Peel Force Research Articles

Mechanical property analysis of a novel peel-speed sensitive flexible fastener

A design of peel-speed sensitive flexible fastener was proposed based on a novel modified polyurethane. Taking the microtrichia of the head-arrester system of lestes barbarous as the bionic prototype, the structure of the micro protuberance was designed as self-mating type with hemispherical caps. Considering the nonlinearities of contact behavior and of the material property, a micromechanical model of typical interlocking element is established. Adopting the explicit dynamics finite element method, the mechanical responses of fastener in peeling are analyzed. The detachment of interlocking element is predicated by taking the total strain energy as an indicator. The influences of peel speed and friction coefficient on the mechanical performances are parametrically studied. The results show that the maximum peel force and the strength increased with respect to the enhancing peel speed because of the intrinsic nonlinearity in the constitutive relation of novel modified polyurethane the investigation adopted. With larger friction coefficient, the maximum peel force, the total strain energy and the corresponding de-adhesion displacements are respectively enhanced.

Surface characterization of polyimide and polyethylene terephthalate membranes toward plasma and UV treatments

This study is to bring an overview on various methods regarding the surface treatment performed on different polymeric membranes in relation to a deference between the treatment mechanism and their chemical structure. Herein, plasma and UV surface treatments (PST and UST) were utilized to treat the surfaces of two commercial membranes, i.e., aromatic polyimide and polyethylene terephthalate for various durations using a discharge electrode and an UV LED curing system, respectively. Based on the effects of PST and UST processes on the surface of these membranes, their surface properties have been characterized to surface morphology and hydrophilicity (or wettability), at same time the changes have probably occurred on their surface during the PST and UST processes. As a result, their hydrophilic behavior was significantly enhanced after conducting these treatment processes based on the investigation of water contact angle. Moreover, Fourier-transform infrared and Raman spectroscopy manifested the changes in the chemical bonds, interactions and orientations of molecules, which confirmed the apparition and insertion of polar functional groups after the surface treatments, and accordingly, their wettability was enhanced significantly. Also, optical microscopy images showed direct impactions on their surface and the evidence of slight surface aging/damage during the treatment processes based on the presentation of the strange streaks on the treated surfaces. In particular, the peel forces exhibited an increase comparing to the initial membranes, which is characteristically for enhancing their adhesion behavior. Hence, these results are needful for improving the surface properties of a material, and obtaining better adhesion behavior on the membrane-like materials and recycling polymer materials.

Effect of water content on physical adhesion of polyacrylamide hydrogels

Hydrogels are widely used in flexible electronics and biomedical areas owning to their superior biocompatibility and stretchability. Previous studies have demonstrated that water content has significant effect on the elastic and fracture behaviors of hydrogels. However, the effect of water content on hydrogel adhesion has not been systematically explored. Herein, we carry out a series of experiments on polyacrylamide hydrogels with a wide range of water content and reveal that the physical adhesion properties of hydrogels are related to the water content. We find that with a variation of water content, the adhesion energy-water content relationship can be divided into four regions. The surface chain density and bulk energy dissipation of the polyacrylamide hydrogel and the water content and effective contact area over the interface between the hydrogel and the substrate synergistically contribute to this relationship. Specifically, at extremely low water content of ∼ 30%, polyacrylamide hydrogels exhibit one order of magnitude higher adhesion energy than that at relatively high water content. It is also found that with the decrease of water content, the maximum peeling force presents a similar trend to that of adhesion energy. According to our findings, we may control the adhesion performance and even achieve reversible adhesion of a hydrogel by simply adjusting the water content.

BONDING PROPERTIES OF Al/Al2O3 BULK COMPOSITES PRODUCED VIA COMBINED STIR CASTING AND ACCUMULATIVE PRESS BONDING

In this study, Al/Al2O3 composites have been fabricated by combined stir casting and accumulative press bonding (APB) processes. The effect of APB method on the bonding properties of bulk samples such as the number of APB process, Al2O3[Formula: see text]wt.% and the pressing temperature has been investigated by the peeling test. It is established that stronger bonding with a good quality can be obtained by increasing the pressing temperature and decreasing the Al2O3 particles[Formula: see text]wt.% as the reinforcement. Also, growing the step number of the APB method increases the bonding strength up to step#2 and then reduces the average peeling force due to the strain hardening result of the metallic matrix during the accumulative pressing. Finally, the effect of the APB method on the peeling surface of samples has been investigated using the scanning electron microscopy.

Effect of Fertilisation with Ash from Biomass Combustion on the Mechanical Properties of Potato Tubers (Solanum tuberosum L.) Grown in Two Types of Soil

The aim of the research was to determine the effect of fertilising with various doses of ash from biomass combustion (D2–D6) compared to control plots and classic NPK (D1) fertiliser on the morphological and mechanical properties of potato tubers (Solanum tuberosum L.). The field experiment was carried out in the years 2019–2021 (south-eastern Poland, 49°59′ N, 21°57′ E) on two types of soil: Gleyic Chernozem (silty loam) and Haplic Luvisol (silt). The values of mechanical parameters, such as the peel and flesh punching force (FD), deformation (DR) and energy (ED) needed to destroy the test sample, were assessed. The biometric features of the tubers were also assessed. It was found that tubers obtained from the experimental fields where D3 and D4 ash fertiliser doses were applied (corresponding to doses of 188 and 282 kg∙ha−1 K) had the highest tuber yields and the highest resistance to mechanical damage under quasi-static loads. Ash from biomass combustion can be an alternative to conventional mineral fertilizers and can be used in the development of mineral fertilization plans for sustainable agriculture, which will help to solve the problem of storage of this waste.

Release properties of plasma polymeric coated polymer films and adhesive strength of transferred polyurethane coatings to fiber-reinforced thermosets

An investigation of plasma-polymeric coatings on stretchable polymer films utilizing hexamethyldisiloxane and oxygen has been performed. The influence of the plasma parameters on release properties to polyurethane paints as well as the unpreventable transfer of traces of plasma-polymeric coatings to paints or thermosets were investigated. The elemental composition and physical properties have been analyzed using contact angle measurement and X-ray photoelectron spectroscopy (XPS) with peak fitting. The release properties of the coatings are discussed. The results show that a higher ratio of oxygen to hexamethyldisiloxane during the plasma process leads to an increase of peel forces to polyurethane paints. The XPS shows that the transfer of plasma coating to the paint is on average below 0.4 at% of silicon, which is below the critical fraction of 2 at% silicon reported in the literature. Therefore, the clear-coat paint shows no difference in its adhesion to thermosets between untreated and pretreated surfaces.

Freezing-Tolerant, Nondrying, Stretchable, and Adhesive Organohydrogels Inspired by the DNA Double Helix Structure for a Flexible Dual-Response Sensor

Due to the unique flexibility and modifiability of hydrogels, hydrogel-based wearable sensors have drawn tremendous attention. However, traditional hydrogels rigidify or dehydrate at extreme temperatures because their included water freezes or evaporates, which greatly impedes the development and practical application of the hydrogel-based wearable sensor. Herein, a temperature-tolerant organohydrogel with self-healing properties, adhesiveness, plasticity, and high stretchability was designed by introducing the specific base pairs, adenine (A) and thymine (T), into the polyacrylamide network in a water–glycerol (Gly) binary solvent. The gelation process was mainly driven by the covalent cross-linking and the complementary base pairing of the double helix structure of DNA. The prepared organohydrogels exhibited a tensile strength of 35 kPa, a toughness of 667 kJ m–3, and were highly flexibile with a rupture elongation of 3870%. Moreover, the organohydrogel demonstrated an excellent adhesive performance toward diverse organic and inorganic substrates. The organohydrogel displayed a maximum peeling force and adhesion strength of organohydrogel to filter paper of 149 and 122 kPa, respectively. In addition, the organohydrogel presented a rapid self-healing efficiency, long-term moisture retention, and good conductivity, even at subzero temperatures (−20 °C), and can be assembled as a dual strain and thermal sensor to realize the dual-sensing. The organohydrogel strain sensor exhibited a higher sensing sensitivity [gauge factor (GF) = 11.99] over a broad strain range (∼660%) and long-term durability (>135 cycles) and can be attached to the human body to monitor human motion in real-time. Significantly, the organohydrogel still maintained its high strain sensitivity (GF = 9.76) even at a lower temperature. We envisage that this study will provide a theoretical guidance for the design and development of multifunctional conductive hydrogels with antifreezing and antidrying properties and extend the application of the hydrogel-based sensor in electronic skin, flexible control panel, wearable devices, and health monitoring in extreme environments.

Experimental and Numerical Peeling Investigation on Aged Multi-Layer Anti-Shatter Safety Films (ASFs) for Structural Glass Retrofit

Anti-shatter safety films (ASFs) are often used for structural glass applications. The goal is to improve the response of monolithic elements and prevent fragments from shattering. Thus, the main reason behind their use is the possibility to upgrade safety levels against the brittle failure of glass and minimize the number of possible injuries. However, the impact response of glass elements bonded with Polyethylene terephthalate (PET)-films and pressure sensitive adhesives (PSAs) still represents a research topic of open discussion. Major challenges derive from material characterization and asymmetrical variability under design loads and ageing. In particular, the measurement of interface mechanical characteristics for the adhesive layer in contact with glass is a primary parameter for the ASF choice optimization. For this reason, the present paper presents an experimental campaign aimed at calibrating some basic mechanical parameters that provide the characterization of constitutive models, such as tensile properties (yielding stress and Young modulus) for PET-film and adhesive properties for PSA (energy fracture and peel force). In doing so, both tensile tests for PET-films and peeling specimens are taken into account for a commercially available ASF, given that the peeling test protocol is one of most common methods for the definition of adhesion properties. Moreover, an extensive calibration of the Finite Element (FE) model is performed in order to conduct a parametric numerical analysis of ASF bonded glass solutions. Furthermore, a Kinloch approach typically used to determine the fracture energy of a given tape by considering a variable peel angle, is also adopted to compare the outcomes of calibration analyses and FE investigations on the tested specimens. Finally, a study of the effect of multiple aspects is also presented. The results of the experimental program and the following considerations confirm the rate dependence and ageing dependence in peel tests.

Secondary embossing method for the capsulation of high-sensitive flexible piezoresistive sensors

Due to the mismatch between thermal expansion and hygroscopic expansion coefficients of polymer packaging materials, the stress and reliability of packaging structure present significant influences on the performance of flexible sensors. In this work, a new capsulation method for polymer-based flexible piezoresistive sensing systems was proposed based on differential-temperature hot embossing. The capsulate mold of the flexible sensing system is designed and the flexible sensor is packaged into a polydimethylsiloxane (PDMS) film to form a “sandwich” structure. The influences of the first embossing pressure and the second embossing time on capsulation result were investigated systematically. The results showed that the optimal parameters for the first embossing pressure and second embossing time were 1.4 MPa and 180 s, respectively. The interlayer peel force of obtained samples under this condition could reach a maximum of 5.7 N. This PDMS bulk bonding method can improve the cracking problem of the sample and provide more effective protection for the flexible sensors, compared with the traditional capsulation methods, this packaging method has little effect on sensor sensitivity (decreased by 0.64 kPa−1). After the packaging is completed, the polymer-based flexible piezoresistive sensor presents a high sensitivity (−5.64 kPa−1), and at the same time, a fast response (92 ms).

Critical peeling of tethered nanoribbons.

The peeling of an immobile adsorbed membrane is a well-known problem in engineering and macroscopic tribology. In the classic setup, picking up at one extreme and pulling off result in a peeling force that is a decreasing function of the pickup angle. As one end is lifted, the detachment front retracts to meet the immobile tail. At the nanoscale, interesting situations arise with the peeling of graphene nanoribbons (GNRs) on gold, as realized, e.g., by atomic force microscopy. The nanosized system shows a constant-force steady peeling regime, where the tip lifting h produces no retraction of the ribbon detachment point, and just an advancement h of the free tail end. This is opposite to the classic case, where the detachment point retracts and the tail end stands still. Here we characterise, by analytical modeling and numerical simulations, a third, experimentally relevant setup where the nanoribbon, albeit structurally lubric, does not have a freely moving tail end, which is instead elastically tethered. Surprisingly, novel nontrivial scaling exponents appear that regulate the peeling evolution. As the detachment front retracts and the tethered tail is stretched, power laws of h characterize the shrinking of the adhered length, the growth of peeling force and the peeling angle. These exponents precede the final total detachment as a critical point, where the entire ribbon eventually hangs suspended between the tip and the tethering spring. These analytical predictions are confirmed by realistic MD simulations, retaining the full atomistic description, also confirming their survival at finite experimental temperatures.

Effect of surface roughness of electroplating chromium coated steel on bonding strength of polymer coated steel

The effect of surface roughness of electroplating chromium coated steel on bonding strength of polymer coated steel has been investigated in this paper. The experimental results have shown that the electroplating chromium coated steel with different surface roughness could be obtained through the substrate surface treatment before the electroplating process. The peeling test results have shown that the peeling force of the polymer coated steel would increase with the increase of surface roughness of the electroplating chromium coated steel, but the increase rate would become slow gradually. With the increase of surface roughness of electroplating chromium coated steel, the PET film would be damaged locally and some polymer residues would remain on the electroplating chromium coated steel; when the bonding force is large enough, the plating shedding would occur on the electroplating chromium coated steel. With the appearance of the polymer residues and the occurrence of plating shedding, the failure mode of polymer coated steel would transform from adhesion failure mode to the mixed failure mode.

Variable Stiffness Electroadhesion and Compliant Electroadhesive Grippers.

Soft adhesion is capable of attaching and bonding to rough surfaces and gripping nonplanar materials. It is preferable for material handling applications where safe interactions with external environments and enhanced adaptability to changing conditions are required. Soft electroadhesion (EA) is an emerging controllable adhesion technology that is especially suited to soft adhesion applications, but is prone to contact peeling that causes unwanted de-adhesion and cannot lift heavy objects unless the lifting force is applied parallel to the surface. Variable stiffness electroadhesion (VSEA) can be used to overcome these issues. Here a VSEA solution is developed by integrating electrostatic layer jamming and soft EA into a monolithic electrically controllable structure. The VSEA pad can achieve rapid response (within 1 s) and significant stiffness change (2200%), resist over four times the peeling force under a weight of 70 g, and generate 24.2%, 34.8%, and 49.3% greater adhesive forces on flat, convex, and concave surfaces, respectively. The promising gripping performance of the VSEA gripper was demonstrated by lifting and moving curved and flat objects. The VSEA concept and solution shown in this work may pave the way for the ready integration of EA into soft robotic systems and promote the broad application of EA technologies.

Door sealing mechanism and process in vehicle engineering

The reliability of door sealing plays an important role in maintaining the quality of vehicle noise, vibration, and harshness (NVH). To improve the reliability of door sealing, a novel sealing process has been proposed. The factors influencing the door sealing quality have been investigated. The relationships between the peeling force, peeling speed, and peeling time have been calculated using the five-variable rheological theory. The maximum stress versus time curve and the distribution of stress and strain at the moment of debonding have been obtained by nonlinear solid cohesive coupling dynamics simulation. The rolling process of the door sealing strip has been developed, and automatic rolling equipment for door sealing has been designed and manufactured. The factors influencing the peeling force have been determined by a peeling test of the door sealing strip. The results show that the peeling force increases with an increase in the peeling speed and time. The C-shaped structure at the front end of the base material during the stripping process makes the peeling angle sharp. In addition, the uneven stripping speed causes the stripping line to become irregular. The peeling force increases with the increase in rolling pressure and failure time. The optimum rolling pressure was 70 N/m2 and the optimum aging time was 24 h.

Changes in Surface Characteristics of BOPP Foil after Treatment by Ambient Air Plasma Generated by Coplanar and Volume Dielectric Barrier Discharge.

Biaxially oriented polypropylene (BOPP) is a highly transparent polymer defined by excellent mechanical and barrier properties applicable in the food packaging industry. However, its low surface free energy restricts its use in many industrial processes and needs to be improved. The presented study modifies a BOPP surface using two different atmospheric-pressure plasma sources operating in ambient air and capable of inline processing. The volume dielectric barrier discharge (VDBD) and diffuse coplanar surface barrier discharge (DCSBD) were applied to improve the wettability and adhesion of the 1–10 s treated surface. The changes in morphology and surface chemistry were analyzed by SEM, AFM, WCA/SFE, and XPS, and adhesion was evaluated by a peel force test. Comparing both plasma sources revealed their similar effect on surface wettability and incorporation of polar functional groups. Additionally, higher surface roughness in the case of VDBD treatment contributed to slightly more efficient adhesion in comparison to DCSBD. Although we achieved comparable results for both plasma sources in the term of enhanced surface wettability, degree of oxidation, and stability of induced changes, DCSBD had less effect on the surface deterioration than VDBD, where surface structuring caused an undesirable haze.

Substrate temperature effects on the peel behavior of temporary pavement marking tapes

ABSTRACT Temporary pavement marking (TPM) tapes are utilized In road construction to delineate temporary traffic lanes and work zones. Adhesive failure of TPM tapes can therefore remove lane and work zone designations, confusing drivers and causing serious accidents, especially in high speed zones. Thus, the adhesion of TPM tapes to pavement surface plays an important role in road construction traffic safety. Pressure sensitive adhesives (PSAs) comprise the adhesive layer of TPM tapes. The adhesion of PSAs depends on their temperature-dependent viscoelastic properties. Since environmental conditions vary during construction, the adhesion of TPM tapes will change over a range of operating temperatures. The viscoelastic properties and peel force of four brands of commercial TPM tapes were characterized via double lap shear dynamic mechanical analysis and 90° angle peel adhesion testing over a range of temperatures (−20°C to 40°C). The interfacial fracture behavior and peel forces were analyzed with respect to the measured viscoelastic properties of TPM tapes. For temperatures below the glass transition temperature of the top layer and the transition temperature into the rubbery plateau of the PSA, the peel force decreased. Through this simple technique, an effective operating temperature range for each TPM tape was determined.

Influence and optimization of parameters of prepreg viscosity during placement

This paper tested the viscosity of prepreg in the automatic placement process, and conducted the probe and placement-90° peel tests through the test systems. The law of variation of prepreg viscosity during the laying process was studied through these tests under different conditions by taking the peel force to intuitively and quantitatively characterise the viscosity of the prepreg. The results show that this viscosity is inversely proportional to the laying rate, proportional to the laying pressure, and quadratic to the laying temperature. Then, peel tests were simulated to validate both the correctness of the peel test and that of the probe test data fitting the two-line cohesion model. On this basis, a response surface test for laying and peeling was designed. Taking viscous peel force as the response target, the laying process parameters were optimised and the significance of their influence was further studied. The error between the test value and the predicted value of the maximum viscous peel force is 3.03%.

A Tough Reversible Biomimetic Transparent Adhesive Tape with Pressure-Sensitive and Wet-Cleaning Properties.

Dry adhesives that combine strong adhesion, high transparency, and reusability are needed to support developments in emerging fields such as medical electrodes and the bonding of electronic optical devices. However, achieving all of these features in a single material remains challenging. Herein, we propose a pressure-responsive polyurethane (PU) adhesive inspired by the octopus sucker. This adhesive not only showcases reversible adhesion to both solid materials and biological tissues but also exhibits robust stability and high transparency (>90%). As the adhesive strength of the PU adhesive corresponds to the application force, adhesion could be adjusted by the preloading force and/or pressure. The adhesive exhibits high static adhesion (∼120 kPa) and 180° peeling force (∼500 N/m), which is far stronger than those of most existing artificial dry adhesives. Moreover, the adhesion strength is effectively maintained even after 100 bonding-peeling cycles. Because the adhesive tape relies on the combination of negative pressure and intermolecular forces, it overcomes the underlying problems caused by glue residue like that left by traditional glue tapes after removal. In addition, the PU adhesive also shows wet-cleaning performance; the contaminated tape can recover 90-95% of the lost adhesion strength after being cleaned with water. The results show that an adhesive with a microstructure designed to increase the contribution of negative pressure can combine high reversible adhesion and long fatigue life.

Nonwetting Nanostructured Hemostatic Material for Bleeding Control with Minimal Adhesion

AbstractHemostatic materials are widely used for bleeding control. However, existing blood‐absorbing wound dressing materials have two unaddressed challenges, blood loss through the hydrophilic material and strong clot adhesion that prevents gauze removal. Here, a nonwetting nanofiber structured material based on a two‐step spray coating procedure for hemostatic application is developed. Interfacial behaviors at the blood/clot‐material interface are exploited for bleeding control and minimizing wound adhesion. It is shown that this nonwetting material can retain blood within the wound, thus preventing blood loss. The nanofiber structure and kaolin microparticles collectively promote fast clotting to seal the wound and generate point‐to‐point contacts between clot and the nanofiber surface. These point‐to‐point contacts would subsequently be damaged by the interfacial shear induced by clot contraction, generating a peeling force significantly smaller than commercial low‐adherent or fast‐clotting hemostatic products. Its bleeding control and low adhesion properties are verified by in vivo animal experiments. The work therefore provides an efficient hemostatic material with excellent bleeding control and low wound adhesion properties, demonstrating an effective strategy to design advanced hemostatic materials by exploiting the interfacial behaviors.

Peeling and sliding of graphene nanoribbons with periodic van der Waals interactions

The peeling and sliding behaviors of graphene nanoribbons (GNRs) atop a graphene substrate are studied by a continuum model and numerical simulations. A periodic potential energy function is used to simulate the van der Waals interactions between the GNRs and the substrate in both the normal and tangential directions, coupling adhesion and friction within the same model. Numerical simulations and associated analyses reveal remarkably rich dynamics in peeling and sliding of GNRs. It is found that the simple 90-degree peeling of a GNR depends primarily on the normal (adhesive) interactions, with negligible sliding or shear interactions. In contrast, peeling with the end fixed in the in-plane directions leads to stick-slip sliding, with a higher peeling force and a critical peeling angle depending on both adhesion and friction. Notably, the stick-slip sliding is facilitated by formation and gliding of strain solitons in GNRs, and different types of strain solitons may form in the zigzag, armchair and chiral GNRs, including tensile, shear and mixed types. Unconstrained sliding is typically accompanied by both lateral and normal displacements, while constraining the displacements in the normal or lateral directions would generally lead to a higher pulling force for sliding. The peak pulling force as a measure of the sliding friction depends on the ribbon width quasi-linearly but becomes nearly independent of the ribbon length for relatively long GNRs (L >20 nm). Finally, two cases with coupled peeling and sliding of GNRs are considered, and a simple analysis is proposed to simultaneously determine the adhesion and friction properties of GNRs from measurable quantities in potential experiments.

Paraffin-Coated Hydrophobic Hemostatic Zeolite Gauze for Rapid Coagulation with Minimal Adhesion.

To solve the problem of strong adhesion and excessive blood loss caused by the use of hydrophilic zeolite gauze (Z-Gauze) in uncontrollable bleeding, we have modified the surface of commercial Z-Gauze with a paraffin coating and prepared a hydrophobic dressing PZ-Gauze. After paraffin coating, the adhesion of Z-Gauze was reduced without an obvious decrease in coagulation activity. The clotting time of the hydrophobic PZ-Gauze was reduced from 378.3 to 154.6 s compared with that of cotton gauze, and the peeling force was decreased from 348.8 to 84.7 mN compared with that of Z-Gauze. Besides, PZ-Gauze can efficiently cut down the blood loss during treatment. On the basis of in vitro and in vivo experiments, it is confirmed that surface hydrophobic modification does not change the procoagulant performance because of the maintained cation exchange capacity of zeolites, and the reduced blood loss as well as enhanced difficulty for fibrin adhesion is attributed to its hydrophobicity. This is different from the traditional gauze procoagulant theories, where gauze hydrophilicity and procoagulant performance are always positively correlated.