Study On The Preparation Of Slow And Controlled Release Fertilizer From Carbon Dioxide Copolymer

Slow release fertilizer is a new type of fertilizer that uses a special process to coat a surface of a common fertilizer with a semi-permeable or impervious material to slow down and control the release of fertilizer nutrients.Because it has the advantage of releasing nutrients according to the fertilizer requirement of crop growth,it has become a research hotspot in the field of fertilizer.At this stage,the research of coating materials is the key point in the research of slow release fertilizer,especially the polymer slow release fertilizer with good nutrient-controlled release effect,which has the most application prospect.Therefore,in this paper,a biodegradable aliphatic polycarbonate material is formed by copolymerization of CO₂ and an epoxy compound,and a slow release fertilizer is prepared therefrom.In this paper,propylene oxide and cyclohexene oxide were selected as the monomers for copolymerization with CO₂,and the properties of the synthesized high molecular polymers were tested and analyzed.Then,the polymer material was used as the coating material to prepare the slow release fertilizer of polycarbonate,and the sustained release property of the prepared fertilizer was studied.The models and methods for the nutrient release behavior of polycarbonate controlled release fertilizers were inferred by slow release kinetics.It not only realizes the efficient use of CO₂ resources,but also opens up an application field of aliphatic polycarbonate,which meets the requirements of low energy consumption and resource renewability,and reflects the concept of green chemistry and sustainable development.The main contents are as follows:?1?An aliphatic carbonate product?poly?cyclohexene carbonate?and poly?propylene carbonate-cyclohexyl carbonate??is prepared by copolymerizing two epoxy compounds?hexylene oxide and propylene oxide?and CO₂.A series of poly?cyclohexene carbonate?and poly?propylene carbonate-cyclohexyl carbonate?with different molecular weights were prepared by controlling the reaction conditions,and their structures were analyzed by FT-IR,NMRand GPC.When the CO₂ pressure is 4MPa,the reaction temperature is70°C,and the reaction time is 12h,the molecular weight of the obtained poly?cyclohexene carbonate?is the largest.When the CO₂ pressure is 4MPa,the reaction temperature is 70°C,and the reaction time is 6h,the obtained poly?propylene carbonate-cyclohexyl carbonate?has the largest molecular weight.?2?A series of slow release fertilizers were prepared by using urea particles as the core and different molecular weight poly?cyclohexene carbonate?and poly?propylene carbonate-cyclohexyl carbonate?as outer coating materials.The preparation process is optimized.The optimum preparation condition of the poly?cyclohexene carbonate?slow release fertilizer is:the solvent amount is 10%,the plasticizer dosage is 2%,and the coating amount is 10%.The optimum preparation condition of poly?propylene carbonate-cyclohexyl carbonate?slow release fertilizer is:the solvent amount is 10%,the plasticizer dosage is 3%,and the coating amount is 10%.?3?The sustained release properties of the above two slow release fertilizers were analyzed by p-dimethylaminobenzaldehyde spectrophotometer.The SEM of the surface morphology of the coatings showed that the higher the molecular weight of the coating materials,the slower the preparation.The smoother and denser the membrane surface of the controlled release fertilizer,the better the sustained release performance.?4?The degradation properties of poly?cyclohexene carbonate?and poly?propylene carbonate-cyclohexyl carbonate?were investigated by soil burial method.The results showed that the film gradually degraded with time.The pH of the solution was measured before and after soaking,and the pH was almost unchanged,indicating that the chemical components of poly?cyclohexene carbonate?and poly?propylene carbonate-cyclohexyl carbonate?were included in the package not affected during the membrane process.?5?Using Ritger-Peppas equation for poly?cyclohexene carbonate?and poly?propylene carbonate-cyclohexyl carbonate?slow-release fertilizers The sustained release performance was simulated,and both materials show that nutrient release is more in line with Fick's law of diffusion.