Thermal processing optimization to obtain composites for controlled release of fertilizer

Development of slowcontrolled release materials has expanded and demonstrated a potential to increase field productivity by delivering the nutrient in a spaced form and synchronized with the needs of the plant, as well decreasing nutrient losses1. Optimizing the processing is a demand. The aim of this work was to study the thermal processing (mixer chamber of Haake rheometer) of composites based on Poly(3-hydroxybutyrate) (PHB), sugarcane bagasse (BCA)2 and potassium nitrate (KNO3) as a controlled release material. The parameters fiber content (10, 20 and 30 wt.%) and KNO3 sorbed by BCA (BCAS) and non-sorbed (BCA) were evaluated and the temperature and rotation (165° C and 50 rpm) and KNO3 content (50 wt.%) were kept constant. For BCA10 (a), BCA20 and BCA30, the processing was finalized after the stable plateau torque, figure 1 (a). However, after processing, it was visible to the naked eye that the composites had heterogeneous points. To improve homogeneity, BCA10 (b) was processed in two steps, initially, the PHB was placed and, in 7 min, the mixture of BCA and KNO3 was added, finishing in 15 min. As the nutrient content in the composition is high, it was not possible, for all the nutrient be aggregated by the polymer. For the composites BCAS10, BCAS20 and BCAS30, the nutrient was first sorbed by the fiber and then processed under the same conditions as BCA10 (b). Evaluating all conditions, the composite with sorbed nutrients has better homogeneity.