Sea-island morphology

The solvent-etched fracture surface of folly cured PEI modified epoxy with different composition is shown in Figure 3.8. For PEI content smaller than 10wt%, the PEI-rich phase is dispersed in a continuous epoxy-rich matrix [i.e., sea-island morphology is observed (a and b)]. Above 25 wt% PEI content, nodular structure was observed (e and f) where the epoxy-rich phase forms spherical nodules and the PEI rich phase forms the matrix. With PEI content between 15 wt% and 20 wt%, dual phase morphology, where sea-island morphology and epoxy nodular structure coexist, is present (c and d). Similar morphology was observed in PEI/BPACY blend [47],... 

Table 3.2 shows the influence of the initial PEI concentration on the resulting particle size distribution. Both the size and the number of PEI domains increased in the sea-island morphology, whereas the size of thermoset nodule decreased and the number of nodules increased in the nodular morphology as the initial PEI concentration was increased. 

In the composition range where the sea-island morphology was shown, the increase of the PEI concentration caused an increase in the PEI phase volume and a lowering of the... 

Kim et al (1999) examined the morphology and cure of semi-IPN epoxy resin or dicyanate-polyimide/polysulfone-carbon-flbre Aims. Polyimide or polysulfone Aims were inserted into the curing epoxy-dicyanate monomers to form semi-IPNs with sea-island morphology at the thermoset-thermoplastic interface. The final carbon-flbre-thermoplastic-dicyanate Aims had fracture toughness three to five times higher than that of unmodified carbon-flbre-dicyanate composites. 

Studies by Rico et al. also shows that increasing the cure temperature causes the particle size to decrease, but increasing the amount of them in sea-island morphology, while in a nodular one the particle amounts decrease and their size increase. Therefore, any meaningful change could be observed during the dual-phase proportion [30]. 

Bhardwaj and Mohanty [8] proposed and demonstrated a new industrially relevant methodology to develop a polylactide (PLA)-based nano blend having outstanding stiffness-toughness balance. In this approach, a hydroxyl functional hyper branched polymer (HBP) was in situ cross-linked with a polyanhydride (PA) in the PLA matrix during melt processing. There was formation of new HBP-based cross-linked particles in the PLA matrix. TEM and AFM revealed the sea-island morphology of... 

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