UV-cured Pressure Sensitive Adhesives Research Articles

Thermally Stable UV-Curable Pressure-Sensitive Adhesives Based on Silicon-Acrylate Telomers and Selected Adhesion Promoters.

A new type of UV-curable pressure-sensitive adhesive containing Si atoms (Si-PSAs) was prepared by a solution-free UV-initiated telomerization process of n-butyl acrylate, acrylic acid, methyl methacrylate, and 4-acrylooxybenzophenone using triethylsilane (TES) as a telogen and an acylphosphine oxide (APO) as a radical photoinitiator. Selected commercial adhesion promoters were tested as additives in the formulation of adhesive compositions, i.e., (i) an organic copolymer with polar groups (carboxyl and hydroxyl); (ii) a hydroxymetal-organic compound; and (iii) a quaternary ammonium salt and (iv) a chlorinated polyolefin. No fillers, crosslinking agents, or photoinitiators were used in the adhesive compositions. NMR techniques confirmed the incorporation of silicon atoms into the polyacrylate structure. The influence of adhesion promoters on the kinetics of the UV-crosslinking process of Si-PSAs was investigated by a photo-DSC technique. The obtained Si-PSAs were characterized by adhesion (to steel, glass, PMMA, and PE), tack, and cohesion at 20 °C. Finally, the wetting angle of Si-PSAs with water was checked and their thermal stability was proved (TGA). Unexpectedly, the quaternary ammonium salt had the most favorable effect on improving the thermal stability of Si-PSAs (302 °C) and adhesion to glass and PMMA. In contrast, Si-PSAs containing the hydroxymetal-organic compound showed excellent adhesion to steel.

Synthesis and Characterization of Pressure-Sensitive Adhesives Based on a Naphthyl Curing Agent.

The incorporation of a naphthyl curing agent (NCA) can enhance the thermal stability of pressure-sensitive adhesives (PSAs). In this study, a PSA matrix was synthesized using a solution polymerization process and consisted of butyl acrylate, acrylic acid, and an ethyl acrylate within an acrylic copolymer. Benzoyl peroxide was used as an initiator during the synthesis. To facilitate the UV curing of the solvent-borne PSAs, glycidyl methacrylate was added to introduce unsaturated carbon double bonds. The resulting UV-curable acrylic PSA tapes exhibited longer holding times at high temperatures (150 °C) compared to uncross-linked PSA tapes, without leaving any residues on the substrate surface. The thermal stability of the PSA was further enhanced by adding more NCA and increasing the UV dosage. This may be attributed to the formation of cross-linking networks within the polymer matrix at higher doses. The researchers successfully balanced the adhesion performance and thermal stability by modifying the amount of NCA and UV radiation, despite the peel strength declining and the holding duration shortening. This research also investigated the effects of cross-linking density on gel content, molecular weight, glass transition temperature, and other properties of the PSAs.

UV-Curable Polyurethane Acrylate Pressure-Sensitive Adhesives with High Optical Clarity for Full Lamination of TFT-LCD

Optically clear pressure-sensitive adhesives (PSAs) face the challenges presented by a range of electronic and touch screen applications. Although many efforts have been made to manipulate the optical and adhesion properties of ultraviolet (UV)-curable acrylate-based PSAs, further application and large-scale production are still limited owing to the intrinsically poor processability that stems from the large content of the high-vinyl-equivalent and low-viscosity acrylic monomers. Introducing a low-vinyl-equivalent and high-viscosity polyurethane acrylate (PUA) prepolymer into the formulation is a facile method to solve this issue without sacrificing the transparency. In this study, a series of PUA prepolymers are prepared to construct the model of PUA-co-2-ethylhexyl acrylate (2EHA), denoted as poly(PUA-2EHA). The influence of PUA prepolymer architectures (average functionality and molecular features) on the optical and adhesion properties is elaborately discussed. The chemical cross-linking-induced enhancement of the haze values of PUA-based PSAs is investigated for the first time. Moreover, an improved and uniform bright image display without blemish, which is usually called the Mura defect-free image display in the industrial field, is obtained by using poly(PUA-2EHA) as the optically clear adhesive for full lamination of the thin-film transistor liquid crystal display (TFT-LCD) module. The laminated TFT-LCD module could be disassembled easily without leaving the residue on the screen. These results provide clear design guidelines to regulate the properties of PUA-based PSAs, which are especially valuable for the large-scale industrial production of UV-cured PSAs and facilitate the development of display technologies.

자외선 경화형 감압점착제의 내열성과 점착 물성에 미치는 유/무기 복합가교제의 영향

자외선 경화형 감압점착제의 내열성과 점착 물성에 미치는 유/무기 복합가교제의 영향

Effects of monomer functionality on physical properties of 2-ethylhexyl acrylate based stretchable pressure sensitive adhesives

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.

A crack repair patch based on acrylated epoxidized soybean oil

We present a novel UV-curable patch system that can be used to repair the cracked surfaces of chemical reservoirs. When a crack occurs in a chemical reservoir, the patch can be quickly attached to the damaged area, and then cured with a portable UV source in order to prevent the further spread of toxic chemicals. Crosslinked acrylated epoxidized soy bean oil (AESO) materials with various compositions and crosslinking densities were prepared by reacting AESO with the triethylenetetramine (TETA) crosslinker and tested as UV-curable pressure sensitive adhesives (PSAs). The optimum curing behavior and adhesion performance of the UV-curable patch system were found by using various analytical methods, namely oscillatory rheology, and peel, tack strength, and tensile tests. Finally, an optimized patch was applied to a laboratory scale chemical reservoir in order to assess its performance as a UV-curable crack repairing patch system for the prevention of chemical spills from cracked reservoirs.

Eco-friendly UV-curable pressure sensitive adhesives containing acryloyl derivatives of monosaccharides and their adhesive performances

Two different monosaccharide acrylate monomers were designed and synthesized from glucose and galactose, and were then used to prepare transparent acrylic pressure sensitive adhesives (PSAs) comprised of semi-interpenetrated structured polymer networks. The effects of the monosaccharide architecture in the acrylate monomers on the adhesive performance of the acrylic PSAs were investigated. Prepared UV-curable acrylic PSA syrups were characterized and the optical properties of the acrylic PSAs were also examined. All of the acrylic PSAs exhibited high transparency in the visible wavelength region. With increasing monosaccharide acrylate concentration in the acrylic PSAs, adhesive performances such as the peel strength, cohesion strength, and probe tack were increased. However, there was no difference in their adhesive performances regardless of the different chemical structures of monosaccharide acrylate monomers.

Preparation and adhesion performance of transparent acrylic pressure sensitive adhesives: effects of substituent structure of acrylate monomer

Three different acrylate monomers containing a cyclohexyl moiety were designed and synthesized to prepare transparent acrylic pressure sensitive adhesives (PSAs) comprised of semi-interpenetrated structured polymer networks. The effects of substituent structure in the acrylate monomer on the adhesion performance of the acrylic PSA were investigated. The prepared UV-curable acrylic PSA syrups were characterized and the optical properties of their acrylic PSA film were also examined. The acrylic PSAs exhibited high transparency in the visible wavelength region. Adhesion performance was evaluated using the peel strength, cohesion strength, and probe tack tests. The adhesion properties of the acrylic PSAs depended on the substituent structure in the acrylate monomer.

Preparation of High-Solids UV-Curable Actylate Pressure-Sensitive Adhesive with Low Viscosity for Printed Electronics

If the pressure sensitive adhesive is coated on the back, it can be used for bonding electronic tag, overburden, protective layer, and RFID layer. The acrylate pressure sensitive adhesives are simple and less pollution, so more and more companies pay attention on this kind of binder. Since the thickness of adhesive layer is relatively small, ink-jet printing is now widely used to easily obtain thin layer and design the pressure sensitive adhesive shape of different parts. So how to get superior performance pressure sensitive adhesive which is suitable for ink-jet printing become an urgent problem in printed electronics. The experiment was conducted through solution copolymerization of various vinyl monomers which were selected on the principle of solvent parameter prepared by free radical polymerization. The monomer, initiator mixture solution was dropped in continuous and synchronization process. By regulating the amount of initiator and polymerization temperature, we could effectively reduce the system viscosity and prepare high quality high-solids acrylate UV-curable pressure sensitive adhesives with low viscosity for ink-jet printing. The influence of initiator, solvents, transfer reagents and temperature on the structure and properties of the resin were discussed.

Preparation and properties of UV curable acrylic PSA by vinyl bonded graphene oxide

Acrylic pressure sensitive adhesives (PSAs) with higher thermal stability for thin wafer handling were successfully prepared by forming composite with the graphene oxide (GO) nanoparticles modified to have vinyl groups via subsequent reaction with isophorone diisocyanate and 2-hydroxyethyl methacrylate. The acrylic copolymer was synthesized as a base resin for PSAs by solution radical polymerization of ethyl acrylate, 2-ethylhexyl acrylate, and acrylic acid followed by further modification with GMA to have the vinyl groups available for UV curing. The peel strength of PSA decreased with the increase of gel content which was dependent on both modified GO content and UV dose. Thermal stability of UV-cured PSA was improved noticeably with increasing the modified GO content mainly due to the strong and extensive interfacial bonding formed between the acrylic copolymer matrix and GO fillers

Curing Properties of UV-Cured Pressure Sensitive Adhesives

In this study the effect of trimethylopropane triacrylate (TMPTA) content as a crosslinking agent on curing properties of UV-cured pressure sensitive adhesives (PSAs) was investigated. The curing properties were studied using gel fraction determination, photo-differential scanning calorimetry (photo-DSC) and Fourier transform infraredattenuated total reflection (FTIR-ATR) spectroscopy. Gel fraction sharply increased after expose to UV irradiation and increased with increasing TMPTA content. Moreover, the addition of TMPTA as crosslinking agent induced an earlier onset of auto acceleration and relative concentration of the C=C was not zero because they were trapped in the PSAs network.

Properties of UV-curable solvent-free pressure sensitive adhesive

In this study, the effects of methyl methacrylate (MMA), trimethylolpropane triacrylate (TMPTA), difunctional silicone urethane acrylate oligomer, and UV-dose on the adhesive properties of UV-curable pressure-sensitive adhesives (PSAs) were investigated, for further optimizing the adhesive properties to meet the requirements on high holding power and low peel strength. The results illustrated that increasing the MMA content decreased the peel strength and improved the holding power. The variation of TMPTA content from 1 to 10 wt% significantly enhanced the holding power from 1 h to above 120 h. The gel fraction increased with increasing TMPTA content. This increment was caused by the cross-linking of TMPTA after UV exposure. The peel strength of UV-curable PSAs was reduced to zero when oligomer content was more than 40 wt%, whereas the holding power was significantly enhanced from 5 h to above 120 h as the oligomer content increased up to 70 wt%. When the UV-dose increased, the peel strength decreased and the holding power increased. Therefore, UV-curable PSAs with very low peel strength and high holding power above 120 h were successfully synthesized and they possessed desirable features which could be fabricated to meet the specific requirements for industrial applications.

UV-curable pressure-sensitive adhesives derived from functionalized soybean oils and rosin ester

Functionalized plant oils such as epoxidized soybean oil (ESO) are widely used in plastic industries as additives and are available for more value-added applications. Pressure-sensitive adhesive (PSA) derived from petroleum feedstocks has a huge market ranging from tapes to packaging. Here we show a sustainable PSA derived from ESO/dihydroxyl soybean oil (DSO)/rosin ester (Sylvalite) via UV-initiated copolymerization. The ether crosslinks derived from cationic polymerization of ESO and copolymerization between ESO and DSO (or rosin ester) were demonstrated using 1H NMR, 2D 1H–1H COSY NMR, electrospray ionization mass spectrometry and thermal analyses (differential scanning calorimetry and thermogravimetric analysis). The PSA was formulated by modulating the ratio of ESO/DSO/rosin ester to achieve high performance. At a UV dose of 5.1–5.4 J cm−2 and 0.3–3% (w/w) of a photoinitiator, i.e. [4-(2-hydroxy-1-tetradecyloxy)-phenyl]phenyliodonium hexafluoroantimonate, the PSA at a ratio (by weight) of 1:1:0.7 (ESO/DSO/rosin ester) recorded the highest peel and loop tack strength, which was comparable to a commercial PSA, Scotch Magic Tape, and showed much stronger shear strength (>30 000 min) than the commercial tape (10 000 min). The high-shear rheological behavior and excellent thermal stability of the PSA were also demonstrated. © 2012 Society of Chemical Industry

Adhesion performance of UV-cured semi-IPN structure acrylic pressure sensitive adhesives

UV-curable solvent-free pressure sensitive adhesives (PSAs) are gaining importance in the area of adhesives because of increasing environmental concerns and the goal to reduce volatile organic compounds (VOCs) in work areas and consumption places. These PSAs have advantages such as low emission of VOCs, a solvent-free process, a fast producton rate at ambient temperature and only a modest requirement for operating space. In this study, UV-curable PSAs were investigated by measuring their adhesion performance in terms of probe tack, peel strength, shear adhesion failure temperature (SAFT) and holding power. PSAs were synthesized from 2-ethylhexyl acrylate (2-EHA), acrylic acid (AA) and vinyl acetate (VAc), using variations in AA concentration to control the glass transition temperature (T g) of the prepared PSAs. In addition, two types of trifunctional monomers, trimethylolpropane triacrylate (TMPTA) and trimethylolpropane ethoxylated (6) triacrylate (TMPEOTA), which have different chain lengths, were used to form semi-interpenetrating polymer network (semi-IPN) structures after UV exposure. With increasing AA concentration in the PSAs, both the T g and viscosity increased. Also, probe tack and SAFT increased, but peel strength decreased. After UV irradiation, probe tack decreased, and SAFT and peel strength increased as AA concentration increased in the PSAs. In most cases, cohesive failure changed to interfacial failure after UV exposure. Also, TMPTA increased the cohesion of PSAs; however, TMPEOTA affected the mobility of PSAs due to the different chain lengths of the two types of trifunctional monomer in a different way. The increase of TMPEOTA content diminished the cohesion of PSAs. Consequently, the adhesion performance of the PSAs was closely related to the T g of the PSAs, and the two types of trifunctional monomer showed different adhesion performances.

Some Recent Approaches To the Development of Acrylic Uv Curable Pressure-Sensitive Adhesives

The goal of this program was to utilize ultraviolet radiation (UV) to cure a series of pressure-sensitive adhesives (PSAs) which would provide properties suitable for "light duty" to "permanent" pressure-sensitive applications. A variety of chemical types were represented among the 36 commercial resins which were screened as tackifiers. Utilizing some of the most promising tackifiers, systematic experimental designs were utilized to evaluate formula composition variables and radiation dosage. Trends in performance vs. type and amount of constituents were developed for oligomers, diluent monomers, cross-linking monomers and other additives—along with variations in light intensity and exposure time. Other formulating approaches were also taken, including "one-step" approaches. A number of diverse compositions are presented as a basis for a discussion of formulation parameters.