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Li Q.,Yanshan University | Wu S.,Yanshan University | Ru T.,Sino Arab Chemical Fertilizer Co. | Wang L.,Yanshan University | And 2 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2012

Polyurethane coated urea slow/controlled release fertilizer was prepared based on urea granules, isocyanate, polyols and paraffin. Isocyanate reacted with polyols to synthesize the polyurethane skin layer on urea granules surface. Paraffin serves as a lubricant during syntheses of polyurethane skin layers. The structure and nutrient release characteristics of the polyurethane skin layers were investigated by FTIR, SEM and TG. Urea nitrogen slow-release behavior of the polyurethane coated urea was tested. The experimental results indicated that compact and dense polyurethane skin layers with a thickness of 10-15 μm were formed on urea surface, the urea nitrogen slow-release time can reach 40-50 days. Paraffin proves to play a key role in inhibiting water to penetrate into urea, but excessive addition would decrease the polyurethane crosslinking density. ©Wuhan University of Technology and SpringerVerlag Berlin Heidelberg 2012. Source

Wu S.,Sino Arab Chemical Fertilizer Co. | Ru T.-J.,Sino Arab Chemical Fertilizer Co. | Wang J.-M.,Sino Arab Chemical Fertilizer Co.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2013

The nutrient release experiment of polyurethane coated urea (PCU) was carried out in pure water at 25°C. With the release of urea, the structural variation of polyurethane coating was investigated by Fourier transform infrared spectroscopy (FTIR), then a series of curves were collated and compared so as to better reflect the relation between diffusion rate of urea and coating structure. It was found that when the nutrient was released by 50% wt, new absorption peaks at 3435, 3342, 1671, 1621, 1448 and 1159 cm-1 appear in the FTIR spectra of polyurethane coating, moreover, the height of these absorption peaks was increased gradually when the nutrient was released by 70% wt, more importantly, these new absorption peaks are consistent with the characteristic absorption peaks of urea fertilizer, the spectra of urea were mainly characterized by bands at 3440, 3346, 1672, 1621 and 1461 cm-1. The results show that the IR spectra variation was caused by the content of urea, existing in the polyurethane coating, and was increased gradually, The more the urea content, the greater the swelling degree of the polyurethane coating. The swelling of polyurethane coating leads to the pores size change, and release rate is increased, so the "S" pattern curve of the nitrogen accumulative release is formed. Source

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