Exploitation of Arundo donax L. Hydrolysis Residue for the Green Synthesis of Flexible Polyurethane Foams

Abstract

Flexible polyurethane foams were prepared from solid waste residue derived from the hydrothermal acid treatment of the Arundo donax L. herbaceous biomass, which produced a very high yield of levulinic acid. An innovative, sustainable, and green liquefaction route was adopted to produce lignin-based flexible polyurethane foams by partially replacing fossil-fuel source polyols with an abundant and renewable hydroxyl source, the Arundo donax L. "lignin-like" residue. Lignin liquefaction was performed in polyolic solvents using microwave irradiation, saving time and energy while ensuring a more sustainable and green approach. Foam production was performed with controlled expansion using the "one-shot" technique. Water was adopted as the only blowing agent, and the isocyanate index (NCO/OH) was kept to less than 100, which reduced the cross-linking degree of the desired foam and increased its flexibility. About 7 wt.% of the conventional petrochemical polyether polyol was replaced with the Arundo donax L. hydrolysis residue. The chemical and mechanical properties of the synthesized foams were compared with those obtained by using a pure technical soda lignin, ProtoBind 1000. The results were characterized by satisfactory mechanical properties, thus closing the biorefinery cycle of Arundo donax L. exploitation.

Filler-Modified Castor Oil-Based Polyurethane Foam for the Removal of Aqueous Heavy Metals Detected Using Laser-Induced Breakdown Spectroscopy (LIBS) Technique

“…The presence of a hard segment in the PU-urea system can be identified by the first two stages of thermal degradation (W 1-2 ) at 270-414 • C, which are comparable with the previous reports [17,18,35]. The urea linkage originated from a further reaction of isocyanate and amine, resulting from isocyanate and water reaction [19]. The following two decomposition stages, at 414-533 • C, are respectively attributed to the castor oil chain scission (W 3 ) and the breakdown of the C-C bonds (W 4 ).…”

“…Led by the rise of environmental concern, a new trend in PU research has been shifted to the use of bio-polyol resources. Lignin, starch, cellulose, chitosan, and vegetable oils (including castor oil) are some examples of many bio-polyols that have been used by researchers in PU synthesis for multiple applications in either pharmacy, building construction, packaging, agriculture, or other fields [16][17][18][19][20][21].…”

“…Due to its easy shape-tailoring, the addition of water into the polyol and diisocyanate mixture is enough to get the polyurethane foam (PUF) [22]. This material can appear in an open or closed cell structure with a wide range of rigidity (rigid, semirigid, and flexible foam) [19]. Hence, PUF has been noticeable for its high applicability as a thermal insulator [16], adhesive [17], and fertilizer release controller [21], and many others.…”

Optimization of the Production Factors of Boards Obtained from Arundo donax L. Fibers without Added Adhesives

“…The hydrolysis of Arundo donax L. L. has also been considered for the synthesis of flexible polyurethane foams [20]. Hydrolyzed A. donax has been used for the production of organic acids of a biological basis as an ecological alternative to petroleum products [21].…”

Variation of Mechanical Characteristics of Polyurethane Foam: Effect of Test Method

“…[6]. Soft segments, in contrast, exist as a rubber phase at room temperature because of the glass transition temperature (Tg) being 30–50 °C [7]. However, in an extremely cold environment much lower in temperature than Tg, the segment undergoes brittle crystallization through phase change, resulting in a complex nature with stiffness to support the load [8].…”