Study On The Performance Of UF Resin Modified Through Melamine And Oxidized Starch

Modified UF resin with melamine, polyvinyl alcohol and oxidized starch resin at a low F/U molar ratio was prepared. The modified UF resin could accord with the National Standards Class II plywood with a low formaldehyde emission.This article researched the influence of melamine dosage, feeding model of melamine and dosage of oxidized starch on the basic performance and cementation performance of the UF resin, and the curing characteristics of the resin by DSC.The results showed that:with the increase of melamine dosage, the solid content increased and the bonding strength was improved, however, the curing time of UF decreased as well as the content of free formaldehyde and formaldehyde emission; If the melamine dosage was fixed, changing the feeding model of melamine also influenced the basic behaviors of UF resin, when adding the melamine in batches, the solid content would increase, simultaneously decreased the curing time. With the increase of melamine content in the pre-reaction period, the free formaldehyde content and the formaldehyde emission exhibited a trend of decrease firstly and then increase, but the variation tendency of the bonding strength was contrary.The more oxidized starch was added, the lower solids content and the longer curing time UF resin became, oxidized starch can also significantly reduce the content of free formaldehyde and the formaldehyde emission, while the bonding strength was increased at first and then reduced, however when the dosage of oxidized starch was more than a certain limit the bonding strength would be reduced.With different curing system, the peak temperatures of DSC were different. A comparison of the two curing systems certified that the curing agent added a small amount of acid could accelerate the curing rate of the resin; the higher the heating rate was, the higher temperature the peak temperature curved to move to. When the curing agent and the heating rate kept constant, melamine dosage increased, the peak temperature of DSC curve will move towards low temperature, indicating that the resin is more easily cured. When the dosage of oxidized starch is5%or10%, the peak temperature of DSC curve was reduced, as oxidized starch makes UF resin cure more easily. However the oxidized starch dosage reached15%, the peak temperature is even higher.