Abstract
Currently, most commercial polyols used in the production of polyurethane (PU) foam are derived from petrochemicals. To address concerns relating to environmental pollution, a sustainable resource, namely, castor oil (CO), was used in this study. To improve the production efficiency, sustainability, and compressive strength of PU foam, which is widely used as an impact-absorbing material for protective equipment, PU foam was synthesized with CO-based multifunctional polyols. CO-based polyols with high functionalities were synthesized via a facile thiol-ene click reaction method and their chemical structures were analyzed. Subsequently, a series of polyol blends of castor oil and two kinds of castor oil-based polyols with different hydroxyl values was prepared and the viscosity of the blends was analyzed. Polyurethane foams were fabricated from the polyol blends via a free-rising method. The effects of the composition of the polyol blends on the structural, morphological, mechanical, and thermal properties of the polyurethane foams were investigated. The results demonstrated that the fabrication of polyurethane foams from multifunctional polyol blends is an effective way to improve their compressive properties. We expect these findings to widen the range of applications of bio-based polyurethane foams.
Highlights
Most commercial polyols are derived from petrochemicals; concerns about environmental pollution and regulations have led to an interest in using sustainable resources to replace petroleum-based polyols [8]
The structural, morphological, thermal, and mechanical properties of the resultant PU foams were characterized via Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), the universal testing machine (UTM), and thermogravimetric analysis (TGA)
castor oil (CO)-based multifunctional polyols were synthesized via a facile thiol-ene click reaction
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The successful commercialization of PU produced from CO is limited by the poor mechanical properties of the foam and low productivity, which are attributed to the inherent characteristics of CO, such as low hydroxyl value, low reactivity of secondary OH groups, and steric hindrance [26]. The thiol-ene click reaction has been attracting considerable attention as a facile and efficient method for producing multifunctional materials [30]. Alagi et al developed thiol-grafted vegetable oil-based polyols and utilized them to prepare thermoplastic PUs [31]. We have reported sustainable polyols with gradually increasing functionalities via the thiol-ene click reaction with castor oil [26]. Only a few researchers have reported the fabrication of PU foams from multifunctional polyols prepared via thiol-ene click reactions. Two types of CO-based polyols with different functionalities are prepared using a facile thiol-ene click reaction method. The structural, morphological, thermal, and mechanical properties of the resultant PU foams were characterized via FT-IR spectroscopy, scanning electron microscopy (SEM), the universal testing machine (UTM), and thermogravimetric analysis (TGA)
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