bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport of methylene chloride in poly(aryl‐ether‐ether‐ketone) (PEEK) resin and composite during alternate sorption/desorption cycles
Authors: Grayson Michael A. , Wolf Clarence J.
Published: April 2003

The transport of methylene chloride into PEEK resin systems following six successive sorption/desorption cycles was investigated. The sorption and desorption processes in neat PEEK with different morphologies and with varying degrees of crystallinity (from 1 to 29%) were compared to chopped‐carbon‐fiber and carbon‐fiber‐laminate composites. The amount of methylene chloride sorbed during an 80‐min immersion varied from less than 1 wt % in the composites to 37 wt % in the amorphous neat PEEK. During each cycle the solvent was desorbed at 95°C for 338 h. With the exception of the laminate, the sorption/desorption process is essentially independent of cycling. Furthermore, when the desorption processes are viewed in normalized form, i.e., fractional weight loss as a function of time, the desorption appears identical in all samples investigated. Although the maximum amount of solvent retained by the laminate was small, less than 0.1 wt % after the first cycle, it did increase to almost 0.15 wt % after 5 cycles.
Polyurethane–polypropylene blends
Authors: Petrović Zoran S. , Budinski‐Simendić Jaroslava , Divjaković Vladimir
Published: April 2003

Five series of blends were obtained by mixing five polyurethanes (PUR), based on poly‐propyleneoxide, MDI, and butanediol, with polypropylene (PP). The structure of PUR was varied by varying soft segment length (MW = 1000 and 2000) and soft segment concentration (50, 60, and 70%). It has been shown that interaction between PUR and PP was better in the case of PUR with the polyol of MW = 1000. The addition of lower molecular weight PUR produced an easy flowing material in the molten state, comparable with the “control rheology PP.” The morphology of the blends changed with PUR concentration. At 30% PUR the dispersed phase tended to agglomerate in the form of long cylinders. Mechanical properties generally were affected by the change of morphology.
Transparency of recycled polypropylene film
Authors: Shibayama Mitsuhiro , Imamura Ken‐Ichiro , Katoh Kuniyasu , Nomura Shunji
Published: April 2003

Turbidity of quenched polypropylene films was measured as a function of the film thickness and number of times film was recycled. Turbidity τ is defined by τ = (1/d) ln (Io/It), where Io and It are the intensity of the incident and transmitted lights, respectively, and d is the thickness of the sample. We assume here that most of the attenuation of light is due to scattering from superstructure in the film, such as spherulites, since no characteristic absorption bands are present in the wavelength region studied in this work. Turbidity varied sigmoidally with film thickness. It remained constant when the film thickness was lower than ca. 400 μm and then increased with film thickness and reached a plateau around 800 μm. When the film preparation was repeated, turbidity increased exponentially with the number of recycles. The spherulite size, however, was an invariant against the number of recycles and was dependent upon film thickness. The variation of turbidity with film thickness and the number of recycles is discussed.
Polymer–surfactant interactions in graft copolymer solutions
Authors: Steiner Carol A.
Published: April 2003

Graft copolymers composed of water‐soluble cellulosic backbones and > 0.4% (by weight) alkyl grafts are insoluble in water but soluble in surfactant solutions. Studies of the bulk viscosity and stability of polymer‐surfactant solutions at 49°C indicate that the mechanism for solubilization of the polymer is the incorporation of the alkyl side chains into surfactant micelles. The tendency for side chains to combine with micelles appears to depend at least in part on the geometry of the surfactant tail group such that surfactants containing straight‐chain tail groups solubilize alkyl side chains more readily than olefinic surfactants. The presence of small solutes near the surface of the micelle also inhibits incorporation of side chains from the polymer. Unsolubilized side chains remain in the aqueous phase of the solution, where they form thermally unstable intermolecular aggregates.
Isothermal sorption from finite baths: Effect of the boundary layer on sorption of diffusants by solids of various geometrical shapes
Authors: Etters J. N.
Published: April 2003

The literature reveals no equation that expresses the influence of the diffusional boundary layer on diffusion‐controlled sorption of dyes or other material by polymeric substrates from finite baths. In view of this mathematical void, a technique is proposed that approximates dimensionless sorption time as a function of fractional equilibrium uptake of diffusant by polymer, dimensionless dye bath exhaustion, and dimensionless boundary layer. The computational technique is based on relationships found in transitional kinetics and is shown to be applicable for sorption systems involving polymeric material of different geometrical shapes. To illustrate the technique, dimensionless half‐times of sorption are computed for the case of diffusant uptake by a cylinder.
Bench‐scale and pilot plant preparation of chemically modified polyester resins
Authors: Dairanieh Issam S. , Rasoul Firas A.
Published: April 2003

The laboratory preparation procedure of a recently developed unsaturated polyester resin was followed to prepare the resin on a large scale (10‐ and 200‐L pilot plant reactors). The process heating rate, reaction temperature, and agitator tip speed were kept constant on scale‐up. The resin was successfully reproduced and its properties were unchanged upon scale‐up. The effects of reaction temperature and inert gas flow rate on the polyesterification reaction rate were investigated. It was found that a 10°C increase in temperature or a 50% increase in the gas flow rate results in a 50% increase in the reaction rate.
A scheme for phase stability in liquid crystal polymers
Authors: Keller A. , Ungar G.
Published: April 2003

It is shown that conditions for realizing mesomorphic states in polymers are readily expressed in terms of the relative thermodynamic stabilities of the crystalline, liquid crystalline, and liquid phases. The simple scheme presented here has the merit of providing: (i) a unifying perspective over a wide range of mesophase behaviour that otherwise may be considered in isolation as disconnected occurrences, and (ii) a signpost for purposeful attainment (or enhancement) of the mesomorphic state also in the case of systems that are not normally considered liquid crystal forming. Examples are quoted from a range of materials, most comprehensively from polyethylene, bringing together diverse past and some rather striking new observations illustrating the validity and usefulness of the scheme.
Electrical conductivity of poly(2‐ethynylthiophene) and poly(2‐ethynylfuran) doped with electron acceptors
Authors: Gal Yeong Soon , Jung Bal , Choi Sam Kwon
Published: April 2003

The electrical conductivity of poly(2‐ethynylthiophene) (P2ET) and poly(2‐ethynylfuran) (P2EF) doped with electron acceptors such as iodine, bromine, and ferric chloride was investigated. The maximum electrical conductivities of P2ET and P2EF doped with iodine were 3 × 10−4 Ω−1 cm−1 and 5 × 10−3 Ω−1 cm−1, respectively. The electrical conductivity was nearly independent with increasing molecular weight. The spectral measurements such as UV‐visible, infrared, electron paramagnetic resonance, thermogravimetric analysis, and X‐ray diffraction were also carried out.
Tensile drawing behaviour of polyethylene terephthalate
Authors: Long S. D. , Ward I. M.
Published: April 2003

A wide range of polyethylene terephthalate fibres was prepared by melt spinning to different degrees of molecular orientation. The tensile drawing behaviour of these fibers was then studied, either by drawing over a heated cylinder at 85°C or by drawing over both a heated cylinder and a plate at 180°C. The mechanical properties and structure of the subsequent drawn fibres are discussed in terms of the network draw ratio, determined by matching true stress–strain curves for the drawn and initial melt spun fibres. It is shown that this procedure provides valuable insight into subtle differences in properties and structure that can arise from differences in processing routes.
Fluorine‐containing optical adhesives for optical communications systems
Authors: Maruno T. , Nakamura K.
Published: April 2003

Fluroinated epoxy resin adhesives containing diglycidylether of bisphenol AF (DGEBAF) with a fluorine content of 25.7 wt % are developed for fabrication of optical communications devices. These adhesives, formulated with a diluent of butanediol diglycidylether (BDDG) and a curing agent of polyether polyamine (Q694), can be cured at a curing temperature as low as 65°C and exhibit high transparency of more than 80% in the wavelength range of 0.5–1.3 μm. Moreover, they significantly reduce return loss at optical‐glass/adhesive interfaces because of the low refractive indices of ca. 1.52 and also improve heat durability of optical devices. They are successfully applied to submarine optical fiber transmission system.
Photoinitiated graft copolymerization of hydroxyethyl methacrylate onto cotton cellulose
Authors: Shukla S. R. , Rao G. V. Gopala , Athalye A. R.
Published: April 2003

The photoinitiated graft copolymerization of hydroxyethyl methacrylate (HEMA) onto cotton cellulose was studied using uranyl nitrate (UN) and ceric ammonium nitrate (CAN) photoinitiators. Optimization of various parameters of the graft‐copolymerization reaction viz., time, temperature, initiator, and monomer concentration, was carried out. The optimized conditions of grafting were employed to cotton samples swollen in zinc chloride as well as sodium hydroxide. Graft add‐on was found to be dependent on the nature of substrate and the concentrations of monomer and photoinitiator. UN was found to be the better photoinitiator, giving higher grafting with HEMA. The grafted samples showed initially decrease and then marginal increase in the moisture regain with increase in graft add‐on. The dye uptake of both direct and reactive dyes decreased with increase in graft add‐on.
Ultracentrifugal studies of the degradation of a fracturing fluid polymer: Hydroxypropyl guar
Authors: Budd Peter M. , Chakrabarti Sumana
Published: April 2003

Ultracentrifugal techniques have been employed to investigate the degradation of hydroxypropyl guar (HPG) solutions, and of gels formed with a delayed zirconium cross‐linker, by ammonium persulphate at 90°C. Molecular weights, M, for various samples of degraded polymer were determined by sedimentation/diffusion, and an empirical relationship was established between M and the sedimentation coefficient at a single, low concentration. This enabled the straightforward determination of M as functions of persulphate concentration, cross‐linker concentration, and time at temperature. It was shown that large decreases in M occur within the first hour at temperature, but that complete degradation is not achieved. It was further shown that, when a delayed zirconium cross‐linker is used, degradation may be less effective when gels are formed and degraded at high shear rates.
Surface and interfacial FTIR spectroscopic studies of latexes. I. Surfactant–copolymer interactions
Authors: Evanson Kevin W. , Urban Marek W.
Published: April 2003

Molecular level interactions between surfactants and copolymers as well as transient effects during latex film formation play an important role in latex technology. Photoacoustic (PA) and attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy were utilized for the characterization of interactions between sodium dioctylsulfosuccinate and ethyl acrylate/methacrylic acid (SDOSS/EA/MAA) copolymer in latex films at both the film–air and film–substrate interfaces. It is shown that the splitting of the asymmetric SO stretching normal vibrations of the SO groups in the presence of Na+ counterions occurs only when weak COOH acid groups of latex are present. The absence of the COOH groups either by neutralization of latex or intentional synthesis eliminates the SO···HO associations that are the primary source of the symmetry changes resulting in the splitting of the SO symmetric mode at 1050 cm−1 to two bands at 1046 and 1056 cm−1.
Amino acids as substrates for preparation of monomers with imide rings
Authors: Orzeszko Andrzej
Published: April 2003

The reaction of pyromellitic anhydride PMDA with some amino acids lead to monomers, which were used to synthesize new polymers. Application to glycine, D,L‐alanine and β‐alanine gave three bis‐acid chlorides. These are able to condense with glycols and diamines to yield a series of new copolyimides. Amino acids of two carboxylic groups D,L‐glutamic acid and D,L‐aspartic acid gave, in reaction with PMDA, two similar dianhydrides (4) and (5). However, the condensation with aromatic amines lead to two different compounds. It was proved that, under the conditions studied, formation of hexa‐membered imide rings was impossible while penta‐membered imides formed without difficulty. Thermogravimetric analyses of these polymers were also carried out.
Measurement of shear‐dependent intrinsic viscosities of carboxymethyl cellulose and xanthan gum suspensions
Authors: Young San Land , Shoemaker Charles F.
Published: April 2003

A rotational rheometer with cone and plate fixtures was used to measure the intrinsic viscosities of aqueous suspensions of xanthan gum and carboxymethyl cellulose (CMC). The reduced viscosities or hydrodynamic volumes of CMC suspensions increased with dilution. However, the reduced viscosities of xanthan gum suspensions decreased with dilution within the concentration range of 0.1–0.06% and increased with dilution within the concentration range of 0.04–0.01%. When the gums were suspended and diluted with 0.06 M sodium acetate, the reduced viscosities of all the xanthan gum and CMC suspensions decreased upon dilution. The intrinsic viscosities of xanthan gum and CMC suspensions decreased with increasing the shear rate, showing a dependence of hydrodynamic volume on shear rate.
Effect of physical annealing on the dynamic mechanical properties of a high‐Tg amine‐cured epoxy system
Authors: Wisanrakkit G. , Gillham J. K.
Published: April 2003

Physical annealing of a fully cured amine/epoxy system has been investigated using the freely oscillating TBA torsion pendulum technique. The material densifies spontaneously during annealing in an attempt to reach equilibrium, thereby changing material behavior. The dynamic mechanical behavior of a film specimen (Tg = 174°C, 0.3 Hz) and of a glass braid composite specimen (Tg = 182°C, 0.9 Hz) was monitored during isothermal annealing at sub‐Tg temperatures (ranging to 230°C below Tg); after annealing, the behavior was measured vs. temperature and compared with that of the unannealed state. Isothermally, the storage modulus (G′) of the film specimen and the relative rigidity (1/P2) of the composite specimen increased almost linearly with log time, whereas the logarithmic decrement (Δ) decreased with time. The isothermal rates of annealing were determined from the rates of changes in G′ and in 1/P2 for the film and composite specimens, respectively. In a wide temperature range between Tg and the secondary transition temperature, Tsec (≈ −30°C, 2.3 Hz by TBA), the isothermal rates of annealing at the same annealing time appeared to be the same. Thermomechanical spectra of the isothermally annealed material revealed a maximum deviation in thermomechanical behavior from the unannealed material in the vicinity of the annealing temperature. The effects of physical aging were the same for the film and composite specimens. Effects of sequential annealing at two isothermal temperatures on the thermomechanical behavior were also investigated; when the second temperature was higher than the first, the effect of only the high‐temperature annealing was evident, whereas the effect of annealing at both temperatures was revealed when the second temperature was lower than the first. Results suggest that physical annealing at different temperatures involves different length scales of chain segment relaxation and that the effects of isothermal aging can be eliminated by heating to below Tg.
A DSC study of curative interactions. I. The interaction of ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J.
Published: April 2003

The interaction between combinations of sulfur, stearic acid, and ZnO were studied by differential scanning calorimetry in the absence of rubber. The only reaction observed was between ZnO and stearic acid. A small amount of zinc stearate formed as soon as the stearic acid melted, but the solid product blocked further reaction, which was only completed at 154°C. Water played a major role in the reaction, and in the presence of water, the reaction went to completion at lower temperatures. Sulfur, too, affected the temperature of the ZnO/stearic acid reaction. The preparation of zinc stearate by a number of routes was investigated.
Refractive index of solutions containing poly(vinyl acetate) and poly(methyl methacrylate)
Authors: Bahr D. , Pinto J. C.
Published: April 2003

Refractive index measurements can be used successfully for on‐line evaluation of extent of reaction in solution polymerization reactors. For this reason, the refractive index of solutions containing tert‐butanol (TBOH), methyl methacrylate (MMA), vinyl acetate (VA), poly(methyl methacrylate) (PMMA), and poly(vinyl acetate) (PVA) were measured and a mathematical correlation was developed to fit the experimental data. The correlation can be extended to fit published data obtained with different solvents.
Hydrolytic stabilities of some polyurethane hydrogels
Authors: Lai Yu‐Chin
Published: April 2003

The hydrolytic stability of some polyurethane hydrogels derived from UV‐curable urethane prepolymers and hydrophilic monomers was addressed. It was found that polyurethane hydrogels derived from prepolymers with hydrophilic polypropylene glycol soft segments were not stable when the films were cast from nonpolar solvent, whereas they are stable if the films were cast from neat monomer mix. The causes for this instability were analyzed. Spectroscopic and gel permeation chromatographic studies of the water extractables suggested that improper curing of hydrophilic monomers with the urethane prepolymers in nonpolar solvent was mainly responsible for the instability phenomenon.
Effect of tensile deformation on the electrical conductivity of SRF black‐loaded SBR blend
Authors: Hassan H. H. , Khairy S. A. , El‐Guiziri S. B. , Abdel‐Moneim H. M.
Published: April 2003

Styrene butadiene rubber (SBR‐1502) was mixed with 100 phr superreinforcing furnace (SRF) black. The obtained rubber vulcanizate was subjected to electrical conductivity measurements at different values of tensile deformation. The log V vs. log I graphs showed two distinct linear stages, the slope of which is nearly independent of the tensile deformation in the first stage and decreases with tensile deformation in the second stage. On the other hand, the tensile deformation was found to have an appreciable effect on the electrical conductivity. It decreases sharply as the sample is suddenly strained and then increases exponentially with time. An empirical formula describing this behavior is suggested.
Blends of thermotropic polyester with poly(phenylene oxide)
Authors: Limtasiri T. , Isayev A. I.
Published: April 2003

A thermotropic liquid crystalline polymer (LCP) based on wholly aromatic copolyesters based on hydroxynaphthoic and hydroxybenzoic acid was melt‐blended with a thermoplastic poly(phenylene oxide) by corotating twin screw extruder. Rheological properties, temperature transitions, dynamic and mechanical properties, and electron microscopy study have been performed. Rheological study indicated significant viscosity reductions with increasing LCP content leading to ease of processing. From the differential scanning calorimeter (DSC) and dynamic mechanical thermal analyzer results, these blends showed incompatibility for the whole range of concentrations. Mechanical properties were found to be slightly improved at low LCP and dramatically improved at above 50% LCP contents. In addition, impact strength was significantly increased up to two times after adding 10% LCP into the matrix. The morphology of blends was affected by composition. Droplets and stubby fibrils structures caused lower tensile strength, whereas fibrillar structure improved this property.
On the synthesis and properties of some saturated and unsaturated esters of 2‐cyano‐2, 4‐pentadienoic acid
Authors: Denchev Z. Z. , Kabaivanov V. S.
Published: April 2003

The preparation and properties of some new saturated and unsaturated esters of 2‐cyano‐2,4‐pentadienoic acid (CPDA) are described. A comparison is also made with the known CPDA monomers synthesized under identical conditions. It was found that the monomer yields are dependent on the structure of the corresponding CPDA esters. This fact was explained with solvatation effects, occurring during the isolation procedures. The base‐catalyzed anionic bulk polymerization of CPDA esters was studied by means of spectral methods. The data indicated that during the homopolymerization 1,4‐addition of monomer molecules takes place to give a steric copolymer consisting of 1,4‐cis and 1,4‐trans structural units. The ability of poly‐CPDA esters was also followed to form crosslinks at room and higher temperatures.
Effects of temperature, repeated exposure, and aging on polybutylene permeation by organic chemicals
Authors: Park J. K. , Bontoux L.
Published: April 2003

The permeation parameters, partition coefficient and diffusion coefficient, were obtained for polybutylene (PB) with toluene using a gravimetric method. A PB sample was repeatedly exposed and desorbed, and the partition coefficient and diffusion coefficient were measured. Permeation parameters were also measured at different temperatures. The results were compared with those obtained from a 12‐year‐old PB pipe sample, which had experienced structural failure. Tests at an elevated temperature of 45°C failed to simulate the effect of polymer aging, whereas repeated sorption/desorption tests produced permeation parameters compatible with those of a 12‐year‐old PB pipe in service.
Diffusion coefficients of direct dyes in chitosan
Authors: Carlough Mark , Hudson Sam , Smith Brent , Spadgenske Dawn
Published: April 2003

Diffusion coefficients for direct dyes (C. I. Direct Red 81, Green 26, Blue 75, and Black 22) in Chitosan films are determined to be 4.48 × 10−11 to 4.54 × 10−10 cm2/at 60°C and pH 9. A method for producing chitosan films is described.
Vinylic graft copolymers of cellulose. I. Effects of monomer concentrations and crystallinity index of cellulosic substrate on grafting vinyl acetate onto cotton
Authors: Flaqué C. , Montserrat S.
Published: April 2003

Graft copolymerization of vinyl acetate (VA) and methyl acrylate (MA) on cotton cellulose was initiated by the Ce (IV) ion, and ungrafted vinylic polymer was separated from the graft copolymer by acetone extraction. The influence of the ratio aqueous initiator solution volume/monomeric volume (Vaq/Vmon), vinyl acetate volume/methyl acrylate volume (VVA/VMA), and the cellulose crystallinity index (CI) on the grafting reaction were studied. To modify the crystallinity of cellulose, native cotton was treated with NaOH in the concentrations 10, 15, and 20% (mercerized). The viscosimetric average molecular weight (Mv), the polymerization degree (PD), and the crystallinity index proposed by Nelson and O'Connor (CI) were determined for native and NaOH‐treated cotton. The polymeric side chains grafted were separated from the cellulose backbone by acid hydrolysis in 72% H2SO4. The viscosimetric average molecular weight (Mv) was determined, and the number of vinylic chains per cellulosic chain (graft frequency, GF) were calculated. The grafting percentage, %G, was higher for most amorphous cellulose and for a higher methyl acrylate percentage (%MA) in monomeric reaction mixtures (VA‐MA). The Vaq/Vmon ratio that yields the highest %G was 70/30. The increase of the %G with the %MA in the VA–MA monomeric mixture seems to be due to both an increase in the length of vinylic grafted chains (as shown by its Mv) and the number of grafted chains (GF). The increase in the %G when the crystallinity index (CI) of the cellulosic substrate decreases seems to be due to an increase in the length of the vinylic grafted chains, but not to an increase in the number of grafted chains, since the Mv increases and GF decreases when the CI of cellulose decreases.
Emulsion copolymerization of vinylidene chloride and butyl methacrylate, 83:17 in mol %
Authors: Lee Ki‐Chang , El‐Aasser M. S. , Vanderhoff John W.
Published: April 2003

Seven 35% solids, (83 : 17 in mol %), vinylidene chloride (VDC)–butyl methacrylate (BMA) copolymer latexes were prepared at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization processes: one batch (G), one seeded batch (F), and five seeded semicontinuous polymerizations of five different monomer feed rates ranging from 0.27 (A) to 1.10 (E) wt %/min. All of the emulsion polymerizations gave stable latexes of almost 100% conversion with negligible coagulum and narrow particle size distributions. The kinetic studies of seeded semicontinuous polymerization A–E showed that the rates of polymerization (Rp) were controlled by the monomer addition rates (Ra), and polymerizations A–D (0.27–0.79 wt %/min) were under monomer‐starved conditions; polymerization E (1.10 wt %/min) was in near‐flooded condition. Significant differences were found in the physical and mechanical properties of the latex films, depending on the mode of monomer addition. Infrared spectroscopy, 13C solid‐state NMR spectroscopy, X‐ray diffraction, the Tg and Tm values by DSC, dynamic mechanical spectroscopy, and tensile strength measurement of the latex films post‐heat‐treated for 30 min at 70°C or aged for several months at room temperature demonstrated that batch polymerizations F and G gave copolymers of heterogeneous composition and a crystalline character. In contrast, semicontinuous polymerizations A–E gave copolymers of more uniform composition and an amorphous character.
Investigation of structural and mechanical properties of copper‐chloride‐doped nylon‐6 films. I. Structure
Authors: Kelkar D. S. , Bhat N. V.
Published: April 2003

Structural changes in nylon‐6 film on doping with various concentrations of copper chloride (0.5, 1.25, 2.5, 5, and 12.5% w/w) have been investigated. Methods such as density measurement, analysis of infrared spectra, and wide‐angle X‐ray diffraction analysis have been employed to study these structural changes. It is found that doping up to 1.25% of copper chloride increases the crystallization of nylon‐6 in the α‐crystalline form. Further increase in the dopant concentration, however, gradually changes the crystal structure to hexagonal γ form with reduction in the total crystallization.
Preparation and characterization of polyelectrolyte copolymers containing methyl methacrylate, and 2‐hydroxyethyl methacrylate. II. Polymers based on dimethylaminoethyl methacrylate
Authors: Wen Shao , Yin Xiaonan , Stevenson William T. K.
Published: April 2003

Co‐ and terpolymers containing dimethylaminoethyl methacrylate (DMAEMA), methyl methacrylate (MMA), and 2‐hydroxyethyl methacrylate (HEMA) were prepared by solution polymerization, and characterized by dilute solution viscometry and proton and carbon‐13 nuclear magnetic resonance spectroscopy. Polymers were prepared containing 75, 60, 40, 25, and 10 mol % DMAEMA but with differing levels of MMA and HEMA. Polymer solutions were titrated under nitrogen to obtain variations of pKb with alpha (the extent of protonation of the DMAEMA residue). From these experiments, we were able to show that, as expected, the cooperative nature of the ionization process decreased as the level of DMAEMA in the polymer was reduced from 75 mol % to 10 mol %. By comparing polymers containing similar amounts of DMAEMA monomer, we were also able to show that base strength increased with the polarity of the uncharged portion of the polymer, in other words, that polymers containing higher levels of HEMA were stronger bases than polymers containing higher levels of MMA. This effect was rationalized by assuming that higher contents of the more polar HEMA monomer facilitated the coil expansion that accompanied the process of ionization, thus increasing charge separations at corresponding values of alpha and increasing base strength.
Kinetics of sol‐to‐gel transition for poloxamer polyols
Authors: Wang P. , Johnston T. P.
Published: April 2003

Kinetics of gelation for aqueous solutions of poloxamers 407 and 288 were determined using pulse shearometry. The principle of this method for determining the shear modulus of a semisolid was based on generation of a torsional force that is transmitted through the poloxamer sample at discrete time intervals. Three distinct linear phases were observed for the log dynamic shear modulus (G′) vs. time profiles as poloxamer 407 and 288 solutions of varying concentrations were allowed to passively warm at room temperature to a temperature exceeding the sol‐to‐gel transition temperature, Tm. The beginning of the second exponential phase coincided with the onset of the gelation process as determined by visual observation. Although gelation appeared visually to be complete at the beginning of the third exponential phase of the log G′ vs. time profiles, this last exponential phase may indicate the rate of formation of the polymer network. A comparison of poloxamer 407 [30% (w/w); Tm = 10.9°C] and poloxamer 288 [37% (w/w); Tm = 11.1°C] would suggest that the concentration of poloxamer required to achieve approximately the same gelation temperature for poloxamers having a similar ratio of poly(oxypropylene):poly(oxyethylene) units decreases with increasing molecular weight of the poly(oxypropylene) hydrophobe contained in the copolymer. Results of these preliminary studies suggest that the gelation process was significantly (p < .05) more rapid for poloxamer 407 at a 30% (w/w) concentration compared to a 30% (w/w) solution of poloxamer 288 when the poloxamer solutions were allowed to passively warm at room temperature. In addition, it appears that the rate of gelation for the poloxamer solutions studied was dependent on the rate of heat transfer through the polymer solution.
Processing–crystallization kinetics–morphology relationships in injection molding of PP and GFRPP
Authors: Chu Wen‐Yen , Tai Horng‐Jer , Chen Leo‐Wang , Chu Line‐Hwa
Published: April 2003

The dynamic crystallization model proposed in our previous work was applied to the simulation of crystallization kinetics and morphology of PP and PP/glass fiber composite (GFRPP) in injection molding process. The cooling rate was very rapid in the processing, either in the core or in the skin region of thin disc part, so that the crystallization would take place at low temperatures and the size of spherulites was small. However, the ultimate crystallinity of PP could always be obtained since the crystallization rate of PP was extremely fast. Prediction of the crystallization morphology from the dynamic model agreed well with the experimental observation, which indicated that our proposed model could give a good estimation of processing–crystallization kinetics–morphology relationships for PP and GFRPP.
Electron‐beam irradiation‐induced grafting of acrylonitrile onto polyethylene
Authors: Mori K. , Koshiishi K. , Masuhara K.
Published: April 2003

Low‐ and high‐density polyethylene (PE) films were grafted with acrylonitrile (AN) by electron beam prior to irradiation. The distribution of graft chains over the cross section of the sample film was analyzed in terms of the distribution of nitrogen atoms contained in the AN by means of an electron probe microanalyzer (EPMA), and graft sites were studied in relation to the effect of grafting temperature on the percent graft and the oxygen permeability of the sample films. It was found that diffusion of AN into the film was the rate‐limiting step in the grafting process, thus restricting the grafting to the surface of the film in the initial grafting stages. However, the grafting shifted to the center of film as the graft process proceeded, until a uniform distribution of graft chains was observed across the entire film thickness. High‐density polyethylene (HDPE) was found to display a higher percent graft than did low‐density polyethylene (LDPE), and percent graft tended to increase with increasing grafting temperature. On the other hand, film oxygen permeability decreased with increasing percent graft, but this decreasing trend decreased with increasing percent graft. These findings suggest that the grafting is initiated by radicals trapped in the amorphous phase near the crystalline regions and at the surface of crystallites and that graft chains grow toward the amorphous regions. As for the radicals contributing to graft polymerization, it appears that AN permeates deeper near the crystalline surface and that graft chains grow from these sites.
Effect of orientation on melting of isotactic polypropylene
Authors: Ibhadon A. O.
Published: April 2003

The effect of uniaxial orientation on the melting of a commercial grade of isotactic polypropylene has been investigated by thermal analytical techniques. Orientation progressively shifts the onset of and the observed melting point to higher temperatures and increases the peak heights of differential scanning calorimetric (DSC) endotherms. The increase in melting point with orientation is attributed to the increase in configurational entropy of the extended melt into which the polymer crystallites melt.
Polyurethane elastomers studied by the Mooney–Rivlin equation for rubbers
Authors: Spathis G. D.
Published: April 2003

A series of poly(ester–urethane) block copolymers were prepared via a two‐step polymerization process. The prepolymer composition was kept constant in all the samples, while the NCO/OH ratio during extension was varied from 0.9 up to 1.2. By this way, chemical and physical cross‐links were constructed into the materials. Equilibrium stress–strain measurements have been carried out for the examination of the elastomeric behavior of the materials tested. Calculation of an extra entropy term resulting from the network deformation is based on a first‐principles derivation of the distribution function, taking into account a new type of network constraints. The process yields the Mooney–Rivlin equation and the constant C2 as a function of physical cross‐links.
Residual birefringence of amorphous polymers for optical‐disk substrates
Authors: Shindo Y. , Saito M. , Iwatsuka Y. , Hasegawa H.
Published: April 2003

Based on the Mueller matrix approach, we have successfully designed and constructed a highly sensitive instrument for measuring optical birefringence (LB) by using a polarization modulation method and phase‐sensitive technique. Our instrument can measure the retardation of a sample up to 10−2 radian. Using this instrument, we have measured the residual birefringence of thermosetting resins, CR‐39 resin and epoxy resin, for opticaldisk substrates. CR‐39 resin results are summarized as follows: (1) Annealing is very effective in reducing LB of samples; (2) samples prepared from raw material 2 (monomer purity, 96%, oligomer, 4%) have smaller LB than those from raw material 1 (monomer purity, 99.9%); and (3) annealed samples prepared from 2 satisfy the requirement on LB to be used as optical‐disk substrates. For epoxy resin: (1) “Second curing” largely reduces LB of samples; (2) “slow cooling” is more effective in reducing LB of samples than “fast cooling;” (3) after the second curing, cutting does not induce any residual stress birefringence in samples; and (4) slow‐cooled samples have good optical properties to be used as optical disk substrates.
Solution process of suspension poly(vinyl chloride) in cyclohexanone by means of a viscometer
Authors: Szewczyk Pawel , Gruszka Marianna , Bortel Krzysztof
Published: April 2003

To study the structure of grains of suspension poly(vinyl chloride) (PVC), the authors applied a capillary viscometer for cyclic measurements of viscosity of the PVC–cyclohexanone solution during dissolution of the polymer. Final concentration of the solution was 0.5–1.0 g/100 cm3 and the measurements were made at temperatures of 313, 333, 353, and 373 K. It was found that at 353 K, a temperature close to the glass transition temperature of PVC, the curve describing changes of viscosity vs. the dissolution time has a pronounced maximum. It follows from a preliminary analysis of the obtained results that this maximum corresponds to the viscosity of a PVC solution in which average apparent mass is many times larger than true average molecular mass of the studied sample. It mans that into the solution enter single chains and some formations, called microdomains in the literature, that are composed of tens of macromolecules. The microdomains disintegrate later to single macromolecules.
Cellulose acetate: Interactions with aqueous phenol and a transition temperature of about 20°C
Authors: Murphy Andrew P.
Published: April 2003

Sorption of aqueous phenol onto powdered cellulose acetate can be described with the Langmuir equation at phenol concentrations below 0.10M. Unacetylated hydroxyl groups are probably the primary sites where phenol hydrogen bonds. As the phenol concentration is increased (> 0.13M), additional hydrogen bonding may occur with the carbonyl oxygens on the primary acetate groups, followed by secondary acetates and the beta glucosidic oxygens. Sorption at higher concentrations shows a negative slope for the Langmuir equation, perhaps caused by crowding and partial blocking of sites. Extrapolations to higher phenolic concentrations using the equation from the negative slope isotherm and plotting N versus °C reveal two lines with a point of intersection at 0.77M. Because of the increase slope above 0.77M, cellulose acetate may be dissolving in phenol. At concentrations below 0.10M, two processes were identified using a Van't Hoff plot (9.33 ± 0.30) × 103 and (−1.36 ± 0.18) X 103 J/mol. The initial moisture present in the polymer appears to be an important experimental variable and a transition temperature of 20.1 ± 0.2°C, probably due to polymer swelling, is reported.
Gas transport in poly(alkoxyphosphazenes)
Authors: Hirose Takuji , Mizoguchi Keishin
Published: April 2003

The permeability of four structurally related poly(alkoxyphosphazenes), three isomers of poly(dibutoxyphosphazenes) (PBuP), and poly(di‐neopentyloxyphosphazene) (Pneo‐PeP), to 13 gases has been determined by the time‐lag method. Systematic variations in chemical structure have shown a large effect of side chains on permeabilities and permselectivities. The permeability of poly(di‐n‐butoxyphosphazene) (Pn‐BuP) is of the order of 10−8 cm3 (STP) cm/(cm2 s cmHg) for many gases, and the value for a large gas is higher than that for a smaller one. For small gases such as He and H2, poly(di‐sec‐butoxyphosphazene) (Ps‐BuP) is as permeable as Pn‐BuP, but its diffusivities for larger gases such as Xe and C3H8 are about one order lower than those of Pn‐BuP. While the permselectivity of Pn‐BuP is determined by the solubility, that of Ps‐BuP depends on both the diffusivity and solubility factors. The property of poly(diisobutoxyphosphazene) (Pi‐BuP) is intermediate between them. These polymers are constitutionally identical, and the only difference is the arrangements of carbons in the side groups. As the side chains become bulky, the permeability decreases, whereas the permselectivity increases. Further decreases of diffusivity and then permeability are observed for Pneo‐PeP, whose side groups have one more methyl group than does Pi‐BuP. But the solubility data are not much different from other three polymers and the diffusivity factor becomes more significant in permselectivity. The diffusivity depends on the polymer structure much more than does the solubility. The relationships between chemical structure and gas diffusivity and solubility are discussed.
Interpenetrating polymer networks of castor oil polyester and poly(methyl methacrylate)
Authors: Murthy C. N. , Patni M. J. , Deshpande D. D. , Kudchadker A. P. , Mehta M. H. , Ankleshwaria B. V.
Published: April 2003

The physical and mechanical properties of interpenetrating polymer networks (IPNs) and semi‐I IPNs of the castor oil polyester network and poly(methyl methacrylate) were investigated. In the semi‐I IPNs, the second component was a copolymer of poly(methyl methacrylate) and polystyrene (PS) or poly(methyl methacrylate) and poly(n‐butyl acrylate) (PnBA). The dynamic mechanical properties indicated the semi‐I IPNs to be more compatible than the IPNs. The degree of molecular mixing was higher than that for IPNs. The impact strength showed a gradual increase with the increase in the percentage of PS or PnBA in the copolymer. The effect of the copolymerization of the second component on transparency was investigated. The transparency of the semi‐I IPNs increased with the increasing composition of PnBA, but reduced with the increasing composition of PS. These results are discussed in light of existing theories.
Effect of water in vapor‐phase photografting of vinyl monomers on polymer films
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

The effect of water added to monomer being supplied in the vapor phase was investigated in photografting on sensitizer‐coated polymer films at 60°C. A pertinent quantity of water accelerated sharply the photografting irrespective of the nature of monomer (acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, and acrylonitrile), film substrate (low‐density and high‐density polyethylenes, polypropyrene, nylon 6, and polyester), and sensitizer (benzophenone and anthraquinone). Water was found to increase the molecular weight of the grafts, which was studied on acrylonitrile‐grafted nylon 6 film. It was confirmed that water exhibited an accelerating action on photoinduced solution polymerizations of acrylic acid and methyl methacrylate, resulting in an increased molecular weight of the both polymers. These results suggest that the accelerating action of water may result from the restriction of chain termination.
Effect of polycarbonate molecular weight on precrack hysteresis energy in determining its ductile‐brittle transition
Authors: Chang Feng‐Chih , Hsu Hon‐Chun
Published: April 2003

The distinctive ductile‐brittle transition behavior of pseudoductile polymeric materials such as polycarbonate (PC) has been discovered to be closely related to the precrack hysteresis loss energy. The higher molecular weight (MW) PC with higher ductility also results in higher precrack hysteresis energy and therefore greater precrack plastic volume under condition of constant loads. If the precrack plastic volume exceeds a critical value, crack initiation thereafter will propagate within the domain of the plastic zone and results in ductile fracture. The deformation displacement is closely related to the precrack plastic volume, and the critical displacement actually determines the critical plastic volume. The higher molecular weight polycarbonate with higher entanglement density is able to withstand earlier crack initiation more effectively. Toughening plastics, such as rubber modification, is simply the result of delaying or retarding the crack initiation and allows the precrack plastic zone to grow over its critical value. A model of crack criterion based on precrack plastic zone is proposed to interpret the ductile‐brittle transition phenomenon.
The relationship between the physico‐mechanical properties and the filler concentration in the HD polyethylene‐dispersed filler system
Authors: Bozveliev L. G. , Kosfeld R. , Uhlenbroich Th.
Published: April 2003

The relationship of 10 basic physico‐mechanical properties and the concentration of the filler is investigated through narrow filling intervals of seven different composite series containing various types of HD polyethylene and different grades of kaolin. A variety of mixing techniques for the preparation of the composites is used, and testing is carried out by applying different techniques and conditions. The investigations show that, in all cases when an identical mixing technique is applied for a given series of composite formulations, the relationship linking the physico‐mechanical and dynamic‐mechanical G′, G″, and tan δ properties with the concentration of the filler is not a monotonous curve, and displays a multiextermal character. We propose as one possible explanation that a periodic change in the free volume and the content of crystal polyethylene phase exists, as a function of the filling. The nonmonotonous character of the changes of properties is related to the proposed mechanism for the change of the physical structure of composites, which are composed of filler particles coated with n monolayers of polyethylene crystallites, when, as filling continues, periodically new types of filler particles are formed. The nonmonotonous character of the relationship between the properties and the concentration of the filler should be taken into consideration when these relationships are approximated or expressed in a mathematical‐analytical form, especially when high amounts of fillers (more than 20 vol %) are used.
The effect of polymer additives on the performance of a two‐roll coater
Authors: Kang Yao‐Ting , Lee Kwong‐Yang , Liu Ta‐Jo
Published: April 2003

The effect of polymer additives on the performance of a two‐roll coater has been examined experimentally. The coater consists of a rigid steel roll and a deformable roll with polyurethane surface. Newtonian coating solutions and solutions with polymer additives were used as test fluids. Both forward and reverse coating operations were studied. It was found that for the forward coating operation, the shear‐thinning behavior of the polymer solutions can reduce the coating thickness, but the fluid elasticity can increase the coating thickness significantly and can also destabilize the coating flow. For the reverse coating operation, a small amount of polymer additives can effectively increase the wipe ratio.
Effect of new additives on the ultrasonic attenuation and mechanical properties of styrene–butadiene rubber
Authors: Aziz A. W. , Younan A. F. , Eid A. M.
Published: April 2003

The change in attenuation of longitudinal ultrasonic waves has been measured as a function of frequency and temperature for styrene–butadiene‐rubber (SBR) mixed with Ismacorr 141 as plasticizer and antioxidant. Analysis of the results showed relaxation processes and the activation energies for these processes were calculated and found to be related to the plasticization of samples. Also the velocity of the ultrasonic longitudinal waves through different samples was measured. The effect of Ismacorr 141 on the physical and mechanical properties of SBR was also studied.
Studies on the preparation and characterization of poly(4‐vinylpyridine) microgel. I. Preparation with polymer emulsifier
Authors: Ma Guang Hui , Fukutomi Takashi
Published: April 2003

Poly(4‐vinylpyridine) (P4VP) microgels with a narrow size distribution have been prepared by a special emulsion polymerization method. This is to say that P4VP, to which cation and double‐bond were introduced with iodomethane and chloromethylstyrene, by quarternization reaction was used as a polymer emulsifier. Divinylbenzene was used as a crosslinking agent. It was found that the microgel became larger with the increase in monomer concentration, and became smaller and softer with the enhancing emulsifer/monomer ratio. Microgels, with the diameter of between 70–700 nm, were obtained by varying the monomer concentration from 1.0 wt % to 5.0 wt %, and by varying the emulsifier/monomer (unit/unit) ratio from 0–10.0 mol %. Compared with conventional emulsion polymerization with surfactant or hydrophilic monomer, this method provides an advantage in that monoingredient microgels can be obtained.