| Starch as a nature adhesive was widely used in papermaking industry. But its viscosity isvery high and the flowability, plastic property, stability are bad. Polylactic acid(PLA) has goodmechanical properties and physical properties, suitable for blow molding, thermoforming andother processing methods. Blending the starch with polylactic acid can improve the plasticproperty and the film-forming property, also the blends can fully biodegradable. Polylactic acidand starch are thermodynamically incompatible and the breaking strength is very low, that impactthe properties of the blends. This paper used Maleic anhydride(MA) as the compatibilizer grafton polylactic acid and blend with starch to improve the compatibility of the polylactic acid andstarch. Then study on the effects of PLA-Starch as adhesive of coating colors on the rheology ofthe coating colors and properties of the coating paper. The main research contents and resultswere as follow:(1) Maleic anhydride (MA) is often used as a compatibilizer in two immiscible polymerblends. MA is highly reactive with PLA free radicals induced by an initiator, and the anhydridegroup also can react with hydroxyls from starch to form ester linkages. This paper used2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexane as initiator makes the MA grafted onto the PLAand then blending the modified PLA with starch. The grafting degree was investigated underdifferent factors include temperature, reacting time and the mass of initiator. The result showedthat the proper grafting condition is at95℃for3h in the presence of1%initiator. Thecompatibility of a MA grafted PLA with starch composite(PLA-g-Starch) was compared with aPLA with starch composite(PLA-Starch) through Differential Scanning Calorimeter（DSC）、Water absorption and SEM. The result showed that the PLA-g-Starch has the lower GlassTransition temperature and lower Water absorption compared with the PLA-Starch. That provedthe compatibility was improved. The SEM also showed that the compatibility was improvedobviously.(2)Study on the effect of PLA-g-Starch on the rheology of the coating colors and theproperties of coating paper. It was showed that the low shear viscosity and the high shearviscosity of the coating color decrease with the grafted polylactic amount increasing. Thewhiteness, glossiness, surface strength and the K&N of coated paper increase with the graftedpolylactic amount increasing.(3)Study on the different effects of PLA-g-Starch and PLA-Starch on the rheology of thecoating colors and the properties of coating paper. It was showed that, when the dosage of PLAwas same, the PLA-g-Starch got the lower viscosity of coating, higher whiteness，glossiness,surface strength and lower K&N than PLA-Starch.(4)Comparing the PLA-g-Starch and PLA-Starch made by chemical method with thePLA-Starch made by Physical extrusion method. It was found that the PLA-Starch made byextrusion as the adhesive could get lower coating viscosity, higher whiteness and glossiness than the PLA-g-Starch and PLA-Starch. But the surface strength and the K&N was lower thanPLA-g-Starch and PLA-Starch.(5) Study on the different effects of the PLA-Starch and the styrene-butadiene latex on therheology of the coating colors and the properties of coating paper. It was found that, by thedifferent method of the PLA-Starch modification or change the dosage of PLA could get betterproperties of coating colors and coating paper than the styrene-butadiene latex. |
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