The linearization of adsorption equations is controversial. The estimation of fitting parameters strongly depends on the linearization method, magnitude of experimental error, and data range. Although many studies contrast linear versions of these equations with their non-linear counterparts, linearization is preferred due to its simplicity since a line could be represented with fewer experimental points than a curve. An in-depth analysis was carried out to compare the accuracy of linear and non-linear models. Although different transformations linearize Langmuir isotherms, only one form yields reliable fitting parameters. Linear transformations could also lead to a statistical bias, favoring a model that does not represent the experimental behavior. Similar observations are discussed regarding the pseudo-second-order kinetic model. Linearization of Freundlich isotherms, pseudo-first-order kinetic models, and fixed-bed adsorption models through logarithms implies that attention must be taken on the logarithm limits by properly selecting the data range. Linearization also promotes the incorrect interpretation of models due to oversimplification. The linearized van’t Hoff equation would yield a reasonable fit with fewer experimental points than the non-linear regression, which requires more data to assure convergence. In this sense, there is convincing evidence that non-linear regression is a more robust and reliable tool for adsorption modeling.

In this study, natural fibers (agave, coir, and pine) were surface treated with maleated polyethylene (MAPE) with two main objectives: (1) to improve the mechanical properties of natural fiber composites produced by rotational molding and (2) to increase the fiber content in the composite. The rotomolded composites were produced at 0, 10, 20, 30, and 40% wt. of fiber contents (treated or untreated) and characterized in terms of morphology and mechanical properties (hardness, impact, tension, and flexion). The results showed that MAPE surface treatment was more successful for agave and coir than for pine fibers due to their respective chemical composition. In general, surface treatment led to better fiber distribution and a more uniform composite morphology allowing the possibility to use higher fiber contents in rotational molding. At low fiber contents (10 and 20% wt.), the mechanical properties were improved using treated fiber composites (TFC) compared to the neat polymer and untreated fiber composites (UFC). Although the mechanical properties of TFC decreased at high fiber contents (30 and 40% wt.), they were substantially higher (about 160, 400, and 100% for impact, tensile, and flexural properties, respectively) than for UFC.

Due to its renewability and biodegradability, biopolymers have developed interest in order to substitute oil-derived plastics. In particular, polylactic acid (PLA) is a promising biopolymer in terms of mechanical and biodegradable properties that is used for different applications. Nevertheless, PLA has some disadvantages like brittleness and processing instability. In order to overcome these drawbacks, it has been blended with natural fibers, leading to a fully biodegradable biocomposite material with enhanced properties. However, blending a hydrophobic biopolymer with hydrophilic fibers leads to poor interfacial adhesion producing interfacial voids, cavities and defects and consequently low performance properties. In this sense, this article reviews different strategies of biopolymer functionalization to improve compatibility in biocomposite materials. First, the effect of different parameters on biopolymers functionalization via melt and reactive extrusion processes is discussed. Finally, coupling efficiency of functionalized biopolymers is analyzed in terms of mechanical and thermal properties.