Brittle-tough transition in PP/EPDM blends: effects of interparticle distance and tensile deformation speed

The toughness of polypropylene (PP)/ethylene-propylene-diene monomer rubber (EPDM) blends containing various EPDM contents as a function of the tensile speed was studied. The toughness of the blends was determined from the tensile fracture energy of the side-edge notched samples. A sharp brittle-tough transition was observed in the fracture energy versus interparticle distance (ID) curves when the crosshead speed < 102.4 mm/min. It was observed that the brittle-ductile transition of PP/EPDM blend occurred either by reducing ID or by decreasing the tensile speed. The correlation between the critical interparticle distance and tensile deformation rate was compared with that between the critical interparticle distance and temperature for PP/EPDM blends. (C) 2000 Elsevier Science Ltd. All rights reserved.

Impedance study of (PEO)(10)LiClO4-Al2O3 composite polymer electrolyte with blocking electrodes

A composite solid polymer electrolyte (SPE) of (PEO)(10)LiClO4-Al2O3 was prepared and Pt and stainless steel(SS) blocking electrodes were used for an impedance study. It was found that the semicircle in the high frequency range and the straight line in the low frequency range depend upon different blocking electrodes and polarization potentials applied in the experiments. In the equivalent circuit. two constant phase elements (CPE) have been used instead of the pure geometrical and double layer capacitances. respectively. A theoretical line calculated from their estimated values has a good correlation with the experiment data. Moreover. the equivalent circuit also can be used to explain the impedance properties of Pt and stainless steel (SS) blocking electrodes both in the high and the low frequency ranges. (C) 2001 Elsevier Science Ltd. All rights reserved.

Study of the conductivity and side chain mobility of a comb-like polymer electrolyte using the dynamic mechanical method

Using poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether (PEGME) with different molecular weights as side chains, three comb-like polymers and their Li salt complexes were synthesized. The dynamic mechanical properties and conductivities were investigated. Results showed that the polymer electrolytes possess two glass transitions: alpha -transition and beta -transition, and the temperature dependence of the ionic conductivity shows WLF (Williams-Landel-Ferry) behavior. Based on the time-temperature equivalence principle, a master curve was constructed by selecting T-beta as reference temperature. The values of the WLF parameters (C-1 and C-2) were obtained and were found to be almost independent of the length of the PEGME side chain and the content of Li salt. By reference to T-0 = 50 degreesC. the relation between log tau (c) and c was found to be linear. The master curves are displaced progressively to higher frequencies as the molecular weight of the side chain is increased. The relation between log tau (n) and the molecular weight of the side chain is also linear. (C) 2001 Elsevier Science B.V. All rights reserved.

Water soluble polyaniline and its blend films prepared by aqueous solution casting

Polyaniline (PAn) was doped with phosphonic acid containing hydrophilic tails. The solubility of the doped PAn in water was controlled by changing the length of hydrophilic chain in the dopant. When poly(ethylene glycol) monomethyl ether (PEGME) with molecular weight M-w = 550 was used as the hydrophilic chain of the dopant, the doped PAn was entirely soluble in water. The film cast from aqueous solution showed good electrochemical redox reversibility, Aqueous solution blending of PAn with poly(ethylene glycol) (PEG, M-w = 20 000) and poly(N-vinyl pyrrolidone) (PVP, M-w = 360 000) was achieved. Percolation threshold of the composite film was lower than 3 wt.%. Electrical conductivity of the composite film was in the range of 10(-1)-10(-5) S cm(-1), depending on molecular weight of the acid and the content of PAn in the composite. (C) 1999 Elsevier Science Ltd. All rights reserved.

Processible nanostructured materials with electrical conductivity and magnetic susceptibility: Preparation and properties of maghemite polyaniline nanocomposite films

We here present a versatile process for the preparation of maghemite/polyaniline (gamma-Fe2O3/ PAn) nanocomposite films with macroscopic processibility, electrical conductivity, and magnetic susceptibility. The gamma-Fe2O3 nanoparticles are coated and the PAn chains are doped by anionic surfactants of omega-methoxypoly(ethylene glycol) phosphate (PEOPA), 4-dodecylbenzenesulfonic acid (DBSA), and 10-camphorsulfonic acid (CSA). Both the coated gamma-Fe2O3 and the doped PAn are soluble in common organic solvents, and casting of the homogeneous solutions gives free-standing nanocomposite films with gamma-Fe2O3 contents up to similar to 50 wt %. The morphology of the gamma-Fe2O3 nanoparticles are characterized by transmission electron microscopy, UV-vis spectroscopy, and X-ray diffractometry. The gamma-Fe2O3/PAn films prepared from chloroform/m-cresol solutions of DBSA-coated gamma-Fe2O3 and CSA-doped PAn are conductive (sigma = 82-237 S/cm) and superpapamagnetic, exhibiting no hysteresis at room temperature. The zero-field-cooled magnetization experiment reveals that the nanocomposite containing 20.8 wt % gamma-Fe2O3 has a blocking temperature (T-b) in the temperature region of 63-83 K.

In-situ microscopic Fourier transform infrared spectroelectrochemistry of redox mechanism for electroactive species in polyelectrolyte

Studies for the development of the in-situ microscopic FTIR spectroelectrochemistry (MFTIRS) have been carried out in polyethylene glycol(PEG) polyelectrolyte, Redox reaction mechanisms of various electroactive substances involving inorganic salt, organic compound and inorganic polymeric particles have been studied.

Aging in EPDM used for outdoor insulation

The effect of accelerated weather aging an ethylene-propylene-diene monomer(EPDM) rubber used for outdoor insulation was studied by surface roughness measurement and X-ray photoelectron spectroscopy(xps). The surface roughness of EPDM rubber changed with aging time. The surface oxygen and aluminum content were found to increase and that of carbon, silicon and nitrogen to decrease with time. The detailed XPS analysis indicated that the concentration of carbon in C-C decreased and that of highly oxidized carbons in C-O, C=O and O=C-O increased with time, which was due to the oxidation of EPDM rubber polymer. The appearance of O=C-O on the surface of EPDM rubber was a signal that EPDM rubber became aged. The aging speed decreased with time. The aging mechanism is discussed also.

In-situ microscopic FTIR spectroelectrochemical study of the reduction of K3Fe(CN)(6) in polymer electrolyte

Cyclic voltammetry and in-situ microscopic FTIR spectroelectrochemistry were used for the electrochemical and vibrational characterizations of the reduction process of K3Fe (CN)(6) in polyethylene glycol(PEG) with LiClO4 as supporting electrolyte at a Pt microelectrode. The rate of electron transfer is a function of the concentration of the supporting electrolyte. The redox potentials and cyclic voltammetric currents vary with Li/O molar ratio. The bl-situ spectroelectrochemistry shows that the infrared spectra are influenced by the concentration of LiClO4. The bridging cyanide groups with a structure Fe-I-C drop N ... Fe-I-C drop N are formed during the reduction process of K3Fe (CN)(6). There may be an activated complex between the Lif cation and the complex anion.

Study on a comb-like polymer electrolyte based on the backbone of ethylene-maleic anhydride copolymer

A comb-like polymer host(CBPE) as polymer electrolyte was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with ethylene-maleic anhydride copolymer(EMAC) and endcapping the residual carboxylic acid with methanol. The synthetic process was followed by IR and the amorphous product characterized by IR and elemental analysis. There were two peaks in the plot of the ionic conductivity against Li salt concentration. The plot of log sigma vs. 1/(T - T-0) may exhibit dual VTF behavior when using the glass transition temperature of PEO of side chain as T-0. The comb-like polymer is a white rubbery solid which dissolves in acetone. (C) 1998 Elsevier Science B.V. All rights reserved.

A study on the diffusion of quinhydrone in polymer electrolyte

The diffusion coefficients (D) of quinhydrone were estimated in polymer electrolytes by using non-steady-state chronoamperometry and steady-state current voltammetry. The D values have been estimated in polyethylene glycol (PEG) containing different concentrations, and cations of supporting electrolytes, and in different solvents over a range of temperatures. The dependencies of electroactive probe diffusion coefficients on temperature, supporting electrolyte concentration and polymer chain length are discussed. The results show that D increases with increasing temperature and decreasing concentration of supporting electrolyte. The diffusion coefficient depends strongly on the length of polymer chain and decreases sharply with increasing polymer chain length. The contribution of electron self-exchange has been explored and it seems to be negligible here. (C) 1998 Elsevier Science S.A.

Polymerization of ethylene by zirconocene-B(C6F5)(3) catalysts with aluminum compounds

Ethylene polymerization by zirconocene-B(C6F5)(3) catalysts with various aluminum compounds has been investigated. It is found that the catalytic activity depended on zirconocenes used, and especially on the type of aluminum compounds. For Et(H(4)Ind)(2)ZrCl2 (H(4)Ind : tetrahydroindenyl), the activity decreases in the following order: Me3Al > i-Bu3Al > Et3Al much greater than Et2AlCl. While for Cp2ZrCl2(Cp : cyclopentadienyl), it varies as follows: i-Bu3Al > Me3Al much greater than Et3Al. Furthermore, the activity is significantly affected by the addition mode of the catalytic components, which may imply that the formation of active centers is associated with an existing concentration of catalytic components. Results of thermal behavior of polyethylene (PE) studied by differential scanning calorimetry(DSC) show that crystallinity of the polymer prepared with Et3Al is higher than that with Me3Al or i-Bu3Al. It is also found that the number-average molecular weight ((M) over bar) of the polymers prepared with Me3Al or i-Bu3Al is much higher than that with Et3Al. H-1-NMR studies substantiate that i-Bu3Al is a more efficient alkylation agent of Cp2ZrCl2 in comparison with Me3Al. (C) 1997 John Wiley & Sons, Inc.

Dynamic mechanical properties of interpenetrating polymer networks based on polyacrylates and epoxy

Interpenetrating polymer networks (IPNs) based on polyacrylate (poly(polyethylene glycol diacrylate), PEGDA) and epoxy(diglycidyl ether of bisphenol A, DGEBA) were prepared simultaneously Dynamic mechanical properties of the SINs (simultaneous interpenetrating networks) with various compositions were studied. Enhanced mechanical properties were found in this case. From the point of view of pre-swollen networks, all of the PEGDA/DGEBA IPNs were composed of the individual pre-swollen networks. A micro-phase segregation system was produced in the SIN. Glass transition temperatures shifted inward, which was attributed to molecular packing effects or mutual-entanglements of molecular segments among the individual pre-swollen networks. In accordance with the additivity of properties, namely the parallel model, the entanglement density between the two polymer networks reached its maximum at 50/50 PEGDA/DGEBA IPN.

Studies on the two class glass transition and the typical VTF behaviour of an amorphous comb polymer electrolyte

A comb polymer (CP350) with oligo-oxyethylene side chains of the type -(CH2CH2O)(7)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly(ethylene glycol) methyl ether. The polymer can dissolve LiNO3 salt to form homogeneous amorphous polymer electrolyte. This electrolyte system was first found to have two class glass transitions, and the two T(g)s were observed to increase with increasing salt content. The ionic conduction was measured by using the complex impedance method, and conductivities were investigated as functions of temperature and salt concentration. At 25 degrees C, the ionic conductivity maximum of this system can get to 3.72 X 10(-5) S/cm at the [Li]/ [EO] ratio of 0.057. The appearance of the conductivity maximum has been interpreted as being due to the effect of T-g and the so called physical crosslinks. The temperature dependence of the ionic conductivity displaying non-Arrhenius behaviour can be analyzed using the Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model.

A study of cokes used as anodic materials in lithium ion rechargeable batteries

A variety of cokes pretreated at different temperatures are used as anodic materials and their electrochemical characteristics are examined by cyclic voltammetry. It is found that for some cokes such as petroleum coke (preheated at 1300 degrees C), pitch coke (1300 degrees C), needle coke (1900 degrees C), metallurgical coke (1900 degrees C), high capacity and cyclic efficiency are achieved. Needle coke (1900 degrees C) and metallurgical coke (1900 degrees C) in particular give a capacity of over 200 mAh/g and a cyclic efficiency of nearly 100%, whereas poor performance is exhibited by those pretreated at higher or lower temperatures, e.g., petroleum cokes (500 degrees C, 2800 degrees C), pitch coke (500 degrees C) and needle coke (2800 degrees C). The cyclic voltammograms show two electrochemical processes, one at about 0.1 V vs. Li+/Li which is electrochemically reversible, and may be attributed to the intercalation/deintercalation of lithium ions while the other, at about 0.6 V vs. Li+/Li, is electrochemically irreversible and may be assigned to the decomposition of the electrolyte solvent, which leads to formation of the passive film on the anode surface. The experimental results strongly suggest that the pretreatment temperature of cokes and of the solvent are determining factors for the growth, structure and properties of the passive film.

Lithium ion conducting polymer electrolytes based on alternating maleic anhydride copolymer with oligo-oxyethylene side chains

A comb polymer with oligo-oxyethylene side chains of the type -(CH2CB2O)(12)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly (ethylene glycol) methyl ether. The polymer can dissolve LiClO4 salt to form homogeneous amorphous polymer electrolyte. The ac ion conduction was measured using the complex impedance method, and conductivities were investigated as functions of temperatures and salt concentration. The complexes were first found to have two classes of glass transition which increase with increasing salt content, The optimum conductivity attained at 25 degrees C is in the order of 5.50 x 10(-6)Scm(-1). IR spectroscopy was used to study the cation-polymer interaction.