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Volume 31 (2003)
- Issue 5 Pages 287-
- Issue 4 Pages 185-
- Issue 3 Pages 119-
- Issue 2 Pages 79-
- Issue 1 Pages 3-
Volume 31, Issue 4
Displaying 1-9 of 9 articles from this issue
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Takeharu Isaki, Masaoki Takahashi2003 Volume 31 Issue 4 Pages 185-194
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSPredictions on shear, planar, uniaxial and biaxial extensional flows are obtained from the BKZ type constitutive equations with the assumption of time-strain separability. Using a single relaxation mode, the effects of adjustable parameters on the stress growth coefficients are investigated in detail. A parameter describing the normal stress ratio governs the biaxial extensional flow behavior. It also controls the planar extensional flow behavior in the direction of constant width (perpendicular to the extension direction). Applicability of two representative models with this parameter is investigated for multiple relaxation times by comparing with a set of data for polyisobutylene (literature data) and polystyrene melts. We propose a method to obtain the model parameters from shear, uniaxial and biaxial damping functions. With the introduction of the parameter describing the normal stress ratio, both the PSMLT model (Papanastasiou-Screven-Macosko as modified by Luo-Tanner) and the WDFÖ model (Wagner-Demarmels as modified by Fegel-Öttinger) give good agreements with all the experimental data. It is suggested that the PSMLT model is preferable for engineering purposes, because the model gives non-divergent stresses in almost of all cases investigated.
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Takashi Kurose, Tatsuhiro Takahashi, Kiyohito Koyama2003 Volume 31 Issue 4 Pages 195-200
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSMelt rheology of blends consisting of tetrafluoroethylene/hexafluoropropylene (Teflon® FEP) copolymer and a small amount of polytetrafluoroethylene (Teflon® PTFE) has been studied under shear and uniaxial elongational deformations. The blends were prepared in a twin-screw kneader at 320°C. Compatibility of the components was investigated by DSC measurements, resulting in two separated peaks for the blends, which suggested FEP and PTFE were mixed in immiscible state. Structural observations were performed with optical microscope and SEM. It was clearly observed that PTFE uniaxialy elongated like fibril by kneading with FEP, and dispersed relatively uniformly in FEP. Storage modulus G' and complex viscosity η* toward lower frequency region became larger by increasing a loading of PTFE in dynamic shear measurements. The blends showed the strain-hardening property in uniaxial elongational measurements, whose tendency became stronger by increasing a loading of PTFE, though FEP hardly showed strain-hardening property. The results would be explained by the idea that dispersed PTFE fibril deformed during an elongational deformation and then generated a contractile stress, which would be resulted from that long length of dispersed PTFE and a strong adhesive interaction of interfaces between PTFE and FEP.
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Yoshinobu Isono, Seiichi Kawahara, Toshio Kase2003 Volume 31 Issue 4 Pages 201-206
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSSimultaneous measurements of stress relaxation and differential dynamic modulus were made at 268K for nearly monodisperse polybutadiene (Mw=2.2×105, 1,2-structure 70%, Me=3.6×103) and also one having coarse cross-linking (Mc=2.6×104) in double-step large shearing deformations with intermittently superposed small oscillations at a frequency of 0.1Hz, which falls in the middle of the rubbery plateau zone of the polymer. The first and the second strains, γ1 and γ2, were applied with a time interval t1. γ1 was constant 1.0. γ2 was varied from 1.0 to −2.0. t1 was 1000s being several times longer than τk, after which time-strain separability relationship holds in nonlinear relaxation modulus. Relaxation of stress after the second strain did not agree with BKZ prediction at −(3/2) γ1<γ2<0 for the uncross-linked sample, but it agreed at any γ2 for the corss-linked sample. At −(3/2) γ1<γ2<0, the uncross-linked sample showed irreversible change in the height of rubbery plateau, while the cross-linked sample showed reversible change. Such the differences between the two samples are discussed in terms of the two origins for nonlinear viscoelasticity of well entangled polymers, chain anisotropy and disentanglement.
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Tadashi Inoue, Kunihiro Osaki2003 Volume 31 Issue 4 Pages 207-212
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSLinear viscoelasticity behavior was described with sum of two terms for semi-dilute polystyrene solutions in tricresyl phosphate with molecular weights (M) close to 2Me, where Me is the entanglement molecular weight in the solution. One was a Rouse-Zimm (RZ) term represented by the Rouse-Zimm theory with arbitrarily chosen value of the longest relaxation time (τRZ). The other (L term) consisted of a relaxation mode with single relaxation time, τL (>τRZ), and high-frequency limiting modulus (GL) proportional to square of concentration, c. The shear stress, σ, and the first normal stress difference, N1, in steady shear were described with simple formulas proposed previously for more dilute solutions. The stress due to L term was assumed to be given by a K-BKZ equation with damping function h(γ)= (1+0.2γ2)−1/2, where γ is magnitude of shear. Contributions to σ and N1 from RZ term were derived from the Rouse-Zimm model theory, in which the relaxation time in steady flow decreased with rate of shear, γ, as τst=τRZ0+(τRZ−τRZ0)/(1+0.35τRZ γ). Here τRZ0 is the longest relaxation time of the polymer at the infinite dilution limit. The result together with previous result for more dilute solutions implies that η and Ψ1 for any non-entangled solutions are well described with use of parameters derived from dynamic viscoelasticity.
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Takanobu Kawamura, Kenji Urayama, Shinzo Kohjiya2003 Volume 31 Issue 4 Pages 213-217
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSWe strictly assess the validity of the familiar Mooney-Rivlin approach to the strain energy density function (W) on the basis of the quasi-equilibrium uniaxial and biaxial deformation data of end-linked poly(dimethylsiloxane) networks prepared from the solutions with various precursor concentrations. The constants C1 and C2 in the Mooney equation (W = C1 (I1 − 3) + C2 (I2 − 3)) are obtained from the intercept and slope of the linear correlation in the Mooney-Rivlin plots for the uniaxial data, respectively. The biaxial stress-strain relations estimated by the Mooney equation are far from the real behavior for all samples. It is clearly demonstrated that the Mooney-Rivlin approach, which has still been employed due to the simplicity in many studies, is unsuccessful to deduce the form of W.
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Syed Atiqur Rahman, Norio Nemoto2003 Volume 31 Issue 4 Pages 219-227
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSThe associative and mechanical properties of aluminium neutralized telechelic poly(ethylene butylene) ionomer, CTPEB-Al, in a nonpolar solvent of decalin were studied from very dilute solution up to the bulk with rheological methods and IR spectroscopy. Dilute solution viscometry revealed that CTPEB-Al molecules are associated in very dilute solution as their smallest associating structural unit made of three CTPEB chains and two aluminium tricarboxylate bonds [(COO−)3Al3+ : ATC bond]. These smallest associating units are further associated into larger aggregates with increasing polymer concentration C and form viscoelastic networks above C=7 wt%. The viscoelasticity and IR data reveal that in the low concentration range from 7 wt% to 12 wt%, CTPEB-Al chains are associated with each other in such a way that they form pretty long network strands with or without branches as dangling chains that act as elastically effective chains as a whole. In the networks with C ≥ 70 wt%, however, most of the ATC bonds and ion clusters act as effective crosslinking points so that almost 90% chains become elastically effective in the bulk state.
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Toshiyuki Shikata, Daisuke Ogata, Kenji Hanabusa2003 Volume 31 Issue 4 Pages 229-236
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSViscoelastic behavior of a supramolecular polymeric system, so-called an organogel, consisting of tri-3,7-dimethyloctyl cis-1,3,5-cyclohexanetricarboxamide (DO3CH) and n-decane (C10) was examined varying the concentration of DO3CH (c) and temperature ranged from 20 to 50°C. The obtained storage and loss moduli for the system were well described with the sum of two Maxwell models possessing two sets of a relaxation time and strength: τf and Gf, and τs (>τf) and Gs, whereas the viscoelastic behavior of organogels consisting of N, N', N"-tris(3,7-dimethyloctyl)benzene-1,3,5-tricarboxamide (DO3B) and n-alkanes is well described with only one Maxwell model. The value of Gf is proportional to c2 as observed in entangled flexible polymer systems and the organogels of DO3B. On the contrary, the value of Gs is approximately proportional to c1.3 similarly to the behavior predicted for rigid rodlike polymer solutions. The value of τf is essentially independent of c, while that of τs is kept at a constant and is followed by increasing above c = 10 gL−1. The activation energies of both the relaxation times are less than that for the viscosity of C10. Supramolecular polymeric structure bearing 2-type, rigid rodlike and flexible, portions are generated in the system due to intermolecular hydrogen bonding. The fast relaxation mode is attributed to the entanglement release between the flexible portions as observed in the organogels of DO3B, and the other is attributed to rotational relaxation of the rigid rodlike portion.
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Yukuo Nanzai2003 Volume 31 Issue 4 Pages 237-242
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSMolecular weight dependence of viscosity compensation effect for non-Newtonian flow in polymer glasses was studied using low and high molecular weight poly(methyl methacrylate)(PMMA) glass samples: the weight-averaged molecular weight MW was 82 × 103 for the former sample, whereas MW = 3380 × 103 for the latter. The compensation effect functions obtained from steady viscous flow in the samples were slightly different, yet the functions were almost the same straight line in a range of low activation energy values of molecular rearrangement. An experimental point obtained from a PMMA melt sample at temperatures much higher than the glass transition temperature was rightly on the straight line for the glasses. This implies that the structures of low and high molecular weight glass samples flowing at low temperatures far below the glass transition temperature and high strain rates are identical with the equilibrium structure of the melt at temperatures much higher than the glass transition temperature.
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Tomiichi Hasegawa, Hideo Asama, Takatsune Narumi2003 Volume 31 Issue 4 Pages 243-252
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSWe have developed a simple method of measuring the thrust of a jet by projecting it downwards into a liquid in a weighed vessel. The validity of this instrument has been confirmed using water. The thrusts for polymer solutions were measured to obtain the first normal stress differences, and it was concluded that the normal stress difference of dilute polymer solutions is correlated with the shear rate at low shear rates, but is a function of the mean velocity at high shear rates. Both the jet thrust and the friction factor of tube flow for very dilute polymer solutions were measured in laminar and turbulent flow regimes, and it was found that the estimated normal stress was rather small in comparison with the drag reduction effect. We discussed the correlation between the first normal stress difference and the velocity, assuming that a balance is attained among the elastic forces produced by each elastic stress at the entrance region, the fully developed flow region and the exit region of the tube flow, and obtained the result that the first normal stress difference is a function of velocity. This was confirmed with the experimental result of a surfactant solution.
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