bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature-modulated DSC studies of time evolution of the polymorphic structure of PA6/clay nanocomposites
Authors: Zhao Xiong-Yan
Published: August 2014

Two PA 6/clay nanocomposites, NCN5 and NCN10 with 5 and 10% (wt %) clay, respectively, were prepared by a twin screw extruder. The effects of annealing including solid-state annealing and melt-state annealing on the polymorphic behavior and thermal property of nanocomposites have been comparatively studied as a function of annealing time using Modulated Differential Scanning Calorimetry (MDSC). It was demonstrated that NCN5 and NCN10 exhibit a similar polymorphic behavior when they were annealed in solid-state for different durations. As the annealing temperature was elevated to 245 °C (melt-state annealing), significant differences in thermal behavior and polymorphism between NCN5 and NCN10 could be found. For NCN5, the α structure became the absolutely dominating crystalline phase independent of the annealing durations, for NCN10, however, the formation of γ structure is greatly enhanced and longer annealing time would amplify this phenomenon. Moreover, a low-temperature endothermic peak was observed around 180 °C in both NCN5 and NCN10 samples which was also found to strongly depend on the thermal history.
Rheology, morphology and mechanical properties of LLDPE/PS blends catalyzed by combined Lewis acids
Authors: Liu Yan-Long , Yin Li-Gang , Ke Zhuo , Shi Qiang , Yin Jing-Hua
Published: August 2014

The rheological, morphological and mechanical properties of LLDPE/PS blends with a combined catalyst, Me3SiCl and InCl3·4H2O, were studied in this work. The higher complex viscosity and storage modulus at low frequency were ascribed to the presence of graft copolymers, which were in situ formed during the mixing process. From the rheological experiments, the complex viscosity and storage modulus of reactive blends were higher than the physical blends. The dispersion of LLDPE particles of reactive blending becomes finer than that of physical blends, consistent with the rheological results. As a result of increased compatibility between LLDPE/PS, the mechanical properties of reactive blends show much higher tensile and Izod impact strength than those of physical blends.
Preparation and characterization of hyperbranched polyimides based on 4,4’,4’’-triaminotriphenyl-methane
Authors: Sysel Petr , Minko Evgenia , Čechová Radana
Published: August 2014

This work focuses on the preparation and characterization of novel hyperbranched polyimides based on commercially available 4,4,’4’’- triaminotriphenylmethane and pyromellitic dianhydride or 4,4’-oxydiphthalic anhydride. The bi- and trifunctional monomers were reacted in a molar ratio of 1:1 or 2:1 to prepare polyimide precursors (hyperbranched polyamic acids) endcapped with either amino or anhydride groups. The precursors were then transformed into hyperbranched polyimides using thermal imidization. The final products were self-standing films, whose thermal behaviour was characterized by having no weight loss up to 250 ºC and by having glass transition temperatures above 200 ºC. We monitored the permeability of carbon dioxide, organic vapours and water vapour through these membranes. We also compared the properties of these materials with linear polyimides based on 4,4’-methylenedianiline combined with either pyromellitic dianhydride or 4,4’-oxydiphthalic anhydride.
Thermal properties of novel clay containing nanocomposites based on low density polyethylene/ ethylene-octene copolymer blends
Authors: Baghaei Bahareh , Jafari Seyed Hassan , Khonakdar Hossein Ali , Ashabi Ladan
Published: August 2014

Thermal behaviour of low-density polyethylene (LDPE)/ ethylene-octene copolymer (POE)/ organo-montmorillonite (org-MMT) nanocomposites, prepared via melt compounding were studied by means of differential scanning calorimetry (DSC), thermogravimetry analysis (TGA) and dynamic mechanical thermal analysis (DMTA) techniques. These nanocomposites showed different levels of intercalated structures depending on clay content, blend composition and compatibilization. Addition of polyethylene grafted maleic anhydride (PE-g-MA), as a compatibilizer, improved the intercalation process. The nanocomposites with 5% org-MMT and 5% PE-g-MA showed improved storage modulus and thermal stability in dynamic mechanical and thermal analysis, respectively. The degradation trends of nanocomposites were almost similar to the neat blends in nitrogen environment, but in air atmosphere thermal stability of the nanocomposites increased. The DSC results showed that the org-MMT layers dispersed in the nanocomposites could act as nucleation agents for the crystallization of the LDPE matrix. The results indicated that clay dispersion and interfacial adhesion, and consequently thermal properties of nanocomposites, are greatly affected by addition of PE-g-MA.
Investigation and modeling of the thermal conductivity of PP/clay nanocomposites and PP/MWCNT nanocomposites
Authors: Nejad Shahryar Jafari , Golzary Aboali
Published: August 2014

In this study, polypropylene/clay nanocomposites were prepared by melt blending method and their thermal conductivity and the thermal conductivity of polypropylene/multi-wall carbon nanotube (MWCNT) nanocomposites were investigated and modeled. It is found that the thermal conductivity of the PP/Clay and PP/MWCNT nanocomposites is increased with increasing temperature. The thermal conductivity of the nanocomposites is improved due to incorporation of nanoclay and MWCNT compared with pure PP matrix
Study on micro-phase separation structure of poly(ethylene terephthalate)-poly(hexylene terephthalate) (PET-PCT) copolymer
Authors: Wang Yuan , Yang Shenglin , Li Guang
Published: August 2014

PET-PCT copolyesters were prepared from terephthalic acid (PTA), ethylene glycol (EG) and 1,4-cyclohexane dimethanol (CHDM) through direct esterification and the subsequent polycondensation. The chemical composition and sequence length distribution of the copolyesters were investigated by 1H-NMR and 13C-NMR. The dynamic rheological behavior and dynamic mechanical property were studied by means of ARES-RFS and DMA. The results demonstrated that the obtained PET-PCT copolyesters were random block copolyesters and the content of PCT units incorporated was always greater than the feed and the numberaverage sequence length of each block in the copolyesters was in proportion to its content. The relation between storage modulus (G’) and frequency (freq) deviated from linearity as the frequency (freq) tend to zero (the terminal region effect), and the frequency band where the terminal region effect appeared would shift to higher value with the increasing content of PCT, suggesting the presence of phase separations. Moreover, two glass transition temperatures were observed from DMA curves, which revealed the incompatibility of PET segments and PCT segments, i.e. the micro-phase separation took place in PET-PCT copolyesters.
Fabrication of poly(lactic acid) scaffolds by a modified solvent casting/porogen leaching method
Authors: Gong Xinghou , Tang Chak Yin , Wong Chi Tak , Lu William Weijia , Zhang Yugang , Lam Wing Moon , Wu Shuping , Liu Jianing
Published: August 2014

A modified solvent casting/particulate leaching (SC/PL) method was developed to fabricate thick three-dimensional poly(lactic acid) (PLA) scaffolds with controlled pore size and porosity, and much shorter processing time. The pasty mixture of PLA/CHCl3/NaCl was sealed in a Buchner funnel by a piston with a suction flask connected. A vacuum pump was used to facilitate the volatilization of solvent. The scaffolds were obtained by subsequent removal of NaCl in deionized water. The pore size within the scaffold was in good accordance with the particle size of NaCl (< 210, 210~310, 310~420 and 420~500 μm), all of which had more than 89 % of porosity, 1.95 ± 0.2 MPa of compressive modulus and non-cytotoxic to L929 cells. To demonstrate the applicability of the SC/VV/PL method, thick cylindrical and tubular porous scaffolds have been produced in this study. Compared with the traditional SC/PL without vacuum volatilization, the modified method, namely, solvent casting/vacuum volatilization/particulate leaching (SC/VV/PL) method, provide a more efficient way to fabricate thick scaffolds.
Critical conversion in the processes of polymer formation
Authors: Irzhak Tamara F. , Irzhak Vadim I.
Published: August 2014

Relations between the critical conversion of gelation αc and the conditions of polymer formation by living and terminated polymerization were studied. It was shown that the weight average functionality of the initial system given by the formula,Φ22(0)=∑ i(i-1)mi where mi is the initial concentration of an i-functional monomer, is the parameter determining the value of αc. Formulas relating the critical conversion to the kinetic parameters of polymerization processes are presented. For polycondensation processes the kinetic equation based on the concept of bond blocks is proposed. It allows for estimating the gel point even for systems in which the substitution effect takes place for one of the components. The equation α ∑ i(i-1)ni=1 is , where α is the current conversion and ni are the values specifying the concentrations of i-functional blocks. The latter values are functions of α and may be calculated kinetically.
The effect of vinyl benzyl chloride on emulsion polymerization of styrene
Authors: Chaabouni Amel , Massardier-Nageotte Valerie , Elleuch Boubaker , Chehimi Mohamed M. , Elaissari Abdelhamid
Published: August 2014

Polystyrene latexes were prepared, in the presence of, vinyl benzyl chloride (VBC) monomer. These particles were synthesized in surfactant-free batch radical emulsion polymerization of styrene and VBC monomer mixture, with 2,2’- azobis(2-amidino propane)di-hydrochloride (V50) initiator. The polymerization kinetics was found to be rapid, as a function of VBC monomer concentration in the polymerization recipe. It is interesting to notice that high VBC amount leads to marked coagulum formation. The final hydrodynamic particle size was found to be slightly sensitive to the VBC concentration in the investigated range. The presence of VBC at the surface of the particles was investigated by XPS analysis.
Liquid crystalline polyureas with oligo(ethylene glycol) sequences
Authors: Mehdipour-Ataei Shahram , Akbarian-Feizi Leila
Published: August 2014

A diamine monomer containing ester, amide and ether functional groups was prepared and its polymerization reaction with different diisocyanates to give main chain poly(ester amide ether urea)s was investigated. The monomer was synthesized via reaction of terephthaloyl chloride with 4-hydroxybenzoic acid and subsequent reaction of the resulted diacid with 1,8-diamino-3,6-dioxaoctane. The polymers were characterized by FT-IR and 1H-NMR spectroscopic method and elemental analysis. The resulting polymers exhibited excellent solubility in polar solvents. Crystallinity of the resulted polymers was evaluated by wide-angle X-ray diffraction (WXRD) method, and they exhibited semi-crystalline patterns. The glass transition temperatures (Tg) of the polymers determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were in the range of 88-112 °C. The temperatures for 10% weight loss (T10) from their thermogravimetric analysis (TGA) curves were found to be in the range of 297-312 °C in air. Also the prepared polyureas showed liquid crystalline character.
Synthesis and characterization of novel value added biodegradable poly(aleuritic acid) from renewable resources (shellac) and invertible amphiphilic behaviors in various solvents
Authors: Pandey Asutosh K. , Nande Smita S. , Selukar Balaji S. , Garnaik Baijayantimala
Published: August 2014

A novel biodegradable polymer poly(aleuritic acid) (PAA) ( M̄w 120,000) was prepared from aleuritic acid, which was obtained from renewable resources (Lac) by using tin catalyst. Aleuritic acid (AL) was protected at 9, 10 position by dimethoxy propane. The protected AL (Pro.AL) was further polymerized to obtain linear protected polyaleuritic acid (PAL) by dehydropolycondensation. Effects of various kinetic and thermodynamic parameters were studied. After polymerization, the deprotection of PAL was carried out. The synthesized PAL and PAA were characterized by using various techniques such as FT-IR, LC-MS, SEC, NMR (1H and 13C), 13C CP/MAS (Cross Polarization / Magic Angle Spinning) of solid PAA, DSC, SEM and TEM etc. The micelle and inverted micelle -structure in polar and nonpolar solvents are highlighted.
Curing kinetics study of epoxy resin/hyperbranched poly(amideamine)s system by non-isothermal and isothermal DSC
Authors: Zhang Li , Yang Hui Kang , Shi Guang
Published: August 2014

Curing kinetics of epoxy resin/hyperbranched poly(amide amine)s (HPAMAM) system was studied by non-isothermal and isothermal differential scanning calorimetry (DSC). Non-isothermal DSC scans indicated that H-PAMAM was an effective curing agent of epoxy resin. The apparent activation energy (E) was 54.3 kJ/mol calculated through Kissinger method, and the kinetic parameters were determined by Málek method for the kinetic analysis of the thermal treatment obtained by DSC measurement. A two-parameter (m, n) autocatalytic model (Sěsták-Berggren equation) was found to be the most adequate selected kinetic model. In addition, the predicted curves from the kinetic model fit well with the nonisothermal DSC thermogram. The isothermal DSC method was used to investigate the curing process for resin at 60, 65, 70, 75 and 80 °С, respectively. Isothermal kinetic parameters, including k1, k2, m and n, were determined based on an autocatalytic mechanism proposed by Kamal. Both models were validated for a fitting to the experimental data by the Levenberg-Marquardt method. A process to determine the initial values for the fitting procedure was also proposed. The predictions of the validated models were in good agreement with the measured data, and were therefore applicable for numerical process optimization
Nitroxide-mediated polymerization of styrene in the presence of a novel trinitroxide
Authors: Li Jieai , Zhang Zhengbiao , Zhu Xiulin , Zhu Jian , Cheng Zhenping
Published: August 2014

The bulk polymerizations of styrene were performed in the presence of a novel trinitroxide, 2,4,6-tri(4’-oxy-2’,2’,6’,6’-tetramethyl-1’-piperidinyloxy)-1,3,5- triazine (TTPT). Typical features of controlled polymerization were observed, such as the first-order kinetics, the molecular weights (Mn) linearly increased with the conversion, and relatively narrow molecular weight distributions (Mw/Mn). The 1H NMR was used to characterize the obtained polystyrene. The most of obtained polymers at 110 °C were the polymer with two-arm linear structure, not the expected three-arm structure, which was confirmed by the analysis of degradation of obtained polymer by ascorbic acid. A proposed polymerization route of styrene mediated by TTPT was also discussed.
Investigation of gel-spun PAN fiber morphology by membrane technology techniques
Authors: Ma Caixia , Qin Zongyi , Pan Ding
Published: August 2014

The as-formed structure of gel-spun polyacrylonitrile (PAN) fiber from the solvent mixture system has been probed exploiting AFM techniques developed in the membrane industry. The surface structure of PAN membranes, prepared by phase transition under different casting conditions, was investigated by tapping mode atomic force microscopy. The results obtained show that the size and the density of these aggregates are dependent on the casting solution, namely on the type and concentration of the non-solvent. In the present work, tapping mode atomic force microscopy is used to comply with the main objective of differentiating surface morphologies of membranes.
Thermal degradation behaviours of flame-retardant polycarbonate containing potassium diphenyl sulfonate and polymethylphenylsilsesquioxane
Authors: Wang Jiangbo , Xin Zhong
Published: August 2014

Potassium diphenyl sulfonate (KSS) and polymethylphenyl silsesquioxane (PMPSQ) were proved to be effective flame retardants for PC by the LOI test and UL-94 measurements. The thermal degradation behaviours were investigated by TGA and flame-retardant mechanism of KSS/PMPSQ/PC system was studied by the kinetic analysis methods including Kissinger method and Flynn- Wall-Ozawa method. The results showed that the activation energies of flameretardant PC (FRPC) were lower than that of pure PC at lower degree of conversion, which indicated that the KSS and PMPSQ both promoted the thermal degradation of PC in the early and middle stages. Flynn-Wall-Ozawa method further revealed that the addition of the flame retardant PMPSQ increased the activation energy of FRPC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of FRPC in the thermal degradation. Therefore, the improved flame-retardant behaviours of KSS and PMPSQ on PC were achieved.
Block copolymerization of 2,2-dimethyltrimethylene carbonate with adipic anhydride catalyzed by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate)
Authors: Ling Jun , Ren Shijian , Shen Zhiquan
Published: August 2014

Tetrahydrofuran-soluble block copolymer of 2,2-dimethyltrimethylene carbonate with adipic anhydride [poly(DTC-b-AA)] containing 64.7/35.3 DTC/AA in molar ratio with Mn of 12.3 104 and Mw/Mn of 1.64 was synthesized by lanthanum tris(2,6-di-tert-butyl-4- methylphenolate) catalyst at 25 C in 32 min. The copolymer was characterized by SEC, 1H NMR and DSC. Copolymers with AA block from 8.5 % to 50.8 % were prepared by changing the solvent and feeding ratio of DTC/AA.
Synthesis of ATRP macroinitiator based on synthetic cis- 1,4-polyisoprene and its application for graft polymerization of MMA
Authors: Vayachuta Lapporn , Phinyocheep Pranee , Derouet Daniel , Pascual Sagrario
Published: August 2014

Modification of synthetic cis-1,4-polyisoprene (PI) into bromoalkylfunctionalized polyisoprene (PIBr), an ATRP macroinitiator, was investigated by two-step chemical reaction. The PI was partially epoxidized into epoxidized polyisoprene (EPI) using m-chloroperbenzoic acid, then the EPI was transformed into PIBr by reaction with 2-bromo-2-methylpropionic acid. The results from 1H NMR revealed that the addition product occurs in competition with epoxide ring rearrangement. The amount of bromoalkyl functionalized units was determined from 1H NMR spectra. The graft polymerization of MMA using ATRP technique from macroinitiator units in PIBr was investigated using three different ligands, i.e. N-(n-octyl)-2-pyridylmethanimine (NOPMI), N-(n-octadecyl)-2-pyridylmethanimine (NODPMI) and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), resulting in formation of graft copolymer of PI and PMMA. The PMMA grafts were successfully separated from the PI backbone using acidolysis for studying their number-average molecular weights (M̄̅̅n,SEC ) and polydispersity indexes (PDI). All of the ligands used give a increase of M̄̅̅n with MMA conversion. Comparing between 3 ligands, Cu(I)Br complexed with NOPMI shows first-order kinetic plot.
Preparation of ZnO/PMMA inorganic/organic composite microspheres via soap less emulsion polymerization
Authors: Ma Xiaokun , Tang Lanqin , Zhou Bing , Xia Yupeng , Lei Hong , Wang Zichen
Published: August 2014

ZnO/PMMA inorganic/organic composite microspheres were synthesized with a yield of 83 wt% via soap less emulsion polymerization. The hydrophobic ZnO nanoparticles were modified by oleic acid (OA), which could improve the compatibility between ZnO nanoparticles and methyl methacrylate (MMA) monomer in emulsion system. The existence of ZnO was indicated by the XRD characteristic peaks of the composite microshperes. The TEM micrographs showed that the morphology of the composite microspheres was uniform and ZnO nanoparticles could be encapsulated in the PMMA polymer microspheres. When the ZnO nanoparticles participated in the polymerization process, the surface morphology of composites microspheres changed from smooth to grooved which was characterized by FESEM. In addition, the fluorescence property of the ZnO/PMMA composites became stronger with the increasing amount of ZnO nanoparticles and the fluorescence absorption was stronger than that of pure ZnO.
Methacrylate copolymers with substituted azobenzene side groups: synthesis, characterization and photo-induced birefringence properties
Authors: Cao Haizhong , Zhu Jian , Zhang Wei , Chen Xinrong , Cheng Zhenping , Wu Jianhong , Zhu Xiulin
Published: August 2014

Well-defined copolymer of methyl methacrylate (MMA) and 2-methylacrylic- acid-2-{ethyl-[4-(4-methoxy-phenylazo)-3-methyl-phenyl]-amino}-ethyl ester (MAMP) bearing pendent azobenzene groups, was synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). Copolymers with different contents of azobenzene moieties, e. g. from 12 mol % to 100 mol %, were obtained by varying the feed molar ratios of MAMP and MMA. The reactivity ratios of these two monomers were measured and calculated via the modified Kelen- Tüdos method. Glass transition temperature of the copolymers was measured by differential scanning calorimetry (DSC). Photoinduced trans-cis isomerization of azobenzene moieties in the copolymer was studied at room temperature. Films cast from the functional copolymers were characterized by photo-induced birefringence and surface relief grating (SRG).
Microwave-assisted ring-opening polymerization of poly (glycolic acid-co-lactic acid) copolymers
Authors: Li Guang , Zhao Na , Bai Wei , Chen Dong Liang , Xiong Cheng Dong
Published: August 2014

The microwave-assisted synthesis of poly(glycolic acid-co-lactic acid) (PGLA) copolymers by ring-opening polymerization of glycolide (GA) and L-lactide (L-LA) was studied. The microwave irradiation time and feed ratios on the molecular weights, as well as the thermal properties of the copolymers were discussed. These copolymers were characterized by 1H-NMR, GPC and DSC. It was found that the largest molecular weight ([η]: 0.8745 dL/g) of PGLA5050 was obtained at the irradiation time of 5 min. The color of the copolymers changed from white to light brown, and the yield was higher with the extension of the irradiation time. The molar component ratio of GA in PGLA (FG) was higher than the initial GA feed ratio (nGA) in the raw materials. As the nGA content increased, the glass transition temperature (Tg) of the copolymers decreased and the melting temperature (Tm) of the copolymers increased.
Tuning of multicompartment micelles from cross-linkable ABC triblock copolymer with the addition of core-forming homopolymer
Authors: Yu Haizhou , Jiang Wei
Published: August 2014

Multicompartment disks with bumpy edges could be synthesized controllably by dissolving a linear ABC amphiphilic triblock copolymer of polystyrene-b-polybutadiene-b-poly (2-vinylpridine) (PS440-b-PBd1020-b-P2VP114) in selective solvent mixtures of toluene and methanol. The disk size was controllable by the initial copolymer concentration. Diameter of the disks increased with the increase of the copolymer concentration. Interestingly, through adding a homo-PS to the system morphological transition took place from multicompartment disk with bumpy edges to sphere, and to hollow sphere with bumpy surfaces. Furthermore, the diameters of the hollow spheres increased with the increase of the homo-PS content, whereas the diameters of the hollows remained unchanged. Moreover, the PB block could be cross-linked by UV irradiation, stabilizing the preformed structure.
Development of synthetic extracellular bone matrix on poly(L-lactic acid) substrates via electrostatic selfassembly and biomimetic mineralization technologies
Authors: Tan Qinggang , Ren Jie , Chen Chu
Published: August 2014

Biomimetic formation of extracellular matrix (ECM) like coatings on artificial biomaterials provides a promising route to gain bioactive materials for tissue engineering applications. Organic ECM is also a template for apatite mineralization in bone tissue. This study was aimed at designing a multilayer film containing an ECM-like molecule on biomaterial surfaces to direct apatite mineralization and to develop biomimetic biomaterials for bone tissue engineering. A multilayer film consisting of gelatin and poly(ethylenimine) molecules was formed on a poly(L-lactic acid) substrate via electrostatic self-assembly technique. Bonelike apatite coating was formed on the multilayer film modified poly(L-lactic acid) substrate in simulated body fluids (SBFs). The amount of forming apatite could be controlled by the Ca2+ and HPO4 2- concentrations in SBF and also through the mineralization time. Gelatin terminated multilayer film can induce the apatite formation with a weak orientation in the (002) plane and the apatite is similar in composition to the natural bone. The gelatin multilayer film/apatite composite coating may serve as a promising microenvironment for bone tissue formation and growth.
Synthesis and quaternization of nitroxide-terminated poly(4-vinylpyridine-co-acrylonitrile) macroinitiators and related diblock copolymers
Authors: Poláková Lenka , Lokaj Jan , Holler Petr , Starovoytova Larisa , Pekárek Michal , Štěpánek Petr
Published: August 2014

Nitroxide-terminated 4VP AN copolymers have been synthesized at 125 oC using an alkoxyamine (MAMA-SG1) as a unimolecular initiator. Their compositions were compared with those published for the conventional radical 4VP-AN copolymerization. To verify the initiation potential of the copolymers containing nitroxyl end groups, they were employed in chain extension with styrene (S). Both the prepared statistic copolymer macroinitiators and related diblock copolymers, poly(4VP-co-AN) and poly(4VP-co-AN)-block-poly(S), respectively, were quaternized with methyl iodide in N,N-dimethylformamide or methanol at ambient temperature. The size-exclusion chromatography and NMR were used for the characterization of the polymers; the completeness of the quaternization was checked by the IR spectrometry.
Miscibility and crystallization kinetics of poly(ε- caprolactone)/bezoxazine blends
Authors: Chiu Hsiu-Jung , Tsai Ruey-Shi , Huang Jieh-Ming
Published: August 2014

The miscibility and crystallization kinetics of the blends of poly(e- caprolactone) (PCL) and bezoxazine (B-m) resin was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that PCL/B-m blends were miscible in the melt. Thus the blend exhibited a single glass transition temperature (Tg), which increased with increasing B-m composition and the crystal equilibrium temperature (Tmo) depressed with the addition of B-m from the Hoffman-Weeks equation analysis. The freezing crystallization temperature (Tfc) for the nonisothermal crystallization on the cooling process, and the spherulitic growth and overall crystallization rates of PCL for the isothermal crystallization were depressed with the addition of B-m component, attributing it to the dilution of PCL concentration due to the addition of B-m.
Essential work of fracture study on thermoplastic polyolefin filled with silicon carbide nanoparticles
Authors: Liao Cheng Zhu , Tjong Sie Chin
Published: August 2014

Thermoplastic polyolefin (TPO) containing 70 wt% polypropylene and 30 wt% styrene-ethylene-butadiene-styrene grafted maleic anhydride and its nanocomposites filled with 1-5wt% silicon carbide nanoparticles (SiCp) were prepared by melt processing followed by injection molding. Tensile tests show that both Young’s modulus and tensile strength increase with increasing SiCp loading. Essential work of fracture (EWF) method was used to evaluate the fracture toughness of resulting nanocomposites. EWF test demonstrates that the fracture toughness of TPO blend generally decreases with increasing SiCp content. Shield yielding and fibrillation are the main fracture mechanisms for TPO blend and composites. SiCp are found to improve the heat deflection temperature of the TPO blend.
Synthesis and water/oil repellency properties of cationic perfluoralkyl acrylate copolymer latices
Authors: Tang Xin , Shen Yi-Ding
Published: August 2014

A series of cationic perfluoralkyl acrylate copolymer latices were prepared by two-stage emulsifier-free emulsion polymerization method. Perfluoroalkylethyl acrylate (FEA) and [2-(methacryloxy)ethyl] trimethyl ammonium chloride (DMC) were used as fluoromonomer and cationic monomer, respectively. The structure and composition of copolymer were characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). Thermal stability of copolymer latex film was investigated by thermogravimetic analysis (TGA). The relationships of polymerization conditions between the conversion and coagulation ratio were discussed in detail and the optimal polymerization condition was identified. The water and oil repellency performance of perfluoralkyl acrylate copolymer latices applied to textiles is significantly investigated. Increasing the FEA amount in the emulsion will lead to increase in the contact angle and water and oil repellency on cotton fabrics. When the FEA dosage was 3.9%, the static contact angles of water and liquid paraffin on the surface of cotton fabrics treated were 142.5° and 126.5°, respectively.
Functional nano fillers in epoxy-dicyandiamide adhesives for prolonged shelf life and efficient cure
Authors: Gaukler Jan Christoph , Müller Ulrich , Krüger Jan Kristian , Possart Wulff
Published: August 2014

Shelf life at room temperature and curing behaviour at elevated temperature are studied for hot-curing accelerated epoxies (EP, diglycidylether of bisphenol A plus dicyandiamide (Dicy)) by FTIR-spectroscopy and modulated DSC. The accelerator is added either directly or with nano-zeolite filler to the EP. Due to the immobilisation of the accelerator in the pores of the nano-zeolite, the shelf life of this EP is 5 times longer than for the EP containing free accelerator. While the free accelerator acts during the whole heating step to curing temperature, the nano-zeolite does not release the accelerator before ca. 100 °C. As monitored by light microscopy, the released accelerator not only supports the curing but also stimulates the dissolution of the solid Dicy. As the result, network formation at 170 °C finishes within less than 25 minutes for the nano-filled EP.
Biopolymeric matrices based on chitosan for medical applications
Authors: Mucha Maria , Balcerzak Jacek , Michalak Iwona , Tylman Michał
Published: August 2014

AbstractChitosan (CS) based materials in a form of composite with poly(lactic acid) (PLA) granules, films and freeze-dried scaffolds also with blend form with hydroxypropylocellulose (HPC), as well as dibutyrylchitin films were obtained. These structures are intended especially for controlled drug delivery systems, including transdermal and oral dosage forms. Excellent adhesion of biopolymer matrices to PLA microspheres or hydroxyapatite (HAp) particles was proven. The Iorder drug (ibuprofen (IBU)) release kinetics from obtained films is stated.
Synthesis and characterization of some polyimide-epoxy composites
Authors: Akhter Toheed , Siddiqi Humaira Masood , Akhter Zareen , Butt M. Saeed
Published: August 2014

Composites from some novel polyimide and commercial epoxy were prepared aiming to improve the thermal behavior of epoxy resins. Two diamines namely 4-4'-diamino-4''-hydroxytriphenyl methane (DHTM) and 4-4'- diaminotriphenyl methane (DTM) were synthesized by reacting aniline and aldehydes according to a reported method. The synthesized diamines were blended with commercially available epoxy 1, 4-butanedioldiglycidylether (BDDE) to synthesize model epoxy amine networks which were compared with polyimideepoxy composites. The polyimides were synthesized by reaction of these diamines with aromatic anhydride namely 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA). These synthesized polyimides were dispersed in epoxy diamine networks to prepare composites. All the monomers and composites were characterized by making use of various analytical techniques including FTIR, NMR, TGA, DSC and XRD. Presence of hydroxyl group in the diamine helped in better dispersion of polyimide leading to high Tg and high char yield at 600 °C.
The pervaporation performance and mass transfer process of PDMS membranes for acetic acid/water mixture
Authors: Hong Housheng , Chen Longxiang , Zhang Qingwen , You Tao
Published: August 2014

Polydimethylsiloxane (PDMS) membranes with different silica content were prepared without support. The characterization and performance of the membranes were investigated by scanning electron microscope (SEM), thermogravimetry analysis (TGA), contact angle meter and swelling experiment. The pervaporation process was investigated with acetic acid/water mixture. And the process of mass transfer was analysed depending on the solution-diffusion model. The addition of silica could greatly improve the pervaporation flux and enhance the thermal stability of membrane. With an increase in feed temperature, selectivity decreased and permeation flux increased for the unfilled PDMS membrane. However, the separation factor of silica loading of 10 wt. % membranes, exhibited a maximum at 50 °C, and it was higher than unfilled membrane when feed temperature was above 40 °C. With the enhancement of acetic acid concentration, flux and separation factor increased. And the unfilled membrane and the silica filled membrane were prior permeation membranes for water when the downstream pressure of unfilled membrane and silica filled membrane was over 1000 Pa and 1500 Pa respectively.
Polymerization of ethylene using a nickel α-diimine complex covalently supported SiO2-MgCl2 bisupport
Authors: Jiang Hongliu , Lu Jinshan , Xiao Jianhua
Published: August 2014

Bisupported catalyst for ethylene polymerization was prepared by mixing alcohol solution of MgCl2 with pretreated SiO2 in heptane, the prepared bisupport was modified by treatment with alkyl aluminum compounds, and further treatment with bis(4-(4-amine-3,5-diisopropylbenzyl)-2,6-diisopropylphenylimino) acenaphthene NiBr2 (abbreviaed as NiLBr2) solution. The most significant feature of the supported catalyst is that it polymerizes ethylene with high activities in the presence of inexpensive general alkylaluminum compounds. According to the results of high temperature GPC, the number-average molecular weights of the polymers ranged from 2.15×105 to 9.27×105 and the polydispersities ranged from 3.12 to 4.23. By modulating the polymerization temperatures, the products of different and good morphologies were obtained. The resultant PE was confirmed by 13C NMR to contain significant amounts of not only methyl but also ethyl, propyl, butyl,amyl, and long branches (longer than six carbons).
Bioactive support for cell cultivation and potential grafting. Part 1: Surface modification of 2-hydroxyethyl methacrylate hydrogels for avidin immobilization
Authors: Hobzova Radka , Pradny Martin , Zhunusbekova Nazym M. , Sirc Jakub , Guryca Vilem , Michalek Jiri
Published: August 2014

Synthetic hydrogels are often used in biomedical applications as many of them are compatible with living tissue and moreover they can meet most criteria for artificial tissue properties. For applications in tissue engineering modification of polymer surface using some bioactive compounds (e.g. saccharides, proteins) for promoting the process of cell adhesion and proliferation is widely used. In this work, a series of modified hydrogels was prepared by three different methods: by copolymerization of 2-hydroxyethyl methacrylate with methacrylic acid, by hydrolysis and oxidation of poly(2-hydroxyethyl methacrylate) to obtain carboxyl-rich supports. The influence of the reaction conditions of the hydrogel surface treatment on the total carboxylic group content and the swelling degree was studied. The modified hydrogels were characterized by attenuated total reflectance FT-IR spectroscopy and refractive index measurements. Obtained carboxylic groups on the hydrogel surface have allowed the immobilization of avidin in two ways: 1) electrostatically through dissociated carboxylic groups and 2) covalently bonded through activated carboxylic groups by Nhydroxysuccinimide. The capacity of hydrogels for avidin immobilization was determined by Bradford spectrophotometric method. The results so far obtained from the preliminary biological tests showed that immobilized avidin on the hydrogel surface provides better adhesion and proliferation of keratinocytes compared to supports without avidin.
Preparation and characterization of high molecular weight poly(trimethylene terephthalate) by solid-state polymerization
Authors: Hoon Kim Seok , Ho Kim Joon
Published: August 2014

Solid-state polymerization has been widely used to prepare high molecular weight poly(ethylene terephthalate). Solid-state polymerization is generally carried out by heating solid, melt-phase-polymerized polymer below its melting temperature but above its glass transition temperature. Solid-state polymerization of poly(trimethylene terephthalate)(PTT) is not an independent process but rather an additional process with respect to melt polymerization that is used when PTT of a higher molecular weight is required. Two kinds of commercial PTT chips were polymerized in the solid state to prepare high molecular weight PTT, which were characterized by end group contents, molecular weight, thermal analysis and X-ray diffraction. In the solid-state polymerization of PTT, the overall reaction rate was governed by the reaction temperature, reaction time and pellet size. The content of carboxyl end groups was decreased during the solid-state polymerization with increasing reaction time and temperature. The melting temperature and crystallinity of solid-state-polymerized PTT were higher at longer times and higher temperatures of polymerization. The activation energy for the solid-state polymerization of PTT was in the range of 24~25 kcal/mol for each chip. Through the solid-state polymerization of commercial PTT chips, we could get high molecular weight polymers up to an intrinsic viscosity value of 1.63 dl/g, which is equivalent to about a 117,000 weight-average molecular weight.
Oligomeric alkylpyridinium surfactants prepared via ATRP
Authors: Su Xin , Chu Zonglin , Shuai Ya , Guo Zanru , Feng Yujun
Published: August 2014

A series of oligomeric alkylpyridinium surfactants were prepared directly in aqueous media by atom transfer radical polymerization (ATRP) of a surfmer, 4- vinyl-N-dodecylpyridinium bromide, and their surface activities were examined in comparison with the surfmer. The resulting oligomers have narrow molecular weight distributions, with polydispersity indices in the range of 1.17-1.23. By using 2-morpholinoethyl 2-bromo-2-methylpropanoate as ATRP initiator, the molecular weight of oligomeric surfactants was characterized by 1H NMR and the results were close to those obtained from GPC analysis. It was found that critical micelle concentration (CMC) of the oligomeric alkylpyridinium surfactants shifted to lower concentrations with increasing degree of polymerization (DPn), and their γ-cmc values were smaller by about 4 to 8 mN/m than that of the corresponding surfmer. Among the series of surfactants, the oligomer with highest DPn showed the greatest efficiency in lowering the surface tension in aqueous solution.
Thin-layer synthesized acrylamide copolymers modified with montmorillonite. Flocculation efficiency evaluation
Authors: Ubowska Agnieszka , Spychaj Tadeusz , Paździoch Waldemar
Published: August 2014

Hydrophilic copolymers based on acrylamide and diallyldimethylammonium chloride including those modified with montmorillonite have been synthesized, characterized by capillary viscometry and FTIR, and their flocculation efficiency has been tested. As an inorganic modifier sodium montmorillonite has been used. In situ copolymerization reactions were carried out as thin-layer processes in aqueous solutions. The results from numerous tests based on model water suspensions (talc and coal fine) confirm high flocculation efficiency of the investigated copolymers. The new type of acrylamide copolymers allow to ascertain that their synthesis in the presence of layered silicates can improve flocculation performance in comparison with unmodified copolymers. These copolymers may potentially compete with acrylamide copolymers in terms of price and flocculation effectiveness.
Energy needs for drying of PAAm- κC composites prepared with various κC contents
Authors: Pekcan Önder , Evingür Gülşen Akın
Published: August 2014

Various polyacrylamide (PAAm) - Kappa Carrageenan (κC) composite gels were prepared from acrylamide (AAm), N,N- methylenebisacrylamide (BIS) and different κC contents by free radical crosslinking copolymerization in water. Pyranine (P) was introduced as a fluorescence probe, and scattered light, Isc, and fluorescence intensities, I, from these gels were monitored during drying at different temperature. The fluorescence intensity of pyranine increased as drying time is increased for all samples. The behavior of I was quantified using the Stern-Volmer equation with moving boundary diffusion model. Desorption coefficient, D increased as temperature was increased for a given κC content. Supporting gravimetrical and volumetric experiments were also carried out during drying of PAAm-κC composite gels. The energy, △E values were measured for the drying processes for each κC content gel by using fluorescence, gravimetrical and volumetric methods, respectively. It is understood that △E values increase by increasing κC content, indicating that energy needs for the drying of high κC content gel is larger than low κC content gel.
Effects of compatilizers on the cellular structures, interfacial morphologies and mechanical properties of PP foam composites
Authors: Yang Ji-Nian , Li Zi-Quan , Liu Jin-Song
Published: August 2014

The short glass fiber (SGF)/polypropylene (PP) and ethylene-1-octene copolymer (POE)/SGF/PP foam composites were prepared by extrusion and subsequent post-foaming process in designed dies. The compatilizers, maleic anhydride grafted PP (PP-g-MAH) and maleic anhydride grafted POE (POE-g- MAH), were employed to improve the performance of the foam composites, respectively, and their influences on the cellular structures, interfacial morphologies and mechanical properties of PP foam composites were investigated. It was found that the compatilizers resulted in modified PP foam composites characterized by uniform cell size distribution, reduced cell size and increased cell density except POE/SGF/PP with POE-g-MAH. The obvious enhanced SGF-matrix interfacial bonding was observed from the SEM examination, and POE-g-MAH also facilitated the compatibility between elastomeric particles and matrix. Testing results indicated that, by the introduction of PP-g-MAH or POE-g-MAH, the mechanical properties of PP foam composites were significantly improved, and it seemed that the PP-g-MAH was more effective in strengthening the flexural and compressive strength while POE-g-MAH greatly increased the impact toughness.
Preparation of the high dielectric performance flexible materials achieved by polyacrylamide/poly(vinylidene fluoride) blends
Authors: Li Rui , Xiong Chuanxi , Dong Lijie
Published: August 2014

A novel all-polymeric material with high dielectric constant (k) has been developed by blending poly(vinylidene fluoride) (PVDF) with polyacrylamide (PAM). The dependence of the dielectric constant on frequency and polymer volume fraction was investigated. When the weight fraction of PAM is 1wt%, the dielectric constant of the blend could be up to 24, and the dielectric loss tanδ can be lowered to 0.06. The SEM investigations suggest that the enhanced dielectric behavior originates from significant interfacial interactions of polymer-polymer. XRD and FTIR demonstrate that blending PAM with PVDF affects the crystalline behavior of each component. Our finding suggests that the created high-k polymeric blends represent a novel type of material that are flexible and easy to process, and is of relatively high dielectric constant and high breakdown strength; moreover find applications as flexible electronics.
The synergism of MgCO3 and 2ZnCO3·3ZnO·4H2O as flame retardants and smoke suppressants for flexible poly(vinyl chloride) (PVC)
Authors: Qu Hongqiang , Wu Weihong , Jiao Yunhong , Xie Jixing , Xu Jianzhong
Published: August 2014

MgCO3 and 2ZnCO3·3ZnO·4H2O (AZC) as flame-retardants and smoke suppressants for flexible poly(vinyl chloride) (PVC) was evaluated using limiting oxygen index (LOI), smoke density rating (SDR) tests, scanning electron microscopy (SEM) and thermogravimetry analysis (TGA). The activation energy (Ea) of the original and flame retardant PVCs’ degradation processes was calculated by the Vyazovkin method. The results showed that the AZC can be used as a synergistic agent for MgCO3 as flame retardants agent of flexible PVC. The composites of MgCO3 and AZC cannot only decrease the initial decomposition temperature and increase the weight loss rate in the first stage, but also can promote the char formation in the second stage. The AZC decreased the Ea of the degradation reaction of PVC in the first stage and MgCO3 increased the Ea in the second stage, which means that the AZC combined with MgCO3, catalyzed the dehydrochlorination, promoted the early crosslinking for the PVC compound and improve the stability of the char residue. The SEM results also show that the char residue of MgCO3/AZC treated sample has a continuous and denser structure, which can be used as a barrier for the PVC bulk.
Obtaining of polyurethane foams with contribution of hydroxyalkylation products of oxalamide with alkylene carbonates and their properties
Authors: Zarzyka-Niemiec Iwona
Published: August 2014

Reaction products of Oxalamide (OD) with a 8- and 12-molar excess of ethylene carbonate (EC) and propylene carbonate (PC), characterized by an enhanced thermal stability due to the presence of Oxalamide arrangement, were used as polyol components for obtaining foamed polyurethane plastics. As an isocyanate agent diphenylmethane-4,4’-diisocyanate was used. The obtained new foamed polyurethane plastics are characterized by a slight water uptake, good stability of dimensions and an enhanced thermal stability.
Synthesis of aromatic polyimide bearing long alkyl chains through click reaction
Authors: Morinaga Hisatoyo , Imahashi Masamine , Takeichi Tsutomu
Published: August 2014

A click reaction of aromatic polyimide having azide groups at both chainends (2), which was obtained by an azidation of polyimide having chloromethyl groups (1), was conducted with 1-octyne, leading to the polyimide having n-hexyl groups (3). 1H NMR spectroscopic analysis for 3 reveals that the n-hexyl groups were successfully introduced into the both chain-ends of aromatic polyimide and that a number-averaged molecular weight of the resulting polymer 3 was 6000. Differential scanning calorimetry analysis for 3 exhibited 30 °C lower glass transition temperature compared to that of 1, by introducing long alkyl groups into the aromatic polyimide chain.
Thermal behavior of epoxy blends for light emitting diode encapsulation
Authors: Tan Seah-Guan , Chow Wen-Shyang
Published: August 2014

Epoxy encapsulant with high glass transition temperature (Tg) is required to ensure light emitting diode (LED) functions properly during its service life. Epoxy blends (cycloaliphatic epoxy, diglycidyl ethers of bisphenol-A and novolac resin) were thermally cured using methylhexahydrophthalic anhydride. Effects of the three types epoxy resins on the Tg of the ternary blends were examined. The Tg was mainly controlled by the concentration of cycloaliphatic epoxy. Optimization with constraint was conducted to produce epoxy blends formulation with optimum Tg. It was found that linear mixture model can fit well the experimental Tgof the epoxy ternary blends.