Effect of tertiary polysiloxane on the phase separation and properties of epoxy/PEI blend

Abstract

Epoxy functional siloxane (DMS‐E09) was blended with epoxy resin (DGEBA) and thermoplastic polyetherimide (PEI). The results of morphology monitoring indicated that the reaction induced phase separation for all blends followed the spinodal phase separation mechanism. The microstructure changed from co‐continuous of 25 wt% epoxy/PEI system to phase‐inversion structure of 30 wt% epoxy/PEI system regardless of the content of the tertiary component DMS‐E09. By comparing the onset time of phase separation between the two designated systems, the sequential occurrence of primary macrophase separation in co‐continuous phase and secondary microphase separation in PEI‐rich phase for 25 wt% epoxy/PEI system was identified. Studies of the thermomechanical properties of the DGEBA/PEI/DMS‐E09 blends found that storage modulus increased with the addition of PEI but decreased with DMS‐E09 monotonically. The value of Tg decreased with the addition of the tertiary DMS‐E09 but was offset partially by the presence of PEI.

Phase separation of ternary epoxy/PEI blends with higher molecular weight of tertiary component polysiloxane

“…In comparison with previous work with DMS-E09, 42 it is seen that DGEBA/PEI/DMS-E11 are more immiscible. For example, the phase separation of blends PEI-25–E11-10 and PEI-30–E11-10 took place phase separation at 134 s, 152 s, respectively.…”

“…It is quite different with the results from DMS- E09 blends, which the continuous PEI-rich phases still remain distinctly. 42 Moreover, as shown in the magnied insets in Fig. 4b-e, spherical particles of 15-25 mm are found in DGEBArich phase and increases with DMS-E11 content, which are also regarded as DMS-E11-rich phase.…”

“…It indicates that the phase separation of all blends follows the viscoelastic phase separation behavior. Therefore, the introduction of higher molecular weight tertiary component DMS-E11 and increase of siloxane segments (in comparison with DMS-E09 systems) 42 have not changed the mechanism of phase separation between DGEBA and PEI. …”

“…This makes an obvious difference from the results of co-continuous system with DMS-E09, which is more miscible with DGEBA than PEI and lead to a signicant reduction of T g1 value corresponding to DGEBA-rich phase. 42 Furthermore, the ratio of amplitude (h 2 /h 1 ) from the tan d curve can predict qualitatively the kind of morphology generated for ternary blends DGEBA/PEI/DMS-E11. 45,46 For the ternary DGEBA/PEI-25/DMS-E11 system, the ratios of h 2 /h 1 are around 0.5-0.6 (Table 2) when the content of DMS-11 is lower than 10 wt%.…”

“…Our previous works investigated the miscibility between DGEBA and epoxy terminated siloxane with lower molecular weight (DMS-E09), 38 and the effects of DMS-E09 on the phase separation and properties of blends DGEBA/PEI. 42 The molecular weight of DMS-E09 is 362 and its corresponding monomer has only one –Si–O–Si– unit. It was miscible with DGEBA to some extent and entered mainly into DGEBA-rich phase in ternary blends DGWBA/PEI/DMS-E09.…”