Composites
PRINCIPLE
Macromolecules of a catalyst contain polar groups, which produce local overheating in microwave (MW) field at macromolecular level and thermal difference between polar groups inside the molecules and the other non-polar parts of molecules. The stronger the dipole moment, the higher the temperature of local "hot" spots, which accelerates the hardening reaction.
DIFFERENCES IN HEATING METHODS
In comparison with conventional heating at the same temperature and with the same concentration of components entering the reaction, epoxide resins belong to materials with higher speed of reaction during MW heating. With microwaves, the exothermic reaction can be started uniformly in the whole volume of the material, whereas traditional heating in hardening head affects only the surface of the profile.
SPEED
Microwaves distinctly accelerate processing capacity, because the speed of heat transmission into the core of a material significantly limits the speed of drawn profile passing the line. The hardening reaction can be thus achieved by very small MW outputs.
UNIFORMITY OF HEATING
It is very high by using microwaves. For that reason, the improvement of mechanical properties of a profile, or production of larger profiles with complex shapes can be achieved. The MW energy batching depends, besides the size and shape of a profile, also on a resin and catalyst type.
DRYING OF FIBRES
If microwaves are used also for removing atmospheric moisture from a bundle of glass and carbide fibers, extremely favourable mechanical properties, or reduction of profile thickness, can be achieved. That is very important for high quality flat profiles.
