Unsaturated polyester resins modified with poly(ε-caprolactone)–perfluoropolyethers block copolymers

Poly(ε-caprolactone)–perfluoropolyether–poly(ε-caprolactone) block copolymers (TXCL) synthesised from Fomblin Z-DOL TX (TX) have been mixed with conventional unsaturated polyester resins (UPR) to prepare fluorine modified UPR (FUPR). A preliminary investigation on the compatibility of uncured FUPR systems has shown that the presence of PCL blocks leads to an enhancement of compatibility with respect to pure perfluoropolyether macromers. The compatibility tends to decrease by increasing the TXCL concentration in the mixture depending on both molecular weight and TX/PCL ratio. Also the morphology of FUPR after curing was strongly affected by the rate of curing and by a critical balancing of TX/PCL ratio and molecular weight of TXCL copolymers. Both transparent and opaque FUPR were obtained for the same composition at different curing rates; high curing rates (i.e. high concentration of initiator/activator) favoured the formation of transparent FUPR through a kinetic control of phase separation. Scanning electron microscopy (SEM) analysis was in good agreement with the macroscopic results obtained by visual inspection. XPS analysis showed a very strong surface enrichment in fluorinated segments, which increases by increasing the TX/PCL ratio. Mechanical tests showed a slight plasticization effect (compared to UPR control) together with a very strong improvement in the absorbed energy at break EB showing the best toughening effect for TXCL with intermediate TX/PCL ratio. Finally, a minimisation of the water diffusion coefficient value (five times lower than UPR control) was noted for UPR modified with TXCL having intermediate PCL segment length.