Preparation of Cassava Starch/Poly(vinyl alcohol)/Montmorillonite Nanocomposites for Coating Controlled-Release Fertilizer

Abstract

The aim of this research is to prepare polymer nanocomposites of cassava starch, poly(vinyl alcohol) (PVOH) and montmorillonite (MMT) by solution method for coating controlled release fertilizer. The polymer nanocomposites were prepared by mixing cassava
starch and PVOH at dry weight ratios of 70/30, 80/20 and each of these with various amounts of MMT (2 4 6 8 and 10 parts by weight per hundred of cassava starch and PVOH) The obtained homogeneous solution was casted into sheets using plastic mold and dried at 60 ^oC in a hot air oven. The obtained polymer nanocomposites sheets have been characterized for those; water absorption, moisture permeability, ammonium ion permeability biodegradability and their structure. The water absorption moisture permeability and ammonium ion permeability of polymer nanocomposites were enhanced with increasing amount of PVOH. However, these properties were decreased by the addition of MMT. After soil burial for 50 days, percent weight loss and biodegradability of the polymer nanocomposites enhanced as the amount of starch were increased. The X-ray diffractograms and transmission electron micrographs showed that the polymer nanocomposites formed were exfoliated. In this work the encapsulation of the commercial granular fertilizers, NPK 16-16-16 and NPK 18-46-0 were prepared by dip coating technique with 80/20/8 starch:PVOH:MMT nanocomposites. The coated fertilizer was put into the deionized water and, at a specified period, water solution was analyzed for amount of nitrogen. The results showed that the amount of nitrogen released rate of the coated fertilizer
was less than the uncoated one.