Study On Modified Corn Starch Adhesive

Starch is a non-toxic and environmental-friendly raw material which is cheap and easy to get. It is used in adhesive industry with low-cost,non-polluting advantages.However,there are drawbacks on original starch regardless of its physical or chemical properties.This study improve the initial viscosity of original starch,shorten its drying time, increase bond strength, while improving other properties.The process is adopting oxidation,gelatinization treatment to the original starch,and then complexing with PVA,casein and other materials.At last, the adhesive achieve industrial application standard.At first, the oxidation and the gelatinization process of the starch is discussed and studied.By analyzing and contrasting,potassium permanganate is selected as oxidant and sodium hydroxide is selected as gelatinization agent.The effect of starch concentration,oxidation temperature,gelatinization temperature to its viscosity is inspected and the best process parameters is got. The microstructure changes before and after oxidation and gelatinization is compared through infra-red spectra which is got before and after oxidation and gelatinization process.The results show that viscosity increased continuously with the increasing of starch concentration in the solubility range.The oxidation temperature is selected 55℃ndhegelatinization temperature 65℃.Oxidation temperature and starch concentration affect on the carboxyl content weakly; the carboxyl content has a small increase as the temperature rose and the concentration increased. In the infra-red spectra can be seen that little amount of hydroxyl is oxidized into carboxyl.Part of starch chain units change into straight-chain from ring after oxidation, and after gelatinization the hydrogen bonding has been damaged.After determining process parameters such as temperature and concentration, the effects of the amount of oxidants,gelatinization agent,as well as polymers on modified starch adhesive is studied.Orthogonal design test method is used to inspect the results which oxidant dosage,gelatinization dosage,PVA consumption,as well as the amount of casein affect on several key indicators of the adhesive.The reasons why the amount of each component influence the property is discussed.And the best ratio range of each component is obtained through comprehensive consideration.The orthogonal design study drew the following conclusions:1)Under the test-set condition, the impact of compounding polymers is most obvious to the apparent viscosity, while potassium permanganate is the weakest.In a certain range,viscosity decreases while the potassium permanganate and hydrochloric acid increase.While the amount of PVA and casein increase,the viscosity decrease.Doses of gelatinization agent increasing make it reduced after initial increasing.2) Under the test-set conditions, the amount of oxidants and gelatinization agent affect the drying time significantly, while PVA and casein is weak.Drying time ture up the most value with the amount of potassium permanganate,hydrochloric acid and sodium hydroxide which is in the scope of the experiment dosage.The PVA and casein are played to the role which reduce and improve the drying rate. 3) Under the conditions of the test set, the amount of gelatinization agent, oxidant and PVA affect the bond strength significantly, and other factors do less.The bond strength reduced while the dosage of potassium permanganate and hydrochloric acid increase.It increases while the dosage of the sodium hydroxide,PVA and casein increase.Excellent and modified starch adhesive is made based on the ratio got from orthogonal test while also need adding relative ingredient.The better dosage production formulations is as follows:starch 50g,potassium permanganate0.5g, sodium hydroxide 5g,polyvinyl alcohol 5g,casein 10g, boric acid,carbamide and alcohol is in its moderate.Such products have many advantages such as high initial viscosity ,better adhesive force,short drying time,non-toxic non-polluting to environment etc. There is a very broad application prospect in industrial production.