%0 Journal Article
%T Effect of Acetylation on Stability to Retrogradation of Starch Extracted from Wild Polynesian Arrowroot (Tacca leontopetaloides (L.) Kuntze) for Utilization as Adhesive on Paper
%A Hamza Abba
%A Abdulqadir Ibrahim
%A Gideon A. Shallangwa
%A Sani Uba
%A Yakubu A. Dallatu
%J Journal of Polymers
%D 2014
%R 10.1155/2014/732174
%X Starch was isolated from T. leontopetaloides tubers, chemically modified by acetylation with varying amounts of acetic anhydride. Monolayer of the ten acetylated and control starch powders was exposed on roof top for five weeks and pastes of both exposed and unexposed (control) samples were prepared with distilled water (1ˋ:ˋ3 w/w). The effects of acetylation, degree of substitution (DS), and exposure to sunlight were investigated to evaluate the retrogradation tendency of the adhesive pastes from changes in syneresis, tack strength, optical clarity, viscosity, gelation time, and drying time. The results obtained showed that all the adhesive properties studied were affected by both DS and exposure to sunlight. While tack strength, viscosity, and drying time were found to increase with increase in DS, syneresis, optical clarity, and gelation time were found to decrease with increase in DS. Increase in tack strength and reduction in syneresis imply that the acetylation treatment has made T. leontopetaloides starch more suitable for use in remoistenable adhesive applications. The reduction in syneresis, optical clarity, and gelation time with increase in DS was attributed to the strengthening of the bonds between the amylose and amylopectin molecules, preventing water leaching out of the starch granules. 1. Introduction Adhesive is a natural or synthetic substance that, when applied to surfaces of materials, binds them and the joint resist separation. Natural bioadhesives are obtained from vegetable matter, starch, plant exudates, and resins or from animals, for example, casein [1每5]. Advantages of adhesives over other binding techniques include ability to bind different materials together, efficient distribution of stress across the bonded joint, cost effectiveness, easy process mechanization, improvement in aesthetics design, and design flexibility [6每9]. Starch, , is a complex carbohydrate occurring in the form of minute granules in seeds, fruits, tubers, roots, and stem pith of plants, consisting of two polymers, amylose and amylopectin, and the molar ratio of which is about 20每30% and 80每70%, respectively [10每13]. Amylose is a linear polysaccharide composed of mostly linear chains with 500每20,000 汐- -D-glucose units, as can be seen in Figure 1 [14, 15]. Figure 1: Amylose molecule (adapted from Ward et al. [ 19]). Depending on the botanic source, amylose can form an extended shape (hydrodynamic radius 7每22ˋnm) but generally tends to wind up into a rather stiff left-handed single helix or form even stiffer parallel left-handed double helical junction
%U http://www.hindawi.com/journals/jpol/2014/732174/