Novel Biocomposites from Microfibrillated Cellulose grafted with Poly(ε-caprolactone) – Synthesis and Characterization

Environmental concerns have led to a rapid growing interest in replacing traditional petroleum-based technology with more green alternatives. Cellulose, one of the main components in plants, is a biodegradable and renewable recourse. The use of cellulose fibers, instead of traditional fibers such as glass and carbon, offers a way to make more environmental friendly biocomposites. By replacing the traditional fibers with cellulose fibers several benefits are achieved, such as low density, low cost, good specific mechanical properties, reduced tool wear, and biodegradability.[1] Microfibrillated cellulose (MFC) is moderately degraded, nano-sized cellulose, which exhibits unique properties with high modulus and strength, and at the same time a high aspect ratio.[2] These are important properties for development of novel, environmentally friendly, cellulose-based biocomposites, suitable for high-performance applications. Nevertheless, there are limitations restricting the use of cellulose fibers, or nano-sized cellulose as reinforcements and the most important one is the poor compatibility between the hydrophobic polymer matrix and the hydrophilic cellulose fiber.[3] Firstly, this causes difficulties in dispersion of the fiber homogenously in the matrix. Secondly, the poor compatibility gives rise to low interfacial adhesion between the components. Thereby, when the material is subjected to a tensile force, the performance of the material is limited by fiber-pull out rather than fiber-break. Hence, the full potential of the cellulose fiber as reinforcement is not utilized, and in order to do so the compatibility between the hydrophobic matrix and the hydrophilic fiber must be improved. This can be obtained by grafting of a nonpolar polymer from the cellulose surface.[4]