Synthesis of starch graft-copolymers via reactive extrusion: Process development and structural analysis

Abstract

Graft-copolymers of starch and acrylamide monomer were prepared via reactive extrusion. Solvent-free graft copolymerization of starch at high solid concentration was completed within 5 minutes. An average monomer conversion of 80% and grafting efficiency of ~74% was achieved. The starch type influenced the grafting reaction and properties of graft-copolymers. The starch-copolymers swelling behavior is comparable to that of synthetic hydrogels.

Recent advances in starch‐based films toward food packaging applications: Physicochemical, mechanical, and functional properties

“…Morphological modification is also a common strategy that is utilized to change starches' functional properties to give porous starch or starch nanoparticles (NPs) (Li, Zhao et al, 2018;Oliyaei, Moosavi-Nasab, Tamaddon, & Fazaeli, 2020;Xiang et al, 2016;Yang et al, 2017). Enzymatic modification by pullulanase, an enzyme that cleaves (1,6)-α-D glycosidic linkages, can also effectively change the amylopectin to amylose ratio (Abidin et al, 2018; Although most of these modification strategies involve fairly simple synthetic reaction steps, much attention has recently been focused on developing and optimizing processes for reactive extrusion of starch, opening the door for further commercialization of starch-based products (Fitch-Vargas et al, 2019;Fonseca-Florido et al, 2019;Jebalia et al, 2019;Kaisangsri, Kowalski, Kerdchoechuen, Laohakunjit, & Ganjyal, 2019;Liu et al, 2019;Milotskyi, Bliard, Tusseau, & Benoit, 2018;Nessi et al, 2019;Siyamak, Laycock, & Luckman, 2020;Tian, Zhang, Sun, Jin, & Wu, 2015;Ye et al, 2019). Although chemical modification of starch typically diminishes the mechanical properties of the resultant films by causing less efficient polymer packing and subsequent decreases in film crystallinity, modified films can exhibit some improvements in some mechanical properties (Table 2, entries 40 and 41) as well as oftentimes leading to better barrier properties or increased compatibilization with additives that can offset the decrease in properties (Table 2, entries 10 and 38) or can endow the film with additional function while decreasing the potential for retrogradation (Colussi et al, 2017;Fu et al, 2019).…”

Functional starch-based hydrogels: renewable material solutions for wastewater and agriculture industries

“…Similarly, the characteristic peaks of AAm are present in the spectra of all copolymers at 3290, 1668, 1568, and 1448 cm −1 corresponding to the N−H stretching, C=O stretching, N−H bending, and −C−N stretching vibrations of amide groups, respectively (Siyamak et al, 2020b). The stretching vibrations of O=S=O in the sulfonic group of AMPS also appear at 1130 cm -1 .…”

“…Additionally, since these copolymers are soluble in water, their interactions with H2O molecules (hydrogen bonds) can shield the NWS protons, causing their resonances to shift upfield. Therefore, the overlapping of the H2O and NWS backbone protons resonances in this sample results in a broader signal appearing at 3.7 ppm (Siyamak et al, 2020b).…”

“…Then, Deionised water (DIW), AAm (50 wt.%), AMPS (20 wt.%), and APS (5 wt.%) solutions were sequentially injected into barrel sections 1, 2, 3 and 5 using peristaltic pumps (Masterflex ® ) ( Figure 6-1). While the feed-rates were selected based on the findings of previous studies (Siyamak et al, 2020b;Travas-Sejdic & Easteal, 2000b;Willett & Finkenstadt, 2015), the main factors that can influence the extrusion process, and the properties of the extrudates were given due consideration. These included the impact of using wheat-starch instead of corn-starch, and the operational differences when using a benchtop extruder in place of the industrial-scale extruders cited in the literature.…”

“…Non-food grade wheat-starch is a by-product of the wheat industry, which is of high economic importance to Australia. To close this gap, we prepared a class of cost-effective hybrid copolymers based on non-food grade NWS, unsaturated AAm, and AMPS comonomers via REx method using a laboratory-scale co-rotating twin-screw extruder within 5 minutes of extrusion (Siyamak et al, 2020b). We applied a starve-feeding method during the extrusion to minimise the required amounts of water and toxic chemicals.…”