Characterization of the UV cured

homopolymer glass transition

Relationship between glass transition and

double bond conversion

It is very well known that the glass transition

temperature Tg of thermosetting systems increases

with the conversion of reactive 펑션(기능), as

illustrated in Figure 4 for UV-cured films. It appears

that in free radical polymerization, Tg increases

quite sharply for high degree of conversion. For

example with ethoxylated trimethylolpropane

triacrylate (SR454) film, a change from 92 to 98%

of double bond conversion leads to an increase of

25°C in Tg. It is therefore crucial to indicate both

Tg and percentage of double bond conversion at

the same time.

Limitations of double bond conversion

The maximum double bond conversion (100%) can

not always be reached, even with a high UV-dose.

This can be understood in terms of the vitrification

phenomenon already mentioned.

In the glassy state, molecular mobility is very much

restricted and very slow diffusion does not allow

chains and radicals to meet each other. The system

therefore is not capable of reaching its theoretical

Tg at 100% conversion.

Limitations of Tg

Trimethylolpropane triacrylate (SR351) film

exhibits a very special behavior where the