Study On The Curing Procedure Of Urea-Formaldehyde Resin With Low Formaldehyde Emission

At present, the output of wood-based panels has more than 45 million m3 in China, urea-formaldehyde (UF) resins are basically used, most of it have high formaldehyde emission (FE) which cause FE over standard, producing environment and using environment of wood glued products are seriously polluted. Therefor, the compulsive standard " Indoor decorating & refurbishing materials limit of formaldehyde emission of wood-based panels and finishing products" is published by government in Jan, 2002,companies of wood-based panels are restricted to use UF resin with lew FE.Consequently, study on the curing mechanism of UF resin with low FE is basic theon problem related to the development of wood-based panels industry in China and also bottle-neck problem affect wide application of UF resin with low FE.Study on the curing mechanism and glue bond properties in different curing system of three typical UF resin with low FE of different synthesis technology and modification means,it revealed curing characteristics of UF resin with low FE. Especially on slow curing speed and unideal glue bond properties UF resin with low molar ratio, it can solved by synthesis technology, modifier and different curing system. UF resin with low FE developed base on typical recipe have partially used in wood-based panels .The thesis studied on the curing procedure, chemical structure, FE and mechanics properties of three UF resin with low FE by 13C NMR, TBA, DSC, DMA and 13C CP/MAS NMR in details. The chemical structure of three kind of cured UF resin with low FE in different curing system is different. With no hardener, the content of methylene ether of cured UF resin is low, methylol is high, crosslinkage is low, FE is high also. With hardener, the content of methylol decrease, methylene ether increase, curing agent accelerate the crosslinking and curing reaction. The curing effect of different kind of UF resin in different curing system is different, chemical structure, FE and mechanics properties of cured UF resin is different. The results revealed the curing procedure and curing characteristics of UF resin with low FE, it has important practical function on the popularization and application of UF resin with low FE.It is one of the common goal to reduce production cost for enterprise and researcher. A UF resin with low FE and low cost has been developed in this research, open up a new modification means, it has wide application future.Study on the curing mechanism and curing characteristics of UF resin with low FE, it provide scientific basis to determine synthesis technology; evaluate glue bond properties andpredict glue bond durability. It ofler theoretic foundation to open up new modification means; determine synthesis technology; provide theoretic foundation to develop new curing system of UF resin with low FE, to meet different needs of various technology of wood-based panels. The research has significant theoretic value to promote the deep development and wide application of UF resin with low FE and important realistic meanings to ensure rapid development of wood-based panels industry in China.