Numerical Simulation and Experiment of Hardening Behaviors in Unsaturated Polyester Resin Artificial Marble Blocks Under Microwave Radiation

A high-power continuous microwave hardening system at the frequency of 915 MHz and the maximum output power of 60 kW is established to harden unsaturated polyester resin (UPR) artificial marble blocks of typical size 1600 x 900 x 600 mm
³
in the industrial production. The microwave hardening system contains three major sections, including a 2000x1300x900 mm
³
multimode cavity, microwave generators, and three groups of feeding-waveguide systems from microwave generators to the multimode cavity. An optimum hardening method by adjusting the value of incident power and processing time is found on the basis of study of UPR properties and can promote products qualities. A numerical coupled electromagnetic and heat transfer model has been built to simulate microwave hardening process and to predict temperature profiles of artificial marble blocks successfully. The result that there is no significant change in temperature profiles between fixed and temperaturedependent thermal parameters indicates thermal conductivity K and specific heat capacity CP, which are not sensitive to temperature. The effect of height between artificial marble block and cavity bottom on electromagnetic field, absorption power, and temperature distribution is also discussed in this paper. The contrast results between the two hardening methods prove that the microwave hardening can achieve better comprehensive characteristics than natural hardening. The establishment of the high-power microwave hardening system has improved the industrial production efficiency of UPR artificial marble 300 times.