Polymerisation viscosity changes during

The difficulties associated with heat transfer can be overcome, and higher molecular weight polymers obtained, by the use of an emulsion system. The heat of polymerisation is readily dissipated into the aqueous phase and the viscosity of the system changes only slightly during the reaction. 

Figures 15.11(a) and (b) describe the flow and cure of a B-staged aerospace adhesive during a complex thermal history, using parallel plate sensors. Specifically, Figure 15.11(a) shows how the loss factor (log e") changes with time and temperature. The increase in log e" between 25 and 80 °C is due to softening of the adhesive. As the temperature is held isothermally at 80 °C for 30 minutes, log e" remains constant. Then, between 60 and 75 minutes as heat is applied at a rate of 1 °C/min, temperature-induced fluidity causes the viscosity of the resin to decrease. After 75 minutes, the resin polymerises and develops a three-dimensional network, as indicated by the decrease in log e".

During the polymerisation of liquid monomer droplets, a physical change occurs whereby the very low viscosity monomer(s) is converted to either a high viscosity liquid, a soft and rubbery gel or a hard, tough or brittle solid. 

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