Open-cell Polyurethane Foam Research Articles

Polyurethane foam-cadmium sulfide nanocomposite with open cell structure: Dye removal and antibacterial applications

A new way to synthesize open cell polyurethane foam using cadmium ions has been described. By converting to cadmium sulfide nanoparticles, cadmium ions have been fixed on the open cell polyurethane foam. Open cell polyurethane foam containing CdS nanoparticles (PUF-CdS) was characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The SEM results showed foam containing nanoparticles unlike pure foam (PUF) has an open cell structure. In the following, the applicability of synthesized nanocomposite in wastewater treatment was investigated. The dye removal efficiency of PUF-CdS was investigated with the objective of removing Reactive Orange 122 (RO122) as a model pollutant from aqueous solution. The effects of adsorbent dosage, initial dye concentration and initial pH of solution on RO122 removal were studied. Kinetics and equilibrium isotherms for adsorption of dye on PUF-CdS were analyzed. The maximum adsorption capacity obtained from Langmuir isotherm equation was 22.7 mg g−1. The experimental data were adjusted to the pseudo-second-order kinetic model. The antibacterial activity of PUF-CdS was also investigated against E. coli and S. aureus.

Characterization of organophosphorus flame retardants’ sorption on building materials and consumer products

Better understanding the transport mechanisms of organophosphorus flame-retardants (OPFRs) in the residential environment is important to more accurately estimate their indoor exposure and develop risk management strategies that protect human health. This study describes an improved dual small chamber testing method to characterize the sorption of OPFRs on indoor building materials and consumer products. The OPFRs studied were tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP). The test materials and products used as sinks include concrete, ceiling tile, vinyl flooring, carpet, latex painted gypsum wallboard, open cell polyurethane foam, mattress pad and liner, polyester clothing, cotton clothing, and uniform shirt. During the tests, the amount of OPFRs absorbed by the materials at different exposure times was determined simultaneously. OPFRs air concentrations at the inlet and inside the test chamber were monitored. The data were used to rank the sorption strength of the OPFRs on different materials. In general, building materials exhibited relatively stronger sorption strength than clothing textiles. The material-air partition and material phase diffusion coefficients were estimated by fitting a sink model to the sorption concentration data for twelve materials with three OPFRs. They are in the range of 2.72 × 105 to 3.99 × 108 (dimensionless) for the material-air partition coefficients and 1.13 × 10−14 to 5.83 × 10−9 (m2/h) for the material phase diffusion coefficients.

Green roofs for built environment recovery: technological transitions

In 2012, the Laboratory of Recovery and Maintenance at the University of Naples Federico II starts an applied research with the Institute for Composite and Biomedical Materials – IMCB – National Research Council of Italy – CNR, of Naples. The aim is to explore the potential of a patented hybrid foam, Hypucem, as a green technology for the recovery of flat roofs in reinforced concrete buildings.Two green extensive prototypes are developed and tested to provide an adequate response to the problem of residential buildings. The difference between them is in the mode of greening: sowing before or after the on-site assembly, with overlapping layers of green, in the first case, and their integration into special pockets formed inside the panel, in the second. Laboratory tests verify the germination and growth dynamics for a closed-cell polyurethane-concrete foam and for open-cell polyurethane-soil specimens.Trials are carried out in a residential neighborhood realized after Second World War. During six months, the benefits to buildings' performances, in both solutions, are monitored, highlighting the importance of roofs dimensions and accessibility. With a greater ease of installation and inspection, the open-cell polyurethane foam solution, accommodating transplanted vegetation, results more suitable for a direct involvement of users in ordinary maintenance. This attitude is fundamental in order to prevent any decrease in roofs thermal resistance due to the lowering of the green layers performances.

Carbon nano-ink coated open cell polyurethane foam with micro-architectured multilayer skeleton for damping applications

Carbon nanotube ink coated multilayered polyurethane open cell foams utilize the CNT–CNT interfacial frictional damping mechanism, thus dramatically improving the foam energy dissipation capability by 270%.

Polydopamine-coated open cell polyurethane foams as an inexpensive, flexible yet robust catalyst support: a proof of concept.

Commercially available polyurethane open cell foams are readily coated with mussel-inspired polydopamine. The polydopamine film allows robust immobilisation of TiO2 nanoparticles at the surface of the three-dimensional material. The resulting catalyst is efficient for the photo-degradation of an azo dye, reusable and highly resistant to mechanical stress. A novel type of robust structured catalytic support, easily accessible via an inexpensive and green process, is thus described.

All-polymer Layer by Layer coating as efficient solution to polyurethane foam flame retardancy

This paper deals with the Layer by Layer assembly of an all-polymer chitosan/poly(allylamine diphosphonate) coating characterized by high efficiency in reducing the flammability of open cell polyurethane foams. The Layer by Layer assembly of the two components yields a supralinear growing coating that can be easily deposited on the complex 3D structure of polyurethane foams while preserving the open cell nature of the substrate. 2 bi-layers (BL) are enough to guarantee the deposition of a continuous thin coating capable of preventing the dangerous melt dripping phenomenon during flammability tests. The very same coating can dramatically reduce the heat release rate under a 35kW/m2 heat flux as it can efficiently hinder the foam structural collapsing during combustion. 2 BL coatings achieve a reduction of 48% while 4 BL reaches the maximum reduction of 55%, thus confirming the great efficiency of the coating in reducing the PU flammability at such low deposition steps and coating thicknesses.

Structural and optical properties of cordierite glass-ceramic doped in polyurethane matrix

The cordierite (2Mg.2Al2O3.5SiO2) was synthesized by the Pechini method and added to polyurethane open cell (PUOC) foam in three different percentages. Fourier transform infrared spectroscopy (FTIR) was employed to evaluate the bonding characteristics of PUOC/cordierites. The effect of temperature on the synthesis of cordierite and crystallographic structure of the final product were studied by XRD. By increasing the temperature, the widths of the XRD peaks decreased, approaching the single crystal spectrum. The SEM results show that by increasing of cordierite percentage in PUOC foam, the matrix structure was much damaged. Using Z-scan method, optical nonlinearities of samples were measured by continues wave (CW) laser at the wavelength of 532 nm. The nonlinear refractive (NLR) indices and nonlinear absorption (NLA) coefficients of the synthesized samples are obtained in the order of 10−8 (cm2/W) with negative sign and 10−5 (cm/W), respectively. The origin of optical nonlinearity may be attributed to the presence of strong saturable absorption (SA) effect.

A comparison of sintered materials for the reduction of wind noise in acoustic sensors

Wind noise reduction has been of particular interest in the acoustic sensor arena for many years. Ideally, a desirable noise-mitigating medium is resilient to extreme temperatures and dust, as well as insects/animals. Open cell polyurethane foam is the most widely chosen material for acoustic wind noise reduction. These windscreens tend to provide protection from humidity and moisture, as well as reduction of wind flow noise at the frequencies of interest (500 Hz and below). However, after prolonged use in the environment, degradation of the windscreen and its performance is inevitable. Exposure to high levels of UV rays tends to make the windscreens brittle, while sand and dirt may become lodged in the pores requiring frequent cleaning or replacement, and they can be vulnerable to wildlife. Ideally, one would like to replace the current foam windscreen with a more durable, smaller, lower-profile medium providing similar wind noise rejection to that of foam windscreen. This research will compare the effectiveness of porous metal and plastic windscreens fabricated from sintered material to that of the conventional open cell foam windscreen in reducing wind generated flow noise.

Strong similarities in the creep and damage behaviour of a synthetic bone model compared to human trabecular bone under compressive cyclic loading

Understanding the failure modes which instigate vertebral collapse requires the determination of trabecular bone fatigue properties, since many of these fractures are observed clinically without any preceding overload event. Alternatives to biological bone tissue for in-vitro fatigue studies are available in the form of commercially available open cell polyurethane foams. These test surrogates offer particular advantages compared to biological tissue such as a controllable architecture and greater uniformity. The present study provides a critical evaluation of these models as a surrogate to human trabecular bone tissue for the study of vertebral augmentation treatments such as balloon kyphoplasty. The results of this study show that while statistically significant differences were observed for the damage response of the two materials, both share a similar three phase modulus reduction over their life span with complete failure rapidly ensuing at damage levels above 30%. No significant differences were observed for creep accumulation properties, with greater than 50% of creep strains being accumulated during the first quarter of the life span for both materials. A significant power law relationship was identified between damage accumulation rate and cycles to failure for the synthetic bone model along with comparable microarchitectural features and a hierarchical composite structure consistent with biological bone. These findings illustrate that synthetic bone models offer potential as a surrogate for trabecular bone to an extent that warrants a full validation study to define boundaries of use which compliment traditional tests using biological bone.

Liquid flow in polyurethane foams for filtration applications: a study on their characterization and permeability estimation

Open-cell polyurethane foams have been investigated for various filtration applications to treat industrial byproducts and waste water. Flow-related morphological characterization of three types of polyurethane foams: (1) control, unmodified polyurethane foam, (2) flexible polyurethane foam obtained by chain extension, and (3) rigid polyurethane foam obtained by chain extension, is presented in this study. Analysis of micrographs, using histograms based on pore size, revealed that the pore size varied in the foams based on their composition. The permeability (K) of the foams for liquid flow, measured by a falling-head permeameter was in the range of 0.45 × 10−11–2.62 × 10−11 m2. In comparison to the theoretical permeability models, the experimental values were smaller by two orders of magnitude. The theoretical prediction of the permeability improved after considering effective porosity and replicated the trend seen in the experiments, but the large gap between the prediction and experiments remained. The failure of the theoretical models points to the need for developing more accurate permeability models after including 3-D pore interconnections and swelling of solid matrix.

Auxetic Foams for Sport Safety Applications

Auxetic materials offer potential to be applied to sports safety equipment. This work reports quasi-static and impact testing of auxetic open-cell polyurethane foam - fabricated with a compression and heat treatment process - in comparison to its conventional counterpart. The foam was compressed to 70% of its original dimension along each dimension during the conversion process. Quasi-static compression testing confirmed the converted foam to be auxetic, with a Poisson's ratio of -0.08. Impact testing was performed for energies up to 5.6J with an instrumented drop rig and high-speed video. Peak accelerations were ∼3 times lower for the auxetic foams, because they prevented bottoming. This work has shown further potential for auxetic foam to be applied to sports safety devices. Future work should look to optimise foam selection and the conversion process, while comparing auxetic foam with existing materials and products.

DirectCell technique: A very fast and simple method for characteristic lengths estimation in polyurethane open cell foam

The use of open cell foams with high specific surface area represents an important breakthrough in several industrial applications. The modeling of the three-dimensional structure of the open cell foams and the definition of relevant geometrical characteristic dimensions deserve fundamental investigations for the possible applications in chemical engineering. Based on experimental data given by X-ray tomography or by scanning electron microscopy, we can have a good description of some of the features of the foam (average cell aperture and strut diameter). However, these techniques are complex, burdensome and long. The main goal of this work is to propose a new, simple and fast technique in order to estimate the main characteristic lengths (cell, pore and strut size) of the open cell foams.

Foams as 3D perforated systems: An analysis of their Poisson's ratios under compression

Using experimental data, it is shown that the Poisson's ratios of standard (untreated) open cell polyurethane foam vary when loading in different loading directions, since foam is inherently asymmetric and anisotropic. The loading direction which is in plane orthogonal to the rise direction of the foam constantly exhibited the most negative Poisson's ratio across foam samples of different types, even at moderate compressive strains. It was also shown that although the foam may become auxetic at very high values of compressive strain, it shows an incremental negative Poisson's ratio at moderate compressive strains. The results obtained are discussed in light of the deformation mechanisms, which have been proposed in literature to explain negative Poisson's ratios in foams. The effects of changing loading direction on the mechanical response of the foam are highlighted.An image of the symmetrical face of a foam cube, taken using a confocal microscope at 4× magnification.

A comparison of two total contact cast constructs with variable body mass.

There is a growing body of evidence implicating obesity as having a negative effect on the development and treatment of diabetic foot disease. The aim of this study was to increase the body of knowledge on the effects of obesity on foot function, specifically as it relates to peak plantar pressures in the total contact cast (TCC). Our investigational objectives were to compare the effect of two different TCC designs on mean peak plantar pressures, and to evaluate the efficacy of two TCC constructs with increasing body mass. The primary outcome measure was mean peak plantar pressure in the heel, midfoot, forefoot and first metatarsal as measured with an in-shoe pressure measurement system. The variables were patient weight (from 'normal' body mass index (BMI) to 'overweight', 'obese' and 'morbidly obese') and the TCC construct (with both a standard and alternate cast design). The standard TCC is considered the gold standard for off-loading of the diabetic foot. The alternate TCC was designed to use the essential offloading component of the traditional TCC, namely the total contact leg section, with use of an open cell polyurethane foam to transfer load from the foot to the lower leg, thereby offloading the foot by suspending it within a padded fiberglass walking cast. We did not observe statistically significant differences in mean peak plantar pressures in any plantar foot anatomic area or with any body mass between the two TCC designs. Based on the results, we concluded that the alternate TCC design provides another viable TCC construct option for practitioners working with the neuropathic foot. This investigation also provides specific data on changes that occur in peak plantar pressures with use of the total contact cast and variable BMIs. none.

Modelling open cell-foams based on the Weaire–Phelan unit cell with a minimal surface energy approach

The complex architecture of open cell foams has most often been described by Kelvin cell models. It has been shown that the accuracy to predict the elastic properties of open cell foams increases with an increasing level of detail and resemblance to real foam microstructures. However, the Kelvin cell does not possess pentagonal faces which are the most abundant within real open cell foams. Therefore this study focuses on the use of the Weaire–Phelan unit cell to model the elastic properties of an open cell polyurethane foam. Optical and scanning electron microscopy were used to characterise the architecture of the open cell foam. Surface Evolver software was used to minimize the surface energy and introduce the typical architectural characteristics of the open cell foam to the FE-model. The E-modulus and Poisson coefficient of the Kelvin and Weaire–Phelan cell show a similar behaviour as a function of density. The Weaire–Phelan cell predicts however a higher dependency of the shear modulus on the density. When the influence of the elongation of the cells in the rise direction of the foam and the uncertainty of the solid material properties of the polyurethane is taken into account, a good accuracy of the Kelvin cell and Weaire–Phelan structure based FE-models versus experimental compression tests is found.

Polymer foam-reinforced hydrogels inspired by plant body frameworks as high-performance soft matter

Plant bodies consist of many cells. Each cell contains a cell wall and a cell membrane, which are involved in maintaining the turgor pressure to bear the weight of the plant body. Inspired by this framework, we prepared a gel material enclosed in many compartments. According to this concept, hydrogels reinforced by polymer foam were fabricated using a simple method, and their mechanical properties were investigated. A piece of polymer foam was immersed in an aqueous solution of a water-soluble monomer in the presence of an initiator and a crosslinker. We used sodium acrylate as a monomer, N,N′-methylenebisacrylamide as a crosslinker, 2,2′-azobis(2-methylpropionamidine) dihydrochloride as an initiator and polyurethane foam as a reinforcing material. After gelation, the mechanical properties of the composite gel were analyzed by compression testing. The compression strength of the composite gel was ∼2 MPa, which was much higher than that of the poly(sodium acrylate) (PSA) hydrogel alone. The compression modulus was also considerably higher than for each constituent material alone (both hydrogel and foam). When melamine foam was used in place of polyurethane foam, the mechanical properties of the composite gel significantly deteriorated. We tried to prepare a gel material enclosed in many compartments, inspired by plant body framework. According to this concept, hydrogels reinforced by polymer foam were fabricated, and their mechanical properties were investigated. We prepared sodium acrylate hydrogels reinforced by open-cell polyurethane foams. After the gelation, the mechanical properties were assayed by the compression test. The compression strength of the composite gel was ∼2 MPa, which was much higher than that of poly(sodium acrylate) hydrogel alone; and the compression modulus was also considerably higher than that of each constituent material alone.

Compressive Response of Polyurethane Open-Cell Foam with Electrodeposited Copper Coatings

Mechanical response of polyurethane open-cell foam with electrodeposited copper coatings under compressive loads is investigated via experimental characterization. Commercially available open-cell polyurethane foam specimens are copper deposited using electroless and electro-deposition techniques. Thickness and composition of the coating are controlled by varying the deposition time to 30, 60 and 90 minutes. Micrographs of the coated foam structure show that the coating thickness is higher at the outer surface, and the averaged thickness linearly depends on the deposition time. The coated foam exhibits a stiffer compressive response than that of the uncoated one. When unloaded, the copper coating layers fracture at the center of foams ligaments, and fall off from the foam structure.

The production and characterization of topologically and mechanically gradient open-cell thermoplastic foams

The development of longitudinally and radially gradient open-cell polyurethane foams is reported. Local and global mechanical properties and pore structure have been characterized using video extensometry with x−y strain-mapping capability, and x-ray microtomography (CT) and scanning electron microscopy (SEM), respectively. The local axial Poisson’s ratio varies in a smoothly continuous manner along the length of the longitudinally gradient foam from large negative (auxetic), through zero, to positive (conventional) values. The production of radially gradient foams having a coaxial core–sheath structure is reported for the first time. Two radially gradient foams have been produced, each displaying similar global negative axial Poisson’s ratio responses but with markedly different local axial Poisson’s ratio and local axial Young’s modulus behaviours. One of the radially gradient foams displays a positive Poisson’s ratio core and an auxetic sheath resulting from conventional and higher density re-entrant open-cell pore structures, respectively.

Investigation of AC8A Scrap-Recycled Aluminum Foams

Open-cell Al foam has outstanding properties which are suitable for functional applications. However, a major drawback for widespread employment of Al foam is its high relative cost which can be several times higher than conventional metals. To reduce the cost, a recycled material waste is constructively used instead of expensive base metal. The present study aims to fabricate economical open-cell Al foams using AC8A alloy scrap from lathe machines. The Al foams were fabricated through pressure infiltration casting process at which the cellular pattern was made from commercial reticulated open-cell polyurethane foams with the pore size of 12 ppi. The compressive strength and microhardness of scrap-recycled Al foams are higher than those of pure Al foam. The increase in foam mechanical properties resulted from the change in foam microstructure as the formation of Si hard phase in Al matrix. The strength and microhardness of the foams increase with increasing scrap contents.

The use of negative pressure wound therapy in veterinary wound care

Negative pressure wound therapy (NPWT) or vacuum-assisted closure (VAC) of wounds is a treatment modality that consists of applying sub-atmospheric, or negative, pressure to a wound resulting in wound protection, drainage and accelerated wound healing. NPWT systems are constructed by the use of commercial or improvised systems; the wound is packed with open cell polyurethane foam or gauze, covered with adhesive drape and connected with tubing to an adjustable suction device. Recently, more portable, single-use systems have been developed, that make them more versatile for use, particularly in veterinary patients.