Manufacturing Aspects of Bast Fiber-Based Composites

The Evolution and Future Trends of Unsaturated Polyester Biocomposites: A Bibliometric Analysis

“…A common strategy to reduce the polar character of natural fibers to improve resin wettability is via fiber modification. Several studies, including complete and extensive reviews, have focused on this topic [3,5,10,14]. Generally, fiber modification, also known as fiber treatment, involves the reduction of non-cellulosic components using alkaline treatments, and the introduction of new and less-polar functional groups by reducing the OH groups of the fiber or altering the fiber surface roughness.…”

“…The rest of the identified treatments can be categorized into five strategies: (a) treatment using silane agents that contain groups with a chemical affinity to UPR matrices, such as aminopropyltriethoxysilane [53,54] or 3-methacryloxypropyltrimethoxysilane [48]; (b) the use of diverse acids, anhydrides, or esters to convert OH groups by esterification or transesterification reactions into less-polar ester groups-one of the most common methods include introducing double bonds onto the natural fiber surface, which improves the resin wettability using maleic anhydride [55,56]; (c) physical processes involving the use of plasma treatment [57,58], as in the case of Sarikanat et al (2016) [59], who used Ar and air atmospheric-pressure plasma treatments to improve the mechanical properties of flax biocomposites; (d) thermal treatment, such as steam explosions combining temperature and pressure, which reduces non-cellulosic components affecting the chemical and morphological structure of the remaining fiber structures-this process usually involves the development of binderless boards [3], but it is also useful for UPR biocomposites, as shown in the work of Brugnago et al (2011) [60], to reduce the content of the non-cellulosic components of the vegetable fibers; and (e) interactions between natural fibers and monomers or polymers. Monomers can be useful for inducing grafting modifications onto fiber surfaces [61].…”

“…Several strategies have been proposed for reducing this impact. One of the most-documented methods to date is the use of natural fibers [3][4][5]. These composites are part of the recently called biocomposites [6,7].…”