Abstract
Polyamide 11 (PA11) is one of bioplastics (plant-derived plastics or recyclable-resource-based plastics). It is produced from renewable castor seeds. The castor seeds are inedible. This is important for food security issues and starvation issues because many bioplastics and biodegradable plastics are made from edible objects such as corn. In general, because yield condition of plastics depends on the hydrostatic pressure, the yield stress of compression is larger than that of tension. The yield stresses of PA 11 were measured at high and low strain rates by using a split Hopkinson pressure bar method and a universal testing machine. We determined constants of Druker-Prager yield criterion for PA11, and drew the yield curves in the plane of the equivalent stress and the hydrodynamic pressure and in the plane of principle stresses. The strain rate dependence of the yield condition of PA 11 was examined.
