An official website of the United States government
Abstract The fabrication of pressure sensitive adhesives (PSAs) using liquid crystal elastomers (LCEs), which are known for their excellent dissipation properties, is explored in this work. The adhesive properties of the PSAs are evaluated using the 180° peeling test at various conditions. The performance of the LCE adhesives is found to show significant rate and temperature dependence. When the adhesion energy is plotted against the rate, LCE shows an anomalously large power law exponent (n≈ 1.17) compared to existing PSAs (n≈ 0.1–0.6). The unusual rate sensitivity is hypothesized to originate from the synergy of soft elasticity and non‐linear viscoelasticity. The adhesive properties at various rates and temperatures are correlated to the results from dynamic mechanical analysis. Moreover, the large strain stiffening behavior of LCE under uniaxial tension reveals the distinctive advantages offered by LCE as adhesives. Time‐temperature superposition is used to obtain a master curve of adhesion energy that spans rates beyond typical experimental limits. The extreme rate dependence and the large strain stiffening of LCE yield a new category of adhesives that possess special properties, such as reversible adhesion and impact resistance, unlike traditional adhesives.
more »
« less
Experimental Studies of Impact Resistance of Pressure-Sensitive Adhesives
Abstract BackgroundPressure-sensitive adhesives (PSAs) are integral to various industrial applications, yet a significant gap remains in accurately assessing their impact properties under dynamic conditions. This limitation hampers the optimization of PSAs for specific uses where impact resistance is critical. ObjectiveThis study aims to develop an experimental method to evaluate the impact properties of PSAs, providing a reliable and reproducible technique to assess their performance. MethodWe designed an experimental setup to simulate real-world impact conditions, incorporating high-speed cameras and an image analysis algorithm to capture the adhesive's behavior under sudden loads. The method's novelty lies in its ability to quantify maximum failure load and adhesion failure mechanisms in the dynamic loading of PSAs. ResultsThe experimental results reveal critical insights into the impact resistance of various PSA formulations, highlighting significant differences in energy dissipation and failure patterns. ConclusionThese findings offer new data not previously available in the literature, enabling a more precise evaluation of PSA performance. The developed method provides a robust framework for assessing the impact properties of PSAs, offering valuable guidance for the design and selection of adhesives in applications requiring enhanced impact resistance. This work bridges the gap between quasi-static testing and realistic dynamic performance, contributing to the advancement of PSA technology.
more »
« less
- Award ID(s):
- 2035663
- PAR ID:
- 10634784
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Experimental Mechanics
- Volume:
- 65
- Issue:
- 6
- ISSN:
- 0014-4851
- Page Range / eLocation ID:
- 885 to 892
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The expanding applications of pressure sensitive adhesives (PSAs) in fields like bioelectronics, healthcare, and flexible displays call for an urgent study on their fatigue behaviors, i.e., damage and fracture under prolonged dynamic loads. However, such studies have been sparse in the field. Here we show prevalent low interfacial fatigue threshold in various PSAs through experimental cyclic peeling tests. We characterize interfacial fatigue fracture in PSAs including the 3M Scotch VHB 4905 tape, the 3M Scotch heavy duty shipping packaging tape, and two homemade PSAs. The two homemade PSAs consist of different poly(butyl acrylate) elastomeric bulks (low-hysteresis and high-hysteresis) dip-coated with identical viscoelastic poly(butyl acrylate-co-isobornyl acrylate) sticky surface layers. The measured interfacial fatigue thresholds are 3.7 J/m2, 10.8 J/m2, 9.8 J/m2, and 8.1 J/m2 for VHB, packaging tape, low-hysteresis PSA, and high-hysteresis PSA, respectively, all much lower than their bulk adhesion toughnesses at finite crack speeds. The interfacial fatigue threshold agrees qualitatively well with a modified Lake-Thomas model despite an underestimation of the model. However, the measured slow crack threshold in monotonic peeling is larger than the fatigue threshold and shows clear dependence on the bulk dissipation. We discuss possible mechanisms for these discrepancies and potential toughening strategies for PSAs. The new experimental data confirm the prevalence of low interfacial fatigue threshold in PSAs, and further suggest that the threshold is nearly independent of their bulk dissipation.more » « less
-
Natural glues offer great potential as bio-inspired solutions to problems associated with the performance of synthetic adhesives. Spider viscous glues are elastic pressure sensitive adhesives (PSAs) that physically adhere to surfaces on contact across a range of environmental conditions. Extracting useful components from these secretions remains a challenge that can be met by the comparative analyses of functional analogues. Here we used 1 H NMR spectroscopy and mass spectrometry to ascertain the organic salt compositions of the PSAs of four different species of Australian spiders belonging to two lineages that independently acquired aqueous gluey secretions: the St Andrew’s cross ( Argiope keyserlingi ), the redback ( Latrodectus hasselti ), the false widow ( Steatoda grossa ), and the daddy long-legs spider ( Pholcus phalangiodes ). The PSAs from each of these spiders contained similar organic salts, albeit in variable concentrations. The adhesives of the false widow and daddy long-legs spider had mixtures of only a few components, of which betaine predominated, while the PSAs of the other spiders predominantly contained small organic acids such as GABA/GABA-amide, isethionate, and choline salts. Our results suggest that the PSA composition of spiders is likely to be influenced more by environmental factors than evolutionary history and are guided by common principles. Our findings could be valuable for facilitating the design of more sustainable synthetic glues.more » « less
-
Pressure sensitive adhesives (PSAs) are ubiquitous materials within a spectrum that span from office supplies to biomedical devices. Currently, the ability of PSAs to meet the needs of these diverse applications relies on trial-and-error mixing of assorted chemicals and polymers, which inherently entails property imprecision and variance over time due to component migration and leaching. Herein, we develop a precise additive-free PSA design platform that predictably leverages polymer network architecture to empower comprehensive control over adhesive performance. Utilizing the chemical universality of brush-like elastomers, we encode work of adhesion ranging 5 orders of magnitude with a single polymer chemistry by coordinating brush architectural parameters−side chain length and grafting density. Lessons from this design-by-architecture approach are essential for future implementation of AI machinery in molecular engineering of both cured and thermoplastic PSAs incorporated into everyday use.more » « less
-
Abstract Pressure‐sensitive‐adhesives (PSAs) are pervasive in electronic, automobile, packaging, and biomedical applications due to their ability to stick to numerous surfaces without undergoing chemical reactions. These materials are typically synthesized by the free radical copolymerization of alkyl acrylates and acrylic acid, leading to an ensemble of polymer chains with varying composition and molecular weight. Here, reversible addition−fragmentation chain‐transfer (RAFT) copolymerizations in a semi‐batch reactor are used to tailor the molecular architecture and bulk mechanical properties of acrylic copolymers. In the absence of cross‐links, the localization of acrylic acid toward the chain ends leads to microphase separation, creep resistance, and enhanced tack. However, in the presence of Al(acac)3crosslinker, the creep resistance remains unchanged and mostly the large‐strain mechanical properties are affected. This behavior is attributed to microphase separation, but also to a change in the energy required to break physical associations, and untangle and elongate associative polymers to large deformations.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1007/s11340-025-01176-z
