Functional Modification Of Anchote Starch: Study On The Effect Of Gum Arabic, Polyvinylpyrrolidone, And Boric Acid On An Acetylated Starch Adhesive Performance

Abstract

Starch Is A Renewable, Biodegradable, And Relatively Inexpensive Natural Polymer That Originates From Different Plant Sources Which Attracted Much Attention In Applications Of Food, Papermaking, Additives, And Adhesives, Because Of Its Non-Toxicity, Renewability, Abundance, And Good Adhesion. It Is Widely Used As Adhesives, But The Bonding Capacity Of Starch-Based Adhesive Is Not Strong Enough To Glues Structural Products, Because, Its Bond Formation Is Dependent On Hydrogen Bonding Forces, Which Is The Weakest Bond Of The Chemical Bonds And ItA lso Reacts Easily With Water Molecules To Form Hydrogen Bonds, Leading To Poor Water Resistance. Therefore, It Is Found Essential To Modify Starch To Upgrade Its Adhesive Performance For Different Applications And To Replace Petroleum Derivative Adhesives Which Contain Carcinogenic, Hazardous, And Toxic Compounds Of Formaldehyde. In This Study, The Starch Of Anchote (Coccinia Abyssinica (Lam.) Cogn.) Was Extracted Using A Modified Procedure And Its Functional Modification Was Done By Acetalization Method. The Starch Acetates With Different Degrees Of Substitution (Ds) Were Prepared By Reacting Native Starch With Acetic Anhydride Using Aqueous Sodium Hydroxide (Naoh) As The Catalyst. The Degree Of Substation (Ds) Increased With Increasing Temperatures, Reaction Times, And Increasing Mixing Ratios Of Acetic Anhydride To Starch. Increasing The Amount Of Catalyst Naoh Up To 30% Increases Ds And Decreases In The Interval Of 30%-40% Due To Steric Hindrance. The Ft-Ir Analysis Confirmed That The Introduction Of The Acetyl Group In The Acetylated Starches Through A Band At 1739 Cm-1. X-Ray Diffraction (Xrd) Analysis Of Acetylated Starch Shown That The Crystal Structure Of Native Starch Was Scratched And A New Crystalline Structure Was Formed. The Scanning Electron Microscopy (Sem) Suggested The Starch Granules Start To Rupture And Different Sizes Of Cracks Are Formed On Their Surfaces When Acetalization Takes Place And Eroded Surface Appearances Are Observed To Make A Rough Surface Than Native Starch. Differential Scanning Calorimetry (Dsc) Confirms That Acetalization Decreases To, Tp, Tc, And?? Hgel Of Starches. The Thermal Analysis Of The Native And Starch Acetate Was Studied Using Thermogravimetric (Tga) Analysis And Differential Thermal Analysis (Dtg), It Was Found That The Thermal Stability Of Acetylated Starch Depends On The Degree Of Substitution (Ds).The Thermal Stability Of Acetylated Starch With Ds-3 Is Much Higher Than That Of The Native Starch. This All Characterization Confirmed The Occurrence Of Structural Modification On Native Starch Due To The Introduction Of The Acetyl Group On It And Its Adhesive Property Measured To Be 2.13 Mpa From Zero. However, Modification Of Native Starch Brought Significant Improvement, But, StillCan??T Full Filled The Minimum Criteria Of The Adhesive Which Was ??? 2.32 Mpa. To Meet The Minimum Requirements Of Adhesive, Ga And Pvp Are Incorporated As Adhesive Enhancers And Ba As A Crosslinker. The Modified Starch Adhesive Significantly Improved To 44.5 Mpa From2.13 Mpa By Incorporating 10% Ga, 10% Pvp, And 1.5% Ba. Its Lap Shear Strength Was Nearly Comparable With Commercially Available Polyvinyl Acetate (Pvac) Which Was 43.13 Mpa. Finally, The Occurrence Of Intermolecular Interactions Or Chemical Reactions Between Modified Starch, Ba, Ga, And Pvp Were Proved By Ftir And Tga/Dtg Analysis. Therefore, This Research Work Concludes That Modified Anchote Starch Can Be Used As A Potential Raw Material For The Formulation Of Adhesives For Structural Applications.