Lignin-Based Foaming Materials

Lignin-Based Polyurethanes: Opportunities for Bio-Based Foams, Elastomers, Coatings and Adhesives

“…Higher incorporation of unmodified lignin over 30 wt % has been reported to result in brittle foams with decreased compression strength [24,87,88]. This is due to the poor cellular structure [88,89] of lignin-based rigid PU foam along with the aromatic structure of lignin which increases the ratio of hard segments creating a brittle and friable foams [90,91]. This problem has been addressed through the addition of chain extenders like castor oil [92], polypropylene glycol triol [92], and butanediol [93].…”

“…This problem has been addressed through the addition of chain extenders like castor oil [92], polypropylene glycol triol [92], and butanediol [93]. Elongation at break and compression strength are some of the properties that have been reported to increase with the addition of chain extenders due to increased flexibility they impart [90,92,93]. The main challenges in incorporating higher proportions of lignin in polyurethane foams are increasing viscosity [56], [94] and density [95], while decreasing curing/reaction times [70], and in some cases, unpleasant odor usually associated with kraft softwood lignins [96].…”

Lignin modifications and perspectives towards applications of phenolic foams: A Review

“…(Gardiziella et al 2015). In addition to their use as adhesives, PF resins are the basic component of low-density PF foams that have a low thermal conductivity and high service temperature (Obaid et al 2016). Synthesis begins when phenol and formaldehyde are mixed in a solution at a low pressure and high temperature.…”

“…However, few reviews were found concerning the application of lignin in phenolic foams. The only work related to the topic is by Obaid et al (2016), which is a book on lignin-based foaming materials. However, the authors did not do a comprehensive review on the topic.…”

Introductory Chapter: Introduction to Structure Properties and Application of Lignin

“…Foaming in polymers is introduced by blowing air or chemicals between the polymer matrixes. Here, the lignin has found its importance due to polyhydroxyl groups present in it, as it can substitute natural polyols in polyurethane [22]. Resins are the another important sector where lignin has been found replacing phenol in phenol-formaldehyde resins [23].Considering the tremendous properties of lignin, it has been an interest of researchers to find out its biomedical and pharma applications in form of hydrogels, aerogels, and sensors.…”