The Study Of Rheological Properties And Crystallization Of Biodiesels And Blends

This work studies the dilution of a biodiesel from Peanut oil, cotton seed oil, palm oil, and soya bean oil with diesel fuel of low pour point and cold filter plugging point to produce fuel blends with better cold characteristics.The low temperature fluidity and rheological property of the blends at different temperatures and different shear rates were measured on a rotatory rheometer. The crystal morphologies of the biodiesel blends at low temperatures were analyzed using a polarized light microscope. The results indicated that temperatures below PPs or CFPPs, the blends exhibited a non-Newtonian behavior as their dynamic viscosity increased remarkably with decreasing temperature, but decreased with increasing shear rate. However at temperatures higher than PPs or CFPPs, linear relationships between dynamic viscosity and shear rate of the biodiesel blends became Newtonians.At low temperatures, wax crystals of the biodiesel blends grew and agglomerated rapidly. The loss of fluidity of the biodiesel blends can therefore be attributed to the sharp increase of viscosity and, the rapid growth and agglomeration of wax crystals at cold temperatures. The findings of the cold flow properties of the75%(V) PEFAME-25%(V) PFAME suggests that nucleation plays a leading role in improving biodiesels cold flow properties. The resulting crystals have a more compact shape and will be less prone to agglomerate.