Methylal was used for several reasons: it was used as co-blowing agent with 134a in order to dissolve a great amount of it, since 134a is gaseous at room temperature (boiling point: 26.5[degrees]C); moreover, it can be considered as a possible HCFC substitute as it has no ODP and negligible GWP compared to other HFCs.
In this section, HFC, HCFC, HC, and methylal are generally called physical blowing agents.
Alternatively, 134a can be used in mixture with some liquid co-blowing agents (e.g., methylal), which are able to solubilize large quantities of it.
Moreover, in the presence of methylal or n-pentane the initial value is somewhat higher, probably due to the higher vapor phase thermal conductivity rather than for the mean cell dimension; in fact, n-pentane blown foam shows lower mean cell diameter but higher initial thermal conductivity.
Moreover, the results showed that methylal may be usefully employed as an environmentally-friendly blowing agent in mixture with 134a, while its use with 245fa does not seem to be optimal.