Surface modified cellulose nanocrystal incorporated nanocomposites

Abstract

Cellulose nanocrystal (CNC) can be a good alternative to be used as a nanofiller in polymer matrix because of its superior properties such as lightweight, high mechanical strength and elastic modulus, high surface area, etc. Also, CNC has abundant sources and biodegradable material. It is obtained from a variety of cellulose sources. Thanks to these properties, eco-friendly nanocomposites can be produced. On the other hand, it includes a significant drawback. Due to their hydrophilic nature, CNC shows agglomeration in the polymer matrix, especially in the hydrophobic polymer matrix. In the literature, successful results were obtained for CNC nanocomposites by using the solution casting method. However, the solution casting method is not suitable for large-scale production and is not environmentally friendly due to using of solvents such as DMF, THF, etc. Compared to the solution casting method, melt mixing is environmentally friendly as no solvent is used in the production steps. Also, this method can give information about large-scale production. Despite these advantages, agglomeration of CNC is a noticeable drawback for CNC nanocomposites which are produced by using the melt mixing method. To eliminate this drawback, CNC can be modified with some chemical structures by using modification methods such as esterification, amidation, and polymer grafting. In this study, the aim is to obtain a new nanofiller with modification of CNC and produce bionanocomposites since a majority of petroleum-based polymers cause non-degradable wastes in the environment. To solve this problem, biodegradable polymers are crucial. These polymers such as Poly (butylene adipate terephthalate) (PBAT) have a significant potential to be used in commodity and biomedical applications, whereas PBAT cannot show sufficient mechanical properties and its mechanical strength and elastic modulus can be improved with some changes in the structure, for instance, the addition of CNC. In this study, CNC was modified with PGMA by using the grafting from method. Before the modification step, neat PGMA was synthesized and added to the PBAT matrix to observe the effects of PGMA on PBAT. In the PGMA modification of CNC, the polymerization reaction took place on the CNC surface and FTIR analysis was performed to determine changes in chemical structure. In FTIR analysis, a peak at 1725 cm-1 which is related to C=O was obtained. Modified CNCs were introduced in the PBAT matrix with 3 wt.%. Following the production step, thermal and rheological analyses were performed to characterize specimens. With thermal analysis, crystallization behavior and thermal properties were determined as well as with rheological analysis, improvement of dispersion was detected. For PBAT/CNC-g-PGMA5, a dramatic increase was obtained.