Polyurethane Foam Formulations Research Articles

Application of Modified Seed Oils of Selected Fruits in the Synthesis of Polyurethane Thermal Insulating Materials.

The use of alternative raw material sources in polyurethane chemistry is necessary given the limited supply of fossil fuels, their rising prices and the concern for sustainability. The production of biopolyols from edible vegetable oils such as rapeseed oil, soybean oil or sunflower oil is often proposed. In order to avoid conflict with the global food economy, non-edible or waste oils are hoped to find application in chemical synthesis. The possibility of using oils from selected fruit seeds to obtain biopolyols is analyzed in this manuscript. Five biopolyols were obtained from watermelon, cherry, black currant, grape and pomegranate fruit seeds using the transesterification reaction of the oils with triethanolamine. Thermal insulating polyurethane foams were then obtained by replacing 75% of petrochemical polyol with the biopolyols in polyurethane systems. Based on an analysis of the foaming process, it was found that the incorporation of triethanolamine molecules into the biopolyols causes a catalytic effect. The use of such biopolyols allows eliminating the catalyst from a polyurethane foam formulation. The polyurethane biofoams obtained with the pomegranate-seed-based biopolyol were characterized by the highest content of closed cells (45 vol.%). The lowest content was found for the foams containing the currant-seed-based biopolyol (9%). The foams were characterized by thermal conductivity coefficients between 32 and 35 kW/m·K and densities of approximately 40 kg/m3. Good dimensional stability and compressive strength between 100 and 250 kPa make them suitable for use in construction.

From Bioresources to Thermal Insulation Materials: Synthesis and Properties of Two-Component Open-Cell Spray Polyurethane Foams Based on Bio-Polyols from Used Cooking Oil.

Open-cell spray polyurethane foams are widely used as highly efficient thermal insulation materials with vapor permeability and soundproofing properties. Unfortunately, for the production of commercial foams, mainly non-renewable petrochemical raw materials are used. The aim of this study was to determine the possibility of completely replacing petrochemical polyols (the main raw material used in the synthesis of polyurethanes, alongside isocyanates) with bio-polyols obtained from used cooking oils, classified as waste materials. The research consisted of three stages: the synthesis of bio-polyols, the development of polyurethane foam systems under laboratory conditions, and the testing of developed polyurethane spray systems under industrial conditions. The synthesis of the bio-polyols was carried out by using two different methods: a one-step transesterification process using triethanolamine and a two-step process of epoxidation and opening oxirane rings with diethylene glycol. The obtained bio-polyols were analyzed using gel chromatography and nuclear magnetic resonance spectroscopy. The developed polyurethane foam formulations included two types of fire retardants: halogenated tris(1-chloro-2-propyl) phosphate (TCPP) and halogen-free triethyl phosphate (TEP). In the formulations of polyurethane systems, reactive amine catalysts were employed, which become incorporated into the polymer matrix during foaming, significantly reducing their emission after application. The foams were manufactured on both a laboratory and industrial scale using high-pressure spray machines under conditions recommended by commercial system manufacturers: spray pressure 80-100 bar, component temperature 45-52 °C, and component volumetric ratio 1:1. The open-cell foams had apparent densities 14-21.5 kg/m3, thermal conductivity coefficients 35-38 mW/m∙K, closed-cell contents <5%, water vapor diffusion resistance factors (μ) <6, and limiting oxygen indexes 21.3-21.5%. The properties of the obtained foams were comparable to commercial materials. The developed polyurethane spray systems can be used as thermal insulation materials for insulating interior walls, attics, and ceilings.

Exploring urea hard segment morphology and phase separation behavior in flexible polyurethane foam formulations: Water, lithium chloride and isocyanate structure effects

Flexible polyurethane foams (FPUFs) are versatile materials used in various applications due to their unique properties. Understanding the phase separation behavior in FPUFs is crucial for tailoring their properties to specific applications. In this study, we investigated FPUFs with varying levels of urea phase connectivity using small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray scattering (WAXS). We explored the effect of water, lithium chloride, and isocyanate structures on the phase separation behavior by employing these methods. An increase in water content in the FPUF formulation resulted in a higher amount of formed urea and larger globular size of urea aggregates. Incorporating LiCl into FPUF formulations demonstrated its ability to prevent hydrogen bond formation, leading to alterations in the urea phase. Moreover, we found that foams prepared with asymmetric diisocyanates showed difficulty in forming the urea phase, while foams prepared with symmetric and aliphatic diisocyanates readily formed the urea phase. Our study sheds light on the morphology of the urea phase, the packaging nature of the hard segment, and the hydrogen bonding behavior of the FPUFs. These findings contribute to a better understanding of phase separation in FPUFs and offer insights into tailoring their properties for specific applications.

Preparation and characterization of indoor heat blockage panel composites made of polyurethane-hybrid-foam-concrete and rice-husk-ash

The preferable properties of indoor heat blockage material for tropical environments are blocking outside heat without absorbing and storing it inside the blockage material, therefore studying the component and the composite properties are crucial. This study, therefore, aims to prepare and characterize a new hybrid foam concrete based on Rice Husk Ash (RHA) composite panels as an indoor building material called Hybrid Foam Panel (HFP). Polyurethane made of the combination of blended polyol (catalyst and surfactant) and diphenylmethane-4,4′-diisocyanate with a constant proportion was used as a matrix, while white Portland cement and RHA with various compositions were used as fillers. The formation of polyurethane foam and related chemical reactions are confirmed and RHA in HFP composition gave significant roles in composite properties. HFP made with the right constituent composition caused much lower thermal conductivity (down to 0.22 W/mK) than the control, blocked the IR radiation heat, and it has moderate compressive strength. HFP with RHA content in consolidated parameters shows a compressive strength of 7.25–12.37 MPa; densities of 1216–1351 kg/m3 and a porosity of 62%. HFP also stands for heat at least 300 °C, thereby it is a potential interior solar heat blockade, especially in the tropical region.

Limits of Performance of Polyurethane Blowing Agents

A MATLAB program was developed to simulate urethane-forming reactions by solving over a dozen differential equations, energy balance, mass balance, and constitutive equations simultaneously. The simulation program was developed for half a decade to simulate the basic kinetics of polyurethane reactions and more complex phenomena that cannot be obtained in laboratories. In the current investigation, the simulation is applied to determine the limits of the performance of polyurethane foam formation. n-pentane, cyclohexane, and methyl formate were used as physical blowing agents, and water was used as a chemical blowing agent. The simulation code increases the accuracy of the results and makes the foam performance process less time- and money-consuming. Specifically, the MATLAB code was developed to study the impact of physical and chemical blowing agents at different loadings on the performance of rigid polyurethane foams. Experimental data were used to validate the simulation results, including temperature profiles, height profiles, and the tack-free time of urethane foam reactions. The simulation results provide a window for the proper type and the optimum amount range of different physical and chemical blowing agents.

Modeling the Formation of Rigid Polyurethane Foams Using Hydrofluorolefin as Expanding Agent

AbstractPolyurethanes are probably the most versatile among polymers of greater industrial use due to the possibility of being produced in a wide range of density, hardness, and mechanical properties and through different conversion processes. Its synthesis involves a great variety of raw materials and proportions between them. A mathematical model that describes the polyurethane foam formation can be very useful for the development of formulations and in the definition of the processing conditions, avoiding great consumption of time and errors in the development and experiments. The present work studies this process using industrial formulation. The kinetic parameters of the reaction between polyol with isocyanate are determined calorimetrically using the adiabatic temperature rise method, obtaining the values of activation energy 22.2 kJ mol−1 and heat of reaction 91.8 kJ mol−1. Data liquid–vapor equilibrium of the hydrofluorolefin blowing agent in a polyol mixture are obtained and treated with Flory–Huggins model with good agreement with experimental data (deviation of 1.6%). The mathematical model is satisfactory to describe the expanding process in a pilot scale, under different conditions.

The thermal and combustion properties of soybean oil phosphate-based polyurethane foam composites containing polyol of etidronic acid

In this work, a phosphorus-containing soybean oil-based polyol (PSOP) was successfully synthesized from epoxidized soybean oil by a ring-opening reaction with dibutyl phosphate. A phosphorous polyol (HEDP-PO) was synthesized by polymerization between 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and propylene oxide (PO). The two new polyols were used together in the formation of flame-retardant polyurethane foams (FRPUF), which depicted good thermal stability and flame retardancy performance. The addition of PSOP/HEDP-PO polyols resulted in a reduction of cell size and an increasement of cell numbers of PUF composites, whose apparent density was observed to increase. Besides, the LOI value of PUF-80 could reach 23.7% and satisfy the V-0 rating in the vertical burning test. The cone calorimeter test showed a reduction in the heat release rate from 395 kW/m2 to 251 kW/m2 and the total heat release from 24.9 MJ/m2 to 18.0 MJ/m2. Polyurethane foam exhibited good flame retardancy because PSOP/HEDP-PO played a great free radical quenching effect in the gas phase by releasing the PO* and PO2* free radicals. Meanwhile, a more dense and complete carbon layer was formed to cut off the transfer of heat and oxygen between the matrix and the ambient.

Impact of Various Catalysts on Transesterification of Used Cooking Oil and Foaming Processes of Polyurethane Systems.

The search for new sources of raw materials that can be used in the synthesis of polyurethanes and other polymer groups is extremely important. Currently, according to the principles of green chemistry and a circular economy, waste materials with a high reuse potential are being sought. This article presents a way of obtaining used-cooking-oil-based compounds capable of participating in the reaction of polyurethane creation. The transesterification reaction can be carried out using a variety of homo- and heterogeneous acid or base catalysts. Here, we looked at the impact of selected catalysts on the course of transesterification reactions, the composition of the post-reaction mixture and the possibility of using the products in polyurethane foam synthesis. The raw materials and the products were analyzed by means of gel permeation chromatography, FTIR spectroscopy and 1H NMR. The polyurethane foam formation process was analyzed using a FOAMAT® apparatus.

A Review of Research on the Effect of Temperature on the Properties of Polyurethane Foams.

Temperature is one of the main factors affecting the properties of polyurethane foams, and there are large differences in the mechanical properties of polyurethane foams at different temperatures. To understand the effect of temperature on the mechanical properties of polyurethane foams and to provide a theoretical basis for the application of polyurethane foams in extreme environments, this paper systematically describes the research on the effect of mold temperature, raw material temperature, and environmental temperature on the microstructure and mechanical properties of polyurethane foams in the formation and service stages of rigid polyurethane foams by domestic and foreign scholars, and summarizes the effect of temperature on the mechanical properties of polyurethane foams and the mechanism of action. A review of the literature shows that the effect of different temperatures on the mechanical properties of polyurethane foams can be summarized. The literature review shows that there are certain changes in the foaming process, pore structure, and mechanical properties of polyurethane foams at different temperatures, and the increase in temperature generally leads to the increase in pore size, decrease in density, and decrease in mechanical properties of polyurethane foams.

Population balance modeling of polyurethane foam formation with pressure‐dependent growth kernel

AbstractPolyurethane foams are widely used materials often chosen for their useful characteristics such as low thermal conductivity, ease of application, and high strength‐to‐weight ratios. Computational models are needed to predict the dynamics of the flow and expansion, and the resulting material properties, to improve manufacturing processes. In this paper, a model for PMDI, a water‐blown polyurethane foam, is presented. By extending a kinetics‐based approach by adding bubble‐scale information via a population balance equation (PBE) using the quadrature method of moments, we can track bubble size distributions during foaming. We present results from a three‐dimensional computational fluid dynamics model using arbitrary Lagrangian–Eulerian interface tracking implemented in finite element software. The model compares favorably with experimental data, including dynamics, bubble distributions measured by both camera and diffusion wave spectroscopy, and post‐test bubble size from scanning electron microscopy and density measurements from x‐ray computed tomography.

Polyurethane Foam Composites Reinforced with Renewable Fillers for Cryogenic Insulation.

Sawdust, microcellulose and nanocellulose and their silanized forms were used to reinforce rigid polyurethane (PU) foam composites. The concentration of fillers was varied in the range of 0.5–1.5%. For rigid PU foam formulations, three polyols from recycled and renewable materials were used, among other components. Polyols were obtained from rapeseed oil, tall oil fatty acids and recycled polyethylene terephthalate. As rigid PU foam composites in literature have been described as appropriate thermal insulation material, the appliance of obtained composites for cryogenic insulation was investigated by determining the various physical-mechanical properties of composites. The physical-mechanical properties, such as the modulus of elasticity, compressive and tensile strength in both 293 K and 77 K, adhesion measurements with and without cryo-shock, apparent density, thermal conductivity coefficient, and safety coefficient were measured. The results showed that the addition of fillers did not give a significant improvement of characteristics.

Nanoparticles Addition in PU Foams: The Dramatic Effect of Trapped-Air on Nucleation.

To determine the effect of nanoclays and trapped air on the formation of rigid polyurethane foams, three different production procedures were used. To study the influence of mixing at atmospheric pressure, two approaches were carried out employing either an electric or a magnetic stirrer. The third approach was executed by mixing under vacuum conditions with magnetic stirring. The samples thus obtained were characterized, and the effect of trapped air into the reactive mixtures was evaluated by analyzing the cellular structures. Different levels of trapped air were achieved when employing each manufacturing method. A correlation between the trapped air and the increase in the nucleation density when nanoclays were added was found: the cell nucleation density increased by 1.54 and 1.25 times under atmospheric conditions with electric and magnetic stirring, respectively. Nevertheless, samples fabricated without the presence of air did not show any nucleating effect despite the nanoclay addition (ratio of 1.09). This result suggests that the inclusion of air into the components is key for improving nucleation and that this effect is more pronounced when the polyol viscosity increases due to nanoclay addition. This is the most important feature determining the nucleating effect and, therefore, the corresponding cell size decreases.

Advances in Low-Density Flexible Polyurethane Foams by Optimized Incorporation of High Amount of Recycled Polyol.

An industrially manufactured recycled polyol, obtained by acidolysis process, was for the first time proved to be a possible replacement of the reference fossil-based polyol in a low-density formulation suitable for industrial production of flexible polyurethane foams. The influence of increasing recycled polyol amounts on the properties of the polyurethane foam has been studied, also performing foam emission tests to evaluate the environmental impact. Using 10 pbw recycled polyol in the standard formulation, significant differences of the physical properties were not observed, but increase of the recycled polyol amount to 30 pbw led to a dramatic decrease of the foam air flow and a very tight foam. To overcome this drawback, N,N′-bis[3-(dimethylamino)propyl]urea was selected as tertiary amine catalyst, enabling the preservation of foam properties even at high recycled polyol level (30 pbw). Foam emission data demonstrated that this optimized foam formulation also led to an important reduction of volatile organic compounds. The results open the way for further optimization studies in low-density flexible polyurethane foam formulations, to increase the reutilization of the polyurethane waste and reduce the amount of petroleum-based raw materials.

Vegetable Fillers and Rapeseed Oil-Based Polyol as Natural Raw Materials for the Production of Rigid Polyurethane Foams.

The reported study concerns the introduction of renewable raw materials into the formulation of rigid polyurethane foams in the quest for the sustainable development of polymer composites. In this study, rigid polyurethane foam composites were prepared using 75 wt.% of rapeseed oil-based polyol and 15 parts per hundred parts of polyol (php) of natural fillers such as chokeberry pomace, raspberry seeds, as well as hazelnut and walnut shells. The influence of the used raw materials on the foaming process, structure, and properties of foams was investigated using a FOAMAT analyzer and a wide selection of characterization techniques. The introduction of renewable raw materials limited reactivity of the system, which reduced maximum temperature of the foaming process. Moreover, foams prepared using renewable raw materials were characterized by a more regular cell structure, a higher share of closed cells, lower apparent density, lower compressive strength and glass transition temperature, low friability (<2%), low water absorption (<1%), high dimensional stability (<±0.5%) and increased thermal stability. The proper selection and preparation of the renewable raw materials and the rational development of the polyurethane recipe composition allow for the preparation of environmentally-friendly foam products with beneficial application properties considering the demands of the circular economy in the synthesis of rigid foams.

Monitoring the formation of polyurethane foams with an infrared camera: Classroom activity

Foams prepared with polyurethanes (PU), a polymer with units in the main chain joined by urethane linkages, are commonly used in isolation panels, seals, automative seats, and bedding. The reaction causing the formation of polyurethane foams is a conventional, yet spectacular, way to attract the attention of polymer chemistry students. Infrared cameras are a relatively inexpensive apparatus that allow for semi-quantitatively temperature monitoring at the surface of objects. Because the formation of polyurethane is exothermic, the polymerization reaction and the expansion of the foam can be easily detected by an infrared camera. Information such as volume expansion, maximum temperature, temperature distribution in time and space, and reaction time can be retrieved from short videos. These data can be correlated and discussed in relationship with the reactivity of the components for synthesizing the foam. The primary goal of this activity was to investigate the exothermic reaction of polyurethane foam using an infrared camera which has been successfully used for monitoring the exothermic formation of polyurethane foams. These values can be discussed in term of reactivity of isocyanates (aromatic and aliphatic/cycloaliphatic) for a given formulation of polyols. The highly visual content of such experiments is attractive for children and students. Chemicals for performing the experiments can be donated either individually or as ready sets (“polyols”) from the industry. It is anticipated that the investment required for buying the infrared camera can be redeemed by using it for other types of exo- or endothermic reactions and for teaching heat transfer in physics class.

Effects of Nucleating Agent on the Thermal Conductivity and Creep Strain Behavior of Rigid Polyurethane Foams Blown by an Environment-Friendly Foaming Agent

The effects of liquid-type additive, methoxynonafluorobutane, on the morphology, thermal conductivity, creep strain, and mechanical strength of polyurethane (PU) foams with an environment-friendly foaming agent, hyrdofluoroolefin, were investigated. The methoxynonafluorobutane under the trade name of NOVEC likely acted as a nucleating agent during the formation of PU foams. When NOVEC was added in the amount of 3 parts per hundred polyol by weight (php), the cell size of the foam was minimal, and the cell size distribution was relatively uniform. At the NOVEC content of 3.0 php, the thermal conductivity of the PU foams was also minimal. This decrease in thermal conductivity was due to the smaller cell size of the foams lowering their thermal conductivity. At 3.0 php NOVEC content, the creep strain of the PU foams was minimal being 0.29% at 1,000 h. At 3.0 php NOVEC, the estimated creep strain of the PU foam exhibited the lowest creep strain of 3.47% at 50 years. As a result, at 3.0 php NOVEC content, the cell wall was relatively less fractured, resulting in a small deformation of the PU foam. These results suggest that the main factors in improving the thermal insulation properties and stability of the PU foams are smaller cell size and narrow cell size distribution.

Bio-Degradable Polyurethane Foams Produced by Liquefied Polyol from Wheat Straw Biomass.

In the present work, an abundant and unused residue (wheat straw) has been employed to synthesize a polyol as a substituent of castor oil in polyurethane foams. The liquefied product showed excellent properties for the proposed application. Castor oil was substituted with up to 50% wheat straw polyol in the formulation of polyurethane foams, which were prepared using two different isocyanates (methylene diphenyl diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI)). The evaluation of physical, mechanical, and thermal properties of the foams revealed that these materials can successfully be formed with up to 40% wheat straw polyols since all the results were improved. Moreover, at this polyol concentration, the morphology of the foams was presented as a compact and ordered structure. Following this trend, the foams showed excellent biodegradability at 30 days (5.60 and 7.31% for TDI and MDI foams, respectively) and 60 days (8.49 and 9.88% for TDI and MDI foams, respectively) in the soil media tests carried out. Thus, the materials prepared in this work can be proposed for agricultural applications such as use in plant nurseries.

Recovery of Flexible Polyurethane Foam Waste for Efficient Reuse in Industrial Formulations

Ester polyurethane (PU) foam waste was reacted at atmospheric pressure in an autoclave and using microwaves with diethylene glycol (DEG) at different PU/DEG ratios in the presence of diethanolamine as a catalyst to find the glycolysis conditions that allow for the improved recovery of the PU foam waste and enable the recycling of the whole glycolysis product in foam formulations suitable for industrial application. The recycled polyol was characterized by dynamic viscosity, hydroxyl number, water content, and density, while thermal stability was assessed using thermogravimetric analysis. In the PU foam formulation, 1% and 5% of the glycolyzed material was reused. The relationship between the reuse level of the recycled polyol and the physical properties of the foam was thoroughly investigated. It was observed that both hardness and air flow decreased with increasing recycled polyol content, particularly for the polyester type foam, while tensile strength and compression strength increased. Depending on the amount of recycled polyol and catalyst used, polyether-based foams could be obtained with a low air permeability, needed in special applications as sealed foams, or with higher air permeability desirable for comfort PU foams. The results open the way for further optimization studies of industrial polyurethane foam formulations using a glycolysis process without any separation stage.

Hybrid Structures Made of Polyurethane/Graphene Nanocomposite Foams Embedded within Aluminum Open-Cell Foam

This paper focuses on the development of hybrid structures containing two different classes of porous materials, nanocomposite foams made of polyurethane combined with graphene-based materials, and aluminum open-cell foams (Al-OC). Prior to the hybrid structures preparation, the nanocomposite foam formulation was optimized. The optimization consisted of studying the effect of the addition of graphene oxide (GO) and graphene nanoplatelets (GNPs) at different loadings (1.0, 2.5 and 5.0 wt%) during the polyurethane foam (PUF) formation, and their effect on the final nanocomposite properties. Globally, the results showed enhanced mechanical, acoustic and fire-retardant properties of the PUF nanocomposites when compared with pristine PUF. In a later step, the hybrid structure was prepared by embedding the Al-OC foam with the optimized nanocomposite formulation (prepared with 2.5 wt% of GNPs (PUF/GNPs2.5)). The process of filling the pores of the Al-OC was successfully achieved, with the resulting hybrid structure retaining low thermal conductivity values, around 0.038 W∙m−1∙K−1, and presenting an improved sound absorption coefficient, especially for mid to high frequencies, with respect to the individual foams. Furthermore, the new hybrid structure also displayed better mechanical properties (the stress corresponding to 10% of deformation was improved in more than 10 and 1.3 times comparatively to PUF/GNPs2.5 and Al-OC, respectively).

High Functionality Bio-Polyols from Tall Oil and Rigid Polyurethane Foams Formulated Solely Using Bio-Polyols

High-quality rigid polyurethane (PU) foam thermal insulation material has been developed solely using bio-polyols synthesized from second-generation bio-based feedstock. High functionality bio-polyols were synthesized from cellulose production side stream—tall oil fatty acids by oxirane ring-opening as well as esterification reactions with different polyfunctional alcohols, such as diethylene glycol, trimethylolpropane, triethanolamine, and diethanolamine. Four different high functionality bio-polyols were combined with bio-polyol obtained from tall oil esterification with triethanolamine to develop rigid PU foam formulations applicable as thermal insulation material. The developed formulations were optimized using response surface modeling to find optimal bio-polyol and physical blowing agent: c-pentane content. The optimized bio-based rigid PU foam formulations delivered comparable thermal insulation properties to the petro-chemical alternative.