High-density Polyurethane Research Articles

Comparison of Biowaste Fillers Extracted from Fish Scales and Collagen on the Mechanical Properties of High-Density Polyurethane Foams

The utilization of biowaste fillers in the development of high-density polyurethane (PU) foams has gained significant attention due to environmental and economic benefits. This study investigates the mechanical properties of PU foams reinforced with biowaste fillers extracted from fish scales (FS) and fish scale-derived collagen (FSC). The fish scales and collagen were characterized for their composition and integrated into PU foams at various loadings. Mechanical properties such as tensile strength, hardness, and density were evaluated. ANOVA was used to analyze the mean values. Bonferroni tests were used to identify differences between the filler materials (α = 0.05). The tensile strength increases with an increase in filler content for both FS (59.48 Kpa) and FSC (65.43 Kpa). No differences were observed between FS and FSC in tensile strength. Significant differences were observed between the FS and FSC in both hardness and density (p < 0.001). The results demonstrated that both fillers enhanced the mechanical properties of PU foams, with collagen-reinforced foams showing superior performance. This suggests that collagen and fish scales can be effective biowaste fillers for developing environmentally friendly PU foams with enhanced mechanical properties.

Effect of size and loading of waste single-used plastic (SUP) aggregates on a bio-based high density polyurethane composite

Abstract The utilization of waste single-use plastic (SUP) as fillers by containment in a polyurethane matrix was investigated as an alternative solution to the detrimental disposal of these waste materials. High-density bio-based rigid polyurethane composites were prepared by adding polyol, isocyanate, and additives, along with densified SUP, which served as aggregate fillers to enhance the bulk density and flexural strength of rigid polyurethane while increasing the thermal conductivity. The aggregated SUPs were prepared using agglomeration-densification machine and exhibited size variations of 12.44 mm (A), 14.12 mm (B), and 15.56 mm (C). The resulting aggregates were added to the rigid polyurethane matrix at varied loadings of 40%, 50%, and 60% v/v. The green composites were cured in heated hydraulic press at constant temperature and pressure. Based on the obtained results, it was found that the formulation with a SUP size of C and a loading of 60% produced the composite of highest bulk density due to relatively high density of agglomerated SUP as the size enlarges. Additionally, the SUP size of A and a loading of 50% (50A) exhibited the highest flexural strength value. This behaviour was attributed to the increased filler-matrix interfacial area achieved with the smallest size aggregates. However, a further increase in aggregate loading resulted in a decrease in this property as common attribute for composite materials. On the other hand, it was revealed that increasing the loading of SUP aggregates provided a lesser insulating effect due to the increase in thermal conductivity resulting from the presence of filled pores within the polyurethane foam. The findings of this study contributed to understanding the effects of aggregate size and loading on the mechanical and thermal properties of the composite material, providing valuable insights for the development of energy-efficient and environmentally-friendly polyurethane structures.

Is Acoustic modal analysis a reliable substitution for Osstell® device in dental implant stability assessment? An experimental and finite element analysis study.

Different methods have been proposed to investigate the fixation stability of dental implants, each of which has its limitations. Among these methods, resonance frequency analysis (RFA) has been widely utilized to measure dental implant stability. This study aimed to assess dental implants with two non-destructive RFA and acoustic modal analysis (AMA) validated with a finite element simulation of the fundamental natural frequency (NF) of the bone analog-implant structure. A total number of 18 implants were inserted into two Polyurethane (PU) bone blocks with different densities (0.16 g/cc and 0.32 g/cc). AMA was used to measure NF; First, the sound originating from the axial tapping of the implant was recorded with a simple microphone. Secondly, a fast Fourier transformation algorithm was conducted to determine the NF of the implant-bone analog structure. In parallel, the ISQ (Implant Stability Quotient) value was measured using the Osstell® device. Finally, using finite element analysis (FEA), the implant-bone analog structure was modeled for validation. Doubling the bone analog density resulted in an average increase of 82% and 47% in the NF and ISQ using AMA and Osstell®, respectively (P-value<0.05). Furthermore, a strong linear relationship (R2= 0.93) was observed between the measured NF and ISQ values in the linear regression analysis. The NF of the dental implant predicted by FEA was overestimated by about 15.2% and 15.0% than those in the low- and high-density PUs, respectively. Moreover, the FEA predicted an increase of 83% in NF by increasing the bone analog density from 0.16 to 0.32 g/cc. Having required the minimum process combined with easily available equipment makes it an ideal method for fixation strength studies. The good correspondence between the ISQ values and NFs, in addition to the good accuracy and reliability of the later method, confirms its application for fixation stability assessment.

Mechanical performance of 3D woven glass fiber I-beam composites with in-situ polyurethane foaming

3D weaving of I-beam structures can potentially create delamination- and joint-free structures, expanding their use in engineering applications compared to metal or traditional laminated composite beams. In addition, polymeric foams can be utilized to fill the vacancies between the web and the flanges of I beams, improving the mechanical characteristics and the structural integrity with little to no weight penalty. Moreover, interposing an adhesive layer between the I beam and the foam structure can result in a more effective bonding which intensifies the structure's robustness. In this study, high-performance I-beam composites were produced by combining polymeric foams with 3D woven glass fiber composites. Low- and high-density polyurethane foams were successfully inserted between the web and the flanges of 3D woven glass fiber composites manufactured by the vacuum infusion process using the free-rise foaming method. Samples with adhesive films were also produced to assess and compare their effectiveness with the composites made solely of polyurethane foam and I beam. The increases in energy absorption capacity and compressive and flexural properties were analyzed under compressive and flexural (three-point bending) loading. The obtained results indicate that structural integrity under bending can be substantially improved with the in-situ foaming supported by adhesive layers.

Lipase-catalyzed glycerolysis of technical lignin towards high-density polyurethane foams

The lignin can be applied in the synthesis of several products, including polymers. Nevertheless, its direct application can affect negatively the mechanical properties of the material, since it presents a highly cross-linked and complex structure. In this scenario, some chemical methods have been explored to increase the reactivity of lignin to produce of polyurethane. Although the literature reports methods intended the modification and incorporation of the lignin in the monomers production, to the best of our knowledge, there are no reports on the use of lipases in transesterification using this biomass. Thus, in this study, biopolyols were synthetized by enzyme-catalyzed transesterification using an ester (castor oil) and an alcohol (glycerol) in the presence of low-sulfur alkaline lignin as substrates, to produces a monomer. Then, high-density rigid foams were obtained via bulk polymerization. An increase in the apparent density and mechanical strength was observed with increasing lignin content. By Scanning Electron Microscopy (SEM) it was possible to observe more elongated and denser mixed cells, associated with the incorporation of lignin. Moreover, the compressive strength reached values of 0.14–0.52 MPa and polymer insoluble fraction were higher than 80 % for all the foams. Then, through this study, it was possible to obtain rigid and high density lignopolyurethane for industrial applications derived from enzymatic glycerolysis and renewable resources.

Crashworthiness analysis and design of a sandwich composite electric bus structure under full frontal impact

The transition toward sustainable transportation includes adopting ecofriendly electric vehicles in public transport, which reduces greenhouse gas emissions and increases energy efficiency. One of the critical features in fuel economy improvement of electric vehicles lies in lightweight structural design. Nevertheless, the crashworthiness of the structures of the vehicles and the safety of passengers must be guaranteed in the attempt of mass reduction because the crash of large vehicles such as buses usually costs many lives. This paper, therefore, aims to present an in-depth analysis of the impact behavior of a lightweight monocoque sandwich composite microbus body under full-frontal crash conditions. The bus structure, made of a high-density polyurethane foam core and woven glass fabric-epoxy face sheets, was modeled and simulated via LS-DYNA dynamic analysis using strength-based Chang-Chang criteria to characterize the failure mechanism of the structure and investigate intrusion into the passenger survival space. Under front collision, the front panel, A-pillars, and front sidewalls of the original bus were found to be extensively damaged in the compressive fiber mode. Based on the 50th percentile male dummy anthropometric parameters, injury indices of 0-5 intervals were proposed to evaluate occupant injury risks. The maximum front and side intrusion into the specified safety space under a maximum impact speed of 50 km/h is 208 mm at the front panel and 221 mm at the sidewall, indicating high injury indices of 3.59 and 4.81, respectively. The effects of stiffeners reinforced in the front panel and foam core thicknesses in the sidewalls, floor, and bottom parts on crashworthiness improvement were thoroughly discussed. The improved bus design can significantly enhance the safety of the occupants with a minimal increase in structural weight of merely 35.6 kg. An effective vehicle safety design under full frontal collision is presented.

The Influence of Density on the Mechanical Response of Reinforced High-Density Polyurethane Foams: A Statistical Approach

In this work, rigid polyurethane foams (RPUF) reinforced by micro fibrillated cellulose (MFC) were manufactured using the free rising method and also under confinement inside a closed mould, aiming to increase apparent density and improve mechanical response. Neat RPUF were also manufactured for comparison. The mechanical response, evaluated by compression (following ASTM D1621 standard) tests were correlated with the final composite apparent density (evaluated following ASTM D1622 standard). Simple linear regression statistical models, based on F-test, were developed using stat graphics software, aiming to understand and correlate the increment in density and its influence on the improvement in mechanical response. Different models were developed to describe the foam behavior. The main results show a more significant influence of the density on strength than stiffness for the neat RPUF, unlike the MFC-reinforced RPUF, which presented an opposite response. These effects could be caused by the lower content of voids when the foams were produced under confinement, and by the greater crosslink density, when MFC was added.

Virtual Studies on the Behavior of Polyurethane on Mechanical Stresses

Abstract In this part of the paper, we will study the behavior of PUR polyurethane at different mechanical and thermal stresses, stresses for which this material behaves very well. It is known that this material behaves well as a protective material against shocks, so it is used as protection against mechanical elements. PUR behaves excellently at uneven static stresses and dynamic stresses. That is why it is used in the construction of the rollers of medium weight mobile devices or rollers that have cam functionality, strongly required for static and dynamic contact. PUR has very good thermal properties, it is used as a thermal insulator when it is in the form of high-density polyurethane foam (PUR / PIR).

Temporary obturator using high-density polyurethane foam following maxillectomy during the coronavirus disease 2019 pandemic.

Rhino-orbital mucormycosis was seen in epidemic proportions during the second wave of the coronavirus disease 2019 pandemic. Many of these post-coronavirus rhino-orbital mucormycosis patients underwent maxillectomy for disease clearance. Rehabilitating such a large number of patients with surgical obturators as an emergency in a low-income setting was challenging. High-density polyurethane foam was used to make a temporary obturator for patients who underwent maxillectomy. These obturators helped alleviate functional problems like dysphagia and nasal regurgitation, improving nutritional outcomes and shortening the hospital stay. The coronavirus disease 2019 pandemic gave physicians time-sensitive challenges, for which immediate alternatives to established care were required. A maxillary obturator made of high-density polyurethane foam is an innovative solution to rehabilitate maxillectomy patients in the immediate post-operative period.

Flexural strength of composite high-density polyurethane foam filled light gauge square steel tubes

The improved flexural strength of composite high-density Polyurethane (PU) foam (Density 150 kg/m3) filled Light Gauge Square Steel (LGSS) tubes is presented in this paper. 4Point bending tests are conducted on Empty and PU Foam filled LGSS Tubes having b/t ratios of 125,100 and 83.33. Numerical study carried out using ABAQUS software to validate experimental results. Using past theoretical models, moment-rotation graphs are prepared for empty and PUFF tubes. The results define the triaxial crushing strength of PU foam in pure bending zone due to confinement by the steel envelope in pre and post buckling regimes and its influence on the composite bending strength (combined flexure and shear). Various types of composite filled tube beams are selected and ratios of their flexural strengths to their own weights are calculated and compared. Observed highest Strength-to-weight ratio for current research composite filled tubes.

Revamping the vehicle protection system using next-generation car bumper to mitigate pedestrian fatality

The increased emphasis on vehicle and occupant safety in automotive accidents has necessitated research on vehicle crashworthiness during the design phase. The design of the bumper plays a significant role in mitigating pedestrian injuries and the risk of life during accidents. The present study is focused on the design and development of an economical external multilayered bumper that can be retrofitted to any car’s existing bumper fascia while improving the safety of pedestrians without compromising the safety of engine components. The proposed multilayered bumper consists of spring and damper assembly along with a layer of high-density polyurethane foam. Finite element analysis has been performed to compute the total deformation, equivalent Von-Misses stress, spring–damping coefficients, and energy absorption using the proposed bumper. An empirical relation amongst considered design parameters is formulated, which can be used to further develop the proposed modified bumper in any feasible ways. A comparative study has also been carried out between the crashworthiness of the conventional bumper and the developed bumper at various speeds. It is observed that a significant reduction of approximately 40% in the impact is observed with the proposed bumper compared to the conventional bumper.

Enhancement of buckling response of stainless steel-based 3D-fiber metal laminates reinforced with graphene nanoplatelets: Experimental and numerical assessments

This research investigates the effects of the inclusion of graphene nanoplatelets (GNPs) on the buckling response of a set of novel three-dimensional fiber metal laminates (3D-FMLs) under a uniaxial compressive load. This special 3D-FML consists of a 3D fiberglass fabric (3DFGF)-epoxy composite hybridized with basalt-epoxy laminate with their resin containing different concentrations of GNPs (0.25, 0.5, and 1.0 wt%), sandwiched between stainless steel (SS) face-sheet with different thicknesses (0.3 mm and 0.48 mm). To further enhance the response of the 3D-FMLs, the cavities of their 3D fabric are filled with two-part low- and high-density liquid polyurethane foam. The main objective is to develop a lightweight and resilient hybrid material system with a competitive cost. In addition, the response of the 3D-FMLs is simulated numerically using LS-DYNA, a commercially available finite element (FE) software. The results produced by the FE models are in good agreement with those obtained experimentally. Moreover, a parametric numerical study is carried out to assess the influence of SS thicknesses and specimen gauge lengths on the buckling response of this hybrid system. The results indicate that a combination of high-density polyurethane foam with 0.25 wt% of GNP content produces the highest buckling capacity, cost-effectively. The microstructural analysis using the field emission scanning electron microscopy (FESEM) technique would also exhibit the distribution and agglomeration of GNPs within the core of 3D-FMLs.

The Effect of Threads Geometry on Insertion Torque (IT) and Periotest Implant Primary Stability: A High-Density Polyurethane Simulation for the Anterior Mandible

The implant geometry provides a key role in the osseointegration process and is able to improve the mechanical interaction and primary stability into the bone tissue. The aim of the present investigation was to compare different implant profiles to evaluate their influence on the primary stability on high-density polyurethane block. Methods: A total of 100 implants were used on 20 pcf polyurethane density in the present investigation, i.e., 20 implants for each of 5 groups (A, B, C, D, and E), characterized by different thread pitch and geometry. The insertion torque (IT), and Periotest mean values were recorded during the implant positioning. Results: Mean values for insertion torque values were higher for the group C and group E implant profiles when compared to all other groups (p &lt; 0.01). No significant differences were detected between these two groups (p &lt; 0.05). Lower IT (&lt;20 Ncm2) were presented by groups A, B, and D (p &lt; 0.05). All groups showed negative Periotest values. Group C implants showed the lowest level of Periotest values (p &lt; 0.05). No significant Periotest differences were found between group B and group D and between group A and group E (p &gt; 0.05). Conclusions: Implants with a wider and V-thread profile and a round apex showed a higher stability in a standardized polyurethane foam. Their use could be suggested in high-density bone in clinical practice.

Micro fibrillated cellulose reinforced bio-based rigid high-density polyurethane foams

Rigid polyurethane foams (RPUF) are the most consumed cellular polymer in the world. Bio-based polyols are sometimes used as raw material for RPUF but with a detrimental effect on mechanical properties. In this paper, micro fibrillated cellulose (MFC) was used as a reinforcement to enhance the mechanical, thermal and dynamic mechanical properties of bio-based RPUF. A bleached Eucalyptus sp. pulp was dispersed in glycerine and then subjected to mechanical defibrillation to extract the MFC, a route that does not require dispersants or drying, which is advantageous for the MCF incorporation. The RPUF were manufactured in a closed mould in a way to obtain overpacking. The higher the overpacking degree, the higher the apparent density and stiffness of the RPUF. Also, expansion under confinement yielded more rounded polymer cells with decreased anisotropy. The MFC and overpacking acted synergistically, improving strength, stiffness, thermal stability and dynamic mechanical properties of the RPUF. Thermal conductivity of the RPUF, on the other hand, was unaffected by those factors.

The Effect of Temperature on Catalytic Pyrolysis of HDPE Over Ni/Ce/Al2O3

The main objective of the current work is to investigate the influence of reaction temperature on catalytic pyrolysis of High-Density Polyurethane (HDPE) over Ni/Ce/Al2O3 into enriched hydrocarbons of pyrolytic oil and gas The experiments were performed at four different pyrolysis reaction temperatures (500, 600, 700, and 800 °C) via in-situ fixed bed reactor. The Al2O3 (75 wt.%) was used as a support, while nickel (20 wt.%) and cerium (5 wt.%) were impregnated as promoters via incipient wetness impregnation method. The catalyst to plastic mass ratio was kept constant at 1:1 for all investigated samples. The results revealed that the Ni/Ce/Al2O3 catalyst has synergistic effects on the catalytic pyrolysis of HDPE into a high yield of hydrocarbon compounds (C5 – C20) in pyrolytic oil and hydrogen gas composition in pyrolytic gas. The highest yield of pyrolytic oil was achieved at 700 °C (53.23 %), while the highest yield of pyrolytic gas was achieved at 800 °C (67.85 %). The small molecular hydrocarbons in pyrolytic oil (C5 - C9) decreases with increasing temperature from 500 to 800 °C. The highest hydrogen gas yield of 77.59 %. was achieved at 700 °C. Thus, this research has economic feasibility in producing alternative valuable energy from the plastic waste stream.

The Thickness of the Medial Wall of the Acetabulum Prevents Acetabular Fracture during the Insertion of a Cementless Cup in Total Hip Arthroplasty: A Biomechanical Study.

Intra-operative acetabular fracture is a total hip arthroplasty complication that can occur during cementless cup insertion, especially in osteoporotic patients. We conducted this biomechanical study to investigate the impact resistance of the acetabulum with simulated bones of different density by drop-weight impact testing. Low- and high-density polyurethane foam blocks were used as osteoporotic and healthy bone models, respectively. Polyurethane blocks were used as the acetabular cancellous bone. Composite sheets were used as the acetabu-lum's medial cortex. The testing revealed that the osteoporotic bone model's impact resistance was significantly lower than that the healthy bone model'. In the healthy bone model, even thin acetabular cancellous bone with ≥ 1 mm acetabulum medial cortex was less likely to fracture. In the osteoporotic bone model, fracture was pos-sible without ≥ 1 mm medial cortex of the acetabulum and thick acetabular cancellous bone. Although impac-tion resistance differs due to bone quality, the impaction resistance in this osteoporotic bone model was equiv-alent to that healthy bone model's when a thick medial wall was present. To avoid intra-operative acetabulum fracture, surgeons should consider both the bone quality and the thicknesses of the medial cortex and acetabu-lar cancellous bone.

Compression characteristics, energy absorption, and feasibility evaluation of egg-box panels made of long fibre prepreg sheets

In this study, the feasibility of using long-fibre-reinforced composites for preparing energy-absorbing structures with a complex geometry was verified by comparing the mechanical performance of two types of egg-box panels, fabricated using plain weave fabric composites (WSN3k, SK Chemical, Korea) and a long-fibre prepreg sheet (LFPS, SK Chemical, Korea). Two types of egg-box panels (large and small models) with different dimensions were prepared to determine the influence of the panel size on the collapsing behaviour and energy absorption rate of the panels. The failure modes at each deformation stage were identified through a multiply interrupted compression test. Furthermore, a high-density polyurethane foam was filled in the cavity of the egg-box panels to suppress premature buckling during crushing. The nominal stress–strain relationships of both types of egg-box panels were obtained through a compression test. Thus, the maximum compressive strength, plateau stress, and energy absorption rate of both types of egg-box panels were experimentally determined and compared. Accordingly, a method to apply LFPS in the fabrication of energy-absorbing structures with a complex geometry was suggested.

Effect of Shod Walking on Plantar Pressure with Varying Insole

Walking and running are very critical factors in human being’s everyday life. A human being takes more than 2,000 steps to walk 1.6 km. The human being wear a boot with insole to protect feet when walking, playing and doing various activities. The boot with insole provides significant impact on the feet during these events and transmitted through the feet due to intense force and pressure. Measurements of plantar pressure are important for diagnosing lower limb disorders, designing footwear, injury prevention and applications in sports biomechanics. The objective of this study is to investigate the plantar pressure exerted on the feet during shod walking (wearing boot with three types of insoles); to identify effective insole for reducing plantar pressure during walking (wearing same boot with three insoles). Eighteen fits, healthy male adults volunteered for this study with mean and SD (mean±SD) age (36±9) years, height (169±4) cm, and weight (71±8) kg. During experiments, each volunteer underwent 5 min of treadmill walking (4.5 km/hr speed) with wearing of boot with varying types of insoles (Low-density polyurethane (LDPU) insole 1; High-density polyurethane (HDPU), insole 2; and Silicone rubber (SR), insole 3). Plantar pressures were measured by using a foot pressure measuring device. A paired t-test was conducted to observe significant changes in plantar pressures of different foot region (P&lt;0.05). Observations of the present study revealed that plantar pressures (N/cm²*s) were minimum during the use of LDPU insole than HDPU and SR insoles. It was also noticed that during the using of LDPU insole, less plantar pressure observed in the heel (3.84 ±1.16 in right foot) followed by forefoot (right 3.92±0.88), lateral (right 3.56±0.85), and medial foot (right 3.60±0.69). Hence, the present study suggested that using LDPU insole reducing the transfer of impact forces to the body/foot in comparison to HDPU and SR insoles during walking and minimizing the risk of foot-related injuries in long term use.

Bio-based rigid high-density polyurethane foams as a structural thermal break material

Sustainable development of building industry implies increasing usage of green materials. With this aim and for the intended application as a structural thermal break material, rigid high-density polyurethane foams have been manufactured using polyols derived from renewable resources - tall oil fatty acids. Thermal conductivity, compressive strength and stiffness of the foams of density ranging from ca. 100 to 680 kg/m3 have been determined. Comparison of the bio-based foams with reference foams derived from petrochemical resources demonstrated similar performance characteristics thus suggesting that bio-based foams can also serve as structural thermal break materials. Analytical models are shown to enable estimation of density dependence of the thermal and mechanical properties of foams using the respective experimentally determined characteristics of the monolithic polyurethane polymer.

Punching behaviour of foam filled modular sandwich panels with high-density polyethylene skins

Modular composite panels are being widely used for floors and roofs in prefabricated construction. Scissors shear and punching shear strength are two critical parameters for designing the sandwich panels under concentrated out of plane load. However, there are relatively few studies on scissors shear and punching shear strength of sandwich panels in literature in comparison with tensile strength and normal shear strength. In this paper, the scissor shear and punching behaviour of an innovative structural sandwich panel is investigated. The introduced system consists of a high-density polyurethane (PUR) foam core as well as two continuous layers of high-density polyethylene (HDPE) facings. Scissors shear strength and punching strength of these panels are studied through a creative experimental procedure. The scissors shear test is also simulated using non-linear finite element models and finally, the results are compared with each other. The results show that the first yield point of composite happens due to shear stress in foam. On the other hand, due to scissors shear, the foam is ruptured on two surfaces at about 45°. The scissors shear strength for the proposed panel, is determined to be 3.1 MPa, which is in good agreement with numerical results. In addition, the results revealed that using studliner skins can improve the scissors shear strength and punching shear strength of panels by about 34% and 22%, respectively.