3. Introduction
UF resin was first produced in 1884 by Holzer, who was working with Bernhard
Tollens.
Urea-formaldehyde, also known as urea-methanal, so named for its common
synthesis pathway and overall structure, is a non-transparent thermosetting resin
or plastic.
It is produced from urea and formaldehyde. These resins are used in adhesives,
finishes, particle board, and moulded objects.
UF glue resins were the most important type of adhesives in the wood industry last
60 years, especially for the production of wood based panels.
4. In industrial production, urea resins are made by the condensation of
formaldehyde and urea in an aqueous solution, using ammonia as an
alkaline catalyst .
The condensation reaction gives a colourless, solution that can be spray-dried
to a powder for later use in coatings or adhesives.
it can also be mixed with cellulose filler to produce powders for moulding into
solid objects.
Under the influence of heat and pressure, the resin, at this point made up
largely of low-molecular-weight intermediate polymers or prepolymers, is
cured to its final state,
which consists of a three-dimensional network of interlinked polymer.
7. Manufacturing Process
Urea and formaldehyde reacted at reflux under acid
conditions to a required viscosity.
Resin is neutralized and cooled.
A further amount of urea is added to react with
remaining free formaldehyde.
Resin is evaporated to obtain the correct viscosity and
solids
9. Process control
Formaldehyde and urea are weighed into a reactor
from a weigh vessel.
Precision on formalin weighing is 0.02%.
Precision on urea weighing is 0.5%.
Viscometers and pH meters are calibrated daily.
Thermocouples are calibrated bi-annually
10. Properties
It has a very high tensile strength.
Has the property of flexural modulus.
Has the property of heat distortion temperature.
Has the capacity of low water absorption .
It has the property of mould shrinkage.
Has a property of high surface hardness.
11. Advantages
Higher maximum operating temperature.
Better dielectric constant.
Tracking resistance.
Dimensional stability compared with cellulose filled
urea formaldehyde
Lower cost
Good electrical insulator
12. Disadvantages
Lower High Density Temperature(HDT).
Higher water absorption and mould shrinkage.
Lower surface hardness.
can have toxic effects
breathing difficulties,