High-Performance-Tensile-Strength Alpha-Grass Reinforced Starch-Based Fully Biodegradable Composites

Abstract

aThough there has been a great deal of work concerning the development of natural fibers in reinforced starch-based composites, there is still more to be done. In general, cellulose fibers have lower strength than glass fibers; however, their specific strength is not far from that of fiberglass. In this work, alpha-fibers were obtained from alpha-grass through a mild cooking process. The fibers were used to reinforce a starch-based biopolymer. Composites including 5 to 35% (w/w) alpha-grass fibers in their formulation were prepared, tested, and subsequently compared with those of wood-and fiberglass-reinforced polypropylene (PP). The term "high-performance" refers to the tensile strength of the studied composites and is mainly due to a good interphase, a good dispersion of the fibers inside the matrix, and a good aspect ratio. The tensile strength of the composites showed a linear evolution for fiber contents up to 35% (w/w). The strain at break of the composites decreased with the fiber content and showed the stiffening effects of the reinforcement. The prepared composites showed high mechanical properties, even approaching those of glass fiber reinforced composites. Keywords INTRODUCTIONIt is commonly accepted that biopolymers and bio-fibers have the potential to replace or reduce the consumption of fossil fuel-derived plastics. In addition, to facilitate the recycling of these materials, such replacement should lead to reductions in energy consumption, pollution, and CO 2 emissions. Hence, fiber-reinforced composites are often described as eco-friendly materials. However, the mechanical properties and/or the price of such composites have rendered them inadequate for many applications to date. In general, cellulosic fibers have inferior strength compared to their synthetic counterparts, such as aramid, carbon, and glass fibers.Due to their lower density, some natural fibers have a specific strength not far from those of fiberglass. On the other hand, bio-based matrices (such as polylactic acid or polyhydroxybutyrate) remain more expensive than petroleum-derived polymers. Nevertheless, thanks to their price/performance balance, ongoing innovations are offering new commercial opportunities for bio-based polymers and their composites in several applications. PEER-REVIEWED ARTICLEbioresources.com Gironès et al. (2013). "Alpha/starch composites," BioResources 8(4), 6121-6135 6122Compared to lactones, butyrates, valerates, and other monomers used for the synthesis of biodegradable polymers, starch is an inexpensive product whose transformation into a thermoplastic polymer can be accomplished in a rather straight-forward manner (Coombs and Hall 1998;Teixeira et al. 2007;Averous and Halley 2009;Dogossy and Czigany 2011;Gandini 2011). As a result, thermoplastic starch (TPS) is considered one of the most promising biopolymers for large-scale applications. During the last few decades, TPS has received considerable attention among the scientific world (John and Thomas 2008;Belhassen et al. 2009;Cañigueral et al. 2009;Cha...

High Stiffness Performance Alpha-Grass Pulp Fiber Reinforced Thermoplastic Starch-Based Fully Biodegradable Composites

“…The 150-min treatment was chosen as satisfactory for obtaining AF with enough stiffening capabilities. Moreover, in a recent article (Gironès et al 2013) the authors found that the same cooking time was enough to obtain fibers with the required quality to create good fiber-matrix interphases. If the data are introduced in the rule of mixtures (Eq.…”

“…The main goal of cooking the alpha-grass was to remove the extractives and ash, thus obtaining neat fibers with high cellulose content and a surface capable of chemical interaction. A good fiber-matrix interphase is very important for obtaining composite materials with good mechanical properties (tensile, flexural, and impact strength) (Girones et al 2013). Moreover, it is important to retain the lignin content, as it influences the intrinsic modulus of the fibers, and at the same time has little influence in the fiber-matrix interaction (Neagu et al 2006).…”

“…The series is designed to study the tensile strength, stiffness, the flexural, impact and thermal properties, as well as the sound and thermal insulation capabilities of such materials. The already published paper (Gironès et al 2013) deals with the tensile strength of the composite materials and the intrinsic tensile strength of the fibers, as well as the micromechanics of the tensile strength properties. The first article of the series established the benefits of using alpha fiber in place of glass fiber (GF) for reinforced polyolefin composites.…”

“…The number of indexed studies dealing with the mechanical properties of Mater-bi®-Y reinforced composites is scarce, numbering five. There have been studies of the tensile properties of natural fibers reinforced Mater-bi®, but the Young's modulus has been considered only superficially and used to compute micromechanical parameters (Gironès et al 2013;Lopez et al 2012c). Other work has considered the impact of chemical modifications or processing conditions on the macro mechanic aspects of the tensile properties (Alvarez et al 2005;Alvarez and Vazquez 2006).…”

Effect of Mesh Number of Wood Powder and Ratio of Raw Materials on Properties of Composite Material of Starch/Wood Powder

“…Starch is the second most abundant renewable polymer found in nature after the lignocellulose group and it is relatively inexpensive (Girones et al 2013). Because of its low cost, renewability, biodegradability, and lack of toxicity or smell, it has been considered for many years to have high potential for use in packing and disposable items instead of petroleum-based polymers (Kaewtatip and Thongmee 2013;Zuo et al 2014).…”