The objective of this research was to assess the utility of dynamic mechanical thermal analysis (DMTA) in investigation of polymer-based foams for the potential use in anti-impact protection systems. Therefore, three different types of specimens were chosen (polyolefin, polyurethane, rubber) and examined with: i. amplitude (1-100 µm), ii. frequency (0.1-100 Hz), iii. temperature (-60-60°C) sweeps. These DMTA modes enabled to successfully mimic: i. deformation during the impact, ii. foam behaviour while worn (low frequencies) and hit (high frequencies), iii. summer and winter conditions. Among others, investigation of loss angle tangent (tanδ), being a ratio between loss (E'') and storage (E') moduli, favourably revealed an inverse relationship between the tanδ at 100Hz and maximum impact force needed to destroy the specimen. It was also established that a compromise between elastic (E') and viscous (E'') needs to be maintained to preserve shape stability while dissipating energy to achieve the high compressive strength (CS), e.g., more viscous rubber foam - CS of approx. 86kPa (tanδ = 0.44), rigid polyolefin foam - CS at the level of 36kPa (tanδ = 0.15). Therefore, DMTA successfully served as a complementary tool, providing mechanistic insight that supported and explained trends observed in conventional compression and impact testing.

Polyurethane (PU) foams are widely applied in cushioning, packaging, and construction, but their reliance on petroleum-based feedstocks and limited durability raises sustainability concerns. This study investigates the incorporation of ground tyre rubber (GTR) into flexible PU foams to enhance performance while promoting circular economy goals. Foams were synthesized via the free-rise method using polyethylene glycol (PEG 400) and isophorone diisocyanate (IPDI), with GTR fillers (≤0.4 mm) and silicone oil surfactant. Fourier-transform infrared spectroscopy confirmed successful urethane network formation, while scanning electron microscopy revealed that GTR disrupted cellular morphology, increasing porosity and heterogeneity. Mechanical analysis showed a substantial decline in compressive strength and modulus with increasing filler loading, attributed to poor filler matrix compatibility and uneven dispersion. Thermal analysis highlighted a dual effect where GTR suppressed the glass transition temperature, reflecting reduced microphase separation, yet improved thermal stability by delaying degradation onset and increasing residual char yield. Silicone oil partially mitigated structural collapse by refining cell morphology and enhancing compressive behavior. The results showed a trade-off between sustainability-driven waste rubber utilization and foam integrity. While GTR incorporation advances responsible resource recovery and contributes to Sustainable Development Goals (SDGs), unmodified fillers compromise mechanical reliability, limiting high-performance applications. Future work should emphasize interfacial engineering, including surface modification and compatibilizer integration, to reconcile environmental imperatives with performance requirements.

Negative-pressure induced controllable foaming reaction for ultralight and flame-retardant phenyl-containing silicone rubber foam nanocomposites modified with low content of graphene oxide

Using an antibacterial agent in rubber normally affects the material’s physical properties. This study assesses the possibility of improving the antibacterial activity of natural rubber (NR) foam while maintaining the physical characteristics of the sample. The physical properties were controlled based on the classifications stated in ASTM D1056. The antibacterial agent used in this work was Triclosan where it was varied from 0–0.8 phr in NR foams. The results found that increasing the content of Triclosan increased the inhibition zone of S. aureus and E. coli . Upon inclusion of Triclosan, there was little effect on the foam classification. At low content of Triclosan, i.e., 0.2 and 0.4 phr, the grade number was maintained as 2A3 grade. However, the grade was changed from 2A3 to 2A4 when adding Triclosan at 0.6 and 0.8 phr. It is clear that adding an antibacterial agent does influence the characteristics of the foam.

Frequent oil spills are a major contributor to water pollution, leading to numerous environmental and ecological issues and posing risks of fire and explosions. Hence, there is an imperative to develop a cost-effective and exceptionally functional absorbent material for separating oil and water. In this study, a simple, low-cost, environmentally friendly, biodegradable, highly hydrophobic, and super oleophilic graphitic carbon nitride (g-C3N4) based natural rubber foam is introduced for oily wastewater treatment. The g-C3N4 was coated onto the natural rubber foam using a simple dip-coating method. The resulting hydrophobic g-C3N4-coated foams exhibit highly hydrophobic and superoleophilic surface properties with contact angles of 144.1 ± 2° and 0°, respectively. These foams exhibited more than 100% oil absorption capacity, effectively absorbing a variety of oils and solvents like olive oil, acetone, methanol, ethanol, etc. and successfully separating oil and solvent mixtures from water. Hence, the developed g-C3N4-based natural rubber foam absorbent has excellent potential for oil/water separation applications.

Complex porous natural rubber foam composites with modified titanium dioxide for photocatalytic xylene removal

Formation of layered cell structure in silicone rubber foam via supercritical CO2-induced crosslinking

Background: The vestibular Romberg test, which assesses the deterioration of balance while standing on rubber foam with closed eyes, is a well-established method in the physical neurological assessment of patients with peripheral vestibulopathy. This study aims to determine whether it can differentiate peripheral vestibulopathy from its main differential diagnosis, namely sensory ataxia, as both conditions typically present with a positive classical Romberg test. Methods: Static balance was assessed in three groups: patients with peripheral vestibulopathy, patients with pure sensory neuropathy, and healthy age-matched controls. Participants stood quietly on a force platform under varying visual and proprioceptive feedback conditions. Conventional and advanced postural sway metrics were investigated to establish a quantitative analogy to both the clinical Romberg and vestibular Romberg tests. Results: Posturographic analysis revealed that, in contrast to healthy controls, patients with vestibular disorders exhibited higher vestibular Romberg quotient values. However, the classical vestibular Romberg quotient did not show diagnostic discrimination between vestibulopathy and sensory neuropathy patients. This lack of discrimination was mainly due to the increased body sway observed in all patient groups under the "eyes open" condition. Nevertheless, a refined vestibular Romberg quotient-comparing standing on foam versus standing on firm support with eyes closed-was able to reliably distinguish vestibulopathy from sensory ataxia. This distinction was evident in both conventional linear sway and spectral postural sway metrics. Conclusions: We conclude that a refined Romberg test, performed solely under conditions of visual deprivation, offers valuable classification potential in differentiating peripheral vestibulopathy not only from healthy controls but also from patients with disequilibrium due to sensory loss.

Abstract A novel class of eco-friendly natural Eucommia rubber (ER)/natural rubber (NR) foam composites with tunable shape memory and oil adsorption capabilities has been successfully developed through optimized vulcanization-foaming integration technology. This study utilized comprehensive characterization techniques such as universal testing machine measurements, scanning electron microscopy, and complementary analytical methods to systematically evaluate the foamed composites’ mechanical properties, shape memory behavior, and oil absorption characteristics. Through these advanced characterization approaches, we elucidated the precise influence of foaming agent H concentration on both the macroscopic performance and microstructural evolution of the foam composites. When increasing the foaming agent H content, the cellular morphology exhibited substantial expansion. This structural transformation was accompanied by a marked density reduction from 0.52 g/cm3 to 0.18 g/cm3, concurrently driving a corresponding decline in tensile strength from 11.1 MPa to 4.3 MPa. Beyond these fundamental property variations, the composites manifested distinctive functional characteristics including notable shape memory effects and temperature-responsive oil absorption capabilities. Particularly noteworthy was the precisely tunable oil adsorption performance, which could be strategically modulated through controlled physical state transitions of the composites under thermal stimuli. This thermal responsiveness establishes promising potential for intelligent material applications requiring adaptive oil–water separation functionality.

Foamed asphalt cold recycled mixtures can provide an effective approach for the reutilization of reclaimed asphalt pavement (RAP), but conventional asphalt foaming technology primarily exploits matrix asphalt as the raw material. To address this issue, this study explores rubberized asphalt with cold recycling technology to develop a foamed rubber asphalt cold recycled mixture (FRCM). The semi-circular bending (SCB) test was employed to investigate its cracking resistance. Load-crack mouth opening displacement (CMOD)-time curves under various temperatures were analyzed, and digital image technique was resorted to monitor crack propagation and growth rates. Fracture toughness, fracture energy, and flexibility index were compared with those of traditional foamed matrix asphalt cold recycled mixture (FMCM). The results show that, under the same test temperature, the FRCM exhibits slower crack propagation; larger peak load; and higher fracture toughness, fracture energy, and flexibility index in comparison with the FMCM. These improvements are more pronounced at low temperatures. For both mixtures, fracture toughness and fracture energy are decreased with increasing the temperature, while the flexibility index shows the opposite trend. The rigid zone accounts for a larger portion of fracture energy at low temperatures. The findings provide technical references for improving the cracking resistance of cold recycled asphalt layers using rubberized asphalt.

This research investigates the influence of the quantity and type of flame retardants and blowing agents on the thermal insulation properties of foam prepared using STR 20 block rubber. Supercell DPT was employed as a blowing agent, and aluminium trihydroxide (ATH) and chlorinated polyethylene (CPE) functioned as flame retardants, with their concentrations adjusted to 10 and 20 parts per hundred rubber (phr). All rubber compound formulations were prepared via a semi-EV sulphur vulcanization system. The expansion ratio in a compression mould and curing properties of the rubber compounds were determined at 170 °C. The experimental results revealed that increasing the amount of blowing agent from 3 to 8 phr led to a maximum increase of 110% in the pore size within the foam structure. Both ATH and CPE at a concentration of 10 phr are sufficient to make all insulating foam formulations pass the UL-94 HBF flammability test. The natural rubber foam applied with 8 phr of blowing agent and 10 phr of ATH flame retardant exhibited the lowest water absorption at 0.46%. It also demonstrated good durability at a maximum temperature of 84 °C for 7 days, and the lowest thermal conductivity (K-value) of 0.0648 W/m·K according to ASTM C518-10.

Effects of MIL-88A/Al2O3 on the flame retardancy and smoke suppression of silicone rubber foams

Protein-based foams are potential sustainable alternatives to petroleum-based polymer foams in e.g. single-use products. In this work, the biodegradation, bioassimilation, and recycling properties of glycerol-plasticized wheat gluten foams (using a foaming agent and gallic acid, citric acid, or genipin) were determined. The degradation was investigated at different pH levels in soil and high humidity. The fastest degradation occurred in an aqueous alkaline condition with complete degradation within 5 weeks. The foams exhibited excellent bioassimilation, comparable to or better than industrial fertilizers, particularly in promoting coriander plant growth. The additives provided specific effects: gallic acid offered antifungal properties, citric acid provided the fastest degradation at high pH, and genipin contributed with cross-linking. All three additives also contributed to antioxidant properties. Dense β-sheet protein structures degraded more slowly than disordered/α-helix structures. WG foams showed only a small global warming potential and lower fossil carbon emissions than synthetic foams on a mass basis, as illustrated with a nitrile-butadiene rubber (NBR) foam. Unlike NBR, the protein foams could be recycled into films, offering an alternative to immediate composting.

Abstract The popularity of foam and wearable electronic materials requires lightweight materials with high electromagnetic interference (EMI) shielding performance. Silicone rubber foam is a lightweight, compression‐shrinkable, porous polymer that fulfills this need. In this work, a simple and easy‐to‐process operation mode was proposed. The silicone rubber/calcium carbonate (CaCO3)@stearic acid (SA)/multi‐walled carbon nanotubes (MWCNTs)@γ‐aminopropyl triethoxysilane (KH550) EMI shielding composite conductive foam with a lightweight gradient structure was prepared. The layered material is divided into three layers: A, layer of lightweight foam; B, layer of bonding; and C, layer of conductive. A layer reduces density; C layer provides strong electromagnetic (EM) shielding; B layer eliminates defects and achieves tight adhesion between layers. Gradient foam material is light has high compression, and has strong EM shielding, with a density of 0.500 g/cm3, a directional tensile strength of 1.72 MPa, a compressive strength of 0.71 MPa, and an EM shielding value of 43.26 dB. Subsequent studies showed that the EMI shielding effectiveness (SE) value of gradient foam materials increased with the increase of conductive layer thickness, reaching 85.10 dB at 3.0 mm. This is attributed to the aspect ratio structure of MWCNTs, which can construct a three‐dimensional conductive network at low content and thin thickness. This material is lightweight and has high EM shielding performance, with broad application prospects in the fields of seismic and pressure reduction, EMI resistance, and other valuable instruments.Highlights Preparation of low‐cost foam materials filled with calcium carbonate. Filling of MWCNTs to form an ideal three‐dimensional conductive network. Introduction of an adhesive layer to better bond the foam layer to the conductive layer. Build a three‐layer structure to enhance EMI performance.

Disposing of waste tyres in landfills poses significant environmental hazards, making recycling a crucial alternative. Rubberised concrete has been found to exhibit lower density and better thermal insulation performance than conventional concrete. In order to maximise the potential of thermal insulation of rubberised concrete, this study investigates the mechanical and thermal properties of foamed rubberised polypropylene fibre concrete (FRPFC). FRPFC was produced using a mix of crumb rubber (CR) granules, polypropylene fibres, and foam, targeting a density of 800 kg/m3, with CR substituting sand at varying levels. Compressive strength, flexural strength, splitting tensile strength, and thermal conductivity of FRPFC were evaluated. The results demonstrate that increasing CR granule content enhances compressive strength due to reduced porosity from lower foam usage. For instance, compressive strength improved by 55% (2.64 to 4.10 MPa) as CR granule content increased from 0% to 80%. Similarly, flexural strength and splitting tensile strength increased by 55% (1.61 MPa to 2.49 MPa) and 39% (0.41 MPa to 0.57 MPa), respectively, when CR content rose from 0% to 100% at a water-to-cement ratio of 0.50. Furthermore, thermal conductivity decreased by 34% (0.3608 W/mK to 0.2376 W/mK) when sand was fully replaced with CR granules, showcasing improved thermal insulation. Statistical analysis using ANOVA confirmed that the crumb rubber content significantly influences the mechanical and thermal properties of FRPFC, with higher CR content (80% and 100%) leading to superior performance. These findings highlight FRPFC's potential as an environmentally sustainable and thermally efficient construction material, contributing to enhanced mechanical properties compared to conventional foamed polypropylene fibre concrete.

An improved hybrid process for natural rubber foam manufacture combining the Dunlop/Blowing/Talalay methods

ABSTRACTMelamine‐modified zinc phytate (PA‐MA‐Zn) was successfully synthesized by the direct precipitation method, and then silicone rubber foams (SiFs) with PA‐MA‐Zn were prepared. The test results showed that PA‐MA‐Zn could considerably enhance the flame retardancy and smoke suppression properties of SiFs. Specifically, SiFs with 5 wt% PA‐MA‐Zn achieved a limiting oxygen index value of 29.4%, and the total heat release and total smoke production were reduced by 37.35% and 70.72%, respectively, compared with pure SiFs. This might be attributed to the better flue gas adsorption capacity of the expanded carbon layer formed by the synergistic effect of MA and PA in SiFs. Furthermore, the catalytic effect of phytate and zinc substantially improved the strength of the carbon layer, which could effectively block the transfer of heat and oxygen on the surface of SiFs.

Silicone rubber foam is recognized for its heat resistance and lightweight properties, making it suitable for a variety of applications. However, the relationship between the formulation, crosslinking network structure, rheological properties and foaming behavior is not thoroughly understood. In this work, the contents of crosslinked chains, dangling chains and free chains were characterized by low-field nuclear magnetic resonance (LF-NMR), which revealed the transformation of dangling chains into crosslinked chains with increasing the content of crosslinking agent. Additionally, utilizing chain segment information and rheological results, it was found that the densely crosslinking network structure of silicone rubber results in a storage modulus significantly exceeding its loss modulus. This leads to a smaller cell diameter in silicone rubber foam compared to thermoplastic polymers such as PP and PET, consequently resulting in a lower expansion ratio for silicone rubber. This study also investigated the mechanical properties of samples with different cell morphologies. The findings provide insights into the differences in foaming behavior between silicone rubber and thermoplastic polymers.

Application of irradiated EPDM rubber foam filled by sugarcane bagasse carbons for removing pollutants from wastewater

Supercritical N2-induced lightweight high-strength chloroprene rubber foam with excellent flame-retardant and smoke suppression