Abstract
Valorization of industrial low-value side-streams are of great interest, contributing to boosts in the circular economy. In this context, lignin side-streams of the pulp and paper industry were oxypropylated to produce biobased polyols and tested in the synthesis of rigid polyurethane (RPU) foams. E. globulus lignins, namely a lignin isolated from an industrial Kraft black liquor and depolymerized lignins obtained as by-products of an oxidation process, were used. RPU foams, synthesized with 100% lignin-based polyols and using a 1.1 NCO/OH ratio, were characterized concerning apparent density, morphology, thermal conductivity, thermal stability, and heat release rate (HRR). Foams containing the lignin-based polyols presented densities varying from 44.7 to 112.2 kg/m3 and thermal conductivity in the range of 37.2–49.0 mW/mK. For the reference foam (sample produced with 100% wt. Daltofoam TP 32015 polyol), values of 70.9 kg/m3 and 41.1 mW/mK were obtained, respectively. The achieved results point out the viability of using the generated lignin-based polyols at 100% content in RPU foams, mainly when depolymerized lignins are used. Moreover, fire retardancy was favored when the lignin-based polyols were introduced. The proposed strategies can contribute to establishing the integrated pulp and paper biorefinery concept where material synthesis (polyols and RPU foams) can be combined with chemical production (vanillin and syringaldehyde).
Highlights
Global policies are presently directing the chemical industry towards sustainable strategies, promoting the transition to greener raw materials based on the circular economy principles and the sustainability triangle built on economic, environmental, and social pillars
All the produced lignin-based polyols were characterized for their technical properties, IOH, and viscosity, having in view their suitability for the application as a monomer for rigid polyurethane (RPU) foam synthesis (IOH between 300 and 800 and a viscosity below 300 Pa·s) [16]
The present study was focused on the synthesis of lignin-based polyols through oxypropylation
Summary
Global policies are presently directing the chemical industry towards sustainable strategies, promoting the transition to greener raw materials based on the circular economy principles and the sustainability triangle built on economic, environmental, and social pillars. An appropriated approach should consider the analysis of stakeholders’ individual responses, together with their influence on the overall performance of the system [4] This approach must be based on an appellative strategy, aiming at enhancing stakeholders’ knowledge on the general socio-economic and environmental benefits of a biorefinery structure, increasing their interest and recognition [5]. In this perspective, lignin valorization can contribute to the implementation of the pulp and paper biorefinery concept, highlighting the relevance of carrying out this study
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