bluuebunny/crossref_metadata_2025 huggingface dataset:
Propylene polymerization in a semibatch slurry reactor over supported TiCl4/MgCl2/ethyl benzoate/triethyl aluminum catalyst. II. A kinetic study based on a multisite model
Authors: Dumas Constantine , Hsu Cheng C.
Published: April 2003

In propylene polymerization over TiCl4/MgCl2/ethyl benzoate (EB)/triethyl aluminum (TEA) catalysts, experimental evidence strongly suggests that active sites have differing propagation and termination rate constants. Although the chemical structure of these sites may be quite similar, their location on the support may affect their polymerization activity, and this results in a distribution of the propagation and deactivation rate constants. To model this type of system, we developed a kinetic model accounting for multiple active sites. The model was fitted to simulated polymerization data to investigate the validity of mathematical approximations used in the derivation of the model equation. Using experimental data, the adequacy of the model was tested, and the statistical inference of parameter estimation was also discussed. The effects of experimental operating variables and additives on the kinetic model parameters revealed an important insight into the fundamentals of this system. The optimum productivity commonly observed has been shown to be the result of differing rates of increase of both propagation and termination rates with Al/Ti ratio and temperature. Kinetic evidence also suggests that the additive selectively poisons atactic‐specific sites.
Dielectric relaxation study of low‐density polyethylene by thermally stimulated depolarization currents and thermal sampling
Authors: Dueñas J. M. Meseguer , Ribelles J. L. Gomez , Calleja R. Diaz
Published: April 2003

The dielectric relaxation zone of a low‐density polyethylene has been studied by thermally stimulated depolarization currents (TSDC) and thermal sampling (TS). Three relaxations have been found in this zone, which have been labeled γI, γII, and γIII in decreasing order of temperature. Samples of different crystallinities were subjected to several thermal treatments in order to study the molecular origin of each relaxation. The γI relaxation intensity changes with the thermal treatment, while the intensity of the γI relaxation is only slightly modified. Using TS it has been proved that the γI relaxation fulfils the compensation law with a high level of significance. Nevertheless, the experimental data are not enough to verity the γI and γIII relaxation.
Preparation and properties of UV‐autocurable BTDA‐based polyurethane methacrylates
Authors: Chiang Wen‐Yen , Chan Shao‐Ching
Published: April 2003

Syntheses of several UV‐autocurable methacrylourethanes and the effects of polyol type on their properties are investigated. Autocurable benzophenone tetracarboxylic dianhydride (BTDA)‐based polyurethane methacrylates are prepared by addition reaction from benzophenone tetracarboxylic dianhydride (BTDA), 2,4‐toluene diisocyanate (TDI), 2‐hydroxyethyl methacrylate (HEMA), and polyol (polyethylene glycol, polydiethylene succinate, polydiethylene maleate, or polydiethylene hexamethylene‐dicarbamate). Autocurable oligomers possess good pot life and are cured rapidly when exposed to ultraviolet (UV) radiation without the addition of photoinitiator. The different polyols are used to obtain wide range properties of cured films with a glass transition temperature (Tg) range of ‐10.5‐5.5°C. Increasing the Tg of polyol shifts the dynamic mechanical storage modulus and loss factor of the cured film to high temperature. For practical application, oligomer is mixed with reactive monomers to bring the systems to a workable viscosity at room temperature. Among the monomers, the higher the composition of hydroxyethyl acrylate in the oligomer‐monomer system, the higher the curing rate of the system as compared with neat oligomer. Moreover, increasing the chain length of dimethacrylate monomers results in a decrease in breaking strength from 160 to 140 kg/cm2, in Young's modulus from 771 to 400 kg/cm2, and in glass transition temperature from 18 to 6.5°C, while the elongation at breaking increases from 70 to 130%.
A zeolite/polymer membrane for separation of ethanol‐water azeotrope
Authors: Goldman Mariana , Fraenkel Dan , Levin Gideon
Published: April 2003

A novel membrane effective in the separation of ethanol‐water mixtures by pervaporation was made by combining zeolite NaA and poly(vinyl chloride) modified by 2‐(2′‐butoxyethoxy)ethyl thiolate. Under ambient conditions, a separation factor (α) of 29 and pervaporability (P) of 4 × 10−4 g m−1 h−1 were obtained for the azeotropic mixture whereas, in the absence of zeolite, the respective values were 7 and 7 × 10−5. A mechanism was proposed relating the preferential water transport at ≈︁ 50% zeolite content to an interfacial “phase” between the zeolite and the modified polymer.
Effect of diantimony trioxide on direct esterification between terephthalic acid and ethylene glycol
Authors: Yamada Toshiro
Published: April 2003

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 (ki) 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.

Sb2O3 accelerates the esterification reaction between TPA and EG.

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).

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.
Rheological behavior of SAN/PC blends under extremely high shear rate
Authors: Takahashi Hideroh , Matsuoka Takaaki , Ohta Takashi , Fukumori Kenzo , Kurauchi Toshio , Kamigaito Osami
Published: April 2003

Extremely high shear rate processing was applied to the compound system of acrylonitrilestyrene copolymer/polycarbonate (SAN/PC). The viscosity was measured against the shear rate up to 107 s−1.

The first non‐Newtonian region, the second Newtonian region and second non‐Newtonian region were observed in the compound system. The occurrence of these regions are very similar to those in the parent polymers, SAN and PC. For the calculation of the viscosity‐shear rate curve, a concentric multilayer model was proposed. It gives good agreement between the calculated value and the measured one. A new mechanism for the occurrence of the non‐Newtonian, second Newtonian, and second non‐Newtonian regions was proposed. Nuclear spin–spin relaxation time measured on SAN, T2, seems to be consistent with the consideration that the occurrence of non‐Newtonian region, second Newtonian region, and second non‐Newtonian region are caused, respectively, by the disentanglement, near saturation of disentanglement associated with snapping of macromolecules, and reentanglement through recoiling of snapped macromolecules, and further snapping of the macromolecules, which is inconsistent with the proposed explanation.
A processable prepolymer for the preparation of a stable conductive polymer
Authors: Walton Theodore R.
Published: April 2003

We recently reported1 the synthesis and polymerization of a completely conjugated acetylene terminated prepolymer into an intrinsically conducting organic polymer. Although this polymer exhibited high thermal and environmental stability, its processing window, i.e., the temperature at which it melted vs. the temperature of the highly exothermic cure, was narrow. We now report the synthesis and polymerization of an isomer of this acetylene terminated material. This change in structure resulted in a 63°C decrease in the melting point (87 vs. 150°C) that provides a more than adequate liquid range between melting and the on‐set of curing. Along with the greatly improved processing, this isomer results in an intrinsically conducting, thermally and oxidatively stable polymer equivalent to the original material.
Studies on graft copolymerization of cyclohexyl methacrylate onto 1,2‐polybutadiene
Authors: Liaw Der‐Jang , Lin Lei‐Li
Published: April 2003

The free radical grafting of cyclohexyl methacrylate (CMA) onto 1,2‐polybutadiene (1,2‐PBD) in benzene solution at 60°C was studied. The graft copolymer was characterized by IR, NMR, DSC, and intrinsic viscosity measurements. The polymerization of CMA shows normal kinetic behavior when the PBD concentration is kept below 1.0 monomer mol/L. The rate of grafting was determined at different reaction times, monomer concentrations, initiator concentrations, backbone concentrations, temperatures, and concentrations of the zinc chloride additive. The performance of the graft copolymer used as adhesive was also investigated for bonding of PVC/PVC film.
Simple dilatometer for polymer density and thermal expansivity measurements
Authors: Tyagi O. S. , Deshpande D. D.
Published: April 2003

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).
Design and applications of a solid‐phase oxidizing reagent consisting of a crosslinked polystyrene matrix and a t‐butyl hypochlorite function separated by a trimethylene spacer
Authors: Sreekumar K. , Pillai V. N. Rajasekharan
Published: April 2003

A crosslinked polystyrene–supported solid‐phase analogue of t‐butyl hypochlorite containing a trimethylene spacer group between the polymer matrix and the t‐butyl hypochlorite function was prepared and used as a recyclable oxidizing reagent for alcohols. The synthetic route to this new polymeric reagent involved a seven‐step polymer‐analogous reaction starting from styrene‐divinyl benzene 2%‐crosslinked polymer. A β‐ketopropionic acid function was introduced into the polystyrene matrix by Friedel–Crafts reaction with succinic anhydride. The keto function in the resulting polymer (2) (capacity, 3.57 meq of COCH2CH2COOH/g) was converted to the methylene group by Clemmensen reduction using zinc amalgam and HCl. The carboxyl function in the product polymer (3) was converted to the acylmalonic ester function by malonic ester synthesis through the reaction of the polymeric acid chloride (4) with ethoxymagnesium diethylmalonate. The polymeric acyl malonic ester (5) was decarboxylated to yield the 2‐oxopentyl polystyrene resin (6). This on Grignard reaction with methyl magnesium iodide followed by hydrolysis afforded the polystyrene derivative with the t‐butyl alcohol function separated by three methylene groups (7). The t‐butyl alcohol resin (7) was converted to the corresponding hypochlorite resin (8) by reaction with sodium hypochlorite. The resin was found to have a capacity of 2.84 mmol Cl/g by iodometric analysis. The capacities of the resins 2–8 were determined from the weight changes in the corresponding conversions and verified by quantitative determination of the functional groups. This new hypochlorite was found to oxidize alcohols to carbonyl compounds in 85–98% yield. The oxidizing efficiency of this new reagent was found to be significantly greater than those of the reagents containing only one spacer and no spacer between the reagent function and the polymer support. The presence of a 3‐methylene spacer also facilitated the hypochlorite formation step significantly.
Studies on swelling of cotton fibers in alkali metal hydroxides. I. Influence of variations in fine structure on tensile behavior
Authors: Sreenivasan S. , Iyer P. Bhama , Patel G. S. , Chidambareswaran P. K.
Published: April 2003

A study on cotton fibers swollen slack at ambient temperature in different concentrations of LiOH and KOH indicates that fibers swollen in KOH have higher disorder. Conversion to cellulose II results from swelling in both the reagents, although, with KOH swelling, it begins at a lower concentration. Further, retention of tenacity is higher at all gauge lengths after KOH swelling. Analysis of the influence of fine structure on tensile properties showed some specificity, mainly attributable to cationic size differences of the swelling agents.
Large scale preparation of melamine‐based superplasticizing admixtures. I. Process optimization
Authors: Dairanieh I. S. , Absi‐Halabi M. , Lahalih S. , Al‐Khalid T.
Published: April 2003

The process for preparing novel sulfonated melamine–formaldehyde resins was studied in detail with the objective of optimizing the production cycle time. The effects of minimizing temperature differences between consecutive reaction steps and reducing reaction time of selected steps of the process were assessed. Experimental work focused on increasing the polymerization step temperature and decreasing its time, resulting in considerable savings in the process time and energy consumption. The resin of the optimized cycle was found to have excellent superplasticizing properties when added to concrete mixes.
Synthesis of functional polymers by radiation‐induced grafting of acrolein onto polyethylene film
Authors: Omichi H. , Katakai A. , Okamoto J.
Published: April 2003

Acrolein was grafted onto polyethylene film with radiation energy in order to make functional polymers containing hydrazone, oxime, and oxyacid. The kinetic analysis of the grafting reaction revealed that the irradiation dose affected not only the initiation but also the propagation and termination steps. The activation energies were 12.5 kcal/mol for propagation and 23.3 kcal/mol for termination, respectively. All the introduced aldehyde groups, free, hydrolyzed, and used for ring formation, participated in the reaction with phenylhydrazine. The conversions of aldehyde group to hydrazone, oxime, and oxyacid were small when the grafting yield of acrolein was high.
Heat‐resistant adhesive resins derived from bismaleimides and bisnadimides containing amide linkages
Authors: Mikroyannidis John A. , Melissaris Anastasios P.
Published: April 2003

A novel class of bismaleimides and bisnadimides containing amide linkages in their backbones were synthesized and characterized. The synthesis of these polymer precursors was carried out by reacting a diamine containing amide linkages with maleic/nadic anhydride. They were alternatively prepared by reacting the monomaleamic/monoadiamic acid of an aromatic diamine (1 mol) with terephthaloyl chloride (0.5 mol) and subsequent cyclodehydration. The latter new preparation method circumvented the hydrogeneration necessary in the first method of synthesis. The monomers were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Differential thermal analysis (DTA) of monomers showed that bisnadimide and bismethylnadimide were polymerized at lower temperatures than the corresponding bismaleimide. Thermogravimetric analysis (TGA) in nitrogen and air atmosphere revealed that all polymers were stable up to 321–363°C. Their char yield at 800°C under anaerobic conditions was 49–67%.
Viscosity–temperature relationships for linear and 12‐arm star polystyrenes in dilute solution
Authors: Liouni Maria , Touloupis Costas , Hadjichristidis Nikos , Mays Jimmy W.
Published: April 2003

The actual viscosities (cP) of dilute solutions of linear and 12‐arm star polystyrenes were measured in benzene, a good solvent, and cyclohexane, a poor to moderate solvent, as a function of temperature. The equations of Moore, previously established for solutions of linear polymers, were also found to be valid for star polystyrenes. A branching parameter b was defined which is essentially the same as g′ = [η]br/[η]1. The values of b found in benzene are close to the value of g′ for 12‐arm star polystyrene in toluene, another thermodynamically good solvent. It thus appears that Moore's relationships have at least limited utility in studying branching in polymers.
Polystyrene–polyisobutylene network composites from in situ polymerizations
Authors: Fu F.‐S. , Mark J. E.
Published: April 2003

Crosslinked networks of butyl rubber [polyisobutylene (PIB) with 2 mol % unsaturation] were swelled with various amounts of styrene containing 0.25–4.6 wt % benzoyl peroxide as initiator. Polymerization of the styrene in situ, by increase in temperature, gave novel elastomeric composites. Scanning electron micrographs suggest phase separation which is locked in at the microscopic level, with no evidence for the particulate domains seen in the similarly prepared polystyrene‐polydimethylsiloxane system. The wt % polystyrene (PS) extractible increased with increase in initiator concentration, which is consistent with decrease in the lengths of the PS chains being formed and grafted onto the PIB. Mechanical properties obtained in continuous extension showed maxima in their dependence on composition. Specifically, the ultimate strength (f/A*)m, maximum extensibility εr, energy Er required for rupture, and permanent set ΔL/L0 generally showed maxima in the vicinity of 50 wt % PS. The shortest‐chain PS samples generally showed the largest values of (f/A*)m, εr, and Er, and the smallest values of ΔL/L0.
Sulfonated polyisobutylene telechelic ionomers. XIII. Viscosity behavior in nonpolar solvents and nonpolar–polar solvent mixtures
Authors: Tant Martin R. , Wilkes Garth L. , Kennedy Joseph P.
Published: April 2003

The effect of molecular variables upon the dilute solution viscosity of sulfonated polyisobutylene telechelic ionomers has been studied in both nonpolar solvents and nonpolar–polar solvent mixtures. In nonpolar solvents, association of the terminal salt groups results in an increase in viscosity and gelation at very low concentrations. The concentration at which gelation occurs was found to be dependent upon molecular variables such as architecture, molecular weight, neutralizing cation, extent of neutralization, and the type of solvent. Addition of a small amount of a more polar cosolvent tends to break up ionic associations between polymer chains and thus reduces viscosity. Finally, such solutions with a small amount of polar cosolvent may display dramatic increases in viscosity with increasing temperature due to a dynamic equilibrium between the ionic groups on the polymer chain, the nonpolar solvent, and the polar cosolvent. The results of this work suggest that these ionomers may potentially be useful as viscosity modifiers or “thermal thickeners” in some applications.
Surface morphology and crystalline orientation of uniaxially drawn polytetrafluoroethylene films
Authors: Hashida Shigesou , Namio Hitoshi , Hirakawa Susumu
Published: April 2003

For polytetrafluoroethylene (PTFE) films drawn uniaxially at 100, 150, 250, and 350°C, the morphology and degree of crystalline orientation were investigated by electron scanning microscopy and wide‐angle X‐ray diffraction, respectively. On the surface of the PTFE films which were heat‐treated at 350°C for 2 h before the drawing, granules with a diameter of about 2 μm and bands with a width of about 0.3 μm were observed. By the drawing below the melting point, the bands are transformed into fibrils and a porous structure is formed by the drawing above the draw ratio (λ) of about 1.3. By drawing above the melting point, striations appear perpendicularly to the draw direction, and the collapse of the granules is observed. The orientation of the crystallites increases rapidly with increasing the draw ratio and approaches a plateau at λ ≈ 1.5 for the films drawn above the melting point and at λ ≈ 2.0 for that below it.
Synthesis, characterization, and utilization of methacrylic esters of polyhydric alcohols
Authors: Shantha K. L. , Krishnamurti N.
Published: April 2003

Dimethacrylic esters of di‐, tri‐, and tetraethylene glycols; trimethacrylic ester of trimethylolpropane and tetramethacrylic ester of pentaerythritol were prepared by a commercially viable process in high yields and purity. These methacrylic esters were systematically characterized by infrared, 1H and 13C nuclear magnetic resonance and mass spectroscopic methods. Anaerobic adhesive compositions were made based on each monomer, and their torque strengths were compared.
Theory of tack of pressure‐sensitive adhesive. II
Authors: Mizumachi Hiroshi , Hatano Yasunori
Published: April 2003

When a cylinder is pulled on a pressure‐sensitive adhesive, the bonding and debonding processes proceed simultaneously within the surface of contact. In the previous paper, the theory of rolling friction coefficient of pressure‐sensitive adhesives was proposed for the case where bonding occurs instantaneously. The theory is modified in this paper so as to include both the time‐dependent bonding process and debonding process at the same time. Effect of fiber‐forming on rolling friction is also examined. It is ascertained that the modified theory reproduces quite well the experimentally observed features of the curves of rolling friction coefficient against velocity.
Polyethylene adhesion: Pretreatment with potassium permanganate
Authors: Costa Ricardo Aurélio Da , Gonçalves Maria Do Carmo , Oliveira Marcelo Ganzarolli De , Rubira Adley Forti , Galembeck Fernando
Published: April 2003

Two major events occur in the modification of polyethylene (PE) surfaces by treatment with acidic KMnO4 solutions: The polymer surface is coated with a porous MnO2 layer and corroded, by oxidation. In both cases the resulting surfaces may be bonded with epoxy; the average peeling force for LDPE/epoxy/LDPE adhesive joints thus obtained may reach > 1.6 kN m−1 and is limited by adherend cohesive failure. Modified LDPE surfaces and disassembled joints were examined by transmission and ATR‐IR spectrophotometry, to show that corroded, nonwettable LDPE contains appreciable amounts of polar groups, reactive towards epoxy amine components.
An analytical solution of the molecular weight distribution of reversible step growth polymerization in homogeneous continuous flow stirred tank reactors
Authors: Khanna Ashok , Kumar Anil
Published: April 2003

Mole balance for the molecular weight distribution in homogeneous continuos‐flow stirred tank reactors (HCSTRs) for reversible step‐growth polymerization has been written. The relation for the moment generating function G is found to be a nonlinear ordinary differential equation and has been solved analytically. The solution of the MWD of the polymer formed is shown to be valid even if the condensation product is removed. At equilibrium, the solution reduces to the Flory distribution. The computations show that the polydispersity of the polymer first increases with the residence time θ of the reactor, but, for large θ, it reduces to the equilibrium value after undergoing a maximum.
Measurement of diffusion of antioxidants in isotactic polypropylene by isothermal differential thermal analysis
Authors: Schwarz T. , Steiner G. , Koppelmann J.
Published: April 2003

The diffusion of the phenolic antioxidant 1,3,5‐tris(3,5‐di tert‐butyl‐4‐hydroxybenzyl)mesitylene (IRGANOX 1330) in extruded sheets of isotactic polypropylene (iPP) was investigated over the temperature range from 80 to 120°C by isothermal differential thermal analysis (DTA). The measurements showed a clear relation between oxidation induction time and oxidation maximum time (both determined by isothermal DTA) and the concentration of the stablizer. It was possible to calculate the diffusion coefficients and the activation energy of diffusion of IRGANOX 1330 in iPP by measuring the oxidation maximum times across stacks of isotactic polypropylene sheets.
Etching of plasma‐polymerized tetrafluoroethylene, polytetrafluoroethylene, and sputtered polytetrafluoroethylene induced by atomic oxygen [O(3P)]
Authors: Wydeven Theodore , Golub Morton A. , Lerner Narcinda R.
Published: April 2003

A study was carried out of the surface recession (etching) of thin films of plasma‐polymerized tetrafluoroethylene (PPTFE), polytetrafluoroethylene (PTFE), and ion‐beam sputter‐deposited polytetrafluoroethylene (SPTFE), exposed to atomic oxygen [O(3P)] downstream from a nonequilibrium radio‐frequency O2 plasma. At 22°C, the etch rates for PTFE, SPTFE, and PPTFE were in the ratio of 8.7 : 1.0. A thin, conformal coating of PPTFE (etch rate of 0.3 nm/h at 22°C) was found to protect an underlying, cast film of a reactive polymer, cis‐1,4‐polybutadiene (etch rate of 0.13 mg/cm2 h ≡ 1300 nm/h at 22°C), against O(3P) attack for the time required to fully etch away the PPTFE coating. From ESCA analysis, PTFE exhibited only minor surface oxidation (uptake of 0.5 atom % O) upon etching, its F/C ratio decreasing slightly from 2.00 to 1.97; PPTFE exhibited considerable surface oxidation (uptake of 5.9 atom % O) and a decrease in F/C ratio from 1.30 to 1.23; and SPTFE exhibited a surface oxidation (uptake of 2.2 atom % O) intermediate between those of PTFE and PPTFE, with a decrease in F/C ratio from 1.73 to 1.67. The O(3P)‐induced etching of PTFE had an activation energy of 3.8 Kcal/mol, but no activation energy value was obtained for PPTFE which gave a nonlinear Arrhenius plot apparently because of thermally induced thinning above 50°C.
Simultaneous sorption and diffusion of a 4‐aminoazobenzene derivative and its conjugate acid in cellulose membrane carrying sulfonic acid groups
Authors: Shibusawa Takao , Weber Ruth , Rys Paul
Published: April 2003

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 (DN) and the cationic dye (DC) in the membranes were estimated from the permeation data of the dyes through the membrane. Both DN and DC decrease with increasing SAG. The ratio DN/DC ranged in 2.2–10, the ratio increases with the SAG.
A study of inverse relaxation in some textile fibers
Authors: Nachane R. P. , Hussain G. F. S. , Patel G. S. , Iyer K. R. Krishna
Published: April 2003

This article discusses the phenomenon of inverse relaxation in some textile fibers, namely cotton, ramie, wool, polyester, and viscose. If anextended viscoelastic specimen is allowed to recover a part of the deformation given to it, such that its tension has not become zero, the stress in it tends to increase. This phenomenon is termed as “inverse relaxation.” This property is measured in terms of an index referred to as the inverse relaxation index. The values of this index at various extension and retraction levels for the above materials are presented and discussed in this article.
Decrystallization and acetylation and benzoylation of cotton fibers
Authors: Subramaniam V. , Vasugi N.
Published: April 2003

The general effects of chemical modification such as acetylation and benzoylation on cotton yarns and fabrics are described and it is demonstrated that the physical properties of yarns and fabrics in terms of their elongation, moisture regain, friction, abrasion resistance, and recovery are enhanced significantly. Thermal analysis data show that benzoylated sample is the most stable product.
Melting behavior of cis‐polybutadiene crystallized under stress
Authors: De Candia F. , Romano G.
Published: April 2003

Samples of crosslinked cis‐polybutadiene were crystallized at different temperature and drawing degree. The melting behavior of the crystallized samples was analyzed detecting the retractive stress as a function of temperature. The experimental melting data were extrapolated to the equilibrium conditions to obtain the thermodynamic melting temperature as a function of the drawing degree. The extrapolated data were analyzed with different theoretical approaches. Results agree with a model in which chain‐folding and extended‐chain crystallization can coexist, depending on crystallization temperature and drawing degree.
Isocyanate–epoxy reactions in bulk and solution
Authors: Senger J. S. , Yilgor I. , McGrath J. E. , Patsiga R. A.
Published: April 2003

The reaction between diisocyanates and diepoxides can produce polyoxazolidones. However, the reaction may be accompanied by concurrent cyclization of isocyanate to produce trimeric isocyanurate. Studies were performed with pure phenyl isocyanate or diphenylmethane‐4,4′‐diisocyanate (MDI) and the diglycidyl ether of bisphenol‐A (DGEBA). Reactions were followed by FT‐IR and differential scanning calorimetry in order to determine relative rates of conversion to polyoxazolidone and isocyanurate. Various catalysts were utilized, with the most effective being 2‐ethyl‐4‐methylimidazole (EMI). Bulk reactions between MDI and DGEBA at 150°C resulted in considerable amounts of trimerization, thus giving crosslinked polymers. Solution reactions at 180–185°C in dry N‐methylpyrrolidone using 0.1% EMI gave soluble and moldable polyoxazolidones.
Compositional analysis and infrared spectra of styrene–methyl methacrylate random copolymers
Authors: Mori Sadao
Published: April 2003

Compositional analysis of styrene–methyl methacrylate random copolymers by UV spectrophotometry at 260 nm, proton‐NMR, and IR at 1730 cm−1 have been accomplished and agreement between these three independent methods was excellent. IR spectra of the copolymers in the region of 1100 and 1300 cm−1 are mainly characteristic absorption bands for the methyl methacrylate (MMA) component, but not the same for those of MMA homopolymer, that is, the IR spectra of the copolymers were not additive with those of polystyrene and PMMA. Information about the sequence distribution of copolymers of the same composition can be obtained by comparing the wavenumbers and absorption coefficients of the IR spectra in the region of 1100–1300 cm−1
Fourier transform infrared analysis of plasma‐polymerized hexamethyldisiloxane
Authors: Krishnamurthy V. , Kamel Ihab L. , Wei Yen
Published: April 2003

The plasma‐induced polymerization of hexamethyldisiloxane onto solid surfaces is studied by FTIR. An inductively coupled RF reactor was used to produce the thin polymer coatings. Analysis of the plasma polymer indicates a long chain polysiloxane structure resulting from the removal of some methyl groups from the monomer structure. Increasing the plasma power level from 30 to 100 W increased the chain length in the resultant polymer as indicated by the widening and splitting of the Si–O stretching absorptions. Thermal aging of the vapor phase polymer at 120°C for 1 h in vacuum and at 410°C for 30 min in a nitrogen atmosphere revealed the removal of some methyl groups from the polymer structure with temperature. TGA runs on the vapor phase polymer at 20°C/min in air showed the polymer retaining almost 65% of its weight at 1000°C. The residue remaining after the TGA run had very little organic content and may represent a glass type silicate network. Wettability values determined on coated glass slides revealed the hydrophobicity of the coatings with water contact angle values > 100°. SEM micrographs showed uniform and featureless coating on glass fibers which was etched by boiling water and was attributed to the loss of vapor phase polymer on the surface.
Thermal properties of drawn polytetrafluoroethylene
Authors: Grebowicz J. , Pan R. , Wunderlich B.
Published: April 2003

Polytetrafluoroethylene as polymerized (virgin) was drawn, sintered, and annealed. By thermal analysis the changes in crystal type and crystallinity and melting kinetics was analyzed. It is shown that this analysis permits control and optimization of the various processes. In addition, a new, high melting polytetrafluoroethylene (654 K) is described. It is assumed to be metastable due to strain in the surrounding amorphous fraction.
Polymerization of methane
Authors: Sharma Ashok K. , Yasuda H.
Published: April 2003

Plasma polymerization of methane in a magnetically enhanced capacitively coupled bell jar reactor operating at a frequency of 10 kHz is reported. Dependence of polymer deposition rate on monomer feed rate (F), composite power parameter (W/FM), electrode temperature, and electrode cleanliness have been examined. Such functional properties as wettability, adhesion, and thermal stability of the polymer are found to depend on the composite power parameter (W/FM) of the plasma. The permeability studies indicate highly crosslinked nature of the polymer. ESCA studies reveal codeposition of electrode material with the polymer under high W/FM conditions, potential applications of plasma polymer of methane are suggested.
Effect of polypropylene morphology on thermal cis‐trans isomerization and photofading of some azo dyes: A kinetic study
Authors: Beltrame Pier Luigi , Paglia Ernestina Dubini , Marcandalli Bruno , Seves Alberto
Published: April 2003

Five polypropylene films were prepared having different crystallinity and morphology, the latter having been modified by stretching. They were colored with azo dyes XC6H4NNC6H4N(C2H5)2 (where XH, OCH3, CN, and NO2). The kinetics of the thermal cis‐trans isomerization of these dyes has been studied in the range 21–41°C, much above the glass transition temperature of the polymer. The isomerization process was found to be strictly first‐order; the kinetic parameter values have been correlated with the free volume extent in the amorphous regions of the matrix. Lightfastness of the dyes in the polymer matrices has been also investigated: It appeared to be more important for the unoriented samples with respect to the stretched ones and substantially independent on the crystalinity degree.
Torsional braid analysis and gelation in thermoset resins
Authors: Stutz H. , Mertes J.
Published: April 2003

The origin of the two damping maxima observed during curing of thermoset resins by torsional braid analysis has been studied using a standard epoxy resin. The first peak is not caused by gelation of the resin, but is due to certain flow phenomena prior to gelation. This first peak always occurs at approximately the same viscosity and is observed only when a fiber braid is used as support. It is therefore, in principle, not possible to detect gelation by torsional braid analysis. The second (vitrification) peak is correct, but it is indicated somewhat too early.
Internal stress in epoxide resin networks containing biphenyl structure
Authors: Ochi Mitsukazu , Yamashita Kiichi , Yoshizumi Makoto , Shimbo Masaki
Published: April 2003

Bisphenol‐A type and biphenyl type epoxide resins were cured with two types of aromatic diamines which have or do not have the carbon bridge between aromatic rings. Internal stress of these cured resins decreased with the introduction of a biphenyl structure into the networks. This reduction of the internal stress is attributed to the decrease of the elastic modulus in the glassy region caused by the low mobility of the biphenyl segment. On the other hand, the glass transition temperature increased with increasing the concentration of the biphenyl unit in the networks. These results revealed that the consistency of the decrease of the internal stress with the improvement of the heat resistance of the cured systems is possible by introducing the biphenyl structure to the epoxide resin networks.
Kinetics of radiation‐induced graft copolymerization of 2‐hydroxyethyl methacrylate onto polyethylene membranes
Authors: Yue‐E Fang , Tianyi Shi , Wenfeng Wang , Fang Shi
Published: April 2003

The kinetics of radiation‐induced graft copolymerization of 2‐hydroxyethyl methacrylate onto polyethylene membranes in ethanol has been studied with radiation sources of cobalt‐60. The influences of concentration of monomer, dose rate, and temperature on grafting rate were investigated. The results show the following functional relationship equations: dG0/dt ∝ [M]0 and dG0dt ∝ Ḋ1/2. The apparent activation energy and the collision frequency factor of the grafting copolymerization are 8.0 kcal/mol and 1.505 × 107 G% h−1/2 Mrad−1/2 mol−1 L, respectively. The work established that the relationship of the grafting rate constant k with the temperature relational expression at arbitrary temperature: in k = 16.5269 − 4026(1/T).
The xanthate method of grafting. XII. Effect of operating conditions on the grafting of vinyl monomers onto wood pulp
Authors: Daneault Claude , Kokta Bohuslav V. , Maldas Debesh
Published: April 2003

The present paper examines the influence of various reaction parameters (e.g., pH, type, and concentration of peroxide, reaction time, oxygen as well as reaction medium) on the graft copolymerization of methacrylic acid, butyl methacrylate, epoxypropyl acrylate, and epoxypropyl methacrylate onto chemithermomechanical pulps, initiated by the xanthate method. The optimum concentration of H2O2 changes with the monomer used. Among the peroxides investigated, H2O2 offered the best performance. Oxygen and organic solvents, e.g., acetone and vegetable oil, inhabited grafting reaction. In addition, epoxy monomers showed better results compared to other monomers; this may be due to the participation of epoxy groups in the polymerization reaction
Sequential vapor sorption of additional penetrants in preswollen polymers
Authors: Bontoux Laurent G. , Soane David S.
Published: April 2003

Uptake and removal of a second penetrant in polymer samples preexposed to another vapor dictate many industrially important processes. Both the kinetics and equilibrium sorption can be strongly affected by the presence of the first permeant in the polymeric matrices. A novel experimental setup was constructed to study penetrant uptake in sequence. Sorption of the second vapor took place while the partial vapor pressure of the first vapor was maintained, so that diffusion into the preswollen polymer approximated transport in a pseudobinary system. Polybutylene was chosen in this work to illustrate the capability of this versatile experimental system. Both the rate of diffusion and equilibrium sorption of the second vapor were found to depend on the prevailing composition of the preswollen polymer for all penetrant pairs studied.
The effect of the soft segment of polyurethane on copolymer‐type polyacetal/polyurethane blends
Authors: Chiang Wen‐Yen , Huang Chi‐Yuan
Published: April 2003

Mechanical blends of copolymer‐type polyacetal (POM) with ester‐based and ether‐based polyurethane (PU) are immiscible over the 0–50% PU compositional range. The PU elastomer was added to the rigid POM matrix to increase its toughness. The mechanical, physical, thermal, dielectric, and dynamic mechanical properties and morphology of POM/PU blends were investigated. The notched Izod‐impact strength of blends reaches a maximum at 10 wt % PU. The tensile strength, Young's modulus, volume resistivity, crystallinity, and density decrease with increasing concentration of PU. The elongation of blends reaches a maximum at 20 wt % PU. The dielectric constant and dissipation factor increase with increasing PU content. From dynamic mechanical measurements, as the elastomer content increases, the height of the damping peak also increases, but there is no transition temperature shift. SEM shows that the blends exhibit a continuous morphology with domain size varying from 1 to 10 μm for PU. However, at a concentration of 50 wt % PU, the dispersed PU particles tend to aggregate. Characterization of morphology by a metallurgical microscope has shown that the crystalline materials in the pure POM and the blends exist in a spherulitic superstructure.
The selective sorption of D,L‐amino acids by chemically modified chitosan gels and its application to liquid chromatography
Authors: Seo Toshihiro , Gan Yoke Ai , Kanbara Takaki , Iijima Toshiro
Published: April 2003

The sorption of D,L‐amino acids, DNP‐L‐amino acids and dipeptides by N‐octanoyl‐ and N‐benzoyl‐chitosan gels was investigated under various conditions. The results indicate that optical resolution of D,L‐amino acids by liquid column chromatography has been achieved, using the chemically modified chitosan gels as a stationary phase.
Fourier transform infrared and high‐resolution solid‐state carbon‐13 NMR spectroscopic characterization of cured polystyrylpyridine resins
Authors: Menif R. , Jasse B. , Laupretre F. , Bloch B.
Published: April 2003

Interesting crosslinked materials possessing good mechanical and thermal properties are obtained by condensation of 2,4,6‐trimethylpyridine (collidine) with terephthalic aldehyde in the presence of an acidic catalyst. Fourier transform infrared spectroscopy has been used to follow the kinetics of the chemical reactions involved in the formation of the tridimensional network using aldehyde and ethylene absorption bands. The first steps of the reaction consist in the addition of aldehyde groups on the methyl groups of collidine followed by a dehydration reaction which leads to the formation of ethylenic functions. Crosslinking is obtained by an addition reaction of the methyl groups of collidine on the double bonds created in the first processes. These reactions are strongly dependent on the reaction temperature. Cured resins prepared with different acidic catalysts have been studied by carbon‐13 NMR. p‐Toluene sulfonic acid leads to residual aldehyde groups in the cured resins whereas no residual aldehyde groups are observed after a relatively short curing time when sulfuric acid is used as the catalyst. The networks created in the two cases are not equivalent and present different mechanical properties.
Crosslinking structure of keratin. I. Determination of the number of crosslinks in hair and wool keratins from mechanical properties of the swollen fiber
Authors: Arai Kozo , Sasaki Naokazu , Naito Sachio , Takahashi Toshie
Published: April 2003

Hair and wool keratin fibers which had been treated with an 11 M LiBr solution containing N‐ethyl maleimide showed typical rubberlike elasticity in a solution composed of equal volume of 8 M LiBr and diethylene glycol mono‐n‐butyl ether. Stress–strain curves and equilibrium force–temperature relations were measured for swollen hair and wool fibers. The non‐Gaussian effects on deformation and the energy component in retractive forces were analyzed. On the basis of rubber elasticity theory, a method for estimation of the number of mechanically effective crosslinks in keratin fibers was proposed. A linear relationship between the crosslink density and the disulfide content was obtained from the data for a variety of keratin fibers (i.e., two different human hairs, horse hair, and 17 different wools). From the results of thermodynamical and non‐Gaussian treatments for swollen keratin, it was suggested that the swollen fiber consists of a two‐phase structure: a mechanically stable phase of higher crosslinked domains and rubbery phase with lower crosslink density. It was further found that considerable amounts of nondisulfide covalent crosslinks are present in wool and hair keratins.
The compatibility of a polymer catalyst–substrate–solvent and its reaction rate. I
Authors: Jiadong Hua , Ruofeng Wu , Lu Liu , Peirong Yu
Published: April 2003

An attempt was made which expressed in a compatibility rule not only the polymer effect but the solvent effect in a given polymeric catalyst system. Here the compatibility refers to interaction energy effects among the polymer backbone, substrate, and solvent, which can be measured by chesive energy density or the solubility parameter. A polymer catalyst adopted here is poly(diethylaminoethyl acrylate)–palladium ion complex. The experiments showed that the activity of the polymer catalyst had a bell‐shaped solubility parameter profile and an optimum solubility parameter value for some substrates, and had an inverse bell‐shaped solubility parameter profile and a minimum solubility parameter value for some solvents. Perhaps these results might be utilized to design a polymer catalyst having high activity for a given substrate.
Internal mixer studies of poly(vinyl chloride)/epoxidized natural rubber blends
Authors: Nasir Zainal A. , Ratnam Chantera T.
Published: April 2003

Blends of polyvinyl chloride/epoxidized natural rubber (PVC/ENR) blends were studied. Their rheological properties were studied with a Brabrender Plasticorder. It was found that the rheological properties of any PVC/ENR blends are governed by their blending conditions. To ensure homogenous PVC/ENR blends, adequate and suitable blending conditions must be utilized. PVC thermoplastics phases enhances rigidity while ENR rubbery phases imparts flexibility and processability to the blends. With premixing, Ba/Cd/Zn‐based PVC stabilizer is effective in stabilizing the PVC/ENR blends. Their properties are further enhanced by the addition of curatives.
Preparation and properties of cationic membranes obtained by radiation grafting of methacrylic acid onto PTFE films
Authors: Hegazy El‐Sayed A. , Taher N. H. , Kamal H.
Published: April 2003

Cationic membranes were prepared by direct radiation grafting of methacrylic acid (MAA) onto poly(tetrafluoroethylene) (PTFE) films followed by alkaline treatment to confer ionic character in the graft copolymer. The complete inhibition of homopolymerization of MAA by using ammonium ferreous sulfate (Mohr's salt) failed. However, the addition of 0.5 wt % FeCl3 to the monomer solution effectively inhibited the homopolymerization process and higher grafting yield was obtained. It was found that the graft polymerization proceeded successfully in presence of methanol/water mixture (30/70 wt %), and much higher degrees of grafting were obtained as compared with those in the presence of other diluents used here. The influence of irradiation atmosphere (air, N2 gas, and vacuum) on the grafting process was investigated. The dependence of the grafting rate on MAA concentration was found to be of orders 2.9 and 0.72 in the presence of 0.5 wt % Mohr's salt or 0.5 wt % FeCl3, respectively. This grafting system proceeds by the front mechanism. Investigation of mechanical properties, electrical conductivity, and swelling behavior of the grafted films revealed that such a copolymer could be acceptable in practical use as a cation‐exchange membrane.