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RESEARCH ON RHEOLOGY

R.Karthik

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Topics covered

SelectionofPectin as pharmaceuticalexcipient on the basis of

Rheological behavior

Determinationofoptimal combinationofsurfactants in

creams using rheology measurements

Rheological investigationofSelfEmulsificationprocess

Rheological analysis ofstabilityofpharmaceutical suspensions

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The aim ofthis study was to evaluate rheological properties of pectin solutions

to determine the influence of polymer concentration, pH, preservatives and

heating duration on viscosity, using Brookfield R/S Plus Rheometer. The

results shows that dilute pectin solutions are showing Newtonian, but at a

moderate concentration they exhibit the non-Newtonian behavior, and the

psudoplastic nature was found to increase with concentration. As the pH of

the polymer solution lowered there was increase in viscosity of the system

observed, this may be due do the carboxyl acid groups on the pectin chains

are neutralize i.e. reduction in ionization, and leads to reduction in hydration

of the carboxylic acid groups. As a result of reduced ionisation, thepolysaccharide molecules do not repel each other over their entire length. The

result shows that pectin solutions are stable at broad range of pH. It was

observed that as the temperature or pH of the system increases there was

decrease in viscosity.

SelectionofPectinaspharmaceuticalexcipient on

the basisofRheological behavior

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Purpose. Aimofthestudyistoexploretheviscoelastic propertiesofintermediate

liquidcrystalline (LC) phaseformedduring self-emulsification and toevaluate its

influenceon self-emulsification

performance.

Methods. Binarysystemoftween 80 (T80)andimwitor 742 (I742)was used and

different SES werepreparedwith I742 at 10, 30,50,70 and 90% w/w concentration

levels. Self-emulsificationwas monitored byvisualobservations anddroplet size

measurement. Mesophases obtained by50% v/v aqueous hydrationofSESwere

utilizedfor polarizing microscopy,differential scanning calorimetry and rheologicalstudies.

RheologicalinvestigationofSelfEmulsificationprocess

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Results

SES 30% presented good emulsifying properties and nano-size dropletswere observed after its emulsification as compared to micron sized droplets for

other SES. In polarizing microscopy, formation of intermediate LC phase was

observed in all SES. Lamellar phase was evident in 30% SES while other SES

exhibited micellar cubic phase. Presence ofhigh level ofstructurally bound water

in thermal analysis confirmed mesophase formation in all SES. Thus, rheological

studies concluded presence of weak and fragile mesophase structure in 30% SES

while LC phase structure with little structural build up was observed in other SES.

This weak mesophase structure in SES 30% presented no or very little resistance

against strain induced deformation. Therefore, during emulsification, weak

mesophase in SES 30% ruptured with ease and released jet of nano-size droplets

compared to coarse droplets for other SES.

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compliance= strain/stress

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Rheologicalanalysisofstabilityofpharmaceutical

suspensions

Viscometry: The samples were exposed to increasing stress (0.1-100 Pa) and relation

between shear stress and shear rate was studied.

Oscillation stress sweep: Linearviscoelastic region (LVR) was determined

in the stress range of0.1-100 Pa at aconstant frequency (1 Hz). The ability of

hydrated SES to resist the deformation with applied stress was recorded in terms of

trends of elastic modulus (G) and loss modulus (G).

Oscillation frequency sweep: The samples were exposed to increasing frequency (0.1-

10 Hz) at a constant stress in LVR. Effect of frequency on G, G, phase degree () and

loss tangent (tan ) were recorded.

Creep-recovery: SES samples were exposed to a constant stress in LVR for

100s. It was then instantly removed and the recovery was followed for 200s. The creep

compliance, J (defined as ratio between measured strain and applied stress) was

recorded against time.

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Shear stress

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References

Rheological EvaluationofSilicon/Carbopol Hydrophilic GelSystems as a Vehicle

for DeliveryofWater Insoluble Drugs Giulia Bonacucina,1 Marco Cespi,1 Monica Misici-Falzi,

and Giovanni F. Palmieri1,2

Rheological InvestigationofSelf-emulsification Process

Shailesh V. Biradar, Ravindra S. Dhumal, Anant Paradkar

Department ofPharmaceutics,Bharati Vidyapeeth University, Poona CollegeofPharmacy,

Erandwane, Pune 411 038, Maharashtra State, India

SELECTION OF PECTIN AS PHARMACEUTICAL EXCEPIENT ONTHE BASIS OF RHEOLOGICAL

BEHAVIOR RAJENDRA AWASTHI Laureate InstituteofPharmacy, Kathog 177101, (Teh. Dehra, Dist. Kangra,

HP), India

Rheological Analysis oftheStabilityofPharmaceuticalSuspensions

Eva-Maria Kutschmann, Gebrder Haake, Dieselstrasse4, D - 76227 Karlsruhe

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