Sowmya, Bandi and Mohan, Anand
(2019)
Rheometric Characterization of Carbopol974p for application in controlled drug delivery.
Masters thesis, Indian institute of technology Hyderabad.
Abstract
Carbopol974p is a poly acrylic acid which contains carboxylic acid groups. Carbopol974p has major application in controlled drug delivery as a drug carrier for treating diseases related to human digestive tract. The rheological properties of Carbopol974p vary in the pHs (1.5 to 8.5) and temperatures (36.5°C to 39.5°C) of the human digestive tract, and have not been documented. Rheological measurements were carried out on Carbopol974p samples using shear rheometer
(Anton Paar Physica MCR301) with Cone and Plate geometry (Plate diameter was 75mm, and cone angle was 2°). Carbopol974p has pH 3.38 when made-up with distilled water at a concentration of 1.7% (w/v). Carbopol974p of pHs 4.5, 5.5, 6.5, 7.5 and 8.5 were prepared using buffer solutions of pH 4, pH 9.2, and pH 11. Steady state rheological measurements were conducted to characterize the Carbopol974p samples at different pHs and temperatures. Temperature ramp test was also conducted to record the effect of temperature on viscosity of Carbopol974p. Results of the flow test (viscosity versus shear rate data) showed that Carbopol974p exhibits non-Newtonian shear thinning behavior at all the temperatures and pHs tested. Constant shear test (viscosity versus time data) showed that Carbopol974p exhibits thixotropic behavior at a (constant) shear rate of 0.1s-1 and only shear thinning behavior at shear rate of 10s-1. Hysteresis test (viscosity during ramp up and ramp down of shear rate) showed that there was a non-zero area under the curve at low shear rates (quantitative values were different for various pHs and temperatures) whereas the area was zero at high shear rates. Results from temperature ramp test showed that the viscosity of Carbopol974p decreases as temperature rises, and the effect of temperature on Carbopol974p increases as pH increases. Results of all the rheological measurements showed that the viscosity of Carbopol974p increases as pH increases.
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