PSI - Issue 64

Rosario Lombardi et al. / Procedia Structural Integrity 64 (2024) 1919–1926 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1921

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Two different fabrics configurations were also considered for the flax: 5.6 yarns/cm for jute textile (320 g/m 2 ), 6.2 yarns/cm (125 g/m 2 ) and 4.4 yarns/cm (265 g/m 2 ) for the 2 flax textiles, respectively (Pepe et al., 2023). 2.2. Fabric Impregnation The jute and flax textiles under consideration were impregnated with a biopolymer, PLA (Poly-Lactic Acid) NatureWork PLA 4060 , which comes in granules. This polymer was dissolved in acetone (2-propanone or dimethyl ketone) in three different concentrations with the aim to obtain a different viscosities and therefore a quantity of PLA deposited for each one. Specifically, the ratios used for the three acetone-PLA solutions have following composition: 85% acetone - 15% PLA; 90% acetone - 10% PLA; 95% acetone - 5% PLA. As the quantity of PLA used decreases, the viscosity of the solution decreases, and consequently the quantity of polymer deposited internally and on the surface of the fabric. As for acetone, the latter volatilizes and disperses into the environment. The procedure employed for the preparation of the analyzed tissue samples is therefore described here in the following: (i) PLA-acetone solution , weighing of the solvent (acetone) and the solute (PLA); mixing the two components and at the same time heat the solvent to a temperature that favors the dissolution of PLA (temperature set at 50°C and mixing speed between 350-500 RPM); (ii) Fabric yarns preparation , extracting 10 yarns (minimum length equal to 70 cm) from the natural textile mesh for each type of fabric; (iii) Yarn impregnation , pouring part of the solution into a beaker with a suitably wide base, and then proceeding with immersing the yarn inside it. The immersed yarn is immediately removed from the dissolved PLA and left to dry; (iv) drying of the impregnated fabric under a hood , the produced samples are then placed to dry inside a ventilated hood, at room temperature, for a minimum of 24 hours. In addition to the impregnation of the single yarns, considering that the final objective is to use the impregnated fabric mesh within a TRM system, the impregnation of the fabric as a whole entails was also investigated: for each acetone-PLA ratio, a 5x5 cm piece of each fabric was coated. 2.3.1. Density The method used for determining the density is similar to the one already described by the authors in a recent publication (Pepe et al., 2023) also in accordance with the ASTM D8171-18 standard (2020). Specifically, the steps performed to determine the density of the yarn impregnated with PLA are the following: (i) extraction of 4 cm long elements in order to warranty to insert the samples within the weighing device; (ii) saturating the samples with distilled water for 48 hours; (iii) swabbing the surface of the samples on filter paper, in order to obtain a sample in saturated surface dry (SSD) conditions; (iv) weighting the SSD samples either in air and immersed within the hydrostatic balance. 2.3.2. Linear density The linear density was measured, for both undried and dried samples, in accordance with the BS EN ISO 1889 (2009). In the first case (i.e., “undried samples”) , the procedure used consisted in the creation of elements of a fixed size, set equal to 10 cm, which were subsequently weighed individually and in groups of 7 (for a total length of 70 cm). Overall, five 70-cm-long samples were considered, for each type of fabric and impregnation carried out, which brings to a total of 45 samples. In the second case (i.e. “dried samples”) the procedure carried out consisted in drying the samples for 48 hours inside a specific oven, at a temperature of 60°C, and in their subsequent weighing. In particular, the samples left to dry coincide with those used for density determination. The samples considered for each type of fabric and impregnation carried out are 10, for a total of 90 samples. The data obtained were finally used to determine the linear density, expressed in g/km, by using the following expression: = 1000 ∗ [ ⁄ ] (2.1) where: 2.3. Physical Characterization