Design And Study Of The Slow-Release Urea Fertilizer Based On Inclusion Complex

Development of environmental-friendly and easily-processed slow-release fertilizers is one of the research hotspots in the fields of agriculture and chemical industry,and also an emerging application for environmental-friendly polymers,nowadays.In this study,a new idea of using polymer/urea inclusion complex compound as slow-release fertilizer was proposed and realized.The biodegradable polyester/urea inclusion complex granules were directly prepared via a one-step approach,and its urea slow-release behavior and structure evolution process were systematically studied.The urea slowrelease mechanism of the inclusion complex fertilizer was well presented.The relationship between the crystallization ability of the polymer chain and the slow-release performance of the inclusion compound was revealed,and the plant growth promoting effect of such slow-release fertilizer was evaluated in detail.The main research contents and conclusions are listed as follows:(1)The slow-release behavior and its influencing factors of degradable polyester/urea inclusion complexes have been studied.Inclusion complexes were prepared by respectively using poly(butylene succinate)(PBS),poly(ethylene succinate)(PES)and poly(propylene succinate)(PPS)as the guest and urea the host frameworks.Slow-release experiment showed that the inclusion complex displays great slow-release performance of urea component.Processing approach,granule size and the type of guest molecule,polyester can be easily used to slow down the dissolution rate by tens to thousands of times when compared with pure urea granules.What is more,the relationship between the crystallization ability of the polyester and the slow-release performance of inclusion complex fertilizer was well clarified,that is,the slower the crystallization the longer the release time.(2)The slow-release mechanism of inclusion complex fertilizer has been presented.Different methods including DSC,POM,SEM were employed to in detail study the release process of urea from inclusion complexes,and the slow-release mechanism was clarified.When the inclusion complex granules are contacted to water,urea framework on the surface of granules is destroyed and dissolved in water,correspondingly,some polyester chains escape,coalesce and crystalize to form highly porous shell structure hindering the further rapid release of urea component inside granule.the porous polyester shell layer also contains small inclusion complex particles,which would exhibit as polymer coated fertilizer and help prolong the slow-release time.(3)The slow-release performance of inclusion complex fertilizer has been finely adjusted based on copolymerization design.Poly(butylene succinate-co-butyl adipate)s(PBSA)were synthesized with different feeding monomers.The crystallization ability of PBSA was gradually weakened with respect to the randomly incorporating adipic acidic units in the main chain.A series of PBSA/urea inclusion complexes were prepared,and their slow-release properties of urea were measured.The intermittent leaching experiment showed that increasing adipic acidic units can gradually prolong the slow-release time from 24 days to 30 days.(4)Promoting effect on plant growth for the inclusion complex fertilizer has been evaluated.The results of pot trial showed that the inclusion complex fertilizer better promote the growth of corn and rape than neat urea.The slowdown of releasing urea nutrient from inclusion complex benefits the utilization rate,thus better promote the plant growth than neat urea and obtain the higher growth indexes.