Abstract
AbstractThe mechanical properties and network structure of photocurable polymers are strongly dependent on processing conditions. Here it is reported that highly crosslinked acrylate systems undergo unexpected additional post‐curing during DMTA measurements, resulting in an increase in glass‐transition temperature (Tg). A detailed study of the conditions under which this increase in Tg takes place unequivocally shows that a small (0.1%) oscillatory strain applied above Tg is responsible for additional cross‐linking reactions. The effect of strain‐induced post‐curing is confirmed by applying post‐curing treatments under oscillatory shear strain in rheological tests. Different acrylate systems were characterized and the results show that the strain induced post‐curing depends on the network structure of the polymer. In polymer networks with an initial high crosslink density the effect is pronounced while in polymers with an initial lower crosslink density no shift in Tg is observed.
Highlights
The mechanical properties and network structure of photocurable polymers are strongly dependent on processing conditions
It is reported that highly crosslinked acrylate systems undergo unexpected additional post-curing during DMTA measurements, resulting in an increase in glass-transition temperature (Tg)
Different acrylate systems were characterized and the results show that the strain induced postcuring depends on the network structure of the polymer
Summary
L. Maassen and Rosaria Anastasio contributed to this study. Thermosets are highly crosslinked polymers,[1] in which the permanent crosslinks form a molecule with infinite. Molecular weight.[2,3] This gives thermosets advantageous properties such as toughness, high dimensional stability and good solvent and heat resistance.[1] A common way of producing thermosets is via photopolymerization.[3,4] Photoreactions occur very fast and at room temperature and are generally performed in bulk which reduces the use of solvents.[5] Another advantage is that the light-induced reaction gives spatiotemporal control over the polymerization reaction.[6]
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