Bleached Kraft Eucalyptus Fibers as Reinforcement of Poly(Lactic Acid) for the Development of High-Performance Biocomposites

Abstract

Poly(lactic acid) (PLA) is one of the most well-known biopolymers. PLA is bio-based, biocompatible, biodegradable, and easy to produce. This polymer has been used to create natural fiber reinforced composites. However, to produce high-performance and presumably biodegradable composites, the interphase between PLA and natural fibers still requires further study. As such, we aimed to produce PLA-based composites reinforced with a commercial bleached kraft eucalyptus pulp. To become a real alternative, fully biodegradable composites must have similar properties to commercial materials. The results found in this research support the competence of wood fiber reinforced PLA composites to replace other glass fiber reinforced polypropylene composites from a tensile property point of view. Furthermore, the micromechanics analysis showed that obtaining strong interphases between the PLA and the reinforcement is possible without using any coupling agent. This work shows the ability of totally bio-based composites that fulfill the principles of green chemistry to replace composites based on polyolefin and high contents of glass fiber. To the best knowledge of the authors, previous studies obtaining such properties or lower ones involved the use of reagents or the modification of the fiber surfaces.

Impact Strength and Water Uptake Behavior of Bleached Kraft Softwood-Reinforced PLA Composites as Alternative to PP-Based Materials

“…It is known that to increase the mechanical properties of PP/GF materials, adding a coupling agent like polypropylene functionalized with maleic anhydride (MAPP) has a noticeable impact, and is common in the formulation of the commercial materials. Based on previous works, uncoupled and coupled material batches were prepared [ 20 , 21 , 25 ]. The coupled composites added 6% of MAPP against reinforcement content.…”

“…Despite the natural fibers being lighter than GF, the density of the PLA in front of PP affects noticeably the specific property of its composites. Nonetheless, the high tensile and flexural properties of PLA/BKSP composites can equalize these disadvantages [ 20 , 21 , 25 ]. Every case must be studied in detail and the advantages of fully biodegradable and bio-based materials in front of non-biodegradable materials based on perishable resources must be part of the decision.…”

“…Although the benefits of the use of a renewable and recyclable resource like lignocellulosic fibers as reinforcement, this kind of fibers show some limitations: difficulties in the dispersion of the reinforcement in the matrix due to the different polarities of the phases; an increment of the water uptake also related with the polarity of the fibers that can produce a reduction in the mechanical properties of the composite and limit its application; a limited range of process temperatures as the degradation of natural fibers starts around 200 °C [ 17 , 18 ]. However, PLA composites from cellulosic fibers have been produced previously showing interesting mechanical and thermal properties [ 19 , 20 , 21 , 22 , 23 ]. The PLA and bleached Kraft softwood pulp (BKSP) compounds have been studied from their behavior in terms of tensile strength, where the results revealed that lignin has a negative effect on the interface of PLA composite materials.…”

“…A similar effect is observed in the thermal expansion coefficient where the composites showed lower values because of the restrictions of the fibers [ 23 , 26 ]. On the other hand, it has been found that other bleached fibers such as bleached kraft hardwood pulp fibers also exhibit similar behavior [ 20 ]. Nevertheless, the impact and water uptake behaviors of these composites are seldom evaluated.…”

High-Yield Lignocellulosic Fibers from Date Palm Biomass as Reinforcement in Polypropylene Composites: Effect of Fiber Treatment on Composite Properties

“…The Bowyer–Bader solution to the Kelly–Tyson equation was applied. The Bowyer–Bader solution estimates the as the product of the intrinsic tensile modulus of the fiber and the tensile elongation of the composite material ( ) [ 50 ]. The Kelly–Tyson equation can be expressed as the orientation factor ( ) by the sum of the contributions of fibers of subcritical length ( X ) and supercritical length ( Y ), plus the contribution of the matrix ( Z ); Equation (4).…”