Upcycling Polymers and Natural Fibers Waste—Properties of a Potential Building Material

Composites of recycled high-density polyethylene and micro fibres of sugarcane bagasse were studied, in order to create an upcycled material to produce masonry bricks. We ranged the polymer/filler ratio from 100–0 to 60%–40%. The materials were assessed through scanning electron microscopy, thermogravimetry/derivative thermogravimetry, differential scanning calorimetry, rheological measurements and compressive strength test. The composites showed a good dispersion and adhesion of the filler into the polymeric matrix. There was no significant variation on the melting and crystallizing temperatures of the materials if compared to those of neat polymer, indicating that there was no relevant change in the average size of the polymeric crystals. We assumed that some transcrystallization has happened, because the degree of crystallinity of the composites increased to all filler contents, while the crystallizing temperature remained the same. There was a rise in the compressive moduli of the composites, ranging from 37% to 63%. The modulus at the crossover point and the complex viscosity also rose due to the fibres ratio. The results show that the combination of these materials led to the reinforcement of the compressive strength of the polymer, and have interesting properties as a potential building material.