Evolution of dispersion in the melt compounding of a model polymer nanocomposite system: A multi-scale study

Abstract

We investigate the morphological development of polystyrene (PS)-C 60 nanocomposites along the length of a prototype co-rotating twin-screw extruder with sampling capabilities. The effects of C 60 concentration and output on the morphological evolution along the extruder are studied employing a suite of characterization techniques covering a wide range of length-scales, thereby shedding new light on the dispersion mechanism in this model system. We show that the relatively new spin-echo small-angle neutron scattering (SESANS) technique is well suited to probe both the distribution and the dispersion of C 60. SESANS complements optical microscopy (OM) data as it covers sampling areas several orders of magnitude larger than OM. The multi-scale morphological information conveyed by OM, SESANS, SANS and rheological data shows that for larger outputs, C 60 agglomerates are eroded as they travel along the extruder, resulting in C 60 dispersion and distribution at both molecular and micrometric levels. The picture is more complex when smaller feed rates are used, as the evolution of C 60 dispersion depends on the C 60 loading. For larger C 60 contents, agglomeration develops along the extruder, whereas dispersion is improved for smaller C 60 contents. Overall, it is concluded that an over-high feed rate in extrusion does not necessarily result in a bigger size of the nanoparticle agglomerates because of the complex interplay between stresses and residence time.

Different agglomeration properties of PC61BM and PC71BM in photovoltaic inks – a spin-echo SANS study

“…Full details are presented in ESI † along with the relevant theory. SESANS has found some recent practical applications in materials science, for instance in the study of fullerene agglomerates in polymer composites 58,59 and the porosity of silica Stöber particles. 60 In this work, we describe the rst application of SESANS to the study of the agglomeration behaviour of the functionalized fullerenes PC 61 BM and PC 71 BM in different organic solvents, with relevance to organic photovoltaics.…”

Recent Advances in Poly(Ionic Liquid)-Based Membranes for CO2 Separation

“…SANS probes the ~1–300 nm length scales, albeit in reciprocal space, whereas SESANS probes the 50 nm–15 μm length scale range [ 55 , 56 ]. Several studies have explored polymer systems such as colloids [ 57 ] and fibrous calcium caseinate gels [ 58 ].…”

Improving the dispersion of multiwalled carbon nanotube in polypropylene using controlled extensional flow

“…In order to more clearly assess the effects of extensional flow on the rheological properties, the values of the crossover frequency (ꞷ c ) and also the short relaxation time (t r ) were determined, which are shown in Table 3. The relaxation process referred to in the measurement is associated with relaxation of the PP chains, probably by the reptation mechanism [38][39][40] . We can verify that when processed with the flow-through device, the compositions have their crossover frequencies shifted to lower values, that is, longer relaxation times, which are involved with higher degrees of interaction between MWCNT and PP chains, corroborating that improved degrees of dispersion were achieved for these compositions due to the finer dispersion of MWCNT through the PP matrix.…”