Utilization of Pineapple Crown Fiber and Recycled Polypropylene for Production of Sustainable Composites

Abstract

Nowadays, the production of consumer goods is based on the use of non-renewable raw materials, which in recent years has been performing as a problem for the environment. Considering the large number of available biofibers in nature, their use in the development of polymeric composites has inevitably emerged, it is also necessary to take into account the countless discarded plastics that still have the potential to be reused. In this work, fibers were extracted from pineapple crown residues and utilized to compose sustainable composites using recycled polypropylene from cups discarded in the trash as a matrix. However, it is known that for good performance, it is necessary to achieve a good chemical interaction between the fiber and the matrix. In order to improve this interaction, alkaline mercerization treatment was carried out on the surface of the fibers removing some components incompatible with the polymer. In this work, the effect of the mercerization treatment on the properties of the fibers was studied, as well as their interaction with the matrix. The effect of fiber concentration on the mechanical and thermal properties of composites was also evaluated. Levels of 5 and 7 wt% were used for both natural and mercerized fibers. A decrease in the number of degradation stages was observed through thermogravimetry analyses (from four in natural fiber to two in mercerized fibers), showing that the mercerization performed on the fibers was effective. An increase in the degree of crystallinity of mercerized fibers was also observed through the results of X-ray diffraction. Both techniques indicate that amorphous compounds, such as hemicellulose and lignin, were partially removed. Through the tensile test, it could be noted that all composites presented higher values of de elastic modulus than recycled polypropylene without added load; however, there were no differences in the elastic modulus between the different types of fibers and load levels. Therefore, it is interesting to use fibers as reinforcing agents in polymers; however, the treatment did not increase the mechanical properties of the composites. In parallel, other factors, such as the dispersion of the components, must be taken into account to justify this result.