Degradation behavior of residual films of controlled release fertilizers with nano-TiO₂ LDPE composites

Nano-TiO₂ and low density polyethylene (LDPE) were combined to form coating fluids, and nano-TiO₂-LDPE composite-coated controlled release fertilizers were prepared in a spouted fluidized bed coating equipment. Based on the research of their release characteristics via water immersion method, the mass loss rates were measured after different irradiation time by artificial accelerated ageing test. The effects of nano-TiO₂ on photo-degradation behavior of residual films were systematically studied by using FT-IR spectroscopy, DSC and viscosimetry. And changes in molecular mass, carbonyl index and others during degradation were discussed. It is found that under the function of photo-catalyst, the urea release rate of controlled release fertilizer has a certain degree of delay, the release period becomes longer and the degradation of residual film is remarkably promoted by hydrophobic nano-TiO₂. Furthermore, residual film shows the best degradation property when the mass fraction of hydrophobic nano-TiO₂ is 1%. With the increasing of degree of residual film degradation, the carbonyl index and crystallinity of LDPE in residual film increase, and the viscosity-average molecular mass decreases.