Swelling Of Material Research Articles

Moisture ageing effects on the mechanical performance of eco-friendly sandwich panels made of aluminium skins, bamboo ring core and bio-based adhesives

Recent research has been focused on developing high-performance sandwich structures using renewable resources. The adoption of bamboo rings as a core material and bio-based adhesives has emerged as a promising sustainable design solution for panel construction. It is therefore critical to conduct accelerated ageing tests on these materials to evaluate the impact of environmental humidity on their degradation and durability. This study assessed the effects of moisture ageing on the physic-mechanical properties of eco-friendly sandwich panels and their constituents (aluminium skins, bamboo ring core and castor oil bio-adhesive). Mechanical evaluations of sandwich panels with compacted and spaced bamboo ring cores were performed under varying humidity conditions. Bamboo rings exhibited variable bulk density due to swelling and loss of organic material over time. They also demonstrated increased compressive properties after 2 years of natural ageing but reduced performance after 30 days at 100% relative humidity. The mechanical properties of the bio-based polymer were enhanced through water-ageing exposure. Sandwich panels constructed with compacted bamboo ring cores exhibited higher bending properties than those with spaced ring core architecture, with the latter showing failures characterised by a wrinkling effect on both skins followed by debonding.

EFFECT OF DRYING SPEED ON THE DESATURATION OF SWELLING ROCK

The paper presents the results of a numerical study of the influence of drying speed and hydraulic conductivity of swelling rock on the development of the desaturated zone. Swelling rock refers to natural material in which montmorillonite is the predominant type of mineral. Previous tests have unequivocally shown that a fully saturated swelling rock with a high swelling potential will not swell when wetted with water of the same chemical composition as the pore water. The swelling potential can be activated only after the desaturation of the swelling rock. The geohazard of swelling of such materials represents a very serious problem. The behavior of swelling rock is modeled as a combined hydraulic-mechanical process that includes vertical one-dimensional water flow in saturated and unsaturated conditions, with a change in the volume due to a change in the water content. As part of previously conducted laboratory research, a model of swelling was developed, which realistically represents the behavior of swelling material at the level of laboratory samples. With the developed model, it is possible to forecast the changes in moisture content that will occur during drying at the depth of the desaturated zone. Numerical simulations have clearly shown that the depth of the desaturated zone depends on the drying speed, that is, that significant depths of the desaturated zones can only be realized at low and long-term drying speeds. With the increase in the hydraulic conductivity of the swelling rock, the depth of the desaturated zone increases, and the time required for the development of such a zone increases to the same extent.

A coarse-grained approach to modeling gas transport in swelling porous media

In many engineering applications, understanding gas adsorption and its induced swelling in nanoporous materials is crucial. In this study, we propose a novel coarse-grained molecular dynamics (CGMD) model with gas-gas, solid-solid, and gas-solid interactions explicitly controlled to achieve the coupling between gas transport and solid deformation at the microscale. The CGMD model has the capability to recover solid and gas properties, including density, Young's modulus of the solid, and viscosity of the gas to generate a broad range of swelling ratios relevant to nanostructures by using the innovative bead-spring chain networks. A comparison is made between gas transport through deformable and non-deformable nanochannels of varying sizes (35.4–123.9 nm), which is also compared with the macroscopic Hagen-Poiseuille equation. The proposed model has been further tested in a simplified nanoporous medium composed of four randomly distributed spherical solids. The Kozeny-Carman equation can generally describe the relationship between permeability and porosity, but small deviations are observed in the case of swelling porous media. Our results justify the effect of swelling on reducing gas permeability and provide a new approach to modeling gas transport in swelling porous media at the microscale within the framework of CGMD, with potential applications spanning nanofluidics, energy storage technologies, and environmental nanotechnology.

Experimental Study of the Swelling and Rheological Properties of a High-Strength Preformed Particle Gel Lost Circulation Material

Summary Preformed particulate gel (PPG) has emerged as a widely utilized lost circulation material in deep oil and gas drilling operations. The objective of our study was to devise a high-strength preformed particle gel (HSPPG) specifically designed to address drilling fluid loss in high-temperature fractured formations. To achieve this, a comprehensive set of laboratory experiments was conducted to assess the swelling and rheological properties of HSPPG under various conditions, and these investigations aimed to provide deeper insights into the pressure-bearing mechanism exhibited by HSPPG. The synthesis of HSPPG involved the copolymerization of acrylamide (AM) and N-hydroxymethacrylamide (NMA) molecular chains, catalyzed by organic peroxides, to form the primary network. Additionally, to enhance its temperature resistance, urea-formaldehyde (UF) resin, known for its superior thermal stability, was incorporated into the secondary network. This unique combination of primary and secondary networks imparted remarkable thermal endurance and structural stability to the resulting HSPPG. The swelling and rheological experiments revealed that HSPPG, with a particle size of 1000 µm, exhibited an equilibrium swelling rate (SR) value of 30.55 and a storage modulus (G’) of 1050 Pa at 120℃. These findings attested to its excellent temperature resistance and structural stability. Furthermore, when subjected to a sodium chloride solution at a temperature of 120℃ and a concentration of 25.0%, HSPPG achieved equilibrium swelling with an SR value of 24.93 and a G’ of approximately 7000 Pa. This significant increase in structural strength was attributed to charge shielding within the highly concentrated brine environment. In the plugging experiments, a wedge-shaped slit with an inlet of 3 mm and an outlet of 1 mm was successfully blocked using a concentration of 4% of HSPPG with a particle size of 1000 μm. The blocking strength achieved was 8.06 MPa. The results of these experiments, as well as the observed filling and plugging state of HSPPG in steel fractured cores, indicated that HSPPG possesses the properties of water absorption, swelling, and extrusion filling. These attributes facilitate the effective formation of a dense blocking layer within the fracture space, exhibiting excellent pressure-bearing capacity. In conclusion, the HSPPG developed in this study represents an advanced swellable granular plugging agent with excellent swelling capacity and structural strength at high temperatures. It offers an ideal solution to mitigate drilling fluid loss from fractured formations under high-temperature and high-salinity conditions.

Dynamic response of He bubbles in Fe9Cr1.5W0.4Si F/M steel under in-situ stepwise nanocompression

Inert-gas bubbles in metals have attracted great attention due to their fundamental role in swelling and degradation of materials. Studies of bubble behavior can provide valuable insights for developing advanced materials. Although extensive research has been conducted on bubble behavior under irradiation or thermal conditions, there is still a lack of investigation under both stress and temperature conditions. In this work, in-situ uniaxial compression tests were performed on helium-bubbled Fe9Cr1.5W0.4Si F/M steel using transmission electron microscopy at 923 K to investigate the responses of bubbles with increasing strain. The results revealed a series of bubble responses, including frequent annihilation, occasional coalescence, and a "forced" coalescence achieved by connecting multiple bubbles under high strain. These responses relied on bubble migration and interaction, influenced by the factors such as the He-V ratio, relative bubble position, and sink effect. Furthermore, the migration mechanism of compressed bubbles at high temperatures is considered to be a combination of surface diffusion induced by thermal gradient and volume diffusion induced by stress gradient. These two mechanisms are expected to compete with each other in different temperature and stress. These findings offer crucial experimental insights into the behavior of bubbles in solids exposed to stress and thermal conditions.

The role of stacking fault tetrahedra on void swelling in irradiated copper

A long-standing and critical issue in the field of irradiated structural materials is that void swelling is significantly higher in face-centered cubic-structured (fcc) materials (1% dpa−1) as compared to that of body-centered cubic-structured (bcc) materials (0.2% dpa−1). Despite extensive research in this area, the underlying mechanism of the difference in swelling resistance between these two types of materials is not yet fully understood. Here, by combining atomistic simulations and STEM imaging, we find stacking fault tetrahedra (SFTs) are the primary cause of the high swelling rate in pure fcc copper. We reveal that SFTs in fcc copper are not neutral sinks, different from the conventional knowledge. On the contrary, they are highly biased compared to other types of sinks because of the SFT-point defect interaction mechanism. SFTs show strong absorption of mobile self-interstitial atoms (SIAs) from the faces and vertices, and weak absorption of mobile vacancies from the edges. We compare the predicted swelling rates with experimental findings under varying conditions, demonstrating the distinct contributions of each type of sink. These findings will contribute to understanding the swelling of irradiated structural materials, which may facilitate the design of materials with high swelling resistance.

Changes of Temperature and Moisture Distribution over Time by Thermo-Hydro-Chemical (T-H-C)-Coupled Analysis in Buffer Material Focusing on Montmorillonite Content

Bentonite is used as a buffer material in engineered barriers for the geological disposal of high-level radioactive waste. The buffer material will be made of bentonite, a natural clay, mixed with silica sand. The buffer material is affected by decay heat from high-level radioactive waste, infiltration of groundwater, and swelling of the buffer material. The analysis of these factors requires coupled analysis of heat transfer, moisture transfer, and groundwater chemistry. The purpose of this study is to develop a model to evaluate bentonite types and silica sand content in a unified manner for thermo-hydro-chemical (T-H-C)-coupled analysis in buffer materials. We focused on the content of the clay mineral montmorillonite, which is the main component of bentonite, and developed a model to derive the moisture diffusion coefficient of liquid water and water vapor based on Philip and de Vries, and Kozeny–Carman. The evolutions of the temperature and moisture distribution in the buffer material were analyzed, and the validity of each distribution was confirmed by comparison with the measured data obtained from an in situ experiment at 350 m in depth at the Horonobe Underground Research Center, Hokkaido, Japan.

Nested loops explain low irradiation-induced swelling rate

In the quest of radiation and oxidation-resistant materials for the fuel claddings of nuclear power stations, chromium (Cr) emerges as a good candidate. It shows a significantly lower irradiation-induced swelling rate of nearly an order magnitude lower than other body-centered cubic materials, such as W and Fe. This phenomenon indicates that there is an unsuspected aspect, beyond the crystal structure that affects the swelling of materials. To understand it, the structure and distribution of irradiation-induced dislocation loops in Cr were investigated after ion irradiation at 550 ℃ from 0.1 to 15 dpa. It appears that after irradiation Cr exhibits nested loops, either vacancy-type loops called ‘trough’ or interstitial-type loops called ‘island’, which are composed of a large dislocation loop containing multiple small and coplanar loops with inverse nature. Our results indicate that the nested trough and island dislocation loops stem from the 1D migration of dislocation loops. This loop formation mechanism is an alternative mechanism of recombination and annihilation of point defects, which in turn can explain the low swelling rate in Cr. This mechanism provides a new insight into the irradiation-induced swelling rate of metals.

Controlling the roll-to-helix transformation in electron-beam-patterned gel-based micro-ribbons.

Helix formation has been of ongoing interest because of its role in both natural and synthetic materials systems. It has been extensively studied in gel-based ribbons where swelling anisotropies drive out-of-plane bending. In contrast to approaches based on photolithography or mechanical bilayer construction, we use electron-beam patterning to create microscale ribbons at ∼1-100 μm length scales in pure homopolymer precursor films of poly(acrylic acid) (PAA). The radiation chemistry creates a ribbon comprising a crosslinked hydrophobic top layer and a hydrophilic gel bottom layer with a continuous through-thickness variation in between. The classic roll-to-helix transition occurs as the ribbon aspect ratio increases. Notably, we see examples of single-loop rolls, multi-loop rolls, minimal-pitch helices, plus a transition structure comprising both helical and roll-like features. Finite-element modelling recapitulates key aspects of these conformations. Increasing the pH from below to above the PAA pKa increases the out-of-plane bending to the extent that the ribbons plastically deform and nonminimal-pitch helices form across a wide range of aspect ratios and irradiation conditions. The nonminimal pitch is caused by an in-plane anisotropy associated with the plastic deformation. We mimic this anisotropy by patterning ribbons comprising micro-tiles separated by gaps which receive electron exposure due to proximity effects. We observe a transition from roll to helix to tube with increasing gap angle. The chirality is completely determined by the gap orientation (±θ). However, in contrast to established approaches to generate in-plane anisotropies based on mechanical properties, finite-element modelling indicates that anisotropic through-thickness swelling of the gap material plays a dominant role in helix formation and suggests that this micro-composite ribbon behaves like a rigid origami metamaterial where deformation at the creases (the gaps) between structural elements controls the shape shifting.

Effect of the sonic shock wave on void evolution in materials under irradiation

Understanding the void-cascade interaction is of great importance for clarifying the irradiation damage as a major challenge in nuclear industry, since it typically causes void annihilation or shrinkage, which greatly affects the swelling of irradiated materials. But the current understanding of it is extremely limited due to the neglect of the sonic shock wave. Herein, we take γ-U as the representative model due to the emergence of a violent sonic shock wave there. Molecular dynamics simulations are performed to explore the underlying mechanism of the sonic shock wave interacting with voids. It is firstly revealed that the sonic shock wave is essentially focusons along <111> crystal orientation family, attributed to the highest energy transfer efficiency along <111> in γ-U. These focusons can cause void annihilation or shrinkage via sliding, while thermal spikes only cause annihilation by covering voids. Combining these two factors, we propose a model to qualitatively epitomize the void-cascade interaction, in which the influence scope exhibits an intriguing anisotropic feature, overturning a long-accepted view that the void-cascade interaction is isotropic. This model is further generalized to other nuclear materials owing to the similar mechanism of the sonic shock wave. Moreover, we find distinct size effect of voids on void-cascade interaction. Thermal spikes hardly affect voids that are too large to be covered, while the sonic shock wave also causes visible shrinkage in large voids. The present work proves that the sonic shock wave has a non-negligible effect on void evolution, improving the fundamental understanding of void-cascade interaction in irradiated materials.

Quantitative method to predict the energetics of helium-nanocavities interactions in metal systems based on electrophobic interaction

Energetics of helium-nanocavities interactions are crucial for unveiling underlying mechanisms of nanocavity evolution in nuclear materials. Nevertheless, it becomes intractable and even not feasible to obtain these energetics via atomic simulations with increasing nanocavity size and increasing helium content in nanocavities. Herein, a universal scaling law of helium-induced interaction energies in nanocavities in metal systems is proposed based on electrophobic interaction of helium. Based on this scaling law and ab-initio calculations, a predictive method for binding energies of helium and displacement defects to nanocavities of arbitrary sizes and with different helium/vacancy ratios is established for BCC iron as a representative and validated by atomic simulations. This predictive method reveals that the critical helium/vacancy ratio for helium-enhanced vacancy binding to nanocavities increases with increasing nanocavity size, and the helium/vacancy ratio giving the highest stability of nanocavities is about 1.6. The Ostwald ripening of nanocavities is delayed by helium to higher temperatures due to reduced vacancy de-trapping rates from nanocavities. The proposed scaling law can be generalized to many metal systems studied in the nuclear materials community. Being readily coupled into mesoscale models of irradiation damages, this predictive method facilitates clarifying helium role in cavity swelling of metallic nuclear materials.

Modeling, validation, and analysis of swelling behaviors of lithium-ion batteries

The swelling of lithium-ion batteries (LIBs) is one of the responsible reasons to cause capacity degradation and safety problems. Quantification of the swelling force and the corresponding strain is a critical problem in exploring the complex electro-mechanical behaviors in batteries. Though in the current open literature, a few models are available to describe the swelling of the component materials in a battery. A physics-based detailed model linking the component material scale to the cell scale is still lacking. Herein, we develop a fully detailed three-dimensional swelling mechanical model considering the actual structure of the battery. After rigorous validation by the experiment, we leverage the model to investigate a complicated coupled boundary, i.e., plate-constrained swelling. The swelling force and uneven stress distribution of each component are analyzed among various influential factors. The results provide fundamental insights into the application of LIB.

Antiproliferative Imidazo-Pyrazole-Based Hydrogel: A Promising Approach for the Development of New Treatments for PLX-Resistant Melanoma.

Aiming at developing a dermal formulation against melanoma, the synthesized imidazo-pyrazoles 2-phenyl-2,3-dihydro-1H-imidazo[1,2-b]pyrazole-7-carboxylic acid (3-methoxy-4-phenoxy-benzylidene)-hydrazide (4G) and 2-phenyl-2,3-dihydro-1H-imidazo[1,2-b]pyrazole-7-carboxylic acid (4-benzyloxy-3-methoxy-benzylidene)-hydrazide (4I) were screened on patient-isolated melanoma cells (MEOV NT) and on Vemurafenib (PLX4032)-resistant (MEOV PLX-R) ones. Since 4I on MEOV PLX-R cells was 1.4-fold more effective than PLX, a hydrogel formulation containing 4I (R4HG-4I) was prepared in parallel with an empty R4-based hydrogel (R4HG) using a synthesized antibacterial resin (R4) as gelling agent. Thanks to its high hydrophilicity, porosity (85%), and excellent swelling capability (552%), R4 allowed to achieve R4HG and R4HG-4I with high equilibrium degree of swelling (EDS) and equilibrium water content (EWC). Chemometric-assisted ATR-FTIR analyses confirmed the chemical structure of swollen and fully dried (R4HG-D and R4HG-4I-D) hydrogels. The morphology of R4HG-D and R4HG-4I-D was examined by optical microscopy and SEM, while UV-vis analyses were carried out to obtain the drug loading (DL%) and the encapsulation efficiency (EE%) of R4HG-4I. Potentiometric titrations were performed to determine the equivalents of NH3+ in both R4HG and R4HG-4I. The swelling and water release profiles of both materials and related kinetics were assessed by equilibrium swelling rate and water loss studies, respectively, while their biodegradability over time was assessed by in vitro degradation experiments determining their mass loss. Rheological experiments established that both R4HG and R4HG-4I are shear-thinning Bingham pseudoplastic fluids with low yield stress, thus assuring easy spreadability in a future topical application. Release studies evidenced a sustained and quantitative release of 4I governed mainly by diffusion. Upon favorable results from further experiments in a more realistic 3D model of melanoma, R4HG-4I could represent a starting point to develop new topical therapeutic options to adjuvate the treatments of melanoma cells also when resistant to currently available drugs.

The Effect of Drying Variables on the Microwave–Vacuum-Drying Characteristics of Mulberries (Morus alba L.): Experiments and Multivariate Models

It is easy to cause increases in temperature and the gasification of water in materials, facilitated via supercharging and the generation of instantaneous strong pressure under the collaborative action of a microwave and a vacuum, thus facilitating the internal cell swelling of materials, changes in fibre structures, and the formation of loose and uniform microstructures. In this experiment, mulberries were dehydrated using microwave–vacuum drying technology. The drying characteristics were disclosed by using crispness as the evaluation index and multiple drying parameters (e.g., products’ surface temperature, microwave power, chamber vacuum level and drying height) as the control variables. The optimised Two-term model can predict the dehydration process of mulberries under multiple drying variables, as determined through the experimental data. The optimal drying variables were determined according to the crispness of the dried mulberries. The optimal puffing quality of mulberries could be gained under a product surface temperature = 50 °C, microwave power = 5.45 W/g, a chamber vacuum level = 0.08 MPa and a drying height = 0 cm. The diffusion coefficient of the available water of the mulberries during the microwave–vacuum drying process ranges from 4.98 × 10−8 to 3.81 × 10−7, and the activation energy for drying is 183.923 KJ/mol.

The channeling effect of symmetrical tilt grain boundaries on helium bubbles in tungsten

Helium atoms can migrate easily and aggregate at various crystal defects, such as grain boundaries, which promote the nucleation and growth of helium bubbles, ultimately causing severe radiation damage to nuclear materials. Structure characteristics of grain boundaries with low-angle symmetrical tilt of the [100] axle and their channeling effects on helium bubbles in tungsten were investigated by molecular dynamics simulations. The triaxial variation curves of the helium bubble size in each grain boundary model and the relationship of the helium diffusion coefficient of each grain boundary to their intrinsic crystal structures are analyzed. The results indicate that the helium bubbles grow into one-dimensional nanochannels at the selected grain boundaries, and there is a significant difference in the maximum number of helium bubbles these grain boundaries can accommodate before forming one-dimensional nanochannels. Furthermore, the existence of helium nanochannels along the 〈100〉 edge dislocation line in the low-angle symmetrical tilt grain boundaries is well verified by molecular dynamics simulation of the helium bubble growth and helium diffusion equations at the 〈100〉 edge dislocation line. This suggests that releasing helium outside of the tungsten matrix through the nanochannel structures of low-angle symmetrical tilt grain boundaries may be a potential strategy to address the root causes of bubble nucleation and swelling of tungsten material.

A system of automated control of thermal vacuum impregnation and swelling of sealing elastomers

When determining the swelling of polymeric materials in aggressive environments by standard test methods, significant measurement errors occur which entails the necessity of improving laboratory methods and diagnostic tools to solve research problems by automation of existing testing processes and minimization or complete elimination of the subjective components of measurement errors. We present an automated control system (ACS) for the process of swelling of sealing elastomers used in the construction of containers, tanks and units for storage, transportation, operation and pumping of liquids of various origins and properties. Methods of hardware and algorithmic implementation of the developed automated system for studying and testing impregnation and swelling of sealing polymers are shown on the example of filling MBS elastomer samples with a standard working fluid. The results obtained can be used to reduce the time of impregnation and swelling of sealing elastomers due to the proposed filling method and the developed integrated automatic control system for the filling process.

Microstructure of Bio-Based Building Materials: New Insights into the Hysteresis Phenomenon and Its Consequences

Considering the current energy environment, both efficient and environmentally friendly solutions have to be developed for building construction. Bio-based building materials offer new perspectives through their insulating and natural humidity regulation capacities. Nevertheless, these materials are as complex as they are promising, and grey areas still remain regarding their behavior. Their water sorption and desorption curves recorded in experimental work demonstrate a hysteresis phenomenon and, although plausible hypotheses have been formulated in the literature, there is currently no consensus on its causes. Furthermore, it is important to emphasize that no reference considers the hydrophilic nature of the resource. Yet, this is a specificity of raw material coming from the plant world. In this context, this paper explores the microstructure and chemical composition of plant aggregates to propose a new explanation for the hysteresis. It is based on recent work demonstrating the existence of differentiated hydrogen bonds between the water sorption and desorption phase in cellulose. Obviously, hysteresis also has an origin at the molecular scale. Lastly, the hypothesis put forward here is supported by the swelling of bio-based materials that has been observed at high relative humidity, and this study aims to identify a link between the mechanics of bio-based materials and their hygroscopic behavior. A swelling/shrinking is macroscopically observed. Combining the fields of chemistry, physics, and civil engineering allowed us to demonstrate that it comes from a molecular-scale hydromechanical coupling. This is a major breakthrough in the understanding of bio-based composites.

Swelling compensation of engineered vasculature fabricated by additive manufacturing and sacrifice-based technique using thermoresponsive hydrogel.

Engineered vasculature is widely employed to maintain the cell viability within in vitro tissues. A variety of fabrication techniques for engineered vasculature have been explored, with combination of additive manufacturing with a sacrifice-based technique being the most common approach. However, the size deformation of vasculature caused by the swelling of sacrificial materials remains unaddressed. In this study, Pluronic F-127 (PF-127), the most widely used sacrificial material, was employed to study the deformation of the vasculature. Then, a thermoresponsive hydrogel comprising poly(N-isopropylacrylamide) (PNIPAM) and gelatin methacrylate (GelMA) was used to induce volume shrinkage at 37°C to compensate for the deformation of vasculature caused by the swelling of a three-dimensional (3D)-printed sacrificial template, and to generate vasculature of a smaller size than that after deformation. Our results showed that the vasculature diameter increased after the sacrificial template was removed, whereas it decreased to the designed diameter after the volume shrinkage. Human umbilical vein endothelial cells (HUVECs) formed an endothelial monolayer in the engineered vasculature. Osteosarcoma cells (OCs) were loaded into a hierarchical vasculature within the thermoresponsive hydrogel to investigate the interaction between HUVECs and OCs. New blood vessel infiltration was observed within the lumen of the engineered vasculature after in vivo subcutaneous implantation for 4 weeks. In addition, engineered vasculature was implanted in a rat ischemia model to further study the function of engineered vasculature for blood vessel infiltration. This study presents a small method aiming to accurately create engineered vasculature by additive manufacturing and a sacrificebased technique.

Positive Control(s) in Polyurethane Condom-Lubricant Compatibility Testing

Abstract Despite the proliferation of over-the-counter (OTC) personal lubricants (PLs) in the last two decades, to date, no known positive control has been identified to assess the compatibility of these PLs with polyurethane (PU) condoms. In the absence of suitable positive controls, PU condom compatibility with OTC PLs is assessed using a method built for testing compatibility of latex condoms with PLs. Herein, we attempt to identify a safe-to-handle positive control(s) for determining PU condom-lubricant compatibility. At room temperature (RmT), swelling of and induced stress in PU condom sample coupons were studied at various strain rates after discrete applications of a few ingredients common in commercial PLs. Additionally, stress reduction at a constant stretch was measured at 37°C. At low strain rates, changes in the induced stress and stress-to-strain ratio were detectable because of ingredients, e.g., hydroxy-terminated poly(dimethyl siloxane) of viscosity 25 cSt that caused substantial swelling of the condom materials at RmT, indicating prospective positive controls. At 37 °C, the percent stress reduction in PU samples under constant stretch was significant, with a few PL ingredients that did not significantly swell the PU material at RmT. Ingredients that enable significant stress reduction can serve as positive controls in PU condom-lubricant compatibility testing using the tensile method, provided the strain rate is comparable to the rate of condom-lubricant interaction, as evidenced by swelling study. At RmT, absence of swelling and insignificant changes in tensile properties at high strain rates do not guarantee the absence of interactions. Instead of testing mineral oil on latex condoms, manufacturers may now use a PU condom-specific positive control, when testing compatibility of PU condoms with OTC PLs.

Dynamic evolution of polyhedral bubbles in Fe9Cr1.5W0.4Si F/M steel under 30keV H2+& He+ synergetic irradiation

Large polygon bubbles can cause significant swelling and embrittlement in irradiated materials. Understanding their formation and growth process is thus important to alleviate the mechanical property degradation of nuclear materials. Here, based on in-situ 30 keV H2+ and He+ synergetic irradiation in Fe9Cr1.5W0.4Si ferritic/martensitic steels, polygonal bubble evolution was investigated at grain boundaries, matrix-precipitate interfaces and matrices. Two threshold sizes were first found for bubble growth in the matrix. One determined the shape between sphere and rectangle, while the other determined whether growth was continuous or reached a saturation size. Large polygonal bubbles formed at interfaces due to abnormal growth rates and coalescence between bubbles. Finally, the bubble growth at sinks and matrices was explained using a bubble growth rate model.