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.     

Dynamic stress intensity factors during viscoelastic crack propagation at various strain rates

Dynamic stress intensity factors K_D were measured by the caustic method and crack propagation velocity ? by the velocity gauge techniques for PMMA [poly(methyl methacrylate)] during dynamic crack propagation at various strain rates \documentclass{article}\pagestyle{empty}\begin{document}$ \rm \dot \varepsilon $\end{document} . No definite applied strain rate effects on the dynamic stress intensity factor were observed for applied strain rates ranging from 8.33 × 10^?4 to 30/sec; however, the test results do show crack propagation velocity dependency in K_D ～ ? relations. The high local strain rate region may be realized at the running crack tip even under the quasi-static loading case of \documentclass{article}\pagestyle{empty}\begin{document}$ \rm \dot \varepsilon $\end{document} = 8.33 × 10^?4/sec, since all the crack propagation velocities obtained were greater than 50 m/sec even up to 450 m/sec.     

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.     

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.     

Influence of electrolytes on the absorption of nitrogen oxide components N2O4 and N2O3 in aqueous absorbents

The influence of electrolytes, which are dissolved in the aqueous absorbent and do not react with nitrogen oxides, on the absorption kinetics of both these components was investigated experimentally. In addition to demineralized water, various salt solutions of different concentrations as well as sodium hydroxide solution were used as absorbents. The term H \documentclass{article}\pagestyle{empty}\begin{document}$ H\sqrt {k_1 D} $\end{document} for N₂O₄ and N₂O₃, which is important for the design of industrial absorbers, was determined as a function of composition and concentration of the absorbents. In the case of N₂O₄, the chosen measuring and evaluation methods permitted a separate determination of the rate constant k of the pseudo first order reaction and of the solubility H. The diffusion coefficient D of the gas in the absorbent can be obtained only by calculation. Experimental results showed that \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document} decreases with increasing ionic strength I, however, without a clear indication of any ion-specific effects. This decrease does not appear to be caused simply by a reduction in solubility (salting out effect), or in diffusion coefficient, but at least, to the same extent, through a decrease of the rate constant k with increasing electrolyte content in the absorbent. The measurements permitted the determination of the gas-based salting out parameter for N₂O₄. The investigations on the absorption of N₂O₃ in water and in an Na₂SO₄ solution showed no experimentally detectable influence of dissolved salts on \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document}. The numerical value of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document} is six times that of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document}.     

A new insight into the mechanism of influence of different inorganic salts on optical properties of water‐soluble cationic conjugated polymers

The water‐soluble conjugated polyelectrolyte poly{2,5‐bis[3‐(N,N,N‐triethylammoniumbromide)‐1‐oxapropyl]‐1,4‐phenylenevinylene} (P2) was synthesized and the influences of different inorganic salts on the optical properties of the polyelectrolyte were studied. New absorption and emission peaks at longer wavelength can be observed in the case of P2 with addition of different concentrations of Cl^? or NO₃^?, whereas addition of I^? or ClO₄^? only induces a red shift. Interestingly, addition of SO₄^2? or F^? does not result in considerable changes in optical spectra. Through UV‐visible spectrometry, photoluminescence, ¹H NMR and cyclic voltammetry, we showed that the nature of the inorganic salts brings these different changes. The special structure of the bond of NO₃^? and the large electronegativity of chlorine lead to an electron transfer between the conjugated polymer and the negative ions. The large radius of I^? and the weak electron withdrawing ability of ClO₄^? only bring a red shift of optical spectra. In addition, SO₄^2? and F^? do not affect the spectra significantly, except that the fluorescence intensity falls slightly indicating that P2 is not sensitive to these ions. Copyright © 2011 Society of Chemical Industry     

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     

Light-scattering studies on solutions of high and low molecular weight polystyrene mixtures used as models of microgel-containing solutions

Diluted solutions of linear polystyrene (PS) in toluene and dioxane were studied by the light-scattering method. The solutes were mixtures of high-M?_w and low M?_w PS. The dissolved PS mixtures were regarded as polymer solutions containing microgels, the high-M?_w PS being looked upon as the microgel counterpart. The calculation method as proposed by Strazielle¹ and Burchard² was used to evaluate the microgel percentage and particle size, whereby the method could be verified against mixtures with well-known weight composition and \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document}. The \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} values evaluated for the mixtures from the experimental data were compared with those estimated from the molecular weights of the components, their weight concentrations, and their \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} values. The method^1,2 was found to be useful for evaluating the microgel content in a sample, but not for \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} values as calculated by Guinier's procedure nor those calculated by Zimm's procedure; the former were low and the latter were even incongruous. A comparative analysis of the theoretical function P^?1(θ)-versus-sin² (θ/2) and experimental (Kc/R(θ))_c=0-versus-sin² (θ/2) curves allowed to discuss the effect of the course of these curves at samll angles from 0° to 30° on M?_w and \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} as determined for the high and low molecular weight polystyrene mixtures in toluene as solvent.     

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.     

Effect of polymer microstructure on dye diffusion in polyamide 66 fibers

Our previous work showed that drawing polyamide 66 (PA 66) fibers at room temperature does not change the degree of crystallinity, but only increases the molecular orientation. We therefore have used a series PA 66 fibers with different draw ratios to establish a direct correlation between (noncrystalline) molecular orientation f_a and the dye diffusion coefficient D. For both acid and disperse dyes, the relationship log D ∝ f provides reasonable fits to the data for PA 66 fibers, and a similar relationship appears to be applicable to PA 6 fibers. Heat‐setting the fibers results in a continuous decrease in diffusion coefficient; unlike PA6 and PET fibers, no minimum in D was found in the region of 160°C. If this decrease in D is attributed to the increase in volume fraction crystallinity X taking place during heat‐setting, it must be deduced that log D ∝ X⁶. This dependence is surprisingly strong, but is consistent with observations we have made on PET and PA6 fibers. It is possible that some other structural rearrangement is partially or largely responsible for the decrease in diffusion coefficient, but Fourier transform infrared, density, and X‐ray diffraction measurements do not indicate any other structural changes taking place. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3803–3807, 2003     

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     

Simulation and optimal design of seeded continuous emulsion polymerization process

Simulation and optimal design of the reactor for the seeded continous emulsion polymerization process have been done in this work. An internal mixer (Toray Hi-Mixer) as seeder connected with a stirred tank is designed to correlate conversion, molecular weight, and MWD with the model simulation proposed. An optimal mean residence time of seeder \documentclass{article}\pagestyle{empty}\begin{document}$(\bar \theta _s)_c$\end{document} is found to lie between \documentclass{article}\pagestyle{empty}\begin{document}$(\bar \theta _1)$\end{document} and t_in, where \documentclass{article}\pagestyle{empty}\begin{document}$(\bar \theta _1)_{{\rm opt}} = (3aS_0 /2r\eta N_a \alpha)^{3/5}$\end{document} and t_in = 1.57(aS₀/r_iηN_A)^3.5. The optimal design of the process is performed according to the above relations under several polymerization conditions. In general, the increase in number of stages inside the seeder can reduced the volume of CSTR for a required production. Molecular weight of products is increased by increasing the number of stages inside the seeder, by decrasing the concentration of the initiator, and by increasing the concentration of the emulsifier under the optimal conditons.     

Simultaneous sorption and diffusion of a 4-aminoazobenzene derivative and its conjugate acid in cellulose membrane carrying sulfonic acid groups

An azo dye, 2-methyl-N,N-bis(2-hydroxyethyl)-4-aminoazobenzene (nonionic dye) and its conjugate acid (cationic dye) are simultaneously adsorbed by the cellulose membranes carrying sulfonic acid groups from a slightly acidic aqueous solution. Sorption equilibria of the nonionic and the cationic dye are described in terms of the Henry's partition and the ionic exchange mechanism, respectively, in the latter case, the ion exchange constants obtained for the membrane with sulfonic acid group content (SAG) = 261 meq/kg at 30°C are K = 1.43 × 10^?5 and K = 0.542, respectively, where Na, H, and DH refer to sodium, hydrogen, and cationic dye ions. The diffusion coefficients of the nonionic dye (D_N) and the cationic dye (D_C) in the membranes were estimated from the permeation data of the dyes through the membrane. Both D_N and D_C decrease with increasing SAG. The ratio D_N/D_C ranged in 2.2–10, the ratio increases with the SAG.     

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     

Polymer melt elongation—methods,results, and recent developments

For film blowing of polyethylene it has been shown previously that melt elongation is very powerful for polymer characterization. With two types of rheometers, simple (also called “uniaxial”) elongational tests as well as creep tests can be performed homogeneously. In simple elongation, the melts of branched polyethylene show a remarkable strain hardening. With respect to their advantages and disadvantages, these rheometers complement each other. For multiaxial elongations the various modes of deformation can be performed by means of the rotary clamp technique. With the strain rate components ordered such that \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}₁₁ ? \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}₂₂ ≥ \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}₃₃, the ratio m = \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}₂₂/\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}₁₁ characterizes the test mode. The Stephenson definition of the elongational viscosities makes use of the linear viscoelastic material equation and proves to be very efficient because the linear shear viscosity (t) (“stressing” viscosity) can act as the reference for the nonlinear behavior in elongation. Results are given for polyisobutylene measured not only in simple, equibiaxial, and planar elongations, but also in new test modes with a change of m during the deformation. This allows one to investigate the consequences of a deformation-induced anisotropy of the rheological behavior.     

Relation between kneading behavior and flow instability of a high molecular weight high density polyethylene,applications to extrusion

Non-monotonic continuous curves of torque as a function of shaft speed, M(N), have been obtained for a high molecular weight high density polyethylene (HDPE) from measurements obtained with a torque rheometer (Haake Rheocord). Previous papers have given theoretical demonstration of the non-monotonic character of the shear stress-shear rate function, s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}), which makes it possible to explain the extrusion behavior of a high molecular weight HDPE. In capillary rheometry, it is not possible to obtain the values of s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) into the “well zone” of this function because the compressibility of the polymer creates a phenomenon of oscillation in the barrel affecting the die output flow rate and the pressure loss. The M(N) function measured by the Haake Rheocord is a complete representation of the s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) function, although the capillary rheometer only gives a partial representation of this function. The transformation of the M(N)function into s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) is quite difficult because of the complex geometry of the Haake Rheocord measuring head. The “critical points” of the s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) function in the capillary rheometer (appearance of oscillations), can be correlated to the maximum points of the M(N) function in the Haake Rheocord at constant temperature. The non-monotonic aspect of the s(\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) function provides an important technological application: extrusion of a high molecular weight HDPE at an increased flow rate at low temperatures.     

A simplified theory for generalizing results from a radiant panel rate of flame spread apparatus

Experimental results on the rate of lateral flame spread and time for piloted ignition under an externally imposed radiant flux were analyzed with a simple theroretical model. The data were developed from a radiant panel apparatus that considers a wall mounted sample with a flux distribution \documentclass{article}\pagestyle{empty}\begin{document}$ (\dot q_{\rm e} ^{\prime \prime } ) $\end{document} of 5 W cm^?2 at the ignited end to 0.2 W cm^?2 at the other end. It is shown that after an appropriate preheating time (flux exposure time before sample is ignited) the rate of flame spread (V_f) results can be correlated by \documentclass{article}\pagestyle{empty}\begin{document}$ V_{\rm f} - {\textstyle{1 \over 2}} = C\left( {\dot q''_{{\rm o,ig}} - \dot q_{\rm e} ^{\prime \prime } } \right) $\end{document} where C is a material ‘constant’ and \documentclass{article}\pagestyle{empty}\begin{document}$ \dot q''{\rm }_{{\rm o,ig}} $\end{document} is minimum flux for piloted ignition—also a material (and configuration) constant. An extension of this model demonstrates that V_f can also be expressed in terms of an ‘ignition temperature’ and the surface temperature of the material. Both correlations are derivable from a single flame spread experiment. Results are presented for a number of typical wood and plastic materials.     

Empirical correlation of flow properties of poly(vinyl chloride)

Empirical correlations of flow properties of poly(vinyl chloride) were made using data reported by a number of investigators. Correlation was made by plotting the reduced variable viscosity η/η₀ versus \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w )/(_\rho RT) $\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w ^{0.5} )/(_\rho RT) $\end{document} for unplasticized PVC and versus \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w ^{0.5} )/(_\rho RTW_2 ^a ) $\end{document} with polymer concentration, W₂, for PVC containing plasticizer.     

Determination of carboxyl endgroups and comonomers in poly(ethylene terephthalate) with hydrazine

On complete hydrazinolysis of poly(ethylene terephthalate), terephthalomonohydrazide is formed from carboxyl-end terephthaloyl residues in a quantity equivalent to the content of carboxyl endgroups in the polymer. The compound is separated from the reaction mixture by ion exchange and determined photometrically [epsiv;₂₄₀ in 0.1 N HCl = 16,700 (1000 cm²/mole)]. A COOH determination carried out in this way is endgroup specific and, unlike titration, is not subject to interference by ionogenic fiber additives. Aromatic comonomers with acidic substituents (e.g., 5-sulfoisophthalic acid) in chemically modified, cationically dyeable poly(ethylene terephthalate) are determined simultaneously with the carboxyl endgroups by the same analytical method. In this case, the terephthalamonohydrazide and 5-sulfoisophthalodihydrazide are separated by ion exchange, and the difference in their spectral behavior is used for quantitative determination with the aid of a two-component analysis: where c₁c₂ = concentration of terephthalomonohydrazide and 5-sulfoisophthalodihydrazide, respectively; and D₂₄₀ D₂₁₂ = optical density at 240 and 212 nm, respectively. The content of carboxyl endgroups in polyether esters poly(p-(2-ethyleneoxy)-benzoate), is determined on the basis of the p-(β-hydroxyethoxy)benzoic acid [epsiv;₂₅₈ in 0.1 N HCl = 16,100 (1000 cm²/mole)] liberated from carboxyl-end monomer units by hydrazinolysis. For copolyether esters with p-(β-hydroxyethoxy)benzoic acid as a comonomer, the contents of carboxyl-end terephthalic acid and p-(β-hydroxyethoxy)benzoic acid are determined simultaneously with the acid of a spectrophotometric twocomponent analysis: where c₂, c₂ = concentration of terephthalomonohydrazide and p-(β-hydroxyethoxy)-benzoic acid, respectively; and D₂₄₀, D₂₅₈ = optical density at 240 and 258 nm, respectively.     

Melt rheology and extrudability of polyethylenes

Commercial high density polyethylene (HDPE), low density polythylene (LDPE), and linear low density polyethylene (LLDPE) resins were tested at 150, 170, and 190°C in steady state, dynamic, and extensional modes. Within the low rates of deformation \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω ≤ 0.3, the steady state and dynamic functions agreed: η = η′ and N₁ = 2G′; at the higher rates, the steady state parameters were larger. The elongational viscosity, η_e, was measured under a constant rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, or stress, σ, condition. In the first case for LLDPE, the transient η reached an equilibrium plateau value, η_e. For HDPE, η increased up to the break point. For LDPE, stress hardening was recorded. Under constant stress the η_e, could always be determined; its value, within experimental error, agreed with the maximum value of η determined in a constant \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document} experiment. The maximum strain at break was only ε = 1.5 for HDPE and 3, to 4 for LDPE and LLDPE. The rate of deformation dependence of the η (or η′) and η_n may be discussed in terms of the Trouton ratio, R_T = η_e/3η at \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω = \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document}: R_T ≤ 1.2 for LLDPE, R_T ≤ 2.5 for HDPE, and R_T ≤ 15 for LDPE. The PE resins were extruded at 190°C through a laboratory extruder equipped with a slit or rod die. The rotational speed of the screw varied from 0 to 90 rpm. Extrusion pressure, output, and energy were measured and correlated with the rheological parameters of the resins.