Reprocessable\nPolyurethane Foams Using Acetoacetyl-Formed\nAmides

Abstract

Like any other thermosetting material,\npolyurethane foams (PUFs)\ncontain permanent cross-links that hinder their reprocessability and\nmake their recyclability a tedious and environmentally unfriendly\nprocess. Herein, we introduce acetoacetyl-formed amides, formed by\nthe reaction of isocyanates with acetoacetate groups, as dynamic units\nin the backbone of PUFs. By extensive variation of the foam composition,\noptimum parameters have been found to produce malleable foams above\ntemperatures of 130 °C, without the requirement of any solvent\nduring the foaming process. The PU cross-linked material can be compression-molded\nat least three times, giving rise to PU elastomers and thus maintaining\na cross-linked network structure. Characterization of the original\nfoams shows comparable properties to standard PUFs, for example, having\na density of 32 kg/m³, while they show similar chemical\nand thermal properties upon reprocessing to strong PU elastomers,\nexhibiting <i>T</i>_g ranging from −42\nto −48 °C. This research provides a straightforward method\nto produce thermally reprocessable PUFs as a promising pathway to\naddress the recycling issues of end-of-life foams.