Enhancement of pre-pressing performance of urea formaldehyde resin adhesive
Urea formaldehyde resin is the main adhesive used for fabricating wood-based panels in China.The pre-pressing performance of this adhesive is crucial to the manufacture of plywood,which determines the production efficiency to a certain extent.In earlier years,urea formaldehyde resins were typically prepared through high formaldehyde molar ratio formula.Bonding performance of the products is the most critical indicator.To ensure the environmental friendliness of artificial boards,modified urea formaldehyde resin has generally been manufactured based on a low formaldehyde molar ratio formula.The pre-pressing performance of this adhesive is weaker than that of traditional urea formaldehyde resin.Therefore,it is necessary to explore efficient techniques to improve the pre-pressing performance of low formaldehyde molar ratio adhesives.The purpose of this study was to improve pre-pressure efficiency of glued slab by inserting phenolic substances into the molecular structure of urea formaldehyde resins.The contribution effect and mechanism of the molecular structure and dosage of phenolic substances to the pre-pressing performance of urea formaldehyde resin were investigated.The results of the study on the impact of the phenolic substances on the properties and main performances of urea formaldehyde resin showed that the pre-pressing performance of urea formaldehyde resin can be improved significantly by inserting phenolic structure into the resin molecules.The per-pressing performance of the adhesive improved with the increase of hydroxyl content in phenolic substances.An improvement of the per-pressing performance of the urea formaldehyde resin adhesive was found when phenolic substances added at an amount less than 1％.After 1 h cold-pressing treatment,the pre-pressing strength of the modified urea formaldehyde resin adhesive prepared by adding the same amount of phenol,catechol and pyrogallol increased by 44.74％,100.00％,and 113.16％,respectively,compared to control adhesive.The hydrogen bonding between phenolic hydroxyl groups and the adhesive matrix was the key reason for the improvement of the per-pressing performance of the modified urea formaldehyde resin adhesives.This study provides a feasible scientific basis and technical reference for solving the problem of poor per-pressing performance of the low formaldehyde molar ratio formula urea formaldehyde resin.
urea formaldehyde resin adhesiveplywoodpre-pressinghydroxylhydrogen bond
万方数据
维普
