engleski

Thermal effects of cure reaction for unsaturated polyester in moulds of different shapes

The cure of unsaturated polyester was studied by using experiments and a model of the process. The kinetic parameters were calculated from the heat flux – time curves obtained by differential scanning calorimetry (DSC, Netzsch – Simultaneous Thermal Analyser DSC 200 ), working in DC (isothermal) mode. The temperature – time histories were studied in moulds of different shapes. The numerical model was constructed by taking into account the heat transferred by conduction through the resin, as well as the kinetics of heat generated by cure reaction. The contributions to the rise in temperature from heat conduction and chemical reaction are different in different parts of the composite, and can explain the temperature -, or conversion – time histories. In order to build up the model for the cure process in a composite sheet, the following assumptions are made: 1.) Negligible temperature change during flow. 2.) Homogeneous and well-mixed reaction system. 3.) One-dimensional heat conduction. 4.) Constant density r, heat capacity cp, heat conductivity l, and heat of reaction DHr. 5.) Constant mould wall temperature through the entire cure. Base on above assumptions, the basic equations of heat transfer can be written as: Energy balance: Reaction: By considering the reaction-cure – time, temperature – time and heat-flux – time histories developed within the sample, more extensive knowledge of the process can be obtained. The effect of the conduction heat transfer through the composite and of internal heat generated by the cure reaction is clearly shown, despite the complexity of the process.

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