Solution Blending of Blends of Modified Starch and EVOH
A predetermined amount of modified starch and EVOH were dissolved into dimethyl sulfoxide(DMSO) at a mildly elevated temperature (around 60 oC). A magnetic stirrer was used to facilitate the dissolution. A transparent and yellowish solution was obtained after total dissolution of polymers. The solution was put into a hood, allowing the evaporation of the solvent. Then the mixture was put into a vacuum oven at 100 oC until no weight changes were detected.
Solution Blending of Nanocomposites based on Modified Starch
A predetermined amount of modified starch was dissolved in tetrahydrofuran (THF) upon heating. 5 wt % of organoclay (or MMT) was pre-dispersed in THF (a co-solvent THF/water, 10/1 v/v was used to disperse MMT) by ultrasonic bath for 30 min, and then it was added slowly, while stirring, into the polymer solution. The mixture of modified starch and organoclay was stirred constantly for 2 days at an ambient temperature, allowing the evaporation of the solvent. Then the mixture were put into a vacuum oven at 100 oC until no weight changes were detected.
Melt Blending of Blends and Nanocomposites
Melt blending was performed by a twin-screw mini compounder (Haake Instruments). 5.5 g of polymer mixture, including a modified starch, EVOH, and 5 wt % of nanoclay, were fed to the compounder, which had been preheated to 185 oC. The compounder was run in a closed-loop mode, and the melt blending was performed by the twin-screw extruding in the compounder before discharge into a circular die. An external nitrogen supply prevented possible oxidation. For other characterization purposes, the nanocomposites were hot-compression molded when needed.