bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoplastic elastomer by radiation grafting. I. Evaluation of processability of natural rubber grafted methyl methacrylate
Authors: Razzak Mirzan T. , Yoshii Fumio , Makuuchi Keizo , Ishigaki Isao
Published: April 2003

Processability of thermoplastic elastomer (TPE) prepared by radiation‐induced grafting of methyl methacrylate (MMA) onto radiation vulcanized natural rubber latex (RVNRL) has been evaluated using a kneader and a hot roll mill at 150°C. It was found that mixing time and revolution rate (rpm) of the kneader have significantly affected the processability. The longer mixing time and the higher revolution rate result in better processability. In such processing conditions, however, the mechanical properties were found to be inferior because the molecular chain scissions occurred during the mixing. A considerable improvement of mechanical properties was obtained when the mixing was carried out without added process oils. Blends of the grafted vulcanized natural rubber latex (RVNRL‐g‐PMMA) and MMA grafted on unvulcanized natural rubber latex (NRL‐g‐PMMA) improved processability where the better processability could be achieved at a shorter mixing time and a lower revolution rate. In addition, a comparable value of mechanical properties was obtained.
The copolymerization of vinyl chloride with 1‐olefins. V. Heat stability of copolymers of vinyl chloride with propene, 1‐butene, and 1‐pentene
Authors: Mrázek Zdenĕk , Lukás̆ Rudolf , Pr̆ádová Olga
Published: April 2003

Copolymers of vinyl chloride with propene, 1‐butene, and 1‐pentene containing 2–15 mol % of 1‐olefinic structural units were prepared. The copolymers were dehydrochlorinated at 180°C in an inert atmosphere; the amount of hydrogen chloride split off was determined by continuous potentiometry. The results show that the heat stability of propene, 1‐butene, and 1‐pentene copolymers containing the same amount of 1‐olefinic structural units does not differ significantly. Compared with the homopolymer of vinyl chloride, it is favorably affected by the presence of 1‐olefinic structural units in poly(vinyl chloride) (PVC) chains. On the other hand, however, the heat stability of copolymers is impaired by the higher content of structural defects able to initiate the dehydrochlorination reaction. These structural defects, probably represented by chloroallyl groups, are formed in the copolymers during their synthesis. At the beginning of heating, structural defects produce intensive dehydrochlorination and, therefore, copolymers of vinyl chloride with 1‐olefins if processed appear to be less thermally stable than does PVC.
Relationship between extrusion condition and mechanical properties of FRPP
Authors: Chiu Wen‐Yen , Lu Hsiang‐Chung , Chang Chia‐Lu
Published: April 2003

In this work, the relationship between extrusion condition and mechanical properties of glass‐fiber‐reinforced polypropylene (FRPP) was investigated. It was found that the extrusion flow rate was higher but the extrusion pressure was lower as the fiber content decreased. The flow rate and pressure were more temperature‐sensitive at high screw speed. As for the mechanical strength of FRPP, the yield strength decreased with increasing the fiber content, but modulus and impact strength significantly increased with increasing the fiber content. The high screw speed did not affect the mechanical strength of PP, but decreased the strength of FRPP. At higher extrusion temperature, the yield strength and modulus of FRPP increased, but the impact strength decreased. The yield strength and modulus of extrudates along the longitudinal direction of extruder were always higher than those along other directions by the effect of fiber orientation. The specimens taken from different positions of extrudate would show different mechanical strength. The way of cooling for the extrudates would affect the mechanical properties of FRPP, too. All the above relations were discussed and well explained from the contribution of fiber distribution, fiber length, crystallinity of PP, and void content.
Mechanical properties of multifilaments in different measurement conditions
Authors: Zurek W. , Jasińska A. , Frydrych I. , Jakubczyk J.
Published: April 2003

Starting from Zhurkov's and Bartenev's theories and connecting them with Bailly's theorem and the structural analysis based on the rheological model, a method of determination of parameters describing the durability of multifilament is presented. Experiments carried out on polyester and polyamide filament yarns confirmed proposed method.
Structures and gas separation properties of asymmetric polysulfone membranes made by dry, wet, and dry/wet phase inversion
Authors: Pinnau Ingo , Koros William J.
Published: April 2003

Integrally skinned asymmetric gas separation membranes were prepared by (i) dry, (ii) wet, and (iii) dry/wet phase inversion processes. The membranes were cast from a polysulfone/methylene chloride/1,1,2‐trichloroethane/2‐methyl‐2‐butanol casting system. Wet and dry/wet phase inversion membranes were quenched in methanol. Membranes made by dry/wet phase inversion using convective evaporation showed optimum gas separation performance. The average O2/N2 and He/N2 selectivities of these membranes were within 85% of those determined for a dense, solution‐cast polysulfone film, suggesting that the ultrathin skin layers were essentially defect free. The average apparent skin layer thickness of all samples tested was 270 Å. Scanning electron photomicrographs revealed that optimum membranes made by dry/wet phase inversion consist of an ultrathin skin layer, a tightly packed nodular transition layer, and an open‐cell, sponge‐like substructure. Dry/wet phase inversion membranes prepared by free‐standing evaporation resulted either in high flux and low selectivity membranes or essentially defect‐free membranes with fluxes lower than those made by convective evaporation. Dry‐phase inversion membranes exhibited extremely low gas fluxes due to thick (17.5 μm) skin layers. On the other hand, wet phase inversion membranes showed O2/N2 selectivities < 1, indicating that gas transport was determined by pore flow through skin layer defects.
Modification of epoxy resins with poly(aryl ether ketone)s
Authors: Iijima Takao , Tochimoto Takuya , Tomoi Masao
Published: April 2003

Poly(aryl ether ketone)s were used as modifiers for bisphenol‐A diglycidyl ether epoxy resin (AER 331) cured with methyl hexahydrophthalic anhydride. Poly(phthaloyl diphenyl ether) (PPDE), soluble in the uncured epoxy resin without using solvents, was prepared by the Friedel‐Crafts reaction of phthaloyl chloride and diphenyl ether. The mechanical, thermal, and dynamic viscoelastic properties of the modified resins with PPDE were examined and compared to the parent resin (AER 331). The fracture toughness, KIC, for the modified resins increased at no expense to their mechanical and thermal properties on 10 wt % addition of PPDE with molecular weights of more than 17,000. The toughening mechanism is discussed based on the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system.
N‐(carboxymethyl) trimellitimide–based polyesterimides as film formers for air‐drying protective coatings
Authors: Kishanprasad V. S. , Gedam P. H.
Published: April 2003

N‐(carboxymethyl) trimellitimide, the imidodicarboxylic acid, was prepared by the reaction between trimellitic anhydride and glycine. This was subsequently condensed in N‐methyl‐2‐pyrrolidone with the alcoholysis products obtained from linseed oil and glycerine to get different oil length polyesterimide resins. The drying characteristics of the resins and the physicochemical properties of the clear and the iron oxide pigmented coatings were evaluated. The results indicate that these materials form a promising class of film—formers for coatings of good durability and protective properties.
Thermal cis–trans isomerization of azo dye chrysophenine in cellulose matrices: Effect of morphology
Authors: Seves Alberto , Romanó Maria , Dubini‐Paglia Ernestina , Beltrame Pier Luigi , Marcandalli Bruno
Published: April 2003

Films obtained from native cellulose synthesized by Acetobacter xylinum and from cellulose obtained from cuproammoniacal solutions (cellulose II) were morphologically characterized by studying the cis‐trans isomerization of azo dye Chrysophenine dispersed in their amorphous region. The kinetic measurements of the reaction showed that both films behave as glassy polymers in the temperature range explored (36–66°C). In going from native cellulose to cuproammoniacal cellulose, an increase of the isomerization rate was observed, revealing a more homogeneous distribution and likely larger extent of free volume in the amorphous phase of cellulose II.
Swellable hydrogel matrices for the release of the pendent chain‐linked active ingredients over extended time periods
Authors: Shah S. S. , Kulkarni M. G. , Mashelkar R. A.
Published: April 2003

Zero‐order release of the physically dispersed active ingredients from the glassy hydrogels has been explained in the past on the basis of the case II transport of the penetrant medium into the matrix. This communication reports the zero‐order release of the pendent chain‐linked p‐nitrobenzoic acid from glassy as well as swollen hydrogel matrices. This has been explained on the basis of the time‐dependent diffusivity of p‐nitrobenzoic acid resulting from the structural changes in the matrix accompanying the release. p‐Nitrobenzoic acid would be released from these systems at a constant rate for periods of up to 5 months. Implants of this type in which the drug molecule is linked to the polymer backbone through the pendent chain are potentially promising systems for drug delivery at a constant rate for extended time periods.
Infrared spectra of raw and chemically modified pineapple leaf fiber (annanus comosus)
Authors: Saha S. C. , Das B. K. , Ray P. K. , Pandey S. N. , Goswami K.
Published: April 2003

Infrared spectra of raw and chemically treated pineapple leaf fibers (PALF) have been studied using the KBr disk technique. Bands due to lignin and hemicellulose in the spectra of the fibers and their changes due to chemical (NaOH and NaCIO2) treatment have been discussed.
ESCA spectroscopy of poly(methyl methacrylate) grafted onto wood fibers
Authors: Kamdem D. P. , Riedl B. , Adnot A. , Kaliaguine S.
Published: April 2003

The incompatibility of hydrophilic wood fiber and hydrophobic polymers is the main difficulty with wood thermoplastic polymer composites. To overcome this issue, many researchers suggest grafting polymer onto wood fiber for improving the interfacial adhesion during mixing. A systematic ESCA study of chemi‐thermo‐mechanical pulp (CTMP) grafted fiber has been performed to provide chemical information about surface composition modification. The material analyzed included initial CTMP fiber, the pure polymer i.e., poly(methyl methacrylate) (PMMA) as reference material, and grafted fiber at different polymer loadings. Interest is focused on the carbon and oxygen spectra. Samples at high polymer loading or high grafting level have an O/C, C1, C2, C4, O1, and O2 intensities much similar to those of the PMMA but a little different since some wood fiber sites have still not fixed the polymer. ESCA spectra provide information on about 1–5 nm depth. The ESCA technique allows the monitoring of grafting polymer onto wood fiber as a surface phenomenon.
Copolymerization of turkish tall oil specimens with indene–coumarone. I. Studies on copolymerization of tall oil and indene–coumarone
Authors: Üstün Güldem , Civelekoǧlu Halidun
Published: April 2003

In this study copolymerization of Turkish tall oil specimens with technical grade indene–coumarone fraction of coal‐tar oils (bp 150–230°C) was investigated. The effects of temperature, the reaction time and reactant ratio on the reaction rate, and the composition of the resulting copolymer were determined. Based on these studies the optimal reaction conditions were established. Some main characteristics of these new type of tall oil/indene–coumarone copolymers determined were.
Properties of recycled high density polyethylene from milk bottles
Authors: Pattanakul C. , Selke S. , Lai C. , Miltz J.
Published: April 2003

The effect of virgin, high‐density polyethylene (HDPE)/recycled HDPE composition on the physical properties of the blends was investigated. The recycled HDPE was obtained from a postconsumer cycle of milk bottles. It was found that elongation at break was the mechanical property mostly affected by the content of recycled HDPE. Overall, however, the recycled HDPE from milk bottles was found to be a material with useful properties not largely different from those of virgin resin and thus could be used, at an appropriate concentration in virgin HDPE, for different applications.
Aqueous electropolymerization of polyacrylamide onto AS‐4 graphite fibers
Authors: Iroh J. O. , Bell J. P. , Scola D. A.
Published: April 2003

Constant current electropolymerization of acrylamide was initiated on the surfaces of AS‐4 graphite fibers. Electropolymerization was performed using an aqueous solution of acrylamide dissolved in dilute sulfuric acid solution. The progress of electropolymerization was followed by measuring the weight of polyacrylamide deposited onto the surfaces of a unit weight of graphite fiber per unit time. The rate of electropolymerization was obtained from the slope of the linear region of the polymer weight gain vs. electropolymerization time curve. The rate of electropolymerization onto AS‐4 graphite fiber surfaces was found to depend on the initial monomer concentration, sulfuric acid concentration, and current density raised to the powers of 1.67, 0.02, 0.54, respectively. Molecular weight measurements on the electropolymerized polyacrylamide were done by solution viscometry. Number average molecular weights of 430,000, 220,000, and 193,000 were obtained for polyacrylamide, electropolymerized at 1 mA/g, 50 mA/g, and 100 mA/g respectively, consistent with classical radical polymerization kinetics.
Viscoelasticity of thin adhesive layers as a function of cure and service temperature measured by a novel technique
Authors: Challis R. E. , Cocker R. P. , Holmes A. K. , Alper T.
Published: April 2003

This article presents a novel short‐pulse ultrasonic technique for measuring the relaxing planewave modulus in realistically thin films of adhesive polymer over wide‐frequency bandwidths (1 MHz to between 30 and 100 MHz). On‐line computational methods are used to correct for known system distortions, for the estimation of absorption, planewave phase velocity, and complex planewave modulus, all as functions of frequency. Where appropriate it is also possible to fit models of relaxation processes to the measured data. Detailed results are shown for nine structural adhesives designed principally for automotive applications. The changes that occur during cure, as a result of extended cure, and with variation in service temperature are demonstrated. This work concludes that the method provides convenient measures of engineering properties, provides the means to study the effects of cure and service conditions, and provides reliable measures of ultrasonic propagation parameters that can be used to investigate the testability of adhered structures by ultrasonic means.
Environmentally stable conductive polymers from bis(ethynylstyryl) benzene monomers
Authors: Walton Theodore R. , Gratz Roy F.
Published: April 2003

Several completely conjugated, all‐carbon–hydrogen acetylene‐terminated monomers, bis(ethynylstyryl)benzenes, were synthesized using the Wittig reaction with ethynyl‐benzaldehyde and xylyldiphosphonium salts. These prepolymers were thermally polymerized in the melt phase into thermally stable materials that can be further processed into conductive polymers having high stability to aggressive environments. Conductivity can range from that of an insulator to 10+2 s/cm. The room temperature conductivity is unchanged by extended exposure to boiling water or 500°C in an inert atmosphere. With proper design of the monomers' structures, they will melt sufficiently below the polymerization temperature to provide an adequate time in the liquid state for ease of processing. Once cured into the solid form, the materials are intractable and exhibit high stability to aggressive environments.
Phospholipid liposomes: Preparation, characterization, and uses
Authors: Nordmeier E. , Zeilinger C. , Lechner M. D.
Published: April 2003

Rhodopsin and cyclic guanosine monophosphat (cGMP)‐dependent channel proteins are isolated from the rod outer segment disk membranes of dark‐adopted bovine retinae and incorporated in liposomes, prepared by the method of detergent removal dialysis. The ion channel does not lose its transport function (release of Ca2+ ions by injection of cGMP) when incorporated in a liposome. Its activity depends on the degree of protein solubilization and the kind of detergent used. The highest activity is obtained by use of the detergent CHAPS. Shape, size, and size distribution of the liposomes are deduced from elastic and quasi‐elastic light scattering, the liposome number density by viscometry, and the photopigment or Ca2+ content by optical absorbance. The liposomes are heterogeneous with respect to size and shape. Small unilamellar liposomes (Rh = 80 nm) and a narrow size distribution (UD = 0.16) are obtained by using the detergent CHAPS. With increasing rhodopsin content per liposome, the hydrodynamic radius Rh increases and at the same time the shape of a liposome converts from a sphere to a prolate ellipsoid. The amount of entrapped Ca2+ per liposome reaches its maximum value when the Rhodopsin nearest‐neighbor distance approaches its minimum value. This suggests an intermembrane protein‐lipid‐protein lattice, which serves as barriere for Ca2+. The influence of temperature or total used Ca2+ content is less profound. Increasing temperature yields slightly smaller liposomes.
Vitrification and further structural relaxation in the isothermal curing of an epoxy resin
Authors: Montserrat S.
Published: April 2003

Isothermal curing of an epoxy resin based on diglycidyl ether of bisphenol A, using a hardener derived from phthalic anhydride, has been performed at curing temperatures between 30 and 130°C. Samples were cured isothermally at various intervals of time and analyzed by differential scanning calorimetry (DSC), the glass transition temperature Tg, and the conversion degree being determined by the residual enthalpy technique. The vitrification phenomenon and a further structural relaxation process, occurring at curing temperatures (Tc) lower than the maximum Tg (109°C), at which Tg equalizes Tc, have been studied at curing temperatures between 30 and 100°C. The structural relaxation process is analyzed by the endothermic peak that appears superposed on Tg in dynamic DSC scans. The area of this peak (Q) is a measure of the recovery enthalpy, and thus of the extent of the relaxation process. This process begins at higher curing times (tc) when Tc decreases because the vitrification of the system starts later. Both the enthalpy recovery (Q) and the temperature of the endothermic peak (Tm) increase with the annealing time (ta), calculated as the difference between tc and the time in which vitrification occurs, and tend to have a limiting value due to the fact that the system loses mobility when the free volume decreases during its asymptotic approach toward the metastable equilibrium state. Furthermore, the dependence of Q and Tm on ta at different Tc shows that the relaxation process in partially cured resins depends on the conversion degree of the system and consequently on the crosslinking density of the network.
Modification of poly(ethylene ether carbonate) polyols by transesterification
Authors: Harris Robert F.
Published: April 2003

Poly(ethylene ether carbonate) polyols are the reaction products of alkylene carbonates or alkylene oxides and CO2 with alcoholic initiators. These polyols can be modified with aliphatic hydroxyl compounds by transesterification reactions. The modifier becomes chemically bound into the polymer during reaction and modifies the properties of the polyol. The extent of reaction is very easy to follow by size exclusion chromatography. Molecular weight is controlled by the molecular weight of the reactants and by their stoichiometry. This transesterification process is compared to the previously described transesterification/advancement process. The transesterification process has the advantage of using milder temperature conditions and runs at ambient pressures. Therefore, modifiers can be used in the transesterification process that are unstable or undergo different chemistry under the reaction conditions of the transesterification/advancement process. Although the modifiers used in the transesterification/advancement process must be less volatile than DEG, more volatile modifiers can be used in the transesterification process. The two processes compliment each other, allowing the preparation of a wide variety of modified poly(ethylene ether carbonate) polyols. These polyols are useful in polyurethane applications.
The synthesis of microgels composed of polyelectrolytes
Authors: Fukutomi Takashi , Imori Yoshihisa , Saito Reiko , Shizu Koji
Published: April 2003

Microgels composed of dimethylaminopropylacryl amide (MAPA) or sodium salt of vinylbenzenesulfonic acid (VBS) were prepared by the crosslinking of primary polymers Poly(MAPA‐co‐acrylamide) or poly(VBS‐co‐acrylamide) with glutaraldehyde in aqueous solutions. Almost mono disperse spheric microgels with the diameter of 120 nm were obtained in the very wide concentration range (up to 5 w/v% for the former and 12 w/v% for the latter). In the copolymerization of MAPA and N‐methyloylacrylamide, microgel with the diameter of 120–140 nm was formed during polymerization.
Electrical properties of poly(butylene terephthalate)
Authors: Sandrolini Franco , Motori Antonio , Saccani Andrea
Published: April 2003

Direct current (dc) and alternating current (ac) electrical properties of semicrystalline poly(butylene terephthalate) (PBT) are investigated as a function of temperature and frequency.

Dc electrical conductivity measurements have been performed over the temperature range −75°C to 130°C and point out an essentially ionic mechanism of charge transport. Charge carriers are identified in protons supplied by ionization of carboxyl end‐groups after dissociation of the existing hydrogen bonds.

Dielectric constant and loss factor have been measured over the temperature range −100°C to 130°C and over the frequency range 10−6 to 106 Hz. Together with de measurements, they allow the detection of the α glass‐rubber and the β subglass relaxation processes, as well as an interfacial polarization of the Maxwell–Wagner–Sillars type.

Finally, the contour map of loss factor, summarizing the overall dielectric behavior of the polymer, is reported and discussed for electrical applications of PBT.
Bulk functionalization of ethylene‐propylene copolymers. IV. A theoretical approach
Authors: Greco R. , Musto P.
Published: April 2003

A theroretical model is developed for the bulk functionalization of ethylene–propylene co‐polymers on the basis of the molecular mechanism proposed in previous papers, with certain simplifying assumptions: (1) A steady state regime for all the radical species is hypothesized; (2) a number of termination reaction are neglected; (3) no monomer homopolymerization is allowed to occur. An analytical expression is derived in such a way. A comparison of the theoretical predictions with some experimental data, obtained varying the radical initiator concentration [I]o and the reaction temperature, T, shows satisfactory agreement at low values of [I]o and T. At higher values the molecular mechanism becomes more complex and the model is unable to fit the data.
Pultruded fiber‐reinforced poly(methyl methacrylate) composites. I. Effect of processing parameters on mechanical properties
Authors: Ma Chen‐Chi M. , Chen Chin‐Hsing
Published: April 2003

A feasibility study of pultrusion of fiber‐reinforced thermoplastic PMMA composite has been conducted using a proprietary method. Effect of processing parameters, preparation of methyl methacrylate (MMA) prepolymer on the mechanical properties (tensile, flexural strength and modulus, impact strength, etc.) of fiber‐reinforced PMMA composites by pultrusion has been studied. Processing parameters investigated included pulling rate, die temperature, postcure time and temperature, and filler content. From the study of Brookfield viscometer and FTIR spectrum the processing conditions can be defined. It was found from SEM photographs that the wetting out of fibers by PMMA resin was complete, and the fiber bundles were distributed evenly in the PMMA matrix. From the study of 1H‐NMR, GPC, and Brookfield viscometer, the conversion, molecular weight, and viscosity of MMA prepolymer data were obtained. From the DSC diagram, molecular weight measurement, and the rule of polymerization rate, the optimum die temperature was determined. It was found that the mechanical properties increase with increasing filler content and postcure temperature, and with decreasing die temperature and pulling rate.
Kinetic modeling of polymerization of butadiene using cobalt‐based Ziegler–Natta catalyst
Authors: Nitirahardjo Singgih , Lee Sunggyu , Miller Joseph W.
Published: April 2003

The reaction mechanism and subsequent kinetics for polymerization of butadiene using cobalt‐based Ziegler‐Natta catalysts have been investigated by many researchers. Kinetic models developed from these investigations can be used to predict the monomer conversion quite accurately; however, it is difficult to develop models that accurately predict the molecular weight as a function of time or conversion. In this paper, an attempt is made to model the reaction mechanism for the polymerization of butadiene using the cobalt octoate/diethyl aluminum chloride/water catalyst system with data taken from the literature. A dual active site mechanism is proposed and incorporated in a kinetic model. In this case, all reaction steps except the formation of byproducts step have two rate constants. The simulation results predict the molecular weight as a function of conversion and time better than results from previously published models.
Infrared investigations of sulfonated ionomer membranes. I. Water–alcohol compositions and counterions effects
Authors: Kujawski Wojciech , Nguyen Quang Trong , Neel Jean
Published: April 2003

FT‐IR spectra of Nafion 117, Raipore 1010, and PESS membranes loaded with different alkaline counterions and equilibrated with different liquid media were recorded by means of the attenuated total reflectance technique. The antisymmetric (vas) and especially the symmetric stretching vibrations (vs) of the sulfonate groups are affected by the presence of solvents in its local chemical environment. In the dry membrane the smaller the bare counterion, the higher the frequency of the symmetric vibration and the stronger the sulfonate‐counterion interactions in the contacting ion pair. After equilibration with pure water, ethanol, and 2‐propanol, the vs vibration shifts to a constant value corresponding to the solvated sulfonic grouping in the case of Nafion‐Li+ membrane. In the cases of PESS‐Li+ and Raipore‐Li+ membrane only water can cause a similar shift. The greater affinity of the Nafion membrane to alcohols can be attributed to the stronger acidity of the corresponding sulfonic acid. In water‐alcohol mixtures the variation of vs with water content indicates that the ion pairs in the PESS‐Li+ membrane are progressively dissociated and solvated by increasing amounts of water in 2‐propanol. Complete dissociation occurs at about 9 wt % water. Smaller shifts are observed with bigger cations, due to the weaker sulfonate‐cation interactions.
Hydrophilic and adhesive properties of methacrylic acid‐grafted polyethylene plates
Authors: Yamada Kazunori , Kimura Tomohiro , Tsutaya Hideyo , Hirata Mitsuo
Published: April 2003

Methacrylic acid (MAA) was grafted onto polyethylene (PE) surfaces by simultaneous irradiation with UV rays in the liquid phase to estimate hydrophilic and mechanical properties for MAA‐grafted PE plates. The amount of grafted MAA increased sigmoidally with UV irradiation time, and the higher grafted amount was obtained at higher monomer concentrations. With an increase in grafting of MAA, the wettabilities from the contact angles of water were enhanced and the refractive indices from the ellipsometry decreased. Though the contact angles remained constant above the grafted amount of 0.02 mmol/cm2, the refractive indices approached the value of PMAA around 0.009 mmol/cm2, indicating that the PE surfaces were fully covered with grafted PMAA chains. Then, at a fixed grafted amount, the grafted layer can absorb more water and the grafted PE plates possessed higher tensile shear adhesive strength, in case grafting was carried out at lower monomer concentrations. Surface properties depended on the density of carboxyl group at the surfaces of grafted layers, whereas adhesive properties depended on the structural properties of grafted chains as well as on the density of carboxyl group of the whole grafted layers.
Structure–property relationship of modified polypropylene–polycaproamide fiber
Authors: Grof I. , Sain M. M. , Durc̆ova Olga
Published: April 2003

The effect of the addition of polyamide on the structure and properties of polypropylene fiber has been studied. Although a good fiber is obtained with a composition containing only a very low concentration of polycaproamide in polypropylene, the increase in polyamide content decreases the drawing strength of the mixed polymer melt due to sudden lowering of melt viscosity and strength. The poor melt strength of the studied polymer mixture is attributed to increased heterogeneity induced in the system with increased concentration of polyamide. Use of an effective interphase modifier, maleic anhydride‐grafted polypropylene, however, was found to improve fiber properties of the studied polymer mixtures even with a very high concentration of polyamide as the dispersed phase. Thus, addition of a 1–4 wt % interphase modifier facilitates the formation of good fiber even with 30 wt % polycaproamide in the blend. This improvement is attributed to the improved dispersity of polyamide in the polypropylene matrix as well as improved phase compatibility due to the formation of a chemically modified polyamide during melt extrusion in the presence of maleic anhydride‐grafted polypropylene.
Synthesis of model latices for the study of coalescence mechanisms
Authors: Dobler F. , Pith T. , Holl Y. , Lambla M.
Published: April 2003

This work describes the synthesis of model latices devoted to the study of the influence of particle‐water and particle‐air interfacial energies on coalescence mechanisms. Core‐shell particles with the same diameter (≃ 2600 Å) and narrow size distributions were prepared. The core is a poly(styrene‐co‐butyl acrylate) (60/40 wt %) copolymer; it represents 90% of the volume of the particle. The shell is a poly(St‐BuA‐methacrylic acid) terpolymer with 10, 15, or 25 wt % MAA. The St‐BuA weight ratio in the shell is also 60/40. The amount of MAA in the shell determines the particle‐water or air interfacial energies. In order to limit the use of an emulsifier and to ensure a homogeneous particle surface layer, an inverted core‐shell synthesis was performed. The hydrophilic shell was prepared first and used as a seed for the synthesis of the hydrophobic core. For all three core‐shell latices, about 45% of the introduced MAA was found at the surface of the particles, which indicates that the core‐shell inversion was successful. The synthesis of the latices with 10 or 15 wt % MAA was relatively easy, whereas the particle size was difficult to control in the 25 wt % MAA latex synthesis.
Effects on properties of varying the cis/trans isomer distribution in polyurethane elastomers made with 1,4‐cyclohexane diisocyanate
Authors: Joseph Michael D. , Savina Michael R. , Harris Robert F.
Published: April 2003

Polyurethane elastomers have been made using 1,4‐cyclohexane diisocyanate (CHDI), 1,4‐butanediol (BDO) and a 2000 Mn polyether diol soft segment. The cis/trans isomer distribution of the CHDI was varied between 23% and 100% trans. This variation in isomer distribution had significant effects on the polyurethane's thermal and physical properties.

Decreasidng the trans CHDI content gives polyurethanes with lower hardness, lower thermal stability, higher Coefficient of Linear Thermal Expension (C.L.T.E.) values and decreased modulus values. Morphology studies showed good phase separation between the hard and soft segment blocks as well as a block copolymer morphology between the cis and trans CHDI/BDO blocks in the hard segment. The polyurethanes made were compared to polyurethanes made with MDI and H12MDI, the leading aromatic and aliphatic diisocyanates respectively.
Transport phenomena into and out of plasticized PVC sheets: The influence of sample history
Authors: Papaspyrides Constantine D.
Published: April 2003

Diffusional exchanges in plasticized PVC applications comprise a critical aspect of much of the published work, which has been intended to study plasticizer migration into simpler extractants, enabling the various parameters involved in migration to be studied in isolation. In this study the migration of dioctyl phthalate into petroleum oils is investigated with emphasis on prior sample history. Simultaneously, the penetration of the liquid environment into the sheets is monitored. Plasticized PVC samples were prepared containing different amounts of plasticizer. The samples are immersed in paraffin oil until the plasticizer concentration reaches a predetermined value. Afterwards the samples are immersed in white spirit and their migration behavior is compared with that of new samples containing this predetermined plasticizer content, i.e., excluding the prior desorption cycle. Under these experimental conditions the parameters studied include immersion time, immersion temperature, initial plasticizer content and specimen thickness. The results obtained, suggesting considerable restriction of the migration activity for the two‐stages specimens, are discussed in terms of surface‐depleted concentration profiles and structure rearrangement mechanisms.
Kinetics of silane grafting and moisture crosslinking of polyethylene and ethylene propylene rubber
Authors: Sen Achintya Kumar , Mukherjee Bibha , Bhattacharyya A. S. , De P. P. , Bhowmick Anil K.
Published: April 2003

Peroxide initiated graft copolymerization of vinyl trimethoxy silane (VTMO) and vinyl triethoxy silane (VTEO) onto polyethylene (PE) and ethylene propylene copolymer (EPR) was studied. The kinetics of grafting, studied by differential scanning calorimetry, are the same for all the systems and the activation energy for VTMO is 170 ± 4 KJ/mol. Activation energy for VTEO is 185 ± 5 KJ/mol. The VTMO and VTEO graft copolymers of PE and EPR were prepared by reactive processing in a Brabender extruder in the temperature range of 150–200°C. Moisture catalyzed crosslinking of the silane grafted copolymer was also studied. The influence of the structure of the catalyst, its concentration, moisture concentration, temperature, and time on degree and rate of crosslinking has been evaluated. Crosslinking reactions follow first order kinetics with respect to both catalyst and moisture concentration. Activation energy (Ea) of the crosslinking reaction has been determined as 65 KJ mol−1. The mechanism of grafting and crosslinking is discussed.
Copolymers of N‐vinylcarbazole with monomers containing carboxylic acid groups or carboxylic anhydride groups. II. Photoconductivity and composition
Authors: Wainwright M. , Griffiths J. , Guthrie J. T. , Gates A. P. , Murray D. E.
Published: April 2003

Copolymers of N‐vinylcarbazole containing olefinic monomers that possess carboxylic acid or anhydride functionality have been produced. The photoconductive properties of the copolymers were measured. Fluorimetry has been used to relate this photoconductivity to the copolymer composition. Photoconductivity was greatest in copolymers containing high percentages of vinylcarbazole. It is suggested that this is due to block copolymer formation, since the development of such blocks allows greater interchromophore overlap than would be possible with alternating copolymers, which exhibit low photoconductivity.
Synthesis and characterization of ionomeric poly(vinyl butyral)
Authors: Dasgupta A. M. , David D. J. , Misra A.
Published: April 2003

A route to synthesizing novel poly(vinyl butyral) ionomers (IPVB), via a condensation polymerization process, has been developed. In the process, ionic groups were permanently incorporated into the poly(vinyl butyral) backbone by using an ion‐containing aldehyde in addition to butyraldehyde during the acetalization of poly(vinyl alcohol). The resulting polymers demonstrated properties typical of ionomer systems, i.e., they behaved as “thermally reversible crosslinked thermoplastics” due to the presence of ionic associations present in the polymers. The ionic associations enabled the polymers to behave as crosslinked materials at ambient temperatures, whereas, at higher temperatures (processing temperatures), the ionic associations were lost, thus allowing the polymers to flow. Consequently, at ambient temperatures, the IPVBs demonstrated increased stiffness as determined from the storage modulus of the polymers, whereas, at higher temperatures, the IPVBs demonstrated moduli and stress‐relaxation properties comparable to those of conventional poly(vinyl butyral). The IPVBs were characterized by a number of techniques including, high resolution NMR spectroscopy (1H, 13C), dilute solution viscometry, dynamic mechanical analysis, and differential scanning calorimetry (DSC). Characterization was done on plasticized and unplasticized IPVBs.
Characterization of the glass transition using a microindenter
Authors: Rodriguez Ferdinand , Long Treva
Published: April 2003

The microindenter described here requires a very small sample (c. 10 mg), can be used with heating rates comparable to those in DSC (i.e., 10°C/min), and gives a large, clearly defined change at the glass transition. The essential features are a needle probe and a linear variable differential transformer (LVDT). By suitably controlling the force on the needle, the rate of heating, and the sample thickness, reproducible results can be obtained. The small sample size permits a relatively fast heating rate. Most mechanical tests (often using oscillating stress and strain) require large samples and a correspondingly long time for temperature equilibration to take place (ASTM D 4065). Another indentation test, the Vicat Softening Temperature (ASTM 1525) also uses a thick (3 mm) sample. Like the Vicat test, the present procedure is best suited to amorphous polymers. The application to plasticized samples of poly(methyl methacrylate) illustrates the utility of the method. The simple, rugged, and inexpensive nature of the apparatus makes it suitable for an under‐graduate experiment in a polymer laboratory course.
The effect of fumed silica upon the reaction of iron octoate and polysiloxanes
Authors: Ishida H. , Dunkers J.
Published: April 2003

Silica is a common component in silicone elastomer formulation. Silica is known to have surface hydroxyl groups and the reactions and interactions of these surface groups with various materials have been studied extensively in the past. It is believed that the iron octoate used to combat oxidative embrittlement in silicone elastomer formulations may also react with the surface of silica, specifically fumed silica. Dynamic mechanical spectroscopy (DMS), Fourier Transform Infrared Spectroscopy (FT‐IR), Electron Scanning for Chemical Analysis (ESCA), and Gel Permeation Chromatogrphy (GPC) were used to study the influence of untreated fumed silica and silica treated with dimethylsiloxane species on the iron octoate reaction. The rate of reaction was studied as a function of loading of silica. From analyzing rates of backbone scission and salt consumption, it is found that the iron octoate reacts preferentially with the surface of untreated fumed silica. Conversely, iron octoate appears to have no preferential reaction with the surface of the treated fumed silica.
The effect of castor oil on the structure and properties of polyurethane elastomers
Authors: Saxena P. K. , Srinivasan S. R. , Hrouz J. , Ilavský M.
Published: April 2003

Segmented polyurethane elastomers based on a mixture of castor oil and poly(propylene glycol), 4,4'‐diphenylmethane diisocyanate, and 1,4‐butanediol were prepared. The ultimate, thermal, dynamic mechanical behavior and morphology were studied. The use of castor oil shifts the main transition region of the soft phase to higher temperatures (the glass transition temperature Tg increases) improves abrasion resistance and the tensile strength. The multifunctionality of castor oil leads to the crosslinking of the soft segments and a decrease of the sol and swelling of elastomers.
Moisture sorption on the wetting behavior of poly(p‐phenylene terephthalamide) fibers in water and epoxy resin
Authors: Hsieh You‐Lo , Hartzell Mary Michelle , Barrall Geoff
Published: April 2003

The moisture sorption of poly(p‐phenylene terephthalamide) (PPTA) fibers and the effects of moisture on the wetting behavior of these fibers in water and in an epoxy resin were studied. The moisture regains in the Kevlar 149 fibers followed a third order polynomial dependency on increasing relative humidity at 23°C. When preconditioned at 0% relative humidity (R.H.), water wettability of Kevlar 49 fibers was superior to that of Kevlar 149 fibers. Resin wettability of the dried Kevlar 49 fibers, on the other hand, was lower than that of Kevlar 149 fibers. Wettability in water and resin of these two fiber types was affected differently by moisture. Exposure to 97% R.H. moisture level significantly lowered water wettability of Kevlar 49 fibers but did not affect the wettability of Kevlar 149 fibers in water. Resin wettability of Kevlar 49 fibers was improved upon exposure to moisture, but the opposite was observed on Kevlar 149 fibers.
Curing behavior of epoxy resin having hydroxymethyl group and different molecular weight distribution
Authors: Ohtsuka K. , Hasegawa K. , Fukuda A. , Uede K.
Published: April 2003

o‐Cresol novolac‐type epoxy resins having hydroxymethyl group were synthesized. These epoxy resins were cured with a mixture of 4,4′‐diaminodiphenylmethane and m‐phenylenediamine (molar ratio, 6:4) as a hardener. Effects of molecular weight distribution of epoxy resins on curing behavior were studied. Curing behavior of epoxy resins with hardener were examined by differential scanning calorimetery (DSC), and cure reaction parameters were obtained. Viscoelastic properties of the cured epoxy resins were studied by dynamic mechanical analyzer. It was found that the lower the average molecular weight of the epoxy resin, that is, the higher the concentration of hydroxymethyl group, the shorter the onset time of exothermal reaction, the higher the rate constant (k), and the lower the activation energy (Ea) were. It was also found that glass transition temperature (Tg) of fully cured epoxy resins was higher than those of fully cured general novolac‐type epoxy resins.
Grafting of poly(ethylene terephthalate) fibers with methacrylic acid using benzoyl peroxide
Authors: Sacak Mehmet , Sertkaya Filiz , Talu Muzaffer
Published: April 2003

The graft copolymerization of methacrylic acid onto poly(ethylene terephthalate) fibers, by the aid of benzoyl peroxide, have been investigated. The graft yield increased up to 85°C, and then decreased with the further increase in temperature. The maximum graft yield was obtained at benzoyl peroxide concentration of 4.0 × 10−3 mol/L. The increase in the concentration of monomer was found to increase the graft yield. The change in the graft yield was followed by the experiments carried out using different water/solvent mixtures. Also, the change in the properties of polye (thylene terephthalate) fibers grafted with methacrylic acid such as moisture regain, density, and diameter were investigated.
Visible laser lights in photoinduced polymerization. VI. Thioxanthones and ketocoumarins as photoinitiators
Authors: Fouassier J. P. , Wu S. K.
Published: April 2003

The efficiency of thioxanthones and ketocoumarins as photoinitiators has been checked in visible laser light‐induced polymerization reactions and discussed in terms of excited‐state reactivity (as revealed by time‐resolved laser spectroscopy). These compounds undergo fast electron transfer reaction in the presence of amines and onium salts. Transient absorption spectra and rate constants of the processes involved have been determined. The combination photoinitiator‐amine‐onium salt appears as very promising for the design of efficient photosensitive systems.
On the synthesis of ethyl‐2‐cyanoacrylate from waste residue
Authors: Denchev Z. Z. , Kabaivanov V. S.
Published: April 2003

The aim of the present study is to clarify some problems concerning the synthesis of additional quantities of ethyl‐2‐cyanoacrylate monomer (ECA) utilizing the waste residue (WR) from the large‐scale depolymerization of ECA oligomers. The composition of WR was established by GPC and IR spectroscopy. WR was found to consist mostly of diethyl dicyanoglutarate (DEDCG) and low molecular weight products of its condensation with paraformaldehyde (pFA). The DEDCG&‐pFA interaction was studied as a model, and the influence of DEDCG conversion on the average degree of polymerization (xn and xw) of the oligomers formed was also followed. On this basis, it was found that oligomer formation in condensation of WR with pFA is consistent with a stepgrowth mechanism, the polymer chain length being determined by steric hindrance and destructive reactions.
Analysis of plasma polymerization of benzaldehyde
Authors: Zhao Q. , Zhu Y. , Xu Y. , Yao Y. , Liu X.
Published: April 2003

Plasma polymerization of benzaldehyde was investigated mainly by infrared spectroscopy. The solubility, wettability, and heat stability for the formed plasma polymer are discussed. Benzaldehyde was plasma‐polymerized to yield films and/or powders. The products contained a large amount of carbonyl‐containing groups, such as aromatic ketone, aliphatic ketone, α, β‐olefinic ketone, and cyclic ketone. The chemical structures of formed polymer were strongly influenced by the plasma parameters and so were its solubility, surface wettability, and heat stability. The polymerization mechanism in plasma for benzaldehyde is discussed on the basis of the infrared analyses of the formed polymers at different plasma conditions.
Evaluation of cure conditions for polyimide thin films by pyrolysis–mass spectrometry
Authors: Johnson Eric T.
Published: April 2003

Films of a BTDA–mPDA–ODA polyimide copolymer (DuPont Pyralin PI‐2555) were spincoated onto silicon wafers and cured at either 300 or 350°C. Films cured at each temperature were then analyzed by various pyrolysis mass spectrometric methods. Low‐temperature pyrolysis mass spectrometry showed that polyimide films cured at the lower temperature contained more residual water and N‐methyl pyrrolidone solvent than did the films cured at the higher temperature. High‐temperature pyrolysis mass spectrometry of the two samples showed subtle differences in the mass spectrum of the polyimide pyrolysate under electron impact (EI) ionization conditions. Principal components analysis was used to differentiate between the EI mass spectra of the high‐and low‐temperature cured films. Several pyrolysis products, primarily aromatic hydrocarbon and heterocyclic fragments, were separated and identified by gas chromatography/mass spectrometry.