Recent Developments in Biobased Foams and Foam Composites for Construction Applications

Abstract

A surge of research into renewable foams has yielded an array of high‐performance polymeric materials, many of which exhibit promising properties for next generation thermal insulating materials. Biobased materials are of particular interest, due to growing concerns towards enhancing the circular economy while reducing fossil fuel dependency in the construction industry. This review outlines recent developments in biobased foams based on biobased polyurethanes (BPU), biobased phenol formaldehyde (BPF) and cellulose nanofibers (CNF) foams. These three areas of polymers are of particular interest due to their early stage of market adoption, yet significant industrial potential. As our focus is on construction materials, we will review their thermal, mechanical, and fire‐retardant performance, their synthesis/fabrication methods and future prospects. Improving the scalability, reproducibility and cost‐effectiveness of their production is vital for successful commercialization adoption.

Investigating the hydrophilicity of phenol formaldehyde foams: Effects of synthesis parameters

“…Phenolic resins can be synthesized under strong acidic or basic conditions. 5 Novolak resins are prepared under strong acidic conditions and with a formaldehyde to phenol molar ratio (F/P ratio) lower than 1.0. On the other hand, when the resins are manufactured under alkaline conditions at a F/P ratio greater than 1.0, they are called resoles.…”

“…are preferred due to their participation in the curing process with phenolic pre-polymers, resulting in a reduction in the overall acidity of phenolic foams. 5 Inorganic catalysts (such as hydrochloric acid, phosphoric acid and sulfuric acid) should however be avoided to a large extent due to their corrosion issues, and to reduce a further step of post-treating the foams with neutralizing gas such as ammonia. 9 Surfactant is used to regulate the foam structure and pore sizes in the foam production process by lowering the surface tension between polar surfaces of the resole resin and non-polar blowing agent to facilitate mixing until gelation of the resin occurs.…”

“…9 Surfactant is used to regulate the foam structure and pore sizes in the foam production process by lowering the surface tension between polar surfaces of the resole resin and non-polar blowing agent to facilitate mixing until gelation of the resin occurs. 5,10 Among the surfactants commonly employed in phenolic foam synthesis are Tween 40, Tween 60, Tween 80, DC-193 (silicone surfactant) and copolymers of siloxane-oxyalkylene. 11 While the majority of studies utilized a single surfactant in their foam composition, Hu et al (2016) observed that the simultaneous use of DC-193 and Tween-80 resulted in improved cell uniformity, compressive strength, and the quantity of closed cells.…”