The Effects of Molecular Weight of Poly Lactic Acid Matrix on Release Time of Smart Urea Fertilizer (SUF)

摘要

Plants could not much absorb the Urea in the commercial granular fertilizers. Urea is a hygroscopic chemical which is easily lost to the environment due to exposure, erosion, surface flow or washed by water. This condition caused a higher dose of urea use that plant needs. It was interesting to develop controlled released fertilizer. We prepared polylactic acid (PLA) as a matrix that carries urea fertilizer. PLA matrix is degraded to be non-toxic chemicals, followed by releasing of urea. This research aims to study the correlation of molecular weight of PLA and release time of urea in water. The molecular weight of PLA was varied by differentiating its polycondensation time, i.e. 24, 36 and 48 hrs. The condition during polycondensation was controlled at 138°C and added SnCl_2.2H_2O (0.01 % wt) as a catalyst. The obtained PLA in molten phase was blended with different weight of urea powder, i.e. 0.1 g, 0.3 g and 0.5 g/3 g of PLA. These blends were then called Smart Urea Fertilizer (SUF). This fertilizer was studied its degradability in water and soil for a certain time. The presence of urea in the PLA matrix was monitored using Fourier Transform InfraRed (FTIR) qualitatively. The morphology of SUF before and after degradability test was investigated using Scanning Electron Microscopy (SEM). These results were then compared and analyzed with the weight loss data. The data show that the degradation of PLA matrix is followed by releasing of urea in SUF.