Modified Bio-based Polymer Composites From Biomass As Coating Material For Controlled-Release Urea Fertilizers And Its Controlled Release Characteristic Research

A novel polymer-coated nitrogen(N) fertilizer was developed by using bio-based polyurethane(PU) derived from liquefied locust sawdust(LLS) and corn crob(LCS)as coating material. The bio-based PU was successfully coated on the surface of urea(U)fertilizer prills to form polymer coated urea(PCU) fertilizer for controlled N release. Epoxy resin(EP) was also used to further modify the LLS bio-based PU to synthesis interpenetrating network(IPN)enhancing the slow-release properties of the PCU; and, organosilicone was modified the LCB bio-based PU to improve hydrophobicity properties of the CRU. The N release characteristics of the EP-modified PCU(EMPCU) and OS-modified CRU(SCRU) in water were determine at 25 ? and compared to that of PCU, EP-coated urea(ECU) and CRU, respectively. SEM was used to show the characterization of the surface and cross section structure of coated fertilizer, determination of the water absorption properties of various materials and the preparation of a new type of fertilizer applied to potted maize experiment, to explore the fertilizer utilization ratio. The main research results were as follows:1. The N release characteristics of various kinds of coated fertilizer in water were determine at 25 ?. The results showed that the EP modification reduced the N release rate and increased the longevity of the fertilizer coated with bio-based PU, and the liquefaction of epoxy resin modified sawdust controlled release performance of coated fertilizer significantly better than unmodified sawdust coated fertilizer, release longevity of EMPCU increase much compared with PCU, and the epoxy resin content in 30% of the time controlled release performance is the best, is better than that of EP coated urea fertilizer.2. SEM was used to detect the surface and cross section characteristics of the various kinds of fertilizer. The results showed that the surface of the coating shell of PCU was very coarse with layered superposition phenomenon. Many pin holes and irregular structure were observed in the cross-section micrographs of the PCU shell. These pin holes and irregular structure might be easily permeated by water, causing quick release of nutrient from the coated fertilizer. The surface and the cross-section of the coating shell of ECU appeared much more smooth, compact, and uniform than that of the PCU. When EP and curing agent were added into the bio-based PU coating material, the surface of the coating shell of EMPCUs was also much smoother than that of PCU. Furthermore, the cross-section of coating shells of EMPCUs was much more compact than that of PCU, suggesting that EP was an effective amendment for the bio-based PU for fertilizer coating. When different amount of EP was used in the coating, the EMPCU shells also exhibited different surface and cross-section structure. In all the coating shells of the EMPCUs, the one with 30% of EP showed much smoother and more compact surface and cross-section than the others.3. The absorption rate of five kinds of materials were explored in the test, the results showed that the only EP material absorb least water, 30% of epoxy resin added amount of the absorbent of bio-PU material is slightly higher than that of EP material, the other is in turn 50% adding amount of EP modified bio-PU material and 20% adding amount of EP modified bio-PU material, and the bio-PU material most easily absorb water.4. Organicsilicon was used to modify liquefied corn cobs for coated fertilizer. Organic silicone modified liquefied corn cobs coated fertilizers greatly increased the controlled release time compared with the unmodified liquefied corn cobs coated fertilizer, suggesting that organic silicon as modified material was applied to the coated controlled release fertilizer in high feasibility. This experiment adopts two methods namely the kjeldahl nitrogen determination method and refractive index method to test the controlled release curves, CRU and SCRU get the release of curve fitted very good, explain complex refractive index method can replace the kjeldahl determination.5. A corn growth study was conducted to further evaluate the filed application of the EMPCU. The final result showed that a new type of fertilizer was developed. In comparison to commercial PCU and conventional urea fertilizer, EMPCU was more effective and increased the yield 39.76% of the corn and N use efficiency 77.14%. New type of EP modified bio-PU coated fertilizer is cheaper and environment friendly.