2.6.3. Strength Properties

Strength properties were determined according to ISO 12625-4 using the tensile index and calculated according to the following equation:

$$\text{Tensile Index (Nm/g)} = \frac{\frac{break}{W}}{G} \tag{2}$$

where *break* was the breaking force (N), *W* was the sample width (50 mm) and *G* was the sample grammage or basis weight (g/m<sup>2</sup> ).
