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Rushita Shah, Nabanita Saha, Takeshi Kitano, Petr Saha
Influence of strain on dynamic viscoelastic properties of swelled (H2O) and biomineralized (CaCO3) PVP-CMC hydrogels

Appl. Rheol. 25:3 (2015) 33979 (10 pages)

This paper reports the rheological behavior of swelled and mineralized hydrogel prepared using polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC) hydrogel as base polymer. Herein, the bio-mineral calcium carbonate (CaCO3) was incorporated into the hydrogel using simple liquid diffusion method. The morphology of the swelled and mineralized hydrogel was analyzed through scanning electron microscopy. Further, the normalized time of absorptivity was identified from the time dependent absorptivity behavior of calcite and water filled PVP-CMC hydrogel. The effect of the biomineral (CaCO3) and water on the dynamic viscoelastic properties, after penetrating inside the hydrogel matrix has been evaluated. The frequency sweep at 1 and 10 % strain and also strain sweep measurement were performed to determine the frequency and strain dependent viscoelastic moduli G' and G'' of both swelled and mineralized hydrogel. At higher strain the both moduli showed significant change over wide range of angular frequency region and the nature of mineralized polymer composites (MPC) turned from elastic to viscous. Based on the observed basic properties, MPC (calcite based polymer composites) can be recommended for the treatment of adyanamic bone disorder and water swelled hydrogel can be acclaimed as a scaffold for burned wound dressing.

Cite this publication as follows:
Shah R, Saha N, Kitano T, Saha P: Influence of strain on dynamic viscoelastic properties of swelled (H2O) and biomineralized (CaCO3) PVP-CMC hydrogels, Appl. Rheol. 25 (2015) 33979.

S.A.R. Hashmi, Takeshi Kitano
Effects of State Change of Liquid Crystalline Polymer on Dynamic Visco-elasticity of its Blends with Polyethylene-terephthalate

Appl. Rheol. 17:6 (2007) 64510 (7 pages)

The dynamic viscoelastic properties of liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) blends were studied at two different temperatures: 265 oC at which LCP was in solid state and 285 oC at which LCP was in molten state. The PET was in molten state at both the temperatures. The storage modulus, G', loss modulus, G'', dynamic viscosity, η', of blends with different compositions were evaluated and compared. The morphology of these samples was studied using scanning electron microscope, which exhibited composition dependency. A maxima was observed in the viscosity versus composition plot corresponding to 90/10 LCP/PET blend at 285oC. The G' versus G'' plots demonstrated the composition dependency of LCP/PET blends.

Cite this publication as follows:
Hashmi SAR, Kitano T: Effects of State Change of Liquid Crystalline Polymer on Dynamic Visco-elasticity of its Blends with Polyethylene-terephthalate, Appl. Rheol. 17 (2007) 64510.

S.A.R. Hashmi, T. Kitano
Rheology of LCP/PET Blends at Solid and Molten States of LCP

Appl. Rheol. 16:3 (2006) 152-160

Liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) were blended in an elastic melt extruder to make samples having different volume fractions of constituent polymers. Shear stress, shear viscosity, first normal stress difference at different shear rates under steady state conditions of these blends were evaluated at two different temperatures 265 and 285°C. The LCP was in solid state at 265° C and in melt state at 285°C and was dispersed in molten matrix of PET at both temperatures. Shear viscosity of blend increased with addition of LCP in PET matrix. A maxima was observed in viscosity versus composition plot. Blends containing more than 50 vol. % of LCP in the blend show higher viscosity as compared to the constituent polymers. First normal stress difference, N1, increased with LCP content in the blend at 285°C when ploted against shear stress whereas at 265°C this trend was opposite. The increased value of N1 with shear rate was explained assuming a tendency of asymmetric particles to rotate under velocity gradient of suspending medium. At 285°C N1 varied with shear stress in two stages. First stage was characterized with high sensitivity of N1 with shear stress, which reduced in second stage on plastic deformation of LCP droplets.

Cite this publication as follows:
Hashmi SAR, Kitano T: Rheology of LCP/PET Blends at Solid and Molten States of LCP, Appl. Rheol. 16 (2006) 152.

T. Kitano, S.A.R. Hashmi, N. Chand
Dynamic viscoelastic properties of organic/inorganic fibres reinforced LLDPE composites in molten state

Appl. Rheol. 11:5 (2001) 258-263

Dynamic rheological parameters such as storage modulus, G’, loss modulus, G’’, and dynamic viscosity, h’, at 200°C were studied for Kevlar fibres, glass fibres and their hybrids reinforced linear low density polyethylene (LLDPE). Parallel plate rheometer was employed for these tests. G’, G’’ and h’ increased with the increased reinforcement and angular frequency, w. Two sets of reinforcement, 10 and 20 vol.% of fibres are used in LLDPE. The composition of fibres in hybrid composites was varied. The replacement of glass fibres with Kevlar increases the values of G’, G’’ and h’. The values of these rheological parameters also increased with the thickness of the composite. This increase was associated with the decreased average orientation of fibres present in the composite. The effects of the change in strain amplitude on G’ and G’’ is also studied and reported here.

Cite this publication as follows:
Kitano T, Hashmi SAR, Chand N: Dynamic viscoelastic properties of organic/inorganic fibres reinforced LLDPE composites in molten state, Appl. Rheol. 11 (2001) 258.

K. Araki,T. Kitano, B. Hausnerova
Rheological Properties of Carbon Fiber and Carbon Black Filled Liquid Crystalline Polymer Melts

Appl. Rheol. 11:4 (2001) 188-196

The rheological properties of thermotropic liquid crystalline polymer (LCP) and its carbon fiber (CF) and carbon black (CB) filled composites in molten state were measured using a cone-plate rheometer. The measurements of the CF/LCP and CB/LCP melts were performed with carbon fiber contents of 5, 10 and 20 wt %, and carbon black contents of 1.5, 3, 5, 10 and 20 wt %. As expected, steady shear viscosity of the LCP, CF/LCP and CB/LCP melts in a low shear rate region (0.1 to 1 s-1) decreased with an increase of temperature and increased with rise of filler content. In shear rate region of 1 to 50 s-1, the LCP melt showed a unique viscosity behaviour with maximum and minimum values. The CF/LCP and CB/LCP melts showed disappearance of such a unique viscosity behaviour with an increase in the CF (CB) content and an increase of temperature. CB filler had a more pronounced effect on the disappearance of the unique viscosity behaviour in comparison with CF. Regarding apparent yield stress, the CF/LCP melts gave the same value as pure LCP, the CB/LCP melts showed an increase of yield with a rise of the filler content. In addition, the first normal stress difference of the LCP and CF/LCP melts are smaller than yield stress values, although the rate of increase with shear rate is higher in case of normal stress difference than in case of yield. The results of the dynamic shear oscillatory flow measurements of CF and CB based compounds at 300°C showed that both, the storage and loss moduli are more affected by carbon black filler. Complex viscosity values of the LCP and CF/LCP melts showed no such unique complex flow pattern as observed in the case of steady shear viscosity.

Cite this publication as follows:
Araki K, Kitano T, Hausnerova B: Rheological Properties of Carbon Fiber and Carbon Black Filled Liquid Crystalline Polymer Melts, Appl. Rheol. 11 (2001) 188.

V. Pavlinek, P. Saha, T. Kitano, T. Tanegashima
Influence of the Electric Field on the Electrorheological Behaviour of Cellulose Suspensions in Silicone Oils

Appl. Rheol. 9:2 (1999) 64-68

Cite this publication as follows:
Pavlinek V, Saha P, Kitano T, Tanegashima T: Influence of the Electric Field on the Electrorheological Behaviour of Cellulose Suspensions in Silicone Oils, Appl. Rheol. 9 (1999) 64.


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