Tearing Energy Research Articles

Influence of Deformation Speed on the Tearing Energy of Carbon Black-Filled EPDM Rubber

Influence of Deformation Speed on the Tearing Energy of Carbon Black-Filled EPDM Rubber

Investigating the impact of manufacturing conditions on crack growth rate in nitrile butadiene rubber for enhanced service life – Part 02: Crosslink density via multi-stage swelling analysis

The importance of the state of cure of elastomer components with regard to fatigue behavior and thus also durability was already discussed in more detail in Part 01 of the paper. It was shown that crosslinking time and temperature have an enormous influence on the crack growth behavior in nitrile butadiene rubber (NBR). In the course of this, a fourfold deceleration in crack growth was observed with a 20 K increase in manufacturing temperature. To confirm this trend, test specimens were produced at 180 °C. Crack growth was found to be 40 times slower, especially in high tearing energy ranges, compared to 150 °C. To analyze the observed behavior in more detail, cylindrical samples were taken from the plain strain test specimens (used for the crack growth measurements), and multi-stage swelling was performed with them. This allowed a detailed analysis of the degree of cure and the sulfur chain composition. It was found that the crosslink density decreases with increasing manufacturing temperature due to decomposition and the proportion of polysulfidic crosslinks decreases with increasing heating time due to desulfurization. Furthermore, a correlation between the results found by means of the rubber process analyzer (RPA) and the swelling results could be established looking at the maximum transmitted torque during the isothermal crosslinking phase.

Molecular Chain Rearrangement-Induced In Situ Formation of Nanofibers for Improving the Strength and Toughness of Hydrogels.

Although poly(vinyl alcohol) (PVA) hydrogel has high elasticity and is suitable for cartilage tissue engineering, it is difficult to have both high strength and toughness. In this study, a simple and universal strategy is proposed to prepare strong and tough PVA hydrogels by in situ forming nanofibers on the original network structure induced by a molecular chain rearrangement. Quenching-tempering alteratively in ethanol and water several times is carried out to strengthen PVA hydrogels (PVA-Etn hydrogels) due to the advantages of noncovalent bonds in adjustability and reversibility. The results show that, after three quenching-tempering cycles, PVA-Et3 hydrogel with water content up to 79 wt % shows comprehensive improved mechanical properties. The compression modulus, tensile modulus, fracture strength, tensile strain, and tear energy of the PVA-Et3 hydrogel are 270, 250, 260, 130, and 180% of the initial PVA hydrogel, respectively. The improved mechanical properties of the PVA-Et3 hydrogel are attributed to the strong cross-linked PVA chains and hydrogen bond-reinforced nanofibers. This study not only provides a simple and efficient solution for the preparation of strong and tough polymer scaffolds in tissue engineering but also provides new insights for understanding the mechanism of improving the mechanical properties of polymer hydrogels by adjusting the molecular structure.

Breathable, Adhesive, and Biomimetic Skin-Like Super Tattoo.

Electronic tattoo, capable of imperceivably acquiring bio-electrical signals from the body, is broadly applied in healthcare and human-machine interface. Tattoo substrate, the foundation of electronic tattoo, is expected to be mechanically mimetic to skin, adhesive, and breathable, and yet remains highly challenging to achieve. Herein, the study mimics human skin and design a breathable, adhesive, and mechanically skin-like super tattoo substrate based on an ultra-thin film (≈2µm). Similar to skin, super tattoo demonstrates strain-adaptive stiffening properties with high tear energy (5.4 kJ·m-2) and toughness (1.3 MJ·m-3). Superior to skin, it exhibits high adhesion, ionic conductivity, and permeability. A variety of conductive electrodes can be processed on it, showing the universality toward an ideal platform for electronic tattoo with stable and low contact impedance. Super tattoo-based electrodes can imperceivably and accurately monitor weak electromyography (EMG) of swallowing on the junction, providing effective guidance for rehabilitation training of dysphagia.

Humidity‐adaptive, mechanically robust, and recyclable bioplastic films amplified by nanoconfined assembly

AbstractPoly(vinyl alcohol) (PVA) is biodegradable, recyclable, and has high tensile strength. Therefore, it is ideal for the development of environment‐friendly sustainable bioplastics. However, at elevated humidity, the mechanical properties of PVA bioplastic films undergo degradation owing to their intrinsic hydrophilic and hygroscopic nature, hindering their applications. This study proposes a nanoconfined assembly strategy to produce humidity‐adaptive, mechanically robust, and recyclable bioplastic film. The strong hydrogen bonds between PVA and cellulose nanofibrils inhibit the penetration of water molecules into the film to promote humidity resistance. Further, the robust coordination interactions between bentonite nanoplates, PVA, and cellulose nanofibrils restrict the slip of polymer chains during deformation, leading to enhanced mechanical properties. Benefiting from the nanoconfined assembly architecture in aggregated composites, the resulting reinforced PVA film simultaneously exhibits strength, stiffness, toughness, fracture energy, and tearing energy of 55.9 MPa, 1,275.6 MPa, 162.9 MJ m−3, 630.9 kJ m−2, and 465.0 kJ m−2, respectively. Moreover, the film maintains a strength of approximately 48.7 MPa even at 80% relative humidity for 180 days. This efficient design strategy applies to diverse scales and structured cellulose biomacromolecules. Moreover, it facilitates the application of recyclable high‐performance bioplastic films to settings that require high humidity tolerance.

Unlocking the potential of lignin: Towards a sustainable solution for tire rubber compound reinforcement

This study tackles the persistent challenge of producing highly reinforced lignin-rubber composites, emphasizing the transformation of agro-industrial residues into value-added products. To address this challenge, we introduce a novel approach termed “in-situ surface modification utilizing a thermo-chemo-mechanical approach” which incorporates the utilization of biomass-derived kraft lignin and a thermally stable organofunctional surface modifier, specifically (3-aminopropyl) triethoxysilane. The resulting material exhibits unprecedented tensile strength (∼15 MPa) along with ∼300 % elongation at break, while typical gum rubber offers 1–2 MPa tensile strength. Additionally, for the other tensile properties like 100 %, and 200 % tensile modulus, the improvement is 7-fold (∼5.6 MPa) and 10-fold (∼11.3 MPa), respectively. Furthermore, this composite presents a higher degree of reinforcement than a passenger car radial (PCR) tire model compound (tensile strength ∼14.5 MPa, 100 % tensile modulus ∼2.2 MPa, and 200 % tensile modulus ∼5.6 MPa) comprised of silica and polysulfide-based coupling agent, with exactly a similar loading of filler. The dynamic mechanical and stress relaxation behavior of the composites are critically discussed concerning the dispersion of the lignin in the sSBR/BR rubber matrix. The morphological orientation and involved chemical interaction in the presence of a surface modifier are also studied in detail. Tear fatigue analysis using pure shear specimens indicates superior fracture toughness at a lower tearing energy regime compared to silica-filled PCR tire compounds. Overall, this study showcases the potential of lignin-reinforced elastomers, offering a promising route for sustainable engineering materials and commercial viability.

The tearing energy threshold of crack growth in rubber exposed to ozone: an experimental–numerical approach

The tearing energy threshold of crack growth in rubber exposed to ozone: an experimental–numerical approach

The role of cavitation in the toughening of elastomer nanocomposites reinforced with graphene nanoplatelets

The toughening of different types of elastomers through the incorporation of graphene nanoplatelets (GNPs) has been investigated. Both the tear strength and tearing energy are increased significantly through a combination of mechanisms such as debonding, pull-out and cavitation. The processes that occur ahead of a tear/crack tip in natural rubber filled with GNPs have been monitored in situ using synchrotron-based nanoscale X-ray computed tomography. The GNP particles are found to debond and form voids that grow under stress leading to considerable energy absorption. The mechanisms of cavitation and void growth are analysed theoretically and it is shown that voids need to be larger than ∼1 μm in size to grow in the triaxial tensile stress field ahead of the tear/crack tip. The high level of cavitation and void growth found for the elastomers filled with micron-sized GNP particles is suggested to be the reason why these nanocomposites have a high tear resistance.

Mode III Tear Resistance of Bombyx mori Silk Cocoons.

This paper concerns the tear properties and behavior of Bombyx mori (B. Mori) silk cocoons. The tear resistance of cocoon layers is found to increase progressively from the innermost layer to the outermost layer. Importantly, the increase in tear strength correlates with increased porosity, which itself affects fiber mobility. We propose a microstructural mechanism for tear failure, which begins with fiber stretching and sliding, leading to fiber piling, and eventuating in fiber fracture. The direction of fracture is then deemed to be a function of the orientation of piled fibers, which is influenced by the presence of junctions where fibers cross at different angles and which may then act as nucleating sites for fiber piling. The interfaces between cocoon wall layers in B. mori cocoon walls account for 38% of the total wall tear strength. When comparing the tear energies and densities of B. mori cocoon walls against other materials, we find that the B. mori cocoon walls exhibit a balanced trade-off between tear resistance and lightweightness.

Self-heating and fatigue crack growth behavior of reinforced NR/BR nanocomposites with different blending ratio

Fatigue crack growth and dissipative self-heating due to viscoelasticity are crucial properties of rubber materials under dynamic service conditions. Systematic evaluation of the thermo-mechanical coupled fatigue properties with suitable lab testing methods could contribute to the development of long-lasting and robust elastomer materials. In this work, on the one hand, the hysteresis energy density, thermal conductivity, and surface temperature rise, which are closely related to the self-heating generation rate, heat transfer rate and heat build-up of the carbon black reinforced seven different natural rubber (NR) and polybutadiene rubber (BR) blends were measured. A thermo-mechanical coupling simulation method was used to reproduce the experimental observation. On the other hand, the fatigue threshold (T0), critical tearing energy (Tc), and fatigue crack growth rate (FCGR) under different tearing energy were investigated by using the advanced rubber fatigue instruments. The Lake-Lindley model was utilized to describe the rubber fatigue responses from the intrinsic strength to the ultimate strength. The results show that the dissipative self-heating of NR/BR:30/70 blend is the most obvious one, which could be well explained by the simulation results. The T0 shows an upward trend while Tc shows a downward trend with the increasing blend ratio of BR. The existence of carbon black fillers showed tiny effect on T0 of NR, but significantly enhanced the T0 of BR. The FCGR of reinforced NR/BR nanocomposites have Lake-Lindley law responses that cross over each other. Therefore, which rubber material is superior to others in resisting crack propagation depends on the magnitude of the input tearing energy.

Preterm membranes are mechanically more resistant than term membranes.

To compare the biomechanical properties of fetal preterm membranes (20+0weeks to 30+0weeks) to those of the term (37+0 to 41+0weeks). Amnion and chorion were manually separated and samples were cut to the required geometry. Rectangular samples with (mode 1) and without (uniaxial) a notch, were tested for tearing energy, critical elongation, and tangent stiffness. Suture retention and inter-suture distance testing investigated the effect of suture placement. From the 15 preterm and 10 term placentas studied, no notable differences were observed in uniaxial testing. Mode 1 fracture testing showed a difference in tearing energy between the preterm and term chorion (0.025±0.005 vs. 0.017±0.005J/m-1 ; p=0.027) but not in the amnion (0.030±0.017 vs. 0.029±0.009J/m-1 ; p=0.895). Both preterm amnion and chorion showed a higher critical elongation compared with term (1.229±0.057 vs. 1.166±0.046; p=0.019 and 1.307±0.049 vs. 1.218±0.058; p=0.012). Preterm amnion had a higher suture retention strength than its term counterpart (0.189±0.065 vs. 0.121±0.031N; p=0.023). In inter-suture distance tests, no significant interaction was observed beyond 3mm, but the preterm chorion showed less interaction at 1-2mm distances. Preterm membranes have equivalent or superior tensile properties to term membranes. The chorion appears to contribute to the mechanical integrity of fetal membranes, particularly in preterm stages.

Preparation and improving mechanism of PBAT/PPC-based micro-layer biodegradable mulch film with excellent water resistance and mechanical properties

The utilization and implementation of biodegradable mulch film represent a highly effective approach to address the persistent pollution caused by non-degradable mulch film. However, the poor water resistance and insufficient mechanical properties strongly restrict its practical application. Here the PBAT/PPC-based multilayer biodegradable mulch films including 3-, 17-, 65-, and 257-layer, were manufactured successfully using a self-developed micro-layer blown film technology. The 65-layer film showed significant improvements in its mechanical and barrier properties, outperforming contrast the blend the film by 148 %, 168 %, and 203 % respectively in terms of puncture energy, tear energy, and water vapor barrier. The results obtained from DSC, WAXD, and SAXS analyses demonstrated a significant similarity in the crystalline structure of PBAT in various micro-layer films and the blend contrast film. Consequently, the robust mechanical and water barrier properties can be attributed to the ultrathin micro-layer structure, which dissipated energy during mechanical breakage by promoting substantial plastic deformation and blocked the water by forming a larger and more continuous phase of high barrier PPC. Briefly, the micro-layer mulch films, based on PBAT/PPC and fabricated using the self-developed micro-layer blown film technology, demonstrate exceptional mechanical strength and water resistance properties. Consequently, this research has the potential to garner interest within the biodegradable mulch film sector.

EVA and SEBS-MA copolymers incorporated silicone rubber/SEBS blends: improvement of mechanical and thermal properties

Enhancing the mechanical and thermal properties of Silicone rubber (SR)/SEBS blends using various compatibilizers opens the opportunity for such new blends to meet the market desire. For this purpose, blends with a 1:1 ratio of SR and SEBS are prepared with different amounts of EVA or SEBS-MA copolymers as compatibilizer. Mechanical properties of the blend are enhanced by adding EVA and SEBS-MA. Addition of 6 phr EVA profoundly improves the tensile strength from 7.70 to 10.06 MPa. Thermogravimetric analysis reveals that the presence of compatibilizer can improve the thermal stability of the blend, especially its initial degradation temperature (T5%). T5% of the blend increases from 376 to 390 °C when comprising 6 phr SEBS-MA. Morphology of the blends is investigated using SEM and AFM. Results of the relaxation modulus curves obtained by rubber process analyzer (RPA) demonstrate that the amount of relaxation in the uncured blends is higher than the cured ones. A comparison of the relaxation of the blends indicates that the relaxation modulus of the SEBS-MA compatibilized blends is enhanced more than other blends after curing. Further investigations indicate that the compatibilized blends exhibit higher tear energy and lower compression set.

Enhanced toughness and tear resistance of thin-walled High-Pressure Die-Cast aluminum alloys through Friction stir processing

In this study, we investigate the toughness and resistance to tear of thin-wall high-pressure die-cast (HPDC) aluminum alloys in two different orientations following the implementation of friction stir processing (FSP). The FSP technique was applied to two different HPDC Al-Si alloys: the recyclable-grade, high iron, A380 alloy and the premium-quality, low iron, Aural-5 alloy. Our findings reveal significant tear resistance and strength enhancements for both alloys after FSP modification. Specifically, FSPed A380 alloy requires 126% higher energy to tear, and it has 49% higher tear strength than the HPDC counterpart. Similarly, the tear energy and tear strength of the Aural-5 alloy witness enhancements of 69% and 21%, respectively. These findings emphasize the capability of FSP to improve the toughness of HPDC aluminum alloys, creating new possibilities for preventing cracks in a variety of engineering applications.

Insights on the J‐integral expression of pure shear carbon black filled natural rubber specimen and predicting the crack growth rate using finite element method

AbstractThe J‐integral approach manifests itself in an efficient way to determine the crack growth and failure mechanism of tread and sidewall compounds used in tyres. Therefore, for a pure shear (PS) specimen of carbon black filled natural rubber, the J‐integral formula was vivisected, and the material parameters were defined using the concepts of solid mechanics considering the planar stress conditions. Theoretical calculations, experimental observations, and finite element analysis were executed to calculate the J value for different strain percentages. Different hyperelastic material models were used to understand the hyperelastic behavior of the test compound, but Yeoh model was found to be the best fit with the least error against the experimental test data. The frequency sweep dynamic mechanical analyzer test was done to observe the viscoelastic response of the material. It was observed that the J value decreased with decreasing contour radius and had exhibited stark difference with the global tearing energy values, indicating the effects of stress softening and the dependence of J value on the elastic characteristics of the material. Further, the J value attained from finite element methods for a random strain 22% was used to predict the crack growth rate of the pre‐notched PS specimen.Highlights J‐integral formula for pure shear specimen using solid mechanics approach. J value comparison of theoretical, experimental, and finite element methods. Dependence of J value on the elastic characteristics of the material. Different hyperelastic models compared and Yeoh model chosen for analysis. Prediction of crack growth rate at a random strain percentage.

Reactivity-Guided Depercolation Processes Determine Fracture Behavior in End-Linked Polymer Networks.

The fracture of polymer networks is tied to the molecular behavior of strands within the network, yet the specific molecular-level processes that determine the mechanical limits of a network remain elusive. Here, the question of reactivity-guided fracture is explored in otherwise indistinguishable end-linked networks by tuning the relative composition of strands with two different mechanochemical reactivities. Increasing the substitution of less mechanochemically reactive ("strong") strands into a network comprising more reactive ("weak") strands has a negligible impact on the fracture energy until the strong strand content reaches approximately 45%, at which point the fracture energy sharply increases with strong strand content. This aligns with the measured strong strand percolation threshold of 48 ± 3%, revealing that depercolation, or the loss of a percolated network structure, is a necessary criterion for crack propagation in a polymer network. Coarse-grained fracture simulations agree closely with the tearing energy trend observed experimentally, confirming that weak strand scissions dominate the failure until the strong strands approach percolation. The simulations further show that twice as many strands break in a mixture than in a pure network.

Tissue histology on the correlation between fracture energy and elasticity

PurposePreemptively estimating tissue damage is crucial for a safe surgical procedure. We previously investigated the possibility of estimating the fracture energies of biological tissues based on their elasticities. However, the reason behind the presence of these correlations is poorly understood. In this study, we investigate the effect of a tissue’s histology on the correlation between the fracture energy and elasticity. We hypothesize that two tissues with similar fibrous structure will show a similar correlation between the fracture energy and elasticity.MethodsPorcine duodenum were used for this study. Two tensile tests were performed for each porcine duodenum specimen to determine its elasticity and tearing energy. The correlation between fracture energy and elasticity was then investigated using the results from the mechanical tests. Furthermore, duodenum specimens were fixed in 10% formalin while under tension. Microscopic images were then taken to visualize the fibrous structure within the duodenum tissues under tension.ResultsThe results from the tensile test showed that the fracture energy had an isotropic positive and linear correlation with the elasticity to the negative 0.5th power (R2 = 0.89), which was also previously reported in small intestinal (jejunum) specimens. Furthermore, the tearing patterns of the duodenum were identical to the ones reported in the jejunum. Hematoxylin and eosin staining on tissues fixed under tension showed that the endomysium fibers are involved in providing resistance toward traction.ConclusionThrough mechanical tests, we showed that porcine duodenum tissues also have a correlation between its fracture energy and elasticity. We also discussed that the histological structure of a tissue is an important factor that dictates how the tearing energy of a tissue will correlate to the elasticity. We understood that since the tearing mechanism between the duodenum and jejunum was similar, the correlations between their fracture energies and elasticities were also similar.

Multifunctional hydrogels simultaneously featuring ultrahigh stretchability, remarkable tearing resistance, and reusable fluorescence for information encoding–decoding and smart anticounterfeiting

Fluorescent hydrogels with fluorescent dyes are widely used for anti-counterfeiting encryption. However, developing highly stretchable and remarkable tear-resistant hydrogels with reusable fluorescence for anti-counterfeiting purposes remains challenging. In this study, we fabricated and characterized double network (DN) hydrogels comprising polyvinyl alcohol-borax (PVA-borax) as the first network and poly(methacrylamide-co-polyethylene glycol-co-pyrenylmethyl acrylate) (P(MAM-co-PEGMA-co-PyMA)) as the second network with varying MAM to PEGMA ratios. SEM images showed the hydrogels had 3D porous structures. FT-IR and thermal properties analysis (DSC and TGA) indicated the presence of hydrogen bonds between PVA-borax and P(MAM-co-PEGMA-co-PyMA) without any chemical bonds. The red shift in characteristic absorption bands at 841 and 710 cm−1 further confirmed the presence of π-π* interactions between pyrene moieties. XRD analysis revealed no significant changes in crystalline phase of the hydrogels, which facilitated the formation of a 3D network due to abundant hydrogen bond presence. When the MAM to PEGMA ratio was adjusted to 9:2, the resulting hydrogels exhibited remarkable properties such as ultra-high stretchability (strain over 3300 %), excellent notch-insensitivity, and exceptional tear resistance (tearing energy over 3.25 × 105 J/m2). Importantly, the hydrogel's fluorescence intensity could be reversibly changed by alternatively adding Fe3+ and EDTA-2Na. It could be reused more than 10 times while maintaining a fluorescence intensity of around 80 %, demonstrating its reliability as a versatile hydrogel probe for Fe3+ detection with “ON-OFF-ON” fluorescence behavior. Furthermore, the hydrogels demonstrated exceptional 2D encryption and decryption capabilities, highlighting their potential applications in information storage and data security. To improve the level of anti-counterfeiting, multiple encryption approaches such as QR codes and ASCII binary codes were rationally designed. Overall, this study successfully developed a universal DN hydrogel platform with ultra-high stretchability and remarkable tear resistance, capable of rapid encoding and decoding of complex information for smart anti-counterfeiting.

A novel conductive composite gel based on polyvinyl alcohol/polymerizable deep eutectic solvent with superior tear resistance, tensile properties and recyclability

The polymerizable deep eutectic gel has become one of the essential materials for wearable electronic devices because of its low volatility, excellent ionic conductivity, and electrochemical stability. Finding strategies to improve the strength of gel-like materials was a huge challenge. In this paper, we present for the first time a deep eutectic solvent (DESD) with hydrogen bond acceptors as polymerizable components. We also discover a new strategy for inducing PVA crystallization with it as the core. Using DESD can induce PVA crystallization extremely easily, avoiding the complicated steps of traditional PVA hydrogels which need to cycle freeze–thaw to induce crystallization. The crystalline domain formed by PVA acts as the physical cross-linking site, greatly enhancing the strength (stress up to 4 MPa, strain up to 1558%) and tear resistance (tearing energy up to 12.3 kJ/m2) of eutectic gel. The fully non-covalent cross-linked structure made eutectic gels have excellent self-healing ability (99%) and recycling ability. This strategy provided a new idea for the preparation of high-strength ionic conductive gel. High strength and recyclability gave gel great development space in the engineering application field.

Bioinspired Fast Room-Temperature Self-Healing, Robust, Adhesive, and AIE Fluorescent Waterborne Polyurethane via Hierarchical Hydrogen Bonds and Use as a Strain Sensor.

Developing a new generation of ecofriendly water-based polymeric materials that integrate mechanical robustness, fast room-temperature self-healing, adhesive, and fluorescence remains a formidable challenge. Herein, inspired by titin protein, a series of novel waterborne polyurethanes (WPU-CHZ-NAGA) containing irregular 6-fold and diamide hydrogen bonds are synthesized by introducing carbohydrazide (CHZ) and N,N-bis(2-hydroxyethyl)-3-amino propionyl glycinamide (HO-NAGA-OH) groups. The representative WPU-CHZ2-NAGA3 exhibits outstanding mechanical properties (tensile strength of 36.58 MPa, tearing energy of 81.2 kJ m-2, and toughness of 125.82 MJ m-3) and fast room-temperature self-healing ability with the aid of ethanol (≥90% within 8 h) originated from hierarchical hydrogen bonds. These properties are superior to those of most of the reported room-temperature self-healing polymer materials. Benefiting from plentiful hydrogen bonds, the WPU matrix achieves excellent adhesive properties without heating or adding curing agents. Interestingly, WPU-CHZ2-NAGA3 film emits inherent blue fluorescence due to the aggregation-induced emission effect of tertiary amine groups, and its potential applications in information encryption and anticounterfeiting are further demonstrated. Specially, a eutectic gel strain sensor is also fabricated with WPU-CHZ2-NAGA3 and deep eutectic solvent by a simple physical blending method, which can be used to monitor the movement of human fingers and wrists as well as the change in body temperature. In summary, this work provides new insight into the design and synthesis of multifunctional WPU with fast room-temperature self-healing and high mechanical properties.