Emulsion Pressure-sensitive Adhesives Research Articles

Preparation and characterization of polyacrylate emulsion pressure-sensitive adhesives with various lengths of fluorinated side chains

A series of fluorinated polyacrylate emulsion pressure-sensitive adhesives (PSA) with various lengths fluorinated side chains were synthesized by using n-butyl acrylate (nBA), acrylic acid (AA), 2-hydroxyethyl acrylate (HEA) together with three kinds of fluorine monomers trifluoroethyl methacrylate (TFEMA), hexafluorobutyl methacrylate (HFBMA) and dodecafluoroheptyl methacrylate (DFHMA). The influences of fluorocarbon chains’ length on the particle size of the latex, as well as on thermostability (DSC, TG) and surface properties (XPS, CA, AFM) of the PSA films were investigated. The results showed that T g and thermal stability of the PSA were both increased with the introduction of F-monomers with various lengths of fluorinated side chains, and the shorter the side chain, the more the T g and thermal stability increased. The XPS results indicated that the surface atom percentage of F element of film increased with the escalation of the length of fluorocarbon lateral chain, which results in the water contact angle and surface roughness increment of the PSA films. Finally, effects of fluorocarbon chains’ length on the adhesive properties (i.e. loop tack, peel strength and shear strength) of the fluorinated latex PSA were also evaluated.

Effect of cyclohexyl methacrylate (CHMA) on the comprehensive properties of acrylate emulsion pressure sensitive adhesives

Cyclic methacrylate monomer cyclohexyl methacrylate (CHMA) was evaluated as an alternative to traditional methyl methacrylate (MMA) as hard monomer in the application of acrylate latex pressure sensitive adhesive (PSA). The influences of CHMA on the resultant latex and PSA properties were comprehensively investigated. Both FTIR and 1H NMR analysis indicated that CHMA could be successfully introduced into the latex PSA copolymer through emulsion polymerization. TEM images illustrated that the synthesized latex particles are spherical and uniform. DSC and TGA results showed that Tg of the copolymer was elevated, while thermal stability was decreased with introduction of CHMA. Besides, it was also found that water resistance of the latex PSA was improved by the presence of CHMA, confirmed by water contact angle measurements. Furthermore, as CHMA amount increased, gel content slightly decreased, while sol molecular weight (Mw ) of the polymer increased. Finally, it was observed that loop tack decreased, while shear strength increased with the incorporation of CHMA. 180° peel strength of the PSA initially increased and then decreased with the addition of CHMA from 0 to 30 wt%, with a maximum value at 10 wt%.

High holding power of acrylic emulsion PSA with sorbitan nonionic surfactants and cross-linker

Since traditional nonyl phenyl type nonionic surfactants have been known as destructive to the ecosystem, sorbitan nonionic surfactants (Tween 20, 40, 60 and 80) were used to make acrylic emulsion type pressure sensitive adhesives (PSA), and the type of effects they have on the adhesive properties were investigated. Also, their adhesive properties were compared with those synthesized using traditional nonyl phenyl nonionic surfactant (NP 40). As a result, PSA made using Tween60 showed higher initial tack and peel strength and a much higher holding power than those properties made using NP 40 at room temperature. PSA made by Tween 60, and cross-linked by DGEBA (Bisphenol A diglycidyl ether) and phenyl aziridine, exhibited over 12 h of holding power at 150 °C, and showed a holding state up to 180 °C during a SAFT test (Shear Adhesion Failure Temperature).

Effect of dodecafluoroheptyl methacrylate (DFMA) on the comprehensive properties of acrylate emulsion pressure sensitive adhesives

Fluorinated acrylate emulsion pressure sensitive adhesives (PSA) based on butyl acrylate (BA), fluorine monomer dodecafluoroheptyl methacrylate (DFMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were synthesized via a monomer-starved seeded semi-continuous emulsion polymerization process. The influences of DFMA on the resultant latex and PSA properties were comprehensively investigated. FTIR analysis indicated that DFMA could be successfully introduced into the latex PSA copolymer through emulsion polymerization. DSC and TG analyses showed that Tg and thermal stability of the PSA were both improved as DFMA content increased. XPS analysis indicated that fluoroalkyl groups had a tendency to enrich on the surface of the film, and the more DFMA added the more F content on the film surface. Moreover, the surface roughness and contact angle of the acrylate latex PSA film were both increased with the introduction of DFMA. Dynamic mechanical analysis (DMA) and adhesive property tests showed that the storage modulus (Gʹ) and shear holding power were improved with DFMA content while at the sacrifice of loop tack. Finally, 180° peel strength of fluorinated acrylate latex PSAs on different substrates (PP, SS) as a function of DFMA content was evaluated.

Synthesis of flame retardant acrylic emulsion pressure sensitive adhesives by co-polymerization with phosphoric flame retardant monomer

Synthesis of flame retardant acrylic emulsion pressure sensitive adhesives by co-polymerization with phosphoric flame retardant monomer

The application research of environment-friendly reactive surfactants in acrylate emulsion pressure sensitive adhesives

In this article acrylate pressure sensitive adhesive (PSA) latexes were synthesized via a pre-emulsion seeded semi-batch emulsion polymerization process with a conventional nonreactive surfactant (CO-436) and two polymerizable surfactants (traditional surfmer SE-10N and environment-friendly surfmer SR-10). The effects of surfactant contents on the particle size, zeta potential, electrolyte stability of the latexes and gel content, sol molecular weight (Mw, Mn), water absorption of the PSA copolymers were investigated. In addition, X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to characterize the latex films. The results showed that the particle sizes of latexes prepared with surfmers were smaller than their CO-436 containing counterparts. And the latexes prepared with surfmers had a lower storage stability than the one prepared with CO-436. However, surfmers can improve the electrolyte stability of the latex. Furthermore, the water resistances of the latexes prepared with surfmers were better than that of the latex with CO-436, which can be confirmed by water absorption, contact angle and XPS analysis. The results also indicated that the PSA prepared with SR-10 exhibited the highest gel content among the three surfactants. Finally, the effects of surfactants on the adhesive properties of the PSAs were also evaluated.

Effect of trifunctional cross-linker triallyl isocyanurate (TAIC) on the surface morphology and viscoelasticity of the acrylic emulsion pressure-sensitive adhesives

Acrylic pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer-seeded semi-continuous emulsion polymerization process with butyl acrylate (BA), methyl methacrylate, acrylic acid (AA), 2-hydroxyethyl acrylate and trifunctional cross-linker, triallyl isocyanurate (TAIC). Influences of TAIC on the resultant latex and PSA properties were comprehensively investigated. The results indicated that latex particle size was independent of the amount of TAIC in the pre-emulsion feed, while the viscosity of the latex increased remarkably with TAIC content increased. Thermal gravimetric analysis result showed that the thermal stability of the polymers was improved significantly with the addition of TAIC. Besides, with the increase in TAIC content, gel content of the polymer increased significantly, while molecular weight between cross link points (Mc) and sol molecular weight (Mw, Mn) of the polymer decreased remarkably. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncrosslinked counterparts. Finally, dynamic mechanical analysis and atomic force microscopy were also used to evaluate the viscoelastic properties and surface morphology of the acrylic emulsion PSA film, respectively.

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.

Synthesis of a glucose-based surfmer and its copolymerization with n-butyl acrylate for emulsion pressure sensitive adhesives

A glucose-based vinyl surfmer, i.e. butyl polyglucoside maleic acid ester (BGMAH), was synthesized and characterized. Macroemulsion copolymerization of BGMAH with n-butyl acrylate (n-BA) was investigated. The structure of the synthesized BGMAH was confirmed using Fourier transform infrared spectroscopy and a series of 2-D homo- and heteronuclear NMR spectra. Its surfactant properties were confirmed by determination of the critical micelle concentration. The semi-batch emulsion copolymerization was monitored in situ using FTIR spectroscopy. The particle size and its distribution of the emulsions and the gel phase of the polymers were determined. The glass transition temperatures were assessed using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The obtained emulsions were tested for potential application in pressure sensitive adhesives by measuring the adhesion properties of copolymer films (peel strength, tack and shear resistance). It was found that synthetic acrylates could be replaced by the modified glucose in the emulsion polymerization recipe. The adhesion properties were improved when 25wt% of BGMAH was added in reaction mixture.

Formulation of Emulsion Adhesives with Removal Properties by Using Alkali Soluble Resins

This study was aimed at developing environmental friendly adhesion materials using alkali soluble resins (ASRs). Water-borne emulsion pressure-sensitive adhesives show good compatibility with different polymer emulsions, high solid contents, and good working property, thereby allowing adjustment of the extensive viscosity. On the other hand, it is not easily recyclable and its adhesion and water-resistance properties are not optimal. Herein, ASR was used as the polymeric surfactant. ASR presents good emulsion stabilization, high molecular weight, and solubility in alkali solutions. ASR contains both hydrophobic and hydrophilic groups, thereby reducing the surface tension of the aqueous phase stabilizing monomer droplet or polymer particles. Additionally, it can form aggregates as a result of inter- and intramolecular hydrophobic interactions. The large number of carboxyl groups of this resin stabilizes polymer particles by an electrostatic effect. The recycling and adhesion properties of this resin were assessed by using UTM, a weight method. Further properties of the resin were determined by DSC, GPC, and ETC.

Emulsion Semi-Batch Terpolymerization Process Using Hybrid Emulsifiers for Synthesizing New Emulsion Pressure Sensitive Adhesives (EPSAs)

In order to obtain a suitable formulation of designing direct synthesis of acrylic latexes to be used as emulsion pressure sensitive adhesives (EPSA), having high shear resistance together with high peel strength and tack, free radical emulsion polymerization of hard monomers, such as styrene (St), vinyl acetate monomer (VAM), methyl methacrylate (MMA) and butyl methacrylate (BMA), and soft monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA) along with multifunctional monomers, namely acrylic acid (AA), were carried out. The effect of the type of hard and soft acrylic monomers, the type and level of emulsifiers, and the initiator concentration on the emulsion polymer stability and final properties of the EPSA were investigated. The results obtained showed an optimized composition. This composition led to a significant increase in shear strength and peel strength to 909 kPa and 0.45 N/mm, respectively, while the synthesized PSA was still too tacky, 5.5 cm, according to adhesion performance testing. For making this successful balance of the conflicting adhesion properties of PSA, a series of anionic and nonionic emulsifiers were investigated. It was interestingly found out that the hybrid emulsifiers (anionic coupling with nonionic) with the optimized compositions could enhance the stability of the emulsion system and improve the properties of PSA compared with the mono-emulsifier. We also tried to adjust the initiator concentration with the level of the optimized hybrid emulsifier, polyoxyethylene alkyl phenyl ether (K30), dioctyl sulfosuccinate (DOSS), and sodium vinyl sulfonate (SVS) with the ratio 2:1:1, resulting in a highly preferred proportion of the 0.5 part of the initiator versus 1.25 parts of the hybrid emulsifier in terms of the total weight of the monomers.

ポリビニルアルコールを保護コロイドとして用いたアクリルエマルジョン粘着剤

ポリビニルアルコールを保護コロイドとして用いたアクリルエマルジョン粘着剤

Viscoelastic properties and peel strength of water-borne acrylic PSAs for labels

The use of acrylic emulsion pressure-sensitive adhesives (PSAs) in labels continues to increase due to their environmental friendliness, good aging resistance and excellent processability during coating process. This study has investigated the acrylic emulsion/tackifier blend systems by examining their thermal properties as indicated by the glass transition temperature (T g), by conducting optical microscopy to determine their structure, by exploring their viscoelastic properties with the advanced rheometric expansion system (ARES), and by measuring their peel strength with the 180° peel test. The acrylic emulsion/tackifier blends with low softening point and low molecular weight exhibited only a single T g. However, the acrylic emulsion/tackifier blends with high softening point and high molecular weight showed two T g values. Microscopic observation of blends with miscible tackifier did not show any evidence of tackifier traces, whereas the microscopic structures of blends with immiscible tackifier showed dispersed tackifier particles. As the tackifier content increased, the rubbery plateau region decreased for the miscible blends but increased for the immiscible blends. The 180° peel strength of the miscible blends was dependent on the viscoelastic properties and was influenced by incorporation of tackifiers in the PSA systems. However, the peel strength of the immiscible systems did not depend on the viscoelastic properties at low tackifier content, but it decreased as the tackifier content increased in accordance with the increase of the storage modulus G′.

Acrylic emulsion pressure-sensitive adhesives (PSAS) reinforced with layered silicate

Composite acrylic pressure-sensitive adhesives (PSAs) were synthesized by emulsion polymerization in the presence of montmorillonite (MMT). An examination with X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that both intercalated and exfoliated structures of MMT coexisted in the composites. It was demonstrated by X-ray photoelectron spectroscopy (XPS) that enrichment of the surface by the surfactant during drying of emulsion PSAs was depressed by the layered silicate. Significant improvements in storage modulus and cohesive strength were achieved by incorporation of MMT. The addition of only a small amount of MMT was enough to improve the adhesion properties of acrylic emulsion PSAs.

Studies on the water resistance of acrylic emulsion pressure-sensitive adhesives (PSAs)

Four different types of acrylic emulsion pressure-sensitive adhesives (PSAs) with the same composition of their constituent co-polymers but stabilized by four different anionic surfactants, two conventional low-molecular-weight surfactants (a sodium salt and an ammonium salt) and two anionic monomers (a sodium salt and an ammonium salt) were prepared. The adhesion properties of the four types of PSA tapes coated onto PET (poly(ethylene terephthalate)) sheets were determined with the national standard methods of China. Water absorption and water solubility of PSA films were determined by the gravimetric method. The peel-strength retention of PSA tapes after immersion in water was compared. The results showed that both the adhesion properties and the water resistance of the acrylic PSAs stabilized by anionic monomers were better than that of the acrylic PSAs stabilized by low-molecular-weight surfactants, and the ammonium surfactants were better than the sodium surfactants. These differences were mainly caused by the different migration ability of the four surfactants in the PSA layers and their different hydrophilic nature, as explained in terms of surfactant content at the surfaces of PSA layers with X-ray photoelectron spectroscopy (XPS).

Mechanistic studies in tackified acrylic emulsion pressure sensitive adhesives

Mechanistic studies in tackified acrylic emulsion pressure sensitive adhesives

Mechanistic studies in tackified acrylic emulsion pressure sensitive adhesives

Twenty-three wt % aqueous tackifier dispersion based on glycerol ester abietic acid (Tg = 64°C, Mw = 940) was added to emulsion polymer 50/32/15/3 poly(2-ethyl hexyl acrylate-co-vinyl acetate-co-dioctyl maleate-co-acrylic acid) pressure sensitive adhesive (PSA). From these latices, 25 μm thick films were cast. The films were dried at 25°C for 24 h or at 121°C for 5 min. Dynamic mechanical analysis (DMA) of the films included measuring elastic modulus (G′) and damping factor (tan δ). Under the above drying conditions, the films did not produce significant differences in their DMA and PSA properties as measured by loop tack, peel, and shear holding power. DMA of the tackified acrylic film showed thermodynamic miscibility between the tackifier and polymer regardless of the drying conditions. Microgels formed during emulsion polymerization of the acrylic PSA brought inherent weakness to the tackified film properties. In the neat acrylic PSA film, these discrete networks entangled with the uncrosslinked chains while in the tackified film, these networks could not form entanglements due to the increased molecular weight between entanglements for the uncrosslinked chains. This lack of network entanglements caused shear holding power of the tackified acrylic PSA film to be 4× lower than that of the neat acrylic PSA film. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1965–1976, 2000