bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal expansion properties of particulates based on the concept of mesophase
Authors: Theocaris P. S. , Varias A. G.
Published: April 2003

The determination of the cubic thermal expansion coefficient of a two‐phase particulate is presented in this paper. The model described is based on the well‐known Kerner's model and takes into account the existence of mesophase, which constitutes a boundary layer between inclusions and the matrix in the composite. This layer is assumed as created by the substance of matrix during the preparation procedure of the composite, and it includes areas of imperfections around and near the inclusions. The influence of this layer on the effective properties of the composite has been proved to be significant. In order to take into consideration the influence of mesophase a spherical shell with the average properties of this layer is interposed between the spherical inclusion and the matrix. The evaluation of the average elastic and thermoelastic properties and also of the extent of mesophase is succeeded by considering the two‐term unfolding model, introduced previously, for describing the change of the elastic modulus of the mesophase layer of fiber‐reinforced and particulate composites. The two‐term unfolding model was, in this paper, extended to incorporate the mode of variation of the thermal expansion coefficient and the bulk modulus in the mesophase. The model was applied to a polyurethane rubber filled with particles of sodium chloride, and its predictions were found to be in good agreement with the experimental data.
Properties of syndiotacticity‐rich poly(vinyl alcohol) thin film in water. II. Effect of the annealing temperature on the extension of thin film in water
Authors: Yamaura Kazuo , Matsuzawa Shuji
Published: April 2003

The effect of the annealing temperature on the extension of thin film of syndiotacticityrich poly(vinyl alcohol)(PVAVTFA) derived from vinyl trifluoroacetate is investigated in water. For the samples annealed at the temperature of above 125°C, the time of initiation of elongation and Young's modulus increase steeply with the elevation of annealing temperature, and the time required to maximum elongation and the maximum elongation ratio decrease quietly. The elongation ratio at break during the elevation of temperature of water decreases with the increase in the annealing temperature, that is, from 6.5 to 1.5. Reversely, the temperature at break increases from 85 to 97°C, but it is minimum at the annealing temperature of 125°C.
Chain extenders for polyesters. I. Addition‐type chain extenders reactive with carboxyl end groups of polyesters
Authors: Inata Hiroo , Matsumura Shunichi
Published: April 2003

Effective chain extenders for linear polyesters were investigated among some bis‐heterocycles, which were capable of coupling carboxyl terminals of the polyesters through addition reaction. Consequently, 2,2′‐bis(2‐oxazoline), 2,2′‐bis(5,6‐dihydro‐4H‐1,3‐oxazine) and N,N′‐hexamethylenebis(carbamoyl‐2‐ oxazoline) were found to be the most effective chain extenders. Starting from a poly(ethylene terephthalate) (PET) having intrinsic viscosity ([η]) of 0.66 and carboxyl content (CV) of 46 eq/106 g, one could obtain polyesters with [η] of above 1.0 and CV of below 5 eq/106 g in the presence of the chain extenders. Typical reaction condition for the coupling of PET was heating PET under atmospheric nitrogen above its melting temperature with 0.5 mol % of a chain extenders only for several minutes. Bis‐2‐thiazolines showed no effect under the condition investigated, while in case of bis‐2‐imidazolines definite degradation was observed. Bis‐N‐acylaziridines and bisiminocarbonates resulted in some gell formation, indicative of side reactions.
Fatigue mechanism of fiber‐reinforced polypropylene swollen by oil
Authors: Iisaka K. , Namai Y.
Published: April 2003

Fatigue mechanism was investigated for the fiber‐reinforced polypropylene (FRPP) swollen by a small amount of oil. The curves of applied cyclic stress (S) vs. logarithm of cycles to failure (N) shifted into smaller values of S and N, respectively, by adding oil into the polymer and with increasing a test temperature. The endurance limiting stress (σe) for the swollen FRPP, defined as the stress at a long lifetime, became much the same as the one for the swollen unfilled polypropylene, though the former was considerably larger than the latter for the breaking strength measured in standard bending test. The activation energy and the activated volume, which have been determined by the Eyring's model from the S–N curves at higher stress levels, suggest that the introduction of a small amount of oil into the polymer lowers a motional unit associated with a fatigue process from 30 to several repeat units. The major decrease in σe by swelling can be explained in terms of the crack–nucleation theory. It is indicated that this decrease yields from the change in the stress–concentration factor.
Carboxymethyl‐cellulose‐grafted with dextrin synthesis and solution rheology
Authors: Sikkema D. J.
Published: April 2003

Carboxymethyl cellulose grafted with dextrin (CMC‐g‐dextrin) products are easily accessible by reacting freshly prepared CMC with the acid alcoholysis product from starch and glycerol monochlorohydrin. The success of the grafting reaction depends on adjusting the alkalinity of the grafting reaction mass prior to addition of the dextrin chlorohydrin reagent. In all, less NaOH should be applied than theoretically necessary for all chlorine substitution. In some cases the products show interesting rheology at very low shear, but rather CMC‐like rheology or more Newtonian behavior than CMC at shearing rates over a few reciprocal seconds. These results reinforce the credibility of the view that natural polysaccharide gums with unusual rheologies derive their special properties from their well‐defined substitution pattern rather than from their overall degree of substitution with (oligo)saccharide units.
Solvent power effect on graessley's time constant in concentrated polystyrene solutions
Authors: Quadrat Otakar , Mikeŝov´ Jana , Prokopová Eva
Published: April 2003

Results of our measurements of polystyrene solutions and those reported in the literature demonstrate the common dependence of Graessley's relaxation time on the product of concentration and molecular weight, irrespective of the solvent power and its viscosity, and of temperature. Such behavior is in agreement with the conclusions reached in our previous paper, namely, that the shear stress dependence of viscosity of this polymer in solvents differing considerably in viscosity and solvent power may be unified by plotting relative viscosity against the product of velocity gradient and Rouse's relaxation time.
Effects of poly(methyl methacrylate‐co‐n‐butyl acrylate) on the properties and processing behavior of poly(vinyl chloride)
Authors: Lee Yu‐Der , Cheng Kung‐Chun
Published: April 2003

Random copolymers of methyl methacrylate/n‐butyl acrylate with a BA content of 0–50% and M̄v = 0.16–4.04 × 106 were synthesized and evaluated as a processing aid (PA) for poly(vinyl chloride) (PVC). Their effects on the processability and properties of PVC were investigated with respect to the composition, molecular weight, and the amount of the copolymer added. It was found that the fusion rate of PVC could be improved (i) by increasing the amount of the copolymer used, (ii) by increasing the butyl acrylate content in the copolymer, and (iii) by lowering the molecular weight of the copolymer. The effect of molecular weight, composition, and amount of copolymer on the ultimate mechanical properties of PVC was investigated. The presence of copolymer did not affect the impact strength. However, the tensile strength and elongation at break were improved, particularly at high temperature (125°C). It was also found that the “plate out” phenomenon of PVC could be significantly reduced in the presence of the processing aid.
The behavior of spiral angle ϕ and the angle of crystallite dispersion α of normal cottons with stress
Authors: Kalyanaraman A. R.
Published: April 2003

It is well known that the cotton fiber consists of microfibrils which in turn do have crystalline and amorphous regions. The crystallites are arranged in the form of helices, and with stress the helical configuration changes. This paper examines the configurational changes that occur in the helix and makes it clear that the amorphous regions of the microfibrils are the source of these changes.
Matrix resins based on bismaleimide–1,2‐polybutadienes
Authors: Gupta Alka D. , Kumar Devendra
Published: April 2003

Improved thermally stable matrix resins have been obtained by the incorporation of 1,2‐polybutadiene in 4,4′‐bismaleimidodiphenylmethane. The thermal curing was performed at 185–195°C for 2.5 h and at 230–235°C for 45 min to give tough crosslinked polymers. The thermal curing reaction was monitered using FT‐IR and differential scanning calorimetry. Thermogravimetric analysis of the cured resins have shown improved thermal stability up to 490–480°C both in air and nitrogen atmospheres. The char yield obtained in nitrogen at 800°C was in the range of 50–49%. Graphite cloth laminates were prepared and tested. The laminates showed improved tensile strength over to parent bismaleimide. 1,2‐Polybutadiene was hydrogenated using 10% palladized‐charcoal. The resulting polymer was characterized by using IR and 1H‐NMR, which showed reduction of 15% pendent vinyl double bonds.
Chemical engineering aspects of reactive dyeing
Authors: Sada Eizo , Kumazawa Hidehiro , Ando Tetsuo
Published: April 2003

The process of dyeing with reactive dyes was formulated on the basis of diffusion of dye species in the pores of polymer phase accompanied by fixation reaction with fiber substrate on the pore wall incorporating hydrolysis of dye species. The effect of the hydrolysis on the fractional fixation was numerically analyzed under various levels of bath ratio and degree of mixing in the dyebath. The simulation model was presented to yield the unlevelness arisen from lack of uniformity of degree of mixing in the dyebath.
Shrinkage and retractive force of drawn isotactic polypropylene during heating
Authors: De Candia F. , Romano G. , Vittoria V. , Peterlin A.
Published: April 2003

The semi‐crystalline isotactic polypropylene was drawn to λ = 6,7,8,9,11 and the drawn samples heated to temperatures between 40 and 160°C. The shrinkage of the sample with λ = 7 and 11 was measured as function of time and temperature. The effect of shrinkage is higher with the smaller draw ratio as if the drawing increased the thermal stability of the sample. With fixed ends the drawn samples were heated at a constant rate and the retractive stress observed. It increases with λ and the heating rate. At the same drawing ratio λ, the curves of the retractive stress show a maximum and subsequently drop to a substantially smaller value that increases with the draw ratio and the distance of the highest temperature of the heating from the melting point of the sample. The cooling curve of the first run almost coincides with the heating and cooling curve of the next runs if one does not surpass the maximum temperature of heating of the first run. The time dependence of the retractive stress after an inital maximum decays more rapidly to the limiting value σ∞ (T) the higher the temperature of the experiment. The limiting value σ∞ (T) rapidly decreases with T and increases with λ.
Uniaxial orientation of linear low density polyethylene
Authors: Pezzutti Jose L. , Porter Roger S.
Published: April 2003

Only a few reported studies have involved the uniaxial orientation of LDPE and even less on LLDPE. It is our purpose to report on characteristics of uniaxially oriented films of LLDPE that contribute to property development. The LLDPE has been coextruded at 25 and at 80°C layered as ribbons within longitudinally split billets of HDPE. The LLDPE so drawn was characterized by thermal analysis, birefringence, elastic recovery, and wide angle X‐ray measurements. As a result, we can conclude that the drawing of LLDPE at the lower temperature produces a relatively high content of monoclinic crystals; the orientation behavior of LLDPE is similar to that of HDPE. The molecular network formed by entanglements and crystals reduces the draw to a maximum below 15.
Radiation‐induced emulsion polymerization of vinyl acetate in a pilot plant reactor I. Recycle flow reactor
Authors: Challa R. R. , Drew J. H. , Stannett V. T. , Stahel E. P.
Published: April 2003

A number of successful radiation polymerization of vinyl acetate in emulsion have been carried out in a modular stainless steel flow pilot plant. In a recycle mode, the system was utilized for extremely accurate kinetic measurements and experimental verification of model restrictions such as plug flow, lack of post irradiation effects and differential reactor behavior. Experimental conditions were explored to minimize contaminant, primarily oxygen, inhibition, and the tendency for this formulation, essentially an adhesive, to build up on the reactor walls. Industrial scaleup of such a prototype system appears attractive.
Preparation of polymer latex films by a flash casting technique
Authors: Chainey M. , Wilkinson M. C. , Hearn J.
Published: April 2003

Conventional film casting methods have proved unsuitable for the preparation of thin (10–100 μ) films from surfactant‐free polymer latices. A flash casting technique has been devised and successfully employed to cast films from a wide range of surfactant‐free homopolymer, copolymer and core‐shell polymer latices. Essentially, the method involves spraying the latex at a specially designed hotplate, the surface of which is coated with a thin layer of PTFE. The hotplate is maintained at a temperature between 393 and 473 K. When sufficient thickness of film has been built up, the hotplate is switched off and allowed to cool to the temperature at which the film is to be removed. For homogeneous latex films, the optimum temperature range for removal lies in the region of the glass transition temperature of the polymer concerned. Where this is below ambient, the appropriate cooling mixture is placed in a slush bath, situated to the rear of the hotplate, thereby cooling the hotplate to the correct temperature. The film is removed by gently peeling it from the surface. The surfaces of the films appeared smooth to the naked eye, but the sprayed surfaces of freshly prepared poly(n‐butyl methacrylate) films were rough when examined by scanning electron microscopy. The surfaces smoothed out on ageing, resembling those of solvent‐cast films after one months storage.
Effect of silicon comonomers on thermal degradation of polystyrene
Authors: Gupta D. C. , Sharma R. C.
Published: April 2003

The thermal degradation of the following organosilicon copolymers: styrene–vinylmethyl‐diacetoxysilane, styrene‐2‐methacryloyloxypropoxytrimethyl silane, styrene–(dimethyl) siloxane–methylvinylsiloxane) diol and hexamethyl cyclotrisiloxane–styrene–hexamethyl cyclotrisiloxane was investigated. The techniques of thermogravimetry, thermomechanical analysis, and differential scanning calorimetry (DSC) were used. The initial decomposition temperature for all the copolymers except styrene–siloxane block copolymers was less than that for polystyrene irrespective of the nature of the silicon comonomer. Integral procedural decomposition temperature of copolymers was higher than that for polystyrene except styrene‐2‐methacryloyloxy propoxytrimethyl silane copolymers which were showing lower (IPDT) values. Styrene–siloxane copolymers were found to be most thermally stable. Variation in the glass transition temperature and probe displacement under stress is related to the polarity of the silicon moiety in the styrene copolymers.
Radiation‐induced graft copolymerization of methacrylic acid onto polypropylene fibers VI. Dyeing behavior
Authors: Mukherjee A. K. , Gupta B. D.
Published: April 2003

The dyeing behavior of polypropylene‐g‐polymethacrylic acid fibers prepared by graft copolymerization of methacrylic acid onto polypropylene fibers by gamma‐ray irradiation was evaluated for their dyeability characteristics using two basic dyes, rhodamine B and methylene blue. An increase in the dye uptake and moisture regain with the increase in graft content was observed. Such behavior has been attributed to the hydrophilicity imparted to polypropylene fiber by the presence of polar carboxyl groups in polymethacrylic acid grafts. The dependence of rate of dyeing on the percentage graft was evaluated. The diffusion coefficient of the fiber showed an increase with the increase in graft content and has been related to the structural changes occurring during grafting.
Study on the curing behavior of resol. IV. Comparison of the curing behavior of resols prepared with either sodium hydroxide or barium hydroxide
Authors: Fukuda Akinori , Hasegawa Kiichi , Horiuchi Hikaru
Published: April 2003

Curing behaviors of two kinds of resols prepared by the reaction of phenol (1 mol), formaldehyde (1.2 mol), and either sodium hydroxide (0.02 mol) or barium hydroxide (0.01 mol), were examined at 120°C by means of Curelastometer, IR spectroscopy, THE extraction, and GPC. Gelling and curing speeds of the resol prepared with barium hydroxide as catalyst (BR) were faster than with sodium hydroxide (NR). The amount of hydroxymethyl groups in BR also decreased more rapidly with an increase in the cure time than that in NR by IR spectrometry. Similar results were confirmed by THF extraction and GPC. It is recognized in the curing of both resols that relatively higher molecular weight compounds gel rapidly and that, after major components in the resol have changed to gel, low molecular weight compounds still remain in the resol as sol state. It is inferred from GPC that NR differs from BR in the molecular weight of the compounds which exist prior to gel formation, namely, the molecular weight of the compounds in BR is smaller than that in NR.
Phase separation in rubber‐modified thermoset resins: Optical microscopy and laser light scattering
Authors: Naé Hemi N.
Published: April 2003

Phase Separation of a prereacted rubber in di‐, tri‐, and tetrafunctional epoxy systems is discussed. Optical microscopy and laser light scattering are used to characterize the morphology and dimensios of the rubbery domains. Systems without rubber are transparent while systems containing 2%, 4%, 6%, and 8% and rubber exhibit distinct phase separation. The average domain size is about 1 μm In the 8% systems the particles are larger and in the trifunctional system the rubbery domains are in the shape of shell and core. Laser light scattering proves that the scattering particles are in the core observed in the optical micrographs. The difference in morphologies is explained by the difference in the chemical structure of the epoxy resin and the rubber content. Thermodynamic considerations and solubility parameters show that the di‐ and tetrafunctional systems have similar enthalpies of mixing while the trifunctional system is much more incompatible with the rubber.
Shear modification of polyethylene
Authors: Ram Arie , Izrailov Lora
Published: April 2003

Polymers like LDPE can be modified by applying a shearing process for an extended period. As a result the melt elasticity is reduced, as evidenced by the decrease in extrudate (die) swell at the exit of a capillary and onset of melt fracture. Melt viscosity was also slightly reduced; melt flow index (measured in short capillary) is highly increased. At the same time, melt density rises. All these parameters vary mostly for LDPE grades that exhibit the highest degree of long‐chain branching. It was confirmed that the intrinsic viscosisty of the polymer samples was essentially unaffected, so that chain scission may be ruled out. Moreover, the process itself is shown to be reversible as the initial parameters were recovered by special treatment, due to heating or solvation. The mechanism of shear modification is believed to consist of disentanglement of temporary couplings betwen long branches. The practical utilization of this process will be pursued, as well as the scientific understanding of structuring entangled branched chains.
Viscoelastic character of poly(ethylene oxide) in aqueous solutions: Effect of shear rate, concentration, salt, and anionic surfactant
Authors: Lance‐Gomez E. T. , Ward T. C.
Published: April 2003

A technique useful for estimating the viscoelastic properties of dilute solution poly(ethylene oxide) was developed. With this technique, the effect of concentration, shear rate, presence of salt and/or anionic surfactant, and molecular weight on the viscoelastic properties in dilute solution were determined. Differences in the viscoelastic properties of commercial grade materials were observed. An explanation for the differences in salt and surfactant solutions based on formation of a weak ionic network is presented.
Mechanical properties of films of poly(vinyl alcohol) derived from vinyl trifluoroacetate
Authors: Yamaura Kazuo , Tada Masuo , Tanigami Tetsuya , Matsuzawa Shuji
Published: April 2003

In order to study the influence of the stereoreguralities of polymer chains on the mechanical properties of films of poly(vinyl alcohol) (PVA)(VTFA) derived from vinyl trifluoroacetate, the strength of the film was measured. In the case of undrawn PVA(VTFA) films, Young's modulus and strength at break were the smallest at the annealing temperature of about 100°C. It is considered to be due to the melt of small microcrystals and the increase in mobility of chains in amorphous parts. Young's moduli of undrawn PVA(VTFA) films were in the range of 1.50–3.75 GPs and the values were higher than that (0.17–0.36 GPa) of undrawn film of commercial PVA with the low concentration of syndiotacticity and the high concentration of head‐to‐head bounds. In the case of drawn, annealed PVA(VTFA) films, the maximum Young's modulus was about 20 GPa.
The density and composition of polyimide surface layers
Authors: Chauvin C. , Sacher E. , Yelon A.
Published: April 2003

Density measurements as a function of polyimide film thickness have revealed that the surface layers, each 1.5 μm in thickness, have a density lower than that of the bulk by a statistically significant 1%. Infrared measurements have confirmed that this is due to the presence of isoimide in these surface layers: because of its nonlinear nature, this impurity structure causes a decrease in the measured density.
Semi‐ and fully interpenetrating polymer networks based on polyurethane‐polyacrylate systems. IX. Properties of an isomerically related interpenetrating network
Authors: Hourston D. J. , Huson M. G. , McCluskey J. A.
Published: April 2003

Two polyurethane–poly(vinyl acetate) interpenetrating polymer networks of differing composition were synthesized and certain physical properties investigated. The results are compared with semi‐1‐interpenetrating polymer networks of the same system as well as with, where appropriate, polyurethane‐poly(methyl acrylate) interpenetrating polymer networks. Dynamic mechanical analysis clearly indicated phase separation for both compositions. The poly(vinyl acetate) glass transition showed a shift to lower temperatures accompanied by a shift to higher temperatures of the polyurethane transition. Such shifts indicate a certain extent of mixing. Electron microscopy confirmed phase separation and for a material with 20% by weight of polyurethane indicated that both components are continuous. This latter material also had a higher tensile strength and elongation at break than the corresponding poly(vinyl acetate) homopolymer. At 60% by weight of polyurethane the stress‐strain characteristics are those of a reinforced rubber. Certain modulus–composition theories, and, also, sonic velocity measurements were consistent with these morphological conclusions.
Thermal behavior of polyethyloxazoline
Authors: Keskkula H. , Paul D. R.
Published: April 2003

Polyethyloxazoline (PEOx) is a new water‐soluble, thermoplastic polymer. It has a glass temperature of 56°C which increases to about 72°C on storage at room temperature. This increase is a manifestation of physical aging, and it occurs relatively fast with PEOx in comparison to other polymers. Also, the extent of this aging, as measured by the amount of enthalpy relaxation, is high for PEOx. It was shown that PEOx can be brought to 320°C without reduction of glass temperature, indicating an exceptional thermal stability.
Optimal periodic control of a continuous “living” anionic polymerization. I. Theoretical study
Authors: Frontini G. L. , Eliçabe G. E. , Couso D. A. , Meira G. R.
Published: April 2003

Within certain limitations, this work shows that the production of polymers with any prespecified number average chain length and polydispersity is theoretically feasible when “living” anionic polymerizations are carried out in continuous stirred tank reactors (CSTRs) which are under optimal periodic forcing of the feed flows. The optimal periodic control problem was solved adopting a suboptimal objective function and a novel iterative numerical procedure. When the objective function is minimized in order to reduce the time average polydispersity, then the operation tends to become a sequential semibatch process. Conversely, if the objective is to maximize these variables, then the reagent concentrations inside the reactor tend to be 180° out of phase. Different periods of oscillation must be selected depending on whether the required average polydispersities are above or below the steady state value of 2. The greatest flexibility in the MWD control is obtained with fast kinetics, and, in this case, average polydispersities between 1.06 and 9.2 may be required.
Studies on structural transformation of the sytrene‐grafted polyethylene film and fabric — grafting behavior and cavity formation mechanism
Authors: Hsiue Ging‐Ho , Huang Wen‐Kuei
Published: April 2003

A new approach to prepare hydrophilic porous membranes is presented. Films and fabric made of polyethylene were grafted with styrene by simultaneous γ‐irradiation. The grafting behaviors of fabric are quite different from bulk films which exhibit the well‐known gel effect in styrene–methanol mixture solutions. The grafting rate for fabric increased monotonically with monomer concentration, and no maximum appeared on dilution with methanol. The copolymer films were further sulfonated to prepare hydrophilic membranes. Surface structure of membranes and fabrics were examined with optical and electron microscopy. For the fabric, the original smooth surface turned into rugged surface with different sizes of cavities. For membranes, the buldgelike bubbles are found when swollen with water. These bubbles changed into cavities after drying in vacuum at elevated temperature. The mechanism for the formation of such a structure is discussed. The electrical resistance of such membrane was low enough to be useful as battery separator.
Selective permeation of o‐, m‐, and p‐isomers of benzene derivatives through polymer membranes based on cyclodextrin complexation in the bulk aqueous solution
Authors: Anzai Jun‐Ichi , Kobayashi Yutaka , Ueno Akihiko , Osa Tetsuo
Published: April 2003

Transport behavior of several aromatic compounds through a poly(vinyl chloride)membrane and poly(vinyl alcohol)‐poly(ethylenimine) composite membranes was studied in the presence of cyclodextrin in the aqueous solution. o‐Isomers of nitrophenol, nitroaniline, and iodophenol were effectively separated from their mixture of regio isomers based on the preferential complexation between cyclodextrin and the m‐ and p‐isomers over the o‐isomers. Pumping of p‐nitroaniline across the membrane was also observed by addition of cyclodextrin. The results were explained as a consequence of the selective complex formation between cyclodexarin and substrate and the low membrane permeability of the complexes.
Orientation behavior of ethylene diamine‐treated cottons with stress
Authors: Kalyanaraman A. R.
Published: April 2003

The decrystallization of natural cotton with Ethylene Diamine Treatment is well known. This paper analyzes the variation of X‐ray orientation with stress on ethylene diamine‐treated cotton fibers. For cotton fibers in the natural state, the elongation varies uniformly with the applied stress. It has also been pointed out by earlier work that the X‐ray orientation does not vary uniformly with increase in applied stress. With ethylene diamine treatment on natural cottons, the above trends are reversed and this is reported in the present investigation. This paper also indicates a possible explanation to support the above observation.
Studies in interaction between polyvinyl pyrrolidone and stilbene fluorescent compounds. Part I: Interaction with individual compounds
Authors: Sheth Geeta N.
Published: April 2003

Interaction between polyvinyl pyrrolidone (PVP) and two stilbene‐type fluorescent compounds has been examined from the results of emission, excitation, and ultraviolet absorbance measurements. Results obtained indicate preferential interaction of the trans form of the fluorescent compound with PVP resulting in complex formation and increase in fluorescence due to such complex formation. However, at higher concentrations of PVP in the aqueous phase the cis form also forms a complex which has no fluorescing characteristics. The calculated values of free energy change indicate weak bonding between both the fluorescent compounds and PVP. Fluorescent compound‐binding capacity as well as the number of monomers of PVP combined remain more or less constant in the range of molecular weights of PVP studied.
Electron‐microscopical investigation of the morphology of segmented polyurethanes
Authors: Foks J. , Michler G.
Published: April 2003

Segmented polyurethanes obtained by two‐step synthesis were studied by electron microscope on specimens prepared as replicas from the brittle surface of the polymer and on thin sections cut with a cryo‐ultramicrotome. Each of the specimens showed two different kinds of dispersed phase. Information obtained on morphology complemented each other. The continueous phase observed on the thin section directly by microscope showed no structure of its own and was similar in all polymers investigated, whereas the surface of the brittle fracture showed two kinds of continuous phase.
Dielectric properties of polymers containing dispersed TCNQ salts
Authors: Kita H. , Okamoto K. , Mukai S.
Published: April 2003

Tetracyanoquinodimethane salts have been incorporated into insulating polymers to raise their dielectric constants. Cast films prepared from mixtures of insulating polymers and tetracyanoquinodimethane salts in a solvent show a high dielectric constant (>20). The dielectric constant of the films varies with the tetracyanoquinodimethane salts. High values were attained with the films containing high‐conducting tetracyanoquinodimethane salts. These values remain constant over a range of frequencies (102–104 Hz). Dissipation factors and electric strength values of the films are also reported.
Effect of comonomer content and annealing on morphological changes in acrylic copolymers and fibers
Authors: Kulshreshtha A. K. , Garg V. N. , Sharma Y. N. , Dweltz N. E.
Published: April 2003

A better understanding of internal microstructure is necessary to understand various properties of acrylic fibers, such as dyeability, mechanical properties, and comfort. In the present paper, the application of x‐ray methods for the investigation of fiber microstructural parameters, namely, crystallinity and crystallite size, is demonstrated. Effect of comonomer incorporation on acrylic copolymer microstructure is assessed in the present work. Influence of annealing aftertreatment on the changes in structure is investigated using the evidence presented by x‐ray and DSC studies. Introduction of small amounts of a comonomer (methyl acrylate, MA) results in diminishing crystallinity. Annealing of acrylic copolymers causes the onset of an intramolecular cyclization, as well as an increase in segmental mobility; both these factors lead to an increase in crystallinity and crystallite size. With increasing comonomer content, the exothermic peak in the thermogram is found to shift toward higher temperatures. Some evidence is presented that shows the effect of spinning process variables on acrylic fiber microstructure. The results and findings of the present work have been interpreted in terms of a two‐phase structure for acrylic fibers.
Permeation of N‐butane, propane and ethane through ethylcellulose
Authors: Casur Ertugrul , Smith Theodore G.
Published: April 2003

The permeation of n‐butane, propane, and ethane in ethylcellulose has been measured over a pressure range from 25 to 200 mm Hg and over the temperature range from 30 to 70°C. The permeation and diffusional time lag of each of the three gases in ethylcellulose is pressure dependent. Transport of the gases through ethylcellulose can be described by the partial immobilization model. It was found that, in general, the Langmuir‐mode species diffusion coefficients are lower than the Henry's law species diffusion coefficients. The logarithm of diffusion coefficients at zero penetrant concentration varies linearly with the square of the molecular diameter of n‐butane, propane, and ethane permeating through ethylcellulose. This relationship suggests that the diffusion process depends upon the availability of sufficient cross‐sectional area for the penetrant to diffuse. An Arrhenius temperature dependence was observed for permeation coefficients and diffusion coefficients for n‐butane, propane, and ethane in ethylcellulose. The activation energy of diffusion at zero penetrant concentration is directly proportional to the square of the gas molecular diameter and the entropy of activation. This observation is consistent with the view that the activation energy of diffusion is associated with the energy required to produce a space of sufficient cross‐section for the diffusion molecule to pass.
Percolation transition and conductivity in macroscopically anisotropic two‐component polymer membranes
Authors: Narȩbska Anna , Wódzski Romuald , Bukowski Zbigniew
Published: April 2003

Percolation conductance has been studied for polypropylene/poly(acrylic acid) membranes (PP‐g‐PAA) prepared by volume grafting of an ionic component onto polypropylene foil. In these membranes the volume fraction of the conducting phase decreases from the surface to the center, brining some anisotropy into the composition. For this material, the “insulator‐ to‐conductor” transition proceeds at a critical volume fraction Vc equal to 0.395. It has been proved that this critical volume fraction and the critical exponent t, found to be below that predicted by theory, i.e., 1.2 ± 0.03 instead of 1.6 ± 0.2, result from the gradient in the distribution of the conducting component in the direction of the current flow. Computations of Vc and t for the same PP‐g‐PAA copolymer with a randomly distributed conducting component have led to Vc = 0.08 and t* = 1.53. A critical exponent t in that range is characteristic of three‐dimensional systems; however, Vc is rather low, suggesting a nonspherical shape for the conducting domains.
Cross‐linked polystyrene‐dithiocarbamate polymers: Use in heavy metal removal
Authors: Wagner Carol K. , Hall Gene , Riegel Bram , Virgilio John De , Kamath Vanita , Germann Geoffrey
Published: April 2003

Cross‐linked polystyrene polymers were converted to dithiocarbamate polymers. These polymers were used to remove heavy metal cations from water. Dithiocarbamate polymers can be understood to be inherently more stable toward hydrolysis than xanthate polymers.
Solution studies of metal sulfonate ionomers IV: Effects of cosolvents
Authors: Lundberg R. D.
Published: April 2003

Previous studies have shown that metal sulfonated ionomers display unusual solution behavior. Typically, inomers, such as metal sulfonated EPDM or sulfonated polystyrene, are readily dissolved in mixed solvents, such as hydrocarbons plus alcohols. Such mixed solvents can provide unusual viscosity‐temperature behavior due to the strong inter‐or intramolecular interactions of the ionic groups.

This paper is concerned with studies directed at a variety of polar cosolvents, including amines, alcohols, acids, amides, and esters, in interactions with zinc sulfonated ethylene propylene diene monomer (sulfo‐EPDM). Within various classes of compounds the structural effects of such cosolvents on the solution viscosities of sulfonate ionomers have been elucidated. Generally, amines and alcohols have been found to be the most effective cosolvents. Amines appear to form a specific complex with zinc and can virtually eliminate ion pair association at extremely low levels. Within a homologous series, those compounds of shortest hydrocarbon chain length provide the most effective solvation of the ionic groups of sulfonated EPDM. The effect of structure of the amines or alcohols on solution viscosity has shown the efficiency of cosolvent interaction proceeding as normal > iso > secondary > tertiary in the alcohol series. These results are interpreted as a consequence of the cosolvent solvating the ionic groups wherein the more bulky cosolvents are least effective in solvating the metal cations.
Influencing the crystallization behavior of PET‐based segmented copoly(ether ester)
Authors: Zeilstra J. J.
Published: April 2003

Segmented copoly(ether ester) based on poly(ethylene terephthalate) and poly(oxytetramethylene) suffers from having a rather low rate of crystallization. The crystallization behavior of this elastomer can be influenced by cocondensation of selected diols and addition of nucleating agents and plasticizers. Changes of the crystallinity and morphology are studied by differential scanning calorimetry and dynamic‐mechanical analysis, respectively. Mechanical properties in relation to the different crystallinites obtained are reported.
Grafting of 3‐chloro‐2‐hydroxypropyl acrylate onto chrome tanned collagen fibers
Authors: Klásek A. , Šimoníková J. , Kaszonyiová A. , Pavelka F. , Janda L.
Published: April 2003

Grafting of 3‐chloro‐2‐hydroxypropyl acrylate onto chrome tanned collagen fibers, initiated by the redox system bisulfite/persulfate, has been investigated. Using the method of statistical planning of experiments regression equations have been obtained, describing the effect of monomer concentration and of initiation system constituents concentrations on monomer conversion, degree of grafting of collagen, and on physical properties of resulting composites. The relationship between the content of poly(3‐chloro‐2‐hydroxypropyl acrylate) in the composite and the swelling ability, water absorption, and tensile strength of the same is discussed. Moreover, results of morphology investigation of composites, prepared by grafting of various acrylic monomers onto collagen fibers, as obtained by electron microscopy, are presented and discussed.
Polymeric reaction of polymer‐monomer system irradiated by low energy electron beam. III. Adhesive property of pressure sensitive adhesive
Authors: Takiguchi Ryohei , Uryu Toshiyuki
Published: April 2003

Application of low‐energy electron beam to nonsolvent‐type pressure‐sensitive adhesive is investigated. Adhesive properties such as peel strength, dead load strength, and ball tack were closely related to the reaction behavior (gel fraction and graft efficiency) of the acrylate polymer‐monomer system. The reaction behavior is eluciadated by combining the measurements of gel fraction, infrared spectrum of gel, and molecular weight distribution detected by gel permeation chromatogrophy. It was found that the adhesive property of electro beamcured adhesives depends on the molecular weight of added polymer, monomer concentration, and irradiation dose. Graft polymerization and moderate crosslinking by electron beam irradiation especially contribute to superior high adhesive properties.
Aging of polypropylene using high oxygen pressure: Influence of sample thickness and stabilization
Authors: Faulkner Douglas L.
Published: April 2003

Thin films (0.05–0.08 mm thick) of stabilized and unstabilized polypropylene were aged under 4.24 MPa (614 psi) of oxygen at 90°C. The oxidation of these films was monitored using transmission infrared spectroscopy. Previously it was shown that embrittlement for the thin unstabilized polypropylene films occurred 3.6 times faster in 4.24 MPa of oxygen than in air at atmospheric pressure. For thick stabilized polypropylene (3.18 mm thick), the oxidative induction time at 120°C and 4.24 MPa of oxygen was drastically reduced compared with conventional air aging at this temperature. Specifically, sample embrittlement occured in 1 week during the high oxygen pressure aging in stark contrast to 70 weeks for conventional air aging. Consequently, due to the shortening of time to age samples at high oxygen pressures, aging can be conducted at this lower temperature (nearer the service temperature) rather than at this commonly used aging temperature of 150°C.
Properties of syndiotactic‐rich poly(vinyl alcohol) thin film in water. III. Contraction and extension of drawn and annealed thin film in water
Authors: Yamaura Kazuo , Matsuzawa Shuji
Published: April 2003

Contraction and extension behaviors in water for drawn (four times original length) and annealed (at 60–215°C) thin films of poly(vinyl alcohol) (PVAVTFA) derived from vinyl trifluoroacetate have been examined. At a constant temperature of 25°C, drawn films annealed at 60–190°C contracted after a certain standing time. Length of films annealed at 200°C did not change after standing of 20 min and film annealed at 215°C extended very little. As the temperature was raised, the drawn films annealed at 60–190°C contracted further until a certain temperature and then extended. The drawn film annealed at 200°C first started contraction at 70°C. The drawn film annealed at 215°C extended further very little until 75°C and then contracted very little until 99°C (in boiling water). In standing at 99°C, it contracted very little with standing and resisted without breaking for 300 min.
A study on blends of different molecular weights of polypropylene
Authors: Deopura B. L. , Kadam S.
Published: April 2003

Blends of small percentage of plastic grade polypropylene with fiber grade polypropylene are studied in unoriented and oriented states. A 3% blend sample has a higher spherulitic growth rate, and improved mechanical behavior in drawn fiber state as compared to the parent sample. These changes are related to the presence of bimodal and trimodal crystal texture of polypropylene in the blend, respectively. At a higher blend percent, specifically at 10 and 15%, the mechanical properties of the drawn fiber are inferior and these are related to partial phase segregation of the components.
Preparation of block copolymers with polymeric azocarbamate as an initiator
Authors: Yürük H. , Özdemir A. B. , Baysal B. M.
Published: April 2003

Block copolymers containing polystyrene and poly(ethylene oxide) or poly(propylene oxide) segments were prepared via chemical reactions. A stepwise procedure was first employed to prepare macroazocarbamates by capping poly(ethylene oxide) glycols or poly(propylene oxide) glycols and an aliphatic diisocyanate and subsequently by reacting this intermediate with an azobisalcohol. This macroazocarbamate was later used to initiate free radical polymerization at elevated temperatures. Styrene contents, molecular weights, and elastic modulus‐temperature relationships were determined.
Crystallinity and dicumyl peroxide diffusivity in low density polyethylene with different thermal histories
Authors: Gupta J. P. , Sefton Michael V.
Published: April 2003

The absorption diffusivity of dicumyl peroxide (DICUP) in low density polyethlene pellets that have been annealed and either cooled slowly or quenched has been measured and correlated with the corresponding changes in crystallinity as measured by DSC. Annealing at 125°C resulted in an increased crystallinity and decreased DICUP diffusivity (3.2 × 10−7 cm2/s for as supplied pellet to 5.2 × 10−8 cm2/s for annealed and slowly cooled pellets). Quenching the annealed pellet reduced the increase in crystallinity and corresponding decrease in diffusivity. The time course of annealing and secondary crystallization processes was defined through further DSC measurements. The relationship between crystallinity and pressure for both hot press films and 4 mm diameter extrudate was found to be identical, Indicating the importance of pressure on bulk crystallization phenomena regardless of the source of the pressure.
Formation of polyelectrolyte complexes between cellulose derivatives and their blood compatibility
Authors: Ito Hiraku , Shibata Toru , Miyamoto Takeaki , Noishiki Yasuharu , Inagaki Hiroshi
Published: April 2003

Formation of polyelectrolyte complexes (PECs) between cellulose derivatives in aqueous solution and their blood compatibility were examined. To this end, two types of quaternary ammonium cellulose derivatives, Q‐Cell and Q‐HEC, were prepared by treating cellulose and hydroxyethyl cellulose (HEC), respectively, with glycidyl trimethylammonium chloride. Anionic derivatives were carboxymethyl cellulose (CMC) with different degrees of substitution (DS) and cellulose sulfate (CS). In vivo blood tests were made by a method of peripheral vein indwelling suture. The results showed that the complex formation of Q‐Cell did not follow a stoichiometric reaction, but Q‐HEC reacted stoichiometrically with CMC and CS. It was also found that water‐insoluble cellulosic PECs are soluble in formic acid, showing that the cellulosic PEC films can be prepared from formic acid solutions. The blood tests revealed that by the criteria of the test method employed in this work, cellulosic PECs had a good blood compatibility.
Thermal analysis of the glass transition of plasticized poly(vinyl chloride)
Authors: Beirnes Kimberley J. , Burns Charles M.
Published: April 2003

Earlier studies by differential scanning calorimetry showed anomalous behavior of Tg with varying amounts of dioctyl phthalate, while by dynamic mechanical analysis 2 Tg's were found over a limited concentration range. In this study, two adjacent Tg's were found over the complete range of concentrations of dioctyl phthalate or dioctyl adipate, changing in relative contributions over the range. The results are shown to be consistent with the earlier work and to fit the Couchman model more closely than other models tested.
A study of polyion‐enzyme complexes: Quaternized poly(vinyl dimethylaminobenzal)‐glucose oxidase‐potassium poly(acrolein bissulfate) complex
Authors: Hua Jiadong , Liu Lu , Yin Rui , Fang Shibi , Jiang Yingyan
Published: April 2003

This report has mentioned a study that includes preparation of a polyion‐enzyme complex consisting of quaternized polyvinyl dimethylaminobenzal (QPVDAB), potassium polyacrolein bissulfate (KPABS), and glucose oxidase (COD), and evaluation of relationships between properties and structure of the complex are discussed.
Accelerated weathering of butadiene–styrene‐based rubber
Authors: Abu‐Zeid M. E.
Published: April 2003

Photoacoustic spectroscopy (PAS) was used for the study of accelerated weathering of some selective samples of butadiene–styrene rubber. It was found that, although their accelerated degradation is mainly due to the combined effects of UV and heat, the rate of their degradation solely depends on their compositions.
Prediction of stress–relaxation data of some nylons from stress–strain data
Authors: Bradley W. V. , Williams H. Leverne
Published: April 2003

Six commercially available nylons were tested for stress–strain and stress–relaxation properties. Use was made of a recently revealed approach to predicting viscoelastic properties beyond the linear region from an analysis of the stress–strain curve. The equations used were three‐dimensional employing the Halsey–Eyring viscoelastic model. The necessary constants were calculated and, when applied to the appropriate equations, reconstituted the stress–strain curve and predicted the stress–relaxation curves quite well.