Revaluation of Guadua Fiber for the Sustainable Production of Recycled Thermoplastic Composites with Potential Industrial Applications and Their Corresponding Life Cycle Analysis

Plastics are widely used in manufacturing various products due to their durability, strength, and low cost; however, they originate from nonrenewable sources. The growing interest in developing environmentally friendly materials has driven research toward the incorporation of natural fibers and recycled plastics. In Ecuador, Guadua Angustifolia Kunth (GaK) bamboo is usually used as furniture and construction materials. Therefore, this research work aims to reevaluate the traditional use of GaK fibers, exploring the potentiality of using chemically treated GaK fibers as reinforcement material for thermoplastic composites. This study presents the development of composite materials based on high-density polyethylene (HDPE), recycled HDPE (rHDPE), and treated GaK fibers, using an experimental design that includes performing tension, flexural, and impact tests to obtain an optimal composite material formulation. The composites were characterized using optical microscopy, SEM, FTIR, DSC, TGA, and EDX, followed by a life-cycle assessment (LCA). SEM images revealed morphological changes in the treated fibers, while TGA indicated significant mass loss due to degradation above 200 °C in all composites and DSC showed a melting temperature of approximately 133 °C for all samples. These results indicated there will not be significant GaK fiber degradation during processing. The highest maximum tensile strength achieved among all the optimization samples was 18.69 MPa. All composites showed an increase in Young's modulus, with enhancement up to 204% compared to pure HDPE, albeit with a marked reduction in elongation percentage. The maximum flexural strength increased to approximately 17.84%, but the impact strength decreased by 83% due to the low fiber-matrix compatibility and the low ductility of the composite, which allows it to absorb less energy before fracture. The optimal formulation had 10% cellulose, 50% HDPE, and 40% rHDPE, which exhibited a maximum tensile strength of 17.62 MPa, obtained from a mixture design regression. LCA demonstrated that rHDPE-based optimal formulation has a significantly lower environmental impact compared to virgin HDPE. Using rHDPE is critical for reducing the environmental footprint of composites, and incorporating GaK fibers further decreases GWP emissions while enhancing certain properties.