(고분자실험) Preparation of Urea-formaldehyde Resin
- 최초 등록일
- 2008.01.01
- 최종 저작일
- 2007.04
- 7페이지/ 한컴오피스
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(고분자실험) Preparation of Urea-formaldehyde Resin내요으로
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목차
1. Title
2. Date
3. Principle
4. Apparatus & Reagent
5. Procedure
6. Result
7.Error&Cause
8.Discussion
9. Reference
본문내용
1. Title : Preparation of Urea-formaldehyde Resin
2. Date :
3. Principle :
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 coatings. Resin can be divided as natural resins and synthetic resins.
The most important synthetic resins are phenol-formalde
-hyde resins, urea-formaldehyde resins, melamine-formald -ehyde resins, polyesters resins, silicone resins and ketone-aldehyde resins.
They are usually thermoset type polymers. Thermoset resins are usually prepared as prepolymer and than in the second stage they are cross-linked by the effect of catalyst, geat and pressure.
The possible reaction of urea with formaldehyde and formation of urea-formaldehyde resin are summarized in the following scheme.
Urea-formaldehyde resins are usually synthesized by heating urea and formaldehyde in basic media, i.e. in the presence of mild alkalies, such as pyridine or ammonia. The urea and formaldehyde undergo a condensation reaction in which they combine to form a water-soluble polymer.
The reaction is 10-20 minutes at 50-60℃. Catalytic crosslinking is carried out with free acids(acid hardening). Large amount acid (pH=2) cause the crosslinking to occur at room temperature (cold curing).
참고 자료
-http://en.wikipedia.org/
-http://en.wikipedia.org/wiki/Divinylbenzene