Polyurethane Foam Composites Research Articles

Waste-wool/ polyurethane foam composites with stratified structure for potential sound absorption applications

The constrained absorption bandwidth of conventional sound-absorbing materials arises from their simplistic pore structure, which constrains their ability to absorb sound energy over a wide frequency spectrum. In this study, a wool-based bioplastic board (Wb) 1with excellent mechanical properties and durability was prepared by plasticising waste wool with glycerin. A novel sound-absorbing material with a layered structure was developed by combining waste polyurethane foam with Wb. This material ingeniously combines the dual advantages of porous-type and resonant-type sound absorption, endowing the composite with excellent acoustic absorption performance across a broad frequency band. The impact of Wb thickness and the number of alternate layers on the sound absorption performance was investigated. The results demonstrated that an increase in Wb thickness led to a decrease in sound-absorbing performance. When the number of alternating layers is three, the sound absorption coefficient of the composite reaches 0.61 in the frequency range of 2500 to 4500 Hz. Additionally, the maximum sound-absorption coefficient of composite materials with different layer numbers appears in different frequency ranges. Accordingly, by adjusting the thickness and varying the alternate layers of the Wb, it is feasible to satisfy the criteria for sound-absorbing materials in diverse architectural contexts. This not only achieves the environmentally friendly reuse of waste wool and polyurethane foam but also effectively overcomes the disadvantages of traditional sound-absorbing materials in terms of environmental impact and cost, bringing an eco-friendly and efficient solution to the field of architectural acoustics, especially in the application of ceiling and wall sound-absorbing materials.

Design of polyurethane composite foam obtained from industrial PET wastes and MXenes for EMI shielding applications.

The primary aim of this study was to synthesize and characterize polyurethane (PUR) foams derived from the depolymerization products of poly(ethylene terephthalate) (PET) and MXenes (Nb2AlC). The depolymerized PET products were produced through a zinc acetate-catalyzed glycolysis process using diethylene glycol (DEG) as solvent. These glycolysis products were then reacted with 4,4'-diphenylmethane diisocyanate (MDI), commercial polyols, and MXenes to produce the PUR foams. The resulting materials were characterized using FT-IR, SEM, EDX mapping, mechanical testing, thermal analysis, and electromagnetic interference (EMI) shielding assessments. The analysis revealed that specimens with a higher concentration of the filler (3.55%) exhibited superior mechanical properties, while the thermal behavior remained relatively unchanged. The sample containing 2.56% of MXenes showed significant potential as an effective EMI shielding material in the 8-9 GHz frequency range, while the blank sample provided the best performance between 9-13 GHz, mostly due to a bigger high-frequency absorption in the upper part of the X band. Regarding mechanical performance, the compression force increased slightly from 1013.31 N to 1013.71 N as the Mxenes concentration increased from 2.56% to 3.55%.

Sustainable rigid polyurethane foam composites based on used palm oil and turkey feather fiber: structural, morphological, thermal, insulation and mechanical properties

Sustainable rigid polyurethane foam composites based on used palm oil and turkey feather fiber: structural, morphological, thermal, insulation and mechanical properties

Viscoelastic Polyurethane Foam Biocomposites with Enhanced Flame Retardancy.

The growing demand for viscoelastic polyurethane foams creates a need for new sustainable raw materials that support cost-effective production while maintaining the desired material performance and fire safety standards. In this regard, our study aimed to develop viscoelastic polyurethane foam composites with reduced flammability and a high proportion of renewable raw materials. To achieve this, blackcurrant pomace, expandable graphite and a third-generation blowing agent were introduced to a viscoelastic polyurethane foam composition containing a reactive flame retardant in the formulation. The effects of the incorporated additives on the foaming process, flammability, chemical structure, cellular structure, thermal properties and physico-mechanical properties of the composites were determined. The results showed that the viscoelastic foam composite containing 30 php of blackcurrant pomace and 15 php of expandable graphite had a pHRRmax 52% lower than that of the reference material. The additional use of a blowing agent enhanced the flame-retardant effect of the materials, resulting in a 67% reduction in pHRRmax of the composite compared to the reference material. Moreover, the developed biocomposites exhibited promising limiting oxygen index values of 26-28%, compared to the 21% shown for the reference sample. Consequently, the best-performing biocomposites achieved the V-0 flammability rating according to the UL-94 standard. This study's results indicate the composites' high application potential due to their reduced flammability and the materials' desirable physical and mechanical properties.

Remarkable improvement in radiation shielding efficiency, thermal insulation performance and compressive strength of rigid polyurethane foam composites by synergetic effect of PbO and colemanite fillers

Developing radiation shielding materials is a critical phenomenon for protecting people and the environment with the increment in usage of nuclear technology in today's world. With this sense, PbO/colemanite-filled rigid polyurethane foams were fabricated by one-shut free rise method, and their performances were investigated via the advanced characterization techniques such as ATR-FTIR, SEM-EDS, TGA as well as thermal conductivity, universal mechanical and radiation shielding tests. The characteristic properties of the samples were evaluated in detail depending on the variation in the filler contents. The ATR-FTIR analysis illustrated that RPUF matrices exhibited good compatibility with the fillers by forming the secondary chemical bonds. Furthermore, SEM analysis revealed that the samples with low PbO/colemanite fillers exhibited fairly uniform and regular cellular morphology with anisotropic elliptical apparition thanks to synergetic catalytic effect of the filler particles, whereas, at high content, some local distortions with slightly chaotic appearance were observed accompanied by viewing the little ruptures and bursts in cell face and collapsed in cell plateau borders. TGA measurement indicated that the inclusion of the fillers into RPUF got worse the samples with comparison of neat RPUF due to the reduction in crosslinking density of the foam. Remarkable improvement (about 25 %) was also obtained in thermal insulation performance at the foam composites containing the fillers due to highly augmentation in number of closed cells and presence of more immobile CO2 gas inside the cells. Furthermore, high inclusion of the fillers in RPUF matrix improved compressive strength of the foams by nearly 15 % by enhancing the bending moment and rigidity of RPUF matrices via contributing to the overall stress dispersion. According to linear and mass attenuation coefficients results, the foam composites displayed excellent X-ray radiation shielding performance with increasing of PbO/colemanite content thanks to the density increment and presence of the atoms with high atomic number. Furthermore, at low photon energy levels, better shielding against X-ray radiation was obtained, while vice versa at high energy levels.

Synergistic Reinforcing Effect of Hazelnut Shells and Hydrotalcite on Properties of Rigid Polyurethane Foam Composites.

Recently, the development of composite materials from agricultural and forestry waste has become an attractive area of research. The use of bio-waste is beneficial for economic and environmental reasons, adapting it to cost effectiveness and environmental sustainability. In the presented study, the possibility of using hazelnut shell (HS) and hydrotalcite (HT) mineral filler was investigated. The effects of fillers in the amount of 10 wt.% on selected properties of polyurethane composites, such as rheological properties (dynamic viscosity, processing times), mechanical properties (compressive strength, flexural strength, hardness), insulating properties (thermal conductivity), and flame-retardant properties (e.g., ignition time, limiting oxygen index, peak heat release), were investigated. Polyurethane foams containing fillers have been shown to have better performance properties compared to unmodified polyurethane foams. For example, the addition of 10 wt% of hydrotalcite filler leads to PU composite foams with improved compression strength (improvement by ~20%), higher flexural strength (increase of ~38%), and comparable thermal conductivity (0.03055 W m-1 K-1 at 20 °C). Moreover, the incorporation of organic fillers has a positive effect on the fire resistance of PU materials. For example, the results from the cone calorimeter test showed that the incorporation of 10 wt% of hydrotalcite filler significantly reduced the peak of the heat release rate (pHRR) by ca. 30% compared with that of unmodified PU foam, and increased the value of the limiting oxygen index from 19.8% to 21.7%.

Ameliorating the comprehensive performance of rigid polyurethane foam insulating materials by green cork for building energy conservation

Biomass-modified polyurethane (PU) foam materials are vital to promote the sustainable development, but the balance between their mechanical strength and thermal insulating ability remains a challenge compared to the petrochemical-based PU foams. Herein, an appropriate amount of cork is introduced to fabricate PU composite foams with good thermal insulating performance and mechanical strength. The added cork could act as a nucleating agent during the foaming process, further tailor the foam structure and enhance their comprehensive performance. The optimal composite foams containing the peak cork usage of 24 % also belong to the high-efficiency insulating materials, with a thermal conductivity of 0.043 W m−1 K−1, a tensile strength of 0.17 MPa, a bending strength of 0.16 MPa, and good impact resistance. This research provides valuable insights for developing the comprehensive PU insulating materials by utilizing eco-friendly cork as substitutes, and offers a reference for highly efficient utilization of biomass resources.

Hybrid lattice structure with micro graphite filler manufactured via additive manufacturing and growth foam polyurethane

The utilisation of lightweight structures is a common practice across a range of disciplines, including the construction of light steel frames, sandwich panels, and transportation infrastructure, among others. The advantages of lightweight structures include design flexibility, weight reduction, and the sustainability of materials that can be easily recycled. However, these advantages also present significant weaknesses. Compared to solid materials with compact weight, lightweight structures do not have the same characteristics. With the reduction in material weight, the strength of the lightweight structure decreases significantly compared to solid materials. In this study, the lightweight structure was made using additive manufacturing and reinforced with solid Composite Polyurethane Foam reinforced with graphite filler expanded into the lightweight structure. The results showed that in the compression test, the mixture with 2 % graphite filler had the highest value of 2.5 kN. The highest hardness test on the specimen with a 2 % graphite mixture was 19.8 HA. FT-IR testing showed that the carbon bonds from graphite in the 2 % specimen had the highest intensity. The test results showed that the addition of Polyurethane Foam into the structure could enhance material strength effectively without adding significant material weight.

Preparations of Polyurethane Foam Composite (PUFC) Pads Containing Micro-/Nano-Crystalline Cellulose (MCC/NCC) toward the Chemical Mechanical Polishing Process.

Polyurethane foam (PUF) pads are widely used in semiconductor manufacturing, particularly for chemical mechanical polishing (CMP). This study prepares PUF composites with microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) to improve CMP performance. MCC and NCC were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), showing average diameters of 129.7 ± 30.9 nm for MCC and 22.2 ± 6.7 nm for NCC, both with high crystallinity (ca. 89%). Prior to preparing composites, the study on the influence of the postbaked step on the PUF was monitored through Fourier-transform infrared spectroscopy (FTIR). After that, PUF was incorporated with MCC/NCC to afford two catalogs of polyurethane foam composites (i.e., PUFC-M and PUFC-N). These PUFCs were examined for their thermal and surface properties using a differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), dynamic mechanical analyzer (DMA), and water contact angle (WCA) measurements. Tgs showed only slight changes but a notable increase in the 10% weight loss temperature (Td10%) for PUFCs, rising from 277 °C for PUF to about 298 °C for PUFCs. The value of Tan δ dropped by up to 11%, indicating improved elasticity. Afterward, tensile and abrasion tests were conducted, and we acquired significant enhancements in the abrasion performance (e.g., from 1.04 mm/h for the PUF to 0.76 mm/h for a PUFC-N) of the PUFCs. Eventually, we prepared high-performance PUFCs and demonstrated their capability toward the practical CMP process.

Giant Cushioning Effect in Facile Polymer/Nanoclay-Coated Flexible Polyurethane Foams.

In this work, a flexible polyurethane (PU) foam/polymer/clay (PUF/PAASep) composite is prepared via a simple dip-coating method. The composite exhibits excellent damping properties under quasi-static compression, vibration transmissibility, and impact resistance. For the composite preparation, sepiolite (Sep) dispersion in a polyacrylic acid (PAA) solution is first homogenized and evaluated using microscopy, and the obtained PAASep suspension is used to coat the PU foam uniformly for optimization of the quasi-static mechanical performance of the foam composites. The PU foam struts coated with 1 wt % PAA and 3 wt % sepiolite are strengthened, resulting in an 8-fold improvement of the stiffness and three-times increase of the impact force resistance compared to the uncoated PU foams. More importantly, the PU foam composites show a remarkable vibration damping capability, with the loss modulus 57 times that of the uncoated PU foams, enabled by micro friction and stick-slip effects mediated by the PAASep coatings. The facile prepared PAASep-coated PU foams have significant potential for cushioning, packaging, and broad engineering applications involving energy absorption.

Synthesis of bio-polyol-functionalized nanocrystalline celluloses as reactive/reinforcing components in bio-based polyurethane foams by homogeneous environment modification

Nanocrystalline Cellulose (NCC or CNC) is widely used as a filler in polymer composites due to its high specific strength, tensile modulus, aspect ratio, and sustainability.However, CNC hydrophilicity complicates its dispersion in hydrophobic polymeric matrices giving rise to aggregate structures and thus compromising its reinforcing action. CNC functionalization in a homogeneous environment, through silanization with trichloro(butyl)silane as a coupling agent and subsequent grafting with bio-based polyols, is herein investigated aiming to enhance CNC dispersibility improving the filler-matrix interaction between the hydrophobic PU and hydrophilic CNC. The modified CNCs (m_Ci) have been studied by XRD, SEM, and TGA analyses. The TGA results show that the amount of grafted polyol is strongly influenced by both its molar mass and OH number and the maximum amount of grafted polyol reaches up to 0.32 mmol per grams of functionalized CNC, within the explored conditions. The effect of different concentrations (1–3 wt%) of m_Ci on the physical, morphological, and mechanical properties of the resulting bio-based composite polyurethane foams is evaluated. Composite PU foams present compressive modulus up to 4.81 MPa and strength up to 255 kPa more than five times higher than those reinforced with unmodified CNC or with modified CNC in heterogeneous chemical environment. The improvement of mechanical properties of the examined PU foams, as a consequence of the incorporation of bio-polyols modified CNCs where polyol's OH groups interact with polyurethane precursors, could further broaden the use of these materials in building applications.

Flame retardant rigid polyurethane foam composites based on hexaphenoxycyclotriphosphonitrile: flame retardancy, combustion properties and pyrolysis kinetics

Flame retardant rigid polyurethane foam composites based on hexaphenoxycyclotriphosphonitrile: flame retardancy, combustion properties and pyrolysis kinetics

Flame‐retardant rigid polyurethane foam composites with the incorporation of steel slag and DMMP: A novel strategy for utilizing metallurgical solid waste

AbstractSteel slag (SS) as solid waste, has low resource utilization efficiency and seriously endangers environmental safety and human health. To explore the potential utilization value of SS and address the flammability challenge of rigid polyurethane foam (RPUF), with a novel flame‐retardant system composed by SS and dimethyl methyl phosphonate (DMMP) was explored. The DMMP/SS system effectively improved the high temperature stability of the RPUF composites. When the mass ratio of SS and DMMP was 1:1, the limiting oxygen index of RPUF/DMMP/SS reached 23.1 vol% and UL‐94 vertical combustion tests passed V‐2 level. Upon incorporation of 15 wt% DMMP, the initial decomposition temperature (T−5 wt%) reduced to 165.3°C, a decrease of 32.2%, while the Tmax2 and residue yield at 700°C exhibited negligible alteration. The peak heat release rate of RPUF/DMMP/SS composite (118.20 W g−1) was 11.02% lower than that of pure RPUF, indicating the significant enhancement of fire safety of the composites. Results confirmed that a synergistic flame‐retardant mechanism was existed between DMMP and SS in enhancing the fire safety of RPUF composite. Introducing a 20 wt% SS content reduces the ID/IG ratio to 1.85, thereby markedly enhancing its heat resistance. This work provides a new application field of SS and paves a novel approach to enhance fire safety of polymers.

Facile preparation of hydrophobic PPy@Si/PU foam for efficient oil adsorption by photothermal effects

AbstractExploring new oil absorbing materials with high adsorption rate remains a global challenge. Hydrophobic porous materials with photothermal conversion property are an attractive option to address oil spills. Herein, the organosilicon (hydroxyl‐terminal polydimethylsiloxane) was used to modify polyurethane (PU) foam to endow it good hydrophobic and compressible properties. Meanwhile, polypyrrole (PPy) with photothermal effect was introduced to endow PU foam with excellent photothermal properties. The PPy@Si/PU composite foams can reach 77.1 and 49.6°C under the laser and simulated sunlight (with the intensity of 1 kW/m2), respectively. The raised temperature of PPy@Si/PU foam makes it adaptable to reduce the crude oil's viscosity and improve its oil adsorption rate. The maximum oil adsorption rate of PPy@Si/PU foam can obtain 175% and 145% under the laser and simulated sunlight, respectively. Therefore, the PPy@Si/PU foam possesses effective photic‐driving oil adsorption capacity, which has a good prospect to be an efficient oil spills treatment material.

Ultrastrong and Thermo‐Remoldable Lignin‐Based Polyurethane Foam Insulation with Active‐Passive Fire Resistance

AbstractFoam thermal insulators are indispensable for prevailing energy‐saving engineering, however their widespread use brings intractability such as unsustainability, “white pollution”, and fire hazards. The emergence of bio‐based foams is highly appreciated, but the fabrication approaches are economically unattractive and/or the product properties are inferior, making their large‐scale implementation unviable. Herein, a versatile, thermally remoldable phosphate‐containing polyurethane composite foam (LPU‐G) is constructed from natural lignin and expanded graphite flakes via an atmospheric pressure and scalable one‐pot strategy. The optimal LPU‐G exhibits exceptional mechanical strength, capable of supporting over 6000 times its weight without significant deformation. Moreover, the LPU‐G demonstrates the desired multifunctionality in handling extreme circumstances, including humidity‐tolerant thermal insulation, superb water vapor barrier, and withstanding ≈1200 °C flame without ignition. Based on the “expansion‐conductivity” micro‐mechanism, LPU‐G is the first foam material to be constructed as a sensitive fire alarm system with an ultra‐long alarm time (>1800 s). Surprisingly, LPU‐G can be rapidly upcycled into recyclable bulk composites for a second life through simple thermo‐molding processes rooted in the multi‐dynamic behavior of the phosphate, carbamate, and hydrogen bonds. The easy‐to‐scale LPU‐G represents a new generation of thermal insulators that address concerns regarding unsustainability, high cost, fire risk, and inferior mechanical properties.

New Fire-Retardant Open-Cell Composite Polyurethane Foams Based on Triphenyl Phosphate and Natural Nanoscale Additives.

Despite the mechanical and physical properties of polyurethane foams (PUF), their application is still hindered by high inflammability. The elaboration of effective, low-cost, and environmentally friendly fire retardants remains a pressing issue that must be addressed. This work aims to show the feasibility of the successful application of natural nanomaterials, such as halloysite nanotubes and nanocellulose, as promising additives to the commercial halogen-free, fire-retardant triphenyl phosphate (TPP) to enhance the flame retardance of open-cell polyurethane foams. The nanocomposite foams were synthesized by in situ polymerization. Investigation of the mechanical properties of the nanocomposite PUF revealed that the nanoscale additives led to a notable decrease in the foam's compressibility. The obtained results of the flammability tests clearly indicate that there is a prominent synergetic effect between the fire-retardant and the natural nanoscale additives. The nanocomposite foams containing a mixture of TPP (10 and 20 parts per hundred polyol by weight) and either 10 wt.% of nanocellulose or 20 wt.% of halloysite demonstrated the lowest burning rate without dripping and were rated as HB materials according to UL 94 classification.

Harnessing Enhanced Flame Retardancy in Rigid Polyurethane Composite Foams through Hemp Seed Oil-Derived Natural Fillers.

Over the past few decades, polymer composites have received significant interest and become protagonists due to their enhanced properties and wide range of applications. Herein, we examined the impact of filler and flame retardants in hemp seed oil-based rigid polyurethane foam (RPUF) composites' performance. Firstly, the hemp seed oil (HSO) was converted to a corresponding epoxy analog, followed by a ring-opening reaction to synthesize hemp bio-polyols. The hemp polyol was then reacted with diisocyanate in the presence of commercial polyols and other foaming components to produce RPUF in a single step. In addition, different fillers like microcrystalline cellulose, alkaline lignin, titanium dioxide, and melamine (as a flame retardant) were used in different wt.% ratios to fabricate composite foam. The mechanical characteristics, thermal degradation behavior, cellular morphology, apparent density, flammability, and closed-cell contents of the generated composite foams were examined. An initial screening of different fillers revealed that microcrystalline cellulose significantly improves the mechanical strength up to 318 kPa. The effect of melamine as a flame retardant in composite foam was also examined, which shows the highest compression strength of 447 kPa. Significantly better anti-flaming qualities than those of neat foam based on HSO have been reflected using 22.15 wt.% of melamine, with the lowest burning time of 4.1 s and weight loss of 1.88 wt.%. All the composite foams showed about 90% closed-cell content. The present work illustrates the assembly of a filler-based polyurethane foam composite with anti-flaming properties from bio-based feedstocks with high-performance applications.

Construction and mechanism of efficient flame retardant system for alkali lignin‐enhanced rigid polyurethane foam

AbstractThe enhancement of flame resistance and mechanical strength is critical for the utilization of rigid polyurethane foam (RPUF) composites. In this study, the efficient synergistic flame‐retardant system, incorporating dimethyl methylphosphonate (DMMP) and expandable graphite (EG), with the addition of refined alkali lignin (A‐lignin) were aimed to superior fire resistance and mechanical integrity for RPUF. Furthermore, the flame retardancy and charring ability of obtained RPUF were obviously enhanced. Notably, an RPUF mixture containing A‐lignin, DMMP, and EG demonstrated substantial charring at elevated temperatures, improved limiting oxygen index, and met the UL‐94 V‐0 rating. Cone calorimeter test indicated that this formulation produces less heat and smoke than pure RPUF. The flame‐retardant efficacy of obtained RPUF was attributed to the formation of a protective char layer coupled with the free radical neutralization properties of DMMP, collectively enhancing the flame retardancy obtained RPUF. Additionally, this RPUF variant showed significant advancements in both mechanical and thermal performance. This study outlines a successful strategy for developing RPUF composites endowed with enhanced flame retardancy and mechanical strengths.

Activated carbon-reinforced polyurethane composite foams with hierarchical porosity for broadband sound absorption

The generation of various noise has caused severe noise pollution issues across a wide frequency spectrum, urgently requiring the development of sound-absorbing materials. Herein, we introduce composite polyurethane (PU) foams incorporating extremely nanoporous activated carbon (AC) including both meso- and macro-sized pores as an eco-friendly sound-absorbing material with superior and broadband sound absorption capabilities. The composite foam absorbs 95.8 % of the incident acoustic waves in the 2,000–5,000 Hz frequency range, i.e., the most sensitive range for the human auditory system, far outperforming pristine PU foam, which absorbs only 70.6 %. We demonstrate that sound absorption properties can be fine-tuned by adjusting the pore type and content of the AC. Significantly, the optimized composite foam structure absorbs 100 % of the incident waves at a specific frequency of 2,550 Hz. Collectively, we propose a master curve for the sound absorption properties derived from various composite foams, demonstrating that the properties can be precisely predictable and subsequently used for designing the pore characteristics and content of AC. Incorporating AC can also improve the mechanical properties of foams through interfacial adhesion phenomena. Our methodology provides valuable insights into the fabrication of composite foams with tunable sound absorption properties as a promising solution to noise pollution.

Preparation and properties investigation of flame‐retardant rigid polyurethane foam composites based on alkylphosphate oligomer

AbstractIn this work, FR‐PNX, an alkylphosphate oligomer was introduced into rigid polyurethane foam (RPUF) to fabricate FR‐PNX/RPUF composites. The flame retardancy, thermal stability, and combustion properties of composites were investigated by limiting oxygen index (LOI), thermogravimetric (TG), microcalorimetry (MCC), scanning electron microscopy (SEM), et al. The flame retardancy tests demonstrated that the incorporation of 50 phr of FR‐PNX yielded composites that the highest LOI of 23.6 vol% and achieved a V‐0 rating in the UL‐94 test. TG results indicated that FR‐PNX promoted the decomposition of FR‐RPUF in the process, but enhanced the high‐temperature stability of the composites. MCC analyses revealed that the addition of FR‐PNX suppressed the heat release during combustion, and FR‐PNX50/RPUF exhibited the lowest total heat release of 17.3 MJ/m2, a 35% reduction compared to the pure sample. Moreover, the peak heat release rate was decreased to 83.1 W/g, representing a 46.9% reduction compared to pure RPUF. SEM and Raman analyses of the char residue demonstrated that the incorporation of FR‐PNX facilitated the formation of a dense and continuous char layer in the FR‐RPUF, with increased graphitization degree of the char layer, thereby enhancing the composite's fire resistance through the development of a more stable fire barrier.