우레아-폼알데하이드 레진 합성
The resin is the general term used technically for solid, hard to soft, organic, non-crystalline products having a broader or narrower molecular mass distribution.
They normally have a melting or softening range, are brittle in the solid state. Resins are in general raw materials, for example for binders, curable molding compositions adhesives and coating. Resin can be divided as natural resins and synthetic resins.
The most important synthetic resins are phenol-formaldehyde resins, urea-formaldehyde resins, melamine-formaldehyde resins, polyesters resins, silicone resins, and ketone-aldehyde resins.
They are usually thermoset type polymers. Thermoset resins are usually prepared as pre-polymer and than in the second stage they are cross-linked by the effect of catalyst, heat and pressure. This polymer is used to formulate adhesives and coating agents or is mixed with wood fiber, pigments, and other substances to produce powders that can be molded into solid objects. Under the influence of heat and pressure, further reactions occur that can convert the polymer into a moisture- and heat-resistant resin. The molecular structure of the final product is that of three-dimensional network resembling those of resins made by the reaction of formaldehyde with phenol or sith melamine.
The possible reaction of urea with formaldehyde and formation of urea-formaldehyde resin are summarized in the following scheme.