Polymer Foams Research Articles

High-brightness betatron emission from the interaction of a sub picosecond laser pulse with pre-ionized low-density polymer foam for ICF research

Direct laser acceleration (DLA) of electrons in plasmas of near-critical density (NCD) is a very advancing platform for high-energy PW-class lasers of moderate relativistic intensity supporting Inertial Confinement Fusion research. Experiments conducted at the PHELIX sub-PW Nd:glass laser demonstrated application-promising characteristics of DLA-based radiation and particle sources, such as ultra-high number, high directionality and high conversion efficiency. In this context, the bright synchrotron-like (betatron) radiation of DLA electrons, which arises from the interaction of a sub-ps PHELIX laser pulse with an intensity of 1019 W/cm2 with pre-ionized low-density polymer foam, was studied. The experimental results show that the betatron radiation produced by DLA electrons in NCD plasma is well directed with a half-angle of 100–200 mrad, yielding (3.4 ± 0.4)·1010 photons/keV/sr at 10 keV photon energy. The experimental photon fluence and the brilliance agree well with the particle-in-cell simulations. These results pave the way for innovative applications of the DLA regime using low-density pre-ionized foams in high energy density research.

Green fabrication for ultra-lightweight polyethersulfone/epoxy foam with excellent thermal insulation

High-performance polymers find extensive applications in heat-resisting materials, aerospace, and automobile manufacturing industry. However, due to their challenging processability, achieving low-density high-performance polymer foams for thermal insulation materials remains a big challenge. Furthermore, the preparation of lightweight special engineering plastic foams has garnered substantial attention in current research. Herein, we have developed polyethersulfone (PES)/bisphenol A epoxy resin (EP) blend foams with ultra-low density and good thermal insulation properties using a facile and environmentally friendly supercritical CO2 (ScCO2) foaming approach. The inherent compatibility between PES and EP resin enhanced the free volume of molecular chain in the matrix, subsequently improving the solubility and diffusion rate of carbon dioxide within the PES matrix. Consequently, in contrast to the maximum expansion ratio of 5.5 observed in pure PES, the PES/EP blend foams achieved an expansion ratio of up to 26 times, along with an improvement of the cell structure of PES and increasing cell density from 2.55 × 109 to 2.96 × 1010 cells/cm3. Furthermore, the thermal conductivity of PES-based foams notably decreased from 0.0667 to 0.0348 W/(m·K) with the addition of EP, possibly resulting from the low density (0.05 g/cm3) and high open-cell content (79.9%) of PES/EP blend foam. Our work presents a novel strategy for producing special engineering plastic foams with ultra-low density for thermal insulation, thereby expanding the potential application of special engineering plastic foam in areas such as biological scaffolds, absorbent material applications, and automotive interior industry.

Facile fabrication of lightweight and high expanded TPU/PBS bead blend foam with segregated microcellular network for reduced shrinkage and enhanced interface bonding

The emergence of expanded thermoplastic polyurethane foam beads (ETPU) has expanded the application range of polymer foam materials. However, most of the prepared bead foam products suffer from high shrinkage rate, high density, and poor interfacial bonding, severely affecting the mechanical stability and lightweighting of the products. Herein, this study constructed thermoplastic polyurethane/polybutylene succinate (TPU/PBS) bead blend foams with a segregated microcellular network structure (SMNS) for the first time, where the TPU/PBS continuous phase formed the SMNS and the bead phase was consisted of TPU foam beads. The results showed good interfacial bonding between the continuous and bead phases. By adding PBS to the continuous phase, the shrinkage percentage of TPU/PBS bead blend foam decreased from 79.19 % to 67.31 %, reduced by 15.0 %. In addition, the foam expansion ratio gradually decreased with increasing PBS content, dropping from 12.07 to 9.03. Moreover, TPU/PBS bead blend foams exhibited good energy absorption and mechanical stability without sacrificing thermal insulation performance. This work effectively reduced the shrinkage of TPU based foam materials, offering a simple and economical solution for the preparation of dimensionally stable, well-interfaced, and lightweight polymer foams.

Assessment of frequency and amplitude dependence on the cyclic degradation of polyurethane foams

AbstractMany energy absorption applications utilize flexible polymeric foams for their viscoelastic properties. It is desired that the material will perform consistently across repeated compression cycles. This study examines the effect of fatigue at low strain rates on the viscoelasticity of open‐cell polyurethane foam. Six polyurethanes of the same base composition with two porosities (70% and 80%) and three chemical indexes (79i, 100i, and 121i) are tested. Large deformation cyclic compression of the foams is conducted on a universal testing system (UTS). These data are then post‐processed leveraging dynamic mechanical analysis Fourier transform rheology to characterize changes in the viscoelasticity of the materials over fatigue cycles. Results show that foams can increase or decrease in stiffness up to 10% over 104 cycles. Specifically, higher chemical index, higher excitation frequency, and larger excitation amplitude correlate with a more pronounced decrease in stiffness. Damping can also change by 15% and correlates with chemical index and excitation frequency. Consequently, the findings suggest that internal foam structure and bulk material properties as well as applied loading parameters affect the viscoelastic fatigue response of flexible polymeric foams.

Fabrication of Triblock Elastomer Foams and Gelation Studies for Oil Spill Remediation.

Polymeric foamed materials are among the most widely utilized technologies for oil spill accidents and releases of oil-contaminated wastewater oil due to their porosity to absorb and separate oil/water effectively. However, a major limitation of traditional polymeric foams is their reliance on an ad/absorption mechanism as the sole method of oil capture, leading to potential oil leakage once their saturation point is exceeded. Tri-block polymer styrene-ethylene-butylene-styrene (SEBS) is a fascinating absorbent material that can bypass this limitation by both capturing oil and providing a sealing mechanism via gelation to prevent oil leakage due to its unique chemical structure. SEBS foams are produced via simultaneous crosslinking and foaming that results in an impressive expansion ratio of up to 15.2 with over 93% porosity. Most importantly, the SEBS foams show great potential as oil absorbents in spill remediation, demonstrating rapid and efficient oil absorption coupled with superhydrophobic properties. Moreover, the unique interaction between the oil and SEBS enables the formation of a physical gel, acting as an effective barrier against oil leakage. These findings indicate the potential for commercializing SEBS foam as a viable option for geotextiles to mitigate oil spill concerns from infrastructures.

Effect of compressibility on the mechanics of hyperelastic membranes

Elastic membranes are usually studied assuming material incompressibility. However, in several applications they are made of compressible materials such as polymeric foams, hydrogels, and certain kinds of elastomers. Only a few works attempted to incorporate volume changes into membrane problems, but with significant limitations. The models proposed were designed for nearly incompressible materials and lacked a foundation in experimental data, leading to results of limited value. In this work, we investigate the effect of compressibility in membrane problems adopting a consistent model based on the real response of materials to large volume changes. We consider three benchmark problems of nonlinear elasticity: (i) inflation of a circular flat membrane; (ii) inflation of a thin-walled cylindrical tube; (iii) inflation of a thin-walled spherical balloon. Four types of materials divided by increasing degree of compressibility are studied. The results indicate that volumetric deformations have a significant impact on both the limit pressure and the deformed shape. The proposed solutions represent benchmarks for developing new applications of compressible membranes made of polymeric foams and hydrogels, playing an increasingly important role in engineering technologies.

Carbohydrate-Based Reprocessable and Healable Covalent Adaptable Biofoams.

Polymeric foams derived from bio-based resources and capable of self-healing and recycling ability are of great demand to fulfill various applications and address environmental concerns related to accumulation of plastic wastes. In this article, a set of polyester-based covalent adaptable biofoams (CABs) synthesized from carbohydrates and other bio-derived precursors under catalyst free conditions to offer a sustainable alternative to conventional toxic isocyanate-based polyurethane foams is reported. The dynamic β-keto carboxylate linkages present in these biofoams impart self-healing ability and recyclability to these samples. These CABs display adequate tensile properties especially compressive strength (≤123MPa) and hysteresis behavior. The CABs swiftly stress relax at 150°C and are reprocessable under similar temperature conditions. These biofoams have displayed potential for use as attachment on solar photovoltaics to augment the output efficiency. These CABs with limited swellability in polar protic solvents and adequate mechanical resilience are suitable for other commodity applications.

Optimizing the photocatalytic properties of macroporous geopolymer foam: Influence of SILAR-technique synthesis conditions

Macroporous cross-linked materials such as 3D honeycomb foams are used as substrates for heterogeneous photocatalysis. They offer a number of interesting properties. They are highly open-porosity substrates, guaranteeing optimum mass and radiation transfer, making them ideal for photo-conversion applications such as photo-oxidation or photo-reduction, which take place in photo-reactors for pollutant degradation or solar fuel production. Many cross-linked supports such as polymeric and metallic foams studied in the literature have revealed photocatalytic capacities similar to those obtained for the catalyst nanoparticle suspensions used as a reference. To reduce the production costs of this type of material, geopolymers, widely used in civil engineering, offer a wide range of properties suitable for shaping cellular foams. In addition to their low cost and mechanical properties, it is also possible to impart porous properties and modulate their characteristics according to the synthesis operating conditions so as to elaborate macroporous cellular foams. In this study, we propose to investigate the photocatalytic properties of honeycomb geopolymer foams coated with a catalyst: ZnO. To achieve ZnO deposition, the SILAR technique was applied by modifying the key synthesis operating conditions, i.e. precursor concentration and the number of quenching cycles applied. The results obtained make it possible to define the optimum operating conditions (pH, temperature) and, above all, the number of cycles and precursor concentration required to obtain the best photocatalytic efficiency. These innovative and promising materials, little studied in the literature, are prime candidates for solar photo-conversion applications.

Sustainable CO2-based PPC foams functionalized with enhanced glass transition temperature by a controllable hydrogen bonding complexation

Biodegradable polypropylene carbonate (PPC) has garnered significant attention for its commendable biodegradability and its role in mitigating the greenhouse effect. However, the inherent drawback of PPC, its low glass transition temperature (Tg), severely restricts its widespread use, especially at room temperature. In this study, we explore the utilization of MXene-OH/CNTs-OH (CM) hybrids, which encompass hydroxylated one-dimensional carbon nanotubes (CNTs-OH) and the two-dimensional layered structure of Ti3C2 (MXene-OH), to enhance the properties of PPC through hydrogen bonding complexation. By adjusting the content of nanofillers, the resulting PPC/CM composites demonstrate improved Tg, mechanical strength, and exceptional capability in supercritical foaming. Both experimental and theoretical analyses confirm that the CM crosslinking mechanism significantly elevates the Tg of the composite to 37.3 °C, while also enhancing tensile strength by 23.7% and antibacterial activity by 99.6%. This study presents a straightforward and practical method for developing functionalized, sustainable polymer foams with enhanced characteristics, poised for a diverse range of applications.

Supramolecular metallic foams with ultrahigh specific strength and sustainable recyclability

Porous materials with ultrahigh specific strength are highly desirable for aerospace, automotive and construction applications. However, because of the harsh processing of metal foams and intrinsic low strength of polymer foams, both are difficult to meet the demand for scalable development of structural foams. Herein, we present a supramolecular metallic foam (SMF) enabled by core-shell nanostructured liquid metals connected with high-density metal-ligand coordination and hydrogen bonding interactions, which maintain fluid to avoid stress concentration during foam processing at subzero temperatures. The resulted SMFs exhibit ultrahigh specific strength of 489.68 kN m kg−1 (about 5 times and 56 times higher than aluminum foams and polyurethane foams) and specific modulus of 281.23 kN m kg−1 to withstand the repeated loading of a car, overturning the previous understanding of the difficulty to achieve ultrahigh mechanical properties in traditional polymeric or organic foams. More importantly, end-of-life SMFs can be reprocessed into value-added products (e.g., fibers and films) by facile water reprocessing due to the high-density interfacial supramolecular bonding. We envisage this work will not only pave the way for porous structural materials design but also show the sustainable solution to plastic environmental risks.

A review on the mechanical behaviour of microcellular and nanocellular polymeric foams: What is the effect of the cell size reduction?

Research on nanocellular foams is motivated in part by the promise of physical properties, in particular mechanical properties, that can go beyond the classical mechanical framework. However, due to the difficulty in obtaining foams of a given density but different cell sizes, determining the effect of cell size on the mechanical properties of polymer foams remains a challenge. To overcome this difficulty, studies on the mechanical behaviour of mesocellular, microcellular and nanocellular polymer foams have been compiled in this review article. After describing the different cellular structures between meso-, micro- and nanocellular foams, the mechanical properties are examined as a function of relative density and cell size. It is shown that for small strains and at low strain rates, nanocellular foams exhibit mechanical behaviour predicted by the Gibson and Ashby model. Relative density remains the first important factor to be taken into account when studying the Young’s modulus and buckling stress of nanocellular foams. The focus then shifts to fracture properties, as microcellular foams have already been shown to be far superior to more conventional foams. As studies are still scarce and different methodologies have been used, no general conclusions can be drawn. However, the fracture and impact properties could be greatly improved by this change in scale. The local confinement of molecular chains in polymeric nanocellular foams or the relaxation of the triaxial stress state in front of the crack tip could explain these observations.

Bayesian calibration of constitutive models for polymeric foams

Porous materials are traditionally used for their sound absorption and insulation properties. Over the past decade, more attention has been given to their elastic and damping properties. There is a particular interest in the automotive industry to replace heavy layers (consisting of constrained viscoelastic rubber layers) with felts or foams evidencing high damping capabilities. Hence, characterizing efficiently the viscoelastic properties of porous materials is crucial for quality control and further improvements in product development and fabrication. In this sense, the main contribution of this work is to propose a stochastic strategy to determine the constitutive equations describing the viscoelastic behaviour of foams. Vibration tests are carried out on a two-layer panel containing a free-layer of a foam. A finite element model is developed considering only the viscoelasticity of the porous skeleton, neglecting the influence of the fluid phase. A fractional derivative model is calibrated and validated for two types o foam based on a Bayesian framework. The models indicate that the reconstitute porous rubber presents absolute values of the complex modulus greater than the ones provided by the closed-cell polyurethane foam and its energy dissipation is greater the one provided by the closed-cell polyurethane one.

A critical review on analysis of sand producing and sand-control technologies for oil well in oilfields

Sand production in oil wells seriously affects the production of oil and gas in oilfields. Although conventional sand-control techniques can effectively prevent sand production, it may also limit the productivity of oil wells. Fracturing and packing sand control technology changes the distribution of pressure and flow in the wellbore, while foam polymer resin diversion technology reduces the anisotropy of reservoir permeability and increases the area of oil leakage in the reservoir, both achieving the goal of sand control and increased production. The sand-free production rate is successfully increased thanks to zeta potential sand control technology, which modifies the formation’s sand potential and causes the sand to agglomerate without harming the reservoir. This article first looks into the causes of sand production in oil and gas wells before examining the fundamentals, implementation strategies, and effects of traditional sand control techniques, fracturing and filling sand control technology, foam polymer resin diversion technology, and Zeta potential sand control technology. In this article, the experience of sand control technology in actual oil field applications is summarized, explained in detail, and the future development possibilities of sand control technology are discussed.

Polymer foam fabricated via surfactant foaming method enables high-performance solar interfacial evaporation

Solar interfacial evaporation is considered as a low energy consumption, low cost, and sustainable desalination technology. However, its practical application is still limited by complex preparation processes and low photothermal conversion efficiency. In this work, we report novel polymer foam (Agar/SA/GO-Ag composite foam). It is prepared by simple and convenient surfactant foaming and in-situ reduction methods and consists of graphene oxide (GO) and silver nanoparticles (Ag NPs) (photothermal conversion medium) as well as Agar and sodium alginate (SA) (basic skeleton) for use in solar-powered interfacial evaporation systems. The prepared foam has excellent wettability and achieves 96.7% light absorption in the full spectrum range. A high evaporation rate of 2.55 kg·m−2·h−1 and a high evaporation efficiency of 97.3% were obtained under the conditions of simulated sunlight (1.0 kW·m−2). Moreover, the foam exhibits good reusability in a 10-cycle test without obvious attenuation in evaporation performance. Foam is used for seawater desalination and wastewater purification, and the treated water meets the water quality standards of the World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA). In short, this work demonstrates a sustainable strategy for low-cost and efficient solar-powered clean water production.

Computational design of isotropic and anisotropic ultralow thermal conductivity polymer foams

Current state-of-the-art commercial polymer thermal insulation foam exhibits a thermal conductivity of 24 mW⸳m−1⸳K−1 (equivalently thermal resistivity of R-6/in.), similar to that of static air. To further optimize building energy efficiency, achieving even lower thermal conductivity is needed, which is, however, highly challenging. This paper presents computational evidence that demonstrates the feasibility of achieving an ultra-low thermal conductivity of less than 14.4 mW⸳m−1⸳K−1 (equivalently R-10/in.) using isotropic and anisotropic foam cell designs. For the isotropic design, we have identified analytical effective medium approximation (EMA) models within the accuracy of ±5% as finite element analysis (FEA) in predicting the effective thermal conductivity of foams with various porosities and filler gases. For the anisotropic design, we have developed and validated new EMA models against FEA in predicting the effective thermal conductivity of general anisotropic cuboids and Voronoi foams. For both isotropic and anisotropic designs, the design spaces for 18, 16, and 14.4 mW⸳m−1⸳K−1 (equivalently R-8, R-9 and R-10/in.) using various filler gases are obtained. It is found that polymer foams can be improved to achieve ultralow thermal conductivity by reducing CO2 concentration, reducing radiation, increasing porosity, and using anisotropic pore geometry. These findings contribute to the development of highly efficient thermal insulation materials, enhancing building energy efficiency and promoting sustainable construction practices.

Neural network-driven interpretability analysis for evaluating compressive stress in polymer foams

This research presents a method to analyze how neural network models, applied to Expanded Polypropylene and Expanded Polystyrene foams, predict their compressive stress responses. By using SHAP values and Partial Dependence Plots, the study elucidates the models’ decision-making processes. It focuses on three main features for both materials: density, loading rate, and strain, with an additional feature concerning loading and unloading for Expanded Polystyrene foam. The findings highlight that increased density and loading rate are closely correlated with higher compressive responses, and strain emerges as the most influential factor for the response of both materials. Partial Dependence Plots reveal a linear relationship with density, whereas other variables demonstrate non-linear relationships. These results validate the use of neural networks in analyzing material behavior, showing that the models’ outputs are in line with empirical observations. In conclusion, as presented, the integration of interpretability tools with neural network models offers a robust method for material response analysis, contributing to a deeper understanding of material science.

A Single Component, Single Layer Flexile Foam Evaporator with the Higher Efficiency for Water Generation.

One of the greenest and promising ways to solve the problem of freshwater crisis is surface solar steam generation from seawater. A great number of photothermal materials with multi-component and multi-layered delicate yet complex structures often suffer from either low evaporation rate or high energy loss. Here, this work presents a single component foam evaporator with steam generation rate of up to 4.32kg m-2 h-1 under 1 sun irradiation. The evaporator is constructed from an aniline oligomer as a single light-absorbing component, covalent linked with polyethylene glycol to form a monolithic polymer foam. Floating on the seawater, the foam has absorbance of 99.5% over the entire solar spectral range and low thermal conductivity (0.0077W K-1m-1) that effectively retains heat in the material and at the interface. After 3 months of continuous outdoor natural sunlight irradiation, the evaporator maintains a stable and durable evaporation rate. Moreover, the materials have good mechanical properties (7.48MPa young's modulus and 57.38% elongation at break) and excellent chemical resistance in 10 common organic solvents and aqueous solutions of pH = 1 to 14. This study provides a new system and strategy for desalination, steam power generation, treatment of polluted water and sewage, etc.

Survival of Alphitobius diaperinus Larvae Reared in Styrofoam and Polymeric Foam Diet

Survival of Alphitobius diaperinus Larvae Reared in Styrofoam and Polymeric Foam Diet

Foaming of thermoplastic polyurethane using supercritical CO2 AND N2: Antishrinking strategy

The transformation of thermoplastic polyurethanes into polymeric foams is attracting great interest nowadays. However, this technology has some challenges that it is necessary to resolve, being one of the most important the shrinkage suffered by the polymeric foams over time. For that reason, this work explores several alternatives to mitigate this phenomenon. These alternatives are divided into two groups: on the one hand, the refoaming of the shrunken foams using supercritical CO2 and N2 was explored; on the other hand, the foaming using mixtures of supercritical CO2 and N2 as foaming agents was carried out. After experiments, it was seen that, the refoaming with N2 of shrunken foams obtained by supercritical CO2 technology can increase and keep constant the initial expansion ratio of the shrunken foams. Moreover, it was also observed that ratios of CO2/N2 between 80/20 and 60/40 can avoid the shrinking issues suffered by the polymeric foams after foaming using supercritical technology.

Large-scale and facile fabrication of phenyl-containing silicone foam materials with lightweight, wide-temperature flexibility and tunable pore structure for exceptional thermal insulation

Silicone foam materials with unique inorganic/organic molecular networks and porous structures are widely used in many emerging fields from aerospace to new energy fields. However, current silicone foam materials still show some limitations, such as the relatively high-density values of >200 mg cm−3, complex fabricating process and difficulty in tailoring pore structure. Herein, we report a large-scale and facile fabricating strategy to prepare phenyl-containing silicone foam materials (PhSiRF) with ultra-lightweight feature, tunable pore structure, and excellent wide-temperature mechanical flexibility. Interestingly, the presence of phenyl groups onto the Si–O–Si backbone tailors the chemical foaming rate probably due to the steric hindrance effect, thus producing tunable pore size distributions in the range of 180–500 μm. Typically, the PhSiRF with 50 % phenyl groups not only shows a very low density of ∼100 mg cm−3, superior to previous silicone foams and composites, but also exhibits wide-temperature flexibility (stable compressive strain of 80 % from −90 to 210 °C) and excellent thermal insulation performance, which outperforms those of conventional polymer foams including polyurethane, polyethylene and melamine foams. Based on the structure observation and theory analysis, the influence of different pore morphological structures on the thermal insulation performance is discussed and demonstrated. Clearly, this work provides a new yet simple method for developing high-performance silicone rubber foam materials for promising thermal insulation applications.