The method of crosslinking a pressure-sensitive adhesive (PSA) significantly affects its properties. There are many different methods of crosslinking, but in recent times, ultraviolet radiation has ...been used more and more as one of the methods. The process of UV crosslinking is based on the photoinitiation of radical and cationic reactions. In the selection of the radiation source it is important that the absorption spectrum of the footprint coincides with the spectrum of the photoinitiator used. The photoinitiator (its chemical nature, the amount used) and the radiation source are the key elements of the UV network. In this work, the crosslinking of an acrylic adhesive was tested using a 4-acryloyloxybenzophenone photoinitiator. The influence of the UV radiation dose using two lamps, and the thickness of the adhesive layer on the self-adhesive properties of the acrylic adhesive was investigated.
This publication describes the influence of residue monomers in synthesized pressure-sensitive adhesives based on acrylics on their main properties-tack, peel adhesion, shear strength and ...shrinkage-in the form of transfer tapes used for joining wooden elements in the furniture industry. The discussed carrier-free adhesive tapes are synthesized via photo-crosslinking and photopolymerization with UV radiation of the photoreactive prepolymers sandwiched between two adhesive siliconized polyester films. The simultaneous crosslinking and polymerization processes carried out under UV lamps placed simultaneously above and below the crosslinked photoreactive polymer layer lead to the production of a carrier-free adhesive film. The preliminary target of these studies was to investigate how the intensity of UV radiation and the time of its exposure affect the viscosity of the photoreactive compositions and the content of unreacted monomers in them. Next, the influence of the crosslinking agent concentration and UV irradiation time on the content of unreacted monomers after the crosslinking process was tested. The last step of the studies was the investigation of the influence of the residue monomer concentration on the application properties of the obtained pressure-sensitive adhesive layers. The typical PSA application properties were tested on the wood samples: tack, peel adhesion, shear strength (cohesion) and shrinkage.
With the increasing demand for innovative electronic products, LED transparent screens are gradually entering the public eye. Polyimide (PI) materials combine high temperature resistance and high ...transparency, which can be used to prepare flexible copper-clad laminate substrates. The physical and chemical properties of PI materials differ from copper, such as their thermal expansion coefficients (CTEs), surface energy, etc. These differences affect the formation and stability of the interface between copper and PI films, resulting in a short life for LED transparent screens. To enhance PI-copper interfacial adhesion, aminopropyl-terminated polydimethylsiloxane (PDMS) can be used to increase the adhesive ability. Two diamine monomers with a trifluoromethyl structure and a sulfone group structure were selected in this research. Bisphenol type A diether dianhydride is a dianhydride monomer. All three of the above monomers have non−coplanar structures and flexible structural units. The adhesion and optical properties can be improved between the interface of the synthesized PI films and copper foil. PI films containing PDMS 0, 1, 3, and 5 wt% were analyzed using UV spectroscopy. The transmittance of the PI-1/3%, PI-1/5%, PI-2/3%, and PI-2/5% films were all more than 80% at 450 nm. Meanwhile, the Td 5% and Td 10% heat loss and Tg temperatures decreased gradually with the increase in PDMS. The peel adhesion of PI-copper foil was measured using a 180° peel assay. The effect of PDMS addition on peel adhesion was analyzed. PIs-3% films had the greatest peeling intensities of 0.98 N/mm and 0.85 N/mm.
Tape products containing ketoprofen have transdermal analgesic and anti-inflammatory effects. We compared the physicochemical properties (water-vapor permeability, peel force, peel force-time curve) ...between one brand-name product and eight generic products. Regarding the measurement of water-vapor permeability, the formulations using methacrylic acid n-butyl acrylate copolymer (MBA) adhesives showed higher water-vapor permeability than those using styrene isopropyl styrene block copolymer (SIS) adhesives. In the case of the formulation using SIS adhesive, the central part of the formulation had higher water-vapor permeability than both ends. In the 90-degree peel test using the methods of adhesion testing, significant differences were observed between the products, especially as the various application times (5 min, 30 min, 9 h and 24 h) increased. This may be because the longer the time of attachment to the adherend, the more the adhesive force with the adherend increased due to the "anchoring effect" of the adhesive. The measurement of the peel force-time curve showed different curves among the products, especially in the peel force curve of Teikoku after 24 h, which showed two characteristic peak curves. Furthermore, when the peel forces at 25°C and 40°C were compared, Mohrus and Toko showed significantly higher values at 40°C compared to 25°C. This study showed that there are many generic drugs with formulation characteristics different from those of brand-name drugs, and that there is a large difference among the products in terms of adhesion and detachment.
This paper describes peel adhesion of solvent-borne acrylic pressure-sensitive adhesives (PSA) crosslinked using crosslinking agent aluminum acetylacetonate (AlACA). The peel adhesion of acrylic PSA ...crosslinked with AlACA was evaluated as a function of adhesive coating weight and kind of tested substrates characterized by various surface free energies (SFE). The diverse substrates tested were stainless steel, poly(methyl methacrylate) (PMMA), polycarbonate (PC), polyethylene (PE), polypropylene (PP) and polytetrafluoroethylene (PTFE) known as Teflon. For peel adhesion determination the most common method in the adhesive tape and PSA industries was used. In order to evaluate surface free energies (SFE) of materials used in tack measurements the Owens–Wendt (OW) and van Oss–Chaudhury–Good (vOCG) methods were employed. The conducted experiments have shown, that a clear relationship exists between SFE of the substrate and peel adhesion of model acrylic PSA. In general, an increase of the difference in SFE between the substrate and adhesive (ΔSFE) affects positive peel adhesion.
Skin adhesives are polymer materials used for attaching medical devices to the skin. Probing the performance of such adhesives is of great interest for rational material formulation. Here, we present ...a perspiration simulator, which includes a skin mimicking gelatin substrate with controlled roughness and the ability to perspire with a tunable sweat rate. The setup was used for probing peel adhesion of adhesives under realistic wear conditions. Adhesives with indistinguishable rheological properties but different ability to absorb artificial sweat were evaluated. The rheological properties were fixed to decouple the bulk mechanical properties from events occurring at the substrate–adhesive interface. The effects of application pressure, dwell time, and perspiration were quantified for each adhesive formulation. Here, we found that sweat introduced at the substrate–adhesive interface restricts further bonding of the adhesives by limiting viscous flow. Water-absorbing skin adhesives were found to have significantly higher peel forces compared to nonabsorbing adhesives under sweating conditions where the adhesive could absorb the introduced sweat.
Transdermal patches and medicated plasters (patch) represent well-established prolonged release dosage forms. Even if satisfactory adhesion to the skin is strictly linked to the efficacy and safety ...of the therapeutic treatment, nowadays numerous reports of in vivo 'adhesion lacking' are still addressed to regulatory agencies. The adhesive properties of a patch should be characterized considering i) the ability to form a bond with the surface of another material on brief contact and under light pressure (tack); ii) the resistance of the adhesive to flow (shear adhesion); and iii) the force required to peel away a patch from a surface (peel adhesion).
In this manuscript, the most widely used methods to measure adhesive properties during development studies are described, along with the quality control of patches. The influence of formulative variables on patch adhesive properties, and their possible relationship with the in vivo adhesion performances, is also discussed.
The Pharmacopoeias should consider the opportunity of introducing compendial testing to assay the quality of adhesive patch properties, and regulatory agencies should issue proper guidelines to evaluate these features during development.
Maintaining adhesion on human skin during perspiration is challenging and may result in undesired detachment. Improvements in the performance are generally made by adjustments in the adhesive ...composition, which simultaneously changes the viscoelastic properties, sweat absorption capabilities, and peel adhesion. To aid the design of skin adhesives for prolonged wear, we systematically investigate the impact of the viscoelastic properties and the sweat absorption capabilities during perspiration. Therefore, four skin adhesives are designed with a stepwise variation in one of the properties at a time to decouple the different effects. A perspiration simulator is used during the study to ensure well-defined and reproducible perspiration conditions. Depending on the sweating pressure and the adhesive formulation, different failure mechanisms are observed. The sweating pressure delaminates the non-absorbing adhesives and causes adhesive failure. Thereby, viscoelastic flow and subsequent cavity growth occur if the sweating pressure overcomes the mechanical strength of the adhesive, while elastic detachment is observed otherwise. The addition of absorbing components results in a pressure relief and thus enables the maintenance of adhesion over prolonged periods. However, the absorption of sweat weakens the mechanical integrity of the adhesive and causes cohesively dominated failure during peel. These findings are also supported by the behavior of the adhesives on human skin before and after perspiration. This shows that the design of skin adhesives requires an intricate balance between viscoelasticity and sweat absorption in order to maintain adhesion during perspiration.
Tape products containing ketoprofen have transdermal analgesic and anti-inflammatory effects. We compared the physicochemical properties (water-vapor permeability, peel force, peel force-time curve) ...between one brand-name product and eight generic products. Regarding the measurement of water-vapor permeability, the formulations using methacrylic acid n-butyl acrylate copolymer (MBA) adhesives showed higher water-vapor permeability than those using styrene isopropyl styrene block copolymer (SIS) adhesives. In the case of the formulation using SIS adhesive, the central part of the formulation had higher water-vapor permeability than both ends. In the 90-degree peel test using the methods of adhesion testing, significant differences were observed between the products, especially as the various application times (5 min, 30 min, 9 h and 24 h) increased. This may be because the longer the time of attachment to the adherend, the more the adhesive force with the adherend increased due to the "anchoring effect" of the adhesive. The measurement of the peel force-time curve showed different curves among the products, especially in the peel force curve of Teikoku after 24 h, which showed two characteristic peak curves. Furthermore, when the peel forces at 25°C and 40°C were compared, Mohrus and Toko showed significantly higher values at 40°C compared to 25°C. This study showed that there are many generic drugs with formulation characteristics different from those of brand-name drugs, and that there is a large difference among the products in terms of adhesion and detachment.
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