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.     

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     

Carbon‐13 nuclear magnetic resonance investigation of styrene–α‐methylstyrene copolymers

A copolymer based on α‐methylstyrene (AMS) was investigated by nuclear magnetic resonance (NMR). The styrene‐co‐α‐methylstyrene (SAMS) was analyzed by solution and solid‐state NMR techniques. Three copolymers of SAMS with different compositions presented a particular behavior. The solution results showed the copolymer microstructure and the AMS content. The carbon‐13 spectra of SAMS C indicated that the AMS CH₃ signal was detected at three distinct chemical shifts, because of the different comonomer‐sequences distribution. The proton spin–lattice relaxation time in the rotating frame (Tρ) parameter was chosen because it permits the evaluation of changes in the molecular mobility. The values of Tρ found for the copolymers confirmed the random distribution in the samples. The copolymer with a low quantity of AMS (1.7%), when analyzed by this relaxation parameter, showed lower values that were interpreted as an antiplasticization effect. The SAMS copolymer with a higher AMS quantity showed a plasticization effect. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 261–266, 2001     

Atom‐transfer radical polymerization of methyl methacrylate with α,α′‐dichloroxylene/CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine initiation system under microwave irradiation

The atom‐transfer radical polymerization (ATRP) of methyl methacrylate (MMA), using α,α′‐dichloroxylene as initiator and CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst was successfully carried out under microwave irradiation (MI). The polymerization of MMA under MI showed linear first‐order rate plots, a linear increase of the number‐average molecular weight with conversion, and low polydispersities, which indicated that the ATRP of MMA was controlled. Using the same experimental conditions, the apparent rate constant (k) under MI (k = 7.6 × 10^?4 s^?1) was higher than that under conventional heating (k = 5.3 × 10^?5 s^?1). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2189–2195, 2004     

Synthesis,characterization, and thermodynamic properties of poly(3‐mesityl‐2‐hydroxypropyl methacrylate)

Poly(3‐mesityl‐2‐hydroxypropyl methacrylate) (PMHPMA) was synthesized in a 1,4‐dioxane solution with 2,2′‐azobisisobutyronitrile as the initiator at 60°C. The homopolymer and its monomer were characterized with ¹H‐ and ¹³C‐NMR, Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and elemental analysis techniques. According to size exclusion chromatography analysis, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of PMHPMA were 65,864 g/mol, 215,375 g/mol, and 3.275, respectively. According to thermogravimetric analysis, the carbonaceous residue value of PMHPMA was 14% at 500°C. The values of the specific retention volume, adsorption enthalpy, sorption enthalpy, sorption free energy, sorption entropy, partial molar free energy, partial molar heat of mixing, weight fraction activity coefficient of solute probes at infinite dilution (Ω), and Flory–Huggins interaction parameter (χ) were calculated for the interactions of PMHPMA with selected alcohols and alkanes by the inverse gas chromatography method at various temperatures. According to Ω and χ, selected alcohols and alkanes were nonsolvents for PMHPMA at 423–453 K. Also, the solubility parameter of PMHPMA (δ₂) was found to be 24.24 and 26.33 (J/cm³)^0.5 from the slope and intercept of (δ/RT) ? χ/V₁ = (2δ₂/RT)δ₁ ? δ/RT at 443 K, respectively [where δ₁ is the solubility parameter of the probe, V₁ is the molar volume of the solute, T is the column temperature (K), and R is the universal gas constant]. The glass‐transition temperature of PMHPMA was found to be 386 and 385 K by inverse gas chromatography and differential scanning calorimetry techniques, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 101–109, 2006     

The degradation and prestabilization of acrylonitrile copolymers

The degradation and prestabilization of polyacrylonitrile (PAN) were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The initial temperature, initial loss‐weight temperatures, and loss‐weight were significantly lowered when ammonium itaconate (AIA) was used as comonomer. One exothermal peak of PAN (homopolymer) was shown in the DSC curves, while there were four exothermal peaks of poly(AN‐AIA). FTIR spectra results confirm the degradation process of NH groups. During the heating process, NH groups (3030 cm^?1) were changed into NH (2955 cm^?1) and then NH groups (2920 cm^?1). The dissociated H⁺ could initiate the cyclization reactions of C?N companied with heat released. The effect of ammonia on degradation and prestabilization of PAN was also studied. It was found that ammonia could accelerate prestabilization of acrylic precursors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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^*.     

Fundamental studies on a new series of SPSEBS‐PVA‐QPSEBS bipolar membrane: Membrane preparation and characterization

A sulfonated polystyrene ethylene butylene polystyrene (SPSEBS)‐poly(vinyl alcohol) (PVA)‐Quaternized polystyrene ethylene butylene polystyrene (QPSEBS) bipolar membrane (BPM) was prepared by lamination method using PSEBS as the starting material, the functionalization of which was modified by sulfonation and amination while PVA was used as the intermediate layer to enhance the water splitting efficiency. The cross section view of SPSEBS‐PVA‐QPSEBS BPM was studied by SEM. Fourier transform infra‐red spectroscopy (FTIR) studies indicated that the prepared BPM contained –SO, –NR, and –C‐N functional groups. The thermal stability of the prepared BPM was studied by thermogravimetric analysis (TGA). Some of the BPM characteristics results showed that the co‐ion fluxes was greater for t(0.065) when compared with t(0.051) along with a water splitting capacity value of 0.88 for SPSEBS‐PVA‐QPSEBS BPM. The water dissociation flux was 2.8 × 10^?5 mol/m²/s and 2.2 × 10^?5 mol/m²/s for the acid (H⁺) and base (OH^?), respectively. The other essential current‐voltage characteristics and permeate flux across the membrane were also evaluated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci 2013     

Influence of anionic form on thermal degradation of TMAHP–cellulose

Trimethylammoniumhydroxypropyl (TMAHP)–cellulose in 10 anionic forms (F^?, Cl^?, Br^?, I^?, HSO, NO, OH^?, HCO, H₂PO, CH₃COO^?) was prepared, and the influence of each anion on thermal degradation in inert atmosphere was studied. With the help of dynamic and isothermal thermogravimetry (TG) it was found that H₂PO ions had the greatest retarding effect on TMAHP–cellulose degradation. From the values of rate constants it can be seen that all ionic forms of TMAHP–cellulose have the starting rate of thermal degradation greater than unmodified cellulose. The calculated values of activation energy of thermal degradation for different ionic forms are decreasing in following sequence: H₂PO > F^? > NO > I^? > Br^? > HCO > Cl^? > HSO > OH^? > unmodified cellulose > CH₃COO^?. From the results of pyrolyse measurements in combination with gas chromatography and mass spectrometry (Py–GC–MS) it follows that the products of the elimination of quarternary ammonium salts are trimethylamine, 3-hydroxy-2-propanone, and, in the case of OH^? form, water. In all other ionic forms the third product is the corresponding acid.     

Synthesis,characterization, and metal‐ion uptake studies of chelating resins derived from formaldehyde‐condensed azodyes of aniline and 4,4′‐diaminodiphenylmethane coupled with phenol/resorcinol

The diazonium salts of aniline and 4,4′‐diaminodiphenylmethane coupled with phenol and resorcinol were condensed with formaldehyde in alkaline media to yield polymeric resins. These polymers were found to readily react with metal ions like Cu²⁺ and UO, forming polychelates. The azodyes, resins, and polychelates were characterized by several instrumental techniques such as elemental analysis, FTIR, ¹H‐NMR, GPC, XRD, TG–DTG, and DSC studies. The chelating capacity of the resins toward Cu²⁺ and UO ions was studied by spectrophotometry. The extent of metal loading of the resins was studied by varying the time of contact, metal‐ion concentration, and pH of the reaction medium. The alkali and alkaline earth metal ions had little effect on the metal‐ion uptake behavior of the resins. The resin derived from the azodye of 4,4′‐diaminodiphenylmethane was found to be more efficient in removing the metal ions from solution than were the resins from aniline. The optimum conditions for effective separation of Cu²⁺ from UO were determined. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3128–3141, 2000     

Experimental studies on the relaxation behavior of commercial polymer melts

With a rotary rheometer, various methods were used to determine the characteristic relaxation times for a commercial polydimethylsiloxane (PDMS), and their consistency and relation to the linear relaxation spectrum were examined. The experimental damping functions of the step deformation of the PDMS, a polymethylvinylsiloxane, and a high‐density polyethylene were compared with predictions of the Doi–Edwards theory and Marrucci model; the effect of wall slip on the damping function data is discussed, and the appearance of stress peaks due to material instability as the strain increased above a critical value is detailed. Through the application of a previously proposed stress decomposition method to the data of large‐amplitude oscillatory shear for the PDMS sample, the relationship between the generalized elastic modulus [G(ω,γ)] and the shear relaxation modulus [G(γ,t)] was investigated. In the linear and initial nonlinear regimes, as the angular frequency (ω) increased, G(ω,γ) approached G(γ,t) on the timescale t = 1/ω, where t is the time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of ultraviolet‐curable modified polysiloxane and its surface properties

A novel ultraviolet (UV)‐curable monomer α,ω‐dichloropolysiloxane was synthesized by the telomerization of dichlorodimethylsilane and octamethylcyclotetrasiloxane (D₄). The products with very low peel strength (<0.332 N/cm) could be used as release agents in pressure‐sensitive adhesives. Moreover, the values of the dispersion component of surface energy (γ) from the films of UV‐curable prepolymers (26.40–33.75 mJ/m²) were determined and the effects of γ on the reduction of adhesion were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2135–2139, 2002     

Oxygen/nitrogen transport in ionomer composite membranes containing a cobalt Schiff base complex

Different amounts of (N,N′‐disalicylideneethylenediamin)cobalt (CoS) were blended to a cobalt (II)‐neutralized sulfonated EPDM (Co^(II)‐S‐EPDM) ionomer membrane to enhance its oxygen‐enriching ability. Various influence factors on permeabilities and selectivities of the composite membranes, such as the gas pressure difference, the CoS content, and the testing temperature have been investigated. Oxygen permeability coefficients (P) and oxygen/nitrogen separation factors (α) increased simultaneously by decreasing the gas pressure difference or by increasing the CoS content. In comparison with the EPDM matrix, P and α of Co^(II)‐S‐EPDM–CoS (85/15) composite membrane increased from 11.0 Barrer and 4.38 to 37.0 Barrer and 9.60. Obvious enhancement in the oxygen‐enriching property shows that the dual actions of cobaltous ion crosslinking and addition of an abundant cobalt complex may be an effective way to improve a rubbery polymer membrane. As high as 15 wt % of the CoS could be blended. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1071–1077, 1999     

Electrochemical synthesis and properties of poly(3‐methylthiophene): Novel synthesis of poly(3‐methylthiophene) with pentachlorostannate and hexachloroantimonate

Poly(3‐methylthiophene) (P3‐MeT) doped with different anions were prepared electrochemically in the presence of tetraalkylammonium salts. The new poly(3‐methylthiophene) SnCl and SbCl (P3‐MeT SnCl₅ and P3‐MeT SbCl₆) were prepared electrochemically using tetra‐n‐butylammonium pentachlorostannate and tetra‐n‐butylammonium hexachloroantimonate as the supporting electrolytes. The effect of current density, salt concentration, reaction temperature, and the nature of solvents on the polymer yield and polymer conductivities have been investigated. Cyclic voltammetry of poly(3‐methylthiophene) has been examined at platinum electrode in 1,2‐dichloroethane medium containing n‐Bu₄NSnCl₅, Bu₄NSbCl₆, and Bu₄NClO₄ as the supporting electrolytes in the range of −1.0 to 1.7 V versus SCE in the presence and absence of 3‐methylthiophene. Electrical conductivity, magnetic susceptibility measurements, and structural determination by elemental analysis and infrared studies were also made. Scanning electron microscopy revealed a globular, branched, fibrous and a spongy, fibrous morphology of poly(3‐methylthiophene) SnCl, ClO, and SbCl, respectively. The thermal analysis of the polymers was also investigated. Possible causes for the observed lower conductivity of these polymers have also been discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 91–102, 1999     

Morphological studies of the modified materials: Low-density polyethylene/poly(acrylic acid)/europium(III) and low-density polyethylene/poly(acrylic acid)/uranyl ion

The morphology of low-density polyethylene (LDPE) modified by in situ sorption and thermal polymerization of acrylic acid (AA) in the matrix was examined. The microstructure of the LDPE/poly(acrylic acid) (PAA) materials after Eu³⁺ and UO ion exchange was investigated. The phase behavior of these materials was analyzed using X-ray diffraction, scanning electron microscopy (SEM), and thermal measurements (DSC). The X-ray dif-fraction studies showed that PAA is located at amorphous region of the matrix. The LDPE/PAA surface, as investigate by SEM, was apparently homogeneous before and after Eu³⁺ and UO ion exchange, respectively. Two T_g values were found for the LDPE/PAA material before and after Eu³⁺ ion exchange. Also, three and four T_g values were found for LDPE/PAA after UO ion exchange depending on the amount of UO in the modified matrix. This indicates microphase domains in the LPDE/PAA-, LPDE/PAA/Eu³⁺-, and LPDE/PAA/UO -modified materials, although a lack of visible phase separation in the micrographs was observed. © 1996 John Wiley & Sons, Inc.     

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     

Solution and diffusion properties of cyclohexane,cyclohexanol, and cyclohexanone in poly(ethylene glycol) by inverse gas chromatography

The solution and diffusion properties of cyclohexane, cyclohexanol, and cyclohexanone in poly(ethylene glycol) (PEG) and crosslinked PEG have been studied in the temperature range of 368.15 to 403.15 K using inverse gas chromatography (IGC) technique. The infinite dilute activity coefficient (Ω) and diffusion coefficient (D) have been determined for the above solvent/polymer systems. Accordingly, several thermodynamic functions, the diffusion pre‐exponential factor, and activation energy have been attained. The results showed a decrease in Ω and an increase in D with rising temperature. The order of the relative magnitude of Ω and D of the solvents were explained by comparing their interactions with the polymer and their collision diameters, respectively. Moreover, Ω and D in crosslinked PEG were smaller than those in PEG at various temperatures. The analysis of Ω, the infinite dilute selectivity and capacity showed the possibility of using crosslinked PEG as an appropriate membrane material for the separation of cyclohexane, cyclohexanol, and cyclohexanone mixture. A thermodynamic study also implied that the solvent sorptions in the polymers were all enthalpically driven in the experimental range. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Adsorption of a gold‐iodide complex (AuI2−) onto cellulose acetate‐polyaniline membranes: Equilibrium experiments

The adsorption of AuI complex onto acetate cellulose‐polyaniline membranes was investigated. Kinetic experiments showed a rapid adsorption of this complex, which was attributed to an ion‐exchange mechanism. Equilibrium adsorption results were represented by the Langmuir model, showing a correlation coefficient of 0.9852. Langmuir parameters K and Q_m were found to be 0.2937 L mg^?1 and 1.2394 mg g^?1, respectively. Approximately 94% of AuI was adsorbed when a solid/liquid ratio of 40 g L^?1 (grams of membrane/ liter of solution) was used. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Several features of vinyl chloride–diallyl phthalate suspension copolymerization

Vinyl chloride–diallyl phthalate (VC–DAP) suspension copolymerization was carried out in a 5‐L autoclave and 200‐mL stainless steel vessel at 45°C. The apparent reactivity ratios of VC–DAP suspension copolymerization system were calculated as r_VC = 0.77 and r_DAP = 0.37. It shows that VC–DAP copolymer contains no gel when the feed concentration of DAP (f) is lower than a critical concentration (f_cr, inside the range of 0.466–0.493 mmol/mol VC at 80–85% conversion), the polymerization degree (DP) of copolymer increases with the increase of f and conversion. VC–DAP copolymer is composed of gel and sol fractions when f is larger than f_cr. The DP of sol fraction decreases as f increases, but the gel content and the crosslinking density of gel increase. The gel content also increases as conversion increases. The results also show that the index of polydispersity of molecular weight of sol changes with f, a maximum value appears when f is close to f_cr. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 156–162, 2000