Modification of epoxy resins with different molecular weight poly(aryl ether sulfone) as effective toughening agents

This contribution investigates the toughness efficiency of poly(aryl ether sulfone)s (PSFs) with different number average molecular weights (M n , PSF2.4K: 2400 g/mol, PSF7.3K: 7300 g/mol, and PSF18K: 18000 g/mol) on the diglycidyl ether of bisphenol A epoxy resin (E51) with 4,4′-diamino diphenyl sulfone (DDS) as curing agent. Compared to the pure E51/DDS epoxy resin (16.3 kJ/m 2 ), the impact strengths of the E51/DDS/PSF resins containing 10 wt% PSF2.4K, 5 wt% PSF7.3K and 10 wt% PSF18K increase up to 27.2 kJ/m 2 , 37.3 kJ/m 2 , and 39.7 kJ/m 2 , respectively, indicating that PSFs are very effective in toughening E51. The higher the M n of PSF, the higher the impact strength of the E51/DDS/PSF composites, meanwhile, the tensile modulus of the composites reduced slightly. For example, the tensile modulus of the E51/DDS/PSF composite with 5 wt% PSF18K decreases slightly from 1.75 GPa (pure E51/DDS) to 1.64 GPa. The effect of PSF18K on the toughness of diglycidyl ether of bisphenol F epoxy resin (HS170), diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate epoxy resin (TDE85), and 4,4′-diaminodiphenylmethane epoxy resin (AG80), has also been examined. With the addition of 5 wt% PSF18K, the impact strength of HS170/DDS/PSF composite increases from 19.5 kJ/m 2 to 31.9 kJ/m 2 . However, PSF18K has no significant effect on the toughness of TDE85 and AG80. The results demonstrate that PSF is an effective toughening agent for bifunctional epoxy resins (E51 and HS170) but not for tri- and tetra-functional epoxy resins (TDE85 and AG80).