Lignin-based rigid polyurethane foams with improved biodegradation

Abstract

Rigid polyurethane (RPU) foams have been synthesized using lignin-based polyols obtained by oxypropylation of four distinct lignins (Alcell, Indulin AT, Curan 27-11P, and Sarkanda). Polyol formulations with two lignin/propylene oxide/catalyst content (L/PO/C) ratios were chosen (30/70/2 and 20/80/5). RPU foams have been prepared with a polyol component that incorporates the lignin-based one at contents ranging from 25 to 100%. A 100% commercial polyol-based (Lupranol® 3323) RPU foam was also prepared and used as the reference. RPU foams were characterized in terms of density, compressive modulus, and conductivity. Cell morphology and size estimation were accessed by scanning electron microscopy. Moreover, biodegradation of the Alcell- and Indulin AT-based foams was evaluated using respirometry tests in liquid and solid media. The Alcell- and Indulin AT-based polyols together with the 20/80/5 Curan 27-11P-based one led to RPU foams with properties quite similar to those of the reference homolog. Biodegradation seems to be, particularly, favored if using Indulin AT-based polyols mixed with Lupranol® 3323.

Characterization of Biobased Polyurethane Foams Employing Lignin Fractionated from Microwave Liquefied Switchgrass

“…The apparent density for the foam with 10% lignin was the highest, increased by 14.2% relative to the control foam, while the foam with 15% lignin showed the lowest density of 0.047 g/cm −3 , which was 12.8% lower than the control foam. In general, for foams with similar cell wall thickness, density is known to decrease as cell size increases, which further influence mechanical properties [32]. Therefore, the low density for the 15% lignin foam is due to its large cell size as evidenced by the SEM image (Figure 1(d)).…”

Sustainable allylation of organosolv lignin with diallyl carbonate and detailed structural characterization of modified lignin

“…3,6,7 On the other hand, the macromolecular structure of lignin can be used for the preparation of polymeric materials. Herein, many possible applications are proposed in the literature; for instance, the use of lignin as polyol for polyurethanes 8,9,10 or as phenol substitute in phenolic resins. 11,12 Furthermore, lignin can be used in blends to increase mechanical stability or biodegradability.…”

Synthesis and characterization of bio-polyols through the oxypropylation of bark and alkaline extracts of bark

“…The combination of a higher molecular weight, less degradation, and a higher bark fraction due to a higher biomass conversion yield, have all led to a polyurethane network that was superior to that made from a liquefied bark-based polyol. Furthermore, the oxypropylated bark showed improved mechanical properties over oxypropylated lignin PUFs with the highest reported elastic modulus of 3.41 MPa (Cateto et al, 2014); oxypropylated kraft lignin PUFs with a highest reported strength value of 140 kPa and modulus of 3.41 MPa (Li and Ragauskas, 2012); and a lower modulus, but comparable strength to PUFs made from oxypropylated organo-solv lignin (Arshanitsa et al, 2013). The oxypropylated bark PUF however had a lower elastic modulus and strength than foams made from liquefied starch that was then oxypropylated (Yoshioka et al, 2013).…”