Sustained And Controlled Release Fertilizers Coated With The Organic / Inorganic Composite Membranes

The urea-formaldehyde prepolymer (UF) was modified using acrylic emulsion (A) and nano-graphite (G). We prepared urea-formaldehyde/acrylic emulsion binary material and urea-formaldehyde/acrylic latex/nano-graphite trinary organic/inorganic composite materials. FTIR, SEM, TGA, DTA, shear strength, shear viscosity, resistance to boiling water of the materials were tested. The binary membrane of urea-formaldehyde/acrylic emulsion and the ternary membrane of urea-formaldehyde/acrylic latex/nano-graphite with different components and different thickness were prepared and their fertilizer-permeation performance were studied.UF resin is an envelope material with the advantages of low cost and high nitrogen contents. Acrylic emulsion exhibits a good coating property, nano-graphite has advantages of nanoparticles, so we used respective advantages to preparare sustained-release membranes. The SEM observation shows that the dispersion of nano-graphite is good in urea-formaldehyde/acrylic latex/nano-graphite composite materials. The other results show that with more pure acrylic emulsion added, the viscosity of urea formaldehyde/acrylic becomes greater, the shear strength decreases and the resistance to boiling water increases lightly. Compared with the binary membrane of urea-formaldehyde/acrylic emulsion, the shear viscosity and shear strength of the ternary membrane of urea-formaldehyde/acrylic latex/nano-graphite with the same amount of acrylic emulsion increase, meanwhile the resistance to boiling water greatly increases. Added acrylic emulsion and nano-graphite has small influences on the thermal stability of UF, but make the residual weight ratio reduce.In the paper, our study shows that the amount of urea through the membrane reduces with the increase of the membrane's thickness. For the binary urea-formaldehyde/acrylic system with the same thickness, the more the content of acrylic emulsion, the smaller the amount of urea through the membranes. With the same thickness and the same content of acrylic emulsion, added nano-graphite could reduce the fertilizer permeability of the membranes. We also find that when the content of nano-graphite is 0.8%, the urea permeability of the ternary membrane is smallest.