Nonedible Starch Based “Green” Thermoset Resin Obtained via Esterification Using a Green Catalyst

Abstract

In this study, a biobased thermoset resin was developed from a nonedible starch source obtained from mango processing industrial waste. Mango seed starch (MSS) was extracted from defatted mango seed kernels and cross-linked using a “green” cross-linker/catalyst system, 1,2,3,4-butane tetracarboxylic acid (BTCA)/sodium propionate (NaP), to obtain the thermoset resin. The tensile properties of the cross-linked MSS were found to be adequate to replace edible starch based thermoset resins, e.g., potato or corn or proteins such as soy. The cross-linking or the esterification reaction proceeds faster and at lower temperature in the presence of a suitable catalyst. Sodium hypophosphite (SHP), a widely used catalyst for esterification using poly­(carboxylic acid)­s and hydroxyl groups of starch or cellulose, contains phosphorus and the effluents containing SHP, i.e., phosphorus, are toxic to humans and can adversely affect the fauna in water. Also, SHP decomposes to toxic phosphine gas when heated. The results of the present study indicate that sodium propionate (NaP), used as a nonphosphorus green catalyst, is as effective and efficient as SHP. The cross-linking of starch was confirmed directly using ATR-FTIR spectra and the degree of substitution (DS) values obtained by chemical titrations as well as indirectly through an increase in the tensile properties. Higher modulus and strength and lower degree of swelling in water of films cross-linked using NaP confirmed that NaP acts as a better catalyst than the conventional SHP.

Hybrid Drug Delivery Patches Based on Spherical Cellulose Nanocrystals and Colloid Titania—Synthesis and Antibacterial Properties

“…A similar effect was observed by N.V. Patil and A.N. Netravali [ 50 ], who esterified mango seed starch extracted from defatted mango seed kernels using 1,2,3,4-butane-tetracarboxylic acid. Moreover, crosslinking by BTCA significantly reduced the percentage of degradation or the weight loss of the samples.…”

Microfibrillated cellulose‐reinforced nonedible starch‐based thermoset biocomposites

“…Based on the understanding derived from Figure , it can be concluded that MSS was completely gelatinized at 85 °C. Further, the gelatinization temperature of MSS was confirmed using Advance Rheometer‐2000 (TA Instruments, New Castle, DE) equipped with standard steel parallel plate and found to be 80 °C …”

“…This confirmed the esterification reaction between the carboxyl groups from BTCA and the hydroxyl groups from MSS which takes place during the curing (hot‐pressing). The BTCA crosslinks with MSS via anhydride formation (Scheme ) in the presence of the catalyst (NaP) which, in turn, reacts with the hydroxyl groups abundantly present and easily available due to gelatinization of MSS . BTCA and NaP have been used to crosslink cellulose earlier .…”

“…Being pure plant derived cellulose, MFC is also fully biodegradable and sustainable. Further, the MFC/MSS biocomposites were crosslinked using a benign crosslinker, 1,2,3,4‐butane tetracarboxylic acid (BTCA) to improve both mechanical properties as well as water resistance . BTCA was chosen in this research because it is nontoxic in nature and contains four carboxylic acid groups which provide better prospects for reacting with the hydroxyl groups present on both MSS and MFC .…”

“Green” composites using bioresins from agro‐wastes and modified sisal fibers

“…A major concern about utilizing these sources for technical applications is that they are extracted from edible sources. Considering the increased demand for edible proteins and starches in the future, from human and livestock sectors, it is critical to explore the nonedible sources for technical applications, which will not compete with the edible ones in the food security interest . Some agro‐seeds such as Pongamia pinnata (karanja), Azadirachta indica (neem), and Jatropha curcus (jatropha) have received attention in the recent past as the sustainable oil sources for medicinal or bio‐diesel production .…”