Influence of ball milling parameters on the mechano-chemical conversion of polyolefins.

Ball-milling of addition polymers such as polyolefins, polystyrene and polyacrylates can be used for depolymerization to obtain the respective monomers. However, absolute yields are typically low, especially from polyolefins which are notoriously difficult to depolymerize. To increase the viability of ball milling as a recycling technique, the effect of milling parameters on small hydrocarbon and monomer yields has to be understood.

Thermodynamic limits of the depolymerization of poly(olefin)s using mechanochemistry.

Mechanochemistry is a promising approach for chemical recycling of commodity plastics, and in some cases depolymerization to the monomer(s) has been reported. However, while poly(olefin)s comprise the largest share of global commodity plastics, mechanochemical depolymerization of these polymers in standard laboratory-scale ball mill reactors suffers from slow rates. In this work, the observed reactivities of poly(styrene), poly(ethylene) and poly(propylene) are rationalized on the basis of thermodynamic limitations of their depolymerization by depropagation of free radical intermediates.

Catalytic Pyrolysis of Polyethylene with Microporous and Mesoporous Materials: Assessing Performance and Mechanistic Understanding.

Testing the catalytic performance for the catalytic pyrolysis of plastic waste is hampered by mass transfer limitations induced by a size mismatch between the catalyst's pores and the bulky polymer molecules. To investigate this aspect, the catalytic behaviour of a series of microporous and mesoporous materials was assessed in the catalytic pyrolysis of polyethylene (PE). More specifically, a mesoporous material, namely sulfated zirconia (Zr(SO)) on SBA-15, was synthesized to increase the pore accessibility, which reduces mass transfer limitations and thereby enables to better assess the effect of active site density on catalyst activity.

Surface-Activated Mechano-Catalysis for Ambient Conversion of Plastic Waste.

Improved recycling technologies can offer sustainable end-of-life options for plastic waste. While polyolefins can be converted into small hydrocarbons over acid catalysts at high temperatures, we demonstrate an alternative mechano-catalytic strategy at ambient conditions. The mechanism is fundamentally different from classical acidity-driven high-temperature approaches, exploiting mechanochemically generated radical intermediates.

Conventional and Contrast-enhanced US of the Lung: From Performance to Diagnosis.

In recent years, lung US has evolved from a marginal tool to an integral component of diagnostic chest imaging. Contrast-enhanced US (CEUS) can improve routine gray-scale imaging of the lung and chest, particularly in diagnosis of peripheral lung diseases (PLDs). Although an underused tool in many centers, and despite inherent limitations in evaluation of central lung disease caused by high acoustic impedance between air and soft tissues, lung CEUS has emerged as a valuable tool in diagnosis of PLDs.