Recent Progress of Non-Isocyanate Polyurethane Foam and Their Challenges

Abstract

Polyurethane foams (PUFs) are a significant group of polymeric foam materials. Thanks to their outstanding mechanical, chemical, and physical properties, they are implemented successfully in a wide range of applications. Conventionally, PUFs are obtained in polyaddition reactions between polyols, diisoycyanate, and water to get a CO2 foaming agent. The toxicity of isocyanate has attracted considerable attention from both scientists and industry professionals to explore cleaner synthesis routes for polyurethanes excluding the use of isocyanate. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines in the presence of an external blowing agent or by self-blowing appears to be the most promising route to substitute the conventional PUFs process and to produce isocyanate-free polyurethane foams (NIPUFs). Especially for polyhydroxyurethane foams (PHUFs), the use of a blowing agent is essential to regenerate the gas responsible for the creation of the cells that are the basis of the foam. In this review, we report on the use of different blowing agents, such as Poly(methylhydrogensiloxane) (PHMS) and liquid fluorohydrocarbons for the preparation of NIPUFs. Furthermore, the preparation of NIPUFs using the self-blowing technique to produce gas without external blowing agents is assessed. Finally, various biologically derived NIPUFs are presented, including self-blown NIPUFs and NIPUFs with an external blowing agent.

CO2-derived non-isocyanate polyurethanes (NIPUs) and their potential applications

“…However, the conventional method that involves the production of NIPU from bicyclic carbonate and polyamine does not naturally produce foaming agents. 70 Researchers recently used a new blowing agent to make high-density NIPU foams with large interconnected cells. 71 Common blowing agents can worsen fire behavior, so there is interest in using nonflammable alternatives.…”

Self-Blowing Non-isocyanate Polyurethane Foams from Cyclic Carbonate Linseed Oil

“…Polyurethane (PU) foams have been widely applied in various industries such as building thermal insulation, packaging, and comfort items (matresses, seats, pillows, ...) and so on due to their excellent thermal insulating properties, light weight, excellent mechanical properties and low costs . It is reported that about 60% of the PU products are used to produce PU foams and the production of PU foams is expected to grow from 42.8 billion US dollars in 2021 to 61.5 billion US dollars by 2026. , However, the traditional PU foams are generally synthesized by utilizing the rapid reaction of water and isocyanate to release CO 2 as the blowing agent associated with simultaneous formation of urethane blocking units through reaction between polyols and isocyanate. − The application of toxic isocyanate in the synthesis of PU foams has led to increasing health and environmental concerns as well as regulatory scrutiny, which has driven the industry and academic circles to develop non-isocyanate polyurethane (NIPU) foams …”

Low-Isocyanate Polyurethane Foams with Improved Stability and Compression Modulus Prepared from Biosourced and Landfill-Diverted Materials

“…Reducing isocyanate concentrations in foam formulations increases safety and lowers cost. Isocyanates are toxic chemicals that irritate mucous membranes, resulting in severe and chronic asthma symptoms in individuals who have prolonged exposure, in some cases resulting in death. , However, the current isocyanate alternatives cannot fully meet the requirements for industrial free-rise foams and it is not possible to completely eliminate the use of isocyanate altogether. − Therefore, it is important to explore methods for reducing the amount of isocyanates used in foam production which can be immediately implemented in industry, while isocyanate replacement research is ongoing.…”