Preparation of Slow-Released Films Based on the Natural Rubber Latex Modified by Cassava Starch

Abstract

Nitrogen fertilizer is an important nutrition for the crops. However, the majority of common nitrogen fertilizers have not been absorbed by the plant, which causes great economical loss and environment pollution. In order to solve the above problem, the biodegradable slow-release coating materials for urea was prepared by introducing the active free radical of short chain cassava starch into concentrated natural rubber latex. The effects of the amount of starch, modifier dosage on the water absorption kinetics of natural rubber latex slow-released film, and the mechanical properties, slow-released performance, thermal stability and mildew characteristics in the tropical climate conditions was also examined. The results showed that the swelling rate of natural latex composite film increased with the increment of starch content. However, the water modifier imposed a different effect on the initial swelling rate and the equilibrium-swelling ratio of latex composite film. The preliminary swelling was slow but the time for achieving a basic balance state of the swelling was short. In addition, the thermal degradation process of the natural rubber latex slow-released composite film was divided into two stages. The maximum heat loss temperature of each stage shift toward the each other due to the increasing dosage of water modifier. The biodegradability of the composite film improved but the release rate of urea got faster when the starch content increased.