Papers by Keyword: Polyurethane Foam

Abstract: The paper proposes an approach to studying the influence of changes in the mechanical characteristics of the material under the influence of plastic deformations in foam materials on changes in their mechanical behaviour. The research was conducted for the case of unsteady multi-cycle loading, which caused plastic deformations, but did not cause material failure. The modelling was carried out in a general unsteady formulation within the framework of Cosserat elasticity, which made it possible to take into account the influence of the heterogeneity of the structure of materials. The proposed methodology is based on the combined use of the method of integral transformations and the indirect boundary element approach. To solve the unsteady problem within the framework of couple elasticity, the time integral and discrete Fourier transform were used in the paper. The assessment of the change in the mechanical, physical and microstructural characteristics of foams under the action of loads causing plastic deformations was carried out on the basis of experimental studies of a series of polyurethane foam samples. Using experimental data based on developed analytical-numerical method [4], the change in the distribution of normalized radial stresses in the internal layers of foam media was investigated, taking into account changes in mechanical, physical, and microstructural characteristics. The use of the approach proposed in the paper makes it possible to assess the change in the residual resource of bodies made of foam materials in the case of short-term loads that cause plastic deformations of the medium.

Abstract: One of the critical components in the rehabilitation of lower limb amputees is the prosthetic foot. The solid ankle cushion heel (SACH) foot is commonly prescribed to patients due to its ability to reduce impact loading at heel strike, as well as its durability and cost-effectiveness. This research focuses on developing a composite SACH foot using two different polymers. The keel was constructed from Nylon fiber, while the shell, designed to resemble an amputee's foot, was made from Polyurethane (PU) foam. The keel functions as a surrogate for the amputee's bone and is therefore specifically designed and embedded within the shell. The developed SACH foot underwent static testing according to the ISO 10328:2016 standard at various angles. Additionally, it was modeled and analyzed using the finite element method (FEM). Material tests were conducted on both the keel and shell to establish their material models for FEM. The finite element analysis (FEA) demonstrated an average error of less than 15.22%. Moreover, the FEA provided insights into the deformation and stress experienced by both the keel and the shell. This detailed investigation into the structural behavior of both SACH components offers valuable guidance for the future design and development of composite SACH feet.

Abstract: The paper examines the influence of loading modes on polyurethane foam elements on the change in mechanical properties of the material under load, resulting in plastic deformation of the material. Studies were carried out on polyurethane foam samples with different ratios of polyol and isocyanate in the foam-forming mixture. From the materials obtained, groups of samples were formed for which a comparison was made of their mechanical behaviour when compressed under the action of a load that causes plastic deformation of the material. To evaluate the change in characteristics, multiple cyclic loading was carried out in the zone of plastic deformation and the change in Young's modulus under the action of such loading was studied.

Abstract: This study explores the effect of varying epoxidized palm oil (EPO) content on the mechanical properties and pressure distribution of polyurethane (PU) foam. Polyurethane foams were synthesized with EPO concentrations of 25%, 50%, and 75%, and their morphologies, densities, hardness, compressive strength, and pressure distribution capabilities were analyzed. The results showed that increasing EPO content significantly affects the foam's cell structure, leading to variations in density and mechanical properties. PU foam with 50% EPO exhibited a more open-cell structure, resulting in lower density and hardness but compromised compressive strength. Conversely, foam with 75% EPO content demonstrated improved pressure distribution despite increased density and nonuniform cell sizes. These findings highlight the potential of using palm oil-based polyols to develop sustainable PU foams, balancing flexibility and mechanical strength for applications in cushioning and pressure relief materials. The study underscores the importance of optimizing EPO content to achieve desirable foam properties for specific applications.

Abstract: This study explores the impact of epoxidized palm oil (EPO) content and surfactant type on the mechanical properties of polyurethane foams. The resilience, hardness, and compressive strength of the foams were systematically analyzed at different NCO/OH molar ratios. The findings revealed that increasing EPO content generally decreased both hardness and resilience values, indicating enhanced viscoelastic properties due to the plasticizing effect of EPO's hydrocarbon chains. However, specific surfactants significantly influenced these mechanical properties. Concentrol STB PU-2254 and Tegostab® B82001 VE surfactants enhanced compressive strength by promoting a compact cellular structure with smaller, more numerous cells, effectively distributing loads and counteracting the softening effect of high EPO content. Conversely, the use of Tegostab® B8462 resulted in reduced hardness due to increased porosity from larger cell formation. At an NCO/OH ratio of 1.0, higher pMDI content improved compressive strength by increasing hard segment formation. These results underscore the importance of surfactant selection and NCO/OH ratio optimization in tailoring the mechanical properties of polyurethane foams, offering valuable insights for their application-specific design and optimization.

Abstract: Cellulose is a fascinating biopolymer and sustainable raw material. Cellulose particles with at least one dimension in the nanoscale are referred to as nanocellulose. Kenaf fiber is a natural fiber used in this study because it has high mechanical properties and strong interface adhesion with polymers so it provides superior properties to other natural fibers. Polyurethane (PU) foam is widely used as a core layer in sandwich composite construction to produce a lightweight material. This study presents a synthesis of cellulose nano-fibrils (CNF) extracted from East Java, Indonesia based kenaf fibers, an analysis of the effect of adding CNF as a filler and a reinforcement in PU foam composites, and a formulation of PU-CNF foam composite that provided the best mechanical properties as strong and lightweight materials in structural applications. The CNF extraction from kenaf fiber started by fiber pre-treatment including alkalization and bleaching, then mechanical treatment with an Ultra Fine Grinder to produce CNF suspension. The weight variations of CNF in PU foam were 0, 3, 5, 7, and 10 wt%. PU-CNF composite fabrication using the in-situ polymerization method. CNF characterization included TEM, XRD, and FT-IR. TEM results on CNF show that the CNF diameter is in the range of 40-70 nm. The functional group from the FT-IR results showed that the pre-treatment process on kenaf fiber was successful in reducing the lignin and hemicellulose content. XRD results showed that the CNF crystallinity was 75.22%. The PU-CNF foam composite characterization included a compressive test, 3-point bending test, and SEM. The PU foam composite with 3 wt% CNF reinforcement is the best composite which has the optimum value from the results of the compression test and the 3-point bending test. The compressive strength value increased by 20.01%, from 236.997 kPa to 284.434 kPa, the compressive modulus value increased by 29.21% from 5.67 MPa to 7.32 MPa, and the 3-point bending strength value increased 28.29% from 572.24 to 734.15 kPa. All the results expected to support that CNF was a potential reinforcement material with a high surface area for a wide variety of applications.

Abstract: The utilization of vegetable oil in producing bio-based polyol, as an alternative replacement to petroleum-based polyol in making polyurethane (PU) foam has gained a lot of interest due to its finite supply and low production cost. In this study, bio-based polyol using coconut oil as raw material produced PU foam as thermal insulation material. The vegetable oil-based polyol was prepared using a two-step method, while PU foams were prepared by the free-rise method. In order to enhance the thermal properties of the produce PU foams, phase change material (PCM) was added to the PU foam formulation. FTIR spectra result showed peaks at 2920 cm^-1 and 2850^-1, which signifies the CH2 asymmetric stretching, indicating that n-octadecane was successfully incorporated into PU foams. Moreover, heat flow meter (HFM) and thermo-gravimetric analysis (TGA) show PU foam with 1% n-octadecane shows better thermal properties than other produced PU foams. Furthermore, the universal testing machine (UTM) result shows an enhancement in the mechanical properties of the produced PU foam. These results demonstrate that the addition of n-octadecane to the PU foam formulation improved the mechanical properties of PU foams while enhancing their thermal properties.

Abstract: The paper shows the applicability of expandable graphite METOPAC EG 350-50 (80) in a rigid PU foam system as a substance that reduces the flammability (flame retardant) and improves the usability. The studies of the physical mechanical and thermal properties of PU foam with a higher graphite content revealed a higher normal sound absorption coefficient; insignificant influence on the thermal conductivity; a higher decomposition onset temperature; more difficult ignition. PU foam sample with a ratio of 15 graphite weight fractions to 100 polyol weight fractions has the highest physical mechanical and thermal properties, and, as compared to the starting PU foam, it features an increase in normal sound absorption coefficient by an average of 3 times; a decrease in the thermal conductivity by 8 %; an increase in the decomposition onset temperature by 6.7 °С. Therefore, the modification of PU foam with expandable graphite makes it possible not only to develop hardly combustible polyurethanes but also to improve its physical mechanical and thermal properties.

Abstract: In this paper, the selected properties of lightweight composites based on the different kinds of binder and recycled waste plastics aggregate were studied. Plastic waste e.g. foamed polystyrene, polypropylene, polyurethane foam or ethyl vinyl acetate (EVA) as an aggregate in these composites was used. Cement CEM II B/S 32.5 R and an organic-based adhesive with the business name Conipur 360 were used as a binder. The cement composites consisted of constant water to cement ratio 0.50 and dose of cement 175 kg/m³. Mixtures of adhesive composites were prepared with constant dose of adhesive 100 kg/m³. The kind of recycled waste aggregate was only changed. The physical properties, such as bulk density, compressive strength and thermo-technical properties were verified. The application of organic-based adhesive resulted in a significant decreasing values of the bulk density (100 kg/m³ - 230 kg/m³) and the thermal conductivity coefficient (0.0511 W/m.K - 0.0686 W/m.K) of lightweight composites. The negative impact of this type of binder resulted to a decreasing value of the compressive strength (0.15 MPa - 0.32 MPa). Use of cement binder caused to an increasing of bulk density (290 kg/m³ - 375 kg/m³) and worsening of the thermal conductivity coefficient of these composites (0.0660 W/m.K - 0.0799 W/m.K). The compressive strength values of cement composites ranged from 0.24 MPa to 0.50 MPa.

Abstract: Polyurethane (PU) foam were produced from polyol (PolyGreen R3110) and 4,4- diphenylmethane diisocyanate (Maskiminate 80) with distilled water as a blowing agent. Natural fibers have received more attention from researchers due to their ability to increase the properties of the polymer composites. In this work, PU/Henna foam composites were prepared by used Henna fibers at different loading of 5, 10, 15 and 20 wt. %. The effect of different Henna loading on PU foam were investigated by density, compression test, morphology and water absorption. Core density of PU/Henna foam composites increased with addition Henna compared to control PU and showed highest core density of 85.10 kgm^-3. Compressive strength decreased to 0.53 MPa after Henna addition at 5 % PU/Henna foam composites. Henna addition to 20 % PU/Henna foam composites were reduced the compressive strength to 0.97 MPa due to stiffness effect of Henna that contributed to embrittlement of the cell wall. The distorted cell wall and less uniform of cell structure were proved by SEM due to Henna addition as compared to control PU. Water absorption percentage of PU/Henna foam composites were increased with Henna addition as compared to control PU. It is because hydrophilic properties of Henna tendency to absorb moisture.