Preparation And Propetries Of Starch Composite Films By Extrusion Casting

With enhancing of environmental awareness, people do not satisfied with the conditionthat traditional plastic packaging films are used in food packaging. To solve the contradiction,lots of research institutions have paid attentions on biodegradable packaging films which aremade by starch that can be biodegraded. However, the starch films made by traditionalprocess are not so good at mechanical performance and water resistance which is the mainlimitation in industrial production. Besides, the weak properties, the high energy costs andlow produce efficiency of solution casting film can not meet the requirements of industrialmanufacture. In this paper, starch films made by extrusion casting were improved theproperties by adding reinforcing agent and surface chemical cross-linking reaction. The mainresults are as follows:1. In the base recipe, the optimal technological parameters were: prilling temperaturewas130℃, prilling rotation speed was30rpm, and extrusion parameter was135℃withrotation speed at24rpm. The verified test showed that the tensile strength of the film underthis condition was1.72MPa and elongation at break was35.94%.2. SEM and FRIT were used in the study of the film morphology and structure. From thetest, a result could be got that CMC had a good consistence with starch which meant theaddition of CMC improved the tensile strength and the water vapor permeability of the starchfilm significantly. The tensile strength increased when CMC content increased under the8%and when it beyond10%the tensile strength began to decrease. Comprehensive eachproperties of the film, the appropriate content of CMC should be under8%.3. Sodium alginate also had a good consistence with starch. The addition of sodiumalginate augmented the film’s tensile strength and oil resistance. However, a decrease ofelongation at break and water resistance appeared while adding sodium alginate. When thecontent was2.5%, the film’s tensile strength increased by112.79%,WVP decreased by41.47%and PO decreased by47.39%。4. The addition of OMMT improved the mechanical property as well as tensile strengthand elongation at break. But OMMT was negative to the film’s water resistance and water solubility. Films which had different OMMTs had different properties, the suitable contentwas among5%to7%.5. The water vapor permeability and elongation at break of starch films were declinedand tensile strength increased after surface crosslinking modified by glyoxal. A highertemperature gave rise to a faster reaction rate, but the influence of reaction temperature onfinal crosslinking degree was not so remarkable. The crosslinking degree of the surface layerincreased with prolongation of crosslinking reaction time. The higher the crosslinking degreewas, the lower WVP of the films. And the maximum decline was44.13%.The influence ofsoaking time and reaction temperature was significant. Longer soaking time and higherreaction temperature gave rise to higher value of tensile strength while the growth was up to122.47%, and lower value of elongation at break.