Valorization of Rice Straw into Cellulose Microfibers for the Reinforcement of Thermoplastic Corn Starch Films

Abstract

[EN] In the present study, agro-food waste derived rice straw (RS) was valorized into cellulose microfi-bers (CMFs) using a green process of combined ultrasound and heating treatments and were, thereafter, used to improve the physical properties of thermoplastic starch films (TPS). Mechanical defibrillation of the fibers gave rise to CMFs with cumulative frequencies of length and diameters below 200 and 5¿15 µm, respectively. The resultant CMFs were successfully incorporated by melt mixing into TPS and also starch subjected to dry heating (DH) modification to yield TPS modified by dry heating (TPSDH) by thermo-compression and characterized. It was observed that both DH modification and fiber incorporation at 3 and 5 wt% loadings interfered with the starch gelatini-zation, leading to non-gelatinized starch granules in the biopolymer matrix. Thermo-compressed films prepared with both types of starches that wereand reinforced with 3 wt% CMF were more rigid (percentages increases of ~215% for TPS and ~207% for the TPSDH), more resistant to break (~100% for TPS and ~60% for TPSDH), but also less extensible (~53% for TPS and ~78% for TPSDH). The incorporation of CMFs into the TPS matrix at both contents also promoted a de-crease in water vapor (~15%) and oxygen permeabilities (~30%). Finally, the TPS composite films showed low changes in terms of optical properties and equilibrium moisture, being less soluble in water than the TPSDH films.