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

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

Validation of Wrinkling-to-Delamination Adhesion Measurement Technique

Polymer thin films have a wide range of applications that span several different industries. Their optical clarity as well as their mechanical rigidness result in their versatile use in applications such as contact lenses, wearable sensors, and flexible electronics. These applications require precise adhesion, so the need for a simple, quantitative adhesion measurement technique is critical. Several methods have already been developed that quantify the adhesion of flexible thin films attached to rigid substrates. However, when the thin films are rigid and the substrates compliant, these methods are insufficient. In the authors’ previous work, an adhesion measurement technique was developed that took advantage of well-characterized surface buckling instabilities that formed when the system was placed in lateral compressive strain, exploiting the wrinkling to delamination transition that occurred. This technique was proven to work for a narrow range of materials. Therefore, the focus of this paper was to validate this wrinkling to delamination adhesion measurement technique by utilizing a variety of film-substrate systems with varying surface energies and substrate moduli. In the authors’ previous work, the technique was validated using polystyrene (PS) and poly(methyl methacrylate) (PMMA) as high surface energy polymer thin films and poly(dimethyl siloxane) (PDMS) as a low surface energy substrate. In this work, Teflon AF 1600, a polytetrafluoroethylene copolymer, was utilized as a low surface energy thin film and bovine gelatin as a high surface energy substrate to determine the limitations of this adhesion technique

Particle Alignment Effects on Mechanical Properties of Cellulose Nanocrystal Thin Films

Cellulose nanocrystal (CNC) thin films are of increasing interest as sustainable materials due to their anisotropic mechanical properties. Previous computational work has shown that the fracture mechanisms of CNC films vary as a function of particle alignment with respect to the loading direction. However, it is challenging to experimentally measure the mechanical anisotropy of extremely thin CNC films due to their brittleness. Here, a new experimental approach was developed to identify the effect of CNC alignment on modulus while simultaneously observing the fracture mechanisms. In this method, uniaxial tensile strain is applied to a CNC film laminated on a silicone substrate with a mechanical stage mounted over a microscope. The modulus calculated by measuring the wavelength of wrinkles that formed perpendicular to the tensile strain direction at low strains during mechanical testing. The elastic modulus of CNC films decayed exponentially as the misalignment of particles to the loading direction increased. By carrying out coarse-grained modeling and comparing the misalignment angle with the crack opening direction beyond the fracture strains, fracture mechanism dependence on misalignment was observed

Mechanical Properties of Durable Pavement Marking Materials and Adhesion on Asphalt Surfaces

Mechanical properties of commercially available temporary pavement marking (TPM) tapes and thermoplastic materials used as permanent pavement markings (PPM) were investigated using the non-destructive Tape Drape Test and conventional mechanical testing. The impact of temperature and aging on the adhesion of TPM tapes and thermoplastic PPM applied to asphalt core surfaces with various surface roughness and treatments was determined using a modular peel fixture and shear adhesion tests. The adhesion of TPM tapes to model smooth surfaces decreased as surface temperature was increased from 0 to 40°C (32 to 104°F). For some tapes, reduced adhesion and brittle broken fracture were observed at the lowest investigated temperature of -20°C (-4°F). The adhesion of tapes applied to asphalt decreased significantly within 1 week of aging at -25°C (-13°F). Ghost markings were more likely at higher aging temperatures. For PPM thermoplastics, better adhesion to asphalt was observed for higher application temperatures and rougher surfaces. Asphalt emulsion treatments reduced the adhesion of thermoplastics and increased the likelihood of adhesive failure after 5 months of aging at -25°C (-13°F). More ductile PPM thermoplastic materials had better adhesion to both smooth and rough asphalt surfaces compared to thermoplastic materials with a more brittle mechanical response

Quantification of Pseudocapacitive Contribution in Nanocage-Shaped Silicon-Carbon Composite Anode

Pseudocapacitive materials have been highlighted as promising electrode materials to overcome slow diffusion-limited redox mechanism in active materials, which impedes fast charging/discharging in energy storage devices. However, previously reported pseudocapacitive properties have been rarely used in lithium-ion batteries (LIBs) and evaluation methods have been limited to those focused on thin-film-type electrodes. Hence, a nanocage-shaped silicon-carbon composite anode is proposed with excellent pseudocapacitive qualities for LIB applications. This composite anode exhibits a superior rate capability compared to other Si-based anodes, including commercial silicon nanoparticles, because of the higher pseudocapacitive contribution coming from ultrathin Si layer. Furthermore, unprecedent 3D pore design in cage shape, which prevents the particle scale expansion even after full lithiation demonstrates the high cycling stability. This concept can potentially be used to realize high-power and high-energy LIB anode materials

Analysis of Outcomes in Ischemic vs Nonischemic Cardiomyopathy in Patients With Atrial Fibrillation A Report From the GARFIELD-AF Registry

IMPORTANCE Congestive heart failure (CHF) is commonly associated with nonvalvular atrial fibrillation (AF), and their combination may affect treatment strategies and outcomes