Effect of Mesoscopic Fillers on the Polymerization Induced Viscoelastic Phase Separation at Near- and Off-Critical Compositions

Abstract

We have investigated the effect of mesoscopic fillers on the polymerization induced viscoelastic phase separation of thermoplastic modified thermosets at near- and off-critical concentrations using optical microscopy, time-resolved light scattering, dynamic mechanical analyses, and rheological instrument. Mesoscopic fillers including sepiolite and nanosized silica showed a significant enhancement effect in viscoelastic phase separation, and resulted in pronounced differences in the phase structures at all concentrations of polyetherimide modified epoxy resins with dynamic asymmetry. For blends near critical concentration, the introduction of fillers led to much finer phase structure with smaller characteristic length scale. At off-critical composition (i.e., blends with low concentration of slow dynamic component), the strong polymer chain entanglement resulted in enwrapped mesoscopic fillers within a slow dynamic phase. The rheological behavior of the blends clearly demonstrated the significant enhancement effect of mesoscopic fillers in the viscoelastic phase separation. The apparent activation energy of polymer chain mobility obtained from dynamic mechanical study of glass transition reflected strong wrapping behavior of polymer chains on mesoscopic fillers, which were consistent with the rheological and light scattering study.

Effect of Attapulgite Nanorods and Calcium Sulfate Microwhiskers on the Reaction-Induced Phase Separation of Epoxy/PES Blends

“…In other words, the incorporation of fillers show an opposite effect on the phase separation: the nanoscale fillers pin down the phase separation while micron-sized fillers accelerate the decomposition process at some stages. On the basis of the above experimental results and previous works [19,[28][29][30], a possible scenario for the effect of mesoscale fillers on the phase separation of PES-modified epoxy blend could be as follows: in a dynamic asymmetric system with consider amount of slow dynamic components (PES at higher content than critical concentration), the diffusion of the fast dynamic epoxy-rich phase is prevented by the slow dynamic PES-rich phase, the addition of nanoscale fillers could enhance this process by the chain entanglement of slow dynamic phase with the filler surface due to the nanoscale fillers providing sufficient surface area [29,30]. Even though the nanoscale fillers have higher affinity to the fast dynamic phase, the elastic deformation of the slow dynamic phase could also form chain entanglement with the filler surface due to the high normal stress from the shear and shrink of the slow-dynamic phase.…”

“…While in thermoplastic modified thermoset blends with dynamic asymmetry, the chain mobility difference of the two parts makes the viscoelastic effect play a crucial role in phase separation process [28]. The addition of nanoscale fillers further enhanced this viscoelastic effect from the chain entanglement of slow dynamic part with the filler surface, which significantly hindered the phase structure evolution process and thus results in a refined phase structure with much smaller characteristic length scales [29,30].…”

Constructing a filler network for thermal conductivity enhancement in epoxy composites via reaction-induced phase separation

“…5D. This means that a 3D interconnected template is not formed and thus a 3D interconnected filler network is not formed [52,73]. For comparison, the distribution of GNPs in the epoxy composites without PES is random, as shown in Fig.…”

Preparation of polyethylene microporous membranes with high water permeability from thermally induced multiple phase transitions

“…Decreasing the content of polymer in polymer/diluent solution may possibly increase the water permeability at the cost of mechanical properties. Therefore, although there is a large amount of theoretical investigations on the viscoelastic phase separation [16,[19][20][21][22], LLPS through spinodal decomposition to form bicontinuous structure is still preferred in application.…”