Catalyst-Free Synthesis of Betulin-Based Polyurethane Elastomers with Outstanding Mechanical Properties and Solvent Resistance

Abstract

Using sustainable biomass feedstock to prepare biobased chemical products is attracting increasing attention. Betulin is a natural cyclic aliphatic diol that can be extracted in large quantities from the bark of birch trees. In this study, a series of biobased polyurethane (PU) elastomers with excellent mechanical properties, solvent resistance, and thermal stability were synthesized under catalyst-free conditions using betulin and castor oil (CO) as the bio-based polyols. The chemical structure and properties of the bio-based PU elastomers were systematically investigated according to the effect of the hydroxyl ratio between betulin and CO. Due to the presence of abundant hydrogen bonds and rigid ring planes in the PU structure, and a higher cross-link density, the obtained PU elastomers had excellent mechanical properties. They achieved a maximum tensile strength of 31.6 MPa with the tensile strain reaching more than 200% and were able to withstand 1 × 10 5 times their weight. The thermal decomposition temperature of the betulin-derived PUs was over 300 °C. This study showcased a strategy to synthesize sustainable high-performance PU materials with a high biomass content (>75%).

Lightweight Biobased Polyurethane Composites Derived from Liquefied Polyol Reinforced by Biomass Sources with High Mechanical Property and Enhanced Fire-Resistance Performance

“…One currently recommended program, such as Net Zero Emissions, aims to reduce its environmental impact by 45% by 2030 and reach net zero by 2050 . One of the strategies to meet today’s needs is the development of biobased insulation materials, which reduce environmental impact while maintaining thermal insulation performance. − As for PU, to meet environmental regulations, there have been a lot of approaches to synthesizing bio-PU and biocomposite based on PU from biomass sources to partially or completely replace petroleum-based polyurethane. , In fact, biomass, serving as a renewable raw material, such as bamboo shoot shell or bagasse flour, has been utilized for synthesizing biopolyol for several years and their environmental benefits have been acknowledged. , The ratio of biopolyol was also optimized to be able to utilize as much of the biopolyol content in the bio-PU while preserving the properties of this material. Up to now, biocomposites based on PU matrix with fillers derived from biomass have been studied. − The biomass content was optimized so that it could be incorporated into the composites as much as possible while still retaining the properties of the composites.…”

“… 3 − 6 As for PU, to meet environmental regulations, there have been a lot of approaches to synthesizing bio-PU and biocomposite based on PU from biomass sources to partially or completely replace petroleum-based polyurethane. 7 , 8 In fact, biomass, serving as a renewable raw material, such as bamboo shoot shell or bagasse flour, has been utilized for synthesizing biopolyol for several years and their environmental benefits have been acknowledged. 9 , 10 The ratio of biopolyol was also optimized to be able to utilize as much of the biopolyol content in the bio-PU while preserving the properties of this material.…”