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Bio-polyurethane and Others
Published in Abdullah Al-Mamun, Jonathan Y. Chen, Industrial Applications of Biopolymers and their Environmental Impact, 2020
Polyurethanes are widely used in the automobile industry. In addition to the foam that makes car seats comfortable, bumpers, interior ceiling sections, spoilers, doors, and windows all use polyurethanes. Polyurethane reduces weight and increases fuel economy, corrosion resistance, insulation, and sound absorption. It has been estimated that the 1995 model cars used an average of 13.6 kg of polyurethane material per car [7].
Introduction to Polyurethanes
Published in I.R. Clemitson, Castable Polyurethane Elastomers, 2015
Acute exposure generally refers to single-dose, high-concentration exposures over short periods. Some of the chemicals used in the polyurethane industry can cause acute health problems and have an immediate effect on the health of people exposed to it. The most prominent of the chemicals are the isocyanates. People with bronchial problems can have an immediate attack. It is often suggested that all employees be screened for lung function and for potential problems. Isocyanates also have the potential to sensitize people and they can develop problems in the future.
Waterborne Polyurethanes: Challenges and Future Outlook
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Felipe M. de Souza, Ram K. Gupta
Despite all the properties and tunability that polyurethane possesses, one of its major drawbacks is its inherent poor resistance to fire, which is due to its high surface area and organic composition. Polyurethanes are particularly dangerous when they go through combustion due to the release of toxic fumes, such as aromatic fragments and cyanides, which are extremely toxic. One of the solutions to reduce the flammability of polyurethane is to incorporate flame-retardants. Flame-retardants can be either additive or reactive. Reactive flame-retardants are chemically bonded to the structure of polyurethane, while additives are just physically blended in the polyurethanes. Flame-retardants can also be toxic; for example, halogen-based flame-retardants are toxic for the environment as well as health. Many other flame-retardants are nontoxic compared to halogen-based flame-retardants. Examples of green flame-retardants are compounds of phosphorus and nitrogen, carbon black, expandable graphite, aluminum, magnesium oxides, and hydroxides. These compounds can be added either by physical blending or by covalently attaching them to the polyurethane structure. These flame-retardant compounds work through two mechanisms: gas or solid phase. The gas-phase mechanism relies on the release of relatively stable radical species that can capture more reactive radical fragments originated from the polyurethane's combustion, hence named radical scavengers. The solid-phase mechanism relies on forming or inducing a compact char layer that blocks the entrance of these radical species and oxygen, hence protecting the unburnt polyurethane underneath it. A viable strategy relies upon combining two or more compounds that can provide these two flame-retardancy mechanisms simultaneously.
Elastic inclusions in ballasted tracks – a review and recommendations
Published in International Journal of Rail Transportation, 2023
H. G. S. Mayuranga, S. K. Navaratnarajah, C. S. Bandara, J. A. S. C. Jayasinghe
It is reported that polyurethane-based inclusions are more expensive due to higher raw material costs and the expensive application process that necessitates specific machinery and a skilled labour force [109]. As a result, they are more appropriate in locations where other remedial techniques cannot be used for a variety of reasons. On the other hand, conducting research on some novel cost-cutting techniques such as manufacturing polyurethane-coated ballast blocks in-house and adding crumb rubber to reduce polyurethane volume would be beneficial [109]. Although it has been reported that un-foamed polyurethane-stabilized ballast facilitates drainage [97], the permeability behaviour of foamed polyurethane-stabilized ballast is unclear [111]. Conversely, there is a lack of laboratory investigations on the hydraulic conductivity of un-foamed polyurethane-reinforced ballast as well. Therefore, a comprehensive laboratory investigation of the permeability behaviour of polyurethane-stabilized ballast is required. Moreover, the production, application, and disposal of polyurethane polymers cause environmental issues. The release of harmful gases during the polyurethane manufacturing process has an impact on air quality, and when the compounds are mixed before the application, harmful gases are released, threatening human health [111]. Besides that, the disposal of polyurethane polymers contributes to the pollution of the environment [131].
Biobased polymers from lignocellulosic sources
Published in Green Chemistry Letters and Reviews, 2023
Rachele N. Carafa, Daniel A. Foucher, Guerino G. Sacripante
Polyurethanes are a versatile class of polymers that are used as foams, elastomers, adhesives, and coatings to name a few. These products are used extensively in markets that include construction, automotive, and packaging (48). Polyurethane foams are generally prepared in a two-step process (49). The first step is the gelation reaction, where the hydroxyl groups of a polyol react with a suitable diisocyanate (O = C = N) to form the urethane linkage, which consists of a carbamate ester (Figure 18(a)). In the second step, the diisocyanate groups react with water to generate carbon dioxide as the blowing agent and forms a urea linkage that provides covalent and hydrogen bonding sites (Figure 18(b)) (48). Combining the urethane and urea linkages from the reaction of diisocyanates forms the desired polyurethane foams, with the rigidity or flexibility of the foam depending on the type of diisocyanate used (Figure 18(c)) (49).
Experimental Analysis of the Effects of a Polyurethane Foam on Geotechnical Seismic Isolation
Published in Journal of Earthquake Engineering, 2022
Michele Placido Antonio Gatto, Lorella Montrasio, Marta Berardengo, Marcello Vanali
Polyurethanes are versatile products, in use in different sectors; in Civil Engineering, they are generally applied for thermal insulation (thanks to their low conductivity) (Albrecht 2000; Schuetz and Glicksman 1984; Wu, Sung, and Chu 1999) and sound insulation (Adachi, Hasegawa, and Asano 1997; Zhang et al. 2012). From a seismic point of view, few literature examples show polyurethane applications just for the liquefaction risk mitigation (Traylen, Van Ballegooy, and Wentz 2016). The polyaddition reaction of isocyanate (containing N-C-O) and polyol (containing OH groups), thanks to blowing agents included in polyol chemical composition, gives rise to cellular low-density materials, where gasses are trapped within the resulting structure; coupled to soil, they give rise to a low impedance ratio system.