Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and thermal conductivity combined with their interesting mechanical properties make them excellent thermal and sound insulators, as well as structural and comfort materials. Despite the broad range of applications, the production of PUFs is still highly petroleum-dependent, so this industry must adapt to ever more strict regulations and rigorous consumers. In that sense, the well-established raw materials and process technologies can face a turning point in the near future, due to the need of using renewable raw materials and new process technologies, such as three-dimensional (3D) printing. In this work, the fundamental aspects of the production of PUFs are reviewed, the new challenges that the PUFs industry are expected to confront regarding process methodologies in the near future are outlined, and some alternatives are also presented. Then, the strategies for the improvement of PUFs sustainability, including recycling, and the enhancement of their properties are discussed.

https://www.mdpi.com/1996-1944/11/10/1841/pdf/1

Polyurethane Foams: Past, Present, and Future

Polyurethanes (PUs), produced from the condensation polymerizations between polyols and isocyanates, are one of the most versatile polymer families. Currently, both polyols and isocyanates are largely petroleum derived. Recently, there have been extensive research interests in developing bio-based polyols and PUs from renewable resources. As the world's most abundant renewable biomass, lignocellulosic biomass is rich in hydroxyl groups and has potential as a feedstock to produce bio-based polyols and PUs. Lignocellulosic biomass can be converted to liquid polyols for PU applications through acid- or base-catalyzed atmospheric liquefaction processes using polyhydric alcohols as liquefaction solvents. Biomass liquefaction-derived polyols can be used to prepare various PU products, such as foams, films and adhesives. The properties of biomass liquefaction-derived polyols and PUs depend on various factors, such as feedstock characteristics, liquefaction conditions, and PU formulations.

Polyols and polyurethanes from the liquefaction of lignocellulosic biomass.

Preparation and characterization of rigid polyurethane foam prepared from sugar-cane bagasse polyol

Bio-based polyurethane foams toward applications beyond thermal insulation

Polyurethane foams based on modified tung oil and reinforced with rice husk ash I: Synthesis and physical chemical characterization

Sugar-cane bagasse was liquefied in ethylene glycol/phthalic anhydride mixture catalyzed by sulphuric acid at temperatures 160-220°C, liquefaction times 60-240 minutes, and ethylene glycol amounts 5-20 ml for each three grams of sugar-cane bagasse. The residue obtained was characterized by FT-IR, X-ray diffraction, and scanning electron microscope. The percentages of residue, average molecular weight, hydroxyl and acid numbers were determined as an estimate of polyol value of the liquid products. Optimal conditions for liquefaction were established: reaction temperature 160°C, reaction time 180 minutes, and ethylene glycol amount 20 ml/three grams sugar-cane bagasse.

Aisha Emam

Papers

Preparation and characterization of rigid polyurethane foam prepared from sugar-cane bagasse polyol

Optimization and characterization of sugar-cane bagasse liquefaction process