bluuebunny/crossref_metadata_2025 huggingface dataset:
Partition of tert-dodecyl mercaptan in systems containing styrene, polystyrene, and polybutadiene. Its effect on the macromolecular characteristics of high-impact poly styrene
Authors: Casís Natalia , Luciani Carla Vanesa , Estenoz Diana Alejandra , Martinelli Marisa , Strumia Miriam , Meira Gregorio Raúl
Published: August 2014

This work investigates the distribution between phases of tert-dodecyl mercaptan (t-DDM) in systems containing styrene (St), polystyrene (PS), and polybutadiene (PB) with the aim of studying its effect on the molecular macrostructure of High-Impact Polystyrene (HIPS) produced via the bulk process. Experimental work involved the study of several St/PS/PB/t-DDM blends, and of 2 polymerizations of St in presence of PB (with and without t-DDM). Blends were prepared with increasing PS/St ratios to emulate monomer conversions of 7, 9, 11, 13, and 15%, employing 2 base PSs of different molar masses, and several total concentrations of t-DDM. Measurements by Proton Nuclear Magnetic Resonance (1H NMR) indicate that t-DDM is almost evenly distributed between the phases at room temperature. In addition, for samples taken along the 2 investigated polymerizations, monomer conversion, grafting efficiency, and free PS molecular weights were measured. Theoretical work involved first to model the species partitions through the Flory-Huggins theory [1]; and then, to combine such partition model with a polymerization model extended from that by Casís et al. [2]. Theoretical estimations were in good agreement with experimental determinations. Simulations suggest that t-DDM partition coefficients exhibit a weak dependence with temperature, but a strong dependence with its total concentration. Also, the combined partition/polymerization model indicates that the free PS contained in the occlusion regions exhibits lower molecular weights than that in the continuous matrix.
Synthesis of nicotinamide-imprinted polymers and their binding performances in organic and aqueous media
Authors: Mookda Pattarawarapan , Singha Komkham , Weeranuch Kareuhanon , Chatchai Tayapiwatana
Published: August 2014

To obtain molecularly imprinted polymers capable of selective rebinding with nicotinamide (NAM), NAM imprinted polymers were synthesized via bulk polymerization using various functional monomers and cross-linkers. The NAM recognition properties of these polymers were investigated in organic and aqueous solvents by equilibrium rebinding experiments. The results show that the imprinted polymer prepared using 1:4:4 molar ratio of NAM/MAA/TRIM in dichloromethane exhibited the greatest NAM binding capacity and selectivity. This polymer is potentially valuable for the analysis of NAM in complex matrices where selective isolation and identification are needed.
Preparation of polyaniline nanofibers using the organic solution of aniline as seed
Authors: Xing Shuangxi , Zheng Hongwei
Published: August 2014

Polyaniline (PANI) nanofibers were prepared using an organic solution of aniline as seed in aqueous solution of ammonium persulfate oxidant. Two types of organic solvents were used, which are miscible and immiscible with water to investigate their effect on the properties of the resulting PANI via the aid of SEM, UV-Vis and FT-IR spectra and conductivity measurements The water dispersity of the polymer was also discussed based on the UV-Vis spectra data. Two possible mechanisms were proposed to explain the formation of the PANI nanofibers during the seed polymerization.
Viscosimetric studies of chitosan nitrate and chitosan chlorhydrate in acid free NaCl aqueous solution
Authors: Lárez Velásquez Cristóbal , Sánchez Albornoz Joel , Millán Barrios Enrique
Published: August 2014

Two salts of the biopolymer chitosan were prepared in aqueous medium by employing an excess of HCl or HNO3 in order to ensure neutralization of all NH2-chitosan groups. Chitosan salts were extensively dialyzed in dionised water and dried at 40 ºC until film formation. The films were characterized by thermogravimetry, FTIR and conductimetric tritration. QH+Cl− and QH+NO3− salts were viscosimetrically evaluated in free acid aqueous solutions in the presence of NaCl to control ionic strength of the medium. Unexpected high intrinsic viscosity values were obtained at low ionic strength when QH+NO3− salt were evaluated. Smidsrod´s approach was employed to estimate the stiffness parameter of both salts and B = 0.084 and 0.120 for QH+Cl− and QH+NO3−, respectively, were obtained.
Preparation and characterization of thermo-sensitive micelles composed of PSt-b-P(DEA-co-DMA)
Authors: Bian Fengling , Xiang Miao , Yu Wei , Liu Mingzhu
Published: August 2014

The amphiphilic block copolymer polystyrene-b-poly(N,Ndiethylacrylamide- co-N,N-dimethylacrylamide) (PSt-b-P(DEA-co-DMA)) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of DEA and DMA using PSt as macro chain transfer agent (PSt CTA) and N,N-azobisisobutyronitrile (AIBN) as initiator. Polymeric micelles were prepared by dialysis of the block copolymer solution in tetrahydrofuran (THF) against aqueous media. The polymeric micelles PM73 based on block copolymer P73, which was prepared with molar ratio DEA/DMA/PSt CTA/AIBN = 700:300:10:1, exhibited a lower critical solution temperature (39.2°C) in aqueous solution which was a little higher than the human body temperature. Polymeric micelles PM73 showed a unimodal size distribution with an average diameter of 24.2±0.5 nm. The micelles were thermodynamically stable in aqueous media above the critical micelle concentration (1 mg/l). The anti-inflammation drug, prednisone acetate, was incorporated into PM73 as the model drug. The loading capacity was found to be around 8 wt%, and the drug-loaded micelles showed similar size distribution patterns (monodisperse with an average diameter of 32.1±0.5 nm) and morphology (spherical) to the empty micelles. The drug-loaded micelles showed remarkable thermoresponsive drug release behavior, in response to the micellar structural change.
Studies on the synthesis, characterization and application of a novel copolymer macromonomer for polymeric solidsolid phase change materials
Authors: Xi Peng , Gu Xiao-hua , Cheng Bowen
Published: August 2014

A novel copolymer as a macromonomer with a polyethylene glycol (PEG) unit as the phase change element and a vinyl group was synthesized for the preparation of polymeric solid-solid phase change materials. The IR, 1HNMR, DSC and WAXD and POM were employed to determine the structure and properties of the novel monomer. The results show that the novel monomer possess steady molecular structure, excellent crystal properties, higher phase change enthalpy and reactivity. Furthermore, the novel polymeric solid-solid phase change material was also prepared via the copolymerization of the novel copolymer macromonomer and styrene. The phase change properties of the polymeric solid-solid phase change material were characterized.
The curing behavior of the epoxy/dicyandiamide (DICY)/2- methylimidazole system with intercalated clays
Authors: Hong Shinn-Gwo , Kuo Chia-Wei
Published: August 2014

The curing behavior of the epoxy/dicyandiamide/2-methylimidazole system in the presence of montmorillonite clays intercalated with different compounds are analyzed by Fourier transform infrared spectroscopy (FTIR) and with differential scanning calorimetry (DSC). The properties of intercalated clays were analyzed by X-ray diffraction and thermal gravimetric analysis (TGA) and it was obtained that the d-spacing of different intercalated clays follows the order of the siloxane-clay>org-clay>epoxy resin-clay>pristine clay; this trend is consistent with the amount of intercalated chemicals obtained from TGA. The results of FTIR and DSC indicate that the curing exotherms, curing rates, formed functional groups, and curing mechanisms (reaction order) of the epoxy resin system are affected by the curing temperature and the type of intercalated clay used because of the stoichiometric imbalance of reactive groups resulted from the mutual diffusion of epoxy resin constituents and intercalated chemicals. The curing heats of the epoxy resins with different clays are in the order of the epoxy resin-clay> siloxane-clay>org-clay. It is shown that the Kamal model when applied can correctly describe the curing kinetics of the studied epoxy resin/clay systems at 160 and 170°C.
Preparation of poly(ε-caprolactone) and its nanocomposites in ε-caprolactam
Authors: Kredatusová Jana , Svobodová Jana , Brožek Jiří
Published: August 2014

The solution polymerization of ε-caprolactone (CLO) initiated with stannous 2-ethylhexanoate has been studied in the temperature range 90 - 150 °C. ε-Caprolactam (CLA) was used as a solvent. Although relatively high polymerization temperature was used poly(ε-caprolactone) (PCLO) was formed solely and no CLA structural units were incorporated into its chains. The polymerization rate increased with CLO content in feed and polymerization temperature. A linear dependence of molar mass on yield of PCLO indicates living character of polymerization. When polymerization was carried out in the presence of organically modified MMT, nanocomposites PCLO - layered silicate with an exfoliated structure were obtained
Gels from acrylic acid and hydroxypropyl cellulose via free radical polymerization
Authors: Castro-Guerrero Carlos F. , Morales-Cepeda Ana , Rivera-Armenta José , Mendoza-Martínez Ana , Álvarez-Castillo Alberto
Published: August 2014

A hydrogel from acrylic acid and hydroxypropyl cellulose was made. The percentages of raw materials and crosslinkers were varied and its swelling behavior was evaluated. Some of the gels obtained absorbed more than 300% wt. The gels with higher swelling percentages were characterized by means of IR spectroscopy, differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and scanning electron microscopy (SEM). The FTIR showed the presence of the main reactants in the gel, while the DSC showed a phase separation in the gel. This gel is partly biodegradable because of the content of hydroxypropyl cellulose and has the viscoelastic properties of poly(acrylic acid).
First example of polystyrene end-functionalized with excited state intramolecular proton transfer (ESIPT) fluorophore by ATRP method
Authors: Lu Jianmei , Zhang Liang , Xu Qingfeng , Li Najun , Yan Feng , Xia Xuewei , Wang Lihua , Zhou Qiuxuan
Published: August 2014

A novel initiator, 2-benzothiazol-2-yl-5-bromomethyl-phenol (BYBP) containing excited state intramolecular proton transfer (ESIPT) fluorophore was synthesized. Atom transfer radical polymerization (ATRP) of styrene was conducted successfully using BYBP as initiator, cuprous bromide (CuBr)/N,N,N’,N”,N’-pentamethyldiethylenetriamine (PMDETA) as catalyst, and cyclohexanone/DMF (mcyclohexanone: mDMF = 1: 1) as solvent. Factors such as the reaction temperature and molar ratio of catalyst to initiator, which could affect the ATRP system, were discussed in the paper. Chain extension was conducted using polymer as the macro-initiator which was characterized via 1H NMR. The optical property of initiator was well preserved in the obtained polystyrene, and the endfunctionalized polystyrene exhibited obvious fluorescent emission at about 530 nm.
Preparation and characterization of poly(hydroxyurethane) /halloysite nanocomposites via in-situ polymerization
Authors: Tang Zhaobin , Liu Peng , Guo Jinshan , Su Zhixing
Published: August 2014

Naturally occurring halloysite nanotubes (HNTs) with hollow nanotubular structures were used as a new type filler for polyhydroxyurethane. The polyhydroxyurethane/halloysite nanocomposites (PHU/HNTs) were prepared by the in-situ surface-initiated polymerization of a five-membered cyclic carbonate 2,2- bis[p-(1,3-dioxolan-2-one-4-yl-methoxy) phenyl] propane (B5CC) and hexa methylene diamine, from the surfaces of the aminopropyl halloysite nanotubes (APHNTs) for the first time. The percentage of grafting (PG %) and the grafting efficiency (GE %) of 41% and 23% were calculated from the results of the thermogravimetric analysis (TGA) and from the results of elemental analysis (EA) respectively after the free polyhydroxyurethane was washed off. The chemical grafting of the polymer was also confirmed using FTIR; the morphology of the silica nanotubes in the nanocomposite was examined by transmission electron microscope (TEM).
Unique structure and property of cyclodextrin and its utility in polymer synthesis
Authors: Hu Jie , Huang Rong , Cao Shunsheng , Hua Yinqun
Published: August 2014

Owing to their unique structure and property, natural cyclodextrins and their chemically modified derivatives can include many kinds of organic monomers to form guest/host complexes. The formation of these complexes results in significant changes of the solubility and activity of the guest molecules, but without chemical modification. It is found that the complexed hydrophobic monomers can be successfully polymerized directly in water without any organic solvent or surfactant, which induces a green way to polymer synthesis. It is found that this new cyclodextrin-mediated polymerization method differs strongly from classical methods. The present article reviewed the formation and the structure of the cyclodextrin/monomer inclusion complexes, and the influence of cyclodextrins on polymer synthesis. At last, the possible theory of the cyclodextrin-mediated reaction is discussed.
Application of ionic liquid [bmim]PF6 as green plasticizer for poly(L-lactide)
Authors: Zhang Puyu , Peng Lichao , Li Wenbin
Published: August 2014

Ionic liquid [bmim]PF6 (1-butyl-3-methylimidazolium hexafluoro phosphate) was synthesized and characterized. It was used as the plasticizer for poly(L-lactide) (PLLA). The glass transition temperature (Tg) and the thermal stability of the plasticized PLLA samples were measured by thermogravimetry (TG) and differential scanning calorimetry (DSC). Compared with poly(ethylene glycol) having Mw of 300 g/mol (PEG300), TG results showed that the thermal stability of PLLA plasticized with ionic liquid was better than that of PLLA plasticized with PEG300. The Tg of plasticized PLLA decrease with increasing the content of ionic liquid [bmim]PF6 from 2 wt.% to 10 wt.%. The Tg of PLLA can be reduced to 40°C when the content of ionic liquid [bmim]PF6 was 10 wt.%. The materials of PLLA with plasticizer were also investigated using polarizing microscope (POM), the results of which indicate that the movements of PLLA chains were improved when ionic liquid plasticizer was used.
Dispersion, mechanical and thermal properties of nano graphite platelets reinforced flouroelastomer composites
Authors: Xu Deng , Sridhar V. , Pham Thanh Tu , Kim Jin Kuk
Published: August 2014

The potential of exfoliated graphite nano platelets (xGnP™) as reinforcing fillers in flouroelastomer has been investigated. The dispersion of the nano graphite platelets in the polymer matrix has been investigated by WAXD, SEM, TEM, EPMA and AFM. WAXD studies indicated that the processing of composites did not change the inter-gallery distance (d-spacing) of the graphite platelets. The effect of increasing nano graphite loadings on mechanical properties like tensile strength, modulus and tear resistance has been studied. Formation of weld lines on the fracture surface of the composite has been observed by SEM. The thermal stability was determined using thermogravimetric analysis. The composites showed higher thermal stability in comparison with nonreinforced polymer.
AGET ATRP of Acrylamide in Aqueous Media
Authors: Tan Ying , Yang Qingbo , Sheng Dekun , Su Xuefeng , Xu Kun , Song Chunlei , Wang Pixin
Published: August 2014

The recently developed initiation system, the activator generated by electron transfer (AGET) was used in atom transfer radical polymerization (ATRP) to synthesize well-controlled polyacrylamide in aqueous media at 25°C. The different reducing agents involved ascorbic acid and glucosa; well-controlled polymers were obtained when ascorbic acid was used as water-soluble reducing agent. The polymerizations targeted at degrees of polymerization in the range of 400 resulted in polymers with low polydispersity indices. Moreover, first order plots were linear.
Synthesis and swelling behaviour of fast-swelling superabsorbent composites
Authors: Zhang Fen , Liu Mingzhu , Qi Xiaohua , Chen Zhenbin
Published: August 2014

Fast-swelling porous superabsorbent composites with high water absorbency in 0.9 wt% NaCl solution both at atmospheric pressure and under certain load (p ≈ 2×103 pa) were synthesized by a rapid solution polymerization of concentrated sodium acrylate, acrylamide and 2-hydroxypropyl acrylate. The porosity was induced through foaming conducted in the course of polymerization using acetone as porosity generator. The copolymerization and surface morphology of the porous copolymers were characterized by FTIR and SEM. To improve other properties of swollen hydrogel such as strength, resilience and dispersion, the copolymers were modified with inorganic salts after surfacecrosslinking by trihydroxymethyl propane glycidol ether. The influences of various experimental conditions, such as neutralization degree of acrylic acid, amount of initiator and crosslinker on the water absorbent capacity in 0.9 wt% NaCl solution were investigated. The resulting products under optimum conditions possessed the water absorbency of 65 g g-1 and 10 g g-1 in 0.9 wt% NaCl solution at atmosphere pressure and under load, respectively. The results of swelling kinetics measurement in 0.9 wt% NaCl solution showed that the composites had very fast swelling rate (they can reach swelling equilibrium in minutes). In addition, the effect of amount of acetone on swelling rate of the composites was examined in detail. It was shown that appropriate amount of acetone caused products with high porosity, which led to large swelling rate. Moreover, the swollen hydrogel exhibited excellent strength, better resilience and dispersion.
Sulfur containing optical plastics and its ophthalmic lenses applications
Authors: Jha G. S. , Seshadri G. , Mohan A. , Khandal R. K.
Published: August 2014

Plastics produced from the sulfur-based monomer are excellent materials with many optical applications such as ophthalmic lenses, fiber optics and non- linear optics. High refractive index plastic materials are able to reduce the curvature, edge and center thickness of lenses. Sulfur containing plastics such as sulfide, polysulfide, and sulfur containing vinyl compound, thioacrylate, polythiol and isocyanate/isothiocyanate based monomers have demonstrated high refractive index, high Abbe number, good impact strength, excellent machinability, good tintability and good transmittance. In the present article, various sulfur containing plastics with different types of monomers for ophthalmic lens applications are reviewed.
Using dioxane and water as mixed solvents to prepare pH and temperature dual responsive poly(N-isopropyl acrylamide-co-itaconic acid) hydrogels
Authors: Ling Youdao , Lu Mangeng
Published: August 2014

pH and temperature dual responsive hydrogels based on itaconic acid (IA) and N-isopropylacrylamide (NIPAAm) were prepared by means of water and dioxane as mixed solvents. The chemical compositions, structures and morphologies of these hydrogels were characterized by FTIR, TGA and SEM, and their pH and temperature responsive behaviours were investigated through equilibrium swelling ratios, deswelling and reswelling kinetics. The results showed the hydrogels fabricated in this condition had expanded chain conformations and macroporous network structures, and exhibited the larger swelling ratios as well as improved deswelling/reswelling dynamics.
Impedance analysis and electromagnetic interference shielding effectiveness of vapor grown carbon nanofiber reinforced chlorobutyl rubber composites
Authors: Sridhar V. , Xu Deng , Tripathy D.K. , Kim Jin Kuk
Published: August 2014

The effect of processing variables (filler loadings) and operating variables (frequency) on the impedance and electromagnetic interference shielding effectiveness of vapor grown carbon nanofiber (VGCNF) reinforced chlorobutyl vulcanizates has been investigated. The dispersion and morphology of the VGCNF in the polymer matrix has been studied by scanning electron microscopy and Raman spectra. Addtionally, the utility of EPMA (Electron probe microanalyzer) as a tool to study the dispersion of nano fibers in polymer matrix has been explored for the first time. With increase in frequency and VGCNF loadings the composites showed a decrease in real part of complex impedance for increasing VGCNF loadings whereas the imaginary part showed a slight peak in the range of 9-10 GHz followed by a subsequent decrease. The measured impedance values were plotted as Nyquist plots (Argand diagrams) and a Resistor-Capacitance model was assumed. The EMI shielding effectiveness increased monotonically with filler loading and showed a maximum of around 55 dB at 12 phr loadings, thus making them suitable for EMI shielding applications.
A review on aromatic poly(ester-carbonate)s and transesterification resistant polyesters
Authors: Montaudo Maurizio S.
Published: August 2014

The review discusses poly(ester-carbonate)s (PECAs for brief), their production, characterization and their use. Great emphasis is on their production via ester-carbonate exchange and in particular on the copolymer obtained when mixing and heating poly(butylene terephthalate) (PBT for brief) or poly(ethyylene terephthalate) (PET for brief) together with poly(bisphenol A carbonate) (PC for brief). Some notes are added on PECAs with long polyester and /or long polycarbonate blocks and for the case of "transesterification resistant" polymers i.e. when the production of random copolymers via ester-carbonate exchange is impossible under ordinary conditions.
The use of crude tall oil as feed-stock for alkyd resins
Authors: Suarez Paulo A. Z. , Einloft Sandra , de S. Basso Nara R. , Fernandes Jonas A. , da Motta Ladimir , do Amaral Lisandra C. , Lima Daniella G.
Published: August 2014

The synthesis of modified alkyd resins using a crude tall oil with a content of rosin acids of 39.8 % is described. This material has the composition of fatty acids close to soybean oil, has low cost and is widely available being a forest product industrial residue. The synthetic route includes the reaction of tall oil and maleic anhydride, in the presence of the catalyst (LiOH), followed by polyesterification reaction steps, resulting in an alkyd resin with interesting properties. The acid value (AN) and viscosity were used to follow the reaction, and it appears to be dependent upon the polyalcohol used in the polyesterification step. A period of 15 hours was needed to yield a tack-free coating.
Synthesis and characterization of new disilane -containing arylacetylene resin
Authors: Yin Guoguang , Zhang Jian , Wang Canfeng , Huang Farong , Du Lei
Published: August 2014

A novel disilane-containing arylacetylene resin, abbreviated as DSA resin, was synthesized from diethynylbenzene and halogenated disilane by Grignard reaction. The obtained resin was a viscous liquid and soluble in a variety of common solvents. The structures and properties of the resin, cured resin and sintered resin were characterized by FT-IR, 1H-NMR, DSC, TGA and XRD techniques. The results showed that the DSA resin could cure at temperatures lower than 200°C and the cured resin exhibited high temperature resistance and good ceramic formability.
Structural and dielectric properties of some epiclon-based polyimide films
Authors: Cosutchi Andreea Irina , Hulubei Camelia , Stoica Iuliana , Dobromir Marius , Ioan Silvia
Published: August 2014

Surface and electrical properties of two flexible and cross-linked epiclon based polyimide films were investigated. Surface tension measurements indicate an increased hydrophobicity due to both isothermal treatment - which induces imidization and cross-linking - and to the chemical structure, characterized by the different number of ether linkages in the polyimide backbone. Morphology of film surfaces, modified by plasma treatment, shows high roughness and, implicitly, improved adhesion, as required in electronics. The studied polyimides exhibit low dielectric constants and dielectric losses, comparatively to conventional aromatic polyimides. The electrical conductance and resistivity characteristics of these polymers recommend them as good insulators for dielectric layers in microelectronic applications.
Poly(4-methyl-1-pentene)/MWNT nanocomposites
Authors: Patil Prashant A , Wanjale Santosh D , Jog Jyoti P.
Published: August 2014

Nanocomposites of poly(4-methyl-1-pentene) (PMP) with various weight fractions of multiwall carbon nanotubes (MWNT’s) were prepared by melt compounding. The nanocomposites are characterized for structure using scanning electron microscopy. The viscoelastic behavior of the nanocomposites is investigated in solid as well as melt state. The study reveals a significant increase in storage modulus especially in the rubbery regime of the polymer matrix and reduced tan δ. Rheological properties in melt show that the complex viscosity and shear storage modulus are increased as a result of incorporation of MWNT. A systematic decrease in the cross over frequency is noted which is attributed to the increased relaxation time. In dielectric analysis, composition dependent enhanced permittivity and conductivity are observed. The thermal stability of the polymer is found to be significantly improved in presence of MWNT’s.
Thermal stability, mechanical and adsorption resistant properties of HDPE/PEG/Clay nanocomposites on exposure to electron beam
Authors: Mohaddespour Ahmad , Javad Ahmadi Seyed , Abolghasemi Hossein , Jafarinejad Shahryar
Published: August 2014

The Influence of electron beam on behaviors of high density polyethylene/poly(ethylene glycol)/organoclay nanocomposites has been studied. Nanocomposite compounds were prepared by melt intercalation method. X-ray diffraction (XRD) and transition electron microscopy (TEM) revealed the combination of nanocomposite morphology. Thermal and mechanical properties of nanocomposites were studied by using Thermogravimetric analysis (TGA), Young's modulus, tensile strength and hardness tests. The results show that at 500 KGy dose of irradiation the Young’s modulus and tensile strength values have been enhanced in comparison with pure blend by cross-linking and the surface hardness of samples raises by increasing the clay content The samples with the clay content of 5 wt% in the matrix with 500KGy dose of irradiation have shown satisfactory thermal resistance.

The irradiation at high levels has degraded the nanocomposites and an optimum dose must be employed to enhance their properties. The presence of poly(ethylene glycol) as a compatibilizer has improved the dispersion of clay layers into the matrix and has enhanced the mechanical properties and thermal resistance of nanocomposites. The presence of the clay in the matrix has increased the adsorption amount of xylene and toluene into the bulk of nanocomposites and the irradiation has decreased this capacity by the dose level.
Characterization of the surface and mechanical behavior of polyurethane microporous films doped with silver nanoparticles
Authors: Ciobanu Liana Cătălina , Ciobanu Constantin
Published: August 2014

The aim of this study was to investigate the effects of silver nanoparticles (Ag-NPs) concentration on surface of polyurethane microporous films. The Ag-NPs have a diameter between 1.74-10 nm and were synthesized in the polymer matrix. The effects of Ag-NPs at the surface of polyurethane (PU) microporous films were investigated by means of attenuated total reflection Fourier infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM) and contact angle measurements. The mechanical behavior of PU films vs Ag-NPs concentration was also studied. The Ag-NPs induce changes in the PU surface structure, wettability properties, topography and mechanical properties. These phenomena may be due to interactions between Ag-NPs and urethane groups which form new structure urethane-silver-urethane with a specific morphology and the nanostructuring of the surface by means of metallic nanoparticles.
Study of thermal properties of difunctional benzoxazines
Authors: Zhao Chun’e , Xu Guoliang , Zeng Ke , Miao Peikai , Zhou Hongfei , Wang Yipeng , Liu Tao , Yang Gang
Published: August 2014

Three difunctional benzoxazine monomers bis (3,4-dihydro-2H-3-phenyl- 1,3-benzoxazinyl) methane, (abbreviated as BF-a), bis (3,4-dihydro-2H-3-phenyl-1, 3-benzoxazinyl) isopropane, (abbreviated as BA-a), bis (3,4-dihydro-2H-3-phenyl- 1,3-benzoxazinyl) biphenyl, (abbreviated as BP-a) were successfully synthesized via phenol (bisphenol A, 4,4’-Biphenol, bisphenol F), aniline and paraformaldehyde. Their structures were identified by 1H NMR and FT-IR. The monomers were thermally treated at 200 oC for 2 h in nitrogen to give corresponding prepolymers. The thermal properties of the monomers were investigated by TGA under nitrogen atmosphere. The thermal properties of the prepolymers were investigated by TGA under nitrogen and air atmosphere. It was found that the monomers of BF-a and BA-a showed lower melting points and exhibited wider processing windows than BP-a. The prepolymer from BP-a showed good thermal stabilities, compared with the prepolymers from BF-a and BA-a.
Effects of feed rate and solution conductivity on jet current and fiber diameter in electrospinning of polyacrylonitrile solutions
Authors: Fallahi Delaram , Rafizadeh Mehdi , Mohammadi Naser , Vahidi Behrooz
Published: August 2014

Electrospinning of solutions of polyacrylonitrile in dimethylformamide (PAN/DMF) were performed under different voltages at different constant feed rates and the jet electric current was measured. The effects of applied voltage, feed rate and solution conductivity on jet electric current and fiber diameter were investigated. The results showed that the feed rate had no effect on jet current and fiber diameter, whereas by increasing the applied voltage and solution conductivity, both the jet current and fiber diameter were increased.
Accuracy in locating glass transitions: aging and gamma sterilization of vulcanized thermoplastic elastomers
Authors: Brostow Witold , Deshpande Sameer , Pietkiewicz Dorota , Wisner Steven R.
Published: August 2014

We have studied nine thermoplastic vulcanizate elastomers (TPVs) in four series: as made, after accelerated aging, after γ irradiation, after both irradiation and aging. The materials exhibit two glass transitions, one seen in crosslinked regions and the other in un-crosslinked amorphous regions. Three techniques of determination of glass transitions have been used and the results compared, all three based on dynamic mechanical analysis (DMA): as a peak in the loss modulus E’’; as a peak in tan δ; and as the midpoint of the rapid decrease in the storage modulus E’. We recommend the last method for both fundamental and practical reasons.
Effectiveness of heat protection of fabrics loaded with phase change materials
Authors: Fallahi Elham , Barmar Mohammad , Kish Mohammad Haghighat
Published: August 2014

Among different natural and non-corrosive products paraffin wax and camel fat are selected as phase change materials (PCM). These PCMs are applied to glass, polyester/viscose and wool/polyester woven fabrics. To examine their efficacy, their thermal behavior in a condition similar to the actual end uses is measured. Chemical nature and thermal properties of the PCMs are measured by Fourier transform infrared spectroscope and differential scanning calorimeter. A relation based on the principle of heat transfer is used to determine the temperature of a thermometer covered by fabrics loaded with PCMs. A simple exponential relation explains the experimental results. For glass and polyester/viscose fabrics use of these PCMs leads to substantial delays in the temperature changes. The important parameters for the evaluation of the products are discussed.
Thermal decomposition studies of highly alternating CO2- cyclohexene oxide copolymer
Authors: Jianxin Luo , Min Zhang , Zhiqiang Zou , Baohua Liu , Liban Chen
Published: August 2014

Highly alternating CO2-cyclohexene oxide copolymer, namely poly(cyclohexene carbonate) (PCHC), considered potentially to be microelectronic sacrificial material, was successfully synthesized by copolymerization of cyclohexene oxide and CO2 in the presence of SalenAl(OiPr) catalyst. The obtained highly alternating PCHC copolymer were determined and proven to have superior thermal decomposition properties decomposing completely at 350 oC by thermogravimetric (TG) analysis under dynamic conditions. The thermal decomposition kinetics of the obtained PCHC was investigated by a different kinetic method using data from TG analysis. Based on the analytical, kinetic parameters were calculated and kinetic model of pyrolysis was proposed. TG-IR, Py-GC/MS, IR and 1H NMR techniques were applied to investigate the decomposition process. Based on Py-GC/MS and TG-IR techniques, carbon dioxide, 1,3-cyclohexadiene, cyclopentanecarboxaldehyde, cyclohexene oxide, cyclohexanone and trans-1,2- carbonyldioxycyclohexane were identified as thermal decomposition products of PCHC. The solid residues of the PCHC with 25% ether linkages decomposed at 200, 250, 300, 350 oC as determined by IR and 1H NMR. The results demonstrated that the carbonate content of the solid residues decreased gradually at elevated heat-temperatures and at 350 oC only few polyether linkages were observed.
Extremely high photocatalytic activity of polymer nanospheres embedded with CdS nanoparticles prepared by a novel method
Authors: Wu Yuanpeng , Gao Yongyi , Ding Xiaobin , Zheng Zhaohui , Peng Yuxing
Published: August 2014

A novel, practicable and convenient route has been developed to prepare polymer nanospheres embedded with CdS nanoparticles which show an extremely high photocatalytic activity compared with other photocatalysts. In this method, polymer nanospheres were fabricated through the polymerization of cadmium dimethacrylate which was introduced into self-assembly system of chitosan and 3-mercaptopropionic acid. Then CdS nanoparticles were prepared insitu by inflating H2S into the polymer nanospheres.
Polyamide/layered silicate nanocomposites: A correlation between fracture toughness and molecular mobility
Authors: Kotek Jiří , Kelnar Ivan , Brus Jiří , Urbanová Martina
Published: August 2014

This study correlates toughness of polyamide nanocomposites with the molecular mobility of polymer segments in the amorphous phase. Two nanocomposite systems prepared by melt-compounding of polyamide-6 with sodium montmorillonite or organophilized montmorillonite were compared. They differed in the extent of silicate dispersion. While sodium montmorillonite formed intercalated nanocomposites, the organophilization promoted full exfoliation of the silicate layers in the matrix. The different morphology was imprinted in fracture behaviour, toughness of exfoliated nanocomposites was markedly lower that that of their intercalated counterparts. To explain this difference, a solid-state NMR was used as a selective tool for providing information about nanocomposites structure and, primarily, about dynamics of polymer segments. Comparison of NMR spinrelaxation behavior with fracture mechanics experiments revealed a close correlation between fracture toughness and the intensity of rapidly relaxing component of the amorphous phase.
Effect of calcium neutralization on elastic and swelling properties of crosslinked poly(acrylic acid) - correlation to inhomogeneities and phase behaviour
Authors: Larsson Mikael , Gustafsson Stefan , Olsson Eva , Larsson Anette
Published: August 2014

Crosslinked hydrogels of poly(acrylic acid) neutralized with calcium hydroxide were synthesized using free radical co-polymerization. The effects of the amount added calcium on the elastic modulus and swelling properties of the gels and the correlation to phase behaviour and structural changes within the gels were studied using texture analysis, gravimetric analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and atomic force microscopy (AFM). It was found that the elastic modulus decreased nonlinearly with increasing amount of added calcium and that the swelling’s dependence on the amount of added calcium was complicated. The maximum swelling increased with increasing amount of added calcium until a critical calcium content was reached, upon which the gels phase separated, with a strong decrease in swelling as a result. The changes in properties are explained by the fact that calcium affects the structure of the polymer network during synthesis and by the phase behaviour of the gels. Changes in the gel structure with the addition of calcium were detected with AFM. Furthermore, AFM revealed different phases on the nanometre scale for the sample with a calcium content around which phase separation is macroscopically observed. Finally, it was shown that the sulphur from the initiator potassium persulfate formed crystal like regions with high sulphur and calcium content upon drying of the hydrogels.
Effects of polypropylene-g-dibutyl maleate on mechanical and rheological properties of PP/PA6 blends
Authors: Li Duxin , Ou Baoli , Jia Demin
Published: August 2014

The effects of polypropylene-grafted-dibutyl maleate (PP-g-DBM) used as compatibilizer on mechanical, rheological and morphological properties of polypropylene (PP) and nylon 6 (PA6) blends was systematically investigated in this paper. The results of Molau test, solvent extraction and differential scanning calorimetry (DSC) indicated the formation of PP-g-PA6 in vicinity of interfaces during melting extrusion. Owing to the reaction between the reactive groups of PPg- DBM and amine (-NH2) end groups of PA6, the tensile and impact strength of the PP-g-DBM compatibilized PP/PA6 blends were much higher than that of the uncompatibilized PP/PA6 blends. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated that the domain sizes of the dispersed phase in the compatibilized PP/PA6 blends decreased and the interfaces become more indistinct, which indicated a clear compatibiliting effect was induced by the PP-g-DBM in the immiscible PP/PA6 blends, i.e. the PP-g-DBM was an effective compatibilizer for the PP/PA6 blends. In addition, the rheological measurements showed the PP-g-DBM compatibilized PP/PA6 blends possessed higher pseudo plasticity, melt viscosity and flow activation energy.
Kinetics of suspended emulsion copolymerization of acrylonitrile with itaconic acid
Authors: Yu Mengmeng , Chen Hou , Liang Ying , Cui Hengli , Zhou Wenying , Li Dongmei , Cui Xianqiang
Published: August 2014

Acrylonitrile(AN) was successfully used to copolymerize with itaconic acid (IA) by suspension emulsion polymerization at 70 ˚C under N2 atmosphere for the first time. Porous AN/IA copolymers were prepared by using potassium peroxydisulphate (KPS) as initiator, poly(vinyl alcohol) (PVA) as dispersant and Span60 as emulsifier. Kinetics of suspension emulsion copolymerization of AN with IA were studied. Effects of various mass ratios of water/monomer, initiator concentrations, emulsifier concentrations and dispersant concentrations on AN/IA copolymerization rate and changes of particle size and size distribution with the extension of polymerization time were investigated. It was found that the copolymerization rate increased with water/monomer mass ratio and KPS concentration. Span60 concentration and PVA concentration had no obvious effect on the polymerization rate. Finally, a suspension emulsion polymerization mechanism for AN and IA was proposed.
Lattice sizes, crystallinities, and spacing between amorphous chains - characterization of ethene-/ɑ-olefin copolymers with various comonomers and comonomer contents measured by wide angle X-ray scattering
Authors: Stadler Florian J. , Takahashi Tatsuhiro , Yonetake Koichiro
Published: August 2014

Ethene-/ɑ-olefin copolymers having a wide range of comonomer contents with comonomers between 4 and 26 carbon atoms in length were characterized by wide angle X-ray scattering (WAXS). It was found that the crystallinities matched fairly well with the crystallinities from DSC and volumetric measurements. An increase of the crystal lattice size was found with increasing comonomer content and comonomer length. Both are attributed to the formation of defects around these short-chain branches in the crystal lattice, which widen it. Increasing the cooling time will lead to a more densely packed crystal structure, if the quenched structure is distorted, i.e. if the sample contains comonomer. A higher molar mass Mwwidens the average space between chains in the amorphous phase as well as the addition of comonomer. The latter finding is explained by the increasing number of chain ends introduced by the comonomer which increases the free volume in the sample because of the worse amorphous packing of the chain ends.
Linear low density polyethylene (LLDPE) films containing perylene dyes as stress-strain luminescent indicators
Authors: Pucci Andrea , Donati Filippo , Ruggeri Giacomo , Ciardelli Francesco
Published: August 2014

Linear low density polyethylene (LLDPE) films containing different concentrations of perylene (P) chromophores have been prepared by solution-casting and compression-moulding. The light emission features of the films depend on P concentration and polymer films deformation. A well-defined band attributed to the formation of micro/ nano-structured perylene chromophoric aggregates is observed with more than 0.1 wt.% of P in the film. The occurrence of this phenomenon changed the emission colour of the films from a bright blue (noninteracting dyes) to low intense pale yellow (interacting dyes) colour. During film drawing the LLDPE macromolecules reorganization is able to break the P supramolecular organization, leading to the prevalence of the blue emission of monomeric P. The optical behaviour of perylene dyes acting as internal stressstrain luminescent indicators for polyethylene films, provides a powerful tool to detect macromolecular organization.
Synthesis and self-assembly of poly(ethylene oxide)-b-poly (2-hydroxyethyl methacrylate)
Authors: Yang Runmiao , Wang Yanmei , Zhou Dan , Jia Jianyong , Han Yanchun
Published: August 2014

Poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate) (PEO-b- PHEMA) was synthesized by successive atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate（HEMA） monomer using PEO-Br macroinitiator as initiator, CuBr/CuBr2 and 2,2‟-bipyridyl (bpy) as catalyst and ligand. IR, 1H NMR, and GPC analysis indicate that PEO-b-PHEMA block copolymer with low polydispersity index (Mw/Mn≈ 1.1) has been formed. Selfassembly of this double hydrophilic block copolymer in the selective solvent and water was also studied. Owing to the high hydrophilic nature of the PEO and PHEMA blocks, this double hydrophilic block copolymer cannot disperse well in water. So block copolymer was modified by part esterification of PEO-b-PHEMA with acetic anhydride, which increased the hydrophobic group of the PHEMA block. The TEM results show that this block copolymer spontaneously form well-defined micelles in water.
Viscometric and rheological study of polyacrylonitrile solutions
Authors: Brunchi Cristina-Eliza , Bercea Maria , Morariu Simona
Published: August 2014

The viscometric behaviour of polyacrylonitrile solutions in dimethylformamide has been examined in dilute and extremely dilute regimes of concentration. For semidilute and concentrated solutions, viscoelastic properties were determined and discussed. The overlap concentration was evidenced as being the crossover of two scaling laws characterizing the entangled and nonentangled solution regimes.
Prediction of crystallinity profile and eject time of injection molded parts using finite element method (FEM)
Authors: Mostafaiyan Mehdi , Sharif Farhad
Published: August 2014

Quality of injection molded parts of semi-crystalline polymers has been the subject of intense interest from both analytical and industrial points of view. Crystallinity profile plays an important role in determining mechanical properties of a part and its quality. Therefore it is important to analyze the effect of injection molding parameters on the crystallinity profile of the molded parts. In this study, finite element analysis has been used to solve the equations of mass, momentum, and energy conservation simultaneously with the equation of crystallization kinetics to predict melt front, its solidification and crystallinity profile. The results from our numerical analysis have been compared with the reported experimental results. Furthermore, progress of the crystallization is proposed to be a proper criterion for estimation of the eject time. Finally, the effects of mold and melt temperature on the eject time; part temperature and average degree of crystallinity, for a specific compound are also presented.
Microwave-assisted synthesis and characterization of some optically active poly(ester-imide) thermoplastic elastomers
Authors: Zahmatkesh Saeed , Hajipour Abdol Reza
Published: August 2014

Pyromellitic dianhydride (1) was reacted with L-leucine (2) to result in [N,N'-(pyromellitoyl)-bis-L-leucine diacid] (3). This compound (3) was converted to N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride (4) by reaction with thionyl chloride. The microwave-assisted polycondensation of this diacid chloride (4) with polyethyleneglycol-diol (PEG-200) and/or three synthetic bisphenols furnish a series of new PEIs and Co-PEIs in a laboratory microwave oven (Milestone). The resulting polymers and copolymers have inherent viscosities in the range of 0.31- 0.53 dl g-1. These polymers are optically active, thermally stable and soluble in polar aprotic solvents such as DMF, DMSO, NMP, DMAc and sulfuric acid. All of the above polymers were fully characterized by IR spectroscopy, 1H NMR spectroscopy, elemental analyses, specific rotation and thermal analyses. Some structural characterizations and physical properties of these optically active PEIs and Co-PEIs are reported.
Novel electron-acceptor conjugated polymer materials based on poly(thienylene ethynylene) derivatives
Authors: Liu Kuan , Li Yang , Yang Mujie
Published: August 2014

Novel electron-acceptor materials based on poly(thienylene ethynylene) derivatives (PTE-BT and PTE-DCNTB) were synthesized and characterized by FTIR spectroscopy. Their thermal, electrochemical and optical properties were investigated. The π-conjugated polymers are soluble in common organic solvents. The maximum UV-Vis absorptions of PTE-BT and PTE-DCNTB in solution are observed at 460 and 390 nm, respectively. The electrochemical band gap was found to be 1.89 eV for PTE-BT and 2.01 eV for PTE-DCNTB. Both polymers are promising as electron-acceptor materials for photovoltaic applications.
pH-Driven synthesis of collagen-silica nanohybrids
Authors: García-Valdés C. J. , Hernández-Padrón G. , García-Garduño M. V. , Castaño V. M.
Published: August 2014

Immobilization of the protein collagen Type I into transparent porous silica matrices produced by the sol-gel process was achieved by using a high concentration of precursor and a low pH. Surface silanol groups interact chemically with the amide and carboxylic groups of the collagen Type I to produce a novel nanohybrid.