Extrusion foaming behavior of polybutene-1. Toward single-material multifunctional sandwich structures

Abstract

Polymeric foams are a key element of many multifunctional sandwich structures. The most commonly used polymeric foam, polyurethane, presents environmental drawbacks, related to poor recyclability and the use of toxic diisocyanates for their manufacturing. The separation of layers in sandwich structures is a further unresolved hurdle toward the recyclability of these elements. There is a need for broadening the spectrum of polymeric foams. In this context, the foamability of polybutene-1 (PB-1) is studied through extrusion foaming experiments. From the application side, foaming PB-1 would allow the manufacturing of district heating pre-insulated pipes out of one single material, bringing circular product design to the energy sector. From the scientific side, there is a knowledge gap in the foaming of polymers in the rubbery state at room temperature, such as PB-1, due to difficulties in the cell stabilization step. This supports the need for research in the foaming of this polymer. In this study, four commercial grades of PB-1 were evaluated, covering different chain structures, molecular weights, and crystallinity degrees. Very different foaming behaviors were found. Dimensionally stable foams were achieved with the two homopolymers tested, demonstrating the foamability of this polymer.