bluuebunny/crossref_metadata_2025 huggingface dataset:
Miscibility, crystallization, and melting of the blends of a ferroelectric VDF/TrFE copolymer and PMMA
Authors: Kim Kap Jin , Kim Gwan Bum , Han Seung Hwa
Published: April 2003

Factor analysis by IR and melting‐point depression indicated miscibility between poly (vinylidene fluoride/trifluoroethylene) [P (VDF/TrFE)] and poly (methyl methacrylate) (PMMA) in the melt state. χ12 was found to be −0.229 at 160°C. PMMA reduced the rate of crystallization of P (VDF/TrFE) drastically by increasing both ΔG* and ΔGη. The double melting of the blend crystallized nonisothermally originated from the presence of two morphologically different crystals in the paraelectric crystalline state. © 1993 John Wiley & Sons, Inc.
Improved interaction effected by maleic anhydride‐grafted polypropylene in PRP triblock polymer–EVA blend
Authors: Hudec Ivan , Sain M. M. , Šúňová Véra
Published: April 2003

The role of anhydride‐grafted polypropylene in the ethylene–propylene triblock polymer and ethylene–vinyl acetate copolymer blend has been studied. Maleic anhydride grafted onto polypropylene interacts with polymer components in the blend and also improves the dispersion of the rubber phase in the plastic matrix. Improved interaction is reflected in the ultimate properties of the blend. Blends with good impact resistance and low‐temperature brittleness may be obtained by optimizing the modifier concentration. Composition with good low‐temperature brittleness is achieved by lowering the glass transition temperature of the plastic phase by adding a low concentration of modifier. Impact strength of the studied blend does not depend only on the reactive maleic anhydride content but also on the type of modifier. Generally, an increase in interfacial surface area improves impact strength. © 1993 John Wiley & Sons, Inc.
Structure of toluene sulfonamide formal resins: Molecular models from mechanistic schemes and analytical results
Authors: Chiva V. , Lecacheur M. , Faure R. , Gallo R. , Wimmer E.
Published: April 2003

Toluene Sulfonamide Formaldehyde Resins (TSFR), having elemental analysis close to (C8H9NSO2)n, are shown by GPC to exist as a mixture of a few (5 to 6) oligomers, having masses between 400 and 1900 g. A complete scheme of all the possible intermediates involved in their preparation is derived from the results of synthesis and from mechanistic steps; this allows one to propose the structure of oligomers having end groups OH and NH. IR, 1H NMR, and 13C NMR data on oligomers, compared to those of authentic samples specially designed and prepared, agree with the structures proposed. These results are helpful in designing modified or new resins to be used in nail lacquers. © 1993 John Wiley & Sons, Inc.
Flow behavior of symmetrical P (S‐b‐MMA) block copolymers: Rheological problems arising from shear modified morphology
Authors: Braun H. , Gleinser W. , Cantow H.‐J.
Published: April 2003

In this article, symmetrical, narrow distribution P (S‐b‐MMA) block copolymers are characterized rheologically, using a dynamic spectrometer and a stress rheometer. The shear induced morphology changes are investigated by off‐line electron microscopy and SAXS. We tried to correlate the results of dynamics and long‐time creep experiments with morphological and rheological features. Summarizing, one can point out that the examined block copolymers reveal the well‐known low frequency behavior of phase separated blends. Additionally, we observed a significant shear influence on the morphology, i.e. a shear induced structuring and alignment of lamellae. This considerable change in morphology is also reflected by the characteristic rheological properties (retardation time, yield stress). Therefore, problems concerning the validity range of linear viscoelastic behavior arise, which are discussed in brief. © 1993 John Wiley & Sons, Inc.
Preparation of polyimide composite membrane by chemical vapor deposition and polymerization technique (CVDP)
Authors: Yanagishita H. , Nakane T. , Nozoye H. , Yoshitome H.
Published: April 2003

A dry process of chemical vapor deposition and polymerization (CVDP) was employed to prepare a polyimide composite membrane for water–ethanol separation, using an apparatus newly developed for this investigation. The characteristics of the apparatus were studied by depositing pyromellitic dianhydride (PMDA) and 4,4′‐diaminodiphenyl ether (P,P′‐oxydianiline, ODA) in a vacuum of 10−6 Torr. Deposited layers were converted to a thin polyimide film by heating at 200°C for 3 h in a vacuum. The composite membranes were prepared by forming a polyimide layer of 0.2 μm thickness on the surface of asymmetric supporting membranes made by the phase‐inversion process. The polyimide composite membranes prepared under the best conditions exhibited a separation factor α (H2O/EtOH) of over 140 for 95 vol% aqueous ethanol solution with flux of 0.1 kg/m2 h at 25°C in pervaporation mode. Also, it was demonstrated that this new technique of chemical vapor deposition and polymerization (CVDP) was very useful for the preparation of a solvent‐resistant composite membrane in a completely dry process. © 1993 John Wiley & Sons, Inc.
Changes in physical properties of methacrylonitrile (MAN)‐grafted silk fibers
Authors: Tsukada Masuhiro , Freddi Giuliano , Shiozaki Hideki , Pusch Noriko
Published: April 2003

Changes in physical properties of silk fibers, grafted with methacrylonitrile (MAN), were investigated as a function of the weight gain. The weight gain increased steadily during the first 60 min of reaction and gradually attained an equilibrium value (60%) after about 4 h. The initial tensile resistance of silk fibers decreased by MAN grafting. The crystalline structure of silk fibers remained unchanged, regardless of MAN grafting, however. a minor and broad peak appeared in the X‐ray diffraction curves of MAN‐grafted silk fibers with a weight gain of 60%, corresponding to the unoriented MAN polymer attached inside the fibers. Molecular orientation of silk fibroin chains in the crystalline regions, evaluated from X‐ray diffraction curves, did not change significantly, while both birefringence and isotropic refractive index decreased as the weight gain increased, implying that MAN polymer attached preferentially to the amorphous and not to the crystalline regions. Dynamic vis‐coelastic measurements showed that the position at which the E′ value began to decrease shifted to a lower temperature as the weight gain increased. These findings suggest that the thermal movement of silk fibroin molecules was accelerated by the presence of the poly‐MAN chains attached to the amorphous regions of silk fibroin fibers. © 1993 John Wiley & Sons, Inc.
Strain‐Coupling effects in extensional flows
Authors: Vrentas J. S. , Vrentas C. M.
Published: April 2003

A recently developed strain‐coupling constitutive equation for nonlinear viscoelasticity is used to analyze extensional flows. Comparisons are presented between the predictions of the theory and experiment for equibiaxial‐ and uniaxial‐step strain‐stress relaxation experiments. © 1993 John Wiley & Sons, Inc.
Thermal degradation of polydigolphosphate
Authors: Basu Sudhapada , Chatterjee Nandini , Maiti Mrinal M.
Published: April 2003

A new inherently cross‐linked polymer, polydigolphosphate, has been synthesized. The polymer has high affinity for moisture and a tendency to retain sodium chloride, which is produced as a coproduct in the synthesis of the polymer. The purity and, hence, the structural identity of the polymer have been established by combined DTA‐TG analyses in an inert atmosphere. Thermal degradation of the polymer has been quantitatively correlated on the basis of a proposed mechanism. The mechanism may serve as a representative one for the degradation of similar polyphosphates of poly(ethylene glycol). © 1993 John Wiley & Sons, Inc.
Isothermal curing of an uncatalyzed dicyanate ester monomer: Kinetics and modeling
Authors: Georjon Olivier , Galy Jocelyne , Pascault Jean‐Pierre
Published: April 2003

The isothermal cure of a dicyanate ester monomer has been studied under different atmospheres (air and argon) without any catalyst, by following the evolutions of both glass transition temperature and conversion. Independently of both atmosphere and temperature of cure, there is a unique one‐to‐one relationship between these two parameters, correctly described by a restated DiBenedetto's equation. The chemical kinetics are satisfactorily modeled with two competing reactions schemes, which are second‐order and second‐order autocatalyzed, the latter displaying more relative importance under air‐curing conditions. Whatever the cure temperature may be, gelation occurs around 0.60 conversion under air, whereas the theoretical xgel = 0.50 is experimentally observed under argon. The time–temperature‐transformation diagrams have been established. © 1993 John Wiley & Sons, Inc.
Phase behaviors and film properties of dispersions and coatings containing associative and conventional thickeners
Authors: Ma Zeying , Lundberg David J. , Roberts Stacy , Glass Edward J.
Published: April 2003

Phase‐separation behaviors of latex dispersions, using commercial latices of three different median sizes, and pigmented coatings are examined. Both the dispersions and pigmented coatings at a 0.32 volume fraction of total dispersed phase were thickened with water‐soluble polymers, with and without surfactant hydrophobes. Latex dispersions thickened with water‐soluble polymers without hydrophobe modification follow the phase‐separation behavior described by the volume restriction flocculation (VRF) concept (i.e., molecular weight of the thickener or particle size of the latex). This is surprising since commercial latices contain a variety of surface‐stabilizing moieties, in addition to surfactant. Latex dispersions thickened with commercial and model hydrophobically modified ethoxylated urethane (HEUR) polymers do not follow the phase‐separation behavior predicted by the VRF concept. The lack of correlation of phase behavior with latex median size in HEUR‐thickened formulations led to an examination of four secondary thickeners, noted for providing high viscosities at low shear rates. With an all‐acrylic, large median‐size latex, the combinations of commercial HEURs with secondary thickeners are effective in eliminating phase separation; only partial reduction in phase separation is observed with a vinyl acetateacrylic large‐particle latex. The influence of HEUR/secondary thickener blends on the film properties also is discussed. © 1993 John Wiley & Sons, Inc.
Thermo‐sensitive swelling behavior in crosslinked N‐isopropylacrylamide networks: Cationic, anionic, and ampholytic hydrogels
Authors: Yu Hua , Grainger David W.
Published: April 2003

Crosslinked polymer networks of N‐isopropylacrylamide (NiPAAm) containing small amounts of either anionic or cationic comonomers, or mixtures of both were fabricated and characterized in terms of their aqueous swelling and critical behavior. These gels demonstrate critical transition temperatures in aqueous media between a highly solvated, swollen gel state and a collapsed, dehydrated network over temperature ranges comparable to that of pure NiPAAm, with modifications of gel critical points and respective temperature ranges dependent upon comonomer type and content. Copolymer gel swelling ratios are significantly larger than those reported for pure homopolymer NiPAAm gels, even when only 0.5 mol % of comonomer is incorporated. At temperatures exceeding the collapse transition point, all copolymer gels collapse to a state of nearly complete dehydration, demonstrating short‐time collapsed‐state swelling ratios far lower than those of pure NiPAAm networks. Collapse kinetics for the ionomeric gels are much more rapid than those of pure NiPAAm, achieving collapse state equilibrium on time scales of seconds. Swelling behavior as a function of pH, buffer type, ionic strength, crosslinking, and temperature is detailed over a range of copolymer compositions. © 1993 John Wiley & Sons, Inc.
Physical properties of silk fibers grafted with a binary mixture of styrene and n‐butyl methacrylate
Authors: Tsukada Masuhiro , Freddi Guiliano , Monti Patrizia , Bertoluzza Alessandro
Published: April 2003

The mechanical and physical properties, as well as the crystalline structure of silk fibers grafted with a binary mixture of styrene (St) and n‐butyl methacrylate (BMA) were studied as a function of the weight gain. The size of the fibers increased linearly with the extent of grafting. The strength, the elongation at break, and the tensile modulus decreased with increasing weight gain, but the breaking load remained almost unchanged. The difference among the tensile properties measured in dry and wet states decreased beyond weight gain of 50% because of the hydrophobic properties of grafted silk fibers. The thermal behavior was determined by differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA) measurements. Silk fibers attained a higher thermal stability as the amount of loaded polymer increased. The thermally induced molecular movement of St/BMA‐grafted silk fibers was enhanced as judged by shifting the onset and the position of the dynamic loss modulus (E″) peak to lower temperature when the weight gain increased. X‐ray diffraction curves demonstrated that the crystalline structure of silk fibers remained unchanged regardless of the St/BMA grafting. © 1993 John Wiley & Sons, Inc.
Polypropylene–Carbon black interaction in conductive composites
Authors: Petrović Zoran S. , Martinović Bratislav , Divjaković Vladimir , Budinski–Simendić Jaroslava
Published: April 2003

Interaction between polypropylene matrix and carbon black was examined by measuring physical, mechanical, and electrical properties. It has been shown that presence of carbon black influences the morphology and crystallinity of the matrix. Strong interaction was observed directly by electron microscopy and indirectly by the rise of the modulus of elasticity. The effect of carbon black on strength and physical properties of the composites is discussed. © 1993 John Wiley & Sons, Inc.
Polymerization of olefins through heterogeneous catalysis. XIII. The influence of comonomer in the solution copolymerization of ethylene
Authors: Jaber Isam A. , Ray W. Harmon
Published: April 2003

The copolymerization of ethylene with highly active TiCl4/MgCl2‐supported catalysts in solution reactors at 185°C and 400 Psig pressure is presented. The performance of these highly active supported catalysts at high reaction temperature is characterized by a high initial rate that decays rapidly within the 10 min polymerization time period. In the presence of hydrogen and a comonomer, catalyst yields up to about 300 kg/g (Ti) are achieved. Kinetic data obtained on the influence of a comonomer, e.g., 1‐octene or 1‐hexene, indicate rate enhancement when used in moderate concentrations. Higher concentrations of comonomer result in a decreasing rate of ethylene consumption. Comonomer/ethylene molar ratios in the range 0–0.827 resulted in comonomer incorporation up to about 2.6 mol % and a small reduction in the polymer molecular weight. © 1993 John Wiley & Sons, Inc.
Interaction of dyes used for foods with food packaging polyamides
Authors: Arvanitoyannis I. , Tsatsaroni E. , Psomiadou E. , Blanshard J. M. V.
Published: April 2003

The effect of pH, temperature, dye concentration, and additives on the adsorption of the dyes FD & C (Food, Drugs & Cosmetics) Blue 1 and Blue 2 upon the polyamides nylon 4–7,9, and 10–12 was studied and a correlation between these parameters and the dye uptake was found. The adsorption kinetics of the dyes on the polyamides were studied and a mechanism based on the interaction of the acid groups of the dyes and the positively charged groups of the polyamides was suggested. © 1993 John Wiley & Sons, Inc.
Vaporization behavior of antioxidant additive BHT in polypropylene by heating
Authors: Hayashi Hiromichi , Matsuzawa Shuji
Published: April 2003

The vaporization behavior by heating of an antioxidant additive 2,6‐di‐tert‐butyl‐p‐cresol (BHT) in polypropylene (PP) was studied. BHT vaporized from PP plates under the stream of air at 70–100°C for 0–3000 min was absorbed to the Tenax GC adsorbent column, and the precentage recoveries of BHT increased linearly with the square root of time: t1/2. There were no considerable differences between the vaporization behavior of BHT by heating under the stream of air and that of nitrogen. BHT does not act as an antioxidant at temperature below 120°C. The percentage recoveries of BHT from PP plates at 90–120°C under a nitrogen stream increased linearly with t1/2 until about 70% of the recovery. At temperature below 80°C, the linear relations still held. The vaporization also proceeded at the temperature below the melting point of BHT. Both the sample thickness and the temperature greatly influenced the vaporization rate of BHT in PP, and the Arrhenius plots of the logarithmus of the specific rate vs. the reciprocal of the absolute temperature at 70–120°C showed an approximately straight line. Triolein coexisted with interrupted BHT vaporization. However, the PP plates containing 0.2 wt % of olive oil showed the same vaporization behavior of BHT as that of the original PP plates free from oils at 80 and 100°C. The decreasing rate of BHT in PP by heating under air obeyed first‐order kinetics. © 1993 John Wiley & Sons, Inc.
Numerical simulation of anomalous penetrant diffusion in polymers
Authors: Wu J. C. , Peppas Nikolaos A.
Published: April 2003

This work introduces a new numerical algorithm that can be used to analyze complex problems of penetrant transport. Penetrant transport in polymers often deviates from the predictions of Fick's law because of the coupling between penetrant diffusion and the polymer mechanical behavior. This phenomenon is particularly important in glassy polymers. This leads to a model consisting of two coupled differential equations for penetrant diffusion and polymer stress relaxation, respectively. If the polymer relaxation is the rate‐limiting step, both the concentration and stress profiles are very steep. A new algorithm based on a finite difference method is proposed to solve the model equations. It features the development of a tridiagonal iterative method to solve the nonlinear finite difference equations obtained from the finite difference approximation of the differential equations. This method was found to be efficient and accurate. Numerical simulation of penetrant diffusion in glassy polymers was performed, showing that the integral sorption Deborah number is a major parameter affecting the transition from Fickian to anomalous diffusion behavior. © 1993 John Wiley & Sons, Inc.
Wood plastic composite using different monomers in presence of additives
Authors: Khan Mubarak A. , Ali K. M. Idriss
Published: April 2003

Wood plastic composites (WPC) are prepared with low density wood simul under Co‐60 gamma radiation using acrylamide (AM), butyl methacrylate (BMA), and styrene (ST) as the bulk monomers at different compositions with methanol used as swelling agent. The effect of additives, e.g., polyfunctional monomers and oligomers, used by 1% v/v or w/v, on the polymer loading and tensile strength of the composites is investigated. Polyfunctional monomers are N‐vinyl pyrrolidone (NVP), tripropylene gylcol diacrylate (TPGDA), and trimethylol propane triacrylate (TMPTA). Oligomer additives are urethane acrylate (UA), epoxy acrylate (EA), and polyester acrylate (PEA). Increased polymer loading (PL) with enhanced tensile strength (TS) are obtained with the composite. Incorporation of a small amount (1% v/v or w/v) of coadditives like sulfuric acid (H+), lithium nitrate (Li+), copper sulfate (Cu2+), and urea (U) into the impregnating solutions containing the additives has significantly influenced the PL and TS values of the WPC. Though the H+ ion has synergistically enhanced the PL, but it has drastically reduced the TS values. Li+ion has played a good role for the replacement of H+ion. Urea has substantially increased the PL values with relatively small enhancement of TS. Cu2+ ions have retained both PL and TS values of the WPC, which could be used as protective and preservative purposes of the composites. © 1993 John Wiley & Sons, Inc.
The influence of chain configuration and, in turn, chain packing on the sorption and transport properties of poly(tert‐butyl acetylene)
Authors: Morisato A. , Miranda N. R. , Freeman B. D. , Hopfenberg H. B. , Costa G. , Grosso A. , Russo S.
Published: April 2003

A series of poly(tert‐butyl acetylene) (PTBA) polymers was prepared with cis contents, as characterized by 13C NMR spectroscopy, ranging from 44% to 100%. The sorption and transport properties of propane in this systematically varied series were determined by a sensitive gravimetric sorption technique. As the cis content of the polymer increased, propane solubility and diffusivity decreased markedly and the d‐spacing, determined by wide angle x‐ray diffraction spectroscopy, decreased monotonically with increasing cis content, suggesting that higher order molecular structure, related explicitly to configurational variations, may strongly influence chain packing in these rigid, glassy materials and, in turn, sorption and transport properties of small molecules in this polymer series. © 1993 John Wiley & Sons, Inc.
On the mechanism of gas transport in rigid polymer membranes
Authors: Hensema E. R. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

Conventional polymers are compared as gas separation membrane materials with “tailormade” polymers. The increased permeability of the latter are due to their higher free volume available for gas transport. The increased free volume is associated with the rigidity polymer backbone. Free volume is obtained by subtracting the occupied volume, calculated using group contributions from the polymer specific volume. Wide Angle X‐ray techniques are used to obtain average d‐spacings that are interpreted in terms of average intermolecular space, and that are related to permeability data. These highly permeable rigid polymer membranes have high glass transition temperatures. The physical parameters, that is, Tg and the jump in heat capacity (ΔCp), are obtained with Differential Scanning Calorimetry, and are used to obtain an estimation of free volume. A good correlation for a series of random copoly[p, m‐phenylene(4‐phenyl)‐1,2,4‐triazoles] is obtained. A relationship between permeability and a free volume term, which can be estimated from thermodynamic properties, is equally valid for a wide variety of conventional polymers. © 1993 John Wiley & Sons, Inc.
Effect of crystallinity on the kinetics of liquid absorption into poly(ethylene terephthalate)
Authors: Popoola Adeola V.
Published: April 2003

Drawn poly(ethylene terephthalate) fibers (D.R. 5 : 1) were treated unrestrained in dimethylformamide and benzaldehyde at 100°C for varying amounts of time. A rapid diffusion of liquids into the polymer occurred, the latter experiencing considerable retention of the absorbed liquids at 60°C. The increase in chain mobility brought about by both the liquids absorbed and the liquid‐induced crystallisation that followed allowed orientation strains existing in the polymer structure to be relieved. This brought about a 20% shrinkage in the polymer and a change in its overall geometry. Subsequently, a sharp drop occurred in the level of liquid retention within the polymer signifying expulsion of liquids from the crystallising domains and ultimately a levelling off (equilibrium) in the weight retention kinetics.

However, precrystallisation of the fibers at 200°C for 3 h using dry hot air prior to liquid treatment study at 100°C and retention at 60°C, led to a linear increase in the amount of liquid retained in the polymer as a function of time until an equilibrium was established. The essential feature of the latter liquid retention kinetic is that a plot of the amount of relative liquid retained, that is Mt/M∞ as a function of square root of time, ($\[ \sqrt t \]$) agrees with Fick's standard diffusion process. © 1993 John Wiley & Sons, Inc.
Method of determination of transient and steady‐state conductivity in polyethylene terephthalate ultrathin films
Authors: Thielen A. , Vanderschueren J. , Niezette J. , Feyder G.
Published: April 2003

The determination of transient and/or steady‐state conductivity of polyethylene terephthalate (PET) ultrathin films by means of electrode configurations involving any load or stress imposed on the measuring area during measurement usually leads to anomalous behaviours of the charging current and thus prevents a good evaluation of the electrical properties of the samples. This can be avoided by the use of a two‐electrode system with lateral contacts, to obtain reproducible results without any requirement for previous mechanical, thermal, or electrical treatments (as is often recommended in the literature), and that permits the characterization of industrial films down to 1.5‐μm thick in true storage conditions after production. © 1993 John Wiley & Sons, Inc.
On the gel effect in the presence of a chain transfer agent in methyl methacrylate polymerization and its copolymerization with various acrylates
Authors: Wang X. , Ruckenstein E.
Published: April 2003

The kinetics of methyl methacrylate (MMA) polymerization, and of its copolymerization with various acrylates, at high conversions in the presence of a chain transfer agent, are investigated with a dilatometer over the entire course of reaction. The displacement to higher conversions of the onset of the gel effect in the MMA homopolymerization, in the presence of a chain transfer agent, was determined. Similar information is also provided for the MMA‐acrylate copolymerization systems. An increase in polymerization temperature slightly delays the onset of the gel effect in the MMA‐acrylate copolymerization, but considerably increases the final conversion. The final conversion in copolymerization for a constant concentration of the chain transfer agent is independent of the initiator concentration, but is a function of the polymerization temperature. The reaction time for reaching the limiting conversion in copolymerization is increased with an increasing amount of the second monomer, as well as with an increasing number of carbon atoms in the acrylate used as the second monomer. © 1993 John Wiley & Sons, Inc.
Functional polymers for colloidal application. VIII. Syntheses of anionic and zwitterionic aniline–formaldehyde condensates and their dispersing ability to zwitterionic clay
Authors: Kuo Ping‐Lin , Wey Bih‐Shiuh
Published: April 2003

Anionic and zwitterionic aniline–formaldehyde condensates have been synthesized by a methylenation under mild reaction conditions and a reaction with propane sultone. The formation of condensates is characterized by NMR, i.e., the peak of methylene at δ = 3.5−4.0 ppm and the peaks of propylsulfonate at δ = 2.7−3.4 ppm and δ = 1.7−2.2 ppm. The results from GPC show that a longer condensation time increases the degree of polymerization of the condensates. The dispersing properties of the condensates are assessed by the viscosity, scanning electron microscopy (SEM), and adsorption behaviors. N,N‐dimethyl‐N‐(3‐propylsulfonate) anilinium–formaldehyde condensates (DPSAF) with higher molecular weight (DPSAF‐H) show significantly lower apparent viscosities. Comparing the results of SEM and the viscosity method, it can be concluded that, under comparable conditions, a suspension with a lower viscosity is more homogeneously dispersed. The amount of DPSAF‐H adsorbed onto clay is significantly higher than that of PSAF‐H at low concentrations of the dispersant and reaches an optimum after ca. 3 wt %. This result is in parallel with the trend of viscosity. The zwittionic DPSAF promotes their dispersing ability of clay in water due to the existence of the positive and negative charges. The decrease in the amount of adsorbed PSAF‐H with increasing pH can be interpreted by the increased negative charge of the clay, as a result of the decreased interaction between the anionic PSAF‐H and the clay. © 1993 John Wiley & Sons, Inc.
Grafting of polyurethane surfaces with poly(ethylene glycol)
Authors: Freij–Larsson Christina , Wesslén Bengt
Published: April 2003

Films of a commercial poly(ether urethane), Pellethane 2363‐80AE, were prepared through solvent casting from dimethyl formamide. The films were grafted with poly(ethylene glycol) (PEG) by a two‐step procedure. In the first step, the film surfaces were treated with hexamethylene diisocyanate in toluene in the presence of triethylamine as a catalyst. In the second step, PEG 1500 was allowed to react in toluene with surface bound isocyanate groups. It was shown by ATR‐IR, XPS, and contact angle measurements that the grafted surfaces were mainly composed of PEG, and that they were strongly hydrophilic. It was also shown that unreacted PEG was entrapped in the material, which influenced its me‐chanical and thermal properties. Extraction of the films with toluene eliminated the entrapped PEG, and the hydrophilicity as well as the PEG coverage of the surface decreased. However, a subsequent treatment with aqueous NaCl solution induced a molecular restructuring of the surface, increasing the amount of grafted PEG at the surface to a value close to the original one. © 1993 John Wiley & Sons, Inc.
Toughening of epoxy resins by modification with dispersed acrylate rubber for electronic packaging
Authors: Ho Tzong‐Hann , Wang Chun‐Szhan
Published: April 2003

Dispersed acrylate rubbers were used to improve the toughness of cresol‐formaldehyde Novolac epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The effect of the alkyl group of the acrylate monomer on the phase separation of resultant elastomers from epoxy resin was investigated. The dispersed acrylate rubbers effectively improve the toughness of cured epoxy resins by reducing the coefficient of thermal expansion (CTE) and flexural modulus, while the glass transition temperature (Tg) was hardly depressed. Electronic devices encapsulated with the dispersed acrylate rubber‐modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended device use life. © 1993 John Wiley & Sons, Inc.
Biocidal polymers active by contact. I. Synthesis of polybutadiene with pendant quaternary ammonium groups
Authors: Hazziza–Laskar J. , Nurdin N. , Helary G. , Sauvet G.
Published: April 2003

Hydroxytelechelic polybutadienes carrying covalently bound quaternary ammonium salts were successfully synthesized in three steps. The first one was the preparation of 1‐(N, N‐dimethylaminopropyl) 1,1,3,3‐tetramethyldisiloxane (M′2A) by hydrosilylation. The addition occurred mainly in the terminal position of the double bond, but isomers were formed in small proportion (an isomer resulting from an inverse addition and an isomer resulting from an isomerization of the double bond). The proportion of these isomers increased with the concentration of catalyst (H2PtCl6). Similar results were obtained with a Pt (0)‐di‐vinyltetramethyldisiloxane complex (Pt,DVDS). The second step was the grafting of M′2A onto the 1,2‐units of a hydroxytelechelic polybutadiene by hydrosilylation. The yield of the reaction was higher than 90% and the OH functionality decreased slightly. Here again, different platinum catalysts were compared: initial rates were higher with Pt,DVDS, but the final yields were better with H2PtCl6. The last step was the quaternization of the pendant tertiary amino groups in methanol with alkyl bromides from C8H17Br to C16H33Br. The yield of the reaction was higher than 90% and the OH functionality was not modified. © 1993 John Wiley & Sons, Inc.
Biocidal polymers active by contact. II. Biological evaluation of polyurethane coatings with pendant quaternary ammonium salts
Authors: Nurdin N. , Helary G. , Sauvet G.
Published: April 2003

Films of polyurethane were prepared by reaction of hydroxytelechelic polybutadienes carrying covalently bound quaternary ammonium salts with an aliphatic triisocyanate. These coatings exhibited high biocidal activity against Gram‐positive and Gram‐negative bacteria, yeasts, and moulds. It was found that many parameters controlled the bioactivity such as the time of contact between films and bacteria, the [NCO]/[OH] ratio used to prepare the cured polyurethane, the concentration of quaternary ammonium salts in the coating, and the length of the alkyl chain from C8 to C16 linked to the quaternary nitrogen atom. A secondary phenomenon of diffusion only observed with the shorter alkyl chains (C8 and C10) was shown to be due to synthesis residues. After these water‐soluble impurities are eliminated, the biocidal activity remains excellent: then it is due only to a contact polymer bacteria. © 1993 John Wiley & Sons, Inc.
Solubility characteristics of poly(4‐methyl‐1‐pentene)
Authors: Beck H. N.
Published: April 2003

Relative solubility determinations in over 50 compounds have identified numerous good solvents as well as nonsolvents for poly(4‐methyl‐1‐pentene) (TPX) at elevated temperatures. The better solvents include hydrocarbons and esters that contain significant amounts of aliphatic or cycloaliphatic character. Equilibrium phase‐transition temperatures for dissolution upon heating and phase separation upon cooling were determined by a hot‐stage light microscopic method. The significance of the results is related to the ability to determine precisely the relative solvent power of different solvents and related to the preparation of permselective membranes from the polymer solutions. © 1993 John Wiley & Sons, Inc.
Study of solution properties of poly(α‐methyl styrene) in various solvents by dilute‐solution viscometry
Authors: Chee K. K. , Ng S. C.
Published: April 2003

The values of Mark–Houwink–Sakurada constants were determined for poly(α‐methyl styrene) (PαMs) of high and low molecular weights in a variety of solvents by a new approach, which requires only polydisperse samples. The results are in accord with those reported in the literature. In addition, the present work reports the values of the Flory interaction parameter for PαMs in 13 solvents of distinct solvent power at various temperatures. Three refined methods pertaining to both polar and nonpolar solvents were applied to estimate the solubility parameter (δ2) of PαMs resulting in δ2 = 18.75 ± 0.15 (J/mL)1/2 at 30°C. Finally, the scatter data of the Huggins coefficient over a range of expansion factors varying from 0.7 to 2.6 seem to conform better to a newly proposed empirical equation than to the contemporary model after Imai. © 1993 John Wiley & Sons, Inc.
Effects of surface roughness and the chemical structure of materials of construction on wall slip behavior of linear low density polyethylene in capillary flow
Authors: Chen Yuhming , Kalyon Dilhan M. , Bayramli Erdal
Published: April 2003

The presence of wall slip during the flow of polymeric melts has significant ramifications on the melts' processability. In this study, the effects of materials of construction and surface roughness on the wall slip behavior of a linear low density polyethylene were investigated, using capillary flow. Capillaries, constructed from copper, stainless steel, aluminum, and glass, were used. The inner surface roughness of the capillaries were characterized by the employment of a profilometer and scanning electron microscopy. The roughness profiles of copper capillaries were also altered by the employment of chemical etching. Using Mooney's analysis, the wall slip velocity values were determined to be in the range of 0.09 to 1.34 mm/s. The wall slip velocity values were the highest for stainless steel and were negligible for aluminum. The relative work of adhesion values of polyethylene were the smallest for stainless steel and copper and the highest for glass. Overall, the wall slip velocity values increased with decreasing surface roughness of the capillaries and with decreasing work of adhesion. © 1993 John Wiley & Sons, Inc.
A kinetic scheme for anhydride curing of diglycidyl ester with tertiary amine as catalyst
Authors: Khanna Umang , Chanda Manas
Published: April 2003

A kinetic model has been developed on the basis of reaction mechanisms proposed for the anhydride curing of diepoxides, using tertiary amine as catalyst. The model has been tested for the cure reaction of a diglycidylester model compound, bis‐(2,3‐epoxypropyl)‐1,3‐benzenedicarboxylate, with hexahydrophthalic anhydride as the curing agent and benzyldimethylamine as the catalyst, over the temperature range 100–120°C, the rate being measured by means of differential scanning calorimetry, using an isothermal approach. The rate expressions derived for the model are half order and first order, with respect to reacted and unreacted functional groups, respectively, in the initial stage. For the later stage of curing, up to the point of vitrification, the model indicates a 1.5 order with respect to the unreacted functional groups. These are in good agreement with the kinetic orders of 0.5 and 1.5, with respect to reacted and unreacted functional groups, respectively, reported earlier from a phenomenological approach for the whole range of curing prior to the onset of vitrification. © 1993 John Wiley & Sons, Inc.
The temperature dependence of the doolittle equation parameter for polymer liquids
Authors: Lee Myung Ho , Han Do Hung , Cho Bongkee
Published: April 2003

The Doolittle equation parameter for polymer liquids is a function of temperature. Its dependence on temperature can be expressed by a quadratic equation. The constants in the equation are determined for four vinyl‐type polymer liquids: polystyrene (PS), poly(vinyl acetate) (PVAc), polydimethylsiloxane (PDMS), and polyisobutylene (PIB). It was found that the Doolittle parameter decreases with increasing temperature. Equations are presented for the pressure and temperature coefficients of viscosity, isoviscous temperature coefficient of volume, and the constant Km in the Miller equation. Comparisons of the predictions of the equations, with those in the literature, are favorable. © 1993 John Wiley & Sons, Inc.
Formation of microporous polymer fibers and oriented fibrils by precipitation with a compressed fluid antisolvent
Authors: Dixon David J. , Johnston Keith P.
Published: April 2003

Polymer morphology is controlled over a continuum from microspheres to interconnected bicontinuous networks to fibers with a versatile new process: precipitation with a compressed fluid antisolvent. The results are explained qualitatively as a function of phase behavior, mass‐transfer pathways, and the formation rates of skin on the flowing jet. By spraying dilute polystyrene in toluene solutions into liquid carbon dioxide, extremely small 100 nm microspheres are formed. For concentrations above the critical composition, fibers are produced that are not only microcellular, but, in some instances, even hollow. Mass‐transfer pathways that cross the binodal near the critical composition produce interconnected networks, likely due to spinodal decomposition. In this region, fibers composed of highly oriented microfibrils are produced at high shear rates. Preaddition of CO2 influences the morphology because of dilution, in a similar manner as a liquid antisolvent, except that the viscosity reduction is larger due to added free volume. Because CO2 diffuses through the glassy polystyrene skin faster than does a conventional liquid antisolvent such as methanol, it produces more porous fibers, which are also more cylindrical. © 1993 John Wiley & Sons, Inc.
Further studies on biodegradation of aliphatic poly(ester‐amides)
Authors: Chen X. , Gonsalves K. E. , Cameron J. A.
Published: April 2003

Two types of aliphatic poly(ester‐amides) (PEAs) were subjected to microbial degradation in basal mineral salt broth, under the attack of a yeast, Cryptococcus laurentii, at 20°C. PEA‐I copolymers were made by the anionic ring‐opening copolymerization of ϵ‐caprolactone and ϵ‐caprolactam, whereas PEA‐II copolymers were synthesized by a two‐step polycondensation reaction of hexanediol‐1,6, hexanediamine‐1,6, and adipolyl chloride. These copolymers were found to be readily degradable under biotic conditions, based on weight loss, GPC, NMR spectroscopy, and tensile property measurements. Compared to abiotic hydrolysis, biodegradation occurred much faster under milder conditions. Furthermore, NMR spectroscopic analysis proved that the biodegradation of poly(ester‐amides) involves the enzymatic hydrolysis of ester groups on the backbones of polymers into acid and hydroxyl groups. No breakdown of amide bonds was observed under the given biotic conditions. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of multiacrylic resins from epoxy resins
Authors: Boutevin B. , Parisi J. P. , Robin J. J. , Roume C.
Published: April 2003

The action of methacrylic acid onto tetraglycidyl methylene dianiline, tetraglycidyl sulfone dianiline, triglycidyl triphenylmethane (TACTIX), and epoxy novolac resins was performed using different catalysts. In each case, a comparative study of these catalysts was investigated depending upon the polarity of the solvent and of the temperature. Chromium complexes are better in low polar solvents. The reactions were monitored by 1H‐NMR, by epoxide titration, and by size exclusion chromatography (SEC), and the reactivity of these resins could be compared. Finally, the study of these materials obtained after radical and photochemical cross‐linking, especially by dynamic mechanical analysis (DMA), shows that these materials exhibit high Tg's (200°C for methacrylated TACTIX) compared to those of the corresponding multiepoxides cured by diamines. © 1993 John Wiley & Sons, Inc.
Proton exchange membranes by radiation grafting of styrene onto FEP films. I. Thermal characteristics of copolymer membranes
Authors: Gupta B. , Scherer G. G.
Published: April 2003

Thermal behavior of radiation‐grafted and sulfonated poly(tetrafluoroethylene‐hexafluo‐ropropylene)‐g‐polystyrene membranes was evaluated using thermogravimetric analysis. A three‐step degradation pattern was observed from thermograms of all the membranes and was attributed to the dehydration, desulfonation, and degradation of the FEP backbone. The evidence for desulfonation was reflected in the loss in ion exchange capacity of the heat‐treated samples. The membranes were found to undergo loss in ion exchange capacity beyond ∼ 200°C. No trace of sulfonic acid groups as the ion exchange sites was found above ∼ 350°C. The swelling of heat‐treated membranes was also reduced considerably. However, the loss in swelling was much higher than that in the ion exchange capacity of the corresponding membrane. The results were explained in terms of cross‐linking reaction occurring in the membrane matrix during the desulfonation process that imparts rigidity in the membrane matrix. © 1993 John Wiley & Sons, Inc.
Solid‐state polycondensation of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. I.
Authors: Karayannidis George P. , Kokkalas Demetris E. , Bikiaris Demetris N.
Published: April 2003

Poly(ethylene terephthalate) (PET), taken from postconsumer soft‐drink bottles, was subjected to solid‐state polycondensation, as received or after dissolution in various solvents and precipitation in methanol. The solvents used were: benzyl alcohol, phenol/tetrachloroethane 60/40, or o‐chlorophenol. The effect of various reaction parameters, such as reaction temperature (180, 200, 220, and 230°C), and time on intrinsic viscosity [η] and carboxyl and hydroxyl end‐group content have been investigated. During the solid‐state polycondensation of PET that was used as received, both esterification and transesterification took place at all temperatures, while in PET samples, used after dissolution, the transesterification was observed only at 230°C. The highest number average molecular weight, Mn = 60,200, was obtained from PET with initial Mn = 20,300, dissolved in o‐chlorophenol, after solid‐state polycondensation at 230°C for 8 h. © 1993 John Wiley & Sons, Inc.
Photodegradation of polymer materials containing flame‐cut agents
Authors: Torikai Ayako , Kato Hitoshi , Fueki Kenji , Suzuki Yuji , Okisaki Fumio , Nagata Masatoshi
Published: April 2003

Photodegradation of incombustible materials [polystyrene (PSt) and polypropyrene (PP) containing 2 wt% of decabromodiphenyl oxide (DBDE) or tetrabromobisphenol‐A (TBA) as a flame‐cut agent] were studied using Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm, UV‐visible spectra and FTIR spectra were measured to identify the chemical structural changes of the polymers. Number of chain scissions, which is a measure of the polymer degradation, was estimated from the results of GPC measurements. It was found that the photostability of PP and PSt was reduced by the addition of DBDE or TBA. Photodegradation of these polymers took place by the irradiation of the light of wavelengths lower than 320 and 360 nm for the polymers containing TBA and DBDE, respectively. The most effective irradiation wavelengths for main chain scission are found to be 260–280 and 300 nm for PP or PSt–TBA samples and PP or PSt–DBDE samples, respectively. © 1993 John Wiley & Sons, Inc.
Sorption of aromatic compounds in water using polymer sorbents containing amino groups
Authors: Martel Bernard , Morcellet Michel
Published: April 2003

Porous organic sorbents containing primary amino groups and crosslinked with divinylbenzene or ethyleneglycol dimethacrylate were used for the recovery of various organic pollutants from aqueous solutions. The kinetics of sorption of these solutes is dependent on the specific area and the average pore radius of the sorbent. Physical sorption and chemical interaction of the acid solutes with the amino functions are both involved in the sorption process. The variation of the sorption capacity with the specific area of the solute depends on the nature of the solute. Experiments with mixtures of organic solutes show that the sorption of a given solute may be increased or decreased by the presence of another one. The capacity is increased during cycles of using and regenerating the sorbent. © 1994 John Wiley & Sons, Inc.
Fibers from DMAc‐LiCl solutions of steam exploded wood
Authors: Focher B. , Marzetti A. , Conio G. , Marsano E. , Cosani A. , Terbojevich M.
Published: April 2003

Poplar wood was steam exploded under various experimental conditions (230°C, 120–360 sec) and was then dissolved in dimethylacetamide‐lithium chloride (DMAc‐LiCl). Solutions of different concentrations (cp 4–10%) were obtained without any activation. Mesophases were not formed in any of the conditions tested. The good spinnability of the solutions led to wood fibers that were evaluated in terms of physico‐mechanical properties and morphological and supramolecular characteristics. The tensile strength and the modulus of the wood fibers, improved through delignification treatments, were comparable to those of conventional rayons. After annealing treatments at 260°C in protic solvent, X‐ray and CP MAS 13C–NMR experiments revealed evidence of a marked modification of the fiber supramolecular structure. © 1994 John Wiley & Sons, Inc.
Effect of E/P ratio and VA content on flow behavior of EPDM and EVA blends
Authors: Ghosh M. K. , Das C. K.
Published: April 2003

The effect of E/P ratio of EPDM rubber and VA content of EVA copolymer on the flow behavior along with the extrudate morphology of EVA and EPDM blends have been studied as a function of shear rate and processing temperature. High E/P ratio EPDM rubber and low VA content EVA render high viscosities to the blend within the temperature range studied. The same trends hold true for extrudate swell. Stored elastic energy and relaxation time are higher for high E/P ratio EPDM and low VA content EVA. However, compositions with low E/P ratio EPDM exhibit higher shear modulus. At a particular blend composition these rheological parameters show a change in their pattern. Melt fracture occurs to a larger extent for the high E/P ratio EPDM in its blend with low VA content EVA. © 1994 John Wiley & Sons, Inc.