Lignin-Based Polyurethanes from the Blocked Isocyanate Approach: Synthesis and Characterization

Autor(es)

Antonino, Leonardo D. ; Sumerskii, Ivan ; Potthast, Antje ; Rosenau, Thomas ; Felisberti, Maria Isabel ; dos Santos, Demetrio J.

• Tipo de documento: Artigo Científico
• Fonte: ACS OMEGA; v. 8, n. 30, p. 13-pg., 2023-07-18.

Resumo

Lignin, the world's second most abundant biopolymer,hasbeen investigated as a precursor of polyurethanes due to its highavailability and large amount of hydroxyls present in its structure.Lignin-based polyurethanes (LPUs) are usually synthesized from thereaction between lignin, previously modified or not, and diisocyanates.In the present work, LPUs were prepared, for the first time, usingthe blocked isocyanate approach. For that, unmodified and hydroxypropylatedKraft lignins were reacted with 4,4 & PRIME;-methylene diphenyl diisocyanatein the presence of diisopropylamine (blocking agent). Castor oil wasemployed as a second polyol. The chemical modification was confirmedby P-31 nuclear magnetic resonance (P-31 NMR)analysis, and the structure of both lignins was elucidated by a bidimensionalNMR technique. The LPUs' prepolymerization kinetics was investigatedby temperature-modulated optical refractometry and Fourier-transforminfrared spectroscopy. The positive effect of hydroxypropylation onthe reactivity of the Kraft lignin was verified. The structure ofLPU prepolymers was accessed by bidimensional NMR. The formation ofhindered urea-terminated LPU prepolymers was confirmed. From the results,the feasibility of the blocked isocyanate approach to obtain LPUswas proven. Lastly, single-lap shear tests were performed and revealedthe potential of LPU prepolymers as monocomponent adhesives. (AU)

• Processo FAPESP: 19/05460-6 - Adesivo poliuretano termoativado baseado em lignina kraft modificada
• Beneficiário: Leonardo Dalseno Antonino
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto