from witco that melts and freezes near room temperature u02dc 75 u00b0 f would be selected for food serving and other higher temperature uses a phase change material that melts in the region of 147 u00b0 f e g parvan 147 from exxon would be selected in prior research glycerine at about 10 wt has been found to be an effective microwave absorbing additive in phase change material silica dry powders for hot medical therapy and warm clothing applications in the current melt mixed composite a somewhat lower concentration in the amount of about 7 8 wt appears to heat effectively in about 4 minutes to a temperature well above the melting point of the phase change material component a somewhat more effective alternate to the glycerine as a microwave heating additive is the special grade of cabot conducting carbon black xc 72 r from cabot corp boston mass this black will heat effectively at lower concentrations than glycerine a further advantage of the carbon black as a microwave heating additive is that since it is not a liquid that has to be taken up by the silica gelled a formulation with somewhat higher concentration of phase change material could be used the major disadvantage of carbon black is that even in low concentrations the color of the composite will be changed to a.