تأثير الإجهادات ومعدلات سرعة القص العالية على سلوكية جريان مزيج من بولي حمض اللبن وبولي كربونات (50/50) في الحالة المنصهرة

Abstract

A blend of Poly(lactic acid) and polycarbonate PLA/PC in a ratio of (50/50) in the molten state was prepared under the influence of high temperatures and shear stresses using a capillary rheometer, The apparent shear stress transformations were plotted against apparent shear rate at various temperatures (170, 180, 190, 200)⁰C. The flow index (n) values for the studied blend were determined, revealing that the blend belongs to the pseudoplastic plastics family (n<1), pressure-volume curves were studied by examining the changes in pressure transformations (Pc) with respect to the ratio of length to radius L/R, and a value of (e = 14) was determined, Based on these data ,the true viscosity was determined ηc, showing that the true viscosity decreases with increasing shear stress and high shear rates.

To determine the flow activation energy, viscosity transformations were studied with the inverse of temperature at constant shear stress and constant shear rate, It was found that the flow activation energy at constant shear stress is greater than that at constant shear rate, attributed to the lesser impact of viscosity changes in this case.

The elasticity of the studied blend was examined using the (Barus) technique, revealing that the swelling rate (B) increases with higher shear stress and decreases with an increase in the ratio L/R.