As shown in Fig. 1d, a sharp brittle-ductile transition occurs at about 35wt% of NR, showing an Izod impact strength of 58.3 kJ/m2, being approximately 21 times that of the neat PLA (2.75 kJ/m2).
It should be pointed out that all the samples of D65/35 were not fractured completely under the impact conditions, which is shown by the digital picture of the inset in Fig. 1d. If the un-fractured part is not considered for impact energy absorption, the samples would exhibit higher impact strength.
It is worth mentioning that in D65/35 the remarkable enhancement in impact strength is accompanied by high ductility with strain at break of ~200% (Fig. 1e).