Study Of Irradiation Modification Effects On The Extrusion Of Biodegradable Starch Material From Maize

In this paper, a kind of biodegradable material was made of corn starch, itsrelevant processes and parameters were also studied systematically. Physical-chemicalproperties of starch can be changed by60Co-γ-ray. Taking the corn starch as rawmaterial, the radiation dosage is adopted10,20,30,40,50kGy, respectively. Suchindex was determined as starch content, colorimetric characteristics and viscosityproperty and so on. Results show that the properties of corn starch effectively changedby irradiation, with irradiation intensity increased, starch brightness is reduced,yellowness is raised, pasting temperature is reduced and viscosity is reduced.The best pressing conditions of preparing the starch biodegradable material wereas follows: pressing temperature of120℃, hot pressure of12MPa, pressing time of12min. Using five-factor orthogonal rotation experiment, the modified conditions ofstarch biodegradable material were optimized. The optimum conditions were asfollows: the irradiation dose of30kGy, extrusion temperature of158℃, extrusionfrequency of22Hz, the addition of glycerol of24.8%, the added amount of water of6.1%. Under these conditions, the properties of the obtained starch biodegradablematerial were as follows: elongation of174.48%, tensile strength of5.47MPa, waterabsorption of51.65%and luminousness of53.57%. The degradation results showed:when the starch biodegradable material was buried in49days, in the natural soilenvironment, the rate of weight loss was62%, when the starch biodegradablematerial was buried in77days, in the aqueous soil solution environment; the rate ofweight loss was63%.The changes of material structure, composition and characteristics were studiedwith integrated thermal analysis instrument, X-ray diffraction, SEM et al before andafter the formation of protein materials.In thermodynamic performance test, the results showed that: the glass transitiontemperature of starch materials and irradiation modified starch biodegradable materials were52.67℃and47.77℃respectively. In the irradiation modified starchbiodegradable materials, the thermal weight loss process could be divided into threeprocesses: water volatilized when the temperature was98.42℃or so; glycerolvolatilized when the temperature was98.42-257.19℃; the degradation of starchmolecules was happened when the temperature followed by257.19℃.The results of SEM analysis showed that: the shape of Starch material molecularstructure was irregular shape, globular structures of starch completely destroyed. Thespace between the irradiation modified starch materials was smaller than the starchmaterial, and the volume of molecular was greater than the starch material; the surfaceof irradiation modified starch material was smoother than the starch material.The results of X-ray diffraction analysis showed that: the crystallinity of starchwas28.72%, the crystallinity of irradiation modified starch was21.53%, thecrystallinity of starch biodegradable material was14.69%, and the crystallinity ofirradiation modified starch biodegradable material was10.41%. The materials showlower crystallinity materials after irradiation, it can improve the material processingperformance.