bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid chromatography at the critical adsorption point (LCCAP) of high molecular weight polystyrene: pushing back the limits of reduced sample recovery
Authors: Favier Arnaud , Petit Christelle , Beaudoin Emmanuel , Bertin Denis
Published: August 2014

Low sample recovery may be one limiting parameter in Liquid Chromatography at the Critical Adsorption Point (LC-CAP) of high molecular weight polymers. We aimed at playing on different experimental parameters in LCCAP of high molecular weight polystyrenes (PS) in order to reach maximum sample recovery. The nature of adsorli and desorli, the temperature, the nature of the column surface and the pore size were studied as regard to their influence on sample recovery. Evaporative Light Scattering was used for detection. We demonstrated that almost all experimental parameters are correlated and that in any case, the lower the adsorli content, the better the sample recovery. Molecular weight limit for good sample recovery could be pushed from as low as 100 000 for the THF/cyclohexane mixture and silica columns to above 1 000 000 for the DCM/n-hexane mixture and amino-silica columns.
Track PVB membrane based on irradiation with high energy protons
Authors: Shadman Muhammad , Ziaie Farhood , Yeganegi Saeid , Niazi Behrooz , Ziaee Farshid , Majdabadi Abbas
Published: August 2014

One of the methods of polymeric material modification is based on the irradiation with accelerated ions. Chemical etching of ion tracks in polymers is a method which is widely used in the fabrication of micro/nano-structures with predetermined characteristics. For the present study polyvinyl butyral (PVB) porous membrane was prepared by track-etching technique. Commercially available PVB film was irradiated by 30 MeV energy protons to form latent tracks, and then etched chemically by potassium hydroxide (KOH) with the different normalities. The etching rate of PVB was related to the concentration of etching reagent, temperature and time. The porous size and shape were investigated by scanning electron microscope (SEM) after and before etching. Relationships in between the etching rate and the etching parameters were established from experimental data, and can be used to control the pore size of PVB track-etch membrane. The Pore sizes and their structures were evaluated by optical microscope (OM) and scanning electron microscope (SEM). The results have shown the micro/nano-pores formation in the PVB films. The physico-chemical properties of the irradiated samples were investigated and compared with the un-irradiated one using the FTIR and DSC and DTG systems, as well.
Alginate-based superabsorbent hydrogels composed of carboxylic acid-amine interaction: preparation and characterization
Authors: Yoshimura Toshio , Matsunaga Miyuki , Fujioka Rumiko
Published: August 2014

Preparation of superabsorbent hydrogels based on sodium alginate was investigated by mixing aqueous sodium alginate solution and aqueous multivalent amine (ethylenediamine, L-lysine, chitosan) solution, followed by HCl addition. After precipitation in methanol, vacuum drying, and pulverization with mixer, granule products with acid-base interaction were obtained. The preparation condition was investigated by changing the feed amount of amine compound. Among those examined, the highest water absorbency was obtained with the sample for chitosan feed ratio to sodium alginate of 100 mol%, reaching 410 g/g in pure water, 100 g/g in 0.9 % solution, and 80 g/g in 3.5 % NaCl solution. Hydrogels in the present study exhibited good biodegradability irrespective of amine compound.
Synthesis and characterization of novel cyanofunctionalized poly(aryl ether ketone)s
Authors: Zhang Yunhe , Ren Dianfu , Guan Shaowei , Na Ying , Wang Guibin , Jiang Zhenhua
Published: August 2014

A series of cyanophenyl-substituted poly(aryl ether ketone)s (PAEKs) have been successfully synthesized from two new bisphenol monomers, (3,4- dicyano) phenylhydroquinone and (4-cyano) phenylhydroquinone respectively, and the thermal behaviour and the solubility have been characterized. These polymers exhibited high glass transition temperatures and excellent thermal stability. The glass transition temperatures ranged from 173 to 217 oC, and 5% weight-loss temperatures were above 470 oC. The solubilities of these polymers have been remarkably improved in common organic solvents over PEEK and PEN. Some polymers formed transparent, strong, and flexible films, with tensile strength of 106.5-125.2 MPa, Young’s moduli of 2.68-3.20 GPa, and elongations at break of 9- 16 %.
Effects of kaolin and maleic anhydride contents on melt elasticity and flexural behaviour of polypropylene/kaolin and unplasticised poly(vinyl chloride)/kaolin composites
Authors: Ariffin A. , Ariff Z.M. , Jikan S.S.
Published: August 2014

Polypropylene/kaolin and unplasticised poly(vinyl chloride)/kaolin composites were prepared by directly melt mixing polypropylene (PP) and unplasticised poly(vinyl chloride) (UPVC) with maleic anhydride (MAH) and low cost kaolin via in situ extrusion process. The influences of kaolin particles and MAH in PP and UPVC matrix were discussed through investigating the flexural and morphological properties of filled PP and UPVC composites. The extrudates obtained from the extrusion process were carefully collected in order to investigate the elastic properties (extrudate swell and melt fracture). Results revealed that the above mentioned properties are strongly dependent on the presences of kaolin and MAH in both composite systems. Observation on scanning electron microscopy (SEM) analysis showed that the kaolin books (stacks of kaolin particles) were successfully delaminated thus lead to a well dispersed of kaolin particles in PP and UPVC matrix.
Effects of carbon nanofibers on the crystallization behavior of polyethylene oxide
Authors: Adhikari R. , Lozano K.
Published: August 2014

Differential scanning calorimetry (DSC) was used to investigate the crystallization behavior of polyethylene oxide (PEO) and carbon nanofiber (CNF) filled PEO systems under non-isothermal experimental conditions. The dispersion and distribution of CNF of the composites were studied using scanning electron microscopy. Studies showed the uniform segregation of CNFs in PEO. Different crystallization kinetic models (the modified Avrami equation and the combined approach of Avrami and Ozawa) were used to study the dependence of crystal nucleation on the filler content. Analysis showed that inclusion of CNF to PEO retards the crystallization of PEO at all CNF loading under study
Non-isothermal crystallization kinetics of isotactic polypropylene nucleated with nucleating agent bicyclic [2,2,1] heptane di-carboxylate
Authors: Zhang Yue-fei , Li Xun , Wei Xian-shan
Published: August 2014

Bicyclic [2,2,1] heptane di-carboxylate (commercial product name: HPN- 68) is a novel nucleating agent with high nucleation efficiency for isotactic polypropylene (iPP). In this paper, the non-isothermal crystallization kinetics of virgin iPP and iPP nucleated with HPN-68 were investigated by means of a differential scanning calorimeter (DSC).The Caze method was used to analyze the non-isothermal crystallization kinetics. The results show that addition of HPN-68 can increase the crystallization peak temperature (Tp) of iPP greatly under the same cooling rate. Under non-isothermal conditions, the addition of HPN-68 changes the spherulite growth pattern of iPP. For virgin iPP, the growth pattern is mainly spontaneous nucleation followed by three-dimensional spherulite growth, while for iPP nucleated with HPN-68, the growth pattern is mainly heterogeneous nucleation followed by three-dimensional spherulite growth.
Preparation and swelling behavior of pH-sensitive and saltresistant amphoteric semi-IPNs hydrogels based on starch phosphate and poly[2-[(methacryloyloxy) ethyl] trimethylammonium] chloride
Authors: Chen Xiaozhen , Xu Shimei , Feng Shun , Wang Jide , Li Xin
Published: August 2014

A novel amphoteric hydrogel with semi-interpenetrating polymer networks (semi-IPNs), was prepared by entrapping linear poly[2-[(methacryloyloxy) ethyl]trimethylammonium] chloride (PDMC) into lightly crosslinked starch phosphate- graft-acrylic acid (St-OPO3-g-AA) network in aqueous solution. The influences including the degree of substitution (DS) of starch phosphate, the doses of crosslinker, AA and PDMC were investigated with respect to the swelling capacity. The swelling capacity of hydrogel reached 2016 g/g in deionized water and 121 g/g in 0.9 wt% NaCl solutions, respectively. The swelling behaviors of hydrogel in various salt solutions and different pH buffer solutions were discussed. The amphoteric semi-IPN hydrogels exhibited pH-sensitivity and salt-resistance.
Physicochemical properties and molecular weight characterisation of porcine dermal collagen digested under varying conditions with clostridium histolytic collagenase
Authors: Yeh Jen-taut , Chang Haw-jer , Xiao Li-fang , Yang Li , Zhu Ping , Huang Guo-xian , Yao Wei-Hua
Published: August 2014

Porcine dermal collagen is successfully digested by clostridium histolyticun collagenases (CHC) at varying compositions and conditions. Collagen fragments thus prepared, with significantly low molecular weight but visible denaturation temperatures and/or triple helix structures, may be useful for clinical applications. As evidenced by Sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) and gel permeation chromatography (GPC) analyses, relatively high molecular weights of α1, α2 subunit, β1 ,β2 dimmers and γ trimmers of the collagen fragments gradually disappear as their incubation temperature and/or time values increase. The time values corresponding to the disappearance of sigmoid plots in the denaturation curves, denaturation endotherm in DSC thermograms and γ bands in SDS-PAGE patterns of digested collagen specimens are the same and reduce significantly as their incubation temperatures increase. Fourier transform infra-red analyses results suggest that the percentages of preserved triple helix structures present in collagen molecules of digested collagen specimens also reduce significantly with increasing the incubation temperature and time values. Possible reasons accounting for the degradation, denaturation and physicochemical properties of digested porcine dermal collagens are explored in this study.
Study on the effect of processing conditions on the mechanical properties of PP/PC/SEBS ternary blends using Taguchi experimental analysis
Authors: Moini Jazani O. , Arefazar A. , Beheshty M.H.
Published: August 2014

In this study, nine ternary polymer blends based on polypropylene (PP)/polycarbonate (PC)/styrene-ethylene-butylene-styrene triblock copolymer (SEBS) with the same compositions (70%wt PP, 15%wt PC, 7.5%wt SEBS and 7.5%wt maleic-anhydride grafted SEBS (SEBS-g-MAH) as a compatibilizer) are prepared using twin screw extruder at different levels of die temperature (235-245- 255 °C), screw speed (70-100-130rpm) and blending sequence (M1-M2-M3) . In M1 procedure, all of the components are dry blended and extruded simultaneously using Brabender twin-screw extruder. In M2 procedure, PC, SEBS, and SEBS-g- MAH minor phases are first pre-blended in twin screw extruder and after granulating are added to PP continuous phase in twin screw extruder. Consequently, in M3 procedure, PP and SEBS-g-MAH are first pre-blended and then are extruded with other components. The influence of these parameters as processing conditions on mechanical properties of PP/PC/SEBS ternary blends is investigated using L9 Taghuchi experimental design. The responding variables are impact strength and tensile properties (young modulus and yield stress) which are influenced by the morphology of ternary blend and the results are used to perform the analysis of variance (ANOVA). It is shown that the resulted morphology, tensile and impact strength are influenced by extrusion variables. Additionally the optimum processing conditions of ternary PP/PC/SEBS blends from Taguchi analysis was achieved.
The properties of sericin/poly(vinyl alcohol) films modified by boric acid
Authors: Wang Qun , Qi Lu
Published: August 2014

A group of films mainly composed of sericin and poly(vinyl alcohol) (PVA), using boric acid (BA) as a modifier, were prepared by a technique of solution casting. In this work, the effect of BA and sericin on the mechanical properties and water resistance of the films was analyzed, the interior morphology of the films were described by a scanning electron microscopy (SEM), the thermal stability of the films was characterized by differential scanning calorimetry (DSC), and the reaction mechanism was proposed according to the previous literature and the test of Fourier transform infrared spectrum (FTIR). Results indicated that, the properties of the membrane were the functions of the blend ratio of sercin to PVA and the content of BA. The use of BA increased the tensile strength, improved the water resistance and the thermal stability, and varied the interior morphology of the films. The content of sericin greatly influenced the combination of properties of the films, especially the mechanical properties, interior morphology, thermal stability, and water resistance reducing with the increasing of sericin content. The films have potential to be used in materials, such as skin-care coatings for beauty, percutaneous drug delivery systems for exterior intact skin, due to the characteristics of the components and the good mechanical properties of the films.
Synthesis and thermal stability of star polymer with eight arms using polyhedral oligomeric silsesquioxane as a core
Authors: Liu Lei , Wang Wenping , Guo Xianran
Published: August 2014

A Polyhedral oligomeric silsesquioxane (POSS) containing eight 3- chloropropyl groups was synthesized and incorporated into poly(methyl methacrylates) to form star polymer. First, octa(3-chloropropyl) POSS [(ClCH2CH2CH2)8Si8O12] was prepared by hydrolysis and condensation of 3- chloropropyltriethoxysilane, and then two star-shaped POSS/PMMA composites with different POSS content was synthesized at 110 °C, using octa(3-chloropropyl) POSS as an multifunctional initiator, CuCl and 2-2’ bipyridine (Bpy) as catalyst system. The structures of octa(3-chloropropyl) POSS and star-shaped POSS/PMMA composite were characterized by analytical methods including FTIR, NMR, GPC and XRD, with results showing that POSS molecule was successfully formed which accorded well with the reported work and was dispersed into PMMA matrix evenly by atom transfer radical polymerization method. The TGA results indicated that synthetic POSS molecule possessed good thermal stability, and the thermal stability of POSS/PMMA composite enhanced with the increase of POSS content, which is due to the incorporation of inorganic POSS molecule
Preparation of submicron ion-exchange fibers and application in copper ions removal from aqueous solutions
Authors: Feng Shuqin , Shen Xinyuan
Published: August 2014

The submicron ion-exchange fibers (IEF) of polystyrene (PS) and styrene-isoprene-styrene block copolymer (SIS) blends (80/20, w/w) obtained by electrospinning technology were further sulfonated with sulfuric acid to produce strong acidic cation ion exchange fibers. Scanning electron microscopy (SEM) images showed that there were obvious increase in the diameters, scratches, cracks, and micro-pores on the rough IEF surface. Fourier transform infrared (FTIR) spectroscopy analysis showed there were many sulfonated acid groups introduced onto the benzene wreath of styrene. The maximum adsorption capacity and the adsorption rate of copper ions were carried out and their removal rate determined by spectrophotometry. The results of the adsorption for copper ions showed that submicron IEF from PS/SIS blends with a high porosity (85%) and a high specific surface (760 m2/g) possess a rapid adsorption rate and a high ion adsorption amount (305.9 mmg/g). This high adsorption capacity suggests that the IEF can be efficiently applied to filter out toxic metal ions, and has excellent efficiency to remove copper ions from aqueous solution.
Preparation and characterization of hydroxybutyl chitosan
Authors: Zhu Bin , Wei Changzheng , Hou Chunlin , Gu Qisheng , Chen Dajun
Published: August 2014

The insolubility in neutral condition is a major problem that confronts the further development of processing and uses of chitosan. Special emphasis has been put on the chemical modification of chitosan to explore its full potential. Studies on these methods are also encouraging and many kinds of water-soluble and alcohol-soluble derivatives have appeared. In this article, hydroxybutyl chitosan, a new type of thermosensitive polymer, was prepared through the chemical modification of 1,2-epoxybutane. Hydroxybutyl chitosan solution underwent sol/gel phase transition at a certain temperature lower than 20 °C, however, at high temperature, hydroxybutyl chitosan can form hydrogel with a certain mechanical strength. Hydroxybutyl chitosan could be an ideal themosensitive material applied in drug delivery system, tissue engineering and other biomedical fields.
Characterization of orientation in polyethylene by scratch testing
Authors: Vigueras-Santiago Enrique , Hernández-López Susana , Camacho- López Marco A. , Brostow Witold
Published: August 2014

Microscratch experiments were performed to evaluate effects of uniaxial stretching by 200 % in low density polyethylene (LDPE) along parallel and perpendicular directions with respect to stretching. Penetration depth, healing depth and viscoelastic recovery have been determined. Clear orientation effects are seen. The direction parallel to the extension axis shows strong resistance to scratching and also the highest recovery (a memory effect). Unoriented material exhibits behavior intermediate between that of oriented samples in parallel and perpendicular directions. The sliding wear was determined by multiple scratching along the same groove and here also was found orientation dependence. Polarized micro-Raman experiments on the oriented LDPE samples were carried out. Since scratching and sliding wear results are strongly affected by polymer orientation, one can use both kinds of tests as a measure of orientation - and also to vary orientation to control tribological properties.
Effect of PVP content on the quaternized polysulfone in blend membranes
Authors: Huang Aibin , Xiao Chaobo
Published: August 2014

A series of blend membranes of quaternized polysulfone (QPSF) and polyvinylpyrrolidone (PVP) were obtained by a novel method. The procedure of quaternization of chloromethylated polysulfone and the process of blend are synchronous. These blend membranes, prepared with quaternized polysulfone (QPSF) and polyvinylpyrrolidone (PVP), were characterized by FTIR, X-ray diffraction (XRD), tensile tests and scanning electron microscopy (SEM). The degrees of swelling of the membranes in some solvent were also measured. The ionic resistances of the membranes were measured too. With the increasing of PVP content, the properties of the membranes have changed. The tensile strength of blend membrane dropped while the degrees of swelling of the membranes in water increased. The ionic resistance of the membrane dropped with the PVP content increasing in blend membranes. The polyvinylpyrrolidone (PVP) has good compatibility with quaternized polysulfone in blend membranes.
Research of mechanical strength enhanced fibrin-PLGA hybrid scaffold with its effect on proliferation of rMSC
Authors: Zheng Qing , Zhao Xiaojun
Published: August 2014

As a tissue engineering biomaterial, fibrin possesses outstanding biodegradable and biocompatible features except for its weak mechanical strength which limits its ranges of further application. In this study, hybrid scaffold was obtained by mixed fibrinogen and thrombin solution homogeneously in the presence of various amounts (0, 1, 2, and 4 mg, respectively) of non-woven fabric of PLGA fiber through traditional freeze-dried method to improve the mechanical strength while keeping its biological characters. The observation by scanning electron microscopy (SEM) showed that all the fibrin sponges have porous and interconnected pore structure, irrespective of the amount of PLGA fiber incorporated. In the measurement of the scaffold shrinkage, the percent of shrinkage of fibrin sponge incorporating PLGA fiber decreased when the amount of PLGA fiber incorporated increased compared with the fibrin sponge without PLGA fiber. The compression test suggested that compression modulus of PLGA fiber incorporated fibrin sponge significantly increased against the fibrin sponge without PLGA fiber; the incorporation of PLGA fiber enabled the mechanical strength of fibrin sponge to be effectively enhanced. Rat mesenchymal stem cells (rMSCs), which is of high potential to induce tissue regeneration, was selected to seed and culture in the fibrin scaffolds with or without PLGA fiber, and the number of rMSC was tested by DNA assay and calculated to examine which sponge was more favourable for rMSC to proliferate. The results reveal that the incorporation of PLGA fiber reinforced the fibrin scaffolds and maintained their intraspace. MSCs proliferated in fibrin scaffold with PLGA fiber was obviously on average more than that without PLGA fiber in vitro.
Combustion and thermal behaviors of the novel UV-cured intumescent flame retardant coatings containing phosphorus and nitrogen
Authors: Xing WeiYi , Song Lei , Hu Yuan , Lv Xiaoqi , Wang Xin
Published: August 2014

Phosphorus-containing tri(acryloyloxyethyl) phosphate (TAEP) was blended with triglycidyl isocyanurate acrylate (TGICA) in different ratios to obtain a series of UV curable intumescent flame retardant resins. The fire properties of the cured films were characterized by limited oxygen index (LOI), UL 94 and Cone Calorimeter. A distinct synergistic effect was found between TAEP and TGICA. The sample TAEP2 had the highest LOI (44) value among all resins. The cone calorimeter results showed that the sample TAEP2 had the lowest peak heat release rate (297 KW/M2). The thermal degradation was monitored by thermogravimetric analysis (TGA) and real-time Fourier transform infrared spectroscopy (RT-FTIR). The degradation mechanism is suggested in which the phosphate group in TAEP first degraded to form poly(phosphoric acid)s, which further catalyzed the degradation of the material to form char with emission of nitrogen volatiles from TGICA, leading to the formation of expanding char.
Synthesis and characterization of α-butyl-ω-{3-[(2,2- dihydroxymethyl)-propionyloxy]}propyl polydimethyl siloxane
Authors: Zhang Meng , Wu Yuanjuan , Zhang Qingsi , Li Tianduo
Published: August 2014

A novel polydimethylsiloxane containing two primary hydroxyl groups at one single chain end was synthesized by five-step reactions which included esterification, hydroxyl protection, anionic ring-opening polymerization, hydrosilylation and deprotection. The prepared compounds in each step were characterized. The results showed that at each step synthesis was successfully carried out and objective products could be achieved.
A convenient method to acquire third-order NLO materials by ATRP
Authors: Wu Jiang , Xu Qingfeng , Xia Xuewei , Li Najun , Lu Jianmei , Ge Jianfeng , Wang Lihua
Published: August 2014

A third-order nonlinear optical (NLO)-active initiator (NA3PH) was synthesized to prepare a NLO-active polystyrene (NA3PH-PSt) via atom transfer radical polymerization (ATRP). The polymerization initiated by NA3PH was studied and the third-order NLO properties of the obtained NA3PH-PSt were investigated by Z-scan technique in comparison with NA3PH. Results show that the endfunctionalized polystyrene possesses third-order nonlinear optical susceptibilities (10-11esu) close to NA3PH. In addition, NA3PH-PSt has good thermal stability and solubility, which holds potential for further application in NLO devices.
Synthesis of long chain semiaromatic polyamides based on decanediamine
Authors: Wang Wenzhi , Li Ruixue , Liu Baoyu , Zhang Yonghua
Published: August 2014

Long chain semiaromatic polyamides were synthesized by the reactions of decanediamine with various aromatic diacids, and characterized by Fourier transform infrared spectrum (FT-IR) and nuclear magnetic resonance (1H-NMR). The thermal behaviours were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The solubility, dynamic mechanical, physical and mechanical properties of the polyamides were also investigated. The resultant polyamides have intrinsic viscosity ranging from 1.7 dL/g to 2.1 dL/g. Their melting temperatures range from 305 °C to 343 °C, and the glass transition temperatures fall in the range of 125 °C - 130 °C. The tensile strength of the polyamides is above 100 MPa.
Poly(α-hydroxyacids) in biomedical applications: synthesis and properties of lactic acid polymers
Authors: Lipsa Rodica , Tudorachi Nita , Vasile Cornelia
Published: August 2014

Poly( -hydroxy acids), especially poly(glycolic acid) (PGA), poly(lactic acid) (PLA) and their copolymers poly(lactic-co-glycolic acid) (PLGA) are novel class of commodity polymers, also used in biomedical applications. They can be synthesized with a controlled biodegradation rate and are biocompatible, bioresorbable and approved by US Food and Drug Administration (US FDA) for clinical use. Lactic acid polymers are developed in medicine (sutures, implants, orthopaedics, tissue engineering), pharmacy (controlled drug delivery systems) as well as in packaging, agriculture (mulch films, seed preservation), food applications, etc. The paper reviews recent literature data concerning lactic acid polymers synthesis (polycondensation, ring opening polymerization), physical (thermophysical, solubility, miscibility), mechanical properties, degradation behaviour, emphasizing on the poly(α -hydroxyacids) and lactic acid polymers applications in medicine and pharmacy.
PAN monofilament in nanoscale: a novel approach
Authors: Sadrjahani M. , Hoseini S.A. , Mottaghitalab V. , Haghi A.K.
Published: August 2014

A novel electrospinning setup was employed for producing aligned polyacrylonitrile (PAN) monofilament in nanoscale. Unlike conventional method, the PAN monofilaments is collected using a rotating drum with various linear speed from bulk of nanofibers. it originates from two syringe infusion pumps contain 14wt% PAN/DMF solution which passes through two separate high voltage electric field. Various collecting drum speed were examined to clarify its effect on degree of alignment, internal structure and mechanical properties. Image process technique used to illustrate the best degree of alignment for nano-monofilament collected at take up velocity of 59.5 m/min. The amount of Crystallization Index (C.I) and orientation parameter calculated respectively from FTIR spectra and Raman spectra also supports the results demonstrated by image processing techniques. The ultimate strength and elastic modulus of nano-monofilament bundles increase with increase of take up velocity. They approach respectively to a maximum of 73.7 MPa and 4.2 GPa at take up velocity of 59.5 m/min. Results acquired by differential scanning calorimetry (DSC) show no significant effect on glass transition temperature with increasing take up velocity. However, minimum value of evolved heat caused by chemical reaction was obtained at surface speed of 59.5 m/min.
Crystallization kinetics and miscibility of blends of polyhydroxybutyrate (PHB) with ethylene vinyl acetate copolymers (EVA)
Authors: El-Taweel S. H. , Stoll B. , Schick C.
Published: August 2014

A series of ethylene vinyl acetate random copolymer EVA, with vinyl acetate (VA) varied from 9 to 91m%, was investigated by differential scanning calorimetry DSC and polarized optical microscopy. Biodegradable polymer blends of polyhydroxybutyrate PHB and EVA, having VA in EVA in range from 40m% till 91m%, were prepared by film casting from a chloroform solution. The miscibility and crystallization behavior of these blends were investigated. The isothermal crystallization behaviors of PHB and PHB/EVA blends are discussed in terms of the half time of crystallization t1/2. Experimental results indicated that blends of PHB/ EVA91 are completely miscible blend in the entire (0 to 100 m%) compositional ranges. Blends PHB/ EVA, for VA varied from 40 till 70 m% are immiscible as evidenced by the existence of unchanged composition independent glass transition temperatures (Tg), crystallization and melting behavior. The isothermal crystallization of PHB blends was investigated from room temperature till 130 °C. 80 °C was found to be the best temperature for comparison of different blends. At 80 °C t1/2 strongly depends on the content of VA in PHB/EVA blend, mainly due to differences in miscibility as well as due to differences in segmental mobility as identified by differences in glass transition temperature. Since both components in PHB/EVA80, pure PHB and pure EVA80, have glass transition temperatures close to 0 °C, it is difficult to decide its miscibility from Tg. However from the strong dependence of the value of crystallization half time t1/2 of PHB/EVA80 on blend composition, it was possible to reasonably infer that PHB/EVA80 is partially miscible.
Predicting the Young’s modulus of intercalated and exfoliated polymer/clay nanocomposites
Authors: Molajavadi Vadoud , Garmabi Hamid
Published: August 2014

The Halpin-Tsai equations were used for the composites with low level content of reinforcements, which contain lamellar shape, high modulus and high aspect ratio. These characteristics of reinforcements were taken into consideration to simplify the Halpin-Tsai equations. The effect of different parameters on the longitudinal Young’s modulus of well aligned polymer/clay nanocomposites was investigated for both exfoliated and intercalated microstructures. It was shown that the applied simplification had negligible effect on the prediction of the Halpin-Tsai model. For the intercalated structures with a high number of platelets per stack (n), increase in the gallery spacing did not influence the predicted modulus values. In an intercalated structure, the surface area of a stack, as the interface of fillermatrix, is n times lower than that of the exfoliated state. By considering the effect of the degree of exfoliation in the proposed model, a new equation was developed to predict the modulus enhancement in the nanocomposites filled with Montmorillonite (MMT). The theoretical predictions were supported by the experimental results.
Synthesis of polyetherols with 1,3-pyrimidine ring using 6-aminouracil, ethylene carbonate and propylene oxide
Authors: Chmiel-Szukiewicz Elżbieta
Published: August 2014

New method of synthesis of polyetherols with 1,3-pyrimidine ring by reactions of 6-aminouracil with ethylene carbonate and propylene oxide was described. The structure of products was analyzed using the IR, 1H-NMR and MALDI-TOF spectroscopies. Some physical properties and thermal stability of polyetherols were investigated. Initial tests on the foaming of polyurethanes obtained from the polyetherols were performed. Some properties of the foams such as apparent density, absorption of water, linear dimensions stability, thermal resistance and compression strength were investigated. Obtained foams show an improved thermal stability.
Characterization of nylon 6/11/montmorillonite nanocomposites prepared by in situ copolymerization
Authors: Zhang Yunsheng , Hu Guosheng , Wang Biaobing
Published: August 2014

A novel nylon 6/11/montmorillonite nanocomposite was prepared by in situ copolymerization of prepolymer of caprolactam with aminoundecanoic acid in the presence of organoclay, and characterized in terms of Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), transmission electron micrograph (TEM), intrinsic viscosity as well as differential scanning calorimetry (DSC). It was found that the addition of organoclay had great influence on the intrinsic viscosity and melting behavior but not on the crystal transition of nylon 6/11 matrix. Intercalated/exfoliated and stacked silicates layers were observed for various nanocomposites.
Silica supported Schiff-base cobaltIII complex-Lewis base system: a highly selective catalyst for alternating copolymerization of CO2 and propylene oxide
Authors: Niu Yongsheng , Li Hongchun
Published: August 2014

An binary catalyst system of a silica supported Schiff-base cobalt complex SalenCoIII (OAC)-MCM-41 (Salen = 3-[N,N-bis-2-(3,5-di-tert-butylsalicylidenamino) ethyl] amine) was developed to generate the copolymerization of CO2 and propylene oxide in presence of (4-dimethylamino)-pyridine (DMAP). The influence of the molar ratio of catalyst components, the operating temperature, reaction time, and CO2 pressure on the yield as well as the molecular weight of polycarbonate was systematically investigated. The high selectivity of polycarbonate over cyclic carbonate at 40 °C was maintained after a longer reaction time to attain quantitative formation of the alternating copolymer. High molecular weight of 67 000 were achieved at an appropriate combination of all variables.
Preparation of poly(vinylidene fluoride)-silver nanoparticle composite using dimethylformide as both a solvent and a reductant
Authors: Chen Yingbo , Liu Lina , Zhang Yufeng
Published: August 2014

Poly(vinylidene fluoride)-silver nanoparticle (PVDF-Ag) composites were synthesized by in situ reduction of silver salt using dimethylformide (DMF) as both a solvent and a reductant. The crystalline properties (e.g., crystallinity and the types of crystals) of the composites were characterized. It was shown that PVDF in the composites had a higher melting temperature than pure PVDF, and the α phase crystal in the composites became more stable with an increase in the amount of silver nanoparticles. The mechanical properties and morphologies of the composites were also investigated. It was noted that the PVDF-Ag composites have better mechanical properties when silver nanoparticles were added. The increase in toughness could be attributed to the formation of continuous structure between PVDF and silver particles.
Sulfur-containing polyurethanes as novel macro photoinitiators comprising in-chain benzophenone and coinitiator amine for photopolymerization
Authors: Wei Jun , Lu Rong , Qiu Jun , Liu Fang
Published: August 2014

Three novel sulfur-containing polyurethanes (PUs) as macrophotoinitiators, hydroxyl-terminated PUa and PUb, and amino-terminated PUc, were synthesized through polycondensation of a novel diamine 4,4’-bis[(4- amino)thiophenyl]benzophenone (BATPBP), isophorone diisocyanate (IPDI) and N-methyldiethanolamine (MDEA). The beznophenone and coinitiator amine structures were successfully introduced into the backbones of PUs. FT-IR, 1H NMR, GPC and DSC analyses confirmed their structures and properties. UV-vis spectra indicate that the macromolecular structure nearly has no influence on their UV-vis absorptions. A trifunctional monomer of trimethylolpropane triacrylate (TMPTA), initiated by these macrophotoinitiators with a low-molecular-weight photoinitiator system (benzophenone/MDEA) as the reference, was studied through photo differential scanning calorimetry (photo-DSC). The results show PUa is the most efficient photoinitiator and the molar content of coinitiator amine in PUs has an important effect on their photoefficiency.
Carbohydrate-based polyurethanes: A comparative study of polymers made from isosorbide and 1,4-butanediol
Authors: Marín Romina , Alla Abdelilah , Ilarduya Antxon Martínez de , Muñoz- Guerra Sebastián
Published: August 2014

A set of polyurethanes containing isosorbide units were synthesized by polymerization in solution from HDI and MDI diisocyanates and 1,4-butanediol (BD), isosorbide (Is) or diisosorbide diurethanes (Is2HDI and Is2MDI) as diols. The thermal properties and stability, and crystal structure of the polyurethane homopolymers and copolymers containing isosorbide were evaluated and compared with those of the polyurethane analogues entirely made of BD. Incorporation of isosorbide produced significant changes in Tg, Tm and Td but no noteworthy differences were found between copolymers made from Is or Is2 monomers. Degradation assays revealed that incorporation of Is units increased slightly the hydrolysis rate.
Influence of nanoparticles on the morphology, thermal stability and air permeability of electrospun polylactic-acid fibres
Authors: Alongi Jenny , Pošković Merima
Published: August 2014

Polylactic-acid (PLA) and PLA-clay fibres have been produced from solution of 1,1,1,3,3,3-hexafluoro-2-propanol by electrospinning. Nanoclays having different aspect ratio, namely a montmorillonite and a sepiolite, have been added and dispersed within the polymer matrix in order to enhance the thermal stability and air permeability of PLA. The influence of the polymer molecular weight, the solution viscosity and conductivity on the morphology of the fibres has been investigated. Electron microscopy has shown that fibre diameter and the presence of beads defects in the fibres depend on the type of clay added to the polymer matrix. The thermal stability in nitrogen and in air has been drastically enhanced for the presence of the clays as compared with neat polymer. Finally, permeability tests performed on the electrospun condensed fibres pointed out that PLA-clay fibres exhibit a lower permeability to air (up to 90%) with respect to neat PLA fibres.
Use of crystal violet to prepare SBR-montmorillonite clay nanocomposites
Authors: Chakraborty Sugata , Kar Saptrashi , Dasgupta Saikat , Mukhopadhyay Rabindra , Bandyopadhyay Samar
Published: August 2014

Present study describes the preparation and characterization of crystal violet modified-montmorillonite clay nanocomposites by latex blending technique. Coagulation of the latex-clay slurry produced nanocomposites master batch. The master batch was compounded with Styrene Butadiene rubber (SBR). WAXD and TEM provided the evidences of formation of nanocomposite. Remarkable improvements in the mechanical properties were found by addition of small amount of modified clay.
Fabrication and electrochemical characterization of carbon nanofibers by electrospinning with various MnO2 contents
Authors: Chang Duk-Rye , Heo Gi-Seok
Published: August 2014

Carbon nanofibers were fabricated by electrospinning with various concentrations of MnO2, carbonization and activation processing for supercapacitor applications. Microstructure and electrochemical properties were characterized by scanning electron microscopy (SEM), the 4-point probe method, and a battery cycler system. It was observed that 8-20 wt.% MnO2/PAN nanofibers had 190- 260 nm diameters. The diameter decreased with increasing MnO2 concentration, but it increased for concentrations greater than 16 wt.%. The 16 wt.% MnO2 solution produced the nanofibers with the smallest diameter. The nanofibers showed capacitor characteristics when fabricated into electrodes, and their electrical conductivity and capacitance increased with increasing MnO2 concentration. The 20 wt.% MnO2/PAN carbon nanofibers showed the highest electrical conductivity value (2.82×10-3 S/cm) and the highest capacitance value (186.28 F/g), which indicates their potential for development of supercapacitor electrodes.
correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP
Authors: Saengsuwan Sayant
Published: August 2014

Drawn composite thin film based on thermotropic liquid crystalline polymer (TLCP) and polypropylene (PP) was annealed at 130 °C at different times. The influence of annealing time on microstructural and mechanical properties of the composite film has been studied. The correlation in mechanical properties and their microstructural parameters has also been investigated. X-Ray diffraction results reveal that the smectic mesophase transforms progressively into the monoclinic phase as annealing time is increased. Consequently, the true crystallinity (Xc), crystal thickness (L) as well as relative level of molecular orientation of PP crystalline phase in the annealed TLCP/PP films are increased significantly. Also, the TLCP fibrils have no influence on the microstructure of PP crystalline phase. The apparent crystallinity (Xc,a) of PP phase evaluated by DSC also increase significantly with annealing time. As a result, the increases of these microstructural parameters coupled with the reinforcement of TLCP fibrils could be contributed directly to the remarkable enhancement of mechanical properties of the annealed TLCP/PP film in both machine (MD) and transverse (TD) directions. The correlation of moduli with microstructural parameters (Xc, Xc,a and L) exhibits nonlinear relations. However, the relative level of molecular orientation is a more suitable parameter to correlate with the improvement of mechanical properties of the annealed TLCP/PP film. Finally, this work presents that the mechanical properties of the TLCP in situ reinforced thermoplastics can be significantly enhanced via a simple thermal treatment.
Polymerization of acrylamide inverse microemulsion initiated directly by UV radiation
Authors: Xie Long , Shao Ziqiang , Wang Huiqing , Lv Shaoyi
Published: August 2014

Combining the microemulsion polymerization with UV direct initiation, an efficient method for polymerization of AM with high polymerization rate and conversion, low polymerization temperature, high purity of product and simple radiation equipment was developed. In the absence of initiator and under UV radiation, the polymerizations of AM inverse microemulsion system with high monomer content and low emulsifier content were successfully accomplished at low temperature (24~30 °C) and PAM with high purity and high limiting viscosity [η] was obtained. The polymerization rate was fast and the conversion reached to higher than 85% in 30 minutes. Based on the abundant experimental results, the reasonable polymerization mechanisms were proposed as follows: the AM participated in the initiation reaction and the main initiation locus was the emulsifier layer. Rp and [η] were weakly influenced by temperature due to the low apparent activation energy of the reaction (Ea = 12.98 kJ/mol). The polymerization kinetics of Rp was expressed as the following: Rp = [IUV]0.4972[M]1.5048[E]-0.5731. The Rp order with respect to [M] is equal 1.5048 which confirms the conclusion that the monomer participated in the initiation reaction.
Preparation of silk fibroin microspheres by emulsificationdiffusion method for controlled release drug delivery applications
Authors: Imsombut Thanonchat , Srisa-ard Mangkorn , Srihanam Prasong , Baimark Yodthong
Published: August 2014

Silk fibroin (SF) microspheres containing a model drug were prepared by a simple water-in-oil emulsification-diffusion method. Aqueous SF solution and ethyl acetate were used as water and oil phases, respectively. Methylene Blue was used as a water-soluble model drug. Effect of drug content on microsphere characteristics, drug loading efficiency and drug release behavior was determined. Scanning electron microscopy revealed that drug-loaded SF microspheres were spherical in shape with a smooth surface. The SF microspheres showed predominant random coil SF conformation. All drug loading efficiencies were approximately 50%. An increase in drug/SF ratio could lead to an increase in %drug release and surface erosion after the drug release test. Drug release from SF microspheres is due to SF matrix swelling and surface erosion processes.
Preparation of polyethylene-g-(polyacrylic acid) and its sodium salt ionomer by in-situ chlorinating graft copolymerization
Authors: Zhao Zhi-Qiang , Wang Shuang-Shuang , Wang Na , Zhao Ji-Ruo , Feng Ying
Published: August 2014

Acrylic acid (AA) was grafted firstly onto high density polyethylene (HDPE) by in-situ chlorinating graft copolymerization (ISCGC), so a graft copolymer composed of chlorinated polyethylene (CPE) as backbone and poly (acrylic acid) (PAA) as branched chains was synthesized. And subsequently the preparation of its carboxylated ionmers was studied. This work was focused on discussing the reaction process for grafting AA onto HDPE by ISCGC and the preparing of carboxylated ionmers of CPE. In this paper, the structure of graft copolymer and the ionomer were characterized mainly by FT-IR, gel permeation chromatography (GPC) and graft degree (GD). The influence factors which related to the main and side reactions, including the monomer concentration, chlorine contents of the product, and reaction temperature were investigated. Additionally, effects of these factors on reaction process controlling were described. The aim of above is to investigate how CPE-cg-PAA and its sodium-salt ionomer were prepared.
The miscibility estimation of some nanocomposites based on starch
Authors: Dimonie Doina , Radu Socoteanu , Doncea Sanda , Pop Florentina Simona , Petre Celina , Dumitriu Irina , Fierascu Radu
Published: August 2014

Based on the FTIR spectral changes, the miscibility of some nanocomposites based on starch, polyvinyl alcohol and treated multilayered silicate, was qualitatively estimated. The FTIR spectroscopy provide evident gross/small spectral changes as well as appreciable spectral shifts mainly in those spectral range that defines hydroxyl O-H vibrations (3600- 3000 cm-1 ), water absorbtion (1800 - 1500 cm-1) , the morphological order degree and the interaction with multilayered silicate and (1192 - 950 cm-1). Based on the observed spectral modifications it can be estimate that high miscibility do exist between the components of the studied nanocomposites.
Effect of FeCl3 on the morphology, wetting behavior, and stabilization/carbonization of polyacrylonitrile nanofibers prepared by electrospinning
Authors: Cai Yibing , Xu Xiaolin , Wei Qufu , Ke Huizhen , Yao Wang , Qiao Hui , Lai Chuilin , He Guangfei , Zhao Yong , Fong Hao
Published: August 2014

Herein we report that the neat polyacrylonitrile (PAN) nanofibers and PAN/FeCl3 composite nanofibers were prepared by the materials-processing technique of electrospinning. The effect of FeCl3 amount on the morphology and wetting behavior of the resulting composite nanofibers were studied by scanning electron microscopy (SEM) and drop shape analysis (DSA), respectively. The SEM images indicated that the diameters of composite nanofibers decreased with increase of FeCl3 amount, and this was probably due to the conductivity increase of spinning solutions. The results acquired from DSA measurement showed that the addition of FeCl3 increased the surface contact angle of water deposited on composite nanofibers, suggesting the higher hydrophobicity and the lower wetting behavior. Additionally, the effect of FeCl3 on stabilization and carbonization of the PAN composite nanofibers were investigated. The structural and morphological evolutions of the stabilized and carbonized nanofibers were studied by Fourier transfer infrared (FTIR) spectra and SEM. The FTIR spectra showed that the presence of FeCl3 in composite nanofibers considerably varied the mechanisms of thermo-chemical reactions during the heat treatments. The SEM images revealed that there were conglutinations of nanofibers after carbonization, while the degree of conglutination for the carbonized PAN composite nanofibers with FeCl3 was higher than that for the carbonized neat PAN nanofibers.