Preparation And Properties Of Composite Degradable Superabsorbent Resin With Slow-release Property

At present,the main way of using fertilizers in agriculture is direct irrigation.This way is not scientific and unreasonable,which can easily lead to a large amount of loss of fertilizers,not only cause low fertilizer utilization,but also cause pollution to the environment.By combining fertilizer with superabsorbent resin,slow-release fertilizer can not only slow down fertilizer time and improve fertilizer utilization rate,but also prevent fertilizer loss and pollution of the environment.Superabsorbent resin?SAR?is a new kind of functional polymer material with three-dimensional network structure.There are a lot of hydrophilic groups such as carboxyl and hydroxyl groups in its molecular chain,which can absorb a large amount of liquid.Because of its good water absorption and retention properties,SAR is widely used in drug carriers,sewage purification,food processing,sanitary products,agriculture and forestry and other fields.At present,most of the traditional SARs are polyacrylic acid and polyacrylonitrile,which have many problems,such as high production cost,poor liquid absorption performance and non-degradation.These problems restrict the application of SAR,and cause serious pollution to the environment.Chitosan,cellulose and other natural polymers and their derivatives can be added to SAR,which can promote the degradation performance and reduce the toxicity of the resin.Sodium humate is an organic material,which is widely distributed in nature,and its molecular structure contains hydroxyl,quinone,carboxyl and other active groups.What's more,SH is an important soil nutrient,which can effectively promote plant growth.Polyvinyl alcohol?PVA?is a water-soluble polymer with good hydrophilicity and biodegradability.Four different substances?sodium humate,polyvinyl alcohol,chitosan and sodium carboxymethyl cellulose?were introduced to the SAR.This study wants to provide theoretical guidance for moisture-resisting and salt-tolerating capacity by comparing different structure of SAR.The degradable SAR has multiple functions,such as water absorption,water retention,degradability and slow release,which can effectively improve the utilization rate of water and fertilizer and reduce environmental pollution and crop damage.In this thesis,PAA/AMPS/CTS/SH SAR and PVA/CMC/P?AA-AM?SAR were prepared with acrylic acid?AA?,acrylamide?AM?,2-acrylamido-2-methylpropane sulfonic acid?AMPS?,which blended with SH?PVA?CTS and CMC.The main contents are as follows:?1?Preparation and properties of PAA/AMPS/CTS/SH SAR:the SAR was prepared by AA,AMPS,CTS,and SH through inverse suspension polymerization,using potassium persulfate?KPS?as initiator,and N,N-methylenebisacrylamide?MBA?as crosslinker.The structure of the product was characterized by via Fourier transform infrared absorption spectroscopy,optical microscope and Thermogravimetric analysis.The optimum preparation conditions were as follows:initiator dosage 1.2%,crosslinking agent dosage0.3%,oil-water ratio 3:1,temperature 75%.Under these conditions,the liquid reached1097g/g and 103g/g in deionized water and 0.9wt%NaCl solution,respectively.Compared with the SAR without SH,the moisture absorption of the resin in the air decreased 2.0%,and the salt resistance in three different salt solutions?NaCl,CaCl₂,FeCl₃?was better.The slow release test showed that the release rate was faster in the first 12 days.The degradation performance test showed that degradation rate of the super absorbent resin in soil could reach 31.9%after 100 days.?2?Preparation and properties of PVA/CMC/P?AA-AM?SAR:the IPN SAR was prepared by AA,AM,CMC,and PVA through inverse suspension polymerization,using potassium persulfate?KPS?as initiator,and N,N-methylenebisacrylamide?MBA?as crosslinker.The structure of the product was characterized by via Fourier transform infrared absorption spectroscopy,optical microscope and Thermogravimetric analysis.The optimum preparation conditions of the resin were as follows:the dosage of initiator was1.5%,the dosage of crosslinking agent was 0.4%,the neutralization degree of acrylic acid was 70%,and the dosage of polyvinyl alcohol was 0.8%.The absorbency reached 1226g/g and 99g/g in deionized water and 0.9wt%in NaCl solution,respectively.In terms of moisture resistance,the hygroscopic property of the IPN SAR was 9.1%lower than that of the single network SAR.In three different salt solutions?NaCl,CaCl₂,FeCl₃?,the IPN SAR had better liquid absorption performance than single network SAR,which indicated that the IPN SAR had better salt resistance.The absorption and release experiments of urea showed that the urea loading rate and release rate of SAR increased with the increase of urea concentration.Under the soil environment,the degradation rate of SAR could reach27.66%after 80 days.According to the study of two kinds of SAR with fertilizer slow-release property and degradable property,it was found that the SAR prepared by fertilizer,natural polymer,synthetic polymer and vinyl monomer as raw materials are not only have good absorbency property,but also have the properties of slow-release and degradation,so the SAR could reduce the environment.The results indicate that the SAR prepared in this paper has a good application prospect in agriculture and forestry.