Rheological properties of syndiotacticity‐rich ultrahigh molecular weight poly(vinyl alcohol) dilute solution

Choi, Jin Hyun; Lyoo, Won Seok; Ko, Sohk Won

doi:10.1002/app.1884

Cited by 6 publications

(4 citation statements)

References 44 publications

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“…According to Gilsenan and Ross-Murphy (2000), this behavior of G 00 , with a minimum in function of the frequency, could be considered as typical of gelatin based systems, and may be associated with relaxation processes that occur at large time scales. On another hand, in pure PVA solutions, a monotonic increase of G 00 in function of the frequency was observed (Choi et al, 2001).…”

Section: Frequency Sweep Testsmentioning

confidence: 95%

Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

Moraes

Carvalho

Bittante

et al. 2009

Journal of Food Engineering

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a b s t r a c tThe objective of this work was to study the rheological and thermal properties of film forming solutions (FFS) based on blends of gelatin and poly(vinyl alcohol) (PVA). The effect of the PVA concentration and plasticizer presence on the flow behavior, and viscoelastic and thermal properties of FFS was studied by steady-shear flow and oscillatory experiments, and also, by microcalorimetry. The FFS presented Newtonian behavior at 30°C, and the viscosity was not affected neither by the PVA concentration nor by the plasticizer. All FFS presented a phase transition during tests applying temperature scanning. It was verified that the PVA affected the viscoelastic properties of FFS by dilution of gelatin. This behavior was confirmed by microcalorimetric analysis. The behaviors of the storage (G 0 ) and loss (G 00 ) moduli as a function of frequency of FFS obtained at 5°C were typical of physical gels; with the G 0 higher than the G 00 . The strength of the gels was affected by the PVA concentration.

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Section: Frequency Sweep Testsmentioning

confidence: 95%

Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

Moraes

Carvalho

Bittante

et al. 2009

Journal of Food Engineering

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“…The mechanical viscoelastic behavior is one of the most important physical properties of polymers, and many studies have been conducted on the viscoelasticity of polymer solids17–19 and polymer solutions 20, 21. However, similar studies on PVAs with high r values have been limited.…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic behaviors and molecular motions of highly syndiotactic poly(vinyl alcohol) fibers

Gotoh

Nagara

Ohkoshi

et al. 2004

J Polym Sci B Polym Phys

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The viscoelastic behavior and molecular motion of highly syndiotactic poly-(vinyl alcohol) (S-PVA) fibers with a dyad syndiotacticity (r) of 69% were studied by dynamic mechanical thermal analysis and wide-angle X-ray diffraction and compared with those of atactic poly(vinyl alcohol) (A-PVA) fibers with r ϭ 54%. The ␤ c dispersion, based on the molecular motion of the chain molecules in the crystalline regions, was observed for A-PVA around 120 -140°C, and the only primary (␣ c ) dispersion was observed for S-PVA around 180°C. The thermal expansion coefficients for the a and c axes of the A-PVA crystal changed discontinuously around 120°C, which corresponded to the ␤ c dispersion. For S-PVA, the coefficient for the (002) plane changed discontinuously around 100°C, similarly to A-PVA, but that for the (100) plane remained unchanged between 20 and 220°C. These results showed that the intermolecular hydrogen bonding of S-PVA was stronger in the direction of the a axis than in the other directions, suppressing the ␤ c dispersion. The storage modulus and thermal expansion coefficient of the (020) plane (molecular axis) of S-PVA decreased markedly around 180°C, and this indicated that the ␣ c dispersion was due to the torsional motion of the molecular chains in the crystalline regions.

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“…Unlike the low molecular weight PVA solutions (Figure 5), the higher molecular weight PVA solutions exhibit slopes less than 2, as shown in Figure 6. It has been reported that heterogeneous polymer systems such as thermotropic liquidcrystalline polymers in their nematic phase show a decreased slope below 2 in the plot of storage modulus against loss modulus, and give rise to an inflection point in the curve [19][20] .…”

Section: Resultsmentioning

confidence: 99%

Flow Instability of Polyvinyl alcohol)/Dimethyl Sulfoxide Solution under Steady Shear

Yeol

Ryu

Lee

et al. 2011

Polymers and Polymer Composites

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The effects of solution temperature and molecular weight on the rheological responses of poly(vinyl alcohol) (PVA) semidilute solutions (13 g/dL- 19 g/dL) in dimethyl sulfoxide (DMSO) have been studied using PVA with two different number-average degrees of polymerization (Pn): 1700 and 4000. For the rheological experiments using dynamic shear, the PVA solution with a Pn of 1700 showed rather simple Newtonian fluid behaviour, whereas that with Pn of 4000 exhibited non-Newtonian shear thinning behaviour. Steady shear rheology experiments suggested that the lower Pn PVA solutions were Newtonian fluids, which is consistent with the dynamic shear rheology results. However, an abrupt decrease of shear viscosity at high shear rates was observed for the higher Pn PVA solutions at lower temperatures, such as 30 °C and 50 °C. At higher temperatures of 70 °C and 90 °C, the higher molecular weight PVA solutions exhibited simple shear thinning behaviour without any further complications of flow instability. The fact that temperature plays a critical role in controlling the observed flow instability of the PVA solutions in DMSO strongly suggests that there exist enhanced inter-chain interactions by hydrogen bonding of PVA chains beyond the chain entanglements, particularly for the higher Pn PVA semidilute solutions at low temperatures. Therefore, it is important to consider both chain entanglements and hydrogen bonding interactions in order to process PVA solutions without causing undesirable flow instability.

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Rheological properties of syndiotacticity‐rich ultrahigh molecular weight poly(vinyl alcohol) dilute solution

Cited by 6 publications

References 44 publications

Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

Viscoelastic behaviors and molecular motions of highly syndiotactic poly(vinyl alcohol) fibers

Flow Instability of Polyvinyl alcohol)/Dimethyl Sulfoxide Solution under Steady Shear

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