STIFF AND DUCTILE NANOCOMPOSITES OF EPOXY REINFORCED WITH CELLULOSE NANOFIBRILS

摘要

Polymer-matrix composites have been a material of choice for a long time now. In view of the recent awareness in environmental changes, a considerable effort has been diverted to study materials obtained from bio/renewable sources as a potential substitute to synthetic/petroleum based products. A significant leap in this direction has been the use of plant fibers (jute, sisal etc) as the reinforcing phase in polymer composites. In addition to the green aspect, plant fibers are the low-cost-low-density replacement of their glass/carbon counterparts. However, both glass and plant fibers result in increased brittleness, although the strength and stiffness increase favorably. Epoxy is one of the most widely used class of thermosets, which finds applications in varied fields - adhesives, coatings, as a matrix in composite materials etc. Epoxy composites with glass fibers and natural fibers as reinforcement have been studied extensively. Recently, there has been increased interest in epoxy based nano composites with most of the attention focused on carbon nano tubes [1, 2] and nano cellulose [3-6] as reinforcements. Cellulose nano fibrils extracted from the plant fibers' cell wall have emerged as a viable alternative for advanced mechanical properties. Cellulose fibrils, composed of crystalline and disordered regions, are the main load bearing structure in the plant cell walls and cellulose crystals have a modulus of 137 GPa [7], which explains the superior mechanical reinforcement of their nano fibrils. It has also been shown that cellulose nano fibrils have a less detrimental effect on the strain to failure resulting in more ductile materials [8]. Small amounts of nano cellulose reinforcements with epoxy matrix are extensively reported in the literature [9-13]. In this work, an attempt has been made to address the issue of brittleness in epoxybased composites by using nano fibrillated cellulose (NFC) obtained from commercial pulp. Also, the potential large-scale application of the composite is demonstrated with the preparation a 3D molded nanocomposite shell element.