Microwaves in most materials cause a rapid increase in temperature. The most important, however, is that this is done as evenly as possible throughout the entire cross-section of the material. This effect is used in many devices and technological processes. There are many examples of practical use of microwaves.
The term thermal treatment includes processes such as heating, thawing, cross-linking, curing, melting, evaporation, etc. The speed and intensity with which the technological process is to take place can be very precisely regulated.
Sandwiches, snacks, dumplings, dinner sets are only a part of food products sold from vending machines. Stored in a vending machine at a low temperature, they are microwaved before being released. Within 1 to 3 minutes (depending on the type and weight) a warm product is delivered to the consumer. The whole process takes place automatically, inside the vending machine.
In the food industry, thawing large blocks of frozen food (meat, butter, fats) is a long-term process during which uneven heating occurs, temperature increases on the surface, which in turn allows the development of microorganisms .
By using microwaves we get:
- shortening the process time,
- possibility of heating in the package,
- no growth of microorganisms on the surface (particularly important in the fish industry),
- limiting weight loss,
- keeping the pH constant (especially important in the meat industry),
- saving energy.
In the production process of composites using microwaves, the shaped and soaked element passes through the chamber in which the resin is cross-linked. Because the microwaves reach the inside of the element, crosslinking occurs as evenly as possible throughout its entire cross section. Additional advantages are: reduction of energy consumption, lack of system inertia (massive heating forms have been eliminated), quick change of shape of the manufactured profile.
When describing curing using microwaves, it is best to refer to curing of casting molds. Molding sands (silica, zirconium, chromite) often with the addition of resins, absorb microwaves well. Curing occurs throughout the entire cross-section of the form, regardless of its shape, complexity and size. In some solutions, IR (infrared) radiation is additionally used.