Crystallization of Isotactic Polypropylene Nanocomposites with Fibrillated Poly(tetrafluoroethylene) under Elevated Pressure

Nanocomposites of isotactic polypropylene with 1–5 wt.% of fibrillated PTFE (PP/T) were prepared, and their crystallization during cooling under elevated pressure, in a wide pressure range, up to 300 MPa, as well as the resulting structure, were examined. The crystallization peak temperatures of PP/T, especially with 3 and 5 wt.% of PTFE, exceeded by up to 13 °C those of neat PP. Moreover, a fine-grain structure was formed in PP/T in the entire pressure range, which proved the ability of the fibrillated PTFE to nucleate crystallization of PP in the γ-form under elevated pressure. This also resulted in a higher crystallinity level developed in the γ-domain, before the temperature range of the α-domain was reached during cooling. Hence, the γ-content increased in comparison to that in neat PP, under the pressure up to 200 MPa, especially under 50–100 MPa.

Facile Polyolefin Plastics Hydrogenolysis Catalyzed by a Surface Electrophilic d0 Hydride

Polyolefins comprise a major fraction of single-use plastics and yet their catalytic deconstruction/recycling has proven challenging due to their inert hydrocarbon connectivities. Here an electrophilic earth-abundant single-site organozirconium catalyst chemisorbed on a highly Brønsted acidic support and characterized by a broad array of experimental and theoretical techniques, is shown to mediate the rapid hydrogenolytic cleavage of molecular and macromolecular saturated hydrocarbons under mild conditions. For n-hexadecane, hydrogenolysis to light hydrocarbons proceeds with an activity of 690 mol n-hexadecane · mol Zr-1 · h-1 at 150°C/2.5 atm H2 pressure. Under similar solventless conditions, polyethylene, polyethylene-co- 1-octene, isotactic polypropylene, and a post-consumer sandwich bag are rapidly hydrogenolyzed to low molecular mass hydrocarbons via a turnover-limiting C-C scission pathway involving ßalkyl transfer rather than more common σ-bond metathesis.