Mechanical Properties Of Polyurethane Foams Research Articles

Fire-Retardant Flexible Foamed Polyurethane (PU)-Based Composites: Armed and Charmed Ground Tire Rubber (GTR) Particles.

Inadequate fire resistance of polymers raises questions about their advanced applications. Flexible polyurethane (PU) foams have myriad applications but inherently suffer from very high flammability. Because of the dependency of the ultimate properties (mechanical and damping performance) of PU foams on their cellular structure, reinforcement of PU with additives brings about further concerns. Though they are highly flammable and known for their environmental consequences, rubber wastes are desired from a circularity standpoint, which can also improve the mechanical properties of PU foams. In this work, melamine cyanurate (MC), melamine polyphosphate (MPP), and ammonium polyphosphate (APP) are used as well-known flame retardants (FRs) to develop highly fire-retardant ground tire rubber (GTR) particles for flexible PU foams. Analysis of the burning behavior of the resulting PU/GTR composites revealed that the armed GTR particles endowed PU with reduced flammability expressed by over 30% increase in limiting oxygen index, 50% drop in peak heat release rate, as well as reduced smoke generation. The Flame Retardancy Index (FRI) was used to classify and label PU/GTR composites such that the amount of GTR was found to be more important than that of FR type. The wide range of FRI (0.94-7.56), taking Poor to Good performance labels, was indicative of the sensitivity of flame retardancy to the hybridization of FR with GTR components, a feature of practicality. The results are promising for fire protection requirements in buildings; however, the flammability reduction was achieved at the expense of mechanical and thermal insulation performance.

Variable pressure foaming on functionality and structural properties correlation in flexible polyurethane foam

The production cost of flexible polyurethane foam is significantly dependent on the cost of polyol, which constitutes the largest percentage of materials used in foam production with the characteristics to induce superior mechanical properties. Suitable fillers that are relatively cheap can be introduced in the foam as replacement for polyol. Certain compositions of filler have deleterious effect on some relevant mechanical properties of the foam. This paper investigates the Effects of Variable Pressure Foaming on functionality and structure property correlation in polyurethane foam using different percentage of inorganic fillers at different pressure in flexible polyurethane foam for the dual purposes of achieving sustained mechanical properties of polyurethane foam and reduction in the production cost by using the VPF Technique. Government restricts the use of certain auxiliary blowing agents like chlorofluorocarbon, trichloroethane, carbon dioxide, methylene chloride, acetone, pentane and water. VPF machine, in which we can make different densities of foam without adding auxiliary blowing agents which are banned in the Europe and other countries. These blowing agents are highly carcinogenic and ozone depletors, which are also harmful for human beings’ health and greenhouse effect. Water is a natural blowing agent, producers have tried to raise the water level substantially as an ABA agent, With the high exotherm associated with high water level formulations, there is so much urea formation that it is difficult to make flexible PU foams and inferior foam quality and durability, scorching in the foam and pose a fire hazard during foam manufacturing. For the rapid cooling process, it required excess Toluene Diisocyanate usage and allowed excess TDI vapour to be released into the atmosphere. In VPF, enclosed chamber and the exhaust is vented through carbon beds, it filters the TDI fumes which are very harmful for human beings’ health and for the environment. Foams can be achieved by foaming under vacuum, thus substantially reducing the water level and TDI usage. VPF technique offers a unique combination of environmental friendliness, superior product consistency and unique foam properties. It provides us with a platform for new product technology and a reliable process to meet the increasingly stringent environmental regulations.

Analysis of the effects of region and direction on the mechanical strength of polyurethane foams in white goods refrigerators

This research focuses on investigating the mechanical properties of polyurethane foam, specifically in the context of the refrigeration industry. Tensile, compression, and flexural tests were conducted to gather comprehensive data on the foam's mechanical behavior under various loading conditions. Samples were collected from different regions within a specific cabinet model to analyze the effects of region and direction of the foam growth on the foam's mechanical properties. The results revealed that samples collected from the top of the cabinet exhibited superior performance compared to those obtained from the bottom. The foam demonstrated isotropic behavior under compression, while exhibiting anisotropic behavior under tensile and flexure. When aligned parallel to the foam growth, the foam displayed slightly higher maximum stress in the tensile and flexural tests. However, the compression test showed comparable strength in both directions. These findings contribute to a better understanding and utilization of PU foam in various industrial sectors, particularly in refrigeration. The data obtained from this research can support the optimization of project designs and facilitate the development of more efficient and economically viable solutions.

Mechanical properties of polyurethane foam for potential application in the prevention and treatment of pressure ulcers

The viscoelastic property is a crucial parameter for evaluating the feasibility of the foam to be used as pressure relief. This work aims to perform experimental measurements to determine the dependence of the viscous behavior of polyurethane foam on density and energy dissipation. Experimental measurements were realized for three types of polyurethane foams with different densities soft, medium and hard. The compression tests at room temperature characterized the mechanical properties of these samples. Furthermore, the structures of the samples were characterized using scanning electron microscopy (SEM). A proportional relationship was observed between the density of polyurethane (PU) foam and the tolerated strength at 90% compression. This material has an excellent remanence (persistence) which showed by the creep experiments at constant stress (2, 5, 10 N) for 6 h. Young Modulus, relaxation time and dissipation coefficient (DE) were also calculated from the stress-strain curve. Moreover, softening behavior, which is responsible for pressure relief, was measured by a cyclic compression test. This paper assesses the capacity of polyurethane to effectively maintain interfacial pressure below the critical threshold of 32 mm of mercury, which represents a significant risk level for the development of pressure sores.

Enhanced effect of chloroprene on the mechanical properties of polyurethane foams

In this research, a new method to increase the mechanical properties of the low-density polyurethane foams (PUFS) has been described. Chloroprene rubber (CR) is used as reinforcing the mechanical properties of the foam. Polyurethane foam (PUF) containing CR (PUF/CR) and pure PUF were characterized by mechanical testing, Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Differential scanning calorimeter (DSC), Thermogravimetric analysis (TGA). The results of mechanical properties show the tensile strength of PUFS containing 0, 1, 2, 3, 4 and 5 wt% CR are 38.2, 42, 56.4, 61.48, 77.3 and 77.18 kPa, respectively. Also the morphological studies show by increasing the amount of CR in the foam structure, the foam cells are smaller and more closed.

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.

Investigation of the Epoxy Concentrations Effect on the Mechanical Properties of Polyurethane Foams

Thermosetting foam had a number of advantage in comparison with unfoamed polymer such as lightweights, higher specifics strength, and stiffness. In this work, preparations and characterizations of polymers foams from polyurethanes have carrying out by means of one shot methods for productions of microcellulars polymers that are using in the lower limp application. Many type of polyols (Local commercial market, Quickmast 110, and Quickmast 120) at equivalents ratios of (isocyanate:polyol) [1:1] mixing with 5 drops of distill water as chemicals blowing agent. Different amounts of epoxy resin [2.5, 5, 7.5, and 10 wt%] mixing with polyol using a magnetic stirrer for 30 min at 50 °C and 30 rpm. The hardener mixing with isocyanates in another container. These two solutions were mixing together, then water was added and mixing by hand to form polyurethane/ epoxy blend foam sample. The mechanical characteristics [hardness, tensile and compression] tests were achieved to display the effects of polyol type, epoxy concentration on the mechanical characteristics of the final product. The results of mechanical characteristics increasing with additions of epoxy resin at the best ratio is 7.5 wt%.

Construction of soft polyurethane cushioning composites based on integral fabric air layer: Reaching new levels in compression and cushioning behaviors

AbstractIn order to prepare a cushioning composite with good resilience and compressibility, the 3D fabric was perforated into a hexagonal honeycomb, high elasticity porous polyurethane foam was used as substrate, and the air layer structure was encapsulated with the packaging film. By changing the hexagonal side length and wall thickness of the honeycomb structure, the integral fabric air layer polyurethane buffer composite was prepared. The properties of the structure were studied, and its compressive capacity under different compressive strains was analyzed. The results show that the mechanical properties of polyurethane foam were improved after adding the integral fabric air layer structure. When the composite HPU‐R1L2 (polyurethane cushioning composites with 1 cm side length and 2 cm wall thickness of hexagonal honeycomb) was compressed to 75%, its compressive capacity was 8.24 times that of PU (Polyurethane foam with 2.5% bentonite). The prepared composite HPU‐R1L1 (Polyurethane cushioning composites with 1 cm side length and 1 cm wall thickness of hexagonal honeycomb) absorbed 96.7% of the energy in the dynamic impact test, indicating that the composite cushioning performance was stronger than that of polyurethane foam. The HPU composites based on the synergistic reinforcement strategy of polyurethane foam and monolithic fabric air‐layer structures are an excellent candidate in the field of commodity packaging and personal protection.

Influences of Halloysite Nanoparticles on the Mechanical Properties of Polyurethane Foam

Influences of Halloysite Nanoparticles on the Mechanical Properties of Polyurethane Foam

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

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

Preparation of polyurethane foam fine polishing wheel for stainless steel surface

AbstractComparing with dry polishing, the wet‐polishing of the stainless steel surface can significantly reduce dust, noise and other pollution, and improve the polished quality. Thus, it is important to develop new polishing tools. In this work, the effects of the foaming agent and diluents on the mechanical properties of the polyurethane foam (PUF) system were investigated, and then the effect of the filler of graphite on the structure and mechanical properties of PUF was studied. Furthermore, the PUF fine polishing wheel with aluminum oxide was prepared. Results show that the bi‐component diluents combined cyclohexane and dimethylformamide significantly affects the porosity and hardness of the PUF matrix. The filler of graphite can decrease the mechanical properties of the polyurethane matrix and increase the porosity of PUF, consequently, improve the self‐sharpening of the PUF polishing wheel. The PUF fine polishing wheel with aluminum oxide shows fine polishing performance.

Investigation of the Polyol Types and Isocyanate Concentrations on the Rheological, Morphological and Mechanical Properties of Polyurethane Foams

This research studies the preparation and characterization of polyurethane foams, which are produced from the reaction of isocyanate Methylene Diphenyl Diisocyante “MDI” and polyol with water being used as a chemical blowing agent. The effect of isocyanate concentration on the cross-linking formation of polyurethane samples and its influence on the final properties of the foams were investigated. Each type of polyols (Local commercial market polyester, Quickmast120 and Quickmast110 polyether) were mixed with the isocyanate at equivalent ratio of (isocyanate: polyol) (0.5:1, 1:1, 2:1 and 3:1) to prepare polyurethane foam using one shot method. Rheological tests were performed for the polyols and isocyanate to find out their effect on the formability processes. The morphology and structure were performed using FTIR and digital microscopy. The tensile strength, compression strength and the hardness were conducted to show the effect of isocyanate concentrations on the mechanical properties of samples. The result display the Quickmast 120 polyol was unsuitable due to the large cells, unstable rheological properties and high hardness, which leads to a loss of flexibility of the polyurethane foams. The ratio of (1:1) (polyol/isocyanate) was the best in terms of the formability of the foam giving the smaller cells size and the best mechanical characteristics as compared to other concentrations of isocyanate.

Experimental Measurements of Mechanical Properties of PUR Foam Used for Testing Medical Devices and Instruments Depending on Temperature, Density and Strain Rate.

Rigid polyurethane (PUR) foam is products used as a biomedical material for medical device testing. Thermal stability is a very important parameter for evaluating the feasibility of use for testing surgical instrument load during drilling. This work aimed to perform experimental measurements to determine the dependence of the mechanical properties of a certified PUR on temperature, strain rate and density. Experimental measurements were realised for three types of the PUR samples with different density 10, 25 and 40 pounds per cubic foot. The samples were characterised in terms of their mechanical properties evaluated from tensile and compression tests at temperatures of 25 °C, 90 °C and 155 °C. Furthermore, the structures of the samples were characterised using optical microscope, their thermal properties were characterised by thermogravimetric analysis, and their density and stiffness with the effect of temperature was monitored. The results show that it is optimal not only for mechanical testing but also for testing surgical instruments that generate heat during machining. On the basis of experimental measurements and evaluations of the obtained values, the tested materials are suitable for mechanical testing of medical devices. At the same time, this material is also suitable for testing surgical instruments that generate heat during machining.

Preparation and characterization of diatomite and hydroxyapatite reinforced porous polyurethane foam biocomposites

Porous three-dimensional (3D) polyurethane-based biocomposites were produced utilizing diatomite and hydroxyapatite as fillers. Diatomite and Hydroxyapatite (HA) were utilized to reinforce the morphological, chemical, mechanical, and thermal properties of polyurethane foam (PUF). Diatomite and Hydroxyapatite were added into polyurethane at variable percentages 0, 1, 2, and 5. The mechanical properties of PUF were analyzed by the compression test. According to the compression test results, the compressive strength of the polyurethane foam is highest in the reinforced foam at 1% by weight hydroxyapatite compared to other reinforced PUFs. Scanning electron microscopy (SEM) images presented structural differences on foam by adding fillers. Functional groups of PUF were defined by Fourier Transform Infrared Spectroscopy (FTIR) and the thermal behavior of PUF was studied with Thermogravimetric Analysis (TGA). The obtained results revealed that PUF/HA biocomposites indicated higher thermal degradation than PUF/Diatomite biocomposites.

Reinforcement Efficiency of Cellulose Microfibers for the Tensile Stiffness and Strength of Rigid Low-Density Polyurethane Foams.

Rigid low-density closed-cell polyurethane (PU) foams are widely used in both thermal insulation and structural applications. The sustainability of PU foam production can be increased by using bio-based components and fillers that ensure both enhanced mechanical properties and higher renewable material content. Such bio-based foams were produced using polyols derived from rapeseed oil and microcrystalline cellulose (MCC) fibers as filler. The effect of MCC fiber loading of up to 10 wt % on the morphology, tensile stiffness, and strength of foams has been evaluated. For estimation of the mechanical reinforcement efficiency of foams, a model allowing for the partial alignment of filler fibers in foam struts was developed and validated against test results. It is shown that although applying MCC fibers leads to modest gains in the mechanical properties of PU foams compared with cellulose nanocrystal reinforcement, it may provide a higher content of renewable material in the foams.

Effect of carbon nanotube doping on the energy dissipation and rate dependent deformation behavior of polyurethane foams

An experimental investigation is performed to characterize the effect of carbon nanotubes on the average mechanical properties of polyurethane foams. Polyurethane foams are doped with as-grown and oxidized carbon nanotubes at varying carbon nanotube concentrations. It is observed that the inclusion of carbon nanotubes up to a threshold concentration decreases the density of freely expanding polyurethane foams. Uniaxial and cyclic compression testing of foam samples is carried out to study their energy dissipation and rate dependent deformation behavior. While energy dissipation is observed to be higher in neat polyurethane foams, carbon nanotube reinforced foams show better recovery when compressed beyond elastic limit due to their stiffer foam cell walls. It is shown that incorporation of oxidized carbon nanotubes should be preferred over as grown carbon nanotubes to improve flexural, thermal and acoustic response of polyurethane foams. Scanning electron microscopy analysis of compressed samples reveals that cell shearing; cell bending and fracture at nodes are the predominant mode of deformation in all foam samples.

Studies on Modelling of Mechanical Properties of Polyester-based Semi-rigid Polyurethane Foams

This paper describes the mechanical behaviour of castor oil based semi rigid polyurethane foams with relative density below 0.05moulded by varying isocyanate index (Isocyanate equivalent/hydroxyl equivalent) from 1:1 to 1:2. Mechanical properties of polyurethane foam mainly compressive strength is measured experimentally and the values were compared using three widely referred theoretical models namely: (i) the Empirical model (ii) Gibson and Ashby approach widely used for foam description and (iii) modified Gent Thomas model. Empirical model suggested that the synthesised polyurethane foam is closed-cell foams, which have cell walls that undergo stretching and struts that undergo bending. Experiment values showed variation from Gibson and Ashby model and Gent Thomas model, since both these models are based on the deformation of a simple cubic or rectangular structure, which is not representative of a real foam structure.

Combined effects of temperature and humidity on the mechanical properties of polyurethane foams

The effects of temperature and environmental moisture on the viscoelastic behavior of polyurethane foams were investigated both theoretically and experimentally. It was shown that the effect of the environmental parameters can be explained in terms of a variation of the free volume of the solid fraction of the foams, thus allowing the use of the superposition principle to predict their influence on the viscoelastic behavior of the materials. Dynamic mechanical analyses were performed to measure the dependence on frequency, temperature, and relative humidity of the complex modulus of two different polyurethane foams, differing in terms of their glass transition temperature. The time-temperature-humidity superposition principle was proved to be applicable for the tested materials. Next, the relaxation spectra and their dependence on the relative humidity were adopted to assess its effects on the large strain behavior of the foams.The effects of temperature and environmental moisture on the viscoelastic behavior of polyurethane foams were investigated both theoretically and experimentally. It was shown that the effect of the environmental parameters can be explained in terms of a variation of the free volume of the solid fraction of the foams, thus allowing the use of the superposition principle to predict their influence on the viscoelastic behavior of the materials. Dynamic mechanical analyses were performed to measure the dependence on frequency, temperature, and relative humidity of the complex modulus of two different polyurethane foams, differing in terms of their glass transition temperature. The time-temperature-humidity superposition principle was proved to be applicable for the tested materials. Next, the relaxation spectra and their dependence on the relative humidity were adopted to assess its effects on the large strain behavior of the foams.

Effect of Cellular Structure on Mechanical Properties of Polyurethane Foam Curing Materials

Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m3.

Fabrication of novel formulations from rigid polyurethane foams and mortar for potential applications in building industry

Rigid polyurethane (PU) foams are widely used in modern life owing to excellent strength and weight carrying capacity. Most of the rigid PU foams in the market are based on polypropylene oxide (PPO) and methylene diphenyl diisocyanate. Amine catalysts, especially tertiary amines, are used to balance both the gelling and gas-foaming reactions, responsible for foam formation. The objective of present work is to prepare rigid PU foams from PPO based polyol and 4,4′- methylene diphenyl diisocyanate (MDI). The morphological and mechanical properties of polyurethane foam using tertiary amine and water blowing agent have been investigated. Moreover, acoustic and thermal insulation of polyurethane foam ordinary Portland cement mortar formulations were also examined. The results indicated that polyurethane ordinary Portland cement mortar formulations have good sound absorption and thermal insulation characteristics compared to blank formulations.