Physical Properties of Thermoplastic Cornstarch/Hibiscus sabdariffa Fiber Obtained by Evaporation Casting

Abstract

Hibiscus sabdariffa is a typical ingredient in a popular Mexican beverage, and a lot of waste is produced as a result. The fibers obtained from Hibiscus sabdariffa waste can be used as reinforcement in a natural composite. This research evaluates the influence and effect of different properties of fiber incorporated into a cornstarch matrix. The mechanical and thermomechanical performance is evaluated using tensile measurements and dynamic mechanical analysis. Thermal stability is analyzed by thermogravimetric analysis. The micrographics show a good incorporation of the bioreinforcement into the polymer matrix. The tensile measurements show that the fiber can be related to a slight decrease in Young´s modulus. The dynamic mechanical analysis results show that the composite with 4 wt% of reinforcement has a higher storage modulus (1139 MPa at 50 °C) than the starch matrix (854 MPa at −50 °C). According to the thermal stability of the composites is displaced to lower temperatures, which can suggest an effect of biodegradation acquired with the progressive addition of the biofibers. As a result, the composites obtained have been shown to be sustainable and friendly to the environment, and the films can offer an advantage for packaging-type bags for foods.

Evaluation of Starch–Garlic Husk Polymeric Composites through Mechanical, Thermal, and Thermo-Mechanical Tests

“…Figure 2b,c, and d show the starch-GH composites. In the images, you can see the absence of separation of the composite, where the reinforcement is completely wet by the matrix, which indicates that the films have a good interaction and compatibility, as has been reported in other investigations where starch has been reinforced with hibiscus or keratin fibers [12,38].…”

“…In addition, they do not present saturations or agglomerations when GH particle content increases. This is apparent by the homogeneous distribution, as has been presented in other investigations in which natural fibers have been used [ 12 , 38 , 39 ]. In addition, adding particles up to 10 wt % allows for good embedding.…”

“…GH particles were added at 2–10% ( w / w ). The solution was heated at 90 ± 5 °C for 10 min with mechanical stirring [ 12 ]. The solution was then poured into silicone molds and allowed to cool for 24 h at 30 °C.…”

“…GH particles were added at 2-10% (w/w). The solution was heated at 90 ± 5 • C for 10 min with mechanical stirring [12]. The solution was then poured into silicone molds and allowed to cool for 24 h at 30 • C. Table 1 shows the corresponding concentrations and nomenclature used in the synthesis and characterization of composites.…”

“…A few researchers have focused on the development of plastic materials that are friendly to the environment and have searched for combinations of natural polymers, including proteins, polysaccharides, and synthetic polymers from both chemical and biological sources, as well as microorganism syntheses [ 10 , 11 , 12 , 13 , 14 ]. Biopolymers represent a group of materials that are formed from natural sources, which implies that they can be disposed without significant damage to the nature; therefore, these kinds of materials represent a good option for applications with a short lifespan.…”