Novel synthesis of branched polypropylene via solid-state shear pulverization

Importance of superior dispersion versus filler surface modification in producing robust polymer nanocomposites: The example of polypropylene/nanosilica hybrids

“…4 compares shear storage modulus as a function of frequency (G 0 (u)) and nanosilica content for PP/p-NS and PP/m-NS nanocomposites. For both nanocomposite types, a very small reduction in G 0 occurs relative to neat PP upon adding 1 wt% nanosilica, which is likely due to a very small reduction in PP molecular weight (a maximum of~3% reduction in M w is observed when neat PP is subjected to SSSP processing of similar harshness [82]) with SSSP processing. (We note that reductions in G 0 could also arise from chain disentanglements near the nanoparticles surfaces.)…”

“…For example, SSSP has been used to produce in situ compatibilized and quasi-nanostructured immiscible polymer blends [78e80] and to achieve intimate mixing of polyethylene and ultrahigh molecular weight polyethylene [81] that, due to extraordinary viscosity mismatch, cannot be mixed by conventional melt processing. It has also been used to produce ester and maleic anhydride functionalized PP [82,83] and long-chain branched PP [84] with dramatically suppressed molecular weight reduction relative to that accompanying functionalization by melt processing. Finally, it has been used to obtain very good to excellent dispersion in polyolefins, superior to that by conventional melt processing, of many unmodified fillers and nanofillers [69,85e93], including carbon nanotubes [85], graphite [86,87], rice husk ash [88], and cellulose nanocrystals [89] that have no favorable interactions with PP beyond van der Waals interactions.…”

Dispersion and Property Enhancements in Polyolefin/Soy Flour Biocomposites Prepared via Melt Extrusion Followed by Solid‐State Shear Pulverization

“…In comparison to conventional melt processing, solid‐state processing can give rise to extraordinarily large compressive and shear forces . In order to overcome the limited stresses and forces developed during melt processing, some researchers have employed solid‐state processes to produce well‐dispersed polymer blends and composites . Batch solid‐state processes such as pan milling and ball milling have been used to expose blends and hybrids to high forces and stresses, leading to improved dispersion and properties .…”

“…Batch solid‐state processes such as pan milling and ball milling have been used to expose blends and hybrids to high forces and stresses, leading to improved dispersion and properties . Solid‐state shear pulverization (SSSP) is a continuous, industrially scalable solid‐state process that has been successful in producing well‐dispersed blends and composites that cannot be made easily or at all by melt processing . The SSSP process employs a twin‐screw extruder modified for cooling; amorphous materials are processed below their glass transition and semi‐crystalline materials below their melt transition.…”

“…Studies have also shown that SSSP can achieve excellent dispersion and exfoliation of commercial carbon‐based nanofillers, from carbon nanotubes to graphene and graphite . By taking advantage of the near ambient temperature conditions of SSSP, yet other studies have achieved maleic anhydride or ester functionalization of PP and PP branching without the large molecular weight reduction that accompanies such post‐polymerization modification during melt processing . Prior SSSP research has also led to unprecedented dispersion and property enhancements in the production of green polymer composites of polyolefins with a variety of bio‐based, renewable fillers, including rice husk ask, eggshells, and cellulose nanocrystals …”