bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface characteristics of polydimethylsiloxane—poly(methyl methacrylate) block copolymers and their PMMA blends
Authors: Inoue Hiroshi , Matsumoto Akihiro , Matsukawa Kimihiro , Ueda Akira , Nagai Susumu
Published: April 2003

To draw a relationship between surface concentration of the siloxane segment and adhesion performance, surface properties of the polydimethylsiloxane—poly(methyl methacrylate) block copolymers(PDMS‐b‐PMMA) prepared via poly(azo‐containing siloxaneamide)s and their PMMA blends have been studied by measurements of FT‐IR spectra, water contact angle, ESCA spectra and 180° peel strength toward pressure‐sensitive adhesive tape. The water contact angles of the chloroform‐cast blend films increased abruptly with siloxane bulk concentrations, or siloxane contents, particularly, on the air‐side surfaces to reach almost 100° in low siloxane content. A marked increase of the contact angle was observed in the blends containing siloxane chain length (SCL) of longer than 2000. ESCA data evidently confirmed for these blend systems that the siloxane segments with low surface energy were accumulated or enriched mainly on the air‐side surface, and that, on the other hand, polar PMMA segments with high surface energy were oriented to the glass‐side surface and the inside of the films. This surface accumulation behavior of the siloxane segments reflected the 180° peel strength, as a measure of adhesion performance. The water contact angle and 180° peel strength were unequivocally correlated to the siloxane surface concentration estimated from ESCA data. Conversely, in the compression‐molded blend films made by a hydraulic press between a Teflon and a stainless steel plate, the extent of surface accumulation of the PDMS segment was lower than that of the chloroform‐cast films, suggesting lower degree of segment migration in hot‐press films, probably due to substrate surface energy and lower relaxation in the blend melts.
Surface modified polysulfone hollow fibers. III. Fibers having a hydroxide group
Authors: Higuchi Akon , Nakagawa Tsutomu
Published: April 2003

Polysulfone ultrafiltration hollow fibers were chemically modified on the surfaces with propylene oxide and Friedel‐Crafts catalysts. A peak at 1.6 ppm was observed in H1‐NMR spectrum of the modified fibers at 45°C, while the peak was not observed at 27°C measurements. The peak was attributed to a hydroxide group from the peak shift at high temperature. Micro ATR spectra of the modified fibers also suggested existence of CH(CH3)CH2OH segments on those surfaces. The modified fibers showed 10–80% rejection of polyethylene glycol 6000 at feed concentration of 0.5 wt %, depending on the conditions of surface reaction, and were found to have smaller molecular cut‐off than nonmodified fibers. The fibers were also compared with modified fibers with propane sultone reported previously [A. Higuchi et al., J. Appl. Polym. Sci., 36, 1753 (1988)], which had negatively charged segments of CH2CH2CH2SO. Absorption of bovine serum albumin on the modified fibers was estimated to be less than the nonmodified fibers from permeation measurements. It is suggested that fibers having hydrophilic surfaces show better results of anti‐absorption of solutes than the nonmodified fibers.
Mössbauer studies of ferric chloride containing ethyl methacrylate‐n‐butyl methacrylate copolymer
Authors: Kapur G. S. , Brar A. S.
Published: April 2003

Ethyl methacrylate(EMA)‐n‐butyl methacrylate (nBuMA) copolymer containing anhydrous ferric chloride was prepared by free radical polymerization at 70°C. TGA studies show that the addition of ferric chloride increases the thermal stability of the copolymer. Mössbauer studies of the copolymers showed the presence of Fe3+ species only. Mössbauer studies of the copolymer heated at 150°C, 250°C, and 500°C for 1 h showed that during the thermal degradation, Fe3+ species are reduced to Fe2+ and then finally α‐Fe2O3 is formed. The mechanism of thermal degradation has been proposed on the basis of IR, TGA, and Mössbauer studies.
The effect of hexane treatment on the permeation of silicone‐coated polyethersulfone membranes
Authors: Chen Y. , Miyano T. , Fouda A. , Matsuura T.
Published: April 2003

The polyethersulfone membranes were cast from casting solutions including poly(vinyl pyrrolidone) additive. The membranes were further dried, silicone‐coated, and used for the permeation study with hydrogen and nitrogen gases. It has been found that solvent hexane which was included in the silicone rubber solution for surface coating increased the pore size on the membranes surface when poly(vinyl pyrrolidone) was present in the membrane. The above effect counteracted the pore size decrease by silicone coating, and, as a result, an H2/N2 permeability ratio of only 8.9 was achieved as compared with 28, which was obtained when the base polyethersulfone membrane was prepared from a casting solution without poly(vinyl pyrrolidone) additive.
Fast atom bombardment mass spectrometry of disaccharide polyether polyols
Authors: Viswanathan Tito , Toland Alan , Liu Rui‐Qin , Lay Jackson O.
Published: April 2003

The products resulting from the propoxylation of sucrose and lactose under alkaline conditions have been studied using FAB mass spectrometry. Soft desorption/ionization, using fast atoms, was expected to show intense protonated molecules for each component of the reaction mixture, thus allowing the extent of propoxylation to be examined under various conditions. However, it appears that addition of the FAB matrix, namely thioglycerol, prior to mass spectral analysis, resulted in alteration of the analyte via hydrolysis/dehydration, with protonated molecules appearing only for matrix/analyte reaction products, and not the original compounds which were to be examined. The resulting mass spectra, however, provided information regarding the extent of propoxylation and were consistent with results obtained by other researchers examining acetylated sugars using CI‐MS.
Preparation and some properties of hydrophilic membranes obtained by radiation grafting of methacrylic acid onto fluorinated polymers
Authors: Hegazy El‐Sayed A. , Taher N. H. , Ebaid A. R.
Published: April 2003

Hydrophilic membranes were prepared by direct radiation grafting of methacrylic acid (MAA) onto poly(tetrafluoroethylene‐perfluorovinylether) copolymer (PFA) and poly(tetrafluoroethylene‐hexafluoropropylene) copolymer (FEP) films followed by alkaline treatment to confer ionic character in the graft copolymer. Addition of 0.5 wt % FeCl3 to the monomer solution effectively inhibited the homopolymerization process and higher grafting yield was obtained. The graft copolymerization of MAA was carried out in presence of methanol/water mixture (30/70 wt %) in nitrogen atmosphere irradiation. The dependence of the grafting rate on MAA concentration was found to be 0.63 and 0.94 order for PFA and FEP films, respectively. This grafting system proceeds by the front mechanism in which the monomer diffuses through the already grafted layer formed initially. Some selected properties of the graft copolymers were investigated. It was found that the grafted membranes possess good mechanical, electrical, and hydrophilic properties which may make them promising in some practical applications.
Study on the compatibility of the blend of poly(aryl ether ether ketone) with poly(aryl ether sulfone)
Authors: Yu Xiaomei , Zheng Yubin , Wu Zhongwen , Tang Xinyi , Jiang Bingzheng
Published: April 2003

Poly(aryl ether ether ketone) is found to be compatible with poly(aryl ether sulfone) at a blending temperature 310°C. There is a single glass transition temperature (Tg) for various compositions of the blend. The relationship ofTgwith composition obeys Gordon‐Taylor's equation, where the adjustable parameter k is 0.43. Thermodynamic interaction parameter χ12is estimated to be ‐0.001 according to Nishi and Wang's melting point depression equation. When the processing temperature is above 350°C, phase separation takes place as shown by a double mechanical loss tangent relaxations in the range of 100–280°C.
Incompatible ternary blends based on unsaturated polyester resins. I. Phase diagrams
Authors: Suspene L. , Pascault J. P.
Published: April 2003

We have determined pseudo ternary phase diagrams for blends based on unsaturated polyester resins and an elastomeric additive. Size exclusion chromatography analysis is a well‐known method for quantifying the demixed phase composition in the case of isomolecular polymers. But when some fractionation occurs, our results show that this analysis becomes inapplicable. In our systems, due to the presence of nitrogen atoms in the elastomer, elemental analysis has been used, and, with the help of the percent of styrene, this leads to the determination of the pseudo ternary phase diagrams. The major cause of this fractionation is the high polydispersity of the UP prepolymer. Lowering the molecular weight of the UP prepolymer leads to a partial miscibility with styrene. This unexpected phenomenon may be attributed to a chain‐end effect rather than a real molecular weight effect. Finally, we have defined a compatibility window between 1–3 or 1–7 phr of elastomer, where the solutions are two‐phase systems but without any sedimentation processes, even after several weeks. This compatibility window is certainly limited by binodal and spinodal curves. The higher limit, 3–7 phr of elastomer, depends strongly on the type of chain ends (hydroxyl or carboxyl) of the UP prepolymer.
The β‐crystalline form of wollastonite‐filled polypropylene
Authors: Jingjiang Liu , Xiufen Wei , Qipeng Guo
Published: April 2003

A study has been made of the thermal, X‐ray diffraction, and dynamic mechanical characteristics of polypropylene (PP1330, a copolymer containing 22% ethylene) filled with wollastonite. Various levels of β‐form crystallinity were produced in the PP by mixing in varying amount of wollastonite. It has been found that all the wollastonite‐filled samples contain both the α‐and the β‐forms, and four melting transitions were observed instead of only two of the unfilled PP on the DSC scan. The conversion of the β‐to the β‐form on heating has been observed. The relative amount of the β‐form in the samples was measured from WAXS data by the K value. The K value obtained increases with increasing wollastonite content. Dynamic mechanical measurements showed an increase in the magnitude of the damping in the high‐temperature region for the wollastonite‐filled PP and the contribution from the filler‐matrix boundary. Wollastonite acted as both a reinforcement and a β‐nucleator for PP.
The effect of crosslinking on properties of polyurethane elastomers
Authors: Petrović Zoran S. , Ilavský Michal , Dus̆ek Karel , Vidaković Mladen , Javni Ivan , Banjanin boz̆o
Published: April 2003

A series of segmented polyurethanes from two polyols, 4,4′‐diphenylmethane diisocyanate (MDI) and butane diol was synthesized. The degree of chemical crosslinking was controlled by varying the ratio of poly(oxypropylene) diol to poly(oxypropylene/oxyethylene) triol. The samples were prepared at the stoichiometric ratio of NCO to OH groups and at a constant concentration of hard segments (butane diol; MDI) equal 50 wt %. At low concentrations of the triol the molecular weight of the polyurethanes increases; at higher concentrations (above 9 mol %) crosslinked products are obtained. All samples show a distinct two‐phase structure and in the region of 0–150°C the dynamic mechanical behavior is affected by the hard phase. Chemical crosslinking was found to increase the tensile strength and strain at break, but did not affect appreciably the tear strength, hardness, and soft segment glass transition. The stress relaxation rate at room temperature was found to depend both on the elongation and on the degree of crosslinking. A comparison of the sol fractions ws found for crosslinked samples with the predictions of the theory of branching processes proved that the achieved conversions of reactive groups in networks are high (∼ 0.98).
Determination of the composition of common linear low density polyethylene copolymers by 13C‐NMR spectroscopy
Authors: De Pooter M. , Smith P. B. , Dohrer K. K. , Bennett K. F. , Meadows M. D. , Smith C. G. , Schouwenaars H. P. , Geerards R. A.
Published: April 2003

A comprehensive 13C‐NMR method for the analysis of composition in the most common commercial polyethylene copolymers has been established. The method covers ethene copolymers with propene, butene‐1, hexene‐1, octene‐1, and 4‐methyl pentene‐1 in the composition range of 1–10 mol %. The chemical shift assignments and T1 values of the resonances of the copolymers are presented. Results of precision studies and interlaboratory analyses showed that the molar composition could be determined with a relative precision at 2δ of about 6%. This method is being proposed to ASTM as Method X70‐8605‐2.
Rheological properties of polypropylene/high‐density polyethylene blend melts. I. Capillary flow properties
Authors: Fujiyama Mitsuyoshi , Kawasaki Youtoku
Published: April 2003

Three kinds of isotactic polypropylenes (PP) with different melt flow indexes (MFIs) were melt‐blended with three kinds of high‐density polyethylenes (HDPE) with different MFI using a screw extruder, and the morphologies and capillary flow properties such as flow curve, entrance effect, Barus effect, and melt fracture were studied. When HDPE contents were 70 wt % or above and PP particles formed the disperse phase, the size of the particles decreased with decreasing viscosity of PP. When HDPE contents were 30 wt % or below and HDPE particles formed the disperse phase, the size of the particles was minimum when the viscosities of PP and HDPE were similar. The die swell ratios of the blends were higher than those of the components. On the other hand, the entrance correction coefficients of the blends were intermediate between those of the components. There was no correlation between the die swell ratio and the entrance corretion coefficient. Therefore, it is not always appropriate to regard the entrance correction coefficient as a measure of melt elasticity in the case of inhomogeneous polymer systems such as PP/HDPE blend.
Dynamic mechanical analysis of fibers. II. Estimation of fiber orientation and characterization of heat set PET yarns
Authors: Khanna Y. P. , Taylor T. J. , Kumar R.
Published: April 2003

A drawn PET yarn was heat set (annealed) at temperatures between 110°C and 245°C in an unconstrained mode and the samples characterized by dynamic mechanical analysis (DMA). A method for estimating the fiber orientation factor (α) is proposed using DMA and shown to be more sensitive than the crystalline orientation (x‐ray diffraction) or total orientation (birefringence) measurements of the heat set yarns. The extension/shrinkage behavior of the heat set yarns has been discussed in the light of morphological changes, e.g., degree of orientation and the micro‐crystallite formation. Unlike in the unconstrained mode, heat setting under constraint does not lead to the formation of micro‐crystallites as revealed by differential scanning calorimetry. As a consequence, although the modulus and degree of orientation increase upon constrained annealing, the thermal stability, i.e., loss of orientation (reflected by shrinkage) could not be improved.
Correlation of binder mechanical properties with microstructure for poly(butadiene–acrylonitrile–methacrylic acid) terpolymer: 13C‐NMR and pyrolysis‐GC studies
Authors: Rao M. Rama , Sebastian T. V. , Radhakrishnan T. S. , Ravindran P. V.
Published: April 2003

13C‐NMR spectroscopy (22.5 MHz) was used to characterize poly(butadiene (B)–acrylonitrile (A)–methacrylic acid (M)) liquid terpolymers prepared by emulsion polymerization. The sequence distribution of the monomers in the terpolymers was described in terms of triads BBB, ABA, ABB, BBA, MBB, and AMB and was found to vary with the mode of addition of methacrylic acid monomer. The NMR data was found to be in good agreement with a mechanism of polymerization in which methacrylic acid is preferentially involved in initiation reactions by a thiyl radical arising from the reaction of the chain modifier, 1‐dodecanethiol, and cyanoisopropyl radical generated from AIBN initiator. Binders obtained by curing the liquid terpolymers with an epoxy resin showed widely varying mechanical properties with tensile strength varying from 4.3 to 0.6 kg/cm2 and elongation at break from 130 to 450%. It was found that tensile strength increases and elongation decreases with the number of acrylonitrile units between the methacrylic acid crosslinks. Good correlation was obtained between triad population ratio [ABB + BBA] [BBvB]/[ABA][MBB] and the mechanical properties of the binders. Pyrolysis‐GC data at 550 and 600°C confirmed the results obtained from 13C‐NMR, and the mole ratio of butadiene to arylonitrile in the pyrolyzates showed correlation with the properties of binders.
Hydroxypropylmethylcellulose–anionic surfactant interactions in aqueous systems
Authors: Alli Dhananjaya , Bolton Sanford , Gaylord Norman G.
Published: April 2003

The increase in the viscosity of an aqueous solution or gel of hydroxypropylmethylcellulose (HPMC) in the presence of an anionic surfactant is attributed to a two‐step process: (a) the surfactant undergoes ion–dipole interaction with the ethereal oxygen in HPMC, in the absence or presence of water, and (b) hydrocarbon moieties in the now pendant surfactant molecules undergo hydrophobic bonding, in the presence of water, resulting in an apparent increase in the molecular weight of the HPMC. DSC of dry blends and dried gels or films confirmed HPMC–sodium lauryl sulfate interaction. Work‐to‐break measurements on films cast from aqueous solutions of HPMC, in the absence or presence of anionic surfactants, indicated an apparent increase in the molecular weight of HPMC in the presence of surfactants.
Structure–properties relations of thermally cured epoxy–lignin polyblends
Authors: Feldman D. , Banu D. , Natansohn A. , Wang J.
Published: April 2003

A bisphenol A based epoxy adhesive (EP) was modified by polyblending with Kraft Lignin (L). A systematic investigation of the thermally cured EP‐L polyblends with up to 40% by weight L was undertaken. Adhesive shear tests, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid‐state CP‐MAS NMR spectroscopy were performed to establish the effect of L on the mechanical properties of the polyblends and on the morphology of these crosslinked structures. The possibility of an enhanced degree of bonding between L and the EP network is discussed. This bonding can arise from a chemical reaction between L and some unreacted amine groups present in the hardener.
Synthesis and structure–property relationships of UV‐curable urethane prepolymers with hard–soft–hard blocks
Authors: Lai Yu‐Chin , Baccei Louis J.
Published: April 2003

UV‐curable urethane prepolymers derived from diisocyanates, rigid diols, and polypropylene glycols of different molecular weights and end‐capped with 2‐hydroxylethyl methacrylate were prepared by stepwise addition reactions. These prepolymers have the common structure, HEMA‐hard segment‐soft segment‐hard segment‐HEMA. As the weight ratio of soft segment to hard segment and thus the rigidity varied, the cured films from these prepolymers exhibited a wide range of mechanical and other key properties such as oxygen permeability.
Characterization of cationic water‐soluble polyacrylamides
Authors: Vu Can , Cabestany Jean
Published: April 2003

Copolymers of poly(acrylamide‐co‐acryloyloxyethyltrimethylammonium chloride or AM–CMA) and poly(acrylamide‐co‐methacryloyloxyethyltrimethylammonium chloride or AM–CMA) prepared by inverse emulsion polymerization were characterized by different analytical techniques. The chemical composition of the copolymers was estimated by elemental analysis and by nuclear magnetic resonance spectroscopy (NMR). NMR spectroscopy and computer simulation were further used for investigating the polymers' sequence distribution. The poly(AM–CMA) copolymers are chemically more homogeneous than are the poly(AM–CMA). The configurational propagation of dyads and triads for the homopolymers obeys Bernouilli's statistics. For the copolymers, the chemical sequences distribution is governed by Markov's first‐order statistics.
Synthesis of graft polyesters by ring‐opening copolymerization of epoxy‐terminated poly(ethylene glycol) with acid anhydrides
Authors: Ikeda Isao , Simazaki Yoshitomo , Suzuki Kimihiro
Published: April 2003

The copolymerization of epoxy‐terminated poly(ethylene glycol methyl ether) (CH3PEG–epoxide) with phthalic anhydride catalyzed by tertiary amines was performed in o‐dichlorobenzene at 100°C to prepare the PEG graft polyester. 4‐Dimethylaminopyridine was the most favorable catalyst to give the graft polyester with relatively high molecular weight. The acidity of the reaction solution decreased and Mn of the graft polyesters increased with reaction time. The CH3PEG/phthalic acid ratio of the products was little affected by the kind of solvent and the reaction temperature above 100°C, but Mn increased with lowering the polarity of solvents and with raising the temperature. Other acid anhydrides, including maleic, succinic, tetrahydrophthalic, and pyromellitic anhydride, could be copolymerized with CH3PEG–epoxide. The number of branched CH3PEG chains was controlled by the mixing of low molecular weight epoxide such as n‐butyl glycidyl ether. CH3PEG component of the graft copolymers melted and crystallized at lower temperature than the raw CH3PEG because of the restriction on the trunk polyester chain.
On the stability and in situ epoxidation of natural rubber in latex by performic acid
Authors: Bac Nguyen Viet , Terlemezyan Levon , Mihailov Marin
Published: April 2003

The aggregative stability of natural rubber (NR) latex stabilized by nonionic, fatty alcohol ethylene oxide condensate surfactant (Verol S‐15) was studied in the presence of formic acid. Natural rubber latex having an additional 3–5 phr surfactant is stable at pH 2 when acidified by formic acid and can be successfully subjected to the subsequent in situ epoxidation. Using a large ratio of H2O2 to isoprene unit (0.4–4.0 M/M) and large excess of H2O2 to HCOOH (3–13 M/M) in reaction, the in situ epoxidation can be performed with reaction mixture having dry rubber content up to 35–37% at room temperature or up to 28% at 50°C. This reaction leads to products of large range of epoxide contents and characterized by absence of side‐ring opening groups, proved by IR and 1H‐NMR analysis. By infrared spectroscopy it was demonstrated a good correlation between the absorbances of the residual double bonds and of the epoxide groups versus the epoxide content in the range from 0 to approx. 60 mol % level. The solubility and gel content were studied in various solvents, demonstrating that epoxidation leads to increasing gel content at high epoxide levels and to enhancing sensitivity of the product toward polar solvents. By GPC, it was shown for the soluble fraction that epoxidation was accompanied by reducing the molecular weight and by change of the MWD compared with the original NR.
Separation of water–ethanol by pervaporation through polyion complex composite membrane
Authors: Karakane H. , Tsuyumoto M. , Maeda Y. , Honda Z.
Published: April 2003

For the purpose of separating alcohol–water mixtures by the use of the pervaporation technique, new composite membranes composed of polyion complexes (PIC) as a separating layer were developed. The polyion complex structure, consisting of polyacrylic acid (PAA) and polycation, provided excellent permeation rate and selectivity. Among the polycations, ionenes, which have quaternary ammonium groups in the backbone chain, were effective in giving membranes of higher permselectivities. High selectivity of PIC membranes was observed at high ethanol concentration regions in the feed mixture. For the azeotropic mixture of water/ethanol (95 wt % EtOH) at 60°C, the PAA‐based PIC membrane had the following separation properties: separation factor ∼ 3,500 and permeation rate ∼ 1.6 kg/m2 h.
Dynamic mechanical and calorimetric analysis of compression‐molded PLLA of different molecular weights: Effect of thermal treatments
Authors: Migliaresi C. , Cohn D. , De Lollis A. , Fambri L.
Published: April 2003

The effect of thermal treatment on compression‐molded poly(L‐lactic acid) (PLLA) has been investigated by means of viscosimetric molecular weight (\documentclass{article}\pagestyle{empty}\begin{document}$$M_{w_v}$$\end{document}) determination, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). Starting from two initial molecular weight PLLAs, amorphous samples with different \documentclass{article}\pagestyle{empty}\begin{document}$$M_{w_v}$$\end{document} have been obtained due to degradation occurring during the molding. The crystallization capability of the materials after different thermal treatments has been determined as a function of the molecular weight, and their dynamic mechanical properties have been measured. Initially fully amorphous PLLA matrices attained very high degrees of crystallinity (up to 90%) following different annealing processes. Concomitantly, PLLA degrades due to thermal cleavage of the chains. This is an unavoidable effect that must be taken into consideration when defining the material processing and annealing conditions. Crystallization phenomena occurring in the material during the treatment are clearly documented by DMTA.
Investigation of structural and mechanical properties of copper‐chloride‐doped nylon‐6 films. II. Elastic and viscoelastic studies
Authors: Kelkar D. S. , Bhat N. V.
Published: April 2003

The article reports the effect of variation in the concentration of copper chloride on the elastic and viscoelastic properties of nylon‐6 films. The elastic modulus for the film is determined using sonic velocity measurement technique. The glass transition temperatures are determined from dynamic mechanical studies with the Rheovibron. It is observed that the glass transition temperature of the doped films increases with increase in the dopant concentration. It is also observed that at low concentrations of doping (up to 1.25%) the salt acts as a plasticizer, whereas for higher concentration of doping (up to 12.5%) it acts as an antiplasticizer.
Synthesis and thermal stability of bitumen–polymer ionomers
Authors: Engel R. , Vidal A. , Papirer E. , Grosmangin J.
Published: April 2003

Road bitumens, when combined with polymers such as styrene‐butadiene‐styrene (SBS) block copolymers, show improved mechanical properties. The corresponding blends, however, are thermodynamically unstable, and phase separation quickly occurs at higher temperatures. A solution is proposed for improving the thermal stability of these blends: It is based on the formation of reversible, ionic interactions between the bitumen and the SBS, thereby leading to a mixed, ionomeric network. Both compounds are first chemically modified by the grafting of carboxylic acid groups, then mixed, and, finally, the available acid groups are partially or totally neutralized by adding zinc acetate dihydrate to the blends. Comparison of the thermal stability of the resulting ionomeric blends with that of the untreated blends is discussed. The use of ion‐ion interactions to enhance miscibility, which, for the first time, has been extended to bitumen–polymer systems, is shown to be a means of obtaining stable blends.
Phase separation and morphology in ethylcellulose/cellulose acetate phthalate blends
Authors: Sakellariou P. , Rowe R. C.
Published: April 2003

This article discusses the phase separation and morphology of ethylcellulose/cellulose acetate phthalate blended films cast from methanol/methylene chloride (50/50 v/v) solvent mixture. The solvent system has been shown to be a cosolvent for CAP and a solvent/nonsolvent for EC. The two polymers have been shown to phase separate for all blend compositions via nucleation and growth. The morphology of these systems consists of a dispersion of broad size distribution of the minor component in a matrix of the major one. The formation of two layers due to coalescence of the dispersed phases and their eventual precipitation has been observed for the middle blend compositions. Finally, the phase separation in this system is discussed in terms of the Flory–Huggins theory and changes in the solvency mechanism during film casting. Enrichment of the solvent system in methanol at relatively early stages of film casting leads to changes in the system viscosity, relative chain conformation in solution, and chain diffusion. The effect of these parameters on the final morphology are discussed in terms of deviations from the equilibrium binodal decomposition.
Permeation behavior of dextrans by charged ultrafiltration membranes of polyacrylonitrile photografted with ionic monomers
Authors: Kobayashi Takaomi , Kumagai Kazuyasu , Nosaka Yoshio , Miyama Hajime , Fujii Nobuyuki , Tanzawa Hiroshi
Published: April 2003

Charged copolymers, polyacrylonitrile, having grafts of quaternized poly(N,N‐dimethylaminoethylmethacrylate) and poly(sodium p‐styrenesulfonate), were synthesized by photograft‐polymerization. The charged ultrafiltration membranes, which had heterogeneous porous structures, were prepared by casting graft polymer solution containing poly(vinyl alcohol) into water.

The permeation of nonionic dextran and anionic dextransulfate through the charged membranes was studied by ultrafiltration in aqueous solution. The molecular weight cutoff characteristics of the charged membrances were obtained using dextrans of various molecular sizes. The permeation behavior was discussed in terms of the charge effect of the graft polymers and electrostatic interaction between the polymers and the solute molecules.
Effect of moisture on the crystallization behavior of PET from the quenched amorphous phase
Authors: Bianchi Riccardo , Chiavacci Paolo , Vosa Renato , Guerra Gaetano
Published: April 2003

The dependence on the moisture content of the glass transition temperature (Tg) and of the crystallization temperature from the quenched amorphous phase (Tc) for poly(ethylene terephthalate) (PET) samples is studied by differential scanning calorimetry.

For low moisture contents, very large and reversible decreases of Tc but small decreases of Tg are observed. This indicates that the strong increase of nucleation rate observed for PET in the presence of moisture is not related to the plasticizing effect that produces significant Tg changes.
1H‐NMR studies on water in methacrylate hydrogels. II
Authors: Yamada‐Nosaka Atsuko , Tanzawa Hiroshi
Published: April 2003

Properties of water in the wet membranes of a random copolymer of methyl methacrylate and methoxy poly(ethylene glycol)–monomethacrylate P(MMA‐co‐M100G) and of a graft copolymer of vinyl chloride and methoxy poly(ethylene glycol)–monomethacrylate P(VC‐g‐M100G) membranes were studied by proton NMR spectroscopy. Both polymers contain flexible polyoxyethylene side chains. Temperature and frequency dependences of relaxation times, changes of signal intensity of water protons on freezing and thawing, and saturation transfer were measured for both copolymers. These experimental results revealed that most of the bound water in these copolymers does not exist in a rigid state as suggested for the other hydrogels. The introduction of flexible hydrophilic side chains resulted in high mobility of the water molecules bound to the side chains (the apparent correlation time Tc ∼ 10−10 s). For the graft copolymer P(VC‐g‐M100G), hydrophilic polyoxyethylene side chains are contiguous to each other. Because of the interaction between the side chains, the mobility became more complex than that for the random copolymer P(MMA‐co‐M100G). The difference in the mode of mobility of water on the membrane surface may be related to the difference of the membrane characteristics of these copolymers.
Effect of a surface active pyrrole on the conductivity of polypyrrole composites
Authors: Ruckenstein Eli , Chen Jyh‐Herng
Published: April 2003

A surface active pyrrole, which has a long hydrophobic chain attached to the 3 position of the pyrrole ring, is used to modify the surface properties of the pores of a porous, crosslinked polystyrene. The latter is prepared starting from a concentrated emulsion (an emulsion with a large volume fraction of the dispersed phase, here 0.81) of water dispersed in a continuous medium composed of styrene, divinyl benzene, a suitable surfactant, an initiator, and the surface active pyrrole. This modified crosslinked porous medium is emplyed as the host for a polypyrrole composite that is prepared first by imbibing the host with a solution of pyrrole and subsequently with an oxidant solution. The latter plays the role of catalyst for polymerization as well as the role of dopant. The presence of the head groups of 3‐alkyl pyrrole molecules on the surface of the pores of the host polymer increases the affinity of the surface for pyrrole. The improved wetting thus achieved for the pyrrole solution ensures a higher connectivity among the pyrrole films present on the internal surface of the host polymer and increases the conductivity of the polypyrrole composites by a factor of 2 to 14, depending upon the solvents employed for pyrrole and oxidant.
Experimental investigation of vinyl chloride polymerization at high conversion—reactor dynamics
Authors: Xie T. Y. , Hamielec A. E. , Wood P. E. , Woods D. R.
Published: April 2003

A series of suspension polymerizations of vinyl chloride monomer (VCM) was carried out in a 5‐L pilot plant reactor over the temperature range, 40–70°C. The reactor pressure and monomer conversion were monitored simultaneously every 7–8 min. The critical conversion Xf, at which the liquid monomer phase is consumed, was considered to occur when the reactor pressure fell to 98% of the vapor pressure of VCM for suspension at the polymerization temperature. The reactor model predictions of pressure are in excellent agreement with the experimental data over the entire conversion and temperature ranges studied. The mechanism of reactor pressure development for VCM suspension polymerization is discussed herein in some detail. For isothermal batch polymerization, the reactor pressure falls in two stages due to the effect of polymer particle morphology on pressure drop. The first stage is due to the volume increase of the vapor phase as a result of volume shrinkage due to conversion of monomer to polymer. The monomer phase is not yet consumed at this stage, but it is trapped in the interstices between primary particles creating a mass transfer resistance; therefore, the reactor pressure drops slowly. The second stage is due to both the volume increase of the vapor phase and to the monomer in the vapor phase diffusing into the polymer phase because of the subsaturation condition with respect to monomer in the polymer phase. The reactor pressure drops dramatically with an increase in monomer conversion at this stage. The present model can be used to predict reactor dynamics during suspension polymerization under varying temperature and pressure conditions.
Etch rate studies of base catalyzed hydrolysis of polyimide film. II
Authors: Pawlowski W. P. , Coolbaugh D. D. , Johnson C. J. , Malenda Mary J.
Published: April 2003

The influence of a potassium carbonate (K2CO3) additive on the base catalyzed hydrolysis of polyimide (Kapton†) film in aqueous potassium hydroxide (KOH) was determined experimentally. The etch rate is significantly greater for KOH/K2CO3 solutions compared with solutions composed of KOH only. The experimental order of the reaction with respect to the KOH concentration was found to be 1.5. In addition, the rate was found to increase linearly with respect to the K2CO3 concentration at a fixed KOH concentration. Visual observations of a thinner gel layer on the surface of the film, combined with increased solubility of the etch by‐products in KOH/K2CO3 relative to KOH, help to explain the difference in etch rate. It appears the ability of K2CO3 to enhance the solubility of the hydrolyzed polyimide (polyamic acid salt) results in faster etch rates.
Free volume effects on rheological and thermal properties of polymers and polymer blends
Authors: Steller Ryszard , Zuchowska Danuta
Published: April 2003

Using the free volume theory, general relations between viscometric and volumetric properties of polymers as functions of temperature and deformation conditions (shear rate or shear stress) have been derived. In particular, it has been shown that thermal expansion of polymers can be calculated from viscometric data. The obtained relations have been applied for description of the rheological behavior of polymer blends. Theoretical predictions have been compared with experimental data. Good agreement between theory and experiment has been stated if rheological properties of blends were compared at a constant shear rate.
Residual reactivity for surface grafting of acrylic acid on argon glow‐discharged poly(ethylene terephthalate) (PET) films
Authors: Hsieh You‐Lo , Wu Meiping
Published: April 2003

The wettability of poly(ethylene terephthalate) (PET) films in water was significantly improved upon exposure to argon glow discharge. Depending upon the lengths of glow‐discharge exposure, the water contact angle (CA) of the untreated film (73.1° ± 0.1°) was reduced to between 33.7° and 41.0° on the argon glow‐discharged films. Wettability decay was observed during the initial few days. Depending upon the treatment time, the water CA stabilized 4–7 days after the treatment and the extent of the wettability decay ranged from 4.3° to 7.6°. The residual reactivity of the glow‐discharged surfaces was captured by exposing the glow‐discharged PET to acrylic acid in the liquid and vapor phases. Optimal water CAs of 54.0° and 41.9° were achieved in the liquid‐phase and the vapor‐phase exposures, respectively. Wettability decay of these acrylic acid‐grafted PET surfaces was very small (0°–1.9°) for the liquid‐phase reactions and negligible (0.3°–0.6°) for the vapor‐phase reactions. The near absence of wettability decay or the greater stability of the grafted surfaces suggested the almost complete dissipation of the residual reactivity through reactions with acrylic acid. Surface morphology of the untreated as well as the acrylic acid‐grafted PET surfaces were examined and detailed by scanning electron microscopy.
IPDI‐based polyurethane ionomer dispersions: Effects of ionic, nonionic hydrophilic segments, and extender on particle size and physical properties of emulsion cast film
Authors: Kim Chang Kee , Kim Byung Kyu
Published: April 2003

Isophoron diisocyanate (IPDI) ‐based polyester polyurethane (PU) dispersion in water was prepared in a prepolymer mixing process. Dimethylol propionic acid (DMPA), triethylamine (TEA), and triethyl tetramine (TETA) were used, respectively, as potential anionic center, neutralizing agent, and chain extender in aqueous phase. The effects of DMPA, butanediol (BD), and nonionic hydrophilic segment, viz. monofunctional ethylene–propylene oxide ether polyol, on the particle size of dispersion and the mechanical and viscoelastic properties of the emulsion cast films were systematically analyzed.
Preparation of cation‐exchange starches containing phosphoric acid groups
Authors: Khalil M. I. , Waly A. , Farag S. , Hebeish A.
Published: April 2003

Poly(glycidyl methacrylate) ‐starch graft copolymer was prepared using hydrogen peroxide/ferrous sulphate/thiourea dioxide redox system as initiator. The copolymer was treated with orthophosphoric acid (H3PO4) under a variety of conditions to discover appropriate conditions for synthesizing the copolymer that can serve as cation exchanger. Results obtained indicated that the cation‐exchange capacity is enhanced by: (a) increasing the H3PO4/epoxy molar ratio up to 4; (b) using material‐to‐liquor ratio 1 : 2; (c) increasing duration (15–300 min) and temperature (60–90°C); (d) increasing the amount of epoxy groups of the copolymer; and (e) increasing the percent neutralization of H3PO4 up to 33.3%. Based upon the results obtained with these parameters, it was postulated that three reactions are involved during treatment of the copolymer with H3PO4. These reactions are phosphorylation, crosslinking, and hydrolysis. Conditions were established under which the phosphorylation reaction occurs exclusively. Studied also were the ion‐exchange properties of the phosphorylated copolymer, namely, pKa values, capacity for heavy metal ions removal, moisture content, durability, swellability, and solubility.
The drawing behavior of polyvinylalcohol fibers
Authors: Schellekens R. , Bastiaansen C.
Published: April 2003

The solid‐state drawing behavior and properties of solution‐spun polyvinylalcohol fibers were investigated. A comparsion was made with solution‐spun, ultra‐drawn polyethylene fibers. The maximum attainable draw ratio of polyvinylalcohol fibers is low (∼ 20), even at optimized conditions with respect to polymer concentration in solution. In contrast to polyethylene, the maximum attainable draw ratio hardly increases with increasing molecular weight. However, high modulus (∼ 70 GPa) and strength (∼ 2.3 GPa) polyvinylalcohol fibers can be produced, despite the low maximum attainable draw ratio. It is suggested that the observed phenomena, with respect to both the drawing behavior and properties of polyvinylalcohol fibers, originate from intermolecular hydrogen bonds in the polymer.
Bending‐beam measurement of solvent diffusions in polyimides: Theoretical and experimental
Authors: Jou Jwo‐Huei , Hsu Li
Published: April 2003

A general formula correlating the bending curvature variation ratio of a layered structure caused by solvent‐induced swelling in its polymer overcoat with diffusion time under case II diffusion has been presented. In the event of case II diffusion, the diffusion front velocity, v, can be calculated by using this formula and measured by a bending‐beam apparatus. At room temperature, the diffusion of n‐methyl‐pyrrolidone (NMP) solvent in the film of pyromellitic phenylene diamine (PMDA‐PDA) is case II. While in PMDA‐B (‐benzidine) and benzophenone tetracarboxylic dianhydride (BPDA‐PDA), no diffusion progress can be observed. But, the diffusion in 6F‐dianhydride‐ (6FDA‐PDA) is case I with D = 0.85 × 10−9 cm2/s. It becomes anomalous when mixing with 25% PMDA‐B, but becomes case II diffusion with more PMDA‐B. The preabsorbed moisture in the films does not affect the v value. In PMDA‐PDA, v = 7.3 × 10−8 cm/s. In the 25/75 and 50/50 6FDA‐PDA/PMDA‐B blends, v = 6.3 and 11.3 × 10−8 cm/s.
Effect of flame‐retardant treatment on the mechanical properties of some tropical timbers
Authors: Eboatu A. N. , Amanfo I. , Akpabio I. O.
Published: April 2003

Potassium aluminum sulphate, hereafter referred to as alum, was used as a flame‐retardant for some African timbers. It was observed that this treatment did not drastically reduce the strength of these timbers. Reasons are adduced to explain this result.
Surface modification of UHSPE fibers through allylamine plasma deposition. II. Effect on fiber and fiber/epoxy interface
Authors: Li Z.‐F. , Netravali A. N.
Published: April 2003

The surface of ultra‐high strength polyethylene (UHSPE) fibers was modified using allylamine plasma deposition to improve their adhesion to epoxy resins. Allylamine plasma polymerization was investigated at different power inputs and polymerization times. The adhesion of treated fibers to epoxy resin was studied by single‐fiber, pull‐out tests. A special silicon rubber mold was developed to embed the single fiber in epoxy resin. The results show that the interfacial shear strength (IFSS) increased by a factor of 2 to 3 after allylamine plasma treatments. The greatest improvement, by a factor of 3.25, was obtained at 30 W for 10 min. Scanning electron microscopy (SEM) was also used to study the surface topography of fibers pulled from the epoxy resin. In most cases, it was observed that pull‐out failure occurred at the interface, as evidenced from clean fiber surfaces. In a few cases, however, fibrils were peeled from fibers. The fiber strength decreased, but initial modulus increased after the plasma treatments. The decrease in fiber strength was insignificant for treatments at a lower power input, but was significant at higher power inputs. Treatment time, however, had no significant effect on fiber strength.
Crystallization behavior of high‐density polyethylene/linear low‐density polyethylene blend
Authors: Gupta A. K. , Rana S. K. , Deopura B. L.
Published: April 2003

Binary blend of high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE), prepared by melt mixing in an extruder, in the entire range of blending ratio, is studied for crystallization behavior by differential scanning calorimetry (DSC) and X‐ray diffraction measurements. Cocrystallization was evident in the entire range of blend composition, from the single‐peak character in both DSC crystallization exotherms and meltingendotherms and the X‐ray diffraction peaks. A detailed analysis of DSC crystallization exotherms revealed a systematic effect of the addition of LLDPE on nucleation rate and the subsequently developed crystalline morphology, which could be distinguished in the three regions of blending ratio, viz, the “HDPE‐rich blend,” “LLDPE‐rich blend,” and the “middle range from 30–70% LLDPE content.” Variations in crystallinity, crystallite size, and d spacing are discussed in terms of differences in molecular structure of the components.
Living carbocationic polymerization of isobutylene by tert‐amyl alcohol/BCl3/1‐methyl‐2‐pyrrolidinone initiating system
Authors: Pratap G. , Mustafa S. A. , Hollis W. K. , Heller J. P.
Published: April 2003

1‐Methyl‐2‐pyrrolidinone has been investigated, for the first time, as an efficient electronpair donor in conjunction with tert‐amyl alcohol and BCl3 in CH2Cl2 diluent at −40°C for the living polymerization of isobutylene. The use of this new monofunctional initiator ‐trans fer (minifer) system has led to the synthesis of low molecular weight, living (near‐monodisperse) polyisobutylenes carrying “ethyl” head group and “tert‐chloro” end group (asymmetric telechelic polyisobutylenes). The nature of these groups was confirmed by 1H‐NMR spectroscopy. The living nature of the α‐ethyl‐ω‐(tert‐chloro)polyisobutylenes has been demonstrated by a linear plot, passing through the origin, of number‐average molecular weight (M̄n) vs. the amount of polymer formed (Wp) and a horizontal N (number of polyisobutylene molecules) vs. Wp plot. These results are further substantiated by gel permeation chromatography data of these polymers, and the molecular weight distributions of these polymers are narrow (low M̄w/M̄n = 1.1–1.2). The initiating efficiencies (Ieff) are close to 100% with this system. Dehydrochlorination of the prepolymer has yielded an isopropylidene (exo‐olefin) end group. Structure of the end group in the resulting polymer, α‐ethyl‐ω‐(isopropenyl)polyisobutylene, was confirmed by FTIR spectroscopy.
Specific volume of molten thermoplastic polymer composite at high pressure
Authors: Wang Y. Z. , Chia W. J. , Hsieh K. H. , Tseng H. C.
Published: April 2003

The specific volume of thermoplastic polymers and composites with glass fiber have been measured at high pressure, up to 2000 kg/cm2, in the molten state by a dilatometer. The specific volume and thermal expansion coefficient of the melts increase with increasing temperature at a constant pressure at a constant temperature. The data of specific volume of molten polymers were satisfactorily fitted to an empirical equation of state based on the Tait equation. Furthermore, it is found that the data of specific volume of molten composites were suitably fitted by an additive rule of Tait equation from the volume fractions of specific volume of polymers and the glass fiber in composites. The thermal expansion coefficients of molten polymers and composites are approach to the derivative values of the Tait equation, and the additive Tait equation, respectively.