Bio-polyurethane foam for fire retardant applications
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https://orcid.org/0000-0002-5984-3745
Haritha R Harshitha N Sripriya U
Abstract
Polyurethane (PU) is a material that finds applications in numerous sectors such as construction, automotive, furniture, additives, and so on. It has been forecasted that the global market for PUF will reach around 12.7 million tons by the year 2024, thus implying its high demand. Conventional polyurethane is synthesized using a mixture of polyols originating from fossil fuels and isocyanate. Wastes from Polyurethane Foam (PUF) are classified as white pollution, and they will have an impact on the living environment. At the same time, since the density of PUF is low, stockpiling will also take up a lot of space [1]. The pliable nature of PUF stems from a wide array of attributes that can be attained by tweaking the composition while manufacturing PUF. To control the quality of the foam, it is necessary to change the type and content of the isocyanate, polyol, catalyst, surfactant, blowing agent, and additive(s). In recent times the demand for green, sustainable, and non-toxic materials is rising due to environmental awareness and stricter policies. This resulted in the birth of Bio-PUF. In addition, the use of a fire-retardant additive can adversely affect the mechanical properties of the PUF. This necessitates the need for incorporating certain components into the rigid backbone of the PUF to counteract the adverse effects. Recent advances in this study include incorporating a phosphorus moiety to enhance the fire-retardant nature of Bio-PUF.
Broadly, the Bio-PUF production process can be segregated into three classes based on the reagents used. These reagents are vegetable oil, lignin, and non-isocyanate-based. Vegetable oils possess a high degree of unsaturation, which makes them suitable for synthesizing polyols. Lignin, an abundant biopolymer exhibit attributes including UV protection, flame retardancy, and hydrophobicity [2]. Non-iso-cyanate-based methods lead to the most environmentally friendly PUFs. Recent studies have depicted the use of dispersion technology [3] and carbon allotropes to increase the mechanical strength of Bio-PUF [4].
This review consolidates the research in the field of bio PUFs as depicted in figure 1 and identifies the gaps/challenges in the synthesis of Bio-PUFs. Also, the recent technologies, different applications, and environmental impact of Bio-PUF in comparison with the standard PUF are discussed.
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