Enhanced Carboxymethyl Cellulose Based on Empty Fruit Bunches in a High Degree of Substitution and Thermal Stability as a Biocomposite Film Backbone

Abstract

Carboxymethyl cellulose (CMC), a water-soluble cellulose, can be derived from oil palm empty fruit bunches (OPEFBs). In addition to being highly soluble, it is essential for CMC to exhibit excellent thermal stability when utilized in biocomposites. Reactants in the alkalization and etherification steps to provide high DS of CMC-based OPEFB have not been standardized. The research aimed to optimize the alkalization and etherification processes using a response surface methodology (RSM). This will help in determining the optimal ratios of 30% NaOH (the center point of 3), isopropanol (the center point of 30) as maceration media, and monochloroacetic acid (the center point of 1.2) needed for the cellulose. RSM determined the optimum ratio of 30% NaOH to OPEFB cellulose, which was 3.36 : 1, an isopropanol ratio of 30.62 : 1, and an MCA to cellulose ratio of 1.19 : 1. The optimization indicates that the OPEFB cellulose-based CMC have a high degree of substitution of 1.28 and a carboxymethyl content of 31.93%. CMC morphology showed noticeable changes, such as a smoother surface and swelling. There was a significant increase in the wavenumber of 1580 cm−1 due to the presence of carbonyl groups. The OPEFB-based CMC resulted in a crystallinity of 40.18%, and thermal gravimetric analysis indicated that mass decreases occurred at high temperatures of 500°C, which suggests that the optimal CMC has a high thermal stability. OPEFB-based CMC exhibits a high degree of substitution and resistance to thermal degradation, which makes it suitable for further use as the main material in biocomposite films.