PHYSICOCHEMICAL CHARACTERIZATION OF HYBRID BIOPOLYMER FILMS FROM PURPLE YAM AND SWEET POTATO PEEL STARCHES

Biopolymers such as starches enhance the viscosity of injected fluids, leading to a favorable mobility ratio during chemical enhanced oil recovery. This study focused on combining starches extracted from the peels of purple yam and sweet potato, evaluating the characteristics of this hybrid biopolymer and comparing it to partially hydrolyzed polyacrylamide (HPAM). The extraction process involved sun drying, grinding, soaking, and sieving the peels to recover starch through precipitation. These starches were then dispersed in brine at varying concentrations and their physicochemical properties were accessed. The pH, viscosity, and weight were measured at different temperatures to understand the thermal behavior of the hybrid biopolymer solutions. The findings showed that the starches fully dissolved in brine across all tested concentrations and temperatures, confirming good compatibility. The hybrid biopolymer (starch blend) exhibited a highly unusual and favorable pH response: an upward shift in pH (13.9 @ 90°C) from acidity to alkalinity at 0.15% concentration. Viscosity of the starch blend (hybrid polymer) showed a moderate reduction from 6.50cp @ 30C to 4.50cp @ 90°C displaying good thermal stability. The solution exhibited a non-Newtonian behavior. Fourier Transform Infrared (FTIR) spectroscopy was performed to analyze the hybrid starch solution, with results compared against HPAM. Both materials exhibited similar absorption peaks corresponding to key functional groups. For the hybrid biopolymer, peaks at 1636 and 3336 cm⁻¹ were linked to C=C, N-H, and -OH vibrations, while HPAM showed peaks at 1647 and 3230 cm⁻¹, indicating the presence of C-O and N-H bonds within acrylamide compounds. The results suggest that the hybrid biopolymer lack toxic acrylamide, and offers a more environmentally friendly alternative while maintaining functional groups essential for mobility control and IFT reduction during EOR applications.