Delayed Shrinkage. Physical and Chemical Aging

We can take advantage of this situation by increasing the light intensity we can increase the conversion while the mobility is still high. In this way, the ultimate conversion will increase with light intensity (Table 5) 

An increase of mobility may also be reached by increasing the temperature which also results in an increased ultimate conversion (Table 6) 

It must be noted that the extents of reaction determined by calorimetric measurements are kinetically defined. The reaction is considered to be finished when its rate falls below the limit of detection, that is when the rate of heat production has decreased by 2-3 decades with respect to the maximum rate. Below we will show that the reaction may go on for quite a long time at a very low and continuously decreasing rate. 

Since the rate law for self-decelerating processes is unknown, extrapolation of conversion with time is impossible. In principle, methods like IR spectroscopy would be suitable but they often suffer from lack of accuracy, notably when small changes have to be detected near the end of the reaction. 

So the physical process of shrinkage is coupled to some extent with the chemical process of polymerization but shrinkage is not a measure of conversion, as is normally observed with liquid systems. 

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