Methods of Processing Aminoplasts

The principal processing methods of aminoplasts are pressing, pressure casting and extrusion. 

Pressing is one of the widespread methods for the manufacture of articles from aminoplasts. There exist varieties of pressing direct (compressional) and casting (transfer). 

In direct pressing the pressure directly affects the material confined within the space of a heated mold. In the press-mold the effect of pressure and heating accounts for the fact that the material is compacted, softened, plasticized and thereafter hardened to the required degree. 

In compaction the particles of the material come so much close to one another that there arise between them the forces of intermolecular interaction, and thus a compact body is formed. 

The interrelationship between the density of the material (q) and pressure in pressing (P) is fairly complex and is expressed by an exponential function. Investigations [30] have revealed that under the actually used pressures such a function can be substituted with a linear one of the type q = P/RT (A -f BP), where R is a universal gas constant T is the temperature of pressing, °C A and B are constant coefficients. 

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