Upcycling detoxified asbestos cement as depolymerization regulating filler in polylactic acid (PLA) composites

Asbestos cement waste, a hazardous and challenging material to manage, can be deactivated and upcycled as a powder that can be safely used as polymer filler. With a standard twin screw extruder, we produced composite pellets with up to 50 wt% loading in PLA. They are sufficiently flowable and stable for further application to Fused Granular Fabrication 3D printing, an additive manufacturing method that employs pellets instead of filament. The filler dispersion is homogeneous, and the mechanical properties of the 3D printed samples are comparable to those of pure PLA up to 20 wt% loading. Depending on the preparation method, the deactivated asbestos can be fully inert or endowed with catalytic properties. A variant produced in a reducing environment has a strongly hydroxylated surface that can induce PLA chain scission and reorganization from 200 °C, significantly less than the 350 °C spontaneous degradation of the pristine polymer. This behaviour facilitates post-consumer biodegradation while preserving material integrity under standard processing conditions.