bluuebunny/crossref_metadata_2025_split huggingface dataset:
Encapsulation of silica nanoparticles by poly(methyl methacrylate-co-styrene) via emulsion polymerization using dimethylaminoethyl methacrylate
Authors: Barari Mohammad , Sharifi-Sanjani Naser 
Published: August 2014

AbstractEncapsulation of silica nanoparticles was performed by emulsion copolymerization of methyl methacrylate (MMA) and styrene (St) using dimethylaminoethyl methacrylate (DM) as an auxiliary monomer. The emulsion polymerization was performed in the presence of silica nanoparticles as the seed to obtain encapsulated silica nanoparticles with polymer content and average particle sizes ranged from 35 wt. % to 85 wt. % and 114 to 272 nm respectively. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the encapsulation of the silica nanoparticles. The influence of MMA, St and DM concentration on the coating of the silica nanoparticles was studied. It was demonstrated that DM has an important role in stabilizing the system. Transmission electron microscopy showed that coreshell structures with silica particles as core were coated with the polymer, of which the amount and morphology were influenced by the total monomer concentration and molar ratio of MMA to St. Zeta potential measurement confirmed the presence of DM on the surface of composite particles. Thermogravimetric analysis showed that the incorporation of silica in polymer matrix results in an enhancement of thermal stability in the encapsulated products. Differential scanning calorimetry studies indicated that the glass transition temperature of encapsulated particles can be either higher or lower than those of the pure terpolymer counterpart, depending on the DM content of the polymer shell. The products were also characterized by FT-IR spectroscopy.
Mechanical and thermal properties of PP/compatibilized PP/acid treated SWNTs nanocomposites: Effect of different acid treatment times
Authors: Ahangari Morteza Ghorbanzadeh , Fereidoon Abdolhosein , Saedodin Seyfolah 
Published: August 2014

AbstractIn the present work, the effect of different acid treatment times of singlewalled carbon nanotubes (SWNTs) on the mechanical and thermal properties of polypropylene (PP)/maleated polypropylene (PP-g-MA) nanocomposites was investigated. The acid treatment process was based on a mixture of concentrated sulphuric and nitric acids. The SWNTs were treated with the acid mixture for 1, 3, and 6 h. FTIR, Raman spectroscopy and TEM revealed the values of carboxylic groups, graphitization and morphology of acid treated SWNTs, respectively. The thermal and mechanical properties and the morphology of nanocomposites were investigated by tensile tests, DMTA, DSC, and SEM.
Surface modification of carbon nanofibers (CNFs) by plasma polymerization of methylmethacrylate and its effect on the properties of PMMA/CNF nanocomposites
Authors: Guadalupe Neira-Velázquez María , Ramos-de Valle Luis Francisco , Hernández-Hernández Ernesto , Zapata-González Ivan 
Published: August 2014

AbstractCarbon nanofibers (CNFs) were modified via plasma polymerization using methyl methacrylate (MMA) as monomer and used as reinforcements for polymethyl methacrylate (PMMA). Conditions of the MMA plasma process in a specially designed reactor and plasma-polymerized methyl methacrylate (PPMMA) films were studied. The study involved varying the process time at a constant plasma power of 100 W and a constant MMA flow rate (0.15 cm3 per min). Nanocomposites of PPMMA-coated CNFs and PMMA were prepared with 0.5, 1.0, 2.0, 4.0 and 8.0 %wt of treated CNFs. The effect of the MMA plasma on the CNFs was analyzed. Dispersion of the modified CNFs was evaluated in several solvents. The results confirmed a change in hydrophobicity of the treated CNFs. The inclusion of treated CNFs exhibited substantial impact on the properties of the PMMA/CNF nanocomposites. The thermal and mechanical properties of the PMMA/CNF composites were examined. It was found that the thermal stability increased by about 8% and the Young´s modulus significantly enhanced by as much as 178% when compared to PMMA with no CNFs.
Polypropylene + Polystyrene Blends with a Compatibilizer. Part 2. Tribological and Mechanical Properties
Authors: Brostow Witold , Holjevac Grguric Tamara , Olea-Mejia Oscar , Pietkiewicz Dorota , Rek Vesna 
Published: August 2014

AbstractStyrene-ethylene/butylene-styrene (SEBS) block copolymer was used as the compatibilizer for PP + PS blends. We have investigated effects of the presence of SEBS on tribological and mechanical properties; dynamic mechanical analysis (DMA) was also performed. Since the copolymer causes formation of smaller particles of the dispersed PS phase in PP matrix blends, there is improved energy transmission and dissipation resulting in higher impact strength. The SEBS additive is relatively soft and causes a decrease in stress at break but an increase in elongation at break in tensile testing. In most cases the friction of the compatibilized blends is higher although in PS-rich blends we find a decrease. Scratch testing shows a change in wear mechanisms when SEBS is added to PP/PS. In uncompatibilized blends we observe adhesive wear, with crazes formed in the middle of the wear track. A compatibilized blend shows more ductile behavior and ploughing wear.
Effects of solvents on post-irradiation grafting of styrene onto fluoropolymer films
Authors: Napoleão Geraldes Adriana , Augusto Zen Heloísa , Fernandes Parra Duclerc , Perez Ferreira Henrique , Benévolo Lugão Ademar 
Published: August 2014

AbstractDue to the interest in the development of low cost membranes with similar capabilities to Nafion®, grafting of styrene on fluorinated polymers by simultaneous irradiation and pre-irradiation methods at high temperature (higher than 50 °C) followed by sulfonation has been a process studied broadly. However, there is very little information about grafting yield at room temperature after simultaneous irradiation. Previous works reported that the surface morphology of the styrene grafts has showed an uneven profile under the studied conditions. This work aims to evaluate the grafting of styrene onto these films after simultaneous irradiation (in post-irradiation condition), using different solvent in periods until 28 days at room temperature. Films of poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) were immersed in styrene/toluene 1:4 or styrene/methanol 1:4 and then submitted to gamma radiation at 40 and 80 kGy doses. The degree of grafting (DOG) was determined gravimetrically and physical and chemical changes were evaluated by infrared spectroscopic analysis (FTIR), differential scanning calorimeter analysis (DSC), thermogravimetric analysis (TGA), and also by scanning electron microscopy (SEM). For PTFE films, the highest DOG was achieved using toluene as solvent while for PVDF films, the highest DOG was achieved with methanol. Surface images of the grafted films by SEM technique have presented a strong effect of the solvents on the films morphology. Finally, PVDF-g-PS in styrene/methanol film revealed higher DOG, although the surface showed small cavities and discontinuities. On the contrary, the surface of PTFE-g-PS in styrene/toluene presented homogeneous surface.
The state of clay dispersion in maleated polypropylene /organoclay nanocomposites via dielectric spectroscopy measurements
Authors: Wang Yeh , Huang Syh-W. , Guo Jiang-Y. 
Published: August 2014

AbstractDielectric spectroscopy is a powerful method that allows the study of dynamics of polymers in a wide frequency range. In this work, the state of clay dispersion was related to the dielectric properties of the polymer nanocomposites based on organoclay filled maleated polypropylene (PPgMA). Fully and partially exfoliated samples were prepared through powered sonication and melt blending, respectively. Though two mechanical relaxations were revealed from dynamical mechanical analysis (DMA), only a single high-temperature process resulting from interfacial polarization was observed in broadband dielectric measurements. Dielectric dispersion parameters that appear sensitive to clay loading and degree of exfoliation were identified. The nanomorphology was primarily reflected in the Maxwell-Wagner characteristic relaxation frequency value, fp, where samples with higher degree of exfoliation showed lower relaxation rate. The relaxation time constant, which is the reciprocal of 2πfp, can be correlated with mean distance of clay layer separation in the nanocomposites and therefore provides additional information on exfoliation of clay platelets. A clear evolution of the relaxation activation energy with the degree of clay dispersion was also observed. The experimental results indicated that sonicated samples with fully exfoliated clay platelets yielded the longer relaxation time and the higher activation energy compared to their partially exfoliated counterparts.
Colloidal and physicochemical characterization of proteincontaining poly(lactide-co-glycolide) (PLGA) microspheres before and after drying
Authors: Kalaji Nader , Sheibat-Othman Nida , Saadaoui Hassan , Elaissari Abdelhamid , Fessi Hatem 
Published: August 2014

AbstractIn the present work, the double emulsion (W/O/W) method was used to microencapsulate a protein model (Bovine Serum Albumin) in a biodegradable polymer poly(lactide-co-glycolide) (50:50) (PLGA). Colloidal and physicochemical characterization of PLGA based microspheres was investigated after their “crude” preparation and after drying and redispersion processes. Particle morphology and size were studied by scanning electron microscopy and by laser diffraction analysis. Electrokinetic study and colloidal stability were also studied as a function of pH and salinity of the medium. Atomic force microscopy (AFM) was used to study the surface properties. It was found that smooth microspheres were obtained after the drying process. The Atomic force microscopy results of microspheres stored for one month in water show softness and surface irregularity caused by the microspheres degradation. The colloidal stability of theses microspheres is mainly governed by repulsive electrostatic interaction due to the PLGA charge. The used amount of stabilizing agent poly(vinyl alcohol) (PVA) is low enough to ensure the sterical stabilization. Drying process has no effect on the surface properties and colloidal stability of the prepared microspheres.
Polymer concretes improved by fiber reinforcement and gamma irradiation
Authors: Martínez-Barrera Gonzalo , Martínez-Hernández Ana Laura , Velasco-Santos Carlos , Brostow Witold 
Published: August 2014

AbstractThe well-known key problem with concrete is that its compressive strength and the compression modulus are insufficient for a variety of applications. Our polymer concrete (PC) consists of an unsaturated polyester resin as the polymeric matrix, silica sand as the inorganic aggregate, plus atactic polypropylene (PP) fibers. A further property improvement can be achieved by gamma irradiation and we apply here two methods. The first method consists in irradiation of PP fibers first and then adding them to the PC. The second route consists in irradiation of PC after inclusion of PP fibers. Along both routes we have applied the radiation at dosages ranging from 5 to 150 kGy. In the second route irradiation of silica sand results in larger contact areas of surfaces with PP fibers and with the polyester resin-as seen in scanning electron microscopy. The second route provides compressive properties which is better by a factor of two or three (depending on the irradiation dose) than the first one.
Nanostructured hybrid materials obtained by UV curing and sol-gel processes involving alkoxysilane groups
Authors: Amerio Ezio , Malucelli Giulio , Sangermano Marco , Priola Aldo 
Published: August 2014

AbstractNovel hybrid organic-inorganic coatings were obtained by photopolymerization and subsequent thermally induced condensation through solgel processes. Both radical (methacrylic) and cationic (epoxy) resins were considered as precursors of the organic phase; tetraethoxysilane (TEOS) was the precursor of the inorganic phase. The effect of the presence of a coupling agent was investigated. Real-time FT-IR analysis was used for evaluating the kinetics of photopolymerization. 29Si-NMR spectroscopy was used in order to evaluate the degree of condensation of alkoxysilane groups. The results showed the prevalence of Q3 e T2 structures indicating an incomplete condensation of the alkoxysilane groups. T1 and Q1 signals are not present, thus indicating that for each Si atom, two or more alkoxysilane groups take part to the condensation reaction. FE-SEM analyses evidenced a nanometric organization of the inorganic domains in the polymer matrix. The addition of the coupling agent was found to influence the morphology of the hybrid systems. DMTA and TGA analyses revealed an increase of the Tg values and of the thermal stability by increasing the coupling agent and TEOS content.
Competing effect of shear and β-nucleating agent on the crystallization of injection-molded iPP
Authors: Zheng Guoqiang , Hao Xiaoqiong , Wang Yaming , Liu Chuntai , Zhang Qinxing , Shen Changyu , Chen Jingbo , Peng Xiangfang 
Published: August 2014

AbstractIn this study, crystallization at different depth in the injection-molded iPP, filled with β-nucleating agent (β-NA), was investigated. According to WAXD result, one observes that the fraction of β-crystals unevenly distributes along the depth of the injection-molded parts. For iPP with lower content of β- NA, larger amount of β-crystals near the surface is shear induced; meanwhile, for the parts with higher content of β-NA, larger amount of β crystals away from the surface is β-NA induced. From the results, it could be suggested that the traditional role of nucleation agent, i.e., heterogeneous nucleation, under complex thermo-mechanical conditions during injection molding, might be suppressed.
Synthesis and property studies of oligomer obtained from the reaction of 4-vinylbenzocyclobutene and styrene with divinyl tetramethyl disiloxane-bisbenzocyclobutene
Authors: Xu Yewei , Zhu Fanghua , Xie Liqin , Yang Junxiao , Zhang Lin , Xie Rugang 
Published: August 2014

AbstractRadical copolymerization of 4-vinylbenzocyclobutene (VBCB) with styrene (St) afforded the copolymer (4-vinylbenzocyclobutene-co-styrene) (VBCBSt). Reaction of VBCB-St and divinyl tetramethyl disiloxane-bisbenzocyclobutene (DVSBCB) gave the oligomer (VBCB-St-DVSBCB), which was subsequently subjected to the cure reaction. The structures of VBCB-St and oligomer (VBCB-St- DVSBCB) were characterized by FTIR and 1H NMR, which are in agreement with the proposed structures. Molecular weights of the synthesized polymers were estimated by gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) showed that VBCB-St exhibited glass transition temperature (Tg > 95 °C) however it is not the case for the oligomers (VBCB-St-DVSBCB). TG measurements indicated that the polymers had the good thermal stability with decomposition temperatures (TD > 370 °C). The polymer resin possessed good film planarization in the AFM images and the process of oligomer curing on a wafer without fusion and flow. These results indicated that the oligomer (VBCB-St- DVSBCB) is a promising film material with a relatively low cost.
Variable surface properties of PTFE foils
Authors: Švorčík Václav , Řezníčková Alena , Kolská Zdenka , Slepička Petr , Hnatowicz Vladimír 
Published: August 2014

AbstractSurface properties of commercially available polytetrafluoroethylene (PTFE) foils of different thicknesses were examined using three different methods: AFM, study of a electrokinetical ζ-potential and measurement of a contact angle by goniometry. It was found that the front and back sides of the foils exhibit different surface morphology and roughness, different values of the ζ-potential and contact angle. The contact angle and the ζ-potential are decreasing functions of the foil thickness.
Synthesis and properties of poly(arylene imino) containing fluorenone group (PIKF)
Authors: Zhang Lin , Chang Guanjun , Xu Zhen , Miao Lubin , Xu Yi , Hu Hongju , Luo Xuan , Lin Runxiong 
Published: August 2014

AbstractA series of novel poly(arylene imino) containing fluorenone group (PIKF) have been synthesized via palladium-catalyzed polycondensation. The thermal properties of PIKF are detected by thermal behavior (TG) and differential scanning calorimetry (DSC). UV-vis absorption spectra, photoluminescence are investigated. PIKF exhibit good thermal stability and high Tgs(>200 °C ). The optical properties of PIKF show that PIKF are interesting materials for further investigations to be presented as possible candidates for use as an electron transport layer (n-type) in multilayer LEDs.
The morphology and non-isothermal crystallization kinetics of PET/BaSO4 hybrid fibre
Authors: Gong Maoming , Zheng Guo , Xu Jinyun , Sun Yu 
Published: August 2014

AbstractThe addition of BaSO4 whose mass fraction was less than 0.052%, could improve the mechanical property and thermal stability of the fibre apparently. It was found that, the smoothness of the hybrid fibre was changed by BaSO4 appreciably, though allowable in actual production; The BaSO4 did not obviously affect the crystallization index ( a ) and the relative degree of crystallization. With the content of BaSO4 increasing, the crystallization rate firstly became smaller slightly and then restored to the original level at the primary crystallization stage, but the crystallization rate revealed a small fluctuation at the secondary crystallization stage. In addition, the Ozawa equation was fit for pure PET well, and the Mo equation was fit for pure and hybrid PET.
Flow induced crystallization of LDPE nanocomposites: A rheological and morphological characterization
Authors: Azzurri Fiorenza , Stagnaro Paola , Conzatti Lucia , Cavallo Dario , Repetto Luca , Scatto Marco , Andreotti Leonardo , Coiai Serena 
Published: August 2014

AbstractThe flow induced crystallization behaviour of a LDPE:PE-g-MA:D72T 90:9:1 nanocomposite has been investigated by in-situ Rheo-SALS technique and data have been compared with those obtained from a reference LDPE:PE-g-MA 90:9 sample. Rheo SALS results, confirming thermal analysis findings, indicate that under mild shear flow fields the organoclay exhibits a negligible nucleating effect. Both nucleation density and, as a consequence, crystallization rate, are not appreciably affected by the application of external flow field for both the examined systems, revealing that no evident synergic effects between the organoclay and the shear flow are present. On the other hand, Rheo SALS analysis indicates that the nanocomposite submitted to flow exhibits a higher level of crystal orientation. TEM morphological analyses support this observation suggesting that the orientation of the nanofiller along the flow direction templates the growth of oriented crystals.
Unconventional microstructure of maleic anhydride copolymers in condensed and dissolved states
Authors: Filimoshkin Anatoliy , Berezina Elena , Manzhay Vladimir , Kuchevskaya Alexandra , Ivanov Alexander 
Published: August 2014

AbstractA novel type of protopropic tautomerism proceeds in macromolecules of binary copolymers of maleic anhydride (MA) with vinyl acetate (VA) and vinyl chloride (VC) giving rise to spontaneous formation of dynamic micro structural heterogeneity which consists of several tautomeric forms: succinic anhydride rings, VC and VA units along with unforeseen enol (en) and dienol (den) furan derivatives (33 mol%). The arising hydrogen bonds close the ring generating quasi-aromatic structures simultaneously. The en and den tautomers form charge-transfer complexes with O- and N- nucleophiles. Mechanism of MA radical copolymerization with VC including polyaddition of molecular monomer complexes both in the ground state and in their biradical resonance structures has been proposed. The investigations were carried out using infrared spectroscopy (IR-), electron, nuclear magnetic resonance spectroscopy (1Н and 13С NMR), differential thermo analysis, mathematical microstructure modelling etc.
Microwave-assisted Wurtz coupling of methylphenyldichlorosilane in solvent-free conditions
Authors: Sacarescu Gabriela , Simionescu Mihaela , Harabagiu Valeria , Sacarescu Liviu 
Published: August 2014

AbstractThis communication describes the synthesis of polymethylphenylsilane by the microwave-assisted coupling of methylphenyldichlorosilane using metallic sodium in solvent free conditions. The instant heating melts the sodium particles within the liquid methylphenyldichlorosilane and the polymerization reaction is achieved in minutes with total consumption of the monomer. The process is carried out in a high performance microwave reactor using the closed vessel operating facility which ensures control of the reaction parameters and highly reproducible results.
Effects of organoclay on morphology and mechanical properties in acrylonitrile-butadiene-styrene/polyamide 6/ organoclay ternary nanocomposites
Authors: Yan Wei , Qin Shuhao , Guo, Jianbing , He Min , Zhang Minmin , Yu Jie 
Published: August 2014

AbstractIn this article, polyamide 6(PA6)/organoclay masterbatch were prepared by melt mixing, and then acrylonitrile-butadiene-styrene(ABS)/polyamide 6(PA6)(70/30,w/w) nanocomposites were prepared by the melt mixing of PA6, ABS and organoclay. The effect of organoclay platelets on morphology and mechanical properties of ABS/PA6/organoclay ternary nanocomposites had been investigated by wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM), scanning electron microscopy (SEM) and mechanical properties testing. Morphology analysis revealed that organoclay platelets were selectively dispersed and exfoliated in PA6 phase, but some were located in interface of PA6 and ABS phase. The droplet size of PA6 dispersed phase were gradually reduced less than 4 phr organoclay, then the dispersed domain size became unchanged with the addition of various organoclay. It suggested the organoclay can compatibilize the ABS/PA6 blend nanocomposite. Moreover, the flexural strength and modulus increase with increasing organoclay content, but the tensile strength became maximal at 3 phr organoclay. The organoclay has no effect on impact strength of ABS/PA6 blend nanocomposite.
Synthesis and characterization of a novel wound dressing by PVP/ PAANa/chitosan with semi-interpenetrating polymer network structure
Authors: Wu Ying , Yang Qing , Gi Yali , Zhang Yueting 
Published: August 2014

AbstractA novel hydrogel wound dressing with semi-interpenetrating polymer network structure (semi-IPN) was prepared by radical polymerization of acrylic acid with potassium persulfate (K2S2O8) as initiator and N, N'-methylenebisacrylamide (MBA) as cross-linking agent in the presence of chitosan (CTS) and polyvinyl pyrrolidone (PVP). Hydrogels were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM displayed semi- IPN hydrogels' creased surface with some scale-like wrinkles, thus improving the absorptive capability which has been considered as a most important characteristic of wound dressings. It was found that the content of cross-linking agent and the mass ratio of PVP and CTS had much influence on the mechanical properties of the hydrogel, varying from brittle plastics to elastomer due to the different degrees of cross linking. Since tensile strength is partly in inverse ratio to the hydrogel absorbent capability, the article offers an analysis of varying material proportion in order to obtain an optimum properties of the hydrogel wound dressing .