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Development of rigid polyurethane foam from kraft lignin and renewable source chain extenders: application as a thermal insulator


The appreciation of Kraft lignin, through its conversion into products with high added value, has been motivated and investigated in technological research centers, universities and industries. It is estimated that tens millions tons of Kraft lignin are generated annually as a by-product from pulp and paper manufacturing. Aiming to raise its value, a Kraft lignin industrial plant was launched by Suzano Papel e Celulose company in Limeira, with production planning of 20,000 tons and production capacity of 80,000 tons per year. In addition, Klabin company announced the installation of a pilot plant for technological lignin development in 2019, reinforcing the interest in lignin reuse and business opportunities generation. Besides the large-scale availability, the functional groups present in the lignin structure (aromatic and aliphatic hydroxyls, carbonyl) make it an interesting raw material alternative for the development of polymers, such as polyurethanes (PU), phenolic resins and epoxies. The development of rigid PU foams from lignin is favored by the presence of aromatic rings in the lignin structure. The results of Phase 1 of this project pointed solutions to main difficulties involved in this development: the low reactivity of its aromatic hydroxyls and its reduced solubility in polyol. In this context, this work aims to develop rigid polyurethane foams from modified lignin and modified castor oil. The modification routes investigated in Phase 1 will be improved and mixtures of modified lignin with modified castor oil will be obtained to optimize the PUs properties. The characterization of these polyols will be conducted by Fourier transform infrared spectroscopy (FTIR), rotational viscosimetry, titration for hydroxyl level determination and temperature modulated optical refractometry (TMOR). Several rigid PU foams formulations will be developed from these mixtures, varying the ratio of their ingredients and additives. Compressive strength, dimensional stability, thermal conductivity analysis, bulk density and scanning electron microscopy (MEV) will be carried out in foams characterization ensuring that rigid foam is obtained within the required performance levels as thermal insulators. The flame retardant properties of foams will also be investigated, as it represents an important differential evidenced during Phase 1 by several companies visited. The PUs cure kinetics will be investigated by TMOR and FTIR. The rigid polyurethane foam market is the second largest in sales in the world. Its development implies the appreciation and transformation of a large-scale industrial waste into cost-effective, flame-retardant rigid foam, indirect jobs generation and the establishment of a new company developing sustainable technological products. (AU)