Flame Retardancy of Bio-Based Polyurethanes: Opportunities and Challenges

Abstract

Sustainable polymers are emerging fast and have received much more attention in recent years compared to petro-sourced polymers. However, they inherently have low-quality properties, such as poor mechanical properties, and inadequate performance, such as high flammability. In general, two methods have been considered to tackle such drawbacks: (i) reinforcement of sustainable polymers with additives; and (ii) modification of chemical structure by architectural manipulation so as to modify polymers for advanced applications. Development and management of bio-based polyurethanes with flame-retardant properties have been at the core of attention in recent years. Bio-based polyurethanes are currently prepared from renewable, bio-based sources such as vegetable oils. They are used in a wide range of applications including coatings and foams. However, they are highly flammable, and their further development is dependent on their flame retardancy. The aim of the present review is to investigate recent advances in the development of flame-retardant bio-based polyurethanes. Chemical structures of bio-based flame-retardant polyurethanes have been studied and explained from the point of view of flame retardancy. Moreover, various strategies for improving the flame retardancy of bio-based polyurethanes as well as reactive and additive flame-retardant solutions are discussed.

The Effects of Unbleached and Bleached Nanocellulose on the Thermal and Flammability of Polypropylene-Reinforced Kenaf Core Hybrid Polymer Bionanocomposites

“…Natural fibers are expected to act as combustion sources in composites. However, with the presence of coupling agent that helps to increase the bonding and promote a more uniform and homogenous blend of fibers in the polymer matrix, restricting the flow-ability of PP and reducing the dripping effect of the composites, fire retardancy of the samples could be improved [ 42 , 43 ]. According to Subasinghe, Das and Bhattacharyya [ 68 ], kenaf composites formed a more stable layer of char in a fully burnt state.…”

“…According to Chen et al [ 40 ], lignin has interesting properties, such as being renewable, non-toxic and biodegradable, which validate it into a value-added product. Furthermore, lignin could play a role as a dispersant to improve the dispersion of cellulose whiskers in the composite’s constituents [ 35 , 42 , 43 ]. Lignin can also withstand high-temperature degradation from 100 °C up to 900 °C, as lignin comprises aromatic rings with various branches, and the activity of chemical bond in lignin covered an extremely wide range [ 42 ].…”

“…Lignin can also withstand high-temperature degradation from 100 °C up to 900 °C, as lignin comprises aromatic rings with various branches, and the activity of chemical bond in lignin covered an extremely wide range [ 42 ]. In addition to other polymers such as bio-based polyurethane [ 43 ] and bio-epoxy [ 44 ] used as a flame retardant in composites, lignin was also seen as potential candidate for flame retardant materials. The aromatic chemical structure in lignin also stimulates the formation of a high char yield after decomposition, which can help protect the underlying substrate from further decomposition and improve flame retardancy [ 45 , 46 ].…”

Dielectric Responses of Polyurethane/Zinc Oxide Blends for Dry-Type Cast Cold-Curing Resin Transformers

“…Polyurethanes are one of the most versatile polymers that are on the reaction of a polyol with a diisocyanate or polymeric isocyanate textcolorbluebasis while using suitable catalysts and additives [ 31 , 32 , 33 ]. The versatility of this material predestines it for use in many areas.…”

The Prospering of Macromolecular Materials Based on Plant Oils within the Blooming Field of Polymers from Renewable Resources

“…In fact, the preparation of polyurethanes from vegetable oils is a subject that deserves attention, since its first report in the literature in the early 1990s [26], related to the preparation of polyurethane foams by mixing waste oil and polypropylene glycol with diphenylmethane diisocyanate, opened the way to hundreds of other publications belonging to the same field. Interesting and thorough monographs tackling the most relevant advances were recently published, calling upon aspects of synthesis, mechanical and thermal properties of polyurethanes from seed oil-based polyols [27], opportunities and challenges of bio-based polyurethanes with flame retardancy [28], as well as plant oil-based waterborne polyurethanes [8], viz. ionic and non-ionic polyurethane dispersions prepared in aqueous media.…”