Study On The Law Of Formaldehyde Release Of Agricultural Urea-formaldehyde Resin And Control

Urea formaldehyde(UF) resin application in agriculture mainly has two aspects:one is as a coated material of slow release fertilizer; the other is the straw pot adhesive. UF resin has low price, but the slow release formaldehyde pollutes the agricultural environment, and harm the crops normal growth. The target of this paper is how to reduce the formaldehyde emission of straw basin port that is pressed by urea-formaldehyde resin, and studied the formaldehyde emission of straw pot by technology improvement, and reduced the formaldehyde emission by lower F/U molar ratio, melamine modification and new curing agent of melamine oxalate. Infrared spectroscopy (IR), differential scanning calorimetry (DSC), thermo gravimetric analysis (TG) and other modern analysis means are used to study structure and curing characteristics of UF resin. Influence of formaldehyde and melamine to crops growth have been studied in the aspect of seed germination and protective enzyme activity. The conclusion are as follows:(1) With the different F/U molar ratio and different curing system, the formaldehyde emission of UF resin gradually decreased, after 5-6 days tended to be stable; when F/U molar ratio lower, melamine modified and added with curing agent, formaldehyde emission reduced.(2) Melamine oxalate as a new curing agent can solve the problem of curing incomplete, the defect of low bonding strength that the traditional curing agent of ammonium chloride on low-formaldehyde UF resin, and can reduce the release quantity of formaldehyde in UF resin.(3) IR analysis results shows that the main reason which the formaldehyde emission reduced is that the content of active groups in UF resin such as-CH2OH,-CH2-O-CH2 decreased, and Uron ring is increased. The results of DSC helps selecte suitable curing agents and curing process and determine the amount ofcuring agents in process of pressing straw pot.(4) When the concentration is greater than 100mg/L, formaldehyde and melamine treatment on seed seedling growth have the obvious inhibitory action. Protective enzyme such as POD and CAT scavenging capacity is affected, influenced the normal growth of plants.When using F/U molar ratio of 1.2,6% of melamine modified urea-formaldehyde resin, melamine oxalate as the curing agent, the straw pot cumulative formaldehyde concentration can lower than 100mg/L, does not affect the normal growth of crops.