Preparation and performance of polyurethane/mesoporous silica composites for coated urea

Polymer/mesoporous silica composites have drawn much attention. In this study SBA-15 mesoporous silicas with three morphologies including fiber, nano-rod and sphere were synthesized and characterized. Polyurethane (PU)/SBA-15 composites were prepared via an in-situ reactive-layer spray technique on urea granules. And the effects of SBA-15 on structure and controlled release performance of coating were elucidated and compared to n -SiO 2 . The results showed that rod-like SBA-15 with an average particle size of 700   nm extremely improved the release properties of PU at the same filler loading, but the other two SBA-15 fillers had no effect on PU instead. SEM images reflected that although SBA-15 particles were all well-dispersed in PU matrix to form a sea-island structure, PU/fiber-like SBA-15 composite coating had some obvious defects. Conversely, n -SiO 2 particles of coating gathered and formed large agglomerates without voids. TGA studies suggested that PU/rod-like SBA-15 composite as a coating material had a much higher thermal stability than PU and PU/ n -SiO 2 .