## 3 Results
### Physicochemical Characterization
The water content remains similar in all collagenic leather substrates (#1, #2, #3, #7, #8, #9, and #10), and is lower for the three alternative materials. The ash content is quite high in the alternative materials leatherette (#4) and Pinatex (#5), which indicates the presence of inorganic substances in the composition of the materials. Sheepskin also has a high ash content, due to its capacity to absorb chrome salt, in comparison to the collagen content; it is a more porous skin than bovine hide. The nitrogen contents of the leathers were found to be significantly higher compared to the alternative materials since the leathers consist of protein which is a huge source of nitrogen. The nitrogen content is comparable for all analyzed leather substrates (#1, #2, #3, #7, #8, #9, and #10). Conversely, for the alternative materials, the nitrogen content is lower, especially for the Desserto material (#6). The pH of all the samples remains similar, except for the Desserto material (#6), which has a higher value of 5.8. Comparing the chromium content of the samples, the samples of sheepskin (#1) and bovine wet-blue (#2) as well as the leatherette (#4) have a high chromium content, owing to the use of chromium (III) salts. Leather samples #9 and #10 have some chromium content due to the use of a dye that contains chromium. The leatherette (#4) has a high iron content (2.6%), as well as high aluminum (3948 ppm) and titanium (500 ppm) contents. In the Pinatex (#5) and Desserto (#6) materials, the total metal content remains below 1000 mg/kg. The formaldehyde content is less than 10 mg/kg in most samples; only sample #1 contains a value of 10.5 mg/kg. All samples fall below the regulation of 75 mg/kg in articles that are in contact with human skin and 150 mg/kg for articles that do not have contact with the user's skin. The leather samples (#1, #2, and #3) show comparable values, the burst strength value being higher for the vegetable-tanned sample. The leather samples from #7 to #10 are also comparable. The tear resistance of articles #7 and #8 is notable. The alternative material samples, especially the leatherette (#4), show much lower resistance values in all categories tested. The tensile strength is very low compared to collagen or natural leather samples. Only the Pinatex material (#5) exhibits a tear resistance similar to the leather samples. The water vapor permeability values, associated with the breathability of the materials, are similar for the leather substrates, with the lowest value corresponding to the vegetable-tanned leather, due to the thickness and market of the article. Of the alternative materials, only the Pinatex material exhibits water vapor permeability. The shrinkage temperature of the chromium-tanned leathers (#1 and #2) reaches values above 100 \({}^{\circ}\)C; the vegetable-tanned leather (#3) remains at 81 \({}^{\circ}\)C. The wet-white leather substrates retanned with sodium alginate (#7, #8, #9, and #10) reach values between 68 and 72 \({}^{\circ}\)C, typical for this type of tanning. With respect to the shrinkage temperature of the alternative materials, the leatherette (#4), the Pinatex material (#5), and the Desserto material (#6) reach values above 140 \({}^{\circ}\)C since they do not contain collagen. Differences can also be observed among the alginate-based leathers. Samples #9 and #10, which contain Tara, show lower values in tensile strength, burst strength, and tear load compared to sample #8, which does not contain Tara, as Tara creates a more rigid and less flexible structure.