Waste to Resource: Synthesis of Polyurethanes from Waste Cooking Oil

Abstract

Waste cooking oil (WCO) is generated after frying or cooking food with vegetable oils. It can be obtained from domestic sources, fast-food places, and industries. The continuous reuse of WCO in foods poses serious health problems, and the improper disposal of WCO results in environmental pollution. Hence, scientists are searching for ways to convert WCO into a useful secondary raw material to produce energy or value-added products. Also, the large generation of WCO is an environmental hurdle, hence finding sustainable ways to reuse it can lead to an advantageous process. Under this perspective, our group collected and filtrated WCO from a domestic source after a one-time use in the deep frying of fish. The qualitative analysis based on iodine, acid value, Fourier transform infrared along with other tests showed that the WCO presented negligible differences when compared to the pure cooking oil. After that, the WCO was converted into a polyol through an epoxidation/ring-opening reaction. The synthesis yielded the WCO-polyol which presented a suitable hydroxyl number that enabled it to form rigid polyurethane foams (RPUFs) with competitive properties. In addition to that, our group introduced flame retardancy properties through the blending of dimethyl methylphosphonate (DMMP) or expandable graphite (EG) under increasing concentrations. Through that, several analyses were conducted to elucidate the properties of the WCO-based RPUF. Within this line, the majority of the RPUF presented a closed cell content greater than 90%. Also, a considerable improvement in flame retardancy was observed as the neat WCO-based RPUF had a burning time of 93 s and a weight loss of 46%. Yet, the addition of 10.73 wt % DMMP (DMMP-7) reduced to 8.5 s and 3%, respectively. Also, 16.69 wt % EG (EG-10) resulted in a decrease to 12.5 s and 5%, respectively. Overall, most of the properties of the foams were not compromised with the use of WCO-polyol. Hence, our research was successful in the production of biobased RPUFs. Additionally, further investigations can be performed to potentially improve the properties of the produced WCO foams which can be likely used on the commercial scale for consumer and income generation needs.

Development of High-Performance Coconut Oil-Based Rigid Polyurethane-Urea Foam: A Novel Sequential Amidation and Prepolymerization Process

“…The most important characteristic bands are located at 2000–1300 cm –1 since C=N stretching vibrations of amines and C=O of carbonyl stretching are usually associated with this range. Both polyols’ FTIR spectra in Figure b indicate an amide carbonyl band found at 1614 cm –1 , which confirms that the process of amidation has successfully taken place, thereby resulting in the presence of diethanolamide . In the spectra of COPUAP, characteristic peaks were observed at 1536 and 1515 cm –1 , which are attributed to the bending vibration of the urea-based N–H group formed by the reaction of −NH and −NCO during prepolymerization .…”

“…Both polyols’ FTIR spectra in Figure 3 b indicate an amide carbonyl band found at 1614 cm –1 , which confirms that the process of amidation has successfully taken place, thereby resulting in the presence of diethanolamide. 20 In the spectra of COPUAP, characteristic peaks were observed at 1536 and 1515 cm –1 , which are attributed to the bending vibration of the urea-based N–H group formed by the reaction of −NH and −NCO during prepolymerization. 26 Additionally, the observed peak at 1417 cm –1 of COPUAP is due to the stretching vibration of the urea-based C–N group formed by the reaction of −NH and −NCO during prepolymerization.…”

“…Both polyols' FTIR spectra in Figure 3b indicate an amide carbonyl band found at 1614 cm −1 , which confirms that the process of amidation has successfully taken place, thereby resulting in the presence of diethanolamide. 20 In the spectra of COPUAP, characteristic peaks were observed at 1536 and 1515 cm −1 The lengthening of the PU-urea prepolymer chain increases the viscosity of COPUAP polyol (Figure S2). 30,44 As the chain grows longer, the viscosity of the system increases due to the lengthening of the polymer chains.…”

“…17 This comparison indicates the importance of coconut oil, highlighting its role as a valuable resource material with the capacity to support various applications, such as polyurethane formulations. Moreover, this recognition lays the groundwork for future research into utilizing coconut oil derivatives, such as coconut fatty acid distillate (CFAD), 18 coconut monoglyceride (CMG), 19 or cooking oil wastes, 20 highlighting the importance of exploring coconut oil-based polyols for the production of high-quality rigid foams.…”

Study of Soybean Oil-Based Non-Isocyanate Polyurethane Films via a Solvent and Catalyst-Free Approach

“…Nowadays, there is an effort from the scientific community to find alternatives to the use of isocyanates, which, even though they are a core component for the fabrication of PU, are also harmful compounds as they can lead to respiratory diseases and severe skin irritation. − Alongside that, one of the reagents used for its synthesis is phosgene, which is extremely toxic . Other factors, such as its nonrenewable origin and the limited number of commercially available products when compared to polyols, also instigate the research to find alternatives for this monomer. − This situation pushed research for the development of nonisocyanate PUs (NIPUs). Based on that, among the available synthetic routes, the reaction through a cyclic carbonated compound that reacts with a primary amine became one of the most notorious. − One of the reasons is that the cyclic carbonate monomer can be synthesized through the reaction between epoxy and carbon dioxide (CO 2 ).…”