Two-point bending stiffness (ISO 5628):
|The force needed to bend the substrate without distorting its structure, i.e. without going beyond the elasticity modulus (E-modulus according to Young), expressed in mNm.
Stiffness has impact on the runnability (trouble-free feeding through a press or printer), but also on the look and feel of the substrate. For some applications (folding board) it is essential, e.g. boxes, wishing cards etc.
|In a stiffness meter a sample of defined dimensions is bent over an angle of 5° and a distance of 50 mm.
|Report the average force of 10 significant values in both MD and CD and the standard deviation.