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•Acrylate-based stretchable, optically transparent PSAs are synthesized.•Synthesized PSAs exhibit high adhesion strength and rapid strain reversibility.•PSAs show high optical ...transparency in the visible regime.•PSAs exhibit excellent compatibility with the corrosion sensitive layer.•Pre-strain strategy enables instantaneous recovery of PSAs upon strain relaxation.
In the era of the Internet of Things, digital displays play a critical role in human–machine interfaces. In particular, displays applied to contemporary devices such as flexible smart watches and foldable/rollable electronics underline the need for pertinent materials and device technologies to fulfill their designed functions. However, despite the technical advancements of electronic components such as stretchable/flexible electrodes and flexible backplanes, their proper assembly remains a challenge. Herein, we report the compositional effect of acrylic acid (AA) on the physical properties of as-synthesized pressure sensitive adhesives (PSAs), especially on their adhesion performance in terms of wettability and peel adhesion. Accordingly, an empirical criterion for intimate wetting is proposed based on the storage modulus of the PSAs. In this study, the PSA with the best adhesion performance was evaluated for its viscoelastic properties and suitability for specific applications. The results demonstrated the strain-dependent conformational recovery of the adhesive; the implementation of the prestrain strategy enables rapid strain reversibility at 25% of the total strain. Furthermore, the AA-incorporated PSAs exhibited remarkable metal corrosion resistance as well as high optical clarity. Thus, this fundamental study of stretchable PSAs can provide useful guidance for the development of advanced PSAs that can be used in a wide range of applications involving display devices.
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•Stretchable and optically clear PSAs are synthesized.•PSAs containing 2-carboxyethyl acrylate show exceptional adhesion strength and flexibility.•PSAs exhibit high optical clearance ...in the visible light range.•Pre-straining strategy triggers instantaneous strain recovery at repetitive cycle test.•The synthesized PSAs exhibit outstanding stability for foldable and epidermal devices application test.
Since the development of the 5G network, wireless and user-oriented electronics are rapidly emerging. In response to demands for wearable devices, which are curved, bendable and/or stretchable, all components of electronics are required to be flexible. Moreover, the assembly of these components is challenging issue, because the conventional adhesives used in displays are typically rigid unsuitable for flexible electronics. Therefore, developing elastic pressure-sensitive adhesives (PSAs) is critical for the commercialization of flexible electronics. In this study, UV curable acrylate-based PSAs are synthesized using 2-carboxyethyl acrylate (CEA) as a functional monomer, and exhibit exceptionally strong peel adhesion and good flexibility. The synthesized film also exhibits adequate transmittance (>95%) to be used as an optically clear adhesive. The stress-relaxation and strain-recovery behavior of the PSAs at various conditions is evaluated and analyzed in detail. To induce elastic characteristics in the PSAs, a pre-straining strategy is implemented, which triggers a purely elastic characteristic with instantaneous strain recovery. The pre-strained PSAs were able to withstand 5000 cycles of repetitive stretching and bending tests; thus, the synthesized PSAs can provide wide range of applications, including stretchable displays and epidermal devices.
Recently, the interest in flexible displays has been increasing due to the demand for wearable and flexible electronics which can be curved, bent and/or stretched without impinging their performance. ...Most importantly, the development of stretchable adhesives is indispensable in order to adhere the components of the stretchable display without defects or flaws at interfaces during operation. In this study, UV curable pressure sensitive adhesives (PSAs) composed of acrylic monomers were successfully characterized in terms of physical properties for the stretchable display application. With the base monomer of 2-ethylhexyl acrylate, various acrylic monomers exhibited different properties, especially instantaneous strain reversibility was achieved using methyl acrylate (MA) and 2-hydroxyethyl acrylate (HEA). Interestingly the MA incorporated PSA became more elastic as strain increased from 15% to 30%, reducing hysteresis loss close to zero. Acrylic acid (AA) containing PSA showed significantly higher peel adhesion compared to the other monomers. Rheological studies are also performed to support the aspect of the peel adhesion values which correspond to the trend of loss modulus (G”). Transmittance of each synthesized PSA was sufficiently clear (>95%) demonstrating the feasibility of synthesized UV curable PSAs for optically clear adhesives.
•Acid functionality plays an important role to improve peel adhesion by increasing loss modulus (energy dissipation).•Methyl and hydroxyl functional groups demonstrate instantaneous strain reversibility.•Acrylamide-free pressure sensitive adhesives guarantee high light transmittance.
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This work aimed at evaluating the influence of glycerol concentration and storage relative humidity (RH) on gluten-based adhesive properties. Adhesive aging and adhesive application ...over different food substrates were also evaluated. For such purpose, three adhesive formulations were developed from different gluten:glycerol ratios (1:0.6, 1:1, and 1:1.4), which were applied over a pectin-based film as support material. The adhesives presented better adhesion and cohesion properties when stored at 58% RH. The formulation with the best adhesive properties was the 1:1 gluten:glycerol ratio. The degradation of the adhesives during aging was considered small in the first thirty days. The adhesives presented potential to be applied on food grade materials with low hydrophilicity.
•The carboxymethyl starch(CMS)/carboxymethyl cellulose (CMC) films were prepared.•The polysaccharide derivatives-based films were applied as human skin equivalent.•The most promising system CMS/CMC ...25/75 wt. % was selected.•The PSA used in medical patches: acrylic, silicone and polyisobutylene were tested.•The peel adhesion for human skin and the CMS/CMC equivalent were on the same level.
The films based on carboxymethyl derivatives of starch (CMS) and cellulose (CMC) were proposed as a novel human skin equivalent. The physicochemical properties (moisture absorption, solubility in water, mechanical properties) of CMS/CMC films were evaluated. Additionally, some properties were compared to the human skin ones (surface roughness, tribology). The system based on CMS/CMC 25/75 wt. % was selected for testing the adhesive properties of pressure-sensitive adhesives commonly used for medical purposes (acrylic, silicone and polyisobutylene). Similar tests were performed for human skin. The peel adhesion values for CMS/CMC film and human skin were similar for all adhesives types tested. Applying such a skin equivalent allows to evaluate the functional properties of medical pressure-sensitive adhesives without the ethical and economic issues.
Adhesive sealing tapes play an important role in ensuring the air tightness of the building, affecting the indoor microclimate and efficient energy use. However, there is still a lack of objective ...indicators that would demonstrate the ability of the sealing tape to ensure the long-term air tightness of the sealing joints of various building structures. Therefore, the purpose of this work is to investigate the indicators demonstrating the suitability of adhesive sealing tapes for sealing building structures of different surfaces and deformation, to provide detailed analyses of the results, and to propose practical recommendations. The investigated self-adhesive tapes differed in backing (nonwoven material, plastic reinforced film, paper, metal foil) and adhesives (acrylic and butyl). The materials of the sealed structural joints were plywood, OSB, plasterboard, cement sawdust board, plastered board, and plastic. The thickness, deformability, peel and shear adhesion of the self-adhesive tapes were used to determine its suitability for sealing of different structural joints. It was determined that tapes with higher deformability are more versatile, as they are suitable for sealing joints subjected to small and large deformations. The higher peel adhesion is typical for tapes of an air-permeable non-woven material backing and a thin adhesive layer. Tapes with a thicker adhesive layer are most suitable for sealing complex-shaped joints. Tapes with acrylic adhesive have a higher peeling force from smooth and moderately smooth surfaces, whereas butyl adhesive creates better contact with uneven surfaces in highly deformable joints.
UV-polymerizable and UV-crosslinkable pressure-sensitive adhesive acrylic compositions are widely applied for high-quality carrier-free films, one-sided or double-sided self-adhesive tapes. ...Comprehensive studies of the properties of novel acrylic PSAs for carrier-free films or adhesive tapes were carried out. Solvent-free acrylic pressure-sensitive adhesive layers were UV-crosslinked using various photoreactive crosslinking agents. Polymer content during UV-polymerization, prepolymers viscosity, temperature changes of prepolymer during UV-initiated polymerization process were investigated. The chemical structure of prepolymer and polymerized acrylic film were examined using FTIR spectroscopy. Prepolymer mixtures were transferred on the transparent carriers to form 1 mm thick polymer films, and then UV-crosslinked after the addition of the selected acrylic crosslinker. Final adhesive films were then tested to evaluate their functional properties as the tack, peel adhesion, and shear strength at 20 °C and 70 °C. From the results reveal that both concentrations of acrylic acid in the prepolymer, and cross-linking agent in the final polymer layer, have a significant influence on the functional properties of the produced PSA films.
•Selected multifunctional acrylates were evaluated as photoreactive crosslinking agents for acrylic solvent-free PSA films.•Viscosity, polymer content of synthesized pre-polymers and temperature changes during polymerization were tested.•Samples of UV-crosslinked PSAs were evaluated to determine their properties as tack, peel adhesion and shear strength.•The studies proved an effect of AA conc. in the pre-polymer and the type and conc. of the crosslinking agent on the properties of PSAs.
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•Thermoplastic polyurethane coatings with good tack at 10–37°C can be prepared by using mixtures of polyethers of different molecular weights.•Thermoplastic polyurethane coatings may ...exhibit pressure sensitive adhesion property.•The segmented structure (i.e., degree of phase separation) of thermoplastic polyurethane determines its pressure sensitive adhesion property.•Thermoplastic polyurethane coatings had good potential as removable pressure sensitive adhesives (PSAs).
Thermoplastic polyurethane (PU) coatings with pressure sensitive adhesion property were synthetized by reacting 4,4′-diphenylmethane diisocyanate (MDI) with 1,4-butanediol and mixtures of polypropylene glycols (PPGs) of different molecular weights (1000 and 2000Da). Good tack at 10–37°C was obtained in PU coatings prepared with PPG2000+PPG1000 mixtures containing 50wt% or more PPG2000. The pressure sensitive adhesion properties of the PU coatings were related to their minor content of bonded urethane groups and important degree of phase separation. Furthermore, these PU coatings followed Dahlquist criterion, they showed low glass transition temperatures, high tack, and low 180° peel strength. Therefore, the PU coatings had potential as pressure sensitive adhesives. Finally, PU coating made with PPG of molecular weight 1000Da did not show pressure sensitive adhesion property.
An acrylic pressure-sensitive adhesive (PSA) was synthesized in ethyl acetate at about 80 °C by the use of 2-ethylhexyl acrylate, ethyl acrylate, methyl acrylate and acrylic acid at presence of ...thermal radical initiator AIBN. The synthesized acrylic PSA was crosslinked at relatively low temperatures at about 110–125 °C using thermal crosslinkers selected from melamine-formaldehyde resins and benzoguanamine resins. The crosslinking process runs between carboxylic groups of acrylic PSA and reactive groups from investigated amine resins. The choice of suitable thermal reactive crosslinkers has significant and relevant influence at presence of organic acid catalysts on main performance of crosslinked PSA such as tack, peel adhesion and shear strength.
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•Melamine-formaldehyde resins and benzoguanamine resins as the thermal crosslinkers.•Effect of thermal reactive crosslinkers on main performance of crosslinked PSA.•The stability thermal crosslinkable systems depends on the amino resin type, the amount of the acid catalyst and the solid content of the solvent-borne acrylic pressure-sensitive adhesives.•Amino resin crosslinked PSA systems containing an acid catalyst are stable for several hours or several days.•The addition of isopropanol results in aprolonging of the pot-life up to a few months.
In recent decades, the basic technology of pressure-sensitive adhesive (PSA) acrylics has developed into a sophisticated science. The main properties of acrylic PSAs such as tack, peel adhesion, and ...shear strength are determined to a large extent by the kind and quantity of crosslinking agents added to the synthesized PSAs. In order to improve their adhesive (tack, peel adhesion) and cohesive (shear strength) properties, a wide range of amino resin thermal crosslinkers are tested. An acrylic PSA based on 2-ethylhexylacrylate, n-butyl acrylate, and acrylic acid was synthesized by performing a radical polymerization in ethyl acetate. After the addition of amino resins to the acrylic PSA and carrying out thermally initiated crosslinking processes to prepare one-sided self-adhesive tapes, their properties were assessed.
•The type and amount of crosslinking agent has a significant impact on the properties of the pressure-sensitive adhesives.•Selected amino resins were evaluated as thermal reactive crosslinking agents for acrylic pressure-sensitive adhesives.•A wide range of amino resins was tested from the group of derivatives of melamine, benzoguanamine, glycoluril and urea.•Samples of crosslinked PSAs were evaluated to determine their properties such as tack, peel adhesion and shear strength.•Optimal balance between mentioned properties has been achieved for one benzoguanamine resin and for two melamine resins.
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