nanocomposites. A commercial organoclay (denoted 15A) served as the filler for PP matrix, and the maleic anhydride modified PP was used as compatibilizer. The specimens were subjected to electron beam (EB) irradiation. The purpose of the study focuses on the influences of EB irradiation on the thermal stability and mechanical properties of the nanocomposites. The morphology of the nanocomposites was studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD and SEM results showed that these nanocomposites are best described as intercalated systems. PP/Clay nanocomposites showed good thermal stability in the TGA analysis. TGA data at 500KGy showed that the EB irradiation has negative effect on thermal stability of the nanocomposites. Mechanical testing showed that the EB irradiation strongly influences the mechanical properties (tensile strength, Young’s modulus and hardness) of PP/Clay nanocomposites. The value of tensile strength decreases remarkably for all specimens with increasing irradiation dose up to about 550 KGy, but this reduction for nanocomposites with 3% clay is less than that of the pure PP/PP-g-MA blend. In higher irradiation doses, reduction in tensile strength of PP nanocomposites is less than that of the pure PP/PP-g-MA blend. Optimum irradiation dose of Young’s modulus for PP/Clay nanocomposites with 5% clay is 450 KGy. The hardness of the nanocomposites with 5% clay was found to decrease with increase in irradiation dose.
Studies of silicon-containing maleimide polymers. Part II: Synthesis and properties of poly(styrene-co-brominecontaining maleimide).
Authors: Chia-Yu Chiang , Ruey-Shi Tsai , Wei-Jye Shu 
Published: August 2014

AbstractSoluble copolymers of a series of bromine-containing (N-maleimido phenoxy) silane (BMS) monomers with styrene (St) were synthesized by radical polymerization in toluene using 2,2’-azobisisobutyronitrile (AIBN) as initiator. The comonomer reactivity ratios were calculated by the conventional Fineman-Ross and Kelen-Tüdos methods and a nonlinear least-squares Tidwell-Mortimer method. The glass transition temperatures (Tg’s) and thermal degradation of copolymers were determined by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) respectively. The introduction of silane side-chain into maleimide (MI) monomers changed the comonomer reactivity ratio with styrene from alternating to azeotropic copolymerization. The curves of Tg’s versus the different compositions of the above synthesized St-BMS copolymers matched a modified Tg’s equation as a increase in the effect of weight ratio on alternating-segment, and an S-shaped curve of deviation in comparison with the Fox’s equation. The MIsegments within these copolymers exhibited a good compatibility and, the flame retardancy of polystyrene could be enhanced via the introduction of Si/Brcontaining maleimide.
Temperature Dependent Dynamic Mechanical Properties of Hydrogenated Nitrile Butadiene Rubber and the Effect of Peroxide Cross-linkers
Authors: Likozar Blaž , Krajnc Matjaž 
Published: August 2014

AbstractThe viscoelastic behavior of hydrogenated nitrile butadiene rubber (HNBR) was studied over a range of temperatures and shear frequencies. Dynamic mechanical properties were studied and modelled using the generalized Maxwell model and the Williams-Landel-Ferry equation. A fitting algorithm was developed to provide the best agreement between the experimental data and the model results. In addition to dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) was applied. The HNBR structure was characterized by X-ray diffraction (XRD). The developed model exhibited an excellent agreement with either isothermal or dynamic experiment data, yet only up to the rubbery plateau, after which a structure ordering occurred. This was explained by the cyano group secondary bonding and consequentially the cross-linking between HNBR chains. A molecular modeling simulation was made to confirm the cross-linking. The effect of peroxide cross-linking agents in a compound resembled the one usually observed in the filler formulated compounds.
Porous 4-Vinylpyridine-Divinylbenzene Copolymers– Varying Porosity in Different Bead Sizes of a Single Batch
Authors: Malik Muhammad Arif , Naheed Riffat 
Published: August 2014

AbstractIon-exchangers, adsorbents, supported catalysts, etc, derived from porous copolymer beads are employed as medium in fine chemical separation processes. In these processes the exchange of reagents completes earlier in the smaller beads than in the larger beads in the same lot, which reduces the separation efficiency. So, it is potentially advantageous to preferentially introduce the macropores in the larger beads, as the macropores provide fast access to the reagents into the inner portions of the beads. In this study, camphor-a sublimable organic compound was employed as a diluent to create porosity in 4-vinylpyridinedivinylbenzene copolymer beads produced by o/w suspension polymerization technique. Camphor preferentially introduced macropores in the larger beads in the reaction. The results are explained on the basis of removal of diluent by sublimation phenomenon from the polymerizing droplets at a faster rate from the smaller beads as compared to the larger beads in the same batch.
Morphological features of PU/PMMA hybrid latex prepared by Miniemulsion Polymerization
Authors: Li Chien-Yu , Chiu Wen-Yen , Lee Chia-Fen 
Published: August 2014

AbstractPU/PMMA hybrid particles are synthesized by using the method of twostep miniemulsion polymerization. In the first step, PU prepolymer is synthesized by isophorone diisocyanates (IPDI) and poly(propylene glycol) (PPG) with methyl methacrylate (MMA) as a solvent. Then the oil phase, including the NCOterminated prepolymer, MMA, hexadecane (HD), a chain extender as 1,4- butanediol (BD) or bisphenol A (BisA), a cross-linking agent trimethylol propane (TMP), and a catalyst dibutyltin dilaurate (SnDBL) is dispersed in the water phase containing SDS. Then the mixtures form miniemulsion by ultrasonication. Two kinds of initiators, BPO and KPS, are applied for the polymerization of MMA. The influences of chain extenders, initiators and PU/MMA weight ratios on the morphology of PU/PMMA latex particles are investigated. Conversion of MMA is measured and discussed. Particle sizes are analyzed by dynamic lighting scattering (DLS) and transmission electron microscopy (TEM). The cross section morphology of the hybrid particles is also characterized by TEM. For BD/BPO and BD/KPS systems, when increasing the load of PU component, PU-rich phase is moved to the outside of hybrid particles. A core-shell structure can be observed. However, for BisA/KPS system, while using hydrophobic bisphenol A as chain extender of PU, the boundary of PMMA and PU phases is not clear. A more homogeneous structure of hybrid particles is obtained.
Novel rapid response clay/poly(N-isopropylacrylamide) nanocomposite hydrogels by post treatment with HCl solution
Authors: Yun Ma , Yang Liu , Yongmei Jiang , Hao Yu , Meifang Zhu 
Published: August 2014

AbstractA series of high clay content Laponite XLS/poly (N-isopropylacrylamide) (PNIPAAm) nanocomposite hydrogels (S-N gels) have been successfully prepared by in-situ ultraviolet (UV) initiated polymerization. The effects of post treatment with HCl solution on swelling/deswelling behaviour of the S-N gels have been investigated in detail. The results indicate that the Laponite XLS/PNIPAAm nanocomposite hydrogels with HCl solution post treatment (S-N-H gels) exhibit great swelling ratio and rapid deswelling response rate; much higher and faster than other reported clay/PNIPAAm nanocomposite hydrogels.
A Novel Poly(amido amine) with Methoxy Carbonyl Groups and High Charge Density: Synthesis and Nanoscopic Selfassembly with Polyanion
Authors: Chuan-bao Wu , Jian-yuan Hao , Deng Xian-mo 
Published: August 2014

AbstractA novel poly(amido amine) with methoxy carbonyl groups, high charge density and broad nitrogen profile, was synthesized from tetraethylene pentamine (TEPA) and methyl acrylate (MA), and named as PTMA. During synthesis, on one hand, double bond of MA was added with amino group of TEPA by Michael addition reaction and, on the other hand, methoxy carbonyl group of MA was nucleophilicly substituted by amino group of TEPA. There are primary, secondary, tertiary amines and amide groups in PTMA molecule. Acid base titration indicated that the polymer was protonated in the range of both pH 5.0 to pH 7.4 and pH 7.4 to pH 11, which is indicative of not only good self-assembling capability with polyanion but also desirable proton sponge effect as shown by polyethylenimine (PEI). In aqueous solution, PTMA self-assembled with weak anionic polymer, poly(acrylic acid) (PAA), to form nanoparticles. The particle size first increased and then decreased with increasing mass ratio of PTMA to PAA, which is defined as θ. At all examined θ values, self-assembling particles with diameter less than 200 nm were obtained. The UV-Vis absorbance curve of self-assembling complex solution at first day overlapped with that at seventh day, indicating that self-assembling particles were stable.
Water-Flooding Fluid Diversion Copolymeric Microsphere Prepared by Inverse Suspension Polymerization
Authors: Zhiyu Huang , Hongsheng Lu , Tailiang Zhang 
Published: August 2014

Abstract In order to enhance oil recovery in high-temperature and high-salinity oil reservoirs, the copolymeric microspheres containing acrylamide (AM), acrylonitrile (AN) and AMPS was synthesized by inverse suspension polymerization. The copolymeric microsphere was very uniform and the size could be changed according to the condition of polymerization. The lab-scale studies showed that the copolymeric microsphere exhibit good salt-tolerance and thermal-stability when immersed in 20×105 mg/L NaCl(or KCl) solution, 7500 mg/L CaCl2 (or MgCl2) solution or 2000 mg/L FeCl3 solution, respectively. The copolymeric microsphere showed satisfactory absorbency rates. The sand-pipes experiments confirmed that the average toughness index was 1.059. It could enhance the oil recovery by about 3% compared with the corresponding irregular copolymeric particle.
Analysis of Water Adsorption on Chitosan and Its Blends with Hydroxypropylcellulose
Authors: Mucha Maria , Wańkowicz Kazimierz , Balcerzak Jacek 
Published: August 2014

AbstractChitosan (CH) and hydroxypropylcellulose (HPC) adsorb water easily by hydrogen bonds formed with hydroxyl and amide groups present in their structures. Heat of adsorption is a thermodynamic parameter which is used to estimate the type of adsorbate molecule bond on a solid surface, among the others. Adsorption of water from vapour phase on chitosan, hydroxypropylcellulose and blends of both biopolymers in the form of films were carried out. Isotherms of water adsorption in the samples were described by the GAB equation. Correlations between mass fraction of chitosan in the sample (wf) and the values of GAB coefficients were obtained. From parameter c in the GAB equation mean heat of adsorption of the first monomolecular layer of water molecules E1, and pure molar heat of adsorption q were determined.
On the use of hyperbranched aramids as support of Pt nanoparticles
Authors: Monticelli Orietta , Chincarini Andrea 
Published: August 2014

AbstractA hyperbranched (HB) aromatic polyamide (aramid) synthesized from A2 (p-phenylenediamine) + B3 (trimesic acid) reactants has been used as Pt nanoparticle support. TEM measurements verified the possibility to obtain a high metallic dispersion (MD) using H2PtCl6 as metal precursor. The amount of Pt retained by the polymer support turned out to be lower than the Pd loading deposited on the same HB aramid from a different metal precursor, i.e. PdCl2, under the same exchange and reduction conditions, namely by the procedure reported in a previous paper of ours [1]. Moreover, Pt nanoparticle diameters have been found to depend on the reducing agent used. As compared to bubbling H2, NaBH4 allowed obtaining of metal particles characterized by smaller dimensions.
Comparison Of Reaction Pathway And Product Analysis For Hydroxyalkylation Of Parabanic Acid With Oxiranes And Alkylene Carbonates
Authors: Zarzyka-Niemiec Iwona 
Published: August 2014

AbstractReactions of parabanic acid (PA) with ethylene and propylene oxides and carbonates lead to oligomeric products with hydroxyalkyl groups in both cases. The parabanic acid ring undergoes scissions during reactions depending on kind of reagent and reaction conditions. In some cases the trioxoimidazolidine ring remains untouched. Using the MALDI ToF technique the product analysis was performed. The by-products were determined quantitatively by GC. The thermostability of oligomeric products was also determined.
Poly(methyl acrylate) plus Mesoporous Silica Nanohybrids: Mechanical and Thermophysical Properties
Authors: Pérez León D. , Giraldo Luis F. , Brostow Witold , López Betty L. 
Published: August 2014

AbstractA mesoporous silica MCM-48 is used as a reinforcement agent for poly(methyl acrylate) (PMA). Methyl acrylate is introduced into the mesoporous silica that has an interconnected porous structure, allowing monomer diffusion into the pores before the polymerization reaction. In order to improve the silica plus polymer adhesion and to decrease the silica agglomeration, the silanol groups of the silica are functionalized with methyl groups without decreasing significantly the pore size. The silica is characterized by nitrogen adsorption, scanning electronic microscopy (SEM) and infrared (IR) spectroscopy. The nanohybrids so obtained are analyzed by tensile testing, thermogravimetry (TGA), differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA). The highest improvement of mechanical and thermophysical properties is achieved for nanohybrids containing 5 wt. % mesoporous silica. At 10 % silica, agglomeration of the filler takes place and the dispersed phase is less effective in reinforcing the polymer matrix.