Showing papers on "Polyurethane published in 2021"

Self-healing polyelectrolyte complex coating for flame retardant flexible polyurethane foam with enhanced mechanical property

Abstract: A self-healing coating containing polyethyleneimine (PEI)/ammonium polyphosphate (APP) polyelectrolyte complex was successfully prepared, and then was deposited on flexible polyurethane foam (FPUF) in association with graphene oxide (GO) via a simple dip-nip process to improve the flame retardancy and mechanical property. The vertical burning test revealed that the FPUF coated with PEI/APP and GO extinguished immediately after removing the igniter. The cone calorimeter results demonstrated that the coating effectively reduced the peak heat release rate by 63.8%. The char analysis suggested that PEI/APP formed an intumescent char structure and released inert gases, whilst GO improved the compactness of the char layer. Furthermore, the compressive strength of the coated foam sample was increased by 175.0% compared to that of the control FPUF sample. The mechanical properties analysis and morphology observation proved that the PEI/APP-GO coating had self-healing ability. This unique intrinsic self-healing coating provides a new opportunity for imparting flame retardancy and excellent mechanical property to foam materials used in many commercial cases.

Polyurethanes from Direct Organocatalytic Copolymerization of p‐Tosyl Isocyanate with Epoxides

Abstract: The direct copolymerization of p-tosyl isocyanate (TSI) with epoxides, initiated by onium salts in the presence of trialkylborane, to produce polyurethanes is reported. The rate of copolymerization and the (regio)selectivity were investigated in relation to the trialkylborane and the initiator used. Under optimized conditions such copolymerizations have been successfully performed for a wide range of epoxides, including ethylene oxide, propylene oxide, 1-octene oxide, cyclohexene oxide, and allyl glycidyl ether. These copolymerizations afford a new category of polyurethanes, clear of side products such as cyclic oxazolidinone, isocyanurate, and poly(isocyanate) linkages. The experimental conditions used in this work are compatible with those for the organocatalytic (co)polymerization of other oxygenated monomers and CO2 , holding the potential for their terpolymerization with p-tosyl isocyanate and the development of new materials with unprecedented properties.

Bio-based rigid polyurethane foam from castor oil with excellent flame retardancy and high insulation capacity via cooperation with carbon-based materials

Abstract: In this work, we prepared the biomass castor oil-based rigid polyurethane foams (RPUF). The two bio-based RPUFs contain modified polyols from castor oil, one of which was transamidated castor oil with diethanolamine (BIO1) and another was further modified epoxidized polyols in BIO1 with phenylphosphonic acid. The cellular structure, thermal, flame retardant and mechanical properties of RPUF via incorporation of expandable graphite (EG) and graphene oxide (GO) on a total fixed amount of 6 wt% were studied by scanning electron microscopy (SEM), thermal conductivity, limiting oxygen index (LOI), vertical burning test (UL94) and cone calorimeter test (CCT), etc. The cellular structure indicated that GO facilitates the dispersion of EG and decreases the cell size of the foam. The thermal and fire behaviors indicated that GO increased the insulation capacity and the flame-retardant performance of RPUFs. The optimal sample BIO2/EG/GO obtained V-0 rating, whereas BIO2/EG obtained only V-2 rating on the UL94 test. Moreover, results from CCT showed that the BIO2/EG/GO effectively reduced heat release rate (HRR), total heat release (THR) and total smoke production (TSP) by 54%, 24% and 15%, respectively, in comparison with BIO1 and decreased the HRR and THR 46% and 6%, respectively, compared to BIO2 sample. The compressive performance of BIO2/EG/GO and BIO2/EG increased to 0.11 MPa compared to 0.07 MPa from BIO1. These interesting results proved a new strategy to develop a bio-based flame-retardant RPUF as fire safety thermal insulation materials by incorporating natural-based carbon materials.

Catalytic Hydrogenation of Polyurethanes to Base Chemicals: From Model Systems to Commercial and End-of-Life Polyurethane Materials.

Abstract: Polyurethane (PU) is a highly valued polymer prepared from diisocyanates and polyols, and it is used in everyday products, such as shoe soles, mattresses, and insulation materials, but also for the construction of sophisticated parts of medical devices, wind turbine blades, aircrafts, and spacecrafts, to name a few. As PU is most commonly used as a thermoset polymer composed of cross-linked structures, its recycling is complicated and inefficient, leading to increasing PU waste accumulating every year. Catalytic hydrogenation represents an atom-efficient means for the deconstruction of polyurethanes, but so far the identification of an efficient catalyst for the disassembly of real-life and end-of-life PU samples has not been demonstrated. In this work, we reveal that a commercially available catalyst, Ir- iPrMACHO, under 30 bar H2 and 150-180 °C, is a general catalyst for the effective hydrogenation of the four cornerstones of PU: flexible solid, flexible foamed, rigid solid, and rigid foamed, leading to the isolation of aromatic amines and a polyol fraction. For the first time, a variety of commercial PU materials, including examples of foams, inline skating wheels, shoe soles, and insulation materials, has been deconstructed into the two fractions. Most desirable, our reaction conditions include the use of isopropyl alcohol as a representative of a green solvent. It is speculated that a partial glycolysis at the surface of the PU particles is taking place in this solvent and reaction temperatures in the presence of catalytic amounts of base. As such a more efficient hydrogenation of the solubilized PU fragments in isopropyl alcohol becomes possible. As the isolated anilines are precursors to the original isocyanate building blocks, and methods for their conversion are well-known, the work reported in this paper provides a realistic indication of a potential circular plastic economy solution for PU. Preliminary experiments were also undertaken applying Mn- iPrMACHO for the deconstruction of a commercial flexible PU foam. Although successful, more forcing conditions were required than those when applying Ir- iPrMACHO.

Effects of Polyurethane Thermoplastic Elastomer on Properties of Asphalt Binder and Asphalt Mixture

Abstract: Polyurethane (PU) is a synthetic material available for researchers to be designed in terms of their demands. This study prepared a novel polyurethane thermoplastic elastomer (PUTE) as an a...

Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis–Hydrolysis Demonstration

Abstract: The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis.

The effect of natural fibre reinforcement on polyurethane composite foams – A review

Abstract: The use of natural fibre reinforced polyurethane composite foams is becoming increasingly popular in the cellular foam industry. This demand is due to the increase in the use of ecofriendly, biodegradable, and sustainable materials to produce polyurethane composite materials for such applications. In this regard, natural fibres from agro-waste are being preferred to their synthetic counterparts due to readily availability, strength, lightweight, biodegradability, and cost-effectiveness. In addition to their renewable nature, the use of natural fibre in polyurethane foams produces composite foams with better properties than the neat polyurethane foams. This review explores the preparation, and properties of natural fibre reinforced polyurethane composite foams and discusses the effect of chemical modification of these fibres on the interfacial adhesion of the fibre-polymer matrix system. It also assesses the trends and future potential of the global market of natural fibres and the polyurethane composite foams.

Bio-Based Polyurethane Foams with Castor Oil Based Multifunctional Polyols for Improved Compressive Properties.

Abstract: Currently, most commercial polyols used in the production of polyurethane (PU) foam are derived from petrochemicals. To address concerns relating to environmental pollution, a sustainable resource, namely, castor oil (CO), was used in this study. To improve the production efficiency, sustainability, and compressive strength of PU foam, which is widely used as an impact-absorbing material for protective equipment, PU foam was synthesized with CO-based multifunctional polyols. CO-based polyols with high functionalities were synthesized via a facile thiol-ene click reaction method and their chemical structures were analyzed. Subsequently, a series of polyol blends of castor oil and two kinds of castor oil-based polyols with different hydroxyl values was prepared and the viscosity of the blends was analyzed. Polyurethane foams were fabricated from the polyol blends via a free-rising method. The effects of the composition of the polyol blends on the structural, morphological, mechanical, and thermal properties of the polyurethane foams were investigated. The results demonstrated that the fabrication of polyurethane foams from multifunctional polyol blends is an effective way to improve their compressive properties. We expect these findings to widen the range of applications of bio-based polyurethane foams.

Flame-retarded polyurethane foam conferred by a bio-based nitrogen‑phosphorus-containing flame retardant

Abstract: Flammable polyurethane foam (PUF) is still an essential material related to buildings and furniture, causing loss of property and lives every year. A novel compound containing phosphorus and nitrogen (referred to as DOPO-NIBAM) was successfully synthesized from camphene as a renewable raw material and applied as a flame retardant in polyurethane foam (DNPUF). During the combustion of DNPUF, DOPO-NIBAM produced phosphorus-free radicals and incombustible gases and promoted the formation of a phosphorus-rich char layer, both of which reduced the flammability of DNPUF. Compared with pure PUF, the limiting oxygen index of DNPUF increased by 41.7%. The peak heat release rate (PHRR) of DNPUF decreased by 40.3%. The compressive strength of DNPUF is significantly enhanced by 166% due to the rigid groups of DOPO-NIBAM. This work demonstrates that the novel phosphorus and nitrogen flame retardant (DOPO-NIBAM) can improve the flame retardancy and mechanical properties of polyurethane foam. DNPUF materials containing DOPO-NIBAM may act as the potential candidate for fireproof building materials.

Waterborne polyurethane/3-amino-polyhedral oligomeric silsesquioxane (NH2-POSS) nanocomposites with enhanced properties

Abstract: To study the influences of 3-amino-polyhedral oligomeric silsesquioxane (NH2-POSS) on the properties of waterborne polyurethanes (WPU), a series of NH2-POSS modified WPUs were synthesized by using polypropylene glycol (PPG-2000, PPG-310), 2,2-dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI), and NH2-POSS via a one-pot reaction and a high shear emulsification method. The results showed that when the NH2-POSS amount in the WPU/NH2-POSS nanoemulsion was 5.73 wt% (WPU2, based on the weight of WPU resin), its viscosity was 2.496 MPa · s and its Zeta potential was 63.7 mV(pH = 6.1), showing lower viscosity and better dispersion stability. The particle size of WPU2 is smaller than that of WPU0, and the polydispersion index (PDI) of WPU2 was decreased from 5.520 to 3.837 indicating a higher crosslinking density. In addition, the thermal stability of WPU/NH2-POSS nanoemulsion was increased with the content of NH2-POSS from 0.00 to 13.19%. The water contact angle values for the WPU2 (84.5°) were higher than that of WPU0 (80.2°), showing an improvement of the hydrophobic properties. This WPU/NH2-POSS nanocomposites can be used for making coating adhesive for textile and hosting matrix for making multifunctional nanocomposites.

Recent Advances in Fabrication of Non-Isocyanate Polyurethane-Based Composite Materials

Abstract: Polyurethanes (PUs) are a significant group of polymeric materials that, due to their outstanding mechanical, chemical, and physical properties, are used in a wide range of applications. Conventionally, PUs are obtained in polyaddition reactions between diisocyanates and polyols. Due to the toxicity of isocyanate raw materials and their synthesis method utilizing phosgene, new cleaner synthetic routes for polyurethanes without using isocyanates have attracted increasing attention in recent years. Among different attempts to replace the conventional process, polyaddition of cyclic carbonates (CCs) and polyfunctional amines seems to be the most promising way to obtain non-isocyanate polyurethanes (NIPUs) or, more precisely, polyhydroxyurethanes (PHUs), while primary and secondary -OH groups are being formed alongside urethane linkages. Such an approach eliminates hazardous chemical compounds from the synthesis and leads to the fabrication of polymeric materials with unique and tunable properties. The main advantages include better chemical, mechanical, and thermal resistance, and the process itself is invulnerable to moisture, which is an essential technological feature. NIPUs can be modified via copolymerization or used as matrices to fabricate polymer composites with different additives, similar to their conventional counterparts. Hence, non-isocyanate polyurethanes are a new class of environmentally friendly polymeric materials. Many papers on the matter above have been published, including both original research and extensive reviews. However, they do not provide collected information on NIPU composites fabrication and processing. Hence, this review describes the latest progress in non-isocyanate polyurethane synthesis, modification, and finally processing. While focusing primarily on the carbonate/amine route, methods of obtaining NIPU are described, and their properties are presented. Ways of incorporating various compounds into NIPU matrices are characterized by the role of PHU materials in copolymeric materials or as an additive. Finally, diverse processing methods of non-isocyanate polyurethanes are presented, including electrospinning or 3D printing.