Reactive Extrusion of Reeds (Phragmites australis) and production of binder-less foam insulator

Abstract

The construction and packaging industries are heavily dependent on petroleum-derived products such as polyurethane (PU) and polystyrene foams, as well as energy-intensive mineral and rock wool. Their low thermal conductivity, moisture resistance, long-term durability, low cost, and wide availability have made these materials difficult to substitute. However, in recent years, there has been growing demand for sustainable, renewable, and environmentally friendly alternatives to petroleum-derived products, driving considerable research and development in this area. Several natural materials, including wood fiber, hemp fiber, and rice and wheat straw fibrous panels, have been utilized for thermal insulation applications in the construction sector. These materials offer notable advantages such as low thermal conductivity, high porosity, and tuneable mechanical properties, alongside inherent biodegradability and a reduced carbon footprint. Nevertheless, significant challenges remain, particularly with respect to moisture resistance, thermal stability, and continued reliance on fossil-derived binders in their production. In the present work, binderless foams based on common reed (Phragmites australis) were produced using hydrothermally treated and reactive extrusion-processed reed fibers. The resulting foams demonstrated thermal conductivity comparable to that of PU and polystyrene foams, along with adjustable density. Moreover, the reed foams exhibited excellent dimensional stability under both water immersion and high humidity conditions. This work also provides a comprehensive characterization of the chemical composition of common reed before and after various treatments, as well as the process know-how required for binderless foam production.