# Mechanochemical Recycling of Flexible Polyurethane Foam Scraps for Quantitative Replacement of Polyol Using Wedge-Block-Reinforced Extruder

## TL;DR

This paper presents a method to recycle flexible polyurethane foam scraps using a specialized extruder, enabling the replacement of polyol in new foam production.

## Contribution

A wedge-block-reinforced extruder is introduced to effectively recycle F-PUF scraps into reusable powder with functional hydroxyl groups.

## Key findings

- The extrusion process reduced the volume mean diameter of F-PUF powder to 54 μm after three extrusions.
- The -OH number of the powder reached 19.51 mgKOH/g due to the mechanochemical effect.
- Recycled powder replaced 10 wt.% polyol, producing foam with properties similar to original F-PUF.

## Abstract

Recycling flexible polyurethane foam (F-PUF) scraps is difficult due to the material’s high cross-linking structure. In this work, a wedge-block-reinforced extruder with a considerable enhanced shear extrusion and stretching area between the rotating screw and the stationary wedge blocks was utilized to recycle F-PUF scraps into powder containing surface-active hydroxyl groups. The powder was then utilized for the quantitative replacement of polyol in the foaming process. Characterizations showed that the continuous shear extrusion and stretching during the extrusion process reduced the volume mean diameter (VMD) of the F-PUF powder obtained by extruding it three times at room temperature to reach 54 μm. The -OH number (OHN) of the powder prepared by extruding it three times reached 19.51 mgKOH/g due to the mechanochemical effect of the powdering method. The F-PUF containing recycled powder used to quantitively replace 10 wt.% polyol was similar in microstructure and chemical structure to the original F-PUF, with a compression set of 2%, indentation load deflection of 21.3 lbf, resilience of 43.4%, air permeability of 815.7 L/m2·s, tensile strength of 73.0 Kpa, and tear strength of 2.3 N/cm, indicating that the recycling method has potential for industrial applications.