Effect of lignin particles as a nucleating agent on crystallization of poly(3‐hydroxybutyrate)

The effect of lignin fine powder, as a new kind of nucleating agent, on the crystallization process of poly(3‐hydroxybutyrate) (PHB) was studied. The kinetics of both isothermal and nonisothermal crystallization processes from the melt for both pure PHB and PHB/lignin blend was studied by means of differential scanning calorimetry. Lignin shortened the crystallization half‐time t_1/2 for isothermal crystallization. The activation energy ΔE for PHB/lignin and pure PHB in the isothermal crystallization process was ?237.40 and ?131.22 kJ/mol, respectively, clearly indicating that the crystallization of the PHB/lignin blend was more favorable than that of pure PHB from a thermodynamic perspective. At the same time, according to polarized optical microscopy, the rate of spherulitic growth from the melt increased with the addition of lignin, which is ascribed to the reduction of surface fold energy σ_e, that is, σ_e is 59.2 × 10^?3 and 41.6 × 10^?3 J m^?2 for pure PHB and PHB/lignin, respectively. Polarized optical microscopy also showed that the spherulites found in PHB with lignin were smaller in size and greater in number than those found in pure PHB. The wide‐angle X‐ray diffraction indicated that an addition of lignin caused no change in the crystal structure and degree of crystallinity. These results indicated that lignin is a good nucleating agent for the crystallization of PHB. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2466–2474, 2004     

Synthesis and characterization of polyaniline/NiO nanocomposite

Spherical nickel oxide (NiO) nanoparticles were prepared by using nickel chloride as precursor in the ethylene glycol as solvent and urea as precipitant. The X‐ray diffraction study showed that NiO has single‐phase cubic structure with average crystallite size of 35 nm. The prepared NiO nanoparticles were incorporated into polyaniline (PANI) matrix during in situ chemical oxidative polymerization of aniline with different molar ratios of aniline: NiO (12 : 1, 6 : 1, and 3 : 1) at 5°C using (NH₄)₂S₂O₈ as oxidant in aqueous solution of sodium dodecylbenzene sulfonic acid, as surfactant and dopant under N₂ atmosphere. The synthesized composites have been characterized by means of X‐ray diffraction (XRD), thermogravimetric analysis, Fourier transform infrared (FTIR), scanning electron microscopy, TEM, and vibrating sample magnetometer for its structural, thermal, morphological, and magnetic investigation. The XRD and FTIR studies show that the NiO particles are in the composite. The room temperature conductivities of the synthesized PANI, PANI/NiO (12 : 1), (6 : 1), and (3 : 1) composites were found to be 3.26 × 10^?4, 1.88 × 10^?4, 1.5 × 10^?4, and 4.61 × 10^?4 S/cm, respectively. The coercivity (H_c) and remnant magnetization (M_r) of NiO, PANI/NiO NCs (12 : 1), (6 : 1), and (3 : 1) at 5 K was found to be 8.22 × 10^?2, 6.31 × 10^?2, 6.42 × 10^?2, 6.27 × 10^?2 T, and 6.64 × 10^?3, 1.83 × 10^?4, 3.07 × 10^?4, and 3.98 × 10^?4 emu/g, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Graft copolymerization of acrylamide onto cellulose in presence of comonomer using ceric ammonium nitrate as initiator

The graft copolymerization of acrylamide (AAm) and ethylmethacrylate (EMA) monomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as initiator in presence of nitric acid at (25 ± 1)°C and varying feed molarity from 7.5 × 10^?2 mol dm^?3 to 60.0 × 10^?2 mol dm^?3 at fixed feed composition (f_AAm = 0.6). The graft yield (%G_Y) has shown a linear increasing trend upto a feed molarity of 37.5 × 10^?2 mol dm^?3. The composition of grafted copolymer chains was found to be constant (F_AAm = 0.56) during feed molarity variation but shown variations with feed composition (f_AAm) and reaction temperature. The grafting parameters have shown increasing trends up to 7.5 × 10^?3 mol dm^?3 concentration of ceric (IV) ions and decreased on further increasing the concentration of ceric (IV) ions beyond 7.5 × 10^?3 mol dm^?3. The IR and elemental analysis data were used to determine the composition of grafted chains (F_AAm) and reactivity ratio of acrylamide (r₁) and ethylmethacrylate (r₂) comonomers. The reactivity ratio for acrylamide (r₁) and ethylmethacrylate (r₂) has been found to be 0.7 and 1.0 respectively, which suggested for an alternate arrangement of average sequence length of acrylamide (mM?₁) and ethylmethacrylate (mM?₂) in grafted chains. The rate of graft copolymerization of comonomers onto cellulose was found to be proportional to square concentration of comonomers and square root to the concentration of ceric (IV) ions. The energy of activation (ΔEa) of graft copolymerization was found to be 9.57 kJ mol^?1 within the temperature range of 20–50°C. On the basis of experimental findings, suitable reaction steps have been proposed for graft copolymerization of selected comonomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2546–2558, 2006     

Ceric ion‐induced graft copolymerization of acrylamide on cationic guar gum at low temperature

The solution polymerization of acrylamide (AM) on cationic guar gum (CGG) under nitrogen atmosphere using ceric ammonium sulfate (CAS) as the initiator has been realized. The effects of monomer concentration and reaction temperature on grafting conversion, grafting ratio, and grafting efficiency (GE) have been studied. The optimal conditions such as 1.3 mol of AM monomer and 2.2 × 10^?4 mol of CAS have been adopted to produce grafted copolymer (CGG1‐g‐PAM) of high GE of more than 95% at 10°C. The rates of polymerization (R_p) and rates of graft copolymerization (R_g) are enhanced with increase in temperature (<35°C).The R_p is enhanced from 0.43 × 10^?4 mol L^?1 s^?1 for GG‐g‐PAM to 2.53 × 10^?4 mol L^?1 s^?1 for CGG1‐g‐PAM (CGG1, degree of substitute (DS) = 0.007), and R_g from 0.42 × 10^?4 to 2.00 × 10^?4 mol L^?1 s^?1 at 10°C. The apparent activation energy is decreased from 32.27 kJ mol^?1 for GG‐g‐PAM to 8.09 kJ mol^?1 for CGG1‐g‐PAM, which indicates CGG has higher reactivity than unmodified GG ranging from 10 to 50°C. Increase of DS of CGG will lead to slow improvement of the polymerization rates and a hypothetical mechanism is put forward. The grafted copolymer has been characterized by infrared spectroscopy, thermal analysis, and scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3715–3722, 2007     

Study on preparation and properties of PVA‐SA‐PHB‐AC composite carrier for microorganism immobilization

Polyvinyl alcohol(PVA) bead crosslinked with boric acid has been widely utilized as a microorganism immobilization carrier. However, it has some disadvantages such as drastic cell viability loss, small adsorption capacity and mass transfer limitation. To improve upon these drawbacks, a new method to prepare PVA composite pieces with the addition of activated carbon (AC) and poly‐3‐hydroxybutyrate(PHB) was explored through a combination of freezing/thawing and the boric acid method and by using Tween‐80 to improve the mass transfer performance of hydrophobic organics. m‐Cresol and pyrene were used as representative compounds with benzene ring structures to model hydrophilic and hydrophobic organics in order to test the performance of PVA pieces. The results showed that, compared with the boric acid method alone, a combination of freezing/thawing and the boric acid method led to a decrease in total organic carbon(TOC) loss from 0.315 g g^?1 to 0.033 g g^?1 and increased the oxygen uptake rate(OUR) of microorganisms from 0.03 mg L^?1·min^?1 to 0.22 mg L^?1 min^?1. The m‐cresol equilibrium adsorption amount of the PVA‐SA(sodium alginate)‐PHB‐AC piece was 2.80 times that of the PVA‐SA piece. The diffusion coefficient of pyrene in the PVA‐SA‐PHB‐AC piece increased from 0.53×10^?9 m² min^?1 to 2.30×10^?9 m² min^?1 with increasing concentrations of Tween‐80 from 1000 mg L^?1 to 5000 mg L^?1. The PVA‐SA‐PHB‐AC composite carrier demonstrated great scope for immobilizing microorganisms for practical wastewater bio‐treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39837.     

Ceric(IV) ion‐induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (F_AAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10^?2 to 60.0 × 10^?2 mol L^?1, whereas the composition of the grafted chains (F_AAm) was found to be dependent on feed composition (f_AAm) and reaction temperature. The effects of ceric(IV ) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10^?3 mol L^?1 concentration of CAN at a feed molarity of 30.0 × 10^?2 mol L^?1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10^?3 mol L^?1) at a constant concentration of nitric acid (5.0 × 10^?2 mol L^?1). The composition of the grafted chains (F_AAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r₁) and ethyl acrylate (r₂) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r₁ = 0.54 and r₂ = 1.10, respectively, and hence the sequence lengths of acrylamide (m?M₁) and ethyl acrylate (m?M₂) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r₁ × r₂) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ‘squares’ of the concentrations of the comonomers and on the ‘square root’ of the concentration of ceric ammonium nitrate. The energy of activation (ΔE_a) of graft copolymerzation was found to be 5.57 kJ mol^?1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry     

Effect of diantimony trioxide on direct esterification between terephthalic acid and ethylene glycol

Experiments at various Sb₂O₃ concentrations were made in a pilot plant and the effect of Sb₂O₃ on continuous esterification between terephthalic acid (TPA) and ethylene glycol (EG) was obtained. Reaction rate constants of the previously reported reaction scheme were determined to fit with the experimental data obtained. It was found that the effect of Sb₂O₃ on reaction rate constant (k_i) can be expressed as follows.

• k₁ = (3.75 × 10^?4Sb + 1.0) × 1.5657 × 10⁹exp(?19,640/RT)
• k₂ = (4.75 × 10^?4Sb + 1.0) × 1.5515 × 10⁸exp(?18,140/RT)
• k₃ = (6.25 × 10^?4Sb + 1.0) × 3.5165 × 10⁹exp(?22,310/RT)
• k₄ = (4.50 × 10^?4Sb + 1.0) × 6.7640 × 10⁷exp(?18,380/RT)
• k₅ = (3.50 × 10^?4Sb + 1.0) × 7.7069 × exp(?2810/RT)
• k₆ = (1.75 × 10^?4Sb + 1.0) × 6.2595 × 10⁶exp(?14.960/RT)
• k₇ = (3.75 × 10^?4Sb + 1.0) × 2.0583 × 10¹⁵exp(?42,520/RT)

Simulation of esterification with these reaction rate constants at various Sb₂O₃ concentrations was made and the following results were obtained.

• 1 Sb₂O₃ accelerates the esterification reaction between TPA and EG.
• 2 Sb₂O₃ accelerates the main reaction and its effects on side reactions are minor. The higher the addition rate of Sb₂O₃, the lower the carboxyl end-group concentration (AV) and diethylene glycol content (DEG).
• 3 The comparison between simulation with potassium titanium oxyoxalate (PTO) in the previous report and with Sb₂O₃ in the present report shows that the acceleration of polycondensation reaction by Sb₂O₃ is higher. DEG formation rate is lower with PTO than Sb₂O₃.

     

Kinetics of leaching of tunisian phosphate ore particles in dilute phosphoric acid solutions

Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P₂O₅). When the temperature rises from 25 to 90°C, for a given particle size, the mass-transfer coefficients, k_L°, vary from 3 × 10^?3 to 8 × 10^?3 m ·s^?1. The corresponding diffusion coefficients, D, lies between 6 × 10^?7 and 27 × 10^?7 m²·s^?1. Activation energy is equal to 14 kJ·mol^?1 and values of k_L°, at 25°C, are in the range of 0.28 × 10^?3 and 4 × 10^?3 m·s^?1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction.     

Anionic difunctionalization with 1,1-bis(4-t-butyldimethylsiloxyphenyl) ethylene. Synthesis of ω,ω-bis(phenol)-functionalized polystyrene condensation macromonomers

ω,ω-Diphenolpolystyrenes (6) can be synthesized in quantitative yields by reacting poly(styryl)lithium with 1,1-bis(4-t-butyldimethylsiloxyphenyl)ethylene (1), followed by methanol termination and hydrolysis with dilute acid. The initially formed 1,1-bis(4-t-butyldimethylsiloxyphenyl)alkyllithium can be reacted with additional styrene monomer to form a polystyrene internally substituted with two in-chain phenol groups after methanol termination and acid hydrolysis. The diphenol-substituted polystyrene condensation macromonomers have been characterized by end-group titration, size exclusion chromatography, thin-layer chromatography, and ultraviolet-visible, ¹H and ¹³C NMR spectroscopy. Chain-extension reactions of 6 (M_n = 2.6 × 10³g mol^?1) with bis(trichloromethyl)carbonate produced the corresponding comb-type, branched polymer with estimated Mⁿ(SEC, polystyrene standards) = 1.2 × 10⁴g mol^?1 and no detectable residual condensation macromonomer. The second order rate constants for the addition reaction of excess poly(styryl)lithium with 1 and with 1-(4-t-butyldimethylsiloxy-phenyl)-1-phenylethylene (3) have been estimated to be 1.7 × 10^?3M^?1/2S^?1 and 3.2 × 10^?3M^?1/2S^?1 respectively. A sigma value (σ) of ?0.46 has been estimated for the t-butyldimethylsiloxy substituent.     

Laser light-scattering studies of soluble high performance fluorine-containing polyimides

Two sets of soluble high performance polyimides synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′-(trifluoromethyl)-4,4′-diaminobiphenyl diamine (PFMB), and from 2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyl-tetracarboxylic dianhydride (HFBPDA) and 2,2′-(trifluoromethyl)-4,4′-diaminobiphenyl diamine (PFMB) have been investigated by static and dynamic laser light scattering (LLS) in tetrahydrofuran (THF) at 30°C. The calibrations, for 6FDA-PFMB: <R_g> (nm) = 3.87 × 10^?2 <M_w> ^0.568, <R_h> (nm) = 2.38 × 10^?2 <M_w>^0.560 and <D> (cm²/s) = 2.13 × 10^?4 <M_w>^?0.560; for HFBPDA-PFMB: <R_g> (nm) = 2.24 × 10^?2 <M_w>^0.626, <R_h> (nm) = 1.27 × 10^?2 <M_w>^0.621 and <D> (cm²/s) = 3.99 × 10^?4 <M_w>^?0.621, have been established, where <M₂>, <R_g>, <R_h> and <D> are the weight-average molar mass, the root mean square z-average radius of gyration, the z-average hydrodynamic radius and the z-average translational diffusion coefficient, respectively. A combination of <M_w> and the translational diffusion coefficient distribution G(D) leads to the calibrations of D (cm²/s) = 2.41 × 10^?4M^?0.564 and D (cm²/s) = 6.16 × 10^?4M^?0.656 for 6FDA-PFMB and HFBPDA-PFMB, respectively, where D and M correspond to monodisperse species. With these calibrations, we can convert a translational diffusion coefficient distribution G(D) into a corresponding molar mass distribution f_w(M). On the basis of the Kratky-Porod wormlike chain model, the persistence lengths (q) were found to be ? 3.3 nm and ? 4.5 nm, respectively, for 6FDA-PFMB and HFBPDA-PFMB, which indicates that both polyimide chains have an extended conformation. In addition, <R_g> / <R_h> ? (1.7-1.9) shows that they are in coil conformation. Therefore, we conclude that both polyimides have an extended coil conformation.     

Simple dilatometer for polymer density and thermal expansivity measurements

A dilatometer is described to study the temperature dependence of density (ρ) of solid and semiliquid polymers and the following linear relations have been established. Atactic poly(vinylisobutyl ether) (25–90°C): ρ = 0.9166 ? 7.15 × 10^?4 × T. Isotactic poly(vinylisobutyl ether) (25–70°C): ρ = 0.9184 ? 7.13 × 10^?4 × T. Poly(n-butyl methacrylate) (90–150°C): ρ = 1.0622 ? 8.41 × 10^?4 × T. Poly(dimethyl siloxane) (30–51°C, using Lipkins pycnometer): ρ = 0.9846 ? 8.81 × 10^?4 × T; where ρ is in g.cm^?3, temperature T is in Celsius, and the linearity correlation coefficient r is better than 0.9998. Their volume–temperature plots are also linear. As the plots of polyn-butyl methacrylate curved slightly near its glass transition (20°C), the quadratic equation ρ = 1.0402 ? 4.79 × 10^?4 × T ? 1.46 × 10^?6 × T² (standard deviation = 1.57 × 10^?3) has been suggested for the entire range of 30–150°C scrutinized in this study. The data have been utilized to derive thermal expansivity and some equation-of-state parameters of the polymers at the reference temperature (ca. 20°C).     

Kinetic and Mass Transfer Model for Separation of Protein Using Ceramic Monoliths as a Stationary Phase

Rigid adsorbents used as matrix skeleton have advantages over soft gel media for downstream processing of proteins. The adsorption of bovine serum albumin (BSA) has been investigated on a rigid ceramic monolith coated with cross-linked microporous agarose (D5). The physical properties of the adsorbent and the adsorption equilibria, adsorption kinetics, and mass transfer behavior have been studied for five different flow rates, with a pH value ranging from pH 4.5 to 7.0. The optimal working flow rate was 14.0?cm³/min, and using this flow rate, increasing the pH does not generate a significant improvement in the adsorption capacity. The rates of BSA adsorption have been measured and it was possible to describe a theoretical model, in which the mass transfer involves a dispersion coefficient (k_disp), which describes the mass transfer in the adsorbent surface, from the volume of the protein solution to the agarose surface. This parameter presents an exponential tendency by increasing the flow rate from 2.37?×?10^?6 to 87.40?×?10^?6?cm/s for n?=?1. Values obtained for the adsorption kinetic constant (k_ads) followed the trend of the mass transfer parameter, increasing with the flow rate from 1.94?×?10⁴ to 117.39?×?10⁴?cm²/mol?s. The theoretical model predicts the protein concentration in equilibrium for successive column reuses and it can be readily used to determine the optimal reuse of column. Likewise, for a maximum flow rate of 14?cm³/min, pressure drop was 0.04?MPa, being an advantage in front of packed columns that have higher pressure drop.     

A measure of effective crosslinks in formaldehyde-modified cotton celluloses

Sol-gel fractions have been measured for cotton celluloses crosslinked with formaldehyde under widely different conditions of reaction and have been employed for estimation of the efficiency of crosslinking in the various processes. Most efficient utilization of formaldehyde for insolubilization of molecular chains is indicated for an aqueous process (form W′) and least efficient utilization is indicated for a nonaqueous process (form D′), the difference in efficiency being approximately a factor of 40. Interpretation of sol-gel data has been made relative to a model assuming random reaction of crosslinking agent throughout the cotton cellulose and by relationships developed by Charlesby and Pinner and by Shultz. This leads to estimates of relative numbers (moles) of effective chain elements per gram, v_e (i.e., twice the number of effective crosslinks), which decrease in the following sequence for cottons at the 0.20% level of formaldehyde (i.e., 6.7 × 10^?5 mole/g.): aqueous process, higher formaldehyde concentration (W′, v_e = 4.8 × 10^?5), vapor process (V, v_e = 1.75 × 10^?5), bake-cure process (C, v_e = 1.37 × 10^?5), aqueous process, lower formaldehyde concentration (W, v_e = 0.95 × 10^?5), nonaqueous process (D, v_e = 0.03 × 10^?5).     

Synthesis and Evaluation of Novel Amido-Amine Cationic Gemini Surfactants Containing Flexible and Rigid Spacers

New amido‐amine‐based cationic gemini surfactants with flexible and rigid spacers and different hydrophobic tails were synthesized and characterized. These gemini surfactants were prepared by a modified procedure through amidation of long chain carboxylic acids using 3‐(dimethylamino)‐1‐propylamine followed by treatment with halohydrocarbons. The effect of the trans and cis conformation of the spacer double bond was investigated by means of critical micelle concentration, surface tension reduction, and thermal stability. The short‐term thermal stability of the gemini surfactants was assessed using thermogravimetric analysis (TGA) and the long‐term thermal stability was examined by a unique approach based on structure characterization techniques including NMR (¹H and ¹³C) and FTIR analysis. TGA results demonstrated excellent short‐term thermal stability since no structure degradation was observed up to 200 °C. Structural characterization revealed impressive long‐term thermal stability of the gemini surfactants with no structure decomposition after exposing them to 90 °C for 10 days. The critical micelle concentration of gemini surfactants was found to be in the range of 0.77 × 10^?4–3.61 × 10^?4 mol L^?1 and corresponding surface tension (γ_CMC) ranged from 30.34 to 38.12 mN m^?1. The surfactant with the trans conformation of spacer double bond showed better surface properties compared to the surfactant with the cis conformation of spacer double bond. Similarly, increasing surfactant tail length and spacer length resulted in decreasing CMC values. Moreover, bromide counterion showed improved surface properties compared to chloride counterion.     

Ionic conductivity of unsaturated polyester resin networks containing LiCIO4

Poly(ethylene oxide) (PEO) 400-maleate-isophthalate resins have been prepared and LiCIO₄ dissolved in the resins before crosslinking with 30% of styrene, vinylpyrrolidone or vinylpyridine. The DC conductivities of the resins were measured and found to increase in the order vinylpyridine 〈vinylpyrrolidone〉 styrene for the same [EO]/[Li⁺] ratio ( = 50). For the styrene system σ = 3 × 10^?6Scm^?1 at ambient temperatures and for the vinylpyridine system σ = 1 × 10^?7 Scm^?1. The T_gs of the system were also measured using dynamic mechanical thermal analysis and were found to be very close (257-260 K). The above sequence was therefore attributed to stronger site-binding of lithium ions at the more polar comonomers. An interpenetrating network (IPN) consisting of the styrene-polyester and incorporating 40% PEO 400 was also prepared with[EO]/[Li⁺]ratios of 20 and 50. These gave ambient temperature conductivities of 1 × 10^?5 and 3 × 10^?5 Scm^?1, respectively.     

Dynamic adsorption behaviors between Cu2+ ion and water‐insoluble amphoteric starch in aqueous solutions

Dynamic adsorption behavior between Cu²⁺ ion and water‐insoluble amphoteric starch was investigated. The sorption process occurs in two stages: external mass transport occurs in the early stage and intraparticle diffusion occurs in the long‐term stage. The diffusion rate of Cu²⁺ ion in both stages is concentration dependent. In the external mass‐transport process, the diffusion coefficient (D₁) increases with increasing initial concentration in the low‐ (1 × 10^?3‐4 × 10^?3M) and high‐concentration regions (6 × 10^?3‐10 × 10^?3M). The values of adsorption activation energy (k_d1) in the low‐ and high‐concentration regions are 15.46–24.67 and ?1.80 to ?11.57 kJ/mol, respectively. In the intraparticle diffusion process, the diffusion coefficient (D₂) increases with increasing initial concentration in the low‐concentration region (1 × 10^?3‐2 × 10^?3M) and decreases with increasing initial concentration in the high‐concentration region (4 × 10^?3‐10 × 10^?3M). The k_d2 values in the low‐ and high‐concentration regions are 9.96–15.30 and ?15.53 to ?10.71 kJ/mol, respectively. These results indicate that the diffusion process is endothermic in the low‐concentration region and is exothermic in the high‐concentration region for both stages. The external mass‐transport process is more concentration dependent than the intraparticle diffusion process in the high‐concentration region, and the dependence of concentration for both processes is about equal in the low‐concentration region. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2849–2855, 2001     

Dielectric relaxation analysis of biopolymer poly(3‐hydroxybutyrate)

Poly(3‐hydroxybutyrate), PHB, is a widely distributed carbon storage polymer among prokaryotes including Rhizobium. Capacities of Rhizobium etli R13 to produce the bioplastic during growth on media with different carbon sources appeared to be specific carbon‐source. In fed batch fermentation, R. etli R13 resulted in cell dry weight 6.2 g/L and PHB 51.4%. Gas chromatography‐mass spectrometry and gel permeation chromatography analysis revealed that PHB produced from R. etli R13 was solely composed of 3‐hydroxybutyric acid and the molecular mass of the purified PHB was 3.4 × 10⁵ Da with polydispersity 1.47. Dielectric relaxation of PHB has been studied in the temperature and frequency ranges 300–440 K and 10 kHz–4 MHz, respectively. A clear dielectric α and ρ‐relaxation processes are observed in these studied ranges of temperature and frequency. The first process is due to the dipole relaxation in the crystalline phase of PHB. The second one is due to the space‐charge formation or Maxwell‐Wagner‐polarization. The α‐relaxation process has been investigated by semiempirical Havriliak‐Negami relaxation function. The activation energy (E_a) and the relaxation time (τ₀) are calculated using the Arrhenius equation. The dielectric relaxation strength (Δε) is strongly temperature dependent. The calculated values of E_a for ac conductivity, ln(σ), of PHB provide information about the presence of electronic conduction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Interpretation of intrinsic viscosity/temperature data for solutions of poly(phenyl acrylate) and poly(ethylene oxide)

Measured intrinsic viscosities ([η]) at several temperatures (T) within the interval 280–350 K have been found to increase with T for solutions of poly(phenyl acrylate) (PPA) in ethyl lactate. A decrease of [η] with T was observed for aqueous solutions of poly(ethylene oxide) (PEO) at several temperatures within the range 276–358 K. The results have been treated on the basis of eight excluded volume theories, among which the best consistency was afforded by those of Kurata-Stockmayer-Roig, Fixman, and Stockmayer (Padé). These yielded values of ?3.4 × 10^?3 to ?4.7 × 10^?3 deg^?1 and ?0.9 × 10^?3 to ?2.4 × 10^?3 deg^?1 for the temperatur coefficient of the unperturbed dimensions of PPA and PEO, respectively. The derived θ-temperatures were 287 K as the upper critical solution temperature for PPA in ethyl lactate and 365–382 K as the lower critical solution temperature for aqueous PEO.     

Capture of submicrometer particles in a pressurized electrostatic precipitator

This study investigated the influence of gas pressure on the submicrometer particle capture performance of an electrostatic precipitator (ESP). Current-voltage characteristics and particle capture performance of the ESP were studied in air and in simulated flue gas (SFG) under 1, 2, and 3 atm. Using negative corona and air as the feed gas, the penetration of most particles of 40–400 nm in diameter decreased from 8 × 10^?4 ? 2 × 10^?2 to 2 × 10^?4 ? 1 × 10^?2 as pressure increased from 1 atm to 3 atm at constant current; and increased from 3 × 10^?5 ? 1 × 10^?3 to 2 × 10^?4 ? 1 × 10^?2 as pressure was elevated when the voltage was held roughly constant. Similar type of disparity under different pressures was also observed for positive corona and for SFG. Experiments set up to capture fly ash in the ESP showed that with constant current, higher pressure resulted in a higher initial charge fraction of the particles from the furnace, which could facilitate the penetration of fly ash particles. A semiempirical model was developed based on the Deutsch–Anderson equation and experimental data under 1, 2, and 3 atm to calculate the particle penetrations under high pressure. The total charge number on a particle (n') is calculated by incorporating the effects of current (I) and pressure (P) on relative weights of the diffusion charging number (n_diff) and field charging number (n_field), that is, n' = B₁(I,P)n_diff + B₂(I,P)n_field, where B₁(I,P) and B₂(I,P) are both empirical coefficients dependent on current and pressure. Experimental penetrations under 1.5 and 2.5 atm validated this model over the particle diameter range in 100–400 nm.

Copyright © 2016 American Association for Aerosol Research     

Photoelectrocatalytic humic acid degradation kinetics and effect of pH,applied potential and inorganic ions

This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV₂₅₄ removal and the degradation of color (Vis₄₀₀) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10^?1 min^?1, 8.3 × 10^?2 min^?1 and 2.49 × 10^?2 min^?1 (R² > 0.97) for UV₂₅₄ degradation and 1.7 × 10^?1 min^?1, 6.5 × 10^?2 min^?1 and 2.0 × 10^?2 min^?1 for color removal from 5 mg dm^?3, 10 mg dm^?3 and 25 mg dm^?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm^?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV₂₅₄ removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry