Rigid Polyurethane Foam Waste Research Articles

Exploring the potential of rigid polyurethane foam waste in structural lightweight concrete

The structural lightweight concrete is gaining significant interest in the research community due to its reduced dead load. The reduction in the self-weight not only lowers the gravity load but can also lower the seismic demands for the structural members and hence can potentially reduce the overall cost. This study examines the feasibility of developing a sustainable structural lightweight concrete by utilizing rigid polyurethane foam waste as coarse aggregates (5–10 mm). The silica fume was incorporated as a cement replacement to enhance the compressive strength of the mix. A total of three composite mix formulations consisting of polyurethane foam, cement-coated polyurethane foam, and pumice (control specimens) as coarse aggregates were tested. The testing was performed for workability, compressive strength, flexural strength, elastic modulus, absorption, permeable voids, chloride-ion penetration, freeze and thaw resistance, and drying shrinkage. The results achieved for elastic modulus, chloride ion penetrability, and drying shrinkage, were meeting the minimum requirements of the standards making this composite suitable for the structural application. The results revealed that uncoated polyurethane based lightweight aggregate concrete resulted in an air-dry density of 1829 kg/m3 with the corresponding compressive strength of 19.5 MPa and flexural strength of 2.78 MPa at 28 days. Besides, the polyurethane-based lightweight concrete also showed lower internal structure damage against freeze and thaw action, along with improved thermal conductivity.

Characterization of pyrolysis behavior for rigid polyurethane foam wastes with different densities through TGA-FTIR-DSC-MCC and Hill Climbing Optimization methods

Pyrolysis technology is one of the most effective thermal treatment methods recycling rigid polyurethane foam (RPUF) waste. To optimize pyrolysis recovery efficiency, quantifying the pyrolysis reaction kinetics and the heat required for the thermal treatment process is critical. This work focuses on establishing a systematic methodology to quantify pyrolysis reaction kinetics and thermodynamics for RPUF waste. RPUF waste with two different densities (RPUFρ100 and RPUFρ45) were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) under anaerobic atmosphere to measure mass and heat flow information. The obtained data were inversely analyzed using a numerical framework known as ThermaKin2Ds. Pyrolysis reaction mechanisms with four and three consecutive first-order reactions were developed to reproduce the TGA data for RPUFρ100 and RPUFρ45, respectively. The Hill Climbing Optimization Algorithm was employed to adjust the reaction kinetics for an improved agreement between the ThermaKin2Ds-reproduced and experimental data. Based on the heat flow data from DSC tests, the specific heat capacity of each condensed-phase component was determined by using the inverse modeling method. Additionally, the micro-scale combustion calorimeter was used to generate the heat release data that served as the target data for inversely determining the heats of complete combustion, hc, of each pyrolyzate. The established pyrolysis reaction models was further validated by predicting the TGA results collected under different external heating conditions. Subsequently, the generated combustion-inhibiting gases (CO2) and combustion-promoting gases (olefins, alkanes, carboxylic acids, etc.) were characterized through TGA coupled with Fourier-transform infrared spectroscopy (TG-FTIR). This allowed us to elucidate the gas-phase combustion phenomena observed in MCC experiments. This work provides a core set of parameters for optimizing the thermal treatment conditions of RPUF waste.

Performance characterization and pyrolysis kinetics of graphene-reinforced, green rigid polyurethane foam

Rigid polyurethane (PU) foam waste was chemically degraded by the two-component alcoholysis agent of diethylene glycol and ethanolamine and graphine oxide (GO), and PU/GO nanocomposites were obtained by one-step foaming. Rigid PU foam was chemically degraded by adding different proportions of two-component alcoholysis agent and GO. Research on the introduction of GO to degrade PU matrices, using different proportions of the alcoholysis agent degradation law of PU oligomer polyols for regeneration, was conducted through the viscosity and hydroxyl value of recycled polyol determination, the infrared spectrum of foam samples, x-ray photoelectron spectroscopy, density, water absorption, thermogravimetric and polarizing microscope analysis. The results showed that the compressive strength of PU/GO nanocomposites increased to 0.2754 MPa by 9.6% when the amount of graphene was 0.5% and the thermal conductivity 0.0120 W m−1·K−1, which is 4.8% reduction. The Kissinger equation was used to calculate the activation energy of the regenerated PU pyrolysis reaction. The results showed that the activation energy of the regenerated PU pyrolysis reaction was improved by adding the graphene.

Sustainable Polyurethane‐Derived Heteroatom‐Doped Electrode Materials for Advanced Supercapacitors

AbstractThis work presented a new method to recycle rigid polyurethane foam (RPUF) waste. A two‐step method to carbonize and activate RPUF was applied to synthesize sustainable polyurethane‐derived N, O co‐doped electrode materials for supercapacitors (SCs). Structural characterization showed a three‐dimensional honeycomb‐like pore structure rich with micro/mesopores formed with a 3647 m2 g−1 maximum specific surface area (SSA), and 2.04 at.% N and 8.30 at.% O were successfully co‐doped into the polyurethane porous carbons (PPCs). These properties created synergistic effects that enhanced the ion storage capacity and pseudocapacitance of the synthesized PPCs. As a result, the optimal PPC‐500‐800‐3 yielded excellent maximum specific capacitance in a three‐electrode (487 F g−1) and symmetric SC (324 F g−1) systems in a 1 m H2SO4 electrolyte at 1 A g−1 current density. Moreover, for the LiTFSI/H2O/(ACN)3.5 electrolyte, PPC‐500‐800‐3 produced a maximum energy density of 29.36 W kg−1 in a symmetric SC. After 10,000 cycles, PPC‐500‐800‐3 could achieve high cycling stability, maintaining 96.8 % of the initial capacitance at a 5 A g−1 current density.

Recovery of Green Polyols from Rigid Polyurethane Waste by Catalytic Depolymerization.

Polyurethane (PU) is one of the most versatile polymers available and can be found in an infinite number of formats ranging from rigid or flexible foams to elastomers. Currently, most Rigid PU Foam (RPUF) waste is landfilled, even though a small amount is mechanically recycled, in which the material is conditioned in size to a very fine powder, which is introduced as a filler. In this work, chemical recycling of two types of rigid PU foams is studied, the major difference being the aliphatic or aromatic nature of the isocyanate used in the synthesis. A solvolysis process is developed, a chemical depolymerization that breaks the chains by means of a chemical agent, a solvent, in the presence of a catalyst and under controlled process conditions. The glycolysis products are purified by vacuum distillation, centrifugation, and acid water treatment, depending on the most suitable process for each waste type. Optimal process conditions are established to obtain high-purity green polyols by performing a set of catalytic glycolysis reactions at laboratory scale with the previously conditioned RPUF waste samples. The physicochemical properties of the polyols, such as hydroxyl value, acid value, average molecular weight (Mn), and viscosity, are analyzed. The chemical structure and thermal stability of the polyols are studied by means of FTIR and TGA, respectively. Partial substitution of the commercial polyol (up to 15 wt.%) by the recycled polyols for RPUF synthesis is studied and characterized.

Assessment of the economic recycling potential of a glycolysis treatment of rigid polyurethane foam waste: A case study from Thailand

This research assessed the economic feasibility of recovering polyol from rigid polyurethane foam (RPUF) waste, collected from dismantled, discarded refrigerators, by a single-phase glycolysis recycling process using domestic crude glycerol (a byproduct of biodiesel production) as a transesterification agent. The study, conducted in Thailand, took into account benefits from the added value of the recovered product, the investment and related operating costs of the process, demand (the need for the recovered product) and supply (the amount of RPUF waste). The results showed that the production of recovered polyol from RPUF waste is economically feasible, with a net present value of 1,113,018 USD, an internal rate of return (IRR) of 22.9%, and a payback period of 4.4 years. Due to the high IRR, project investment should be attractive to both the government and private sector investors. In addition, a sensitivity analysis was conducted to assess the economic resilience of the process to uncertainties in key factors, including the prices of the machinery, recovered polyol, crude glycerol and stannous octoate, and the amount of RPUF waste available. The sensitivity analysis showed that the economic feasibility was most sensitive to the price of the recovered polyol, followed by the amount of RPUF waste and the prices of the machinery, crude glycerol and stannous octoate. Based on these results, technological, operational, financial, and regulatory policy recommendations were also presented.

Ecological Design of New Efficient Energy-Performance Construction Materials with Rigid Polyurethane Foam Waste

An ecological mortar is designed from industrial sub-products, with the objective of utilizing both the slag residues, generated during steel manufacturing processes, and the waste from Polyurethane Foam (PF) panels, generated during refrigerator chamber manufacturing processes. The ecological mortar design involves the dosing of Electric Arc Furnace (EAF) slag, together with finely ground Polyurethane Foam, cement, and additives. An energy efficient prefabricated block is designed with the mortar, for use in construction, and its energy performance is assessed as a material inserted within the envelope of a service sector (hospital) building, either as an exterior skin, or as an enclosing component within the façade interior. The main contribution of this research is the characterization of the thermo-physical and mechanical properties of a new prefabricated panel made with recycled materials. The full characterization of the properties of these new materials is presented and discussed. The new prefabricated panel demonstrates adequate thermo-mechanical characteristics as a substitute for traditional materials, while improving the sustainability of the building. As a secondary objective, the energy behaviour of the new panels when integrated in a real building is presented by means of a case study simulation. The use of computational thermal simulation confirmed that the properties of the prefabricated block influenced the annual thermal demand of the building for heating and cooling. Improvements to the thermal inertia of the building envelope were also confirmed with the inclusion of PF waste, giving the mortar an energy performance that was similar to conventional materials, in such a way that its use in façade construction may be validated, in addition to its environmental benefits, due to it having been manufactured with critical recycled industrial waste such as EAF slag and PF, thereby contributing to both the circular economy and sustainable development.

Comparative waste management options for rigid polyurethane foam waste in Thailand

Abstract This research assesses the appropriate options for managing rigid polyurethane waste (RPUW) remaining from refrigerator/freezer dismantling in Thailand by analyzing the impacts on environment, energy and economic aspects. There are four options for RPUW management: option 1 – landfill; option 2 – incineration; option 3 – hydrolysis + landfill; and option 4 – production of lightweight concrete (LWC) mixed with RPUW (LWC-RPUW). From environmental and energy perspectives using Life cycle assessment (LCA) by Simapro software, the results showed that option 4 had the lowest human toxicity, followed by option 3, option 1 and option 2, respectively. On the other hand, option 1 had the lowest climate change and fossil depletion impacts, followed by option 2, option 3 and option 4, respectively. However, without considering energy consumption during the use phase of LWC as wall material in building, option 4 has the least energy and environmental impact. Regarding economic impact, option 4 is the only one option that can make a profit, and its net present value (NPV) is positive. In other words, it is worth refrigerator recyclers investing in a LWC-RPUW production plant. Option 4 is feasible to perform practically without subsidizing from any organization, while the other options are costly to carry out. To promote option 4, which is more appropriate considering all three kinds of impact studied here, it will be necessary to improve option 4 in terms of the insulation properties of the LWC-RPUW products to reduce the environmental impact from energy consumption during the product use phase.

Utilization of rigid polyurethane foam waste in removal of uncontrolled releases of hazardous substances

In 2017 in Poland 12522 incidents involving hazardous substances were recorded, of which 23 have been classified as large and very large. Apart from the share of carbon monoxide, most of them concerned uncontrolled petroleum product releases. In the same year over 427 m3 of foaming agents were used. Consequently, an extremely important issue at the intervention level is the efficient and safe removal of the resulting pollution. Tests of maximal absorption proprieties with the use of the modified Westinghouse method executed on a wide range of industrially used diverse industrial toxic substances and various classes of waste of firefighting foam agents have demonstrated substantial usability of rigid polyurethane foam waste. The obtained maximal theoretical sorptivity were within the range of 1.87-5.11 kg.kg-1. It has also been proven that absorption proprieties in relation to waste firefighting foaming agents were reduced. However, the maximum absorption proprieties of the tested rigid polyurethane foam waste are much higher than those for standard mineral sorbents used in rescue operations, which indicates a high potential for their practical use for emergency services.

Performance Studies of Lightweight Concrete Mixtures Made with Rigid Polyurethane Foam Wastes

This paper describes the results of some studies on the properties of lightweight expanded concrete mixtures made with rigid polyurethane foam waste. Experimental study on the mechanical properties of polyurethane foam waste mixed with concrete shrinkage performance and the relationship between packing density and absolute density. The results showed that: Polyurethane foam plastic waste can be used in the preparation of lightweight concrete, the strength with the state standards, and packing density and concrete absolute density with reference line between sex. Drying shrinkage comply with Selih and Bremner lightweight concrete water content to evolution.

Transient Thermal Response of Lightweight Cementitious Composites Made with Polyurethane Foam Waste

The development of low-cost lightweight aggregate (LWA) mortars and concretes presents many advantages, especially in terms of lightness and thermal insulation performances of structures. Low-cost LWA mainly comes from the recovery of vegetal or plastic wastes. This article focuses on the characterization of the thermal conductivity of innovative lightweight cementitious composites made with fine particles of rigid polyurethane (PU) foam waste. Five mortars were prepared with various mass substitution rates of cement with PU-foam particles. Their thermal conductivity was measured with two transient methods: the heating-film method and the hot-disk method. The incorporation of PU-foam particles causes a reduction of up to 18 % of the mortar density, accompanied by a significant improvement of the thermal insulating performance. The effect of segregation on the thermal properties of LWA mortars due to the differences of density among the cementitious matrix, sand, and LWA has also been quantified. The application of the hot-disk method reveals a gradient of thermal conductivity along the thickness of the specimens, which could be explained by a non-uniform repartition of fine PU-foam particles and mineral aggregates within the mortars. The results show a spatial variation of the thermal conductivity of the LWA mortars, ranging from 9 % to 19 %. However, this variation remains close to or even lower than that observed on a normal weight aggregate mortar. Finally, a self-consistent approach is proposed to estimate the thermal conductivity of PU-foam cement-based composites.

Valorization of coarse rigid polyurethane foam waste in lightweight aggregate concrete

This study examines the mechanical properties and the durability parameters of lightweight aggregate concretes (LWAC) incorporating rigid polyurethane (PUR) foam waste as coarse aggregates (8/20 mm). The influence of both the increasing incorporation of FUR foam waste and the presence of superplasticizer on the workability, bulk density, mass loss, drying shrinkage, compressive strength, dynamic modulus of elasticity, total porosity, gas permeability and chloride diffusion coefficient of the different concretes, has been investigated and analyzed. The results showed that the use of FUR foam waste enabled to reduce by 29-36% the dry density of concrete compared to that of the normal weight concrete (made without foam waste). The reduction of density was due to the increase of total porosity in the lightweight concretes, which also induced higher gas permeability and chloride diffusion coefficient. These negative effects on durability of concrete were lowered by improving the characteristics of the cementitious matrix. The mechanical properties of the LWAC ranged between 8 and 16 MPa for the compressive strength and between 10 and 15 GPa for the dynamic modulus of elasticity; the concrete mixture with the higher performances almost satisfied the mechanical and density criteria of structural lightweight concrete. These results consolidate the idea of the use of PUR foam waste for the manufacture of lightweight aggregate concretes.