Digital viscometer

Viscosity is a parameter, which is used to determine rheological properties of any preparation. Viscosity measurements were performed at 25 °C (ambient temperature) using Brookfield Digital Viscometer (Spindle: Low Viscosity-3, Stoughton, MA) at 10, 20, 30, 50, and 100 rpm. The experiment was carried out in triplicate.

The ultrasonic velocity of the NFs was evaluated at the temperature of 303 K using the MITTAL single-frequency ultrasonic interferometer (2 MHz, model F-81). The NFs’ viscosity at 303 K was determined using a digital viscometer (BROOKFIELD brand, Haverhill, MA, USA). The density of the NFs was calculated using a pyknometric approach. The mass of the liquid was determined using an electronic single-pan balance (made by K-ROY, Kolkatta, India) with an accuracy of 0.001 g. The refractive index was determined with an accuracy of 0.001 using Mittal Abbe refractometer (New Delhi, India). A thermostat with a temperature measuring accuracy of ±0.05 K was used to circulate water at 303 K during the measurement of the properties of NFs using viscometer, interferometer, and refractometer. The zeta potential values were measured using the Zetasizer (Litesizer 500, Malvern Pananalytical Ltd., Malvern, UK) instrument. The particle size, zeta potential, and molecular weight of the solution were determined by integrating dynamic light scattering, laser Doppler micro electrophoresis, and static light scattering.

The ASP system and PPG/ASP system were prepared using clean water, then diluted with produced water. The HAKKE MARS rheometer was used to determine the elastic modulus and viscous modulus of each system at a fixed stress and frequency under the temperature of 45 °C, and then the two systems were aged at 45 °C. The viscosity of the systems was measured at regular intervals using a BROOKFIELD digital viscometer to obtain the variation function of viscosity with time. During the aging process, the Texas-500C rotary drop interfacial tension meter was used to measure the interfacial tension between the system and crude oil under 45 °C and 4500 r/min.

Viscosity of the formulation was evaluated at 25°C using Brookfield digital viscometer. The dimensions were taken in the established speed settings. The settings range from 10 to 100 rotations per minute. A time interval of 30 seconds among 2
consecutive speeds in a declining manner is used.

A Brookfield digital viscometer was used to measure the viscosity of the TUL ointments, as presented in Table 1 (Brookfield Engineering Laboratories, Inc., Middleboro, MA, USA).