2.1.2. Archimedes' Principle Method

In addition to the density calculated by geometric method, a density evaluation was also carried out using Archimedes' principle (buoyancy). In the Archimedes' test, fiber samples were weighed in air and then subjected to an immersion liquid with a density lower than that of the sample, according to ASTM D3800 [31]. Gasoline was used as the immersion liquid. Density was calculated using the formula indicated in the Equation (4):

$$\rho = \frac{(M\_3 - M\_1)}{((M\_3 - M\_1) - (M\_4 - M\_2))} \rho\_I \tag{4}$$

where *ρ<sup>l</sup>* is the density of liquid, as well as *M*<sup>1</sup> being the weight of the suspension wires in air, *M*<sup>2</sup> is the weight of the suspension wire in liquid, *M*<sup>3</sup> is the weight of the suspension wire with fiber in air and *M*<sup>4</sup> is the weight of the suspension wire with fiber in liquid.
