Internal donors on supported Ziegler Natta catalysts for isotactic polypropylene: a brief tutorial review

Porous Organic Polymers-Supported Zeigler-Natta Catalysts for Preparing Highly Isotactic Polypropylene with Broad Molecular Weight Distribution

Porous organic polymers (POPs) have attracted much attention in numerous areas, including catalysis, adsorption and separation. Herein, POP supported Ziegler-Natta catalysts were designed for preparation of isotactic polypropylene (iPP). The POPs-based Ziegler-Natta catalysts exhibited the characteristic of broad molecular weight distribution (MWD > 11) with or without adding an extra internal electron donor. The added internal electron donor 3-methyl-5-tert-butyl-1,2-phenylene dibenzoate (ID-2) used in cat-2 showed good propylene polymerization activity of 15.3 × 10⁶ g·PP/mol·Ti·h, high stereoregularity with 98.2% of isotacticity index and broad molecular weight distribution (MWD) of 12.3. Compared to the MgCl₂-supported Ziegler-Natta catalysts (cat-4) with the same ID-2, cat-2 showed higher chain stereoregularity for propylene polymerization. As seen in the TREF results, the elution peak of PP-2 (124.0 °C, 91.7%) is 1.5 °C higher than the isotactic fraction from PP-4 (122.5 °C, 87.2%), and even 1.2 °C higher than PP-5 prepared from ID-3 with the characteristics of high stereoregularity. Moreover, the pentad methyl sequence mmmm of PP-2 (93.0%) from cat-2 is 0.5% higher than that of PP-4 from cat-4. XPS analysis revealed that the minute difference in binding energy of Ti, Mg, C and O atoms exist between the inorganic MgCl₂ and the organic polymer based Z-N catalysts. The plausible interaction mechanism of active sites of Mg and Ti with the functional groups in the POP support and the added ID was proposed, which could be explained by their high stereoregularity and the broad molecular weight distribution of the POP-based Z-N catalysts.

Identification and quantification of additive-derived chemicals in beached micro-mesoplastics and macroplastics

Although marine plastic debris are expected to retain various chemical additives, little is known about the additives that are retained. We conducted a screening analysis of additives in 261 macroplastic and micro-mesoplastic debris from two beaches. We detected 52 chemicals-antioxidants, phthalates, ultraviolet stabilizers, hindered amine light stabilizers, and flame retardants-and quantified the concentrations of 15 of them. Comparison of the concentrations of Irgafos 168, an antioxidant stabilizer, among sample categories indicated that leaching had occurred from micro-mesoplastics. Differences in diffusion rates between polymer types may explain faster leaching from polyethylene than polypropylene. The significant amounts of Irgafos 168 retained in even micro-mesoplastics indicated the importance of plastics as a vector of additives. This study provides fundamental data needed to assess the risks to organisms from exposure to plastic additives and to understand the effect of stabilizers on the aging behavior of marine plastics.