Study On Dispersion Technology Of Pigment And Its Interaction Based On OSA Starch And Arabic Gum Compound System

Iron oxide yellow,also known as iron yellow,is a hydrated form of iron oxide.It has fine particles and excellent properties such as covering power,coloring power,light resistance,alkali resistance,acid resistance,etc.It is widely used as a pigment and coloring agent in various glass ceramics,concrete,cosmetics,building materials,plastics,and rubber products.The particle size of the color powder itself has a large specific surface area and surface energy,as well as hydrogen bonds and intermolecular attraction in its molecular structure,making it easy to agglomerate.In recent years,the coating technology has been widely used to improve its dispersibility and stability.Octenyl succinic anhydride（OSA）can be esterified with starch to produce octenyl succinic acid starch（OSA starch）,which is amphiphilic and can be used as an emulsifier and encapsulant.Arabic gum（AG）is one of the first hydrophilic colloids approved by the U.S.Food and Drug Administration（FDA）for use in food.It is a carbohydrate polymer with excellent emulsifying,stabilizing,and thickening properties and is commonly used as an emulsion stabilizer in medicine,cosmetics,and food.In this study,OSA starch and AG were used as composite wall materials to encapsulate iron oxide yellow powder to improve its dispersibility and stability in water-based solutions.Considering the dispersibility and stability of high-content color powder in cosmetics,the encapsulation of iron oxide yellow with OSA starch and AG is an efficient and non-toxic method for preparing stable color powders.It is of great significance for the development and application of natural polysaccharides in the cosmetics industry.The main conclusions are as follows:Through investigating the compounding process of OSA starch and Arabic gum composite wall material embedding,optimization experiments were conducted on the suspension stabilizer for colorant.The three main factors of composite wall material concentration,composite wall material ratio（OSA starch:AG）,and core-to-wall ratio were determined.Viscosity and centrifugal stability（absorbance）were used as evaluation indicators,and single-factor and response surface optimization experiments were conducted to determine the optimal process parameters.The optimal process parameters were found to be:composite wall material concentration of 4%,OSA starch to AG ratio of 4:1,and iron oxide yellow to composite wall material ratio of 3:2.Iron oxide yellow loses about 14%of weight due to dehydration within 500℃.OSA starch loses weight due to dehydration within the temperature range of 25-100℃,and rapid weight loss occurs in the temperature range of 200-310℃due to the degradation of hydroxyl structure of high-temperature OSA starch.AG loses slight weight due to moisture loss within the temperature range of 25-200℃,and its stability deteriorates and loses about 48%of weight rapidly at temperatures between 240-330℃.The mass loss of the inclusion compound OAF（OSA starch-Arabic Gum-Fe₂O₃·H₂O）is mainly divided into two stages:one is the mass loss caused by water evaporation at temperatures below 200℃,and the other is the significant weight loss at temperatures above 200℃,with almost no weight loss after 400℃.OAF starts to melt at 3℃due to the degradation of the composite wall material layer and reaches the glass transition temperature at 65℃.The thermogram of OAF shows a wide range of melting transition temperatures,indicating good thermal stability after encapsulation of iron oxide yellow.Diffraction peaks of iron oxide yellow pigment appear at 17.7°,21.1°,34.6°,35.3°,36.7°,53.1°,and 59.3°,and the intensity of diffraction peaks of OAF and iron oxide yellow are slightly different but similar in shape.Transmission electron microscopy（TEM）and scanning electron microscopy（SEM）observations show that both iron oxide yellow particles and OAF are elongated in shape with different sizes,and the thickness of the encapsulation layer is about20 nm.The apparent viscosity of OAF solution increases with the increase of OAF concentration,and the viscosity value reaches 43 m Pa·s at a concentration of 40%,but the color slurry still maintains good flowability.The absolute value of Zeta potential of OAF increases with the increase of pH,indicating stronger stability,and the stability is relatively better at pH>8.The increase of OAF concentration reduces the contact angle and surface tension,indicating better wetting and spreading ability of OAF solution,and all contact angles are less than 90°,indicating good wettability and hydrophilicity of OAF solution,which is easy to adhere to the skin.Accelerated stability tests of wet-mixed OAF color slurry were conducted using LUMi Sizer,and it was found that the instability index decreased and the system stability increased with the increase of OAF concentration.The elastic modulus（G′）and viscous modulus（G″）of OF（OSA starch-Fe₂O₃·H₂O）,AF（Arabic Gum-Fe₂O₃·H₂O）,and OAF increase with the increase of angular frequency（ω）,and G″is always higher than G′,indicating that the system is predominantly viscous in nature.The tanδvalues of these mixed systems are all greater than 1,and the tanδvalues decrease with the increase of angular frequency（ω）,indicating a weakening of gel strength and an increase in elastic proportion.The shear stress and apparent viscosity of these three systems decrease with increasing shear rate,exhibiting typical pseudoplastic behavior.