Effects of surface modification by oxygen plasma on peel adhesion of pressure‐sensitive adhesive tapes

Surfaces of poly(isobutylene) (PIB) and poly(butylacrylate) (PBA) pressure‐sensitive adhesive tapes were treated by oxygen plasma, and effects of surface modification on their adhesive behavior were investigated from the viewpoint of peel adhesion. The peel adhesion between PIB and PBA pressure‐sensitive adhesive tapes and stainless steel has been improved by the oxygen plasma treatment. The surface‐modification layer was formed on PIB and PBA pressure‐sensitive adhesive surfaces by the oxygen plasma treatment. The oxygen plasma treatment led to the formation of functional groups such as various carbonyl groups. The treated layer was restricted to the topmost layer (50–300 nm) from the surface. The GPC curves of the oxygen plasma‐treated PBA adhesive were less changed. Although a degradation product of 1–3% was formed in the process of the oxygen plasma treatment of the PIB adhesive. There are differences in the oxygen plasma treatment between the PIB and PBA adhesives. A close relationship was recognized between the amount of carbonyl groups and peel adhesion. Therefore, the carbonyl groups formed on the PIB and PBA adhesive surfaces may be a main factor to improve the peel adhesion between the PIB and PBA adhesive and stainless steel. The peel adhesion could be controlled by changing the carbonyl concentration on the PIB and PBA adhesive surfaces. We speculate that the carbonyl groups on the PIB and PBA adhesive surface might provide an interaction with a stainless steel surface. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1392–1401, 2000     

Free volume,adhesion, and viscoelastic properties of model nanostructured pressure‐sensitive adhesive based on stoichiometric complex of poly(N‐vinyl pyrrolidone) and poly(ethylene glycol) of disparate chain lengths

Positron annihilation lifetime spectroscopy was used to characterize the size and content of subnanoscopic free volume in a model pressure‐sensitive adhesive based on a stoichiometric hydrogen‐bonded network complex of poly(N‐vinyl pyrrolidone) (PVP) and oligomeric poly(ethylene glycol) (PEG). Adhesive properties were examined with peel and probe tack tests, and mechanical properties were studied with tensile test. Nonequimolar stoichiometry and the structure of PVP–PEG model pressure‐sensitive adhesive blends were found to be determined by the length of PEG short chains. The size and number density of free volume domains in the PVP–PEG blends were determined as functions of blend composition and relative humidity of the surrounding atmosphere, which controls the amount of absorbed water. Correlating the free volume, adhesion behaviors, and tensile properties of the blends, the range of free volume favoring pressure‐sensitive adhesion in examined compositions was established. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improvement in mechanical properties and thermal stability of solvent‐based pressure‐sensitive adhesives based on triazine heterocyclic monomer

A heat‐resistance monomer denoted as triazine heterocyclic compound (TGIC‐AA) was synthesized and applied into improving the thermal stability of solvent‐based acrylic pressure sensitive adhesives (PSAs) through copolymerization. The modified acrylic PSAs tapes possessed longer holding time at temperature up to 150°C and no large areas of residues could be seen when peeled off on the substrate while the temperature of test was cooled down to room temperature. The thermal stability could be significantly enhanced in PSAs as the content of triazine heterocyclic compounds increased due to the extensive crosslinking networks. This indicated a worthy method to prepared heat resistant acrylic PSAs. An obvious reduction in peel adhesion occurred at the content of crosslinkers range 5 wt %‐7 wt %, while beyond 7 wt % adhesion failure occurred. The influences of crosslinking density on the molecular weight, glass transition temperature and viscosity, etc. for PSAs were also studied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43281.     

Viscoelastic and adhesive properties of single‐component thermo‐resistant acrylic pressure sensitive adhesives

Poly(butyl acrylate‐vinyl acetate‐acrylic acid) based acrylic pressure sensitive adhesives (PSAs) were synthesized by solution polymerization for the fabrication of high performance pressure sensitive adhesive tapes. The synthesized PSAs have high shear strength and can be peeled off substrate without residues on the substrate at temperature up to 150°C. The PSAs synthesized in the present work are single‐component crosslinked and they can be used directly once synthesized, which is convenient for real applications compared to commercial multi‐component adhesives. The results demonstrated that the viscosity of the PSAs remained stable during prolonged storage. The effects of the preparation conditions such as initiator concentration, cross‐linker amount, organosiloxane monomer amount and tackifier resin on the polymer properties, such as glass transition temperature (T_g), molecular weight (M_w), surface energy and shear modulus, were studied, and the dependence of the adhesive properties on the polymer properties were also investigated. Crosslinking reactions showed a great improvement in the shear strength at high temperature. The addition of tackifier resin made peel strength increase compared to original PSAs because of the improvement of the adhesion strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40086.     

Acrylic pressure‐sensitive adhesive for transdermal drug delivery systems

This article describes the development in the area of resin‐free acrylic pressure‐sensitive adhesive (PSA) based on 2‐ethylhexyl acrylate, methyl acrylate, acrylic acid, N‐vinyl caprolactam, and pregnancy transdermal drug delivery systems, and shows the variety of polymer composition, residue monomers content, quality control of peel adhesion level and repeating during the time, biocompatibility of the acrylic PSA layer, and efficacy in clinical medicine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion‐Based Pressure‐Sensitive Adhesives

Summary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi‐batch mode. The objective was to generate polymers with properties favoring their application as pressure‐sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (T_g), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three‐component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. T_g, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration.

Shear strength contour lines over the investigated region.     

Effect of N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine antioxidant on the adhesion properties of (zinc oxide)‐filled (epoxidized natural rubber 25)‐based pressure‐sensitive adhesives

The effect of antioxidant, namely, N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine (IPPD), on the adhesion properties of epoxidized natural rubber (ENR 25)‐based pressure‐sensitive adhesive was investigated. The concentration of the IPPD was varied from 0 to 5 parts by weight per hundred parts of rubber (phr). Coumarone‐indene resin, zinc oxide, toluene, and polyethylene terephthalate were used as the tackifier, filler, solvent, and substrate, respectively. A Lloyd Adhesion Tester operating at different testing rates (10–60 cm/min) was used to determine the loop tack, peel strength, and shear strength at 60‐µm and 120‐µm coating thicknesses. Results indicate that adhesion properties increase with IPPD up to 2 phr of content, after which it decreases with further addition of the antioxidant. This observation is attributed to the culmination of wettability and compatibility at the optimum IPPD concentration. The 60‐µm coated sample consistently shows higher adhesion strength than that of 120‐µm coated sample. Loop tack and peel strength increase with testing rate up to 30 cm/min. However, shear strength increases with increasing testing rate in the testing rate investigated in this study. J. VINYL ADDIT. TECHNOL., 21:111–115, 2015. © 2014 Society of Plastics Engineers     

Molecular design for silane‐terminated polyurethane applied to moisture‐curable pressure‐sensitive adhesive

Moisture‐curable silane‐terminated polyurethanes (SPUs) served as pressure‐sensitive adhesive (PSA) were synthesized based on different soft‐segment materials, silanes and silane end‐capping ratios. Depending on peel strength, tack, and holding power, the characteristic properties for PSA, a proper scheme for the design of the PSA molecular structure could be selected. Completely end‐capped by silane and assembled by poly(propylene glycol), SPU films presented better properties. On the basis of comprehensive considerations, the anilinomethyltriethoxysilane was an excellent silane‐end capper for PSA. Otherwise, the obtained PSAs did not degrade below 250 °C. The glass transition temperature and hydrophobicity of SPU samples with different formulas were also investigated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45292.     

Influence of selected photoinitiators on important properties of photoreactive acrylic pressure‐sensitive adhesives

Photoreactive solvent‐borne pressure‐sensitive adhesives are not commercially available in the market. The reason for it is that the UV‐initiated crosslinking has sense only in the case of solvent‐free self‐adhesive systems. Investigations conducted in Institute of Chemical Organic Technology have shown that the photoreactive solvent‐borne acrylic PSA are conventional crosslinked solvent‐borne acrylic PSA used as crosslinking agents typical metal chelates as titanium acetylacetonate (TiACA), aluminum acetylacetonate (AlACA) or thermal reactive crosslinker melamine‐formaldehyde resin Cymel 303 clear considered. The main purpose of the investigation was to study the influence of diverse photoinitiators on main properties, such as shrinkage, tack, peel adhesion, and shear strength of solvent‐based acrylic pressure‐sensitive adhesives. The interesting alternative to conventional photoinitiators is unsaturated photoinitiators described in this article. Following unsaturated photoinitiators were used: 4‐acryloyloxy benzophenone, 4‐acryloyloxyethoxy benzophenone, and 4‐acryloyloxybutoxy benzophenone. The influence of the crosslinking agents or crosslinking methods was determined in relation to the reaction time and to the concentration versus adhesion properties. The increase of photoinitiator concentration causes in the decrease of the shrinkage. Increasing the UV dose during the crosslinking of acrylic PSA film leads clearly to better shrinkage resistance. The best results of the lowest shrinkage value of 0.35% were given by using 4‐acryloyloxy benzophenone. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adhesive failure peak in peel spectra

Peel force spectra for pressure‐sensitive adhesive tapes provide a peel peak in the adhesive failure region. The observed peak behavior is coincident with calculation based on a viscoelastic peel model. It turns out that the origin of the peak is significantly associated with viscoelasticity or short relaxation time of the adhesive. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 264–266, 1999     

Solvent‐free radiation‐curable polyacrylate pressure‐sensitive adhesive systems

This article shows radiation‐curable solvent‐free pressure‐sensitive adhesive polyacrylates, their synthesis, chemical modifications, important properties and use after crosslinking with UV‐lamps and UV‐lasers for the production of self‐adhesives tapes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 182–191, 2003     

Crosslinking of pressure sensitive adhesive based on water‐borne acrylate

This publication shows how the kind of crosslinking agents and their contents influence important properties of acrylic based pressure‐sensitive adhesive (PSA) dispersions such as tack, adhesion and cohesion. Synthesized PSAs based on acrylic polymers, containing 2‐ethylhexyl acrylate, butyl acrylate, vinyl acetate, styrene and acrylic acid are used in the preparation of self‐adhesive dispersions used as coating of polyethylene foams and poly(vinyl chloride) and polyester foils. © 2003 Society of Chemical Industry     

Influence of the interfacial adhesion on the stringiness of crosslinked polyacrylic pressure‐sensitive adhesives

The stringiness of crosslinked polyacrylic pressure‐sensitive adhesives (PSA) was observed during 90° peeling under a constant peel rate with various adherends in order to clarify the influence of interfacial adhesion on the stringiness behavior. The crosslinked random copolymer of butyl acrylate with 5 wt % acrylic acid was used as a representative PSA. Poly(methyl methacrylate) (PMMA), polycarbonate (PC), poly(vinyl chloride) (PVC), fused quartz plates and some surface‐modified poly(ethylene terephthalate) films were used as adherends. The films were pasted on a glass plate using a cyanoacrylate adhesive. The 180° peel strength was higher in the order of PVC >> PMMA ≈ PC > other adherends. All observed stringiness was sawtooth‐shaped, but the stringiness width and length were longer in the same order. The number of sub‐branches formed at the tips of the strings was much more for the PVC, PMMA and PC adherends. Frames formed at the front end of the strings in the case of PVC adherend. Sufficient interfacial adhesion generates large internal deformation of the PSA layer. Internal deformation occurred preferentially over peeling as a result of front frame formation. The string length and the peel load required for the constant peel rate have good correlation with the peel strength. The estimation of generated inner stress in the fibrils of the strings was possible by analysis using the string length for various adherends and the stress–strain curve of pure PSA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40869.     

Rheological and adhesion properties of acrylic pressure‐sensitive adhesives

Different pressure‐sensitive adhesives (PSAs) based on acrylic monomers were synthesized under different reaction conditions. The synthesized PSAs have good adhesive properties and without leaving any residue can be easily peeled off from the surface of a substrate. The relationship between PSAs rheological behavior and its adhesion properties (e.g., peel, tack, and shear resistance) has been studied at constant adhesive thickness. The samples were examined for their surface energy and viscoelastic characteristics. It was observed that increase in reaction temperature and reaction time results in decreased storage modulus due to lowered molecular weight, which finally leads to lower elasticity of the PSA. While the storage (G′) and loss (G″) modulus of samples increase with increased initiator concentration, the elasticity of PSA is increased as well. High G″ at high frequency (100 Hz) represents high peel strength because of higher dissipation of viscoelastic energy during debonding. The tack values increase by lowering storage modulus at 1 Hz due to higher M_e. Shear values are increased by higher storage modulus at low frequency (0.1 Hz) due to hydrogen bonding of the different components. Some parallel investigations on the surface energy of the samples showed that they have different properties because of the nature of different monomeric units with their corresponding orientations. Our results reveal that the peel strength is not affected by surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crosslinked acrylic pressure‐sensitive adhesives. I. Effect of the crosslinking reaction on the peel strength

For pressure‐sensitive adhesives (PSAs) composed of poly(co‐ethyl acrylate‐2‐ethylhexyl acrylate‐2‐hydroxyethyl methacrylate) as a base resin and polyisocyanate as a crosslinker, the relationship between the crosslinking reaction and peel strength was investigated. A 90° peel test of cured PSA films under various storage conditions was carried out. At the same time, the isocyanate (NCO) consumption in these PSA films was monitored by attenuated total reflectance/Fourier transform infrared spectroscopy. The peel strength of the PSA compounded with the crosslinker decreased as the NCO groups were consumed. The elevation of the aging temperature promoted the crosslinking reaction and increased the decrement in the peel strength. The peel strength of noncrosslinked and crosslinked PSA films increased with the contact time. A high storage temperature made the increment in the peel strength increase. The addition of the crosslinker to the PSA films reduced the increment in the peel strength. Furthermore, PSA films with residual NCO groups possessed stronger peel strengths than fully cured films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1493–1499, 2003     

Effect of the MMA content on the emulsion polymerization process and adhesive properties of poly(BA‐co‐MMA‐co‐AA) latexes

In the past work, the shear resistance of pure poly(n‐butyl acrylate) was low, even incorporation of inorganic filler, silica in the composition. It is well‐known that the copolymerization of n‐butyl acrylate (BA) with methyl methacrylate (MMA) will increase the glass transition temperature, and enhance the shear resistance of acrylic polymers. In the current work, the preparation of a series of acrylic water‐borne pressure‐sensitive adhesives (PSAs) with the controlled composition and structure for the copolymerization of BA and acrylic acid (AA) with different MMA contents, poly(BA‐co‐MMA‐co‐AA) was reported and its effects on adhesive properties of the latices were investigated. The latices of poly(BA‐co‐MMA‐co‐AA) were prepared at a solid content of 50% by two‐stage sequential emulsion polymerization, and this process consisted of a batch seed stage giving a particle diameter of 111 nm, which was then grown by the semicontinuous addition of monomers to final diameter of 303 nm. Dynamic light scattering (DLS) was used to monitor the particle diameters and proved that no new nucleation occurred during the growth stage. Copolymerization of BA with MMA raised the glass transition temperature (T_g) of the soft acrylic polymers, and had the effect of improving shear resistance, while the loop tack and peel adhesion kept relatively high. The relationship between pressure‐sensitive properties and molecular parameters, such as gel content and molecular weight, was evaluated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dependence of adhesion property of acrylonitrile‐butadiene rubber‐based adhesive on zinc oxide concentration

Viscosity and adhesion properties of acrylonitrile‐butadiene rubber (NBR)‐based pressure‐sensitive adhesive were investigated by using zinc oxide as the filler. The zinc oxide loading was varied from 10 to 50 parts by weight per hundred parts of rubber (phr). Coumarone–indene resin, toluene, and polyethylene terephthalate were used as the tackifying resin, solvent, and coating substrate, respectively. Viscosity of the adhesive was measured by a Brookfield viscometer, whereas the loop tack, peel strength, and shear strength were determined by a Lloyd adhesion tester operating at 10 to 60 cm/min. Results show that viscosity increases with zinc oxide loading because of the concentration effect. Loop tack and peel strength pass through a maximum value at 20 phr of zinc oxide concentration, whereas the optimum zinc oxide loading for shear strength is 30 phr. This observation is attributed to the effect of varying degrees of wettability and compatibility of the adhesive on the substrate. In all cases, the adhesion properties of adhesives increase with coating thickness and testing rates. J. VINYL ADDIT. TECHNOL., 23:241–246, 2017. © 2015 Society of Plastics Engineers     

Improved heat and solvent resistance of a pressure‐sensitive adhesive thermally processable by isocyanate dimer dissociation

Methods that do not involve use of an organic solvent are being considered for manufacturing environmental‐friendly pressure‐sensitive adhesive tapes. Among these methods, the hot‐melt method exhibits high productivity but is somewhat limited in terms of performance. Hot‐melt‐fabricated pressure‐sensitive adhesives require heating fluidization and cooling solidification, and it is extremely difficult to improve their heat resistance. We examine thermally processable pressure‐sensitive adhesives with a completely new structure, fabricated based on the thermal dissociation of the isocyanate dimer. This enables thermal processing of materials softened by thermal dissociation. Fabrication of crosslinkable pressure‐sensitive adhesive becomes possible through a reaction of isocyanate caused by dissociation of its dimer. It is found that improving thermal and solvent resistances, which are disadvantages associated with conventional hot‐melt pressure‐sensitive adhesives, is potentially possible with the pressure‐sensitive adhesive reported here. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41444.     

Synthesis of high‐solid‐content,acrylic pressure‐sensitive adhesives by solvent polymerization

In this study, we prepared high solid content (SC), solvent‐based, acrylic pressure‐sensitive adhesives (PSAs) with n‐dodecyl mercaptan as a chain‐transfer agent (CTA) and studied the crosslinking reactions between the crosslinker and the acrylic PSAs. Acrylic PSAs were prepared from 2‐ethyl hexyl acrylate, acrylic acid (AA), and 2‐azobisisobutyronitrile with a solution polymerization process. The results show AA resulted in an effective molecular weight in the acrylic PSAs, as it improved the hydrophilicity with increasing peel strength of the acrylic PSAs. As for the high SC, the molecular weight and system viscosity decreased through the addition of CTA. At a constant AA amount, the addition of CTA decreased the molecular weight and increased the hydrophobicity of the acrylic PSAs; this decreased the peel strength of the acrylic PSAs on the glass. Furthermore, the addition of CTA decreased the molecular weight and improved the acrylic PSAs' surface morphologies and optical properties. The acrylic PSAs produced in this study could meet production needs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46257.