Compression Set Research Articles

Thermal oxidative aging behavior and lifetime prediction of fluoroether rubber

Fluoroether rubber's performance offers extensive application potential in harsh conditions. This article investigates the thermal-oxidative aging behavior and life prediction of fluoroether rubber using methods such as Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Differential Scanning Calorimeter (DSC) and Compression Set. Results indicate that with prolonged aging, fluoroether rubber exhibits decreased heat resistance, damaged TAIC crosslink structures, and weakened characteristic peak intensities of main chains and side groups, leading to changes in rubber structure. Throughout the aging process, hardness, physical crosslink density, glass transition temperature, and compressive stress gradually increase, while mechanical properties decline. Using compression set as an indicator, service life at various temperatures was predicted, providing theoretical guidance for improving the reliability of fluoroether rubber seals and expanding their engineering applications.

Study on the effect of halloysite nanotubes on the mechanical properties and swelling resistance of ethylene-propylene diene monomer (EPDM)/nitrile butadiene rubber (NBR) blend nanocomposites

Abstract Research was undertaken to explore the alteration of natural halloysite nanotubes (HNTs) using a blend of resorcinol and hexamethylenetetramine (RH), (γ-aminopropyl) triethoxysilane (APTES), and diethoxydimethyl silane (DMS). This investigation delved into the impact of incorporating various proportions of RH-modified HNTs (RH-HNTs), APTES-modified HNTs (APTES-HNTs), DMS-modified HNTs (DMS-HNTs), and unmodified HNTs into ethylene propylene diene monomer (EPDM) and nitrile butadiene rubber (NBR) for their potential as seal materials. The study assessed key properties such as tensile strength, stress at 100% elongation, elongation at break, compression set, hardness, and swelling and abrasion resistance to gauge the influence of HNT additions. As nanofiller content increased, the crosslinking rate rose, while scorch time and optimum cure time decreased. Findings indicated that incorporating nanofillers at 6 phr compositions notably enhanced composite strength initially, with a subsequent slight reduction. However, rebound resilience diminished with increasing filler content, though composite hardness experienced a slight improvement. Mole percent uptake decreased, particularly at higher filler loadings. Notably, systems containing 6 phr RH-HNTs exhibited a 140% increase in tensile strength. FESEM micrographs depicted a rough fracture surface with well-dispersed nanofillers within EPDM/NBR. Additionally, compression set data illustrated enhanced composite performance under compression, crucial for seal applications.

Lossy Compression of Integer Astronomical Images Preserving Photometric Properties* *This work was supported in part by the Spanish Ministry of Science and Innovation (MICINN) and by the European Regional Development Fund (FEDER), funded by MCIN/AEI/10.13039/501100011033/FEDER, UE, under grant PID2021-125258OB-I00; also by the Catalan Government under grant SGR2021-00643; and also by the “PhotSat” project under the Institute for Space Studies of

Observatories are producing astronomical image data at quickly increasing rates. As a result, the efficiency of the compression methods employed is critical to meet the storage and distribution requirements of both observatories and scientists. This paper presents a novel lossy compression technique that is able to preserve the results of photometry analysis with high fidelity while improving upon the state of the art in terms of compression performance. The proposed compression pipeline combines a flexible bi-region quantization scheme with the lossless, dictionary-based, LPAQ9M encoder. The quantization process allows compression performance and photometric fidelity to be precisely tailored to different scientific requirements. A representative data set of 16-bit integer astronomical images produced by telescopes from all around the world has been employed to empirically assess its compression-fidelity trade-offs, and compare them to those of the de facto standard Fpack compressor. In these experiments, the widespread SExtractor software is employed as the ground truth for photometric analysis. Results indicate that after lossy compression with our proposed method, the decompressed data allows consistent detection of over 99% of all astronomical objects for all tested telescopes, maintaining the highest photometric fidelity (as compared to state of the art lossy techniques). When compared to the best configuration of Fpack (Hcompress lossy using 1 quantization parameter) at similar compression rates, our proposed method provides better photometry precision: 7.15% more objects are detected with magnitude errors below 0.01, and 9.13% more objects with magnitudes below SExtractor’s estimated measurement error. Compared to the best lossless compression results, the proposed pipeline allows us to reduce the compressed data set volume by up to 38.75% and 27.94% while maintaining 90% and 95%, respectively, of the detected objects with magnitude differences lower than 0.01 mag; and up to 18.93% while maintaining 90% of the detected objects with magnitude differences lower than the photometric measure error.

Exploring effects of supplementary cementitious materials on setting time, strength, and microscale properties of mortar

The concept of sustainability has become a crucial concern for safeguarding the planet. The current research has focused on developing affordable and eco-friendly mortar by using industrial wastes. This study explores the use of fly ash (FA) and ground granulated blast furnace slag (GGBFS), byproducts of steelmaking and coal burning, in mortar production. It examines their impacts on the compressive strength and setting times, when utilizing varying proportions of the materials. The study also evaluates water requirements for the workability, thus demonstrating the sustainability of these waste products in construction. The cementitious materials were employed in finely ground form and were replaced with further tertiary mixes including both supplements at 10%, 30%, and 50% of each. The mixtures were allowed to cure for 7, 14, and 28 days by immersion in water. The results showed improvements in the compressive strength of mortar samples incorporating FA and GGBFS at various curing ages. However, the water requirement and workability of mortar samples were altered as a result of utilizing these supplementary cementitious materials (SCMs). These findings will serve as a standard for environmentally responsible mortar using GGBFS and/or FA as SCMs.

Mechanical characterization and structural analysis of elastodontic appliances under intraoral and artificial aging conditions

BackgroundThis study focused on the aging mechanism and degradation of mechanical and structural features of elastodontic appliances (EA) under artificial and intraoral aging to achieve oral myofunctional therapy with particular removable silicone elastomer devices.Materials and methodsEAs artificially aged in saliva with different pH values were investigated through cyclic compression testing along with characterization techniques (Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy), and characterization analysis was also performed on clinically retrieved EAs.ResultsArtificial aging was found to have minimal effect on the structural properties of EAs, and intraorally aged samples showed perceptible micro-morphology. The Mullins index and peak stress decreased (P<0.01), while the compression set increased with prolonged aging time. Samples in alkaline saliva showed the largest Mullins effect (P<0.05).ConclusionsThe aging mechanism of the elastomer was found to be the crosslinking of main chains and scission of side chains. The presence of OH- enhanced the rupture degree of side bonds. The decline in viscoelastic properties was shown to be more severe with longer service durations.Clinical relevanceResearch on how the salivary environment and pH affect the aging characteristics of EAs is vital for guiding clinical applications and future modifications to extend their clinical lifetime.

Effects of BET Surface Area and Silica Hydrophobicity on Natural Rubber Latex Foam Using the Dunlop Process.

To reinforce natural rubber latex foam, fumed silica and precipitated silica are introduced into latex foam prepared using the Dunlop process as fillers. Four types of silica, including Aerosil 200 (hydrophilic fumed silica), Reolosil DM30, Aerosil R972 (hydrophobic fumed silica), and Sipernat 22S (precipitated silica), are investigated. The latex foam with added silica presents better mechanical and physical properties compared with the non-silica foam. The hydrophobic nature of the fumed silica has better dispersion in natural rubber compared to hydrophilic silica. The specific surface area of silica particles (BET) also significantly influences the properties of the latex foam, with larger specific surface areas resulting in better dispersity in the rubber matrix. It was observed that exceeding 2 phr led to difficulties in the foaming process (bulking). Furthermore, higher loading of silica also affected the rubber foam, resulting in an increased shrinkage percentage, hardness, compression set, and crosslink density. The crosslink density increased from 11.0 ± 0.2 mol/cm3 for non-silica rubber to 11.6 ± 0.6 mol/cm3 for Reolosil DM30. Reolosil DM30 also had the highest hardness, with a hardness value of 52.0 ± 2.1 IRHD, compared to 45.0 ± 1.3 IRHD for non-silica foam rubber and 48 ± 2.4 IRHD for hydrophilic fumed silica Aerosil 200. Hydrophobic fumed silica also had the highest ability to return to its original shape, with a recovery percentage of 88.0% ± 3.5% compared to the other fumed silica. Overall, hydrophobic fumed silica had better results than hydrophilic silica in both fumed and precipitated silica.

Influence of Wastes and Synthesis Conditions on the Compressive Strength, Setting Time and Gels of Waste-Based Geopolymers.

In civil engineering, both rapid setting and delayed setting are needed for various application scenarios. In order to regulate the setting time of concrete, the iron ore tailings-blast furnace slag (IOT-BFS)-based geopolymers were synthesized with a broad range of setting time and a high compressive strength in this study. The factors of iron ore tailings content, alkali content, liquid-solid ratio, and modulus of alkali activator on setting time of the geopolymers were analyzed. The setting times of geopolymers are tested by a manual Vicat apparatus, and their microstructure is characterized by scanning electron microscopy (SEM), as well as that the hydration heat flow is characterized by an isothermal heat conduction calorimeter (TAM Air). It is found that setting time of the geopolymers was mostly affected by the modulus of alkaline activators due to the reasons that changes in modulus lead to the accelerated hydration reaction, formation of low-polymeric silicates, generation of gels, and encapsulation of precursor particles caused by high viscosity. Adjusting the modulus of the alkaline activator to 0.8 can control the initial setting time of the geopolymers to around 3 min. When the modulus ranges from 1-1.8, the initial setting time fell in the range of 15-45 min. For an alkaline activator modulus of 2, the initial setting time increased to 108 min. This study gives a clue for the preparation of geopolymers with adjustable setting times for multi-scenario applications in construction materials.

Impact of ageing factors on the performance of novel viscoelastic polyurethane foams utilized as seals in respiratory protective devices

This study explores the impact of ageing factors – i.e., perspiration, disinfection procedures and ultraviolet radiation – on the structural and performance characteristics of novel viscoelastic polyurethane foams specifically developed for use in seals for respiratory protective devices (RPDs). The investigation includes an analysis of resilience, compression set and recovery time to ascertain the influence of the chosen factors on the foam’s mechanical properties. Furthermore, an in-depth exploration of the foams’ thermal properties and chemical structure was carried out using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), respectively. The influence of the ageing factors on the foams’ microstructure was scrutinized via scanning electron microscopy (SEM), supplemented by assessments of colour change and contact angle alterations. The experimental results were contextualized within the existing literature, with particular attention to the desired attributes of RPD seals composed of these newly engineered materials. Recommendations for use were then formulated.

Geophysical characterization of the bedrock and regolith in the Pranmati basin critical zone, Uttarakhand Himalaya

The young active Himalayan mountain is characterized by steep slope and dissected topography in overall compressive tectonic setting. The mountain belt has primarily coarse textured soil with poor water holding capacity and is highly prone to erosion. The erosion not only affects many ecosystems located at downstream but also has detrimental effects on the critical zone (CZ). In the present study, we have carried out DC electrical resistivity study in the Pranmati catchment of the Alaknanda basin, a Himalayan critical zone in the Lesser Himalaya, to understand the pattern of soil erosion, transportation and deposition by characterizing the bedrock architecture and hence regolith thickness. A total of 6 electrical resistivity tomogram (ERT) profiles were laid at two locations in the catchment, one in a plain grassland and another at a crop field located on a hill slope of >25o. The study area in the Baijnath klippe, consists of quartz-biotite gneisses with layers of quartz mica-schist enclosed by thrust faults. Electrical resistivity sections of the downslope grassland site show a sharp resistivity contrast between the southwest and northeast transects suggesting south-eastern increase in dip of the bedrock, oblique to the north-east facing surface topography and a thick regolith (> 10 m). The resistivity sections of the site located on the hillslope yield a very thin layer of regolith (< 2 m) indicating significant soil erosion and high weathering of the bedrock. We propose that the water–rock interaction within the porous regolith facilitated by subsurface water circulation might be a potential source for the thick regolith. The observations substantiate existing hypotheses for the evolution and development of deep critical zones. From the results, it has been hypothesized that the bedrock architecture and water channel paths within the CZ together control the regolith thickness.

Impact of Aging on Tensile Properties of EPDM, TPV, and eco-TPV: A Comparative Study Across Diverse Environments

Abstract This study examines the effects of aging on the tensile characteristics of Ethylene Propylene Diene Monomer (EPDM), Thermoplastic Vulcanizates (TPV), and Eco-friendly Thermoplastic Vulcanizates (Eco TPV) in different conditions. The samples underwent thermal aging at a temperature of 90°C and were immersed in sulfuric acid solutions with varying concentrations (1M, 0.1M, and 0.001M) for a duration of 1000 hours at the same temperature. The findings revealed that EPDM demonstrated the maximum tensile strength and a moderate level of elongation and breakage. Furthermore, it retained substantial mechanical integrity after undergoing aging, thereby establishing it as the most resilient material among those evaluated. The thermoplastic vulcanizate (TPV) exhibited intermediate tensile strength and elongation, but experienced significant deterioration when exposed to very acidic environments while Eco TPV had lower tensile strength but good chemical stability. The stress-strain behavior and compression set tests emphasized EPDM’s exceptional durability and ability to recover elastically. The pH measurements of the immersion solutions indicated an elevation caused by the release of alkaline chemicals from the rubber components, especially in the 1M solution.

Unraveling the interactive effects of Na2O/Al2O3, SiO2/Al2O3 and calcium on the properties of geopolymers from circulating fluidized bed fly ashes

Circulating fluidized bed fly ash (CFB-FA), generated as solid waste from the thermal power plants with different contents of calcium. The reuse of CFB-FA for construction materials is the most promising method for the large-scale transformation of waste to resource. This paper examines the ratio effects of Na2O/Al2O3 and SiO2/Al2O3 on geopolymers from low-calcium fly ash (CFB-FA1) and high-calcium fly ash (CFB-FA2) by using a mixture of Na2SiO3 and NaOH as the alkali activator. The detailed mechanistic study with XRD, FTIR, SEM, and MAS NMR is also conducted for the roles of silicon, aluminum, and calcium in the reaction process and their mutual interaction mechanism, along with the regulating mechanism for the compressive strength and setting time of geopolymers. The results indicate that the increased ratios of Na2O/Al2O3 and SiO2/Al2O3 are favorable for the reactions and reduce the setting time of CFB-FA1 and CFB-FA2 based geopolymer. In CFB-FA1, the higher silicon and aluminum content is conducive to their dissolution by regulating the Na2O/Al2O3 ratio, forming N-A-S-H and resulting in the increased strength. A small amount of calcium mainly exists in the form of CaSO4, which completely participates in the reaction. In CFB-FA2, the silicon and aluminum contents are relatively low, while the calcium content is high. The compressive strength is achieved by regulating the SiO2/Al2O3 ratio to increase the dissolution of silicon and aluminum, allowing CaSO4 and CaO to react and form C-A-S-H and ettringite, with CaCO3 as unreactive. The low calcium is favorable for the long-term strength, but the high calcium acts oppositely, primarily attribute to the decomposition of ettringite, a critical component for maintaining the compressive strength of CFB-FA2 based geopolymers.

The Influence of Oil and Thermal Aging on the Sealing Characteristics of NBR Seals.

Nitrile Butadiene Rubber (NBR) is widely used as a sealing material due to its excellent mechanical properties and good oil resistance. However, when using NBR material, the seal structure is unable to avoid the negative effects of rubber aging. Hence, the influence of oil and thermal aging on the characteristics of NBR seals was studied by coupling the mechanical behavioral changes with the tribological behavioral changes of NBR in oil and the thermal environment. For this paper, aging testing and compression testing of NBR were carried out. Additionally, friction testing between friction pairs under different aging times was carried out. The surface morphology of the NBR working surface under different aging conditions was also observed. Finally, coefficients of different test conditions were introduced into the finite element model of NBR seals. It can be seen from the results that the elastic modulus increased with the increase in aging time in the thermal oxidative aging testing. The elastic modulus after 7 days of thermal oxidative aging increased by 135.45% compared to the unaged case, and the elastic modulus after 7 days of oil aging increased by 15.03% compared to the unaged case. The compression set rate of NBR increased significantly with the increase in aging time and temperature. The coefficient of friction (COF) between friction pairs increased first and then decreased with the increase in aging time. The maximum contact pressure decreased by 2.43% between the shaft and sealing ring and decreased by 4.01% between the O-ring and groove. The proportion of the effective sealing area decreased by 3.05% between the shaft and sealing ring and decreased by 6.11% between the O-ring and groove. Furthermore, the sealing characteristics between the O-ring and groove were better than those between the shaft and sealing ring.

RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS THE INNER PART OF ROD SEALS

ABSTRACT The viscoelastic properties of rubber polymer–based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion and the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and the acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications were varied to demonstrate the different degree of contraction resulting from three-dimensional printing. An ACN content of 34% and an average molar mass of 2.47·105 g·mol−1 with a dispersity index of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as the inner part of rod seals.

Lifetime prediction of EPDM sealing materials with thermal aging under constant compression

Abstract EPDM (Ethylene Propylene Diene Monomer) is an important engineering sealing material. Thermal aging leads to a decline in its service life. In this study, the static sealing lifetime of EPDM sealing materials is investigated by thermal aging experiments under constant compression. Based on the variation pattern of compression set over aging time at different aging temperatures (80 °C, 100 °C, and 120 °C), a lifetime prediction model for EPDM sealing materials is derived using chemical reaction kinetics and the Arrhenius equation. The model is compared with the experimental results. The results show that the prediction model is highly reliable. The theoretical life of EPDM after thermal aging at 25 °C is 30.6 years, 53.1 years, and 89.1 years, respectively, when the compression set is 40%, 45%, and 50 %.

Comprehensive evaluation of microstructure and mechanical performance of sustainable ambient-cured alkali-activated composites

Cement is one of the building materials that is most frequently utilized in the construction field. However, the cement industry contributes significantly to the production of greenhouse gases. Therefore, many works have focused on improving sustainable construction materials that could contribute to decreasing greenhouse gas emissions. This study aimed to design a sustainable geopolymer mortar (GPM) made of fly ash (FA) and ground-granulated blast furnace slag (GGBS), which would be suitable for repairing damaged concrete structures. The work focused on investigating the effect of GGBS percentage, alkaline activator ratio, and superplasticizer dosage on the compressive strength, setting time, and workability of an ambient-cured GPM. The results of this research indicated that the compressive strength of GPM improved with the increase in GGBS percentage until a certain limit. However, the workability and setting time deteriorated with the increase in GGBS percentage. Increasing the alkaline activator ratio contributed to improving the compressive strength, workability, and setting time of GPM up to specific levels, but then they started to reduce. Superplasticizer dosage contributed to enhancing the compressive strength, workability, and setting time of GPM. This study found that the optimum FA/GGBS-based GPM that may be used in repair applications contains 50% GGBS, 50% FA, and 5% superplasticizer. The silica sand/binder ratio and alkaline activator ratio were 2.75 and 1.0, respectively. The compressive strength at 1 day, setting time, and workability of the optimum mix were about 12.70 MPa, 20 min, and 138.75 mm, respectively. The XRF, XRD, TGA, and SEM analyses were useful tools used to interpret the effects of the alkaline activator ratio on the fresh and mechanical properties of GPM.

Prediction models for seal performance of a space seal considering atomic oxygen effects

A low impact docking system with advanced capabilities has been developing for future spacecrafts, and its main interface docking seal (MIDS) is both a critical component and a research topic of interest. It is a typical design for the MIDS that adopts the elastomer seal-on-seal structure made of silicone rubbers, and the atomic oxygen (AO) in space had been found to take great effects on the sealing performance by previous experimental studies, especially for the seal leak, seal adhesion, and compression set. Exposure to AO may cause obvious changes on the sealing surface of the MIDS, and some characteristic parameters of morphology are proposed to characterize the changes in this study, including of the porosity, roughness and radius of curvature. Both the leakage model and the adhesion model of the MIDS are further developed to predict the sealing performance considering AO effects, which had been confirmed by the application experiments. The experimental data are in good agreement with the calculation data. The effects of AO on the sealing performance are simulated and analyzed by the proposed prediction models. The results are beneficial to the developments of the MIDS and other space seals.

Lossless hyperspectral image compression by combining the spectral decorrelation techniques with transform coding methods

ABSTRACT This study explores the utilization of Binary Embedded Zero Tree Wavelet Algorithms (BEZW) to compress hyperspectral images. The primary goal is to enhance the representation of spectral data while minimizing storage and transmission requirements. The BEZW algorithm employs wavelet transformations to leverage both spectral and spatial redundancies found in hyperspectral data cubes. Its embedded zero tree structure ensures efficient encoding of small coefficients with minimal overhead. The study evaluates the performance of the BEZW method utilizing various hyper-spectral datasets and compression settings, comparing it to other compression techniques. The results illustrate that the BEZW algorithm offers a promising approach to hyperspectral image compression, achieving competitive compression ratios while preserving spectral accuracy. This makes it a valuable option for applications where efficient hyperspectral data storage and transmission are crucial. The research contributes to the field of hyperspectral imaging by introducing an effective compression method that enhances data accessibility, simplifying the utilization of hyperspectral data in resource-constrained environments.

Correlations between the Aging Behavior and Finite Element Method Simulation of Three Silicone Elastomers.

The material parameters required to describe material behavior can change with the age of the components due to chemical and physical aging processes. The finite element method (FEM) is a tool for designing components for later use. The aim of this study is to correlate the change in the mechanical properties of silicone elastomers from standard tests over a longer period of time with the parameters of the Mooney-Rivlin model. To date, there are no publications on the development of the Mooney-Rivlin parameters of silicone elastomers over a storage period. For this purpose, the Shore A hardness, rebound elasticity, compression set and tensile properties were investigated over an aging period of approx. 200 days on two liquid silicone rubbers (LSRs) and one room-temperature-vulcanizing (RTV) silicone rubber. Depending on the silicone elastomer used, different trends in the characteristic values can be observed over the storage period. In general, increases in the Shore A hardness, rebound resilience and stress at a 100% strain with a decrease in the compression set can be determined. In addition to standard tensile tests, the material's multiaxial behavior under tension was probed, and it was found that the similarly stress at a 100% strain increased. Finite element simulations verified the standard tensile test and corresponding Mooney-Rivlin model parameters. These parameters from the uniaxial tensile were validated in the multiaxial behavior, and the model's accuracy in representing material properties and the influence of aging on the FEM simulation were affirmed.

Modification of polymethylmethacrylate bone cement with halloysite clay nanotubes

BackgroundPolymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn’t provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics.ObjectivesThe purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers.MethodsPMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05).ResultsThe findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups.ConclusionThe novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

Fabrication of Soft Biodegradable Foam with Improved Shrinkage Resistance and Thermal Stability.

The soft PBAT foam shows good flexibility, high elasticity, degradable nature, and it can be used as an environmental-friendly candidate for EVA and PU foams. Unfortunately, there are few reports on the application of PBAT as a soft foam. In this study, PBAT foam was fabricated by a pressure quenching method using CO2 as the blowing agent. A significant volume shrinkage of about 81% occurred, where the initial PBAT foam had an extremely high expansion ratio, of about 31 times. A 5-10 wt% PBS with high crystallinity was blended, and N2 with low gas solubility and diffusivity was mixed, with the aim of resisting foam shrinkage and preparing PBAT with a high final expansion ratio of 14.7 times. The possible mechanism behind this phenomenon was established, and the increased matrix modulus and decreased pressure difference within and outside the cell structure were the main reasons for the shrinkage resistance. The properties of PBAT and PBAT/PBS foams with a density of 0.1 g/cm3 were measured, based on the requirements for shoe applications. The 5-10 wt% PBS loading presented advantages in reducing thermal shrinkage at 75 °C/40 min, without compromising the hardness, elasticity, and the compression set, which ensures that PBAT/PBS foams have good prospects for use as soft foams.