Vapour pressure and vapourisation enthalpy of pyridine N‐oxide

The vapour pressure of pyridine N‐oxide was measured using a boiling point method at different temperatures from 389.02 to 546.33 K and the constants of the Antoine equation for the substance were determined. The vapourisation enthalpy of pyridine N‐oxide at the normal boiling point is calculated to be 58.8 ± 1.8 kJ mol^?1. Based on Othmer's method, the standard enthalpy of vapourisation is estimated to be 66.6 ± 0.1 kJ mol^?1 by using pyridine as the reference substance. Furthermore, Watson equation is employed to verify the reliability of and the results demonstrate that the value of is acceptable. © 2011 Canadian Society for Chemical Engineering     

Polypentadecalactone prepared by lipase catalysis: crystallization kinetics and morphology

BACKGROUND: This work addresses the need to better understand the crystallization kinetics and morphology of poly (ω‐pentadecalactone) (PPDL). This polyester has promising mechanical properties and a unique structure that resembles that of polyethylene. PPDL is a member of the poly(ω‐hydroxy fatty acid) family, which can be derived from biobased feedstocks. RESULTS: PPDL (M_n = 34 000 g mol^?1 and dispersity D = M_w/M_n = 2.7) was synthesized using enzyme catalysis. Equilibrium melting enthalpy and equilibrium melting point were determined using extrapolation techniques, being 227 J g^?1 and 101 °C, respectively. In addition, the equilibrium melting point ( ) was found to be 109.3 °C by the nonlinear Hoffman‐Weeks plot. For , the lateral surface free energy (σ), fold surface free energy (σ_e) and fold work (q) are 10.4 erg cm^?2, 47.5 erg cm^?2 and 2.6 kcal mol^?1, respectively; while for , they are 25.1 erg cm^?2, 46.6 erg cm^?2 and 2.6 kcal mol^?1, respectively. The results indicated the existence of a regime I to regime II transition during crystallization at about 80 °C. Polarized optical microscopy and AFM provided further evidence for the regime I–II transition. In regime I, coarse spherulites were formed through splaying out and occasional branching of lamellae, as well as stacking of lamellae through screw dislocation. In contrast, in regime II, banded spherulites were formed through crystal twisting. CONCLUSION: Morphological changes in PPDL at spherulitic and lamellar levels in regimes I and II were confirmed by differential scanning calorimetry, POM and AFM. Copyright © 2009 Society of Chemical Industry     

Use of various processes for pilot plant treatment of wastewater from a wood‐processing factory

The wastewater from a wood‐processing factory is characterized by a high COD, chlorides and nitrogen content. Various treatment processes were applied to treat this wastewater in pilot‐scale units. By applying one‐stage denitrification–activated sludge biological treatment it was not possible to remove nitrogen. Nitrification was inhibited by wastewater compounds. By applying a second stage of a nitrification biofilter it was possible to have a high degree of nitrification. The denitrification was complete. With biological methods the reduction of COD, and ‐N and ‐N concentrations to acceptable values was not achievable. Physical–Chemical methods as H₂O₂/UV, electrolysis and ozonation were used as post‐treatment of effluents from the biological system. Radical degradation, initiated by the powerful hydroxyl radicals which are generated from H₂O₂ by UV activation, is used for wastewater post‐treatment. The combination of H₂O₂/UV was not suitable for post‐treatment of this wastewater. With electrolysis, ‐N and COD removal can be complete. The total amount of ammonia and organic nitrogen converted to nitrate nitrogen for current density of 1.15 Adm^?2 and energy consumption of 71.6 kWhm^?3 was 0.35 gdm^?3. Further biological denitrification is required for ‐N removal to permitted values. Energy consumption for the elimination of 1 kg COD was 40.4 kWh and 35.8 kWh for current densities of 0.7 Adm^?2 and 1.15 Adm^?2 respectively. The energy required to reach the limit value of COD equal to 150 mgdm^?3 for current density of 1.15 Adm^?2 was 71.6 kWhm^?3. With ozonation, the COD removal can be complete. Further biological nitrification–denitrification is required to remove ‐N and ‐N to permitted values. At pH 7.0, in order to reach the limit value of COD equal to 150 mgdm^?3, specific ozone dose was 6.0 g per g of COD removed and the total amount of ammonia and organic nitrogen converted to nitrate nitrogen was 0.25 gdm^?3. The total equivalent energy required is estimated to be 75.0 kWhm^?3. © 2001 Society of Chemical Industry     

Shear rate dependence of the viscosity of cellulose nitrate solutions in the dilute concentration regime revisited

A detailed rheological study of cellulose nitrate in ethylacetate had been carried out in the dilute concentration (c) regime, covering a degree of polymerization (DP) range between 300 < DP_η < 7000 and shear rates ($ \dot \gamma $) between 100 s^?1 < $ \dot \gamma $ < 2000 s^?1. The results show a strong dependence of the transition Newtonian to non-Newtonian behavior on the three variables $ \dot \gamma $, DP, and c, similar to that found recently on solutions of synthetic polymers. Emphasis has been put on the critical concentrations corresponding to the standard shear rate 1000 s^?1 to correspond to the standard conditions ($ \dot \gamma $ ? 1000 s^?1; 0.3 < [η] · c < 0.6; DS = 2.90 ± 0.02) proposed for the determination of the intrinsic viscosity [η] of cellulose nitrates. It is shown that solutions with concentrations adjusted according to the above given conditions still exhibit Newtonian behavior, up to the highest range of DP. It follows, therefore, that applying the standard conditions, an extrapolation to $ \dot \gamma $ = 0 as has been proposed often for the intrinsic viscosity determination of cellulose nitrate is not advisable and results in considerable error. Considering the relationship between [η] and DP, the present results indicate that the decrease of the exponent ( a ) from a = 1.0 to a = 0.76, taking place above a DP ? 1000, is not a consequence of the applied shear rate but rather of the molecular properties of the solutes themselves.     

Kinetics of ion exchange in monodisperse resin

Ion-exchange kinetics within a conventional strong base resin, Dowexl-8X®, and a resin with uniform particle size, Dowex® Monosphere® Tough Gel® TG550A®, were investigated using neutron activation analysis and radio-tracer techniques. The kinetics of ion exchange were measured in a batch and in a “shallow-bed” flow system. The experimental data were compared with the results of model computations. The diffusivities of several anions within TG550A and Dowexl-8X were deduced. It was found that at 25°C Br^-, Cl^-, OH^-, and Na⁺ diffuse within TG550A with the diffusion coefficients = 6.0 × 10^-7 cm²/s, = 1.2 × 10^-6 cm²/s, = 7.0 × 10^-8 cm²/s, and = 5 × 10^-7 cm²/s. Diffusion of anions within a conventional resin, Dowexl®, was slower: = 3.5 × 10^-7 cm²/s, = 6 × 10^-7 cm²/s, = 2.7 × 10^-8 cm²/s, and = 5 × 10^-7 cm²/s. A higher rate of ion diffusion and the bead-size uniformity may make monodisperse Dowex Monosphere Tough Gel TG550A resin attractive for analytical applications. The difference in properties between conventional and monodisperse resins is not sufficient to affect the large volume applications of resins. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1271–1283, 1997     

Evaluation of the termination mode in the radical polymerization of 2,2,2‐trifluoroethyl α‐fluoroacrylate

The mode of termination of 2,2,2‐trifluoroethyl α‐fluoroacrylate (FATRIFE) in radical polymerization was studied, and only termination by recombination occurred, which led to telechelic macromolecular structures. The radical polymerization in acetonitrile was carried out to synthesize oligomers with a low number average degree of polymerization ( )_cum (about 20), using tert‐butylcyclohexyl peroxydicarbonate (TBCPC) as initiator at 75 °C. The initial [TBCPC]₀/[FATRIFE]₀ molar ratio was monitored to evaluate its influence on the ( )_cum of α‐fluoroacrylic oligomers. The ¹H NMR analysis of the polymers showed that the ( )_cum values obtained were higher than 40, in spite of a high C₀ value. To explain these results, the mode of termination was evaluated using the following kinetic law: . The development of kinetic relationships allowed us to calculate the ratio k_prt/k_i·k_p as about 17–30 mol s l^?1, and to confirm that primary radical termination (PRT) was in competition with bimolecular macromolecular termination (BMT). © 2002 Society of Chemical Industry     

Kinetics of methyl methacrylate grafting polymerization onto flaky aluminum powder

With ammonium persulfate (APS) as the initiator, the kinetics of methyl methacrylate (MMA) grafting polymerization onto flaky aluminum powder (Al) was studied. It was found that the experimental apparent grafting polymerization rate, R_g = KC × C × C, was basically consistent with the theoretical result based on the theory of stable polymerization and equivalent activity, R_g = KC × C × C_MMA. The activation energy of grafting, homogenous, and total polymerization rate was calculated as 65.1, 35.4, and 37.5 kJ mol^?1, respectively. It could be validated that the relationship among these activation energies accorded with the theoretical result of parallel reactions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface energy mapping of Kevlar® fibers by inverse gas chromatography

The surface energy characteristics of three Kevlar® fibers have been systematically studied using two inverse gas chromatography (IGC) techniques, i.e., at an infinite probe dilution and at a finite probe concentration, with the latter allowing a unique mapping of the surface energy levels, which complements greatly the more traditional characterization of the highest energy sites. The standard thermodynamic parameters, such as the free energy −Δ , and the adsorption enthalpy and entropy (Δ and −Δ ), as well as the dispersive and the specific component ( and ΔG^sp/I^sp) of the fiber surface energy, were determined from the retention behavior at zero coverage of selected molecules of various polarity. The values are between 49–58 mJ m⁻² for the three fibers at 50°C. The polar components, ΔG^sp or I^sp, calculated by three different methods, reveal the polar feature of the fiber surface. It is interesting to note that the adsorption enthalpies Δ for the short chain alkane probes are nearly the same as their liquefaction energies. Using the second IGC approach, i.e., at finite concentration, the isotherms for the adsorption of n-octane and n-hexylamine on the three selected Kevlar® fibers were constructed by the one-peak method. These are shown to be instrumental to establish the corresponding energy distribution functions. The results may indicate that, unlike the alkane probes, the polar molecules interact strongly with the Kevlar® fiber surfaces, which appear, in this case, energetically heterogeneous. The resulting energy distribution mapping opens new avenues towards the surface characterization of the global surface without the restriction of the averaging imposed by other bulk analysis techniques. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 487–500, 1998     

Limitations of the Zero‐Length Column Technique to Measure Diffusional Time Constants in Microporous Adsorbents

The zero‐length column (ZLC) technique has been developed to measure the intracrystalline diffusivity of strongly adsorbed species in large zeolite crystals above 50 μm in the Henry's law range of sorption equilibrium. The ZLC is a macroscopic technique, and there is a need of large crystallites or pellets to measure the intracrystalline diffusivity D_c of fast diffusion species or the macropore diffusivity D_P of weakly adsorbed species, respectively. Another limitation is that ZLC desorption curves produce similar concentration profiles (linear isotherms) in bidisperse adsorbents (pellets) under macropore or micropore diffusion control. Moreover, the forms of the response curves are very similar in both diffusion‐ and nonlinear equilibrium‐controlled processes, leading to some misinterpretations of ZLC experiments. In this work, two criteria are developed showing that, in order to macroscopically measure the micropore diffusion time constant  or the macropore diffusion time constant , the time of the ZLC experiments t should be higher than 7.0 × 10^?2 or 7.0 × 10^?2 , respectively. The interpretation of the ZLC response curve data is also checked in two completely different regimes, showing that a single ZLC response curve is not enough to conclude if a system is under a kinetic or an equilibrium regime.     

The Use of Inverse Gas Chromatography (IGC) to Determine the Surface Energy of RDX

The surface properties of RDX play an important role in enhancing mechanics performances of the propellants and explosives. In this work, thereby, inverse gas chromatography (IGC) using various probe liquids as the medium was used to determine the surface energy components of RDX containing both dispersive and polar components, which were acquired respectively from neutral probe liquids (such as n‐hexane, n‐heptane, n‐octane) and polar probe liquids (such as chloroform, benzene, methanol). The results show that RDX located in different column temperatures has difference in the surface energy and possesses more surface energy when there is high temperature. The calculated formula of the total surface energy with temperature is: , and it is also found that dispersive, polar, electron acceptor, and electron donor components of RDX are , , , and , respectively. These results demonstrate that the dispersive component is the primary part of the total surface energy, and RDX has an acid performance.     

The kinetics of reduction of selenious(IV) ions in hydrochloric acid with sulphur dioxide

The reduction of selenious ions to its elemental state has been found to be a function of selenious ion concentration, solution acidity, gas flow rate and temperature. The rate equation can be written as: where α = ?1/2, β = 1, γ = 0.9, E = ?53 411 kJ kg^?1mol^?1, R = 8314 kJ kg^?1 mol^?1 K^?1 and k₀ = 194. The reaction temperature starts to decrease when the conversion rate reaches a maximum. This observation can be used to determine the end of the reaction.     

Melting behavior of poly(trimethylene terephthalate)

In this study, the melting behavior of isothermally crystallized polytri‐ methylene terephthalate (PTT) was investigated. Multiple melting behaviors in DSC heating trace were found because two populations of lamellar stacks were formed during primary crystallization and the recrystallization at heating process, respectively. This fact could be also confirmed from the result of optical microscopy observation. The Hoffman–Weeks equation was applied to obtain equilibrium melting temperature (T). The T value of PTT is about 525 K, which is 10 K higher than that reported. Combining the enthalpy of fusion from the DSC result and the degree of crystallinity from WAXD result, the value of the equilibrium‐melting enthalpy ΔH was deduced to be approximately 28.8 kJ mol^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2426–2433, 2002     

Thermal decomposition of potassium persulfate in aqueous solution at 50°C in the presence of ethyl acrylate

Potassium persulfate modes of thermal decomposition and reactions with ethyl acrylate in aqueous solution at 50°C in nitrogen atmosphere have been investigated. It has been found that the rate of persulfate decomposition may be expressed as ?d(S₂O)/dt ∝ (S₂O)^{1.00 ± 0.06} × (M)^0.92±0.05 while the steady state rate of polymerization (R_p) is given by R_p ∝ (S₂O)^{0.50 ± 0.50} × (M)^{1.00 ± 0.06} in the concentration ranges of the persulfate, 10^?3?10^?2 (m/L), and monomer (M), 4.62?23.10 × 10^?2 (m/L), i.e., within its solubility range. In the absence of monomer, the rate of persulfate decomposition was slow and first order in persulfate at the early stages of the reaction when the pH of the solution was above 3.0. The separating polymer phase was a stable colloid at low electrolyte concentrations even in the absence of micelle generators. It has been shown that the oxidation of water soluble monomeric and oligomeric radicals by the S₂O ions in the aqueous phase, viz., \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm M}_j^ \cdot + {\rm S}_2 {\rm O}_8^{2 - } \to {\rm M}_j - {\rm O} - {\rm SO}_3^ - + {\rm SO}_4^{ \cdot - } $\end{document} is not kinetically significant in this system. It has been found that the reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm M} + {\rm S}_2 {\rm O}_8^{2 - } \rightarrow{k}{\rm M} - {\rm O} - {\rm SO}_3^ - + {\rm SO}_4^{ \cdot - } $\end{document} would also lead to chain initiation at the outset of the polymerization reaction. k has been estimated as 5.41 × 10^?5 (L/m/s) at 50°C. Taking k_p as 10³ (L/m/s), k_t has been estimated as 0.168 × 10⁶ (L/m/s). The partition confficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 16 ± 2, at 50°C. The rate constant for persulfate ion dissociation has been found as 1.40 × 10^?6 s^?1 at 50°C.     

Synthesis,physical properties,and crystallization of optically active poly(L‐phenyllactic acid) and poly(L‐phenyllactic acid‐co‐L‐lactic acid)

Optically active poly(L ‐phenyllactic acid) (Ph‐PLLA), poly(L ‐lactic acid) (PLLA), and poly(L ‐phenyllactic acid‐co‐L ‐lactic acid) with weight‐average molecular weight exceeding 6 × 10³ g mol^?1 were successfully synthesized by acid catalyzed direct polycondensation of L ‐phenyllactic acid and/or L ‐lactic acid in the presence of 2.5–10 wt % of p‐toluenesulfonic acid. Their physical properties and crystallization behavior were investigated by differential scanning calorimetry, thermogravimetry, and polarimetry. The absolute value of specific optical rotation ([α]) for Ph‐PLLA (?38 deg dm^?1 g^?1 cm³) was much lower than that of [α] for PLLA (?150 deg dm^?1 g^?1 cm³), suggesting that the helical nature was reduced by incorporation of bulky phenyl group. PLLA was crystallizable during solvent evaporation, heating from room temperature, and cooling from the melt. Incorporation of a very low content of bulky phenyllactyl units even at 4 mol % suppressed the crystallization of L ‐lactyl unit sequences during heating and cooling, though the copolymers were crystallizable for L ‐phenylactyl units up to 6 mol % during solvent evaporation. The activation energy of thermal degradation (ΔE_td) for Ph‐PLLA (200 kJ mol^?1) was higher than that for PLLA (158 kJ mol^?1). The ΔE_td for the copolymers increased with an increase in L ‐phenyllactyl unit content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Forced oscillations in continuous flow stirred tank reactors with nonlinear step growth polymerization

The self-step growth polymerization of RA_f monomers in homogeneous, continuous flow stirred tank reactors (HCSTRs) is simulated under conditions of periodic feed concentration (with frequency ω and amplitude α). By having periodic operation, the polydispersity index of the polymer is found to increase by about 35% over the values at steady state. Periodic operation of HCSTRs is found to lead to gelation only for certain values of the frequency and the dimensionless residence time τ^*. Gelling envelopes have been obtained to give conditions under which HCSTRs should be operated. These envelopes can be described in terms of two critical dimensionless residence times, τ and τ such that nongelling operation is always ensured when τ^* < τ. For τ^* > τ, periodic operation always leads to gelation, and HCSTRs cannot be used. For τ < τ^* < τ, the gelling behavior is found to depend on the functionality f, amplitude α, and the dimensionless residence time τ^*.     

Yield stress and flow measurements in ABA block copolymer melts

A parallel-plate constant-stress rheometer is used to measure the yield stress τ_y, and the post-yield flow curve T(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}), where τ is shear stress and \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} is shear rate, for microphase-separated triblock copolymer melts. Five polymer samples, all styrene-butadiene-styrene but with differing composition ratios and molecular weights, are tested at 125°C. Specimens are prepared by casting sheets from solutions made with different solvents. The τ(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) is found usually to be sigmoidal, for the range 10^?5 < \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} < 10^?3 s^?1, representing different stages of microstructural degradation in flow. Measurements indicate that a true τ_y exists, with values in the range 100 < τ_y < 500 Pa for these melts. A general trend is detected for τ_y to decrease as the casting solvent solubility parameter increases. A scheme for correlating the dependence of τ_y, on composition and molecular weight is proposed for the various polymers. For selected samples, the effect of mechanical history (sequence of stress application) and a temperature variation that crosses T_s (110 to 150°C) are also explored.     

Mass transport process for the adsorption of Cr(VI) onto water‐insoluble cationic starch synthetic polymers in aqueous systems

Dynamic adsorption behaviors between Cr(VI) ion and water‐insoluble amphoteric starches was investigated. It was found that the HCrO ion predominates over the initial pH ∼ 2–4, the CrO ion predominates over the initial pH ∼ 10–12, and both ions coexist over the initial pH ∼ 6–8. The sorption process occurs in two stages: the external mass transport process occurs in the early stage and the intraparticle diffusion process occurs in the long‐term stage. The diffusion coefficient of the early stage (D₁) is larger than that of the long‐term stage (D₂) for the initial pH 4 and pH 10. The diffusion rate of HCrO ion is faster than that of CrO ion for both processes. The D₁ and D₂ values are ∼ 1.38 × 10⁻⁷–10.1 × 10⁻⁷ and ∼ 0.41 × 10⁻⁷–1.60 × 10⁻⁷ cm² s⁻¹, respectively. The ion diffusion rate in both processes is concentration dependent and decreases with increasing initial concentration. The diffusion rate of HCrO ion is more concentration dependent than that of CrO ion for the external mass transport process. In the intraparticle diffusion process, the concentration dependence of the diffusion rate of HCrO and CrO ions is about the same. The external mass transport and intraparticle diffusion processes are endothermic and exothermic, respectively, for the initial pH 4 and pH 10. The k_d values of the external mass transport and intraparticle diffusion processes are ∼ 15.20–30.45 and ∼ −3.53 to −12.67 kJ mol⁻¹, respectively. The diffusion rate of HCrO ion is more temperature dependent than that of CrO ion for both processes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2409–2418, 1999     

Composition and temperature effects on air separation through liquid crystalline alkyl cellulose membranes

The air separation through triheptyl cellulose (THC)/ethyl cellulose (EC) blend membranes containing no more than 20 wt % THC at the temperature range from 298 to 358 K was investigated using a variable volume method. The air-separation ability for the THC/EC membranes were greater than that for the THC-free pure EC membrane. P for the THC/EC membranes was between 1.06–8.89 × 10^?9 cm³ (STP) cm/cm² s cmHg and P/P 3.04–3.66. The THC/EC membrane showed a unique trend in its P/P ? P relationship, i.e., the magnitude of P/P increased simultaneously with that of P. The THC/EC membrane yielded a maximum oxygen concentration in the oxygen-enriched air (OEA) of 39.5% at an OEA flux of 6.99 × 10^?4 cm³ (STP)/s cm² for a pressure difference of 0.43 MPa at 358 K. After 300 h of measurement at 0.40 MPa and 313 K, the efficiency of the concentrating oxygen was almost constant. © 1994 John Wiley & Sons, Inc.     

The rheology and spin coating of polyimide solutions

The rheological properties of five types of concentrated polyamic acid and polyimide solutions are characterized by non-Newtonian shear viscosity η(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma} $\end{document}) and primary normal stress coefficient Ψ₁(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma} $\end{document}) measurements over a wide range of shear rates. Onset of non-Newtonian flow of the polyamic acid solutions was observed in the shear rate range 30 to 400s^?1 and of the fully imidized polyimide solution at below 3 × 10^?2s^?1. Significant viscoelastic properties exemplified by normal stresses were observed in all the solutions. The solution rheology results are discussed in the context of spin coating for the deposition of thin films. The relative magnitude of effects of non-Newtonian flow on the dynamics of spin coating is assessed with a Deborah number characteristic of the flow.     

Intrinsic birefringence of nylon 6

Different values are reported in the literature for the intrinsic birefringence of the crystalline (Δn) and the amorphous (Δn) phases in nylon 6. Mostly, these values have either been determined by extrapolation (and then it is assumed that Δn = Δn) or calculated theoretically. In this study, intrinsic birefringence values Δn and Δn for nylon 6 were determined using the Samuels two-phase model which correlates sonic modulus with structural parameters. Three series of fiber samples were used: (1) isotropic samples of different degrees of crystallinity for estimation of E and E moduli at two temperatures. The following modulus values were obtained: 1.62 × 10⁹ and 6.66 × 10⁹ N/m² for 28.5°C, and 1.81 × 10⁹ and 6.71 × 10⁹ N/m² for ?20°C; (2) anisotropic, amorphous fiber samples for estimation of Δn = 0.076 and E = 1.63 × 10⁹ N/m² at 28.5°C; (3) semicrystalline samples of various draw ratios for estimations of Δn = 0.089 and Δn = 0.078. All measurements were carried out with carefully dried samples to avoid erroneous results caused by moisture.