Synthesis and Characterization of Hybrid Micro Crystalline Cellulose - Montmorillonite Nanoclay Filled and Sorbitol Plasticized PolyLactide Acid for Structural Application

Abstract

PolyLactide Acid (PLA) is a polyester made from renewable resources such as fermented starch of corn, maize, sugarcane, etc. It’s a renewable, biodegradable, biocompatible, and high strength polymer designated to substitute petroleum-based polymers. However, it has low performance in some mechanical properties, such as impact strength, and its thermal stability limits its utilization for structural applications. The main objective of this study was to modify the properties of PLA through hybrid microcrystalline cellulose (MCC)-montmorillonite (MTT) fillers and sorbitol (S) plasticizer for the structural application due to their renewability, biodegradability, nontoxicity, and less weight. Among the factors, MCC was extracted from coffee husks through sequential chemical treatments: de-waxing (DW), alkali treatment (AT), and bleaching (BL). The effect of factors such as weight percentage of MCC (0, 3, 6, and 9), MTT (0, 3, 6, and 9), S (10, 20, 30 and 40), and temperature (T) (100, 125, 150, and 1750C) on flexural strength (FS), flexural modulus (FM), tensile strength (TS), young modulus (YM), impact strength (IS), hardness value (HV), water absorption (WA), and density (D) were investigated through Taguchi’s based Grey relational Analysis (GRA). The obtained results of chemical composition analysis showed that the cellulose, hemicellulose, lignin, extractive and ash content were (52.9%), (12.5%), (21.9%), (9.4%), and (2.4%), respectively. The sequential chemically treated sample showed a higher crystallinity index (CI), i.e., 89.9%, in the MCC region with 54.7% yield and has great thermal stability at high temperature. The synthesized MCC/MTT/S/PLA hybrid bio-composite global optimum result obtained for FS, FM, TS, YM, IS, HV, WA and D were MCC at level 3 (6%), MTT at level 4 (9%), S at level 2 (10%), and T at level 4 (1750C). ANOVA showed that MTT has the greatest significant effect on mechanical and physical properties of MCC/MTT/S/PLA bio-composite, followed by MCC, T, and S. The confirmation test indicates the improvement of weighted Grey Relational Grade (GRG) from 0.7896 to 0.846. Further, the FTIR, XRD, TGA/DTA, and SEM results indicated that the good interaction between PLA and fillers improved the thermal and morphological properties of optimal (6MCC/9MTT/10S/1750C) bio-composite samples. Therefore, the multiple quality characteristics of MCC/MTT/S/PLA bio-composite material can be a possible candidate for various structural applications.