Application of selected 2-methylbenzothiazoles AS cationic photoreactive crosslinkers for pressure-sensitive adhesives based on acrylics

Since their introduction half a century ago, acrylic pressure-sensitive adhesives have been successfully applied in many fields. They are used in self-adhesive tapes, label signs, marking films and protective films as well as in medical pharmaceutical applications for plaster, in dermal dosage systems and in a wide range of biomedical electrodes. In the last 15 years or so, the UV technology, especially UV-crosslinking, is well established in the market and allows the production of UV-crosslinkable pressure-sensitive adhesives (PSA) based on acrylics with interesting performance. So much so that the larger manufacturers of pressure-sensitive adhesive materials and their suppliers now use very expensive equipment to study pressure-sensitive adhesive behavior: tack, peel adhesion and shear strength. The balance between adhesive and cohesive strength after the crosslinking process is very important and critical for properties of acrylic PSA in form of self-adhesive films. In this work the cationic UV-crosslinking of acrylic PSA containing epoxy groups in their structure and additionally cationic photoinitiators based on 2-methylbenzothiazoles as photoreactive crosslinkers have been investigated using UV-lamp as ultraviolet sources. The investigated acrylic PSA were synthesized from 80 wt% of butyl acrylate, and 20 wt% of glycidyl methacrylate. The use of selected photoreactive crosslinkers: 1,5-bis[N,N׳-(2-methylbenzothiazolium)]pentane diiodide and 1,10-bis[N,N׳-(2-methylbenzothiazolium)]decane diiodide allows manufacturing of high quality PSA materials with interesting properties, such as high tack, high peel adhesion, and excellent shear strength.     

The effects of graphene on the properties of acrylic pressure-sensitive adhesive

Graphene was examined as a conductive filler to reduce the surface resistivity of an acrylic pressure-sensitive adhesive (PSA). The graphene effectively reduced the surface resistivity; however it also reduced the peel strength of the PSA. This peel strength reduction could be minimized when the graphene was not mixed homogeneously but embedded in the PSA as a separate layer. In addition, the surface resistivity was reduced much more effectively. Typically, the surface resistivity reduced to one-millionth, when 1 part of graphene was imbedded as a separate layer in 100 parts of PSA, compared to that of homogeneously dispersed composite.     

Photocrosslinking of solvent-based acrylic pressure-sensitive adhesives (PSA) by the use of selected photoinitiators type I

This study investigated the photocrosslinking of solvent-based acrylic pressure-sensitive adhesives (PSA) containing selected photoinitiators type I, known as α-cleavage photoinitiators. Photocrosslinking of PSA, especially of acrylic PSA, is well established crosslinking process using the UV radiation technology. UV-initiated crosslinking of acrylic PSA allows the synthesis of the wide range of UV-crosslinkable PSA with the interesting features. Especially, the important balances of properties such as adhesive and cohesive strength which are typically critical for the application performance can be achieved by this technology. The selection of suitable photoinitiator plays an important role to obtain the optimum properties of acrylic PSA including tack, peel adhesion, and shear strength. In this study, the investigations on different saturated conventional photoinitiators of type I for solvent-based PSA were carried out. The effects of photoinitiator concentration, UV crosslinking time and UV dose on the tack, peel strength, and shear strength were explored in detail for guiding the choice of photoinitiators to fabricate advanced PSA for industrial usage.     

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.     

UV-initiated crosslinking of photoreactive acrylic pressure-sensitive adhesives using excimer-laser

UV-initiated crosslinking technology is well established in the market and allows the production of a wide range of ultraviolet (UV)-crosslinkable pressure-sensitive adhesives (PSA) with interesting features. The balance between such properties as adhesive and cohesive strengths within the crosslinked self-adhesive coatings is critical for their performance. The UV crosslinking of acrylic PSA, especially for following properties: tack, peel adhesion, and shear strength of self-adhesive polymer layers, has been investigated using UV excimer-laser and UV lamp as UV sources. It was observed that after UV crosslinking of acrylic PSA using excimer-laser in comparison with typical UV lamp, high-quality PSA products with excellent properties, such as tack, peel adhesion, shear strength, and shrinkage were received.     

Thermally conductive adhesives from covalent-bonding of reduced graphene oxide to acrylic copolymer

This work reports about the enhancement of the thermal conductivity of an acrylic pressure-sensitive adhesive (PSA) with the incorporation of functionalized and reduced graphene oxide (frGO) sheet in the composition. Bifunctional isocyanatoethylmetharcylate (IEMA) was intercalated (so-called ‘functionalization’) to the GO surface mainly at its –COOH sites. The remaining oxygenated groups on the GO surface were reduced by dimethyl hydrazine. The frGO was successfully incorporated into PSA matrix through in-situ polymerization of acrylic monomers and subsequently crosslinked under UV radiation. The conductivity and the peel strength of the PSA were studied as a function of filler content, filler modification (functionalization and/or reduction), UV-radiation dosage and mode of filler insertion (through in-situ polymerization or mechanical mixing). frGO/PSA showed much better properties than the PSA system with bare or IEMA-functionalized unreduced GO. In-situ polymerization was found to be more effective method for frGO insertion. Within the range of filler content (0.0–1.0) wt% and UV-radiation dosages of (400–3000) mJcm^?2, the thermal conductivity and peel strength of the acrylic PSA-system under investigation varied in the range of 0.17–1.03 Wm^?1K^?1 and 2831–299 g_f/25 mm. This is the first report on ‘reduced GO covalently bonded to polymer chain in an adhesive-composition’ providing novel idea to make PSA-system with balanced thermal conductivity and peel strength with perspective for application in miniature electronic industries.     

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.     

Behavior of Pressure-Sensitive Adhesives Filled with Metallized Inorganic Particles

The electrically conductive pressure-sensitive composite adhesives based on acrylic polymer and silver-coated inorganic particles have been investigated in this article. The electrical conductivity of the pressure-sensitive adhesives containing silver coated spherical inorganic particles is lower at the same concentration of the filler in comparison with silver coated inorganic fibers, the strength of adhesive joint to aluminum being higher in the case of the pressure-sensitive adhesive containing silver-coated inorganic fibers. After the thermal treatment the strength of adhesive joint to aluminum of electrically conductive pressure sensitive adhesives increases significantly. The suitable concentration proposition of the silver-coated inorganic filler in the pressure-sensitive adhesive requires a compromise solution of the problem taking into account the ultimate adhesive and electrical properties of the investigated pressure-sensitive adhesives composites.     

The effects of substrate surface properties on tack performance of acrylic Pressure-Sensitive Adhesives (PSAs)

The effects of substrate surface free energy (SFE) and substrate roughness on tack performance of adhesive tapes containing synthesized model acrylic pressure-sensitive adhesive (PSA) have been investigated. In order to study the influence of substrate SFE on tack the adherents with the same surface roughness (expressed by selected amplitude parameters) were used: PTFE, PP, PE, ABS, PC, PMMA, stainless steel and glass. The relationship between substrate roughness and tack was investigated using two polypropylene plates (PP and PP_rough) characterized as having the same wettability (SFE). For tack determination the most common method in the PSA tapes industry was employed (loop tack test). The conducted experiments showed that substrate SFE is a crucial factor governing tack properties of acrylic PSAs. In general, a larger difference between the SFE values of the substrate and adhesive were correlated with greater tack values. The dependence of tack and SFE was significantly influenced by crosslinking degree and layer coat weight of model acrylic PSA. The experiments carried out in the second part of the study revealed that the adhesive׳s viscoelastic properties control the tack properties on rough substrates, however, the final tack performance was found to be strongly affected by the level of substrate roughness and PSA thickness.     

How does the surface free energy influence the tack of acrylic pressure-sensitive adhesives (PSAs)?

This article describes a comparative study of the tack properties of a model acrylic pressure-sensitive adhesive (PSA) crosslinked using aluminum acetylacetonate on several substrates, including stainless steel, glass, polyethylene, polypropylene, polytetrafluoroethylene, polycarbonate, and poly(methyl methacrylate). The tack measurements were conducted using a technique commonly used to measure the tack of an adhesive tape in the PSA industries. The surface free energy (SFE) values of the materials were evaluated using the Owens–Wendt and van Oss–Chaudhury–Good methods. The experiments showed a clear relationship between the SFE of the substrate and the tack of the model acrylic PSA. In general, larger differences between the SFE values of the substrate and adhesive (Δ_SFE) were correlated with greater tack values. The tack of the model acrylic PSA was found to be optimal over the Δ_SFE range of 7.0–13.1 mJ/m². The trend in the tack as a function of the SFE difference was attributed to the quantity of energy dissipated at the jointed points during the separation stage in the loop tack test.     

Using of carbon nanotubes and nano carbon black for electrical conductivity adjustment of pressure-sensitive adhesives

Electrical conductive pressure-sensitive adhesives (PSAs) are not commercially available on the market. The development of these PSAs requires special suitable self-adhesive polymers and their modification through adding of electrical conductive fillers. From the evaluated PSAs the best performances were achieved using acrylic PSAs. Common fillers for electrical conductivity are carbon nano-fillers, metallic powders like copper, aluminum, nickel, silver or gold. Acrylic PSA containing electrical conductivity fillers are applied for the manufacturing of diverse technical self-adhesive products, such as broadest line of electrically conductive sensitive double-sided, one-sided and carrier-free tapes. After addition of electrical conductive fillers the main typical properties for pressure-sensitive adhesives like tack and peel adhesion are deteriorated. In the last time the research and development on the area of nano carbon black or nanotubes as electrical conductive fillers is observed.     

Biodegradable self-adhesive tapes with starch carrier

The disposed pressure-sensitive adhesive (PSA) tape widely used in daily life has been contaminating the environment and producing the vastly non-degradable trash. In this pioneering work, the advanced biodegradable pressure-sensitive double-coated tape containing starch carrier and water-soluble partially degradable modified pressure sensitive adhesive is architecturally designed and fabricated. The results have illustrated the excellent tack and peel adhesion of these newly constructed biodegradable self-adhesive tapes, and high thermal shear strength. Most importantly, the complete biodegradability of starch carrier and partially biodegradability of modified acrylic pressure-sensitive adhesives (PSA) have been confirmed experimentally. This environmentally friendly technology based on the starch resource utilization and novel water-soluble PSA will have great potentials for diverse applications such as the paper industry for manufacturing of ecological biodegradable product, the production of water-soluble biodegradable labels, medical tapes and biomedical electrodes.     

保护膜用高剥离力丙烯酸酯乳液压敏胶的研制

以丙烯酸丁酯（BA）、丙烯酸酯（2-EHA）、甲基丙烯酸甲酯（MMA）、苯乙烯（St）、丙烯酸（AA）、丙烯酸羟丙酯（HPA）为原料进行乳液共聚,合成了保护膜用丙烯酸酯乳液压敏胶,讨论了各种单体、乳化剂、交联剂对压敏胶性能的影响。结果表明,该压敏胶具有较高的剥离强度和初黏力,同时具有较好的耐高温高湿老化性能。     

复合填料/聚丙烯酸酯导电压敏胶的制备与性能

针对导电胶黏剂（ECA）在实用中所遇到填料组分单一、易团聚、对基体力学性能影响较大等问题,本文利用不同组分填料间的架桥、插层等“协同”效应,将一定比例的碳黑（CB）、碳纤维（CF）、碳纳米管（CNTs）、纳米石墨微片（NanoG）复合作为导电填料加入到聚丙烯酸酯压敏胶（PSA）中,采用溶液共混法超声分散,得到填料添加量小、导电性能和力学性能良好的导电PSA。运用多种检测手段对导电PSA的电学性质、微观结构、热稳定性和力学性能进行了分析。结果表明,复合填料组成为CF 3%、NanoG 5%、CNTs 5%（均为质量分数）时,导电PSA的电导率达到3.0×10?2S/cm,180°剥离强度为0.38kN/m。     

Miscibility and fracture energy of probe tack for acrylic pressure-sensitive adhesives: acrylic copolymer/tackifier resin systems

The relationship between the miscibility of acrylic pressure-sensitive adhesive (PSA) and the fracture energy (W) (Jm⁻²) of the probe tack was investigated, wherein the master curve of W was compared with that of the maximum force (σ_max) (gf) of the probe tack. It was ascertained that W of acrylic PSA was closely related to the miscibility between the components (acrylic copolymer and tackifier resin). In the case of the miscible blend system, the master curve of W shifted toward the lower rate side and, at the same time, the magnitude decreased as the tackifier resin content increased. The degree of the shift of W was extremely smaller than that of σ_max. In the case of the immiscible blend system, the master curve of W remarkably decreased as the tackifier resin content increased, which suggests the fact that W of the PSA depended on the dynamic mechanical properties of the matrix phase and that the resin-rich phase acted as a kind of filler, thus reducing the practical performance. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 581–587, 1998     

Stress Relaxation During Bond Formation and Adhesion of Pressure-Sensitive Adhesives

Relaxation properties and adhesion of pressure-sensitive adhesives (PSAs) have been studied with the Probe Tack method under the conditions corresponding to the adhesive bond formation. Typical representatives of various PSA classes are examined: adhesives based on the styrene-isoprene-styrene (SIS) block copolymer, polyisobutylene of two molecular weights, acrylic and silicone PSAs. By comparison of the adhesive and relaxation behaviors of different PSAs it has been established that the PSA relaxation contributes appreciably to the strength of the adhesive bond and underlies the impact of contact time on adhesion. Direct correlation has been established between the compressive stress relaxation in the course of bond formation and the mechanism of debonding. All the examined PSAs can be classified into two groups: 1) the fluid-like PSAs that are capable of relaxing fully under compression (PIB, silicone adhesives) and 2) the PSAs, which reveal a residual unrelaxed stress. Physically crosslinked SIS and chemically crosslinked acrylic adhesives exemplify the PSAs of the second group. The occurrence of two peaks on the debonding stress–strain curves is typical of the PSAs of the second group. High adhesive strength requires the contribution of the longer relaxation times that vary for different PSAs in the range from 150 to 800 s. Minimum values of the longer relaxation times are featured for fluid adhesives, whereas the maximum values are found for crosslinked, network, and entangled adhesives. The adhesive strength achieves its maximum when the slow relaxation processes become dominating. Relative contributions of viscous and elastic deformations to relaxation properties of PSAs are assessed in terms of the Deborah number.     

Stress Relaxation During Bond Formation and Adhesion of Pressure-Sensitive Adhesives

Relaxation properties and adhesion of pressure-sensitive adhesives (PSAs) have been studied with the Probe Tack method under the conditions corresponding to the adhesive bond formation. Typical representatives of various PSA classes are examined: adhesives based on the styrene-isoprene-styrene (SIS) block copolymer, polyisobutylene of two molecular weights, acrylic and silicone PSAs. By comparison of the adhesive and relaxation behaviors of different PSAs it has been established that the PSA relaxation contributes appreciably to the strength of the adhesive bond and underlies the impact of contact time on adhesion. Direct correlation has been established between the compressive stress relaxation in the course of bond formation and the mechanism of debonding. All the examined PSAs can be classified into two groups: 1) the fluid-like PSAs that are capable of relaxing fully under compression (PIB, silicone adhesives) and 2) the PSAs, which reveal a residual unrelaxed stress. Physically crosslinked SIS and chemically crosslinked acrylic adhesives exemplify the PSAs of the second group. The occurrence of two peaks on the debonding stress-strain curves is typical of the PSAs of the second group. High adhesive strength requires the contribution of the longer relaxation times that vary for different PSAs in the range from 150 to 800 s. Minimum values of the longer relaxation times are featured for fluid adhesives, whereas the maximum values are found for crosslinked, network, and entangled adhesives. The adhesive strength achieves its maximum when the slow relaxation processes become dominating. Relative contributions of viscous and elastic deformations to relaxation properties of PSAs are assessed in terms of the Deborah number.     

Influence of selected photoinitiators type II on tack,peel adhesion,and shear strength of UV-crosslinked solvent-borne acrylic pressure-sensitive adhesives used for medical applications

This article describes the photoreactive UV-crosslinkable solvent-borne acrylic pressure-sensitive adhesives (PSA) containing unsaturated copolymerizable photoinitiators and their synthesis. The solvent-borne acrylic PSA were synthesized in ethyl acetate as a solvent, and the copolymerizable photoinitiators type II, known as hydrogen abstractors, were incorporated into acrylic polymer chain during conducted radical polymerization process. The synthesized solvent-borne acrylic PSA containing different unsaturated photoinitiators were investigated to evaluate their relevant and significant properties such as tack, peel adhesion, and shear strength after UV exposure.     

链转移剂与极性单体对丙烯酸酯乳液压敏胶性能的影响

研究了链转移剂硫醇及极性单体丙烯酸(AA)、丙烯酸-β-羟丙酯(β-HPA)对丙烯酸酯乳液压敏胶性能的影响。同时还探讨了极性单体不同加入方式对压敏胶性能的影响。结果表明:适量分批加入硫醇、丙烯酸和丙烯酸-β-羟丙酯可显著提高压敏胶的初粘性、持粘性和剥离强度。     

Preparation of an adhesive in emulsion for maxillofacial prosthetic

Maxillofacial prostheses is a dental medicine specialty aimed at restoring anatomical facial defects caused by cancer, trauma or congenital malformations through an artificial device, which is commonly attached to the skin with the help of an adhesive. The purpose of our research was to develop a pressure-sensitive adhesive (PSA) based on acrylic monomers, characterizing and determining its drying kinetics, that is to say the time it takes to lose 50 to 90% of its moisture. The adhesive synthesis was realized by means of emulsion polymerization; the composition of formulations was: (AA-MMA-EA) and (AA-MMA-2EHA) with different molar ratios. The formulation based on (AA-MMA-2EHA) with 50 w% of solids, presented good adhesive properties such as tack, bond strength, and short drying time. We propose this formulation as a PSA, because it offers an alternative for systemically compromised patients, by less irritation compared to organic solvent-based adhesives.