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.     

Optical properties and UV-curing behaviors of optically clear semi-interpenetrated structured acrylic pressure sensitive adhesives

Acrylic pressure-sensitive adhesives (PSAs) with different side-chain lengths in the co-monomer were synthesized. This study employed semi-interpenetrated structured polymer networks using UV-curing with a hexafunctional monomer, dipentaerythritol hexacrylate (DPHA). The optical properties of the acrylic PSAs were examined by UV-visible spectroscopy and a prism coupler. ARES was used to characterize the viscoelastic properties of the acrylic PSAs. Adhesion performance was conducted by the peel strength and probe tack tests. Also UV-curing behavior of the acrylic PSAs was investigated by FTIR.     

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.     

Adhesion Performance and Thermal Stability of Fluorinated PSAs as a Crosslinking System

The use of pressure sensitive adhesives (PSAs) is becoming increasingly popular in many industrial fields. In the automobile industry the main reasons for using PSAs are that they reduce the overall weight of the vehicles and because they are easy to use. However, in the case of acrylic PSAs, the non-crosslinked linear chains results in low thermal stability. In this study, a fluorinated acrylic pressure sensitive adhesive was synthesized under UV irradiation and crosslinking was applied to the linear chain of acrylic PSAs to improve the thermal stability. The adhesion performance was evaluated by analyzing the peel strength, probe tack and shear adhesion failure temperature (SAFT) as a function of the type of crosslinking system. In particular, the peel strength and probe tack were measured at 25, 50 and 80°C. The viscoelastic properties, which were measured using an advanced rheometric expansion system (ARES), revealed a proper balance between the thermal stability and adhesion performance.     

Sustainable isosorbide‐based transparent pressure‐sensitive adhesives for optically clear adhesive and their adhesion performance

A biomass‐based isosorbide acrylate (ISA) was synthesized in a one‐pot reaction at low temperature with a quite slow dropwise technique using a syringe pump. Using the ISA monomer, UV‐cured transparent acrylic pressure‐sensitive adhesives (PSAs) composed of semi‐interpenetrating networks were prepared. The effect of ISA on the adhesion performance of the resulting acrylic PSAs was investigated by changing the ISA content, while fixing the mole ratio between 2‐ethylhexyl acrylate and 2‐hydroxyethyl acrylate in the PSAs. The prepared acrylic PSAs, with ISA content ranging from 3.2 to 14.3 mol%, were evaluated in terms of 180° peel strength, probe tack, static shear testing and optical properties. Increasing the ISA content in the acrylic PSAs improved the adhesion properties, such as 180° peel strength (0.25–0.32 N/25 mm), shear holding power (0.086–0.023 mm) and probe tack (1.21–2.26 N). Dynamic mechanical analysis indicated that ISA is a good candidate monomer, playing the role of adhesion promoter and hard monomer in the acrylic PSAs. © 2017 Society of Chemical Industry     

环保型低剥离力压敏胶的研制

采用半连续乳液聚合法制备了一种丙烯酸类水基型低剥离力压敏胶。主要考察了甲基丙烯酸(MAA)等功能单体和外加交联剂对产物性能的影响。实验表明,随MAA等亲水单体用量的增多,乳液粘度会增大,而引入交联单体在实验范围内可显著降低剥离强度。功能单体用量有一合适范围。选用较高反应活性的氨基树脂作交联剂,可改善耐温性,保持初粘力,得到综合性能较好的低剥离力压敏胶。     

New Developments in the Area of Solvent-Borne Acrylic Pressure-Sensitive Adhesives

Since their introduction half a century ago, acrylic pressure-sensitive adhesives have been successfully applied in many fields. In the last fifty years or so, acrylic pressure-sensitive adhesives (PSAs) have made tremendous strides from what was virtually a black art to what is now a sophisticated science. So much so that larger manufacturers of pressure-sensitive adhesives and even their polymer suppliers now use very expensive equipment to study pressure-sensitive adhesive behavior. The three properties which are useful in characterizing the nature of pressure-sensitive adhesives are tack, peel (adhesion) and shear (cohesion). The first measures the adhesive's ability to adhere quickly, the second its ability to resist removal by peeling, and the third its ability to hold in position when shear forces are exerted. The performances of pressure-sensitive adhesives, such as tack, peel and shear, based on polyacrylates synthesized through co-polymerization of acrylate monomers and formulated in organic solvents mixtures are, to a large degree, determined by the molecular weight of acrylic copolymer, polymerization method and especially by the type and quantity of the crosslinking agent added to the PSA. Newly developed solvent-borne PSAs are used in protective foils, removable and repositionable self-adhesive products, water-soluble PSAs and water-dispersible self-adhesive products, photoreactive UV-crosslinkable self-adhesive tapes, and dual-crosslinkable PSAs for self-adhesive tapes with post-crosslinking potential characterized by enhanced cohesion at higher temperatures. The mentioned water-soluble PSAs, water-dispersible self-adhesive products and photoreactive UV-crosslinkable self-adhesives are synthesized in organic solvents as solvent-borne acrylic PSAs.     

Fabrication of optically clear acrylic pressure–sensitive adhesive by photo-polymerization: UV-curing behavior,adhesion performance,and optical properties

Acrylic pressure–sensitive adhesives (PSAs) with 2-phenoxy ethyl acrylate (PEA) were polymerized using UV-curing technology. This study examined the effects of PEA content and UV dose. The photo-polymerization behavior of the pre-polymer was examined by viscosity measurements, real-time Fourier transform infrared spectroscopy, and photo-differential scanning calorimetry. The curing behaviors of the acrylic PSAs were investigated by shrinkage test, a modular advanced rheometer system, and gel content. differential scanning calorimetry and Advanced Rheometric Expansion System were used to characterize the acrylic PSAs. Adhesion performances were measured by probe tack, peel strength, and shear adhesion failure temperature. The optical properties of acrylic PSAs were examined by UV–visible spectroscopy and prism coupler. The PEA content had a larger effect on improving the optical properties, than did the UV dose. The transmittances of the acrylic PSAs with <75% PEA were >95%. The refractive indices of the acrylic PSAs increased with increasing PEA content, due to its high refractive index, >1.5, which affected the overall refractive indices, particularly in the visible region.     

Improvement in wettability of pressure‐sensitive adhesive on silicon wafer using crosslinking agent with siloxane groups

Acrylic copolymers are prepared by radical polymerization of 2‐ethylhexyl acrylate, ethyl acrylate, and acrylic acid followed by crosslinking to manufacture the pressure‐sensitive adhesives (PSAs) for silicon wafer protection. Both higher reliability and wettability are required for the protective acrylic PSAs in the semiconductor processing applications. The siloxane linkages are introduced in the acrylic PSAs via crosslinking with siloxane‐containing crosslinking agent to modify the thermal and wetting properties of PSAs efficiently. The more efficient formation of crosslinked network structure was achieved with higher content of tetra‐functional crosslinking agent, and the surface energy of PSAs decreased significantly with increasing the content of siloxane linkage resulting in the improved areal wetting rate. The thermal stability of PSAs was also improved significantly by incorporation of siloxane linkages. The adhesion properties such as peel strength and probe tack of acrylic PSAs decreased significantly by increasing the content of either crosslinking agent or siloxane linkage. The acrylic PSA with siloxane group showed both satisfactory wetting and clean debonding properties for the optimal protection of thin silicon wafers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Optical properties and adhesion performance of acrylic PSAs; influence of functionalized monomer and curing agent

Acrylic pressure–sensitive adhesives (PSAs) were synthesized by solution polymerization using zirconium carboxyethyl acrylate (ZrCEA) with methyl aziridine derivatives (MAZ) as a curing agent. The acrylic PSAs were characterized by Fourier transform-infrared spectroscopy and gel contents. The viscoelastic properties of the acrylic PSAs were determined using an advanced rheometric expansion system. The adhesion performance of the acrylic PSAs was determined by measuring the probe tack, peel strength, shear adhesion failure temperature, and holding power. The optical properties of the acrylic PSAs were evaluated by the transmittance and refractive index. The results show that the adhesion performance and optical properties of the acrylic PSAs are influenced by the ZrCEA and MAZ content.     

Wettability and adhesion characteristics of photo-crosslinkable adhesives for thin silicon wafer

Acrylic pressure-sensitive adhesives (PSAs) have many applications in the processes of electronic industry. As the silicon wafers become thinner, the acrylic PSAs need to show proper adhesion and better wettability on the thin wafer. The acrylic copolymers were synthesized by solution polymerization of 2-ethylhexyl acrylate, ethyl acrylate, and acrylic acid with AIBN as an initiator. Photo-crosslinkable PSAs were synthesized by reaction of the acrylic copolymers with glycidyl methacrylate (GMA) and lauryl glycidyl ether (LGE). The adhesion performance of acrylic photo-crosslinkable PSAs was investigated based on wettability, probe tack, peel strength, cohesiveness, and viscoelastic properties. The adhesion characteristics varied significantly depending on the ratio of GMA to LGE in the photo-crosslinkable PSAs.     

Optical properties and adhesion performance of optically clear acrylic pressure sensitive adhesives using chelate metal acetylacetonate

Optically clear acrylic pressure-sensitive adhesives (PSAs) with different co-monomers were synthesized. This study employed metal chelate aluminum acetylacetonate and zirconium acetylacetonate as curing agents. The optical properties of the acrylic PSAs were examined by UV–visible spectroscopy and a prism coupler. In addition, the adhesion performance was obtained by assessing the peel strength, the tack, and the shear adhesion failure temperature. The decrease in the adhesion performance may be related to a higher crosslinking density, which also resulted in a higher gel content.     

Effect of side chain on wettability and adhesion performance of acrylic pressure-sensitive adhesives on thin silicon wafer

Acrylic pressure-sensitive adhesives (PSAs) need to show proper adhesion and improved wettability on the silicon wafer as the wafer becomes thinner. The acrylic copolymers were synthesized by solution radical polymerization of 2-ethylhexyl acrylate, ethyl acrylate, and acrylic acid with AIBN as an initiator. Adhesion performance and wettability of acrylic PSAs were studied depending on the content of lauryl side chains and the degree of crosslinking. The introduction of lauryl side chain was characterized by Fourier transform infrared spectroscopy. The adhesion performance of acrylic PSAs having lauryl side chain was investigated using contact angle, wettability, probe tack, peel strength, and cohesiveness tests. The wettability of acrylic PSAs was improved significantly with increasing the content of lauryl side chain.     

Novel pyridinium photoinitiators and their applications for the ultraviolet crosslinking of acrylic pressure‐sensitive adhesives

The demand for ultraviolet (UV)‐crosslinkable pressure‐sensitive adhesives (PSAs) has rapidly been increasing. A variety of different PSAs containing new photoreactive pyridinium derivatives have been evaluated for their effectiveness in improving adhesion and cohesion in UV‐crosslinkable PSAs. PSAs have been evaluated with respect to the tack, peel adhesion, and shear strength. This article summarizes the breakthrough technology used to achieve better performances in UV‐crosslinkable acrylic PSAs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

2-Ethylhexyl acrylate/4-acryloyloxy benzophenone copolymers as UV-crosslinkable pressure-sensitive adhesives

Summary It has been previously shown that copolymer of 2-ethylhexyl acrylate with an 4-acryloyloxy benzophenone can be used as PSA. This paper presents synthesis and application of solvent-based polymer system for the preparation of acrylic pressure-sensitive adhesives (PSA). 2-Ethylhexyl acrylate benzophenone copolymers, having molecular mass in the range of 120 000 to 380 000 Dalton were prepared by free-radical solution polymerization. These copolymers were tacky but possessed insufficient cohesive strength after UV-crosslinking to be useful as PSAs. These copolymers resulted in materials having a balance of cohesive and adhesive characteristics required of a good PSA. Some of the parameters affecting the pressure-sensitive adhesive properties of the copolymer are: amount of the 4-acryloyloxy, molecular mass of the polymeric components, UV-reactivity and such properties like tack, peel adhesion and cohesion.     

Novel acrylic pressure-sensitive adhesive (PSA) containing silver particles

Acrylic pressure-sensitive adhesives (PSAs) are generally considered as nonelectrically conductive materials. The electrical conductivity is incorporated into acrylic polymer after blending with electrical conductive additives like silver particles. After the addition of electrically conductive silver filler, the main and typical properties of PSAs such as tack, peel adhesion, and shear strength will decline. This study is the first trial which reveals that the acrylic self-adhesive basis must be synthesized with ameliorated initial performances like high tack and excellent adhesion. Currently, the electrically conductive solvent-borne acrylic PSA containing silver fillers are not commercially available on the market. They are promising materials which can be applied for the manufacturing of diverse technical or medical high performance self-adhesive products, such as broadest line of special electrically conductive sensitive tapes.     

Effect of organoclay and chain-transfer agent on molecular parameters and adhesion performance of emulsion pressure-sensitive adhesives

Organoclay-reinforced pressure-sensitive adhesives (PSAs) based on poly(butyl acrylate-co-vinyl acetate-co-acrylic acid) were prepared in the presence of an organically modified montmorillonite, that is, Cloisite15A (C15A), via in situ batch emulsion polymerization. The effect of C15A and chain transfer agent (CTA) level on the molecular parameters and adhesion properties of resulting reinforced PSA were investigated. Small-angle X-ray scattering (SAXS), gel permeation chromatography (GPC), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC) were used to determine the characteristics of the neat and reinforced PSAs. The adhesion test results showed that the incorporation of C15A up to 1 wt% considerably increased the peel strength, shear and probe tack due to increasing the entanglement density of the PSA copolymer, while further increase lowered the peal and tack properties. Interestingly, the addition of 0.25 wt% CTA in the presence of 1 wt% C15A silicate layers resulted in PSA nanocomposite with the highest peal strength and probe tack. Although the CTA remarkably decreased the shear resistance of the neat PSA, the existence of C15A layers or tactoids in the reinforced PSAs decreased the rate of shear resistance decay due to the good interaction between the C15A and adhesive copolymer chains.     

Effect of crosslinking density on adhesion performance and flexibility properties of acrylic pressure sensitive adhesives for flexible display applications

The use of acrylic pressure sensitive adhesives (PSAs) in flexible displays involves their attachment to each layered device. Due to the high industrial demand of flexible displays, acrylic PSAs must necessarily exhibit high flexibility. In this study, the effect of the crosslinking density of acrylic PSAs on their adhesion and flexibility properties has been investigated by incorporating a diisocyanate crosslinking agent into the PSA structure. As the content of the crosslinking agent increased, the measured peel strength and tack of the synthesized PSAs decreased, while the maximum value of the lap shear stress increased. In addition, the maximum stress and shear strain determined for the crosslinked PSA specimens decreased with an increase in the crosslinking agent concentration (although, the stress measured at low strain values was initially increasing until the crosslinking agent content reached 1 phr). The results of stress relaxation testing showed a stress increase at specified strain levels with an increase in the crosslinking agent content up to 0.5 phr, while the results of creep testing revealed that the measured strain was inversely proportional to the degree of elastic recovery. The obtained data indicate that crosslinking generally improves the PSA properties related to their use in flexible display applications; however, very high crosslinking densities produce mostly a negative effect on the PSA flexibility and adhesion characteristics.     

Multifunctional propyleneimines-new generation of crosslinkers for solvent-based pressure-sensitive adhesives

This article describes work with the goal of crosslinking pressure sensitive acrylic adhesives (PSA) and a new generation of crosslinkers based on multifunctional propyleneimine derivates. Crosslinking of PSA is an established technology used in many industrial manufacturing processes. New applications and technical specifications stimulate the continuous development of new crosslinking agents with very interesting properties. These new crosslinkers influence physico-mechanical properties of acrylic PSA such as tack, peel resistance (adhesion) and shear strength (cohesion). The weak point of propyleneimine crosslinkers is their very short potlife.     

Incorporation of cellulose nanocrystals and reactive surfactants for improved pressure-sensitive adhesive performance

Pressure-sensitive adhesives (PSAs), which achieve instantaneous adhesion with the application of light pressure, are used in a large range of commodity applications. In this work, PSAs enriched with cellulose nanocrystals (CNCs) and stabilized with a reactive surfactant (Hitenol AR-1025, AR) were synthesized via in situ emulsion polymerization. Incorporation of CNCs into AR-stabilized PSAs lead to improvements of peel strength, shear strength, and loop tack with significant increases observed at a CNC concentration of 0.75 parts per hundred monomer (phm). A comparative investigation of PSAs stabilized with reactive (AR) and non-reactive (sodium dodecyl sulfate) surfactant revealed that the enhanced performance can be attributed to the synergistic combination of CNCs and reactive surfactant, as only modest improvements can be attributed to surfactant type. In contrast to previous studies that report a trade-off in adhesive properties, we present a well-rounded PSA with exceptional peel strength, shear strength, and loop tack.