Properties Of Rigid Polyurethane Foams Research Articles

Study on the Cross-Scale Effects of Microscopic Interactions and Mechanical Properties of Rigid Polyurethane Foam Driven by Negative-Temperature Environments

In order to investigate the cross-scale effects of the interaction between the hard and soft segments of stiff polyurethane foam on the material’s mesoscopic pore structure and macroscopic compression characteristics in various negative-temperature environments, this paper used molecular dynamics to calculate the interaction differences between hard and soft segments in different negative-temperature environments. The effects of various negative-temperature settings on the cell structure of stiff polyurethane foam were investigated using scanning electron microscopy and Image J software. Finally, macro experiments were used to determine the influence of a negative-temperature environment on the characteristics of stiff polyurethane foam (such as compressibility). The molecular simulation calculation results show that in a negative-temperature environment, decreasing temperature gradually increases the interaction between hard segment molecules and soft segment molecules, resulting in an increase in the molecules’ modulus and cohesive energy density. The scanning electron microscope results reveal that a negative-temperature environment gradually increases the pore diameter of stiff polyurethane foam. The compression experiment findings demonstrate that, for the same service duration, the compressive strength in the −20 °C environment is 27.53% higher than that in the 0 °C environment. The study’s findings reveal a microscopic mechanism for the following receiving alterations and toughness enhancement of rigid polyurethane foam throughout service in negative-temperature conditions.

Axial crushing responses and energy absorption characteristics of aluminum honeycombs filled with graphene oxide modified rigid polyurethane foam

This study aims to explore the potential application of hollow glass beads (HGB) compounded with graphene oxide (GO, HGB@GO) to improve the mechanical properties of rigid polyurethane foam (RPUF). This HGB@GO/RPUF composite is considered a potential filler for reinforcing aluminum honeycomb (AH). A characterization of the chemical structure and surface morphology of HGB@GO was conducted, as well as the analysis of its effect on the compression properties of the foam. The compressive strength of HGB@GO/RPUF (4 wt. %) is 146.17% higher than that of pure RPUF. This study also compared the deformation modes of AH and foam-filled honeycomb (F-AH) structure under axial crushing. The interaction effects between the foam and AH were also analyzed. The results indicated that the RPUF improves the compressive capacity and deformation stability of the AH through its good compression properties and interaction with the aluminum foil. The use of HGB@GO/RPUF further enhances the energy absorption characteristics of the F-AH. In comparison with the pure RPUF-AH, the total and specific energy absorption of the HGB@GO/RPUF (4 wt. %)-AH increase by 74.65% and 44.98%, respectively. This work demonstrates that the prepared HGB@GO can enhance the mechanical properties of RPUF, and HGB@GO/RPUF-AH is expected to be a desirable energy-absorbing device.

Study of the possibility of regulating the properties of rigid polyurethane foams with oligomeric furan-containing ammonium bases

Hydroxyl-containing ammonium oligomers containing a furan heterocycle were synthesized. Their use as modifiers of properties of rigid polyurethane foams makes it possible to improve technological parameters of molding and physical and mechanical properties of urethane foams. The quaternary ammonium compounds used were found to act as "soft" catalysts, cross-linking agents and flame retardants.

Thermal insulation properties of rigid polyurethane foam modified with fly ash- a comparative study

Limitations in natural resource availability have a significant impact on prices of thermal energy. As a result, a growth of interest in the technology of insulation materials is observed. The paper presents a comparative analysis of rigid polyurethane foams, which are widely used as insulation materials. Rigid polyurethane foam with 10 wt.% addition of coal fly ash is compared to a reference foam, without any addition. The thermal conductivity coefficient of polyurethane materials was determined by the Hot Disk device. Heat transfer for both types of foams was modelled. As a result of the numerical modelling, the temperature field for the wall was obtained. The results of the computations have shown differences in energy losses. Conducted analyses demonstrate that the modified polyurethane foam (with the addition of coal fly ash) performs better as an insulation material. The reduction of heat requirement is 2.9%. An environmental analysis of the insulation materials was also carried out. Using the SUBRAW index method it was calculated that embodied energy and the carbon footprint are lower in the case of the modified polyurethane compared to the unmodified foam.

Utilization of Sunflower Husk Ash in the Production of Polyurethane Materials

Energy produced from waste biomass is more environmentally friendly than that produced from fossil resources. However, the problem of managing waste from the thermal conversion of biomass arises. The overarching goal of this article was to propose a method of utilizing biomass ash (sunflower husk) as a filler that positively affects the properties of rigid polyurethane foams. The scope of the presented research is to obtain and characterize rigid polyurethane foams (RPUFs) with the addition of two types of fillers: sunflower husks (SHs) and sunflower husk ash (SHA). First, an analysis of the fillers was carried out. The carbon content of SHs (C~49%) was ten times higher in comparison to SHA’s carbon content (C~5%). The morphology of the fillers and the particle size distribution were determined, which showed that in the case of SHs, particles with a size of 500–1000 µm predominated, while in SHA, the particles were 1–20 µm. The content of inorganic compounds was also determined. Potassium and calcium compounds were the most abundant in both fillers. The second part of the research was the analysis of polyurethane materials with the addition of fillers. The obtained results indicate that filler addition had a positive effect on the dimensional stability of the foams by eliminating the risk of material shrinkage. The biodegradation process of polyurethane materials was also carried out. The reference foam weight loss after 8 weeks was ~10%, while the weight loss of the foam containing SHA was over 28%. Physical and mechanical properties, cell structure, and thermal stability tests were also carried out. The use of bio-waste fillers creates a possibility for the partial replacement of petrochemical products with environmentally friendly and recycled materials, which fits into the circular economy strategy.

The effects of a phosphorus/nitrogen-containing diphenol on the flammability, thermal stability, and mechanical properties of rigid polyurethane foam

The effects of a phosphorus/nitrogen-containing diphenol on the flammability, thermal stability, and mechanical properties of rigid polyurethane foam

Effect of Selected Bio-Components on the Cell Structure and Properties of Rigid Polyurethane Foams.

New rigid polyurethane foams (RPURFs) modified with two types of bio-polyols based on rapeseed oil were elaborated and characterized. The effect of the bio-polyols with different functionality, synthesized by the epoxidation and oxirane ring-opening method, on the cell structure and selected properties of modified foams was evaluated. As oxirane ring-opening agents, 1-hexanol and 1.6-hexanediol were used to obtain bio-polyols with different functionality and hydroxyl numbers. Bio-polyols in different ratios were used to modify the polyurethane (PUR) composition, replacing 40 wt.% petrochemical polyol. The mass ratio of the used bio-polyols (1:0, 3:1, 1:1, 1:3, 0:1) affected the course of the foaming process of the PUR composition as well as the cellular structure and the physical and mechanical properties of the obtained foams. In general, the modification of the reference PUR system with the applied bio-polyols improved the cellular structure of the foam, reducing the size of the cells. Replacing the petrochemical polyol with the bio-polyols did not cause major differences in the apparent density (40-43 kg/m3), closed-cell content (87-89%), thermal conductivity (25-26 mW⋅(m⋅K)-1), brittleness (4.7-7.5%), or dimensional stability (<0.7%) of RPURFs. The compressive strength at 10% deformation was in the range of 190-260 and 120-190 kPa, respectively, for directions parallel and perpendicular to the direction of foam growth. DMA analysis confirmed that an increase in the bio-polyol of low functionality in the bio-polyol mixture reduced the compressive strength of the modified foams.

Preparation and Effect of Methyl-Oleate-Based Polyol on the Properties of Rigid Polyurethane Foams as Potential Thermal Insulation Material.

Recently, most of the commercial polyols used in the production of rigid polyurethane foams (RPUFs) have been derived from petrochemicals. Therefore, the introduction of modified palm oil derivatives-based polyol as a renewable material into the formulation of RPUFs is the focus of this study. A palm oil derivative-namely, methyl oleate (MO)-was successfully modified through three steps of reactions: epoxidation reaction, ring-opened with glycerol, followed by amidation reaction to produce a bio-based polyol named alkanolamide polyol. Physicochemical properties of the alkanolamide polyol were analyzed. The hydroxyl value of alkanolamide polyol was 313 mg KOH/g, which is suitable for producing RPUFs. Therefore, RPUFs were produced by replacing petrochemical polyol with alkanolamide polyol. The effects of alkanolamide polyol on the physical, mechanical and thermal properties were evaluated. The results showed that the apparent density and compressive strength increased, and cell size decreased, upon introducing alkanolamide polyol. All the RPUFs exhibited low water absorption and excellent dimensional stability. The RPUFs made with increased amounts of alkanolamide polyol showed higher thermal conductivity. Nevertheless, the thermal conductivities of RPUFs made with alkanolamide polyol are still within the range for thermal insulating materials (<0.1 W/m.K). The thermal stability of RPUFs was improved with the addition of alkanolamide polyol into the system. Thus, the RPUFs made from alkanolamide polyol are potential candidates to be used as insulation for refrigerators or freezers.

Study on properties of rigid polyurethane foam as a thermal building insulator at varied mixing conditions

The concept of zero-energy building is one of the promising ways to improve energy efficiency, resulting in the reduction of greenhouse gas emissions. The use of rigid polyurethane foam (RPUF) has been widely used as insulation material in building panels because of its excellent properties including light-weight, durability, and lower thermal conductivity. This study aimed to determine the effect of mixing conditions on the production of RPUF at varied mixing speeds (300, 500, 1000 rpm) corresponding to its density, mechanical, and insulation properties. It was observed that the well-defined physical structure of RPUF was obtained at the minimum mixing speed of 500 rpm. The foam density changed with the increasing mixing speed, from 39.8 kg/m3 at 500 rpm to 51.30 kg/m3 at 1000 rpm. This might be because of the possible loss of the blowing agent due to excessive mixing speed as noted by the constrained foam expansion and the shorter time for the free-rise process. The thermal insulation property of obtained RPUF was significantly lower than that of conventional building materials like concrete. This research is one of the key technologies to reduce the energy consumption for heating-cooling buildings and thus create a potential strategy for climate change mitigation.

Influence of Reactive Amine-Based Catalysts on Cryogenic Properties of Rigid Polyurethane Foams for Space and On-Ground Applications.

Rigid polyurethane (PUR) foams have outstanding properties, and some of them are successfully used even today as cryogenic insulation. The fourth-generation blowing agent Solstice® LBA and commercial polyols were used for the production of a low-density cryogenic PUR foam composition. A lab-scale pouring method for PUR foam preparation and up-scaling of the processes using an industrial spraying machine are described in this article. For the determination of the foam properties at cryogenic temperature, original methods, devices, and appliances were used. The properties at room and cryogenic temperatures of the developed PUR foams using a low-toxicity, bismuth-based, and low-emission amine catalyst were compared with a reference foam with a conventional tin-based additive amine catalyst. It was found that the values of important cryogenic characteristics such as adhesion strength after cryoshock and the safety coefficient of the PUR foams formed with new reactive-type amine-based catalysts and with the blowing agent Solstice® LBA were higher than those of the foam with conventional catalysts.

The influence of biowaste-based fillers on the mechanical and fire properties of rigid polyurethane foams

Increasing emphasis on the circular economy is driving the development of environmentally friendly rigid polyurethane foams (RPUFs). In this work, polyurethane foams were altered with an addition of fillers, i.e. sunflower husks, rice husks and buckwheat hulls at various weight ratios (5 wt%, 10 wt%, 15 wt%). The aim of the study was to investigate the influence of bio-fillers on the structure, mechanical properties, and thermal properties as well as dimensional stability, water absorption and apparent density of RPUFs. The obtained results indicated that foam modified with these types of fillers, compared to the reference foam, which did not contain fillers, has a higher apparent density (38–51 kg⋅m−3), lower water absorption (18–32%) and higher compressive strength (50–90 kPa). Moreover, the fire behaviour of the produced composites was investigated with the use of a cone calorimeter. The foam containing 5 wt% of rice hulls showed the highest resistance to fire. The obtained results show the possibility of introducing bio-fillers to polyurethane materials as ingredients which can enhance the properties of these materials.

Quantitative Analysis of Mechanical Strength of Three-Phase Rigid Polyurethane Foam Composites Immersed with Water

The mechanical properties of rigid polyurethane foam (PUF) will be significantly affected because of the existence of water when applied in dam repair and road maintenance. The related studies generally consider the effects of water and matrix on the mechanical properties of rigid PUF. However, PUF is a three-phase composite consisting of water, air, and matrix in practical engineering. Its mechanical properties are subject to the combined effects of these three composites at the same time. In this case, an improved three-phase viscoelastic model was proposed to quantify the effects of water, air, and matrix on the compressive mechanical behavior of rigid polyurethane foam immersed in water (WRPF). Based on the improved viscoelastic model and piecewise method, a compressive strength prediction model of WRPF was developed to describe the change of WRPF’s compressive strength during the full-service life. Then uniaxial compression tests and electron microscope tests were conducted to verify the rationality of the model. Results show that water and air have reinforcing effects on the compressive property of WRPF in the short-term, unsaturated absorption stage. In contrast, water has weakening effects on its compressive property in the long-term, saturated stage. Finally, at different stages of water absorption, a semitheoretical and empirical formula was developed from the prediction model and the experimental data from compressive tests.

Multifunctional Polyurethane Composites with Coffee Grounds and Wood Sawdust

Currently, the fundamental activity that will allow for the development of an economy with closed circulation is the management of food waste and production waste for the preparation of biocomposites. The use of waste materials of natural origin allows for the creation of innovative composites with improved physicochemical and functional properties. The present investigation concerns the use of coffee grounds (2.5-20 wt.%) and oak sawdust (2.5-20 wt.%) as effective fillers of rigid polyurethane foam. Innovative composite materials, previously indebted in the literature, were subjected to the necessary analyses to determine the application abilities: processing times, free density, water absorption, dimensional stability, mechanical properties (compressive strength), thermal conductivity, morphology, and flame resistance. The results with respect to the mechanical tests turned out to be the key. Increasing the number of coffee additives has a positive effect on the compressive strength. The addition of this filler in the range of 5-15 wt.% increased the compressive strength of the composites, 136-139 kPa, compared to the reference sample, 127 kPa. The key parameter analysed was thermal conductivity. The results obtained were in range of the requirements, that is, 0.022-0.024 W/m·K for all used amounts of fillers 2.5-20 wt.%. This is extremely important since these materials are used for insulation purposes. The results of the burning-behaviour test have confirmed that the addition of renewable materials does not negatively affect the fire resistance of the received foams; the results were obtained analogously to those obtained from the reference sample without the addition of fillers. The height of the flame did not exceed 17 cm, while the flame decay time was 17 s for the reference sample and the composite with coffee grounds and 18 s for the composite with oak sawdust. In this work, the practical application of bioorganic waste as an innovative filler for the insulation of flooded polyurethane foam is described for the first time. The introduction of fillers of natural origin into the polymer matrix is a promising method to improve the physicochemical and functional properties of rigid polyurethane foams. Composites modified with coffee grounds and sawdust are interesting from a technological, ecological, and economic point of view, significantly increasing the range of use of foam in various industries.

Acoustic Properties of Rigid Polyurethane Foam Mixed with Pet Bottle Wastes

Rigid closed-cell polyurethane foam is renowned for its outstanding sound absorption properties and its application as sound insulation panels. Studies show that mixing of rigid polyurethane foam with non-reactive filler materials during fabrication improves the sound absorption properties of the composite material. In this composite, foam was fabricated from polyol and isocyanate monomers with shredded pet bottle waste as a filler component. The percentages of pet wastes mixed with the polyurethane foam composites were varied by 0%, 10%, 15%, 20% and 25% of total weight. The measurement of sound absorption coefficient has been done using impedance tube technique. The results showed that the rigid polyurethane foam with 0% pet waste has poor acoustic absorption. Also, sound absorption coefficient results showed that a sample with higher amount of upto 20%pet bottle waste had better sound absorption even at higher frequencies. From this research it is clear that mixing of pet waste as a filler material upto 20% is ideal for fabricating sound absorption panels with better sound absorption average.

Properties of Rigid Polyurethane Foam Filled with Sawdust from Primary Wood Processing

In this study, the possibility of using sawdust, a by-product of primary wood processing, as a filler (WF) for rigid polyurethane (PUR) foams was investigated. The effects of the addition of 5, 10, 15 and 20% of WF particles to the polyurethane matrix on the foaming process, cell structure and selected physical-mechanical properties such as density, thermal conductivity, dimensional stability, water absorption, brittleness, compressive and bending strengths were evaluated. Based on the results, it was found that the addition of WF in the amount of up to 10% does not significantly affect the kinetics of the foam foaming process, allowing the reduction of their thermal conductivity, significantly reducing brittleness and maintaining high dimensional stability. On the other hand, such an amount of WF causes a slight decrease in the compressive strength of the foam, a decrease in its bending strength and an increase in water absorption. However, it is important that in spite of the observed decrease in the values of these parameters, the obtained results are satisfactory and consistent with the parameters of insulation materials based on rigid PUR foam, currently available on the market.

Synergistic effect of silica aerogels and hollow glass microspheres on microstructure and thermal properties of rigid polyurethane foam

Insulation materials with excellent thermal properties are pivotal components for the next-generation green building materials. In this study, several novel rigid polyurethane foam (RPUF) composites modified by silica aerogels and hollow glass microspheres (HGMs) were prepared. The microstructure, mechanical, physical and thermal properties of the specimens were characterized. The results showed that the addition of fillers changed the microstructure of RPUF. Furthermore, the thermal conductivity of rigid polyurethane foam filled with silica aerogels and HGMs (PUAH) decreased from 24.4 to 22.7 mW/mK, and the compressive strength of PUAH was 51.1% higher than that of pure RPUF. Thermogravimetric analysis (TGA) exhibited that the thermal stability of PUAH was improved, which was evidenced by the delayed thermal decomposition temperature. Notably, the results of cone calorimeter test (CCT) demonstrated that, compared with pure RPUF, the total heat release (THR) and total smoke production (TSP) of PUAH decreased by 23.2% and 21.6%, respectively. The above results proved that there was a synergistic effect of silica aerogels and HGMs in enhancing the various performance of RPUF composites.

Green rigid polyurethane foam from hydroxyl liquid natural rubbers as macro-hydroxyl polyols

The novel renewable source precursors from hydroxyl liquid natural rubbers (HLNRs) with various secondary hydroxyl content of 22% (HLNR22), 35% (HLNR35), and 50% (HLNR50) (or naming macro-hydroxyl polyols) were used to prepare rigid polyurethane foam. The aim of this study was to investigate the effect of hydroxyl content of HLNR precursors and the ratio of HLNRs and commercial polyols on physico-mechanical properties of rigid polyurethane foams in comparison to foams made from commercial polyols. The increase in hydroxyl content of HLNRs resulted in the foams with larger cell size while the increase in the HLNR portion caused a small and more uniform cell size, which is related to their density and compressive strength. Thermal stability of polyurethane foams was analyzed by thermogravimetric analysis and the results have demonstrated that the use of HLNR polyols improved thermal stability of polyurethane foams in comparison to commercial foam.

Nanocomposites of Rigid Polyurethane Foam and Graphene Nanoplates Obtained by Exfoliation of Natural Graphite in Polymeric 4,4'-Diphenylmethane Diisocyanate.

The influence of graphene nanoplates (GNPs) obtained by the ecofriendly exfoliation of natural graphite has been addressed on the mechanical and thermal insulating properties of rigid polyurethane foams (RPUFs). Few-layer GNPs with few defects were prepared in polymeric 4,4′-diphenylmethane diisocyanate (pMDI) under ultrasonication to obtain a GNP/pMDI dispersion. GNP/pMDI dispersions with different GNP concentrations were used to prepare RPUF nanocomposites via in situ polymerization. An important finding is that the GNP/pMDI dispersion exhibits lyotropic liquid crystalline behavior. It was found that the unique orientation of GNPs above the concentration of 0.1 wt% in the dispersion affected the mechanical and thermal insulation properties of the RPUF nanocomposites. GNP/RPUF nanocomposites with GNP concentrations at 0.2 wt% or more showed better thermal insulating properties than neat RPUF. The lyotropic liquid crystalline ordering of GNPs provides stable nucleation for bubble formation during foaming and prevents bubble coalescence. This decreases the average cell size and increases the closed cell content, producing GNP/RPUF nanocomposites with low thermal conductivity. Furthermore, GNPs incorporated into RPUF act as a barrier to radiant heat transfer through the cells, which effectively reduces the thermal conductivity of the resulting nanocomposites. It is expected that the nanocomposite of RPUF investigated in this study can be applied practically to improve the performance of thermal insulation foams.

Experimental study on the dynamic properties of rigid polyurethane foam in stress-controlled cyclic uniaxial tests

Frequent major earthquakes in Japan necessitate earthquake-resistant infrastructure. The dynamic deformation characteristics of rigid polyurethane foam, used as a lightweight embankment material, is examined in this study. The effect of the initial static stress on the shear modulus of single-layer samples was small, while the shear modulus of two-layer samples increased with increasing initial static stress. The damping ratio of single-layer samples converged to 4–5%, but decreased with increasing initial static stress up to 30 kPa in two-layer samples before increasing above 40 kPa. Results from cyclic uniaxial and triaxial tests were compared. The dynamic properties depended on restriction conditions and the deformation direction.

ВЛИЯНИЕ ФИЗИЧЕСКОГО ПЕНООБРАЗОВАТЕЛЯ НА СВОЙСТВА ЖЕСТКИХ ПЕНОПОЛИУРЕТАНОВ

The article discusses the properties of rigid polyurethane foams (PU foams) obtained with the use of various environmentally friendly physical foaming agents - cyclopentane, cycloisopentane mixtures (CIP), methylal, methyl formate and methyl tert-butyl ether. No significant differences were noted in the use of various blowing agents during technological samples free foaming. In the course of further research, it was confirmed that the physical and mechanical properties of the finished foam significantly depend on the type of gas in the closed cells of the material. Foams obtained with the use of hydrocarbon blowing agents have a fine-meshed structure without defects, cavities and voids. It has been established that in the case of foaming with cyclopentane and cycloisopentane compositions, the introduction of isopentane provides an increase in the strength of the finished foams in compression in the horizontal direction in accordance with the direction of foam rise. It is also noted that materials foamed with methylal and methyl formate have the lowest compressive strength values. A slight difference was also noted in the thermal conductivity of the foamed products. The lowest values of thermal conductivity in the present study were noted for foams based on cyclopentane and cycloisopentane mixtures. It was also of interest to establish the change in the thermal conductivity of finished products based on cyclopentane and CIP over time. Experimentally found that after 500 days the thermal conductivity of the samples increased and reached equal values. This effect is due to the diffusion of the foaming component molecules through the walls of the foam cells, as a result of which air with a much higher thermal conductivity coefficient diffuses into the cells. It was shown in a comparative analysis that the mixtures of polyurethane foam components have good fluidity in the case of cyclopentane and cycloisopentane use, which contributes to uniform filling of the mold and reduction of losses during pouring. Based on the work done, cycloisopentane mixtures can be recommended as foaming components in the production of polyurethane foam insulation.