NIST researchers say that defects in Graphene may appear due to the movement of the carbon atoms at high temperatures when producing graphene by heating silicon carbide under ultrahigh vacuum. Graphene tend to rearrange from six-sided rings to five or seven atoms. Stringing five and seven member rings together in closed loops creates a new type of defect or grain boundary loop in the honeycomb lattice. These defects might allow it a little flexibility, making Graphene even more resilient to tearing or fracturing.
The researchers say that we should be able to either avoid defects entirely or produce them at will by variations in growth conditions.