Study of the porous network developed during curing of thermoset blends containing low molar weight saturated polyester

Polymerisation of unsaturated polyester/styrene blend added with a thermoplastic additive leads to the formation of a porous biphasic polymer network. In this paper, the porous medium was specifically studied by TEM associated with images analysis by chord length distribution and small angle X-ray scattering (SAXS). When the molar weight and/or the amount of low profile additive (LPA) are sufficient to ensure porosity higher than 2%, chord length distribution can be performed and is characteristic of a Debye random medium and Porod's law was observed in SAXS. The lengths deduced from Porod's law are similar to those observed for Debye random regime and are lower than 50 nm. These characteristics are closely related to the processes happening during curing and especially to the phase separation. For less porous samples, deviation from Porod's law was observed and could be attributed to additional scattering intensity coming from concentration fluctuations within polymer matrix. For nonporous samples, scattering intensity was only due to concentration fluctuations.