Recycling Of Polyurethanes Research Articles

Fast pyrolysis of polyurethanes and polyisocyanurate with and without flame retardant: Compounds of interest for chemical recycling

To date, the recycling of polyurethane (PU) and polyisocyanurate (PIR) waste still poses a significant problem. Within this contribution, the thermal degradation of high-resilient ether PU, semirigid PU, rigid PU, and (PIR) with and without TCPP flame retardant was studied at different temperatures to identify and quantify the main products. For this, a tandem micropyrolyzer coupled to GC × GC with FID and ToF-MS detectors was used, and the yield volatiles, light gases, and residue was quantified. The volatile pyrolysis vapours obtained from pyrolyzing high-resilient ether PU and semirigid PU at 600 °C were very similar, and the main products obtained were ethylene and propylene (combined yield of ~13 wt%), ~16 wt% of various oxygenates, and 4–6 wt% organic nitrogen compounds. The oxygenates included mostly poly-ether type compounds with varying molecular weight, and these are attributed to the decomposition of the polyol chains forming the soft segments of the polymer. The main semi-volatile nitrogen compound was 4,4′-methylenedianiline, attributed to the decomposition of the hard segments in the PU structure synthesized from MDI. The pyrolysis vapours from rigid PU contained several ether-type compounds and high yields of heteroatom-free monoaromatics—in particular styrene. The PIRs were more difficult to decompose and volatilize than the PUs, resulting in ~20 wt% higher residue yields. The charring propensity was even higher in the absence of a flame retardant in the formulation. Pyrolysis of TCPP-containing PIR produced Cl-containing pyrolysis vapours such as allyl chlorides. While the yield of H2O was comparable for the different PUs and PIR, pyrolysis of PIR produced higher yields of CO2 and less CO compared to the different PUs. The use of catalysts can help to convert PU waste pyrolysis vapours more efficiently to desirable chemicals.

Kinetic Monte Carlo Tool for Kinetic Modeling of Linear Step‐Growth Polymerization: Insight into Recycling of Polyurethanes

AbstractA kinetic Monte Carlo model of polyurethane polymerization which explicitly tracks the polymer sequences is developed and shared. This model is benchmarked against theoretical and experimental polyurethane data and used to investigate the effect on oligomer distributions of unequal reactivity of the first and second isocyanate to react. The reverse reactions using thermodynamic consistency are then added to the framework, and analogous to the addition polymerization concept of ceiling temperature, equilibrium chain length distributions at various temperatures are calculated. For a mixture of three monomers AA, BB, and CC, where BB and CC do not react with one another, are present in stoichiometric proportions, and have different enthalpies of reaction with AA, an odd‐even effect emerges. Odd length chains are more likely than even length chains for temperatures at which BB and CC have significantly different equilibrium conversions. The concept of ceiling temperature that is typically cited for addition polymers is extended here to provide a measure of conditions under which depolymerization for recycling is favored.

Breakthrough in polyurethane bio-recycling: An efficient laccase-mediated system for the degradation of different types of polyurethanes.

Development of green, efficient and profitable recycling processes for plastic material will contribute to reduce the expanding plastic pollution and microplastics accumulation in the environment. Polyurethanes (PU) are versatile polymers with a large range of chemical compositions and structures. This variability increases the complexity of PU waste management. Biological recycling researchers have recently demonstrated great interest in polyethylene terephthalate. The adaptation of this route towards producing polyurethanes requires the discovery of enzymes that are able to depolymerize a large variety of PU. A laccase mediated system (LMS) was tested on four representative PU models, with different structures (foams and thermoplastics), and chemical compositions (polyester- and polyether-based PU). Size exclusion chromatography was performed on the thermoplastics and this revealed a significant reduction in the molar masses after 18days of incubation at 37°C. Degradation of foams under the same conditions was demonstrated by microscopy and compression assay for both polyester- and polyether-based PU. This study represents a major breakthrough in PU degradation, as it is the first time that enzymatic degradation has been clearly demonstrated on a polyether-based PU foam. This work is a step forward in the development of a sustainable recycling pathway, adapted to a large variety of PU materials.

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

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.

Recycling of polyurethane by acidolysis: The effect of reaction conditions on the properties of the recovered polyol

Recently, a method for the recycling polyurethane (PU), the acidolysis, was reported in which dicarboxylic acids (DA) were used as cleavage agents. Yet, the effect of reaction conditions on the properties of the recovered polyol (RP) was not discussed. Therefore, aiming at achieving in-depth knowledge of acidolysis, in this work, the effect of the recycling conditions on the properties of RP was statistically evaluated. Temperature and PU/DA ratio were found to be the predominant factors with influence of 62.4% and 31.5% on the hydroxyl number (OHnumber), respectively. In turn, the acid value (AV) proved to be dependent on several factors and their interactions. Yet, the major influence on AV, the combination of PU/DA ratio and temperature, has 39.7% of influence. Using linear regression to predict the properties of the RP, both the experimental and the predicted values presented high correlation. Afterwards, flexible polyurethane foams (PUF) were produced using up to 30% (w/w) of RP as partial substitute of virgin polyol. It was observed that all foams present similar density, although the presence of the RP enhances their stiffness, which was attributed to the higher content of aromatic moieties of RP. Therefore, the suitability of this recycling method and the subsequent use of the reaction products in the production of new foams was demonstrated. This is fully in line with the principles of circular economy.

Polyurethane Recycling and Disposal: Methods and Prospects.

Growing water and land pollution, the possibility of exhaustion of raw materials and resistance of plastics to physical and chemical factors results in increasing importance of synthetic polymers waste recycling, recovery and environmentally friendly ways of disposal. Polyurethanes (PU) are a family of versatile synthetic polymers with highly diverse applications. They are class of polymers derived from the condensation of polyisocyanates and polyalcohols. This paper reports the latest developments in the field of polyurethane disposal, recycling and recovery. Various methods tested and applied in recent years have proven that the processing of PU waste can be economically and ecologically beneficial. At the moment mechanical recycling and glycolysis are the most important ones. Polyurethanes’ biological degradation is highly promising for both post-consumer and postproduction waste. It can also be applied in bioremediation of water and soil contaminated with polyurethanes. Another possibility for biological methods is the synthesis of PU materials sensitive to biological degradation. In conclusion, a high diversity of polyurethane waste types and derivation results in demand for a wide range of methods of processing. Furthermore, already existing ones appear to be enough to state that the elimination of not reprocessed polyurethane waste in the future is possible.

Enzymatic recycling of thermoplastic polyurethanes: Synergistic effect of an esterase and an amidase and recovery of building blocks

Biological recycling of polyurethanes (PU) is a huge challenge to take up in order to reduce a large part of the environmental pollution from these materials. However, enzymatic depolymerization of PU still needs to be improved to propose valuable and green solutions. The present study aims to identify efficient PU degrading enzymes among a collection of 50 hydrolases. Screenings based on model molecules were performed leading to the selection of an efficient amidase (E4143) able to hydrolyze the urethane bond of a low molar mass molecule and an esterase (E3576) able to hydrolyze a waterborne polyester polyurethane dispersion. Degradation activities of the amidase, the esterase and a mix of these enzymes were then evaluated on four thermoplastic polyurethanes (TPU) specifically designed for this assay. The highest degradation was obtained on a polycaprolactone polyol-based polyurethane with weight loss of 33% after 51 days measured for the esterase. Deep cracks on the polymer surface observed by scanning electron microscopy and the presence of oligomers on the remaining TPU detected by size exclusion chromatography evidenced the polymer degradation. Mixing both enzymes led to an increased amount of urethane bonds hydrolysis of the polymer. 6-hydroxycaproic acid and 4,4′-methylene dianiline were recovered after depolymerization as hydrolysis products. Such building blocks could get a second life with the synthesis of new macromolecular architectures.

Simultaneous recovery of H2-rich syngas and removal of HCN during pyrolytic recycling of polyurethane by Ni/Mg/Al catalysts

Polyurethanes (PUs) such as flexible (cushioning material and sponge) and rigid (different insulators) forms and elastomers (flexible tube and smartphone case) were thermally decomposed at 500 °C. The useless decomposition products were converted into H2-rich syngas and the toxic HCN in it was removed by Ni/Mg/Al catalysts at 800 °C under 50 vol% steam/He flow. The resultant total gas production was 1411–1623 mL/g (H2: 794–967 mL/g), which was almost 30 times larger than that obtained from simple pyrolysis of PUs where no H2 was produced. Meanwhile, there was a drastic reduction of HCN concentration in the product gas from a maximum at 2.8 to 0.2–0.6 vol%. The excellent performance on the removal of HCN and the enhanced H2-rich syngas production is due to the synergy between Ni, Mg, and Al in the catalysts. This approach has great promise for treating a variety of PU wastes that cannot be recycled effectively otherwise.

8-20.超臨界二酸化炭素を溶媒として用いるクリーンなポリウレタンのリサイクルプロセス((5)廃棄物転換素材の利用,Session 8 環境対策・リサイクル)

8-20.超臨界二酸化炭素を溶媒として用いるクリーンなポリウレタンのリサイクルプロセス((5)廃棄物転換素材の利用,Session 8 環境対策・リサイクル)

Thermo-Chemical Decomposition Study of Polyurethane Elastomer Through Glycerolysis Route with Using Crude and Refined Glycerine as a Transesterification Agent

Due to the increasing amount of polyurethane waste, chemical recycling of these materials is a topic of growing interest for many researchers. The primary purpose of polyurethane feedstock recycling is to recover the starting polyol. In this study glycerolysis using glycerine from two sources and two purity grades is proposed as a method of chemical recycling. The main effort of this paper focuses on the employment of commercial glycerine of analytical grade and waste glycerine without purification derived from the biodiesel production, as a decomposing agent for polyurethane recycling. In this study, the influence of polyurethane to glycerine mass ratio (PU/GL) and the type of decomposing agent on the chemical structure by FTIR, 1H NMR and GPC was examined. FTIR analysis of the glycerolysates showed absorption peaks similar to the virgin polyol. Those results are in compliance with GPC chromatograms, which showed for all samples, well-defined peak at ca. 13 min of retention time. The molecular weight of glycerolysates was ranging from 800 to 1300 g mol−1 depending on PU/GL mass ratio. The novel decomposition agent, namely waste glycerine derived from biodiesel production was successfully used in glycerolysis process.

Synthesis and characterisation of polyurethane elastomers with semi-products obtained from polyurethane recycling

In this work polyurethane elastomers were synthesised by using different mixtures of a petrochemical and glycerolysate polyols and 4,4-diphenylmethane diisocyanate (MDI). Glycerolysate polyol was produced from polyurethane foam decomposition using crude glycerine as a decomposition agent. The structure and thermal properties of obtained semi-product were similar to the polyol used in the synthesis of original foam. Glycerolysate polyol was incorporated into polyurethane formulation as soft segment (SS). Since polyol is one of the major component in polyurethane system (>70%) introducing recycled components leads to lowering of consumption of petrochemicals and valorisation of recycled products. Polyurethane elastomers containing up to 16.4wt.% of glycerolysate polyol were synthesised, soluble in dimethylformamide (DMF) up to ca. 12wt.%. The effect of glycerolysate polyol content on the structure and properties was analysed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and mechanical tests. Thermal properties did not worsen after using glycerolysate into polyurethane formulation. A slight increase in glass transition temperature is observed with the incorporation of glycerolysate polyol. Elastic modulus, tensile strength and hardness of polyurethane elastomers increased with recycled polyol content. Moreover they showed high elongation at break values.

Single‐phase product obtained via crude glycerine depolymerisation of polyurethane elastomer: structure characterisation and rheological behaviour

AbstractPolyurethane recycling is a topic of growing interest due to the increasing amount of polyurethane waste. The main purpose of polyurethane feedstock recycling is to recover the starting polyol, a valuable material. In this work, a method of polyurethane thermo‐chemical recycling, glycerolysis by means of crude glycerine, is proposed. The main effort is focused on the employment of crude glycerine without purification from biodiesel production as a decomposing agent for polyurethane recycling. The influence of polyurethane‐to‐glycerine mass ratio (PU/GL) on chemical structure was examined using Fourier Transform Infrared (FTIR) and Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy and Gel Permeation Chromatography (GPC). Glass transition temperature (Tg) and thermal properties using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and also rheology were analysed. FTIR and 1H NMR analyses of the glycerolysates showed peaks similar to those of virgin polyol. From GPC chromatograms it was concluded that glycerolysates are a mixture of compounds with different molecular weights, such as recovered polyol, urethane oligomers or carbamates. Glycerolysates indicated Tg in the range from −65 to −60 °C and, for high PU/GL ratio, a second Tg appeared. Thermal stability of glycerolysates increased with increasing PU/GL ratio. The molecular weight of glycerolysates ranged from 700 to 1020 g mol−1 depending on PU/GL mass ratio. The semi‐products were defined as non‐Newtonian fluids, where viscosity depended on the shear rate. Crude glycerine, derived from biodiesel production, was successfully used in polyurethane decomposition, resulting in valuable semi‐products. © 2016 Society of Chemical Industry

Polyurethane Waste Reduction and Recycling: From Bench to Pilot Scales

In this review, reports, patents and recently published papers and documents on polyurethane recycling, especially chemical recycling methods, are investigated in order to find an adequate method for waste reduction, protecting the environment and preventing waste land filling. The recycling of polyurethane has always posed unique challenges due to its wide variety of applications, from the industry to bio-based materials, namely, artificial organs. Mechanical regrinding is the oldest method in polyurethane waste recycling and the use of the regrind wastes as filler in the new formulations. Chemical recycling of polyurethanes by hydrolysis, aminolysis and glycolysis is for the most part considered economically uncompetitive compared to formulating with virgin raw materials. Also some thermochemical processes are utilized for PU recycling. Recycling has opened an effective and economic route for polyurethane waste treatment. Nonetheless, more research efforts are required in order to scale up the recycling methods.

A gestão do conhecimento aplicada à reciclagem de componentes automotivos através do tratamento das informações contidas em documentos de patentes

This article evaluates the technologies adopted for recycling and reuse of automobile components, through the analysis of patents documents. The automobile batteries recycling is the main topic, followed by the automatic disassembly of vehicles, tires recycling and polyurethane recycling. None document approached recycling of steel and aluminum or ceramics products. The reduced number of technologies for the recycling of the polymeric compounds (including polyurethane) indicates that a bigger number of research and inventions must be elaborated in the next years, aiming at to the reduction of costs of processes and adequacy to the more restricted environmental legislation.

Recycling of Polyurethane using High-pressure Steam Treatment

Recycling of Polyurethane using High-pressure Steam Treatment

Continuous Process for Recycling of Polyurethane Foam

The investigation deals with the recycling of high resiliency polyurethane (PU) foam by the application of high-power ultrasound in a continuous ultrasonic reactor. The foam has been decrosslinked at various screw speeds and various amplitudes, then blended at different ratios with the virgin polyurethane rubber (PUR) and cured. The die pressure and the total power consumption have been recorded as a function of processing conditions. Rheological and mechanical properties, hardness as well as gel fraction and crosslink density of the decrosslinked foam and cured blends have been measured and compared in an attempt to find out the optimum condition for decrosslinking. Blends have also been prepared using different proportions of ground samples and virgin rubber, and a comparison of the properties between these blends and the blends of the decrosslinked foam has been carried out. The results show that compared to the ground samples, the blends of the decrosslinked samples are easier to mix and exhibit enhanced properties.

Hard Metals in New Orleans

Recent progress in the recycling and recovery of polyurethane and polyurethane composites is reviewed. The various types of polyurethane waste products, consisting of either old recycled parts or production waste, are generally reduced to a more usable form, such as flakes, powder or pellets, depending on the particular type of polyurethane that is being recycled. The various recycling technologies for material and chemical recycling of PU materials have greatly contributed to improve the overall image regarding the recyclability of polyurethanes in recent years, by far the most important being regrinding and glycolysis. These technologies open an emerging, effective and economic route for recycling polyurethane rigid foams and composite. Polyurethane foam in automotive seating has been successfully recycled using regrind technology. Glycolysis of polyurethanes can be economically acceptable, but still requires more development in order to tolerate more contamination in the post-consumer material. Current technologies can recover the inherent energy value of polyurethanes and reduce fossil fuel consumption. Energy recovery is considered the only suitable disposal method for recovered material for which no markets exist or can be created. Increasing waste-to-energy and other thermal processing activities involving gasification, pyrolysis and two-stage combustion has contributed for the disposal of significant amounts of scrap PU without many difficulties. It is concluded that many of the plastic feedstock recycling processes appear to be technically feasible and robust enough to warrant further development in the future.

A novel approach to recycling of polyurethanes: chemical degradation of flexible polyurethane foams by triethyl phosphate

It was established that flexible polyurethane foams based on polyester or polyether polyol and toluene diisocyanate can be converted quantitatively into liquid form by treatment with triethyl phosphate (C 2H 5O) 3P(O). Structures of the degraded products were studied by 1H, 13C and 31P NMR spectroscopy. The degraded products are phosphorus containing oligourethanes. The likely mechanism is presented.

ポリウレタンのリサイクル

ポリウレタンのリサイクル

Progress in recycling of polyurethanes

Progress in recycling of polyurethanes