Composite Mold behavior / Thermodynamics

  • Thread starter Sinope
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Dear All,

Currently we have changed from our epoxy tooling (molds) to aluminium tooling to obtain more accuracy in the dimensions of our final product.

Our resin is preheated to 50 degrees Celsius before injection and our epoxy tooling have similar temperature levels. At these levels the viscosity is adequate to fill the mould and there doesn't seems any undesirable (runaway) exothermic reaction of the curing resin.

Changing to aluminium molds seems currently creating an almost immediate exothermic reaction which prevent us from making products. Lowering down the mould temperature seems not to help and will affect the viscosity in a negative way.

Although the thermal conductivity of Aluminium (+/-250) is much higher than from Epoxy (+/-0.35), and its heat capacity around 50% higher, the temperatures of the Epoxy mould and the Aluminium mould are the same during the injection.

Could it be that the Aluminium mold gives more heat at the same temperature as the epoxy mold and will accelerate the exothermic reaction? Our there any Physical Properties that will described these effects in a better way?

Thanks!
 

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