Some phenomenological relations for strain-induced birefringence of amorphous polymers (abstract)

Some phenomenological relations for straininduced birefringence of amorphouspolymers (abstract)Kunihiro Osaki and Tadashi Inoue

Citation: Journal of Rheology (1978-present) 36, 984 (1992); doi: 10.1122/1.550337 View online: http://dx.doi.org/10.1122/1.550337 View Table of Contents: http://scitation.aip.org/content/sor/journal/jor2/36/5?ver=pdfcov Published by the The Society of Rheology Articles you may be interested in StrainInduced Modified Form Birefringence In A OneDimensional Photonic Crystal: An Exact CoupledModeApproach AIP Conf. Proc. 1176, 102 (2009); 10.1063/1.3253874 Atomistic simulation of strain-induced amorphization Appl. Phys. Lett. 82, 2017 (2003); 10.1063/1.1563831 Straininduced chemical reactions AIP Conf. Proc. 309, 1349 (1994); 10.1063/1.46461 Birefringence of amorphous polymers III. On the modified stressoptical rule (abstract) J. Rheol. 36, 971 (1992); 10.1122/1.550371 Strain Birefringence of Polymer Chains J. Chem. Phys. 48, 3822 (1968); 10.1063/1.1669690

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Abstracts of manuscripts appearing inNihon Rheoroji Gakkaishi

(Journal of the Society of Rheology, Japan)Volume 19, 1991


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972 JAPANESE ABSTRACTS

Birefringence of amorphous polymers III.On the modified stress-optical rule

Hirotaka Okamoto, Hiroshi Hayashihara, Tadashi Inoue, andKunihiro Osaki

Institute for Chemical Research, Kyoto University, Uji,Kyoto 611, Japan

Synopsis

The stress-optical rule (SOR) does not hold valid in the glassy and the glassto-rubber transition zones of amorphous polymers. The birefringence and stresscan be related through a modified SOR: The stress is composed of two components each of which contributes to the birefringence with different degree ofeffectiveness. Studies of Read [Polym. Eng. Sci. 23, 835 (1983)] and of thepresent authors [Macromolecules, 24, 5670 (1991)] are based on different methods of assignment of the stress-optical coefficientsfor the two components. Weshow that the two component viscoelastic functions derived from the lattermethod are thermorheologically simple but those from the former are not.


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JAPANESE ABSTRACTS

Structural recovery of ferrite suspensions

Hiroyuki Kanai and Takeshi Amari

Graduate School of Science and Technology, ChibaUniversity, 1-33 Yayoi-cho, Chiba 260, Japan

Synopsis

973

In order to investigate the structural recovery of suspension of acicular y-ferritepowder in mineral oil, viscoelastic properties were measured intermittently withsmall amplitude oscillatory shearing (strain at 0.3%, rate at 10 rad/s). ACouette test fixture was used for the measurements. Storage and loss moduli ofthe suspension immediately after cessation of large amplitude oscillatory preshearing (strain at 50%-500%, rate at 50 rad/s, for 20 min) increased withincreasing strain amplitude of preshearing. The moduli of the suspension at theearly stage of recovery were found to follow the scaling equation:

G' (or G") - (1, where t is the resting time after cessation of preshearing. Themoduli decayed after reaching the maximum, when larger amplitude preshearing had been applied. The phenomenon is interpreted from the view point ofpercolation using a two-level (intra- and interfloc level) network model offlocculated suspensions.


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Mechanical properties of fatty acid monolayerson the water surface based on surface

pressure relaxation and area creepmeasurements

Tatsuya Tanizaki, Atsushi Takahara, and Tisato Kajiyama

Department of Chemical Science and Technology, Faculty ofEngineering, Kyushu University, Hakozaki, Higashi-ku,

Fukuoka 812, Japan

Synopsis

The surface pressure relaxation and area creep experiments were carried out forthe myristic acid (C I4 ) , stearic acid (C I8 ) , and behenic acid (C22 ) monolayerson the water surface at 293 K. The myristic acid monolayer is in an amorphousstate on the water surface at 293 K. In the case of 1T(t=0) = 17 mN m-I for themyristic acid monolayer, little change of 1T was observed in the experimentalrange of 1000s. The large relaxation was observed both above and below 17 mNm- I. On the other hand, the stearic and behenic acid monolayers are in crystalline states on the water surface at 293 K. In the case of 1T(t=O) =26mN m-I for the crystalline stearic acid monolayer, large relaxation of thesurface pressure was not observed up to 100 s. Also, in the case of 1T(t=O) =25mN m- I for the crystalline behenic acid monolayer, the surface pressure didnot change within 1000 s. The transmission electron microscopic (TEM) observation revealed that this stability of monolayer might be related to homogeneity of monolayer. Electron diffraction (ED) measurement also revealed thatthe origin of relaxation for crystalline monolayer at high surface pressure can beattributed to the collapse of monolayer and the sintering among crystallinedomains of monolayer. On the other hand, the area creep measurement revealedthat the magnitudes of constant pressure 1To which showed the smallest decreaseof area were 17, 23, and 25 mN m- I for the myristic, stearic, and behenic acidmonolayers, respectively. These surface pressure (1To) values are almost equal tothe surface pressure 1T(t=O) at which the monolayer showed fairly small surface pressure relaxation.


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JAPANESE ABSTRACTS 975

Capillary flow properties of chemically crosslinked low-density polyethylene and

isotactic polypropylene

Mitsuyoshi Fujiyama

Polymer Research Laboratory, Tokuyama Soda Co., Ltd; 1-1,Harumi-cho, Tokuyama-shi, Yamaguchi-ken 745, Japan

Synopsis

A low-density polyethylene (LDPE) sample and an isotactic polypropylene(PP) sample were chemically cross linked in molten state with dicumyl peroxide using liquid 1,2-polybutadiene (L-PB) as an auxiliary for PP. The effects ofthe degree of cross linking on their capillary flow properties have been studied.The apparent viscosity 'T/a of LDPE system at a constant shear rate rapidlyincreases until a gel content of 1.1 wt. %, which is due to the increase inmolecular weight, and after that log TJa linearly increases with the gel fraction,which is due to an action of gel particles as filler. The dependence of TJa on thegel fraction is more notable at lower shear rate. The value of "7a at a constantshear rate ofPP system with an L-PB content of 5 phr drops until a gel contentof about 15 wt. %, and after that shows a maximum at a gel fraction of about25 wt. %, and gradually decreases with the gel content. For the system of anL-PB content of 20 phr, 'T/a gradually increases with the gel fraction. The endcorrection coefficient v shows a maximum in a range of gel fractions from 15 to40 wt. %. The flow activation energy at a constant shear rate, !:J.Hy, of LDPEsystem decreases with the gel fraction and the flow activation energy at a constant shear stress, !:J.HT' shows a maximum at a gel fraction of about 70 wt. %.


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An empirical equation on a shift factor forsynthesizing master curves from nonlinear

viscoelasticity functions based on free volume

Takuji Yamaguchi, Susumu Saeki, and Junpei Yamanaka

Department of Materials Science and Engineering,Fukui University, Fukui 910, Japan

Synopsis

Ferry and Stratton proposed a relation between a shift factor and a strain. Theyassumed compressibility of free volume on the basis of a sample volume. On theother hand, we defined the compressibility on the basis of the free volume, andderived a new relation between the shift factor and the strain (or stress). Theequation we obtained was different in the formula from the Ferry-Strattonequation, but the properties of the equations were quite similar. Our equationcould satisfactorily approximate a relation between the shift factor and thestrain for relaxation curves of a polyethylene film, and also the relation betweenthe shift factor and the stress for creep curves of monofilaments of nylon andpoly (ethyleneterephthalate). Fractions of free-volume were estimated fromthese equations.


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JAPANESE ABSTRACTS

Diffusion and viscoelasticity of polystyrenedibutyl phthalate solutions

977

Norio Nemoto, Tadashi Inoue, and Kunihiro Osaki

Institute for Chemical Research, Kyoto University, Uji, Kyoto611, Japan

Masahiro Kishine

Mitsui Petroleum Chemical Co., Waki, Kuka, Yamaguchi740, Japan

Takaharu Kojima

Sekisui Chemical Co., Mishima, Osaka 618, Japan

Michio Kurata

Mitsubishi Gas Chemical Co., Katsushika, Tokyo 125, Japan

Synopsis

This paper summarizes recent works in which the entanglement effect on diffusion and viscoelasticity was mainly studied on solutions of narrowdistribution polystyrene (PS) in dibutylphthalate (DBP) over a wide range oftemperature T, concentration C, and molecular weight M. The temperaturedependence of the self-diffusion coefficient D, and the tracer diffusion coefficientDtr was described by the WLF equation with values of the WLF coefficients thesame as found for the solution viscosity 1/. The effects of entanglements on theself-diffusion behavior and the viscoelastic behavior were examined from dataanalysis in terms of the two parameters. the effective friction coefficient of asegment; and the molecular weight between entanglements Me. The productDs1/IC was close to the theoretical prediction based on the free Rouse chain upto M1Me- I and, for MI Me> 10, showed universal behavior characterized bythe linear proportionality to M 1Me- The ratio of the two characteristic times forviscoelasticity and diffusion took approximately a constant value ofO.15±O.05over the whole range of M 1Me studied. Reduction of diffusiondata on the basisof the two-parameter scheme was so successful that one master curve wasobtained for each set of D, and Dt~ data. Both the master curves were proportional to (MIMe ) - 2.5 in the highly entangled region, being not in harmonywith either the prediction of the reptation theory or the observation for PSmelts. The tracer diffusion behavior in the unentangled concentrated solutionwas described by the partial-draining model.


13:42:49


Rheological study on solid structure in colloidalsystems

Takayoshi Matsumoto

Department ofPolymer Chemistry, Kyoto University,Kyoto 606, Japan

Synopsis

Solid structure in colloidal systems can be roughly classified into two groups.One is the structure which is attributed to a random aggregation of the disperseparticles, the other is the ordered structure due to a regular arrangement of theparticles. For these types of structure, flow and large deformation are due to aslip in some plain at a constant stress which corresponds to the yield stress Uy

or the absolute value of the complex stress Iu*[. The value of uy is nearly equalto Io" Iat long time scale region. That is, the Cox-Merz empirical rule (u= IG*Iat t=w) cannot be applied for the deformation of the structure.


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JAPANESE ABSTRACTS

Studies on elongational viscosity of polymermelts

Kiyohito Koyama

979

Faculty of Engineering, Yamagata University, Yonezawa992, Japan

Synopsis

This paper summarizes an experimental study on an elongational rheometer andelongational viscosity measurements of polymer melt developed by the presentauthor and his coworkers. The elongational viscosity increases with time by twosteps: One is a gradual viscosity increase at small strain and the other is a rapidviscosity increase at large strain. The rapid viscosity increase behavior does notdepend on strain rate, temperature, and average molecular weight, but doesdepend on molecular weight distribution and chain branching. These experimental results were explained by introduction of small amounts of extremelylong relaxation time mode into the normal relaxation spectrum which is estimated from linear viscoelastic data. The elongational rheometer can quicklydetect the extremely long relaxation time mode.


13:42:49


Effect of molecular association on rheologicalproperties ofchitosanlacetic acid aqueous

solutions

Takayoshi Matsumoto

Department of Polymer Chemistry, Kyoto University,Kyoto 606, Japan

Masahiro Kawai and Toshiro Masuda

Research Center for Biomedical Engineering, KyotoUniversity, Kyoto 606, Japan

Synopsis

Light scattering and rheological properties of chitosan solutions in 2% aceticacid aqueous solution were measured by means of a low angle laser light scattering photometer (Chrornatix, KMX6) and a cone-plate Weissenberg Rheogoniometer (Sangamo Controls, R 18). Chitosan samples of CS62 and CS19,which have degrees of deacetylation of 0.62 and 0.79, respectively, associateeven in very low concentrations such as 10- 5 g/rnl and a degree of associationis 2-3. On the other hand, the molecular association does not occur in a chitosanCS96, which has a relatively high degree of deacetylation of 0.96. Rheologicalproperties show that the solutions of CS62 and CS96 are homogeneous and thesolutions of CS79 are heterogeneous, with a certain relaxation mechanism having relatively long relaxation times. The effect of the molecular association andthe heterogeneous structure on stress overshoot is also discussed.


13:42:49


Auto-controlled mechanism for rheologicalproperties of native ovalbumin aqueous colloid

Takayoshi Matsumoto and Jiro Chiba

Department ofPolymer Chemistry, Kyoto University, Kyoto606, Japan

Synopsis

Native ovalbumin (OA) molecules in aqueous colloids are more stable in anordered arrangement state than in a random dispersion state. Rate of the stabilization from the random dispersion state to the ordered arrangement state isextremely accelerated by shear flow. Isotropic colloids of native OA moleculesin buffer solutions show a remarkable yield stress a y and a rigidity G even invery dilute systems such as 0.027 wt. %. The values of a y and G remain almostconstant over a wide concentration range from 0.1% to 17%. This suggests thatthe systems are spontaneously controlled (auto-controlled) in order to suppressthe increase in o-y and G with increasing concentration of OA. This autocontrolled mechanism disappears completely with gelation by heat denaturation.


13:42:49


Self diffusion and viscoelasticity of aqueousdetergent solutions II. Effect of salt concentration

Takeshi Yamamura and Norio Nemoto


Toshiyuki Shikata

Faculty of Science, Osaka University, Toyonaka, Osaka 560,Japan

Kunihiro Osaki


Synopsis

Diffusion of rod-like micelles of cetyltrimethylammonium bromide (CTAB) inaqueous sodium salicylate (NaSal) solutions were studied by varying CTABconcentration CD and NaSal concentration Cs. For solutions with CD=O.OIand 0.1 M, a ratio CSICD ranged from 1.0 to 41 and from 0.70 to 6.0, respectively. For measurement of the diffusion coefficient D, the forced Rayleighscattering technique was employed at 25 "C. Plots of D against CSICD gave verycomplicated behavior such that D took a maximum and afterward took a minimum with increasing CSICD. CslCDvalues of the maximum and minimum forsolutions with CD=O.OI M was very different from that for CD=O.l M. But themagnitude of D was of the same order of 10-9 cm2 s-I for both solutions.Diffusion data could be reduced to one master curve by plotting D against theconcentration CJ of free salicylate ion Sal- in the low CJ region. The CJdependence of D at low CJ was found to roughly correspond to that of therelaxation time 1" obtained in earlier investigations from a fit of the complexshear modulus data of the same solutions to a Maxwell model with one relaxation time. At high ~, however, D appeared to increase more rapidly forsolutions with CD=O.Ol M than those with CD=O.l M. The diffusion mechanism of rod-like micelles was interpreted in terms of a theory of Brownianmotion of a rod in the semidilute region at low CJ and the breaking andreforming process of network strands at high ~.


13:42:49


Properties of IPNs of epoxy resin/bismaleimideallylester copolymer

Katsuyoshi Iisaka

Materials and Electronic Devices Laboratory, MitsubishiElectric Corporation, 1-1, Tsukaguchi-Honmachi 8

chome, Amagasaki, Hyogo 661, Japan

Synopsis

Interpenetrating polymer networks (IPNs) were prepared from anhydridecured epoxy resin and bismaleimide (BMI) coreacted with triallyltrimellitate(TAT), triallylisocyanurate (TAlC), and diallylisophthalate (DAP), underthe same gelling conditions for both the epoxide resin and BMI-allylestercomonomer. Dynamic mechanical properties of the IPNs were measured overthe temperature range from room temperature to 4OO"C. In addition, tensileand thermal degradation properties were measured for these IPNs. The rubberymodulus and primary dispersion temperature (Ta) due to the cured epoxy resinconsiderably increased with loading of BMI-allylester component. The value ofTa exhibited an asymptotic behavior at high loading, the value increasing in theorder ofBMI-TAT, -TAlC, and -DAP. The modulus behavior in the rubberstate followed approximately the Budiansky's equation and suggested the formation of IPN. The difference among the asymptotic values of Ta for eachseries can be explained in terms of polar-nonpolar solubilities of the components. The most efficientand major increase in Ta which occurred at about 50wt. % of BMI-allylester component, is based upon an enhanced miscibilitybetween both components as a result of interpenetration. The effects of interpenetration brought about maxima in tensile strength significantly higher thanthe tensile strength of the component networks and some improvement in thermal resistance at about 50 wt. % of BMI-allylester component.


13:42:49


Some phenomenological relations for straininduced birefringence of amorphous polymers

Kunihiro Osaki and Tadashi Inoue


Synopsis

The strain-induced birefringence of amorphous polymers can be described withthe stress-optical rule in the rubbery plateau and the terminal flow zones. Thisis not the case in the glassy and the glass-to-rubber transition zones. When thestress or the strain is sufficiently small, the birefringence may be described interms of the linear response theory similar to the linear viscoelasticity theory. Inthis paper, we present some new relations among the response functions such asthe time-dependent stress-optical coefficient and strain-optical coefficient. Thebirefringence in the following processes were considered: the stress relaxation atconstant strain, the creep, the oscillatory deformation, the strain of constantrate, and the subsequent elastic recoil.


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JAPANESE ABSTRACTS

Numerical calculation of the startup flow ofviscoelastic fluids in a circular pipe

under constant flow rates

Noriyasu Mori

985

Nara National College of Technology, Yamato-koriyama,Nara 639-11, Japan

Yoshiro Konishi, Takumi Kaige, and Kiyoji Nakamura

Department of Mechanical Engineering, Osaka University,Suita, Osaka 565, Japan

Synopsis

The transient flow after imposing a constant flow rate on viscoelastic fluidsinitially at rest in a tube has been numerically calculated by using a finitedifference method. The viscoelastic fluid model used is the Meister model witha memory function which depends on shear rate. The numerical calculation bythe Meister model has shown that the center line velocity exhibits an overshoot,an oscillation, and a slight undershoot before reaching a steady state and thatthe complicated behavior in the velocity change has no significant effect on apressure gradient change. Agreement between numerical calculations and experimental results is fairly good, though the overshoot in the calculation ofpressure gradient is weak compared with the experimental data.


13:42:49


Uniaxial elongational viscosity of high molecularweight high density polyethylene melts

Masayuki Shinohara

Polymer Research Laboratory, Idemitsu Petrochemical Co.,Ltd., Anesaki-Kaigan, Ichihara, Chiba 290-01, Japan

Synopsis

Extensional properties of high molecular weight high density polyethylene(HDPE) were studied. Uniaxial elongational viscosity was measured underconstant strain rate. The following conclusions were obtained. (I) Timetemperature superposition could be applied to the elongational viscosity at aconstant strain at different temperatures. (2) The samples which show a remarkable strain-hardening during deformation had a good processability, i.e.,narrow distribution of bottle thickness, for the blow molding. (3) Order of themagnitude of steady shear viscosity did not agree with that of maximum elongational viscosity at the same strain rate. (4) Shear relaxation modulus atnonlinear region could not be separated with the terms of strain and modulusduring long time period. Transient elongational viscositycalculated was good fitwith experimental viscosity behavior by introducing short time process.


13:42:49

JAPANESE ABSTRACTS

Elastic percolation in colloidal dispersionsflocculated by polymer bridging

Yasufumi Otsubo

987

Department of Image Science and Technology, Faculty ofEngineering, Chiba University, Yayoi-cho 1-33, Chiba-shi 260,

Japan

Synopsis

The dynamic viscoelasticity was measured for silica dispersions flocculated bypolymer bridging. When both the particle and polymer concentrations exceedsome critical values, the dispersions respond elastically at low frequencies because a network structure of unbounded floes is developed over the system. Thedispersed particle is compared to the site and the polymer bridge to the bond inthe percolation concept. Boundaries for elastic percolation were determined interms of the site-bond percolation. In bridging flocculation. many bridges areformed by one polymer chain and a series of bridges cannot be broken down tononinteracting bonds. Therefore, the critical probability for bond percolation,p~, varies with number of bridges formed by one polymer chain, N", whereas thecritical site probability, pf, is independent. As a result, scaling analysis is notapplicable to the bond process. Floes in which particles are connected by polymer chains were generated on the computer and p! was geometrically determined as a function of N b in a two-dimensional square lattice. For random-bondpercolation at Nb= I, the simulation gives the same value as the theoreticalprediction, but p~ decreases with increasing N b: The discrepancy between theexperimental results and simulation appears in the N b dependence of p~ whenN b is large. In strongly interacted systems, the formation of infinite floes in thegeometrical sense does not necessarily lead to the appearance of susceptibleelasticity. The fractal dimension of percolating floc decreases with increasingN b. The elastic properties above the percolation threshold may be closely relatedto the fractal structure of floes.


13:42:49


A general correlation between steady shear anddynamic properties of dilute polymer

solutions at zero shear and frequency conditions

K. C. Tam and C. Tiu

Department of Chemical Engineering, Monash University,Clayton, Victoria 3168, Australia

Synopsis

A simple relationship between the steady-shear polymer viscosity and the zerofrequency storage modulus for dilute polymer solutions is developed. It combines the Oldroyd-B model with the Zimm theory yielding a result that enablesthe prediction of elastic properties from a given Tip at zero deformation conditions. A correlation established from a large number of experimental data obtained for various solutions of polyacrylamide (Separan) and a polyisobutylene(PIB) agrees well with the theoretical expression. The relationship is also foundto be applicable to other polymeric systems such as dilute solutions of xanthangum and Pusher 700. Based on the simple fluid theory, the correlation may beused to predict the first normal stress coefficientat zero shear rate condition.


13:42:49

JAPANESE ABSTRACTS

An apparatus for dynamic birefringencemeasurements

Tadashi Inoue, Hirotaka Okamoto, Hiroshi Hayashihara,and Kunihiro Osaki


Synopsis

989

An apparatus was constructed for simultaneous measurements of the dynamicbirefringence and the complex Young's modulus. The frequency range was1-200 Hz. The instrument was calibrated with a polybutadiene film, for whichthe stress-optical law was expected to hold well. The stress-optical coefficientestimated by dynamic birefringence measurement was consistent with the resultof the static measurement. The stress-optical law did not hold valid for a polystyrene film containing 5 wt. % dibutyl phtalate in the glass-to-rubber transitionregion.


13:42:49


Changes of refractive index ellipsoid by biaxialdrawing of a PET film

Kunisuke Sakamoto

Research Center, Mitsubishi Kasei Corporation, 1000,Kamoshida-chou, Midori-hu, Yokohama 227, Japan

Synopsis

The change of optical property on transverse drawing of a uniaxially orientedPET film was investigated. The birefringence in the plane of film decreased inproportion to transverse draw ratio, and come to zero in the optically balancedcondition. The optical axis of a uniaxially oriented film separated into twooptical axes in the plane perpendicular to the transverse draw direction. At theoptically balanced condition, the two separated optical axes joined into oneoptical axis perpendicular to the plane of films. These observations could bedescribed well with a model based on the assumption that a refractive index ineach principal direction changes in proportion to draw ratio.


13:42:49

JAPANESE ABSTRACTS

The measurement of viscosity by tuning-forkvibration mechanism

Shosuke Ishiwata, Mitsuro Hayashi, Hideaki Ohshima,and Osamu Suzuki

991

Central Research Laboratory, Chichibu Cement Co., Ltd., 1-1,2-Chome, Tsukimicho, Kumagaya, Saitama 360, Japan

Synopsis

We developed an unique device for measuring the viscosity of the liquids, usingthe mechanism of the tuning-fork vibration. This device has a pair of platesprings with a circular plate mounted on the end. When a pair of circular platesis operated in a sample by a resonance vibration in a reverse phase at a constantfrequency, its amplitude is inversely proportional to the viscosity of the sample.So the viscosity can be obtained by measuring the amplitude. This device usesthe standard liquid for calibration, and stores the calibration curve of the relationship between the amplitude value and the viscosity of standard sample. Therheological complicated materials can also be characterized by using this device.


13:42:49


Viscoelastic properties of propylene-ethyleneblock copolymer melts

Mitsuyoshi Fujiyama and Tetsuo Wakino

Polymer Research Laboratory, Tokuyama Soda Co., Ltd.,1-1, Harumi-cho, Tokuyama, Yamaguchi 745, Japan

Yasuhiro Kagiyama

Specialty Product Department Tokuyama Soda Co., Ltd.,1-1, Mikage-cho, Tokuyama, Yamaguchi 745, Japan

Synopsis

Stress relaxation and creep behavior of 16 commercial propylene-ethylene blockcopolymers was measured in a molten state. The relaxation moduli of sampleswith monomodal molecular weight distribution show plateau or shoulder atlong times. The bimodality of molecular weight distribution in the latter samples is due to the ethylene-propylene copolymer component with high molecularweight. The plateau at long times is more noticeable as the bimodality is stronger. The height and width of the plateau is independent of the ethylene content.A PP-HDPE-EFR blend which was made as a model material of propyleneethylene block copolymer does not show the plateau. The relaxation modulus athigh temperature is always lower than that at low temperature, the timetemperature superposition can be performed well in all the measured range, andthe shift factor obeys the Arrhenius equation. It was assumed from the aboveexperimental results that appearance of the plateau at long times originatesmainly from the bimodality of molecular weight distribution, not from thedispersion state of the ethylene-propylene copolymer particles.


13:42:49


Analysis of fatigue behavior of high-densitypolyethylene based on dynamic viscoelastic

and small angle light scattering measurementsduring the fatigue process

Atsushi Takahara, Yoshio Nishi, Norihiro Kaiya,and Tisato Kajiyama

Department of Chemical Science & Technology,Faculty ofEngineering, Kyushu University,

Higashi-hu, Fukuoka 812, Japan

Synopsis

The high-density polyethylene (HOPE) films have been prepared eitherthrough melt quenching or isothermal crystallization. The fatigue behavior ofthose HOPE films under constant strain amplitude has been investigated basedon dynamic viscoelastic and small angle light scattering (SALS) measurementsduring the fatigue process. Nonlinear viscoelastic behavior under cyclic fatiguehas been observed for both melt-quenched and isothermally crystallizedHOPEs. Melt-quenched HOPE showed greater fatigue strength compared withisothermally crystallized HOPE. The SALS measurement under cyclic fatiguecan reveal the deformation process of spherulitic structure during the fatigueprocess. Melt-quenched HOPE showed elongation of spherulitic structure under cyclic fatigue. On the other hand, isothermally crystallized HDPE did notshow any elongation until the onset of fatigue fracture. The short fatigue lifetime and small deformation of spherulitic structure for isothermally crystallizedHOPE can be ascribed to the sharp boundary between spherulitis.


13:42:49


Capillary flow properties of PVC melts

Mitsuyoshi Fujiyama and Tetsuo Wakino

Polymer Research Laboratory, Tokuyama Soda Co., Ltd.,1-1, Harumi-cho, Tokuyama, Yamaguchi 745, Japan

Synopsis

The effects of degree of polymerization and temperature on flow properties ofPVC melts have been studied by using a Koka Flow Tester. Each flow curve isexpressed by two straight lines of different slopes which meet at a breakingpoint. The critical shear rate y;"c at the breaking point increases as the degree ofpolym~rization decreases or the temperature increases. The critical shear stressTc at r:VC increases as the degree of polymerization decreases, being almostindependent of the temperature. Th~ end correction coefficient v shows a minimum or begins to increase around r;"c' The coefficient v increases as the degreeof polymerization increases or the temperature decreases. The extrudate issmooth on the surface at low shear rates, shows a small wavy roughness. (sharkskin) at shear rates just below r;"c, becomes fairly smooth again beyond y:ve. andthen shows intensive irregular roughness (melt fracture) at higher shear rates.The die swell becomes notable as degree of polymerization decreases or thetemperature increases. The die swell takes a maximum at a shear rate just belowr;"", where a shark skin appears on the extrudate, Differing from usual thermoplastic resin melts, PVC melts show a negative correlation between the die swellratio and the end correction coefficient. This seems to be due to the followingreason: PVC melts have high viscosities and have long relaxation times forstrain recovery, and thus the extrudates solidify without being fully relaxed.This tendency of solidification without relaxation is more noticeable as thedegree of polymerization increases or the temperature decreases.


13:42:49


Reproduction of the stress-strain curve for glassypolymers by a mechanical model bearing the

concept of structural transition

Shin-ya Yoshioka, Shoji Sugimoto, Yukuo Nanzai,and Sachio Ueda

Faculty of Engineering, Osaka City University,Sumiyoshi-ku, Osaka 558, Japan

Synopsis

The rate analysis of steady plastic flow in glassy polymers has verified that thestructure of the polymers is changed into a liquid-like structure during the yieldprocess. This result motivated us to develop a mechanical model which predictsthe stress-strain curve for glassy polymers. The model is composed of a dashpotand two elastic springs, where the viscosity of dashpot is a single parameterquantifying the structural transition and is approximated by a simple mathematical equation decreasing with increasing strain. Using this model, stressstrain relations were simulated for poly (methyl methacrylate) and poly (vinylchloride) under uniaxial constant-rate tension and compression. The modelreproduced successfully the experimental stress-strain curves over a wide rangeof temperature and strain rate for each case. This led to a conclusion that at auniaxial constant deformation rate the structural change in the glasses is mainlygoverned by strain. Moreover, the optimum equation for the internal viscositydetermined by the simulation indicated that the degree of structural change isclosely related to both the yield strain and the strain range in the lower yieldstate,


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Self-diffusion of micelles and viscoelasticityof aqueous detergent solutions

Takeshi Yamamura, Toshitsugu Kusaka, Eiichi Takatori,Tadashi Inoue, Norio Nemoto, and Kunihiro Osaki


Toshiyuki Shikata and Tadao Kotaka

Faculty of Science, Osaka University, Toyonaka,Osaka 560, Japan

Synopsis

The viscoelasticity and self-diffusion were investigated for aqueous solutions ofcetyltrimethylammonium bromide (CTAB) containing sodium salicylate(NaSal). The concentration ofCTAB, CD> was equal to that of NaSal, Cs' Thissystem contains thread-like micelles and exhibits pronounced viscoelastic behavior. The storage modulus G' and loss modulus G n could be fitted with theMaxwell model of one relaxation time when CD< 0.5 M. The plateau modulusGN was proportional to CI, over a wide range of CD- This property is similar tothat of concentrated polymer solutions. The relaxation time 'T' was evaluatedfrom the frequency at which G " takes maximum, The self-diffusion coefficientD was measured by forced Rayleigh scattering measurement. The quantities Dand 'T'- 1 varied in a similar manner as a function of CJi, when CD<0.2 M, theyincreased with CDand when CD<0,2 M, they decreased with CD- This behavioris remarkably different from polymer solutions. The rate of diffusion may becontrolled by the rate of the process where thread-like micelles cut across eachother, a process proposed previously to describe the stress relaxation.


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JAPANESE ABSTRACTS

Viscoelastic properties of polymer solutionsat temperatures lower than e points

Yoshiaki Takahashi, Masayoshi Yamaguchi,Daisuke Sakakura, and Ichiro Noda

Department of Synthetic Chemistry, Nagoya University,Chikusa-ku, Nagoya 464-01, Japan

Synopsis

997

Zero-shear viscosity TfD and steady-state compliance J, of poly(amethylstyrenes) in benzyl n-butyl phthalate (8=4.6 'C) and polystyrene indioctyl phthalate (8=22 'C) were measured at temperatures lower than the 8points. Moreover, stress developments after onset of steady shear flow weremeasured and the strength of entanglement was estimated on the basis of network rupture model. The concentration and the molecular weight dependencesof TfD at temperatures lower than the 8 points are almost the same as those atthe 8 temperatures, but the magnitude of Tfo increases with decreasing temperature. This suggests that the strength of entanglement increases with decreasingsolvent power. On the other hand, Je values at the temperatures lower than the8 points are almost the same as those in good and 8 solvents. This resultindicates that the entangled structure of polymer solution effective to J, isalmost independent of solvent power. Therefore, it is concluded that the gel-likebehavior of polymer solution at temperatures lower than the 8 points is causedby the long relaxation times due to the high viscosity.


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Numerical simulation on the flow of aviscoelastic fluid through an axisymmetric

abrupt contraction-Effect of elongational flowcharacteristics on vortex and entrance

pressure drop

Toshihisa Kajiwara, Yoshifumi Kuwano,and Kazumori Funatsu

Department of Chemical Engineering, Kyushu University,6·10·1 Hakozaki, Higashi-ku, Fukuoka 812, Japan

Synopsis

The flow of a viscoelastic fluid through a 4:I axisymmetric abrupt contractionwas studied by means of the finite element method. The effects of elongationalviscosity on vortex and entrance pressure drop were investigated in detail usingthe viscoelastic models which have different values of elongational viscosity byvarying the model parameters. The Phan Thien-Tanner (PTT) type and theGiesekus type models with a single relaxation time were used as the constitutiveequations. It is found that the vortex grows with the recoverable strain and themodel with higher elongational viscosity predicts a larger and more intensivevortex. It seems that the vortex becomes more intensive as recoverable strainbecomes larger if elongational viscosity curves coincide. The model with higherelongational viscosity gives larger values for the entrance correction in the PTTtype model, while the Giesekus type model gives the opposite prediction. Itseems that the magnitude of entrance correction cannot be explained only fromthe elongational viscosity.


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Thermal conductivity and flocculated structureof suspension of carbon black

Xianfu Wei, Takeshi Amari, and Koichiro Watanabe

Department of Image Science and Technology,Faculty of Engineering, Chiba University,

1-33 Yayoi-cho, Chiba 260, Japan

Synopsis

A modified concentric cylinder viscometer was used for the simultaneous measurement of thermal conductivity and apparent viscosity. The thermal conductivity of disperse medium is 100 times higher than that of carbon black particles,suggesting the particles behave as obstacles to thermal conductance. In flowfield, heat transfer is mainly caused by forced convection and the effect ofparticle orientation on the thermal conductivity of the system becomes large.After cessation of shear flow, the thermal conductivity decreases drasticallydepending on the rate of shear before the cessation of flow, and recovers gradually with elapsed time. The process of thermal conductance at rest state is byradiation. The thermal conductivity of the disperse system where the particlesare dispersed uniformly agents. The thermal conductivity of the system containing a small amount of dispersing is comparatively low, but aggregation ofparticles results in an increase of conductance because of the path for thermalconductance. In the disperse system, aggregation of particles is depressed by theaddition of dispersing agents. The thermal conductivity of the system containinga small amount of dispersing agent does not change with time. With increasingconcentration of disperse particles, the thermal conductivity of the system isreduced. The concentration dependence of thermal conductivity can be expressed by Hamilton's theory, qualitatively. However, in the higher concentration region, the experimental values of thermal conductivity are larger than thetheoretical values, because highly developed flocculated structures are con

.structed.


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Injection molding of liquid-crystalline polymer

Masao Haria

Institute for Chemical Research, Kyoto University, Gokasho,Uji-City, Kyoto 611, Japan

Ei-ichi Kamei and Shigeru Yao

Hirakata Laboratory, Ube Industries, Ltd., Nakamiya Kitamachi, Hirakata 573, Japan

Synopsis

A liquid-crystalline copolyester consisting of 1,4-oxybenzoate and ethyleneterephthalate groups was subjected to the injection molding using a rectangularmold 120X70 X I mm with a slot gate of O.5-mm gap. The structures ofinjection-molded products were studied in detail by the x-ray diffraction methodand the techniques of polarizing microscope. The molecules in the outer layerscontiguous to both surfaces of injection-molded rectangular plate were highlyoriented in the direction of injection and strongly birefringent, whilst the interior layer remained principally unoriented. The generation of characteristicbinary structure with sharp boundaries was interpreted in terms of CAE dataand the rheological behavior of the melt of liquid-crystalline polymer. Theproducts of usual polymer made up of flexible molecules, on the contrary, gaveisotropic products. The measurements of relaxation time afforded a key to anunderstanding of the difference between the behavior of liquid-crystalline polymer and that of usual polymer. The structural anisotropy of the products ofliquid-crystalline polymer resulted in the anisotropy of mechanical properties.The structure produced by processing proved to be a determining factor for themechanical properties of products in preference to the material of which theproduct was composed.


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Rheological properties of a thermotropic liquidcrystalline copolyester

Ken-ichi Fujiwara

Performance Polymers Research Laboratory, IdemitsuPetrochemical Co., Ltd., 1660 Kamiizumi, Sodegaura-machi,

Kimitsu-gun, Chiba-ken 299-02, Japan

Toshiro Masuda

Research Center for Biomedical Engineering, KyotoUniversity, Kyoto 606, Japan

Masaoki Takahashi

Department of Polymer Chemistry, Kyoto University,Kyoto 606, Japan

Synopsis

Rheological properties of a thermotropic liquid-crystalline copolyester whichwas synthesized from poly(ethylene terephthalate) and 60 mol % phydroxybenzoic acid were investigated. The dynamic and steady flow propertiesabove the rheological transition temperature (~270 ·C) were studied in detail.It has been found that the steady flow properties are not affected by thermalhistory in the anisotropic state. The following relations hold between steadyflow and dynamic viscoelastic properties of the sample with a shearing history:171*(w)I=71(Y) at w=y, and lim",_o G'(w) = 1I5IimT_oNj(r). In theanisotropic state. the thermotropic liquid-crystalline copolyester shows a significant shear-thinning of viscosity even at very low shear rates and a first normalstress difference comparable with an isotropic copolyester melt which was synthesized from poly(ethylene terephthalate) and 28 mol % p-hydroxybenzoicacid. The steady compliance (Js) of the liquid-crystalline copolyester in theanisotropic state is about ten times as large as that of the isotropic copolyestermelt when compared at the same shear stress. It is shown that the storagecompliance of various liquid-crystalline polymers is about ten times as large asthat of liquid-crystalline polymers in the isotropic state and of the crystallinecopolyester in the molten state when compared at the same value of IG* I. theabsolute value of complex dynamic modulus.


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Documents

Some phenomenological relations for strain-induced birefringence of amorphous polymers (abstract)