Synthesis of Hydrogel Made of Tapioca/Sago Carboxymethyl Starch and Reinforced by Oil Palm Empty–Fruit–Bunch Based Carboxymethyl Cellulose

Abstract

Indonesia is listed as World’s top tier producer of tapioca, sago and oil palm empty-fruit-bunch (OPEFB). In this study, hydrogel was synthesized by combining tapioca-or-sago-based carboxymethyl starch (CMS), OPEFB-based carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA). Carboxymethyl functional group (1620-1618 cm-1) and crystallographic-peak (2θ=20o) were investigated within both CMS samples. Sago-CMS held higher yields (175.49 g/g) than tapioca-CMS. Morphologically, tapioca-CMS granules were oval, round, or polygonal, individual, scattered, full-of-indents/defective-ends, whereas sago- CMS were oval or irregular, intact and exceptionally smooth. Tapioca-CMS possessed more amorphous (86.3%-amorphous) and viscous (310.58 cP) profile than sago-CMS. Carboxymethyl functional group (1620-1607 cm-1) and crystallographic-peak (2θ=20o) were spotted as well within all CMC samples. CMC NaOH-25% possessed the highest yield (118.52 g/g). More alkali added led to more intense CMC granules degradation. CMC NaOH-25% acquired the most amorphous (59.5%-amorphous) and viscous (63.08 cP) profile. Crosslinked-PVA functional group within materials’ bond (3431-3436 cm-1 and 1384-1413 cm-1) was evidenced within all five hydrogel samples (tapioca CMS-PVA (9:1), sago CMS-PVA (9:1), tapioca CMS-CMC NaOH 25%-PVA (2:2:1), sago CMS-CMC NaOH 25%-PVA (2:2:1), tapioca CMS-CMC NaOH 25%-PVA (8:1:1) hydrogel). CMC addition successfully improved PVA-hydrogel crosslinks structures throughout CMS-PVA hydrogel networks, however excess CMS disrupted PVA crystallites after its miscibility. Sago CMS-PVA hydrogel (9:1) denoted the highest swelling capability, while tapioca CMS-CMC NaOH 25%-PVA hydrogel (8:1:1) presented the highest water absorption capacity. Otherwise, the best oil absorption capability was indicated by sago CMS-CMC NaOH 25%-PVA hydrogel (2:2:1).