Creating Hierarchical Structures in Renewable Composites by Attaching Bacterial Cellulose onto Sisal Fibers

Abstract

underexploited. This paper describes a new approach to producing hierarchical composite structures from completely renewable resources. Bacterial cellulose was introduced as a nanoscalereinforcementbyattachingittothesurfaceofnatural fibers, in this case sisal. The natural fibers have micrometerscale diameters, and although they themselves have a hierarchical internal structure, the deliberate introduction of the nanofiller provides a new means of controlling their interaction with and the behavior of the matrix. The modified sisal fibers were incorporated into a bioderived polymer matrix, poly(L-lactic acid) (PLLA), to obtain a new class of hierarchical composite that is both derived from renewable resources and biodegradable. The attachment approach facilitates modification of the fiber surface and avoids the problems commonly associated with agglomeration and dispersion of nanofillers; the result is a rise in interfacial adhesion to the polymer matrix, and an associated improvement in the performance of the composite. The effects of modifying sisal fibers, both in their natural state (Sisal-N) and after extraction withacetone(Sisal-A),wereassessedqualitativelybySEM,and quantitatively by single-fiber tensile and pull-out (interfacial shear strength) tests. The hierarchical-composite performance was determined using compression-molded samples loaded in tension, parallel (08) and perpendicular (908) to the primary reinforcing fibers; the response to water immersion was also explored.