Peel Force Research Articles

Influence of Stretchiness and Application Times of Tapes on Peel Forces and the Correlation between Peel Forces on Test Plate and in vivo Human Skin

Influence of Stretchiness and Application Times of Tapes on Peel Forces and the Correlation between Peel Forces on Test Plate and in vivo Human Skin

Abstract 167: Granulation And Genomic Evaluation Of Easy To Use Novel Negative Pressure Wound Therapy Dressings

Introduction: NPWT with reticulated open cell foam (ROCF) has impacted the practice of healing wounds. New approaches have been contemplated for longer wear dressings. Two novel dressings were evaluated for cellular genomic responses, granulation tissue thickness formation, and average peel force to remove the dressing in a porcine wound healing study. Methods: Eleven domestic swine were used to obtain samples from full-thickness surgical wounds treated with either NPWT ROCF+, NPWT novel dressing 1#, or NPWT novel dressing 2*. Biopsy samples were taken at study termination on either Day 7 or Day 13. Porcine polymerase chain reaction (PCR) wound healing arrays (Qiagen, Valencia, CA) were performed to determine differences in gene expression (>2 fold difference; p<0.05). Histopathology evaluations and morphometry measurements assessed granulation tissue quality and thickness, respectively. The peel force required to remove the dressings was obtained using a custom test device. Results: Granulation: In the day 13 group, there was a significant difference (p<0.0441) in granulation tissue thickness between ROCF + interfacial layer (ROCF + IFL) (5.33 mm ± 0.14) as compared to CPUF (7.43 mm ± 0.33). No significant difference were seen between ROCF + IFL (5.33 mm ± 0.14) and GM (5.80 mm ± 0.22). Moreover, each treatment group (ROCF + IFL, CPUF, and GM) demonstrated a significant increase in granulation tissue deposition over time (p<0.04). Genomics: The novel GM dressing at Day 13, relative to Day 7, demonstrated greater upregulation in cell binding and catalytic activity which included Matrix metallopeptidase 1 (6.58), Matrix metallopeptidase 3 (8.83) and Decorin (2.15). These are important epithelial markers and known for collagen binding. Novel CPUF dressing at Day 13, as compared at Day 7, demonstrated similar results. There was in increase in MMP1 (10.30) and MMP3 (13.46), both of which are important in keratinocyte migration and endothelial cell activity. There was an increase in Catenin (2.29), which may be responsible for the inhibition signal that causes cells to stop dividing once the epithelial sheet is complete. In addition, cell adhesion genes (Integrins: ITGA2, ITGB3 and ITGB6) were all up regulated (2.01, 2.62, 6.90 respectively). Peel Force: Regardless of group or timepoint, ROCF required significantly greater average force for removal. A dressing change at day 4 did not statistically affect the amount of peel force required to remove ROCF for the groups with a day 7 end of in-life/termination. The use of the interfacial layer with GF brought the force required for removal as low as the other novel dressings. Conclusions: This preclinical study illustrates that the tested novel dressings induced more granulation tissue formation with less peel force, and interesting genomic responses than the controls. Following 13 days of treatment in a porcine model, the novel NPWT dressings have been shown to increase genes involved in epithelization while increasing granulation tissue and decreasing dressing removal force, which might lead to better wound healing outcomes. KCI Licensing, San Antonio, TX +V.A.C.® Therapy with GRANUFOAM™ #GM dressing (NPWT novel dressing 1) *CPUF dressing (NPWT novel dressing 2)

Segmental Variations in the Peel Characteristics of the Porcine Thoracic Aorta.

Aortic dissection occurs predominantly in the thoracic aorta and the mechanisms for the initiation and propagation of the tear in aortic dissection are not well understood. We study the tearing characteristics of the porcine thoracic aorta using a peeling test and we estimate the peeling energy per unit area in the ascending and the descending segments. The stretch and the peel force per unit width undergone by the peeled halves of a rectangular specimen are measured. We find that there can be significant variation in the stretch within the specimen and the stretch between the markers in the specimen varies with the dynamics of peeling. We found that in our experiment the stretch achieved in the peeled halves was such that it was in the range of the stretch at which the stress-stretch curve for the uniaxial experiment starts deviating from linearity. Higher peeling energy per unit area is required in the ascending aorta compared to the descending aorta. Longitudinal specimens required higher peeling energy per unit area when compared to the circumferential specimens.

In vitro evaluation of skin adhesives during perspiration

To bridge the gap between current in vitro and in vivo testing, we present the use of a perspiration simulator to evaluate the performance of skin adhesives during sweating. The perspiration simulator mimics human skin in key aspects such as roughness, water contact angle, sweat pore size, sweat pore density, and can be operated at different perspiration rates. In contrast to in vivo testing, a well-defined experimental setup with minimal variation is therefore successfully achieved. To demonstrate the capabilities of the reported perspiration simulator, two model adhesives with different water absorption capabilities are assessed. The peel forces as a function of time are thereby measured during perspiration of a 0.154 M NaCl solution. The peel force decreases immediately when the perspiration rate exceeds the water uptake as determined by an immersion test. However, when the water absorption capabilities are sufficiently high, a delay in the decrease in peel force is observed. Through the use of a fluorescent dye, we can further correlate the loss of adhesion with a spreading of liquid at the skin-adhesive interface.

Bonding Strength of FRP-Metal Hybrids

The lightweight credo “the right material in the right place” raises an interesting concern once different materials are meant to provide a watertight bond. Therefore, we investigate the bonding behavior of metals with Fiber-Reinforced-Plastic (FRP) materials. In order to optimize the bond, the major influencing factors and their interactions are studied.In order to identify the above interactions, FRP-metal hybrid specimens were investigated with regard to peel forces and shear strengths. During manufacturing the influencing factors such as sheet metal and FRP type, surface treatments, and bonding processes were varied.Considering the peel force, a thermoset plastic matrix adhesively bonded to steel provided the best results, along with the use of a novel surface etching method by Kobelco. The latter yielded the highest shear strengths within this investigation. No bond could be obtained applying thermoset plastic matrices for in-operandi connections.Using adhesives or surface treatments introduced additional production costs. Hence, in-operandi bonding would be a favorable option, however, one requiring further research. Compared to the material costs, the additional production costs could prove to be insignificant once the bonding process has been properly robustified and automated.

Glycerol-crosslinked PEDOT:PSS as bifunctional binder for Si anodes: Improved interfacial compatibility and conductivity

Developing conductive polymer binders is a new way to enhance the electric connectivity and mechanical contact of Si based anode material. While the linear structure of commercial PEDOT:PSS cannot effectively alleviate the volume expansion of Si. Herein, glycerol was introduced as a cross-linker to PEDOT:PSS binder for Si anodes, which can further improve the interfacial compatibility between silicon and PEDOT:PSS. After crosslinking, the peel force increased 2 times. As a result, the Si nanoparticles anode with the glycerol-crosslinked binder exhibited a high reversible capacity of 1951.5 mAh g−1 after 200 cycles at 0.5 A g−1 and superior rate capability (804 mAh g−1 at a high current of 8.0 A g−1) for the inherent superior conductivity of PEDOT:PSS.

Determination of the interface properties in an elastic film/substrate system

Based on the assumption of constant-stress (Dugdale) interface bonding, a theoretical model is established in order to characterize the entire peeling response of an elastic film from a rigid substrate. The relationship between the peeling force and the peeling displacement and the relationship between the cohesive zone length and the peeling displacement at different peeling stages are analyzed. Closed-form solutions of the maximum peeling force and the maximum length of cohesive zone are further derived theoretically. It is found that both the maximum peeling force and the maximum length of cohesive zone depend on the interface strength, interface toughness and bending stiffness of the film. Combined with the classical Kendall's model, the cohesive zone length in the steady-state peeling stage is further given. A new method to simultaneously determine the interface strength and interface toughness is proposed, as long as the maximum peeling force, steady-state peeling force and film's bending stiffness are obtained from peeling tests. The results of this paper should be very helpful for interface performance prediction and interface design of film/substrate systems.

Unveiling the Failure Mechanism of Electrical Interconnection in Thermal-Aged PV Modules

The electrical interconnection is the most decisive current transportation pathway in photovoltaic (PV) modules. However, thermal stresses, induced by temperature variation, can reduce the mechanical properties of the electrical interconnection and lead to the performance degradation of PV modules. The present study aims to investigate the influence of thermal stress on the failure mechanism of the electrical interconnection. The mechanical integrity of current transmission layers and interfaces is measured by peeling tests and evolution of defects and failure process is observed by in-situ electroluminescence (EL) imaging and scanning electron microscopy (SEM). Under repeated thermal stress, the defects initiated at the end of the soldering track and, then, expanded to the adjacent cell regions. Initially, the silver-glass interface was more vulnerable to separation under the action of the peeling force. However, the disruption between the silver busbar and silicon wafer increased with increasing thermal cycling. In addition, a possible failure mechanism has been proposed for electrical interconnection by SEM observation and defect analysis. Lastly, we have demonstrated that the reliability of the interconnection structure can be improved by increasing the edge distance of the PV modules or using an anti-overpressure device.

Predicting adhesive sealing life of Li-ion pouch cell using a fusion method considering time-varying dependence

ABSTRACT The adhesive sealing structure plays an important role in high-reliability long-life service of Li-ion pouch cells. The inner gas pressure increases inevitably owing to a diversity of chemical and thermal reactions during charging/discharging cycles of Li-ion pouch cells. It accelerates the degradation of adhesion properties, leading to the sealing failure and batteries’ being scrapped in advance. Therefore, an accurate sealing life prediction method is crucial for durable Li-ion batteries. Since existing physics-based methods cannot describe the time-varying dependence between the gas pressure and adhesion property variable (i.e. maximum peeling force) well, whereas pure data-driven methods have difficulties in determining failure thresholds, this paper proposes a fusion method for predicting the sealing life. Considering the irreversibility of the sealing degradation, the Gamma stochastic processes are used to describe the dispersivity and monotonous variation of gas pressure and maximum peeling force, and the time-varying dependence between them is modelled by time-varying copula functions. Then, two empirical physical equations are employed to determine the relationship between the gas pressure and the sealing stress, as well as the relationship between the peeling force and the adhesive strength. Finally, the sealing life prediction is obtained based on the stress-strength interference theory.

Preparation of polyacrylic latex with external crosslinking and its effect on the pressure-sensitive properties

ABSTRACT A series of external crosslinked polyacrylic latexes with the same particle sizes were synthesized at a solid content of 50 wt% via semi-continuous emulsion polymerization with diacetone acrylamide (DAAM) and adipic acid dihydrazide (ADH) as the external-crosslinking agents, named as poly(BA-co-MAA-co-DAAM)-ADH, PBMD-A. The effects of crosslinking agent content on the emulsion polymerization, molecular structure, and molecular motion were investigated by means of gravimetric analysis, dynamic light scattering (DLS) and dynamic mechanical analysis (DMA). The results showed that the crosslinking agent content had no significant effect on the polymerization process. The overall conversions of monomers with different crosslinking agent contents were high, and the latex particles grew in a spherical shape without generating secondary particles during the growth process. With the increase of the crosslinking agent content, the gel content, glass transition temperature, and storage modulus of the PBMD-A increased. The adhesive properties, including tack force, peel force and shear resistance of the PBMD-A products were evaluated using the FINAT test methods. This paper provided a facile and ecological method to rapidly increase rapidly the shear resistance and kept other adhesion performance for polyacrylic pressure-sensitive adhesives (PSAs) with addition of a small amount of external-crosslinking agent.

Peeling of metal foil from a compliant substrate

ABSTRACT Large displacement peel was studied for cases where a compliant substrate leads to a large value of the root rotation. An existing simplified beam model to calculate the peel fracture energy was modified to allow for a kinematic hardening beam model of the foil. The steady-state peel force and the root rotation were used as input data to the resulting analytical beam model. Test results from the literature were analysed. A more elaborate finite element model was also studied, using cohesive elements for the interface layer between the foil and the substrate. The cohesive zone parameters used were the fracture energy, the cohesive strength and a shape parameter. An optimization scheme for the cohesive zone parameters was developed and optimized against experimental steady-state peel force and root rotation. The optimization scheme was effective to characterize the cohesive parameters. The method yields similar values of fracture energy for the two peel angles, with the one for being slightly higher than for . The difference in fracture energies for different peel angles suggests that the fracture energy can be mode dependent.

Quantitative peel test for thin films/layers based on a coupled parametric and statistical study

The adhesion strength of thin films is critical to the durability of micro and nanofabricated devices. However, current testing methods are imprecise and do not produce quantitative results necessary for design specifications. The most common testing methods involve the manual application and removal of unspecified tape. This overcome many of the challenges of connecting to thin films to test their adhesion properties but different tapes, variation in manual application, and poorly controlled removal of tape can result in wide variation in resultant forces. Furthermore, the most common tests result in a qualitative ranking of film survival, not a measurement with scientific units. This paper presents a study into application and peeling parameters that can cause variation in the peeling force generated by tapes. The results of this study were then used to design a test methodology that would control the key parameters and produced repeatable quantitative measurements. Testing using the resulting method showed significant improvement over more standard methods, producing measured results with reduced variation. The new method was tested on peeling a layer of paint from a PTFE backing and was found to be sensitive enough to register variation in force due to differing peeling mechanisms within a single test.

Development and Identification of Working Parameters for a Lychee Peeling Machine Combining Rollers and a Pressing Belt

This work describes the development, design, and parameter identification of a lychee peeling machine. The working principle of the machine combines two rollers with a pressing belt to separate the peel from the fruits. It was designed and its operational parameters identified on the basis of experimental data on the Thieu lychee, which currently covers about 80% of the plantation area in Vietnam. To this end, the first step was to measure the physical characteristics of the fruits, such as size, shape, and density. Moreover, the coefficient of static friction between lychees and rubber rollers, and the critical peeling force, were identified, with a view to optimizing the operational parameters later on. Results showed that a minimum tangential force of 10.5 N is needed to break the peel and separate it from the pulp. Based on the balanced force principle, various optimal machine parameters such as roller rotation speed, roller diameter, roller length, gap size between the two rollers, belt velocity, and minimum pressure of the belt were calibrated. In addition, spiral grooves were created on the roller surface to facilitate the motion of the fruits. The optimal results were roller size 900 × 100 mm (length × diameter), rotation speed 159 RPM, gap size between rollers 4 mm, belt size 850 × 60 mm (length × width), belt pressure 13.5 N, and belt velocity 140 mm/s. Using the design and operational parameters mentioned above, the machine was able to perform regularly at a throughput of 100 kg/h, as demanded by the current market. Moreover, it would be easily feasible to combine multiple pairs of rollers and pressing belts in order to increase throughput. The methodology for the design of this peeling machine and identification of working parameters with respect to experimental data could be applied in many other post-harvesting configurations.

Nanofiber membranes as biomimetic and mechanically stable surface coatings.

Elastomers have been extensively exploited to study cell physiology in fields such as mechanobiology, however, their intrinsic high hydrophobicity renders their surfaces incompatible for prolonged cell adhesion and proliferation. Electrospun fiber networks on the other side provide a promising environment for enhanced cell adhesion and growth due to their architecture closely mimicking the structure of the extracellular matrix present within tissues of the human body. Here, we explored the stable integration of electrospun fibers onto the surfaces of elastomeric materials to promote cytocompatibility of these composites. Elastomers based on room temperature vulcanizing silicone (RTV), polydimethylsiloxane (PDMS) as well as functionalized PDMS-based materials were chosen as wafer substrates for attachment of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDFhfp) fibers, a well-known antithrombotic polymer. Electrospinning the fibers onto uncured interfaces acted as bonding agents on the wafers, enabling penetration and formation of a stable bond between the fibers surfaces and the elastomers after curing the interface. Dimensional analysis revealed a relationship between peeling force, intrusion depth and the elastic modulus of the wafers. A design parameter Πα was extrapolated to be used as a predictive tool of the peeling force when intrusion depth of PVDFhfp fibers and elastic modulus of the wafers are known. Cultivating fibroblasts on these hybrid membranes showed cell attachment and growth over 7 days regardless of the composition of the substrate, confirming high cytocompatibility for all composite materials. The presented approach opens avenues to establish nanofiber morphologies as a novel, stable surface texturing tool for tissue engineering, cell biology, medical devices and textiles.

Elastic–plastic analysis of the peel test for ductile thin film presenting a saturation of the yield stress

The paper investigates the peel test of an elastic–plastic film on an elastic substrate. The case of a film material presenting a saturation of the yield stress is considered. Based on earlier approaches of the literature, see for instance Kim and Aravas (Int J Solids Struct 24:417–435, 1988), a semi-analytical expression for the work done by bending plasticity is proposed. The validity of the present expression is established based on finite element calculations. It is shown that for the interpretation of the results of peel test at 90$$^{\circ }$$ when the peel force and the curvature are measured, the present approach can provide a precise value of the interface fracture energy.

In-situ formation of indium seed layer for copper metallization of silicon heterojunction solar cells

Low production cost and simplified process are the prerequisites for large-scale commercialization of highly efficient silicon heterojunction (SHJ) solar cells. In this paper, an innovative method of plating process with in-situ seed layer technique is proposed for the metallization of SHJ solar cells. As indicated by the measurements of cyclic voltammetry curves and scanning electron microscopy, electrochemical reduction reaction occurs and results in metal particles randomly distributed on the surface of tungsten doped indium oxide (IWO) layer. Given the measurement of Energy-dispersive X-ray spectroscopy elemental mapping and X-ray photoelectron spectroscopy, the metal particles are indium and are electrochemically reduced from the IWO film. These indium particles can serve as the seed layer facilitating the subsequent copper plating process. In order to prevent copper diffusion and enhance the adhesion, nickel plating and alkaline copper plating was applied. As a result, the maximum peeling force of plated copper busbar reaches 4.23 N. This is higher than that of the screen-printed silver busbar (2.31 N). By adopting the in-situ indium-seed-layer based plating process, a cell efficiency of 22.01% was achieved with significantly improved short circuit current density and fill factor. Taking advantage of the in-situ seed layer technique, the all-solution based plating process is simplified and effective without full area seed layer deposition and subsequent etch back step, showing great potential for the copper metallization of SHJ solar cells with reduced cost.

Effect of size and shape of graphene sheets on nanoscale peeling process by atomic force microscopy

We numerically studied the effect of size and shape of graphene sheets on nanoscale peeling characteristics by atomic force microscopy (AFM). It was clarified that the simulated peeling processes of the graphene sheet connected to the cantilever spring of AFM were classified into typical four types of the peeling force curves. This classification of the peeling process could be clearly understood in the phase diagram plotted as a function of the length and width of the peeled graphene sheet.

Effect of thin-film length on the peeling behavior of film-substrate interfaces.

Compared with the classical Kendall's model to analyze the steady-state peeling behavior of an infinite length film attaching to a rigid substrate, this paper establishes a model of a finite length thin film adhering on a rigid substrate and analyzes the influence of film's initial adhesion length, film stiffness, and initial cantilever length of films on the whole interface peeling behavior. Both theoretical prediction and finite element calculation are carried out. The typical relationship between the peeling force and the separation distance at the loading point is obtained as well as the morphology of deformed films. It is found that the initial adhesion length has a significant effect on the peeling behavior. Differently from the case of infinite thin films, whether the steady-state peeling process can be achieved or not depends on the film's adhesion length. If the film is long enough, the whole peeling process can be divided into an initial peeling stage, a transition stage, a steady-state stage, and an unstable peeling stage. The maximum peeling force of the interface does not necessarily occur in the steady-state stage, which is influenced by the film's initial adhesion length, film stiffness, and initial cantilever length. The results achieved in this paper can not only provide a systematic understanding of peeling behavior of a thin film on a rigid substrate, but also be helpful for the design of high-quality interface and peeling tests in practical applications.

Polyacrylamide hydrogels. II. elastic dissipater

A rubber band is an elastic dissipater. It has narrow hysteresis on load and unload, but dissipates all its elastic energy on snap. We hypothesize that the dissipation of elastic energy can be a potent toughening mechanism. A polyacrylamide hydrogel has narrow hysteresis, but appreciable toughness, providing an ideal candidate to test the hypothesis of elastic dissipater. We peel the polyacrylamide hydrogel of various thicknesses, and record the steady peel forces. A transition thickness exists, below which the steady peel force increases linearly with thickness, and above which the steady peel force is independent of thickness. The transition thickness is comparable to the fractocohesive length, defined by the ratio of toughness over the work of fracture, and is ∼1 mm for the polyacrylamide hydrogel. The linear slope is comparable to the work of fracture. The linear extrapolation of the steady peel force to vanishing thickness defines the peel threshold, and the thickness-independent steady peel force defines the toughness. The former is much below the latter. We interpret these experimental findings in terms of elastic dissipater. A crack not only cuts a layer of polymer chains, but also breaks some polymer chains in a zone of thickness comparable to the fractocohesive length. Even though only a small fraction of the chains in the zone rupture, all the elastic energy stored in this zone dissipates and contributes to toughness. The entire zone acts as an elastic dissipater, not just a layer of individual polymer chains. We discuss the importance of the elastic dissipater in creating materials of high toughness, high threshold, and low hysteresis.

Chemomechanics of transfer printing of thin films in a liquid environment

The liquid-assisted transfer printing is emerging as a competitive manufacturing technique in the delivery and assembly of thin film-layered functional materials and structures. In essence, this technique is underpinned by the detachment of thin films under a synergistic effect of external mechanical loading and interior chemical reaction at interfaces in a liquid environment. Here, we have developed a comprehensive chemomechanics theory for the transfer printing of thin films from as-fabricated SiO2/Si wafer substrate in a liquid water environment. The kinetic chemical reaction at the interface of liquid molecules and interfacial solid bonds is incorporated into the interface energy release rate of thin film detachment, and a rate dependent interfacial debonding process is obtained. We further couple it with mechanical deformation of thin films by taking into account various peeling conditions including peeling rate, peeling angle and thin film thickness to theoretically predicate the steady-state peeling force. Besides, we implement this chemomechanics theory into a finite element model with all atomic information informed and present a reactive atomistic-continuum multiscale model to simulate the detachment of thin films at the continuum scale. In parallel, we have conducted the peeling experiments of three different separation layers on wafer substrates in both dry air and water conditions. Quantitative comparisons among theoretical predictions, simulation results, and experimental measurements are performed and good agreement is obtained. The competition between interfacial delamination and mechanical deformation of thin films during peeling is also analyzed, and a theoretical phase diagram is given to provide an immediate guidance for transfer printing of silicon nanomembranes in the fabrication of functional structures and electronic devices. In addition, the capillary force due to surface wettability of materials is discussed and compared with chemical reaction-induced driving force for transfer printing on a wide range of thin film/substrate systems. The chemomechanics theory and reactive atomistic-continuum simulation model established are expected to lay a foundation for quantitative understanding and descriptions of transfer printing of thin films in a liquid environment.