Composites of thermoplastic starch/natural rubber blends for fertilizer-releasing in agriculture

Thermoplastic starch (TPS) based on the mixture of cassava starch and glycerol was prepared and blended with the natural rubber (NR) and epoxidized NR (ENR). The resulting blend was further filled with fertilizer grade 16-16-16. The effects of fertilizer concentration on the properties of the blends and the growthability of maize seedling were investigated and characterized. In case of the specific properties of the blends, it was found that the blends based on NR and ENR matrices exhibited a reduction in tensile properties upon increasing the fertilizer concentration, while the solubility, water absorption and biodegrability were improved. In particular, the blends of TPS/ENR with fertilizer showed better properties than that of the blend with NR due to the physical interaction of hydrogen bonding among the polymer molecules as confirmed from ATR-FTIR. Although both the blends were found to be decomposed within a period of two weeks, the releasing efficiencies significantly affected the growth of maize seedlings. According to the growthability based on count and greenness of leaves, shoot and root biomasses and phytotoxicity of fertilizers, the TPS/ENR with 80 phr of fertilizer represented the suitable one for growing the seedlings with proper release ability of fertilizer, especially the N, P and K elements during planting. Relating the water swelling of 180 %, it was found that the approximately 90 % of N, 70 % of P and 95 % of K were released before the complete decomposition degradation. This newly controlled release fertilizer (CRF) system can be applied for several plants by knowing the fertilizer concentration and ease of shape designing.