摘要
An experimental study has been carried out to determine the flow behavoir (rheological characterization) of potential adhesive of starch derived from sweet potato (Ipoemoa batatas) and yam (Dioscorea rotundata) at varying temperatures ranging from 40°C to 85°C with borax blend of 0.83%. The results obtained showed decreasing viscosity with an increasing temperature;potatoes had higher viscosity and density (27 × 103 cP), (0.813 g/m3) than yam (23 × 103 cP), (0.415 g/m3). The rheological data were evaluated by the power law and Casson models to describe the rheological behavoir. The Casson model gave a relatively poor fit to the experimental data with R values ranging from 0.899 to 0.967 from yam while a better fit was obtained for potato with r values ranging from 0.957 to 0.976. The predicted k and n values fit into experimental data (K = 26.36 and 0.388) and (K = 34.75 and 0.649) for yam and potato respectively;n < 1 showing Non-Newtonian behavoir. The relation between the temperature and K was described by an Arrhenius equation. Activation energies of 2.69 KJ/mol and 5.87 KJ/mol for yam and potato blends were obtained, indicating more sensitivity of yam blend to temperature compared to potato blend. With the experimental values obtained, a mathematical expression to relate shear stress and shear rate were proposed as:τ=26.36γ0.388 and τ=34.75γ0.649, for both the yam and potato blends respectively.
An experimental study has been carried out to determine the flow behavoir (rheological characterization) of potential adhesive of starch derived from sweet potato (Ipoemoa batatas) and yam (Dioscorea rotundata) at varying temperatures ranging from 40°C to 85°C with borax blend of 0.83%. The results obtained showed decreasing viscosity with an increasing temperature;potatoes had higher viscosity and density (27 × 103 cP), (0.813 g/m3) than yam (23 × 103 cP), (0.415 g/m3). The rheological data were evaluated by the power law and Casson models to describe the rheological behavoir. The Casson model gave a relatively poor fit to the experimental data with R values ranging from 0.899 to 0.967 from yam while a better fit was obtained for potato with r values ranging from 0.957 to 0.976. The predicted k and n values fit into experimental data (K = 26.36 and 0.388) and (K = 34.75 and 0.649) for yam and potato respectively;n < 1 showing Non-Newtonian behavoir. The relation between the temperature and K was described by an Arrhenius equation. Activation energies of 2.69 KJ/mol and 5.87 KJ/mol for yam and potato blends were obtained, indicating more sensitivity of yam blend to temperature compared to potato blend. With the experimental values obtained, a mathematical expression to relate shear stress and shear rate were proposed as:τ=26.36γ0.388 and τ=34.75γ0.649, for both the yam and potato blends respectively.
