Pressure-sensitive Adhesive Applications Research Articles

Biomass-sourced polymers for pressure-sensitive adhesive applications

Pressure-sensitive adhesives are self-adhesive chemical products that have gradually supplanted traditional glues in recent years. Most of the commercially available pressure-sensitive adhesives are derived from petrochemical resources. The increasing attention to environmental protection, coupled with the introduction of stringent regulations and rising oil prices, has led to widespread attention being paid to the development of sustainable pressure-sensitive adhesives from biomass sources. This paper summarizes the biomass-sourced pressure-sensitive adhesives and their modification methods that have been reported in recent years as promising alternatives to petrochemical resources.

Sustainable terpene triblock copolymers with tuneable properties for pressure sensitive adhesive applications

A series of triblock copolymers in a hard-soft-hard block configuration with varying hard block α-pinene methacrylate content and molecular weight and butyl acrylate soft segment have been synthesised and investigated for viability in pressure sensitive adhesive (PSA) applications. The morphologies vary from pockets of hard phase distributed within a continuous soft matrix, through to lamellar with co-continuous phases, and finally continuous hard phase with pockets of soft phase dispersed. Uniaxial tensile properties, probe adhesion performance and cyclic adhesive behaviour are presented for seven compositions including four short chain and three long chain copolymers, alongside a commercial benchmark PSA. Structure-property relationships for the novel elastomers are evaluated, establishing that short chain materials with 20–25 wt% poly(α-pinene methacrylate) offer similar tensile and adhesion performance to the commercial elastomer. Raising the hard phase concentration has been observed to provide a considerable increase in ultimate tensile strength, stiffness and peak tack force, but at the expense of significant reductions in ultimate tensile strain, adhesive bond displacement and vibrational dissipation. The results suggest that the performance of these sustainable materials can be tuned to produce viable PSAs with a range of useful properties.

Relationship between large amplitude oscillatory shear (LAOS) experiments and commercial pressure sensitive adhesives applications testing

Abstract Historically, analytical test methods on pressure sensitive adhesives (PSAs) have shown modest correlation to applications test results. Since applications tests such as peel strength and shear strength involve large deformations of the adhesive, large amplitude oscillatory shear (LAOS) experiments may correlate more strongly to the applications test results than typical linear viscoelastic measurements. Here we report some of the earliest LAOS measurements on commercial PSA films and compare them to the measured peel strength and shear strength. The parameters, G’M, Q, and e3/e1, showed a strong correlation to the peel and shear results while the parameters, S, T, and v3/v1, demonstrated weaker dependencies. While detailed molecular level interpretation of the LAOS results is not possible, these results indicate LAOS testing may provide a better indication of applications performance in a more efficient way than existing applications test protocols.

UV-Tunable Biobased Pressure-Sensitive Adhesives Containing Piperonyl Methacrylate

Novel waterborne pressure-sensitive adhesives (PSAs) with biobased contents up to 71% and UV-light-tunable features have been developed using piperonyl methacrylate (PIPEMA) as a hard monomer. The biobased monomer was synthesized from piperonyl alcohol (derived from black pepper), and its homopolymer was fully characterized. Emulsion polymerization was chosen as a sustainable strategy to copolymerize piperonyl methacrylate together with biobased 2-octyl acrylate to produce high-solid-content latexes for pressure-sensitive adhesive applications. The UV light curing ability of the piperonyl methacrylate moieties in the copolymer backbone yielded PSAs with excellent shear resistance and reasonable adhesive properties (tack and peel).

Nematic liquid crystal 4-cyano-4′-pentylbiphenyl functionalization of MWNTs for improved thermal and mechanical properties of silicone pressure sensitive adhesives

In this research, nanocomposite modified pressure sensitive adhesives (PSA) (5CB-MWNTs/PSA) with high mechanical and thermal properties were fabricated via nematic liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) functionalized multi-walled carbon nanotubes (MWNTs). The results showed that 5CB interacted with MWNTs via non-covalent interactions e.g. π-π stacking, which not only improved the dispersion and orientation of MWNTs in a silicone PSA but also the compatibility between MWNTs and the silicone material. The tensile strength of 5CB-MWNT/PSA was increased to 14.5 MPa while the mass fraction of MWNTs was 1.0%, which was an enhancement of 943% over that of the MWNTs/PSA and 28 times greater than that of the neat PSA. In addition the thermal conductivity of the PSAs filled with the 5CB-MWNTs were improved to 1.28 W/(m•K) at a mass fraction of 10%, which was increased by 552% over that of the neat PSA and 231% over that of the MWNT/PSA. The resulting thermally conductive and mechanically applicable silicone PSA nanocomposites could be significant in a wide variety of pressure sensitive adhesive applications.

Preparation and characterization of self-crosslinking fluorinated polyacrylate latexes and their pressure sensitive adhesive applications

Self-crosslinking fluorinated polyacrylate latexes based on butyl acrylate (BA), fluorine monomer octafluoropentyl methacrylate (OFPMA), self-crosslinking functional monomers acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were synthesized by a monomer-starved seeded semi-continuous emulsion polymerization process. The latexes and their corresponding films were characterized by laser particle size analyser, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results indicated that the particle size of the latexes and the gel content of the films were both independent of the amount of OFPMA employed. On the other hand, the particle size of the latexes decreased and the gel content of the films increased with the incorporation of AA and HEA as expected. Glass transition temperature (Tg) and the thermal stability of the copolymer were both improved gradually as OFPMA content increased. XPS, AFM and water contact angle measurement indicated that the fluoroalkyl groups had a tendency to enrich on the surface of the films. However, this enrichment of fluorine on the film surface was reduced after the introduction of self-crosslinking functional monomers into the system. Finally, the adhesive property of the latexes was evaluated for application as a pressure sensitive adhesive (PSA).

Potential of Organosolv Lignin Based Materials in Pressure Sensitive Adhesive Applications

Blending lignin with other polymers has long been utilized as a potent approach to explore novel applications for lignin. Yet, combinations of organosolv lignin (OSL) with superplasticizer have bee...

Preparation and characterization of natural rosin stabilized nanoparticles via miniemulsion polymerization and their pressure-sensitive adhesive applications

A series of rosin stabilized nanoparticles were prepared by miniemulsion polymerization. The hydrophobicity of dehydroabietic acid (DA) from rosin or from DA derived acrylic monomer (AEDA) was employed to stabilize the monomer miniemulsions. Then miniemulsion polymerizations of these monomer miniemulsions were performed separately and achieved the rosin stabilized nanoparticles with a near-monodisperse spherical morphology, respectively. This approach can effectively incorporate DA or AEDA into polyacrylate miniemulsion. Herein, AEDA played a role as both costabilizer and reactant in miniemulsion polymerization, and high molecular weight AEDA-MMA copolymers were achieved. The introduction of rosin’s moiety also could afford its copolymers with an improved thermal stability and mechanical property. Unlike conventional usage of rosin derivatives as a tackifying resin in pressure-sensitive adhesives (PSA), AEDA served as a hard component and improved the holding power of PSA, which opens a new platform for the using of rosin.

Tailoring Soft Polymer Networks Based on Sugars and Fatty Acids toward Pressure Sensitive Adhesive Applications

The present work describes the synthesis and characterization of fully biobased soft polymer networks for pressure sensitive adhesives applications. The incorporation of different sugars into fatty-acid-based monomers, made it possible to tailor the viscoelastic properties of the materials. Lipase catalysis allowed to afford monomers with varying hydroxyl content and epoxy-functionalities. Step-growth polymerization catalyzed by DBU resulted in soft-polyester networks through combination of the monomers with a biobased diacid. Rheological and adhesion studies were performed to elucidate the different viscoelastic and adhesive properties of the materials as a function of their composition.

Polyols from epoxidized soybean oil and alpha hydroxyl acids and their adhesion properties from UV polymerization

Two types of biobased polyols, ESOGA and ESOLA, were synthesized from epoxidized soybean oil (ESO) with glycolic acid (GA) and lactic acid (LA), respectively, using a solvent-free/catalyst-free method. An ESO epoxy conversion rate of over 93% was achieved for both polyols. ESOGA has a weight-/number-average molecular weight (Mw/Mn) of 27,700/3900g/mol and average hydroxyl functionality (fOH) of 12.9, and ESOLA has Mw/Mn of 8800/3000g/mol and fOH of 11.7. The structures of the polyols were further characterized with Fourier transform infrared spectroscopy and 1H-nuclear magnetic resonance. Rheology and thermal properties were studied with a rheometer and a differential scanning calorimeter. The polyols were polymerized with ESO to adhesive polymers using UV light in the presence of cationic photoinitiator. The curing rate decreased as the amount of polyol increased for resins based on ESOGA and ESOLA (EGA and ELA). With the same amount of polyol, ELA resins cured faster than EGA resins. The peel strength and tack of EGA and ELA adhesives increased significantly as the ratio of polyol in the resin increased. ELA exhibited obviously higher peel strength and tack than EGA with the same amount of polyol. All resin tapes exhibited high static shear values (20,000+min). Overall, both ESOGA and ESOLA exhibited great potential as polyols for pressure-sensitive adhesive applications.

Interplay Between Viscoelastic and Chemical Tunings in Fatty-Acid-Based Polyester Adhesives: Engineering Biomass toward Functionalized Step-Growth Polymers and Soft Networks

This Article describes the synthesis and characterization of renewable self-adhesive coatings with tunable viscoelastic properties and equipped with well-defined amounts of carboxylic acid "sticker" groups with adhesion promoting characteristics. Hydroxyl-ended polyesters with various architectures (linear, branched) were synthesized by melt polycondensation of dimerized fatty acids and fatty diols and then cured with maleic anhydride-modified triglycerides (such as maleinized soybean oil) in the presence of the amidine catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene. The curing reaction of alcoholysis has the dual effect of chain extending/cross-linking the base polymers via creation of polymeric half-esters linkages while introducing carboxylic acid functions within the gel structure. We demonstrated how the adhesion properties can be finely tuned from molecular design and formulation of the network precursors and how the rheology and functionality of the coatings influence the adhesive bond formation and development. These renewable polyester adhesives proved to be suitable materials for pressure-sensitive adhesives applications with respect to adhesion strength, viscoelasticity, and functionality. In addition, the environmental benefits of such materials are briefly discussed.

Synthesis of Acrylic−Polyurethane Hybrid Latexes by Miniemulsion Polymerization and Their Pressure-Sensitive Adhesive Applications

The successful incorporation of a NCO-terminated polyurethane (PU) prepolymer in a hybrid miniemulsion is described with the purpose to develop waterborne, high solids, acrylic−PU hybrid nanoparticles to be used in pressure-sensitive adhesive (PSA) applications. To ensure efficient chemical incorporation of the reactive PU into the hybrid latex particles, the NCO moieties were reacted with 2-hydroxyethyl methacrylate (HEMA). The NCO−HEMA coupling reaction was thoroughly studied by conductimetry in order to control the extent of HEMA incorporation into the PU chains. The resulting HEMA-end-capped prepolymers were chain extended in situ with Bisphenol A (BPA) and polymerized with n-butyl acrylate, methyl methacrylate, and acrylic acid in the presence of small amounts of a chain transfer agent to form PU/acrylic particles. The amount of chain transfer agent, the ratio between HEMA and BPA, and the amount of PU were varied step by step to study their influence on the final film properties. The miniemulsions a...

Amphiphilic silicone copolymers for pressure sensitive adhesive applications

AbstractAmphiphilic copolymers of poly(dimethylsiloxane)‐poly(maleic anhydride‐vinyl ethyl ether) (PDMS/MA/VEE) were synthesized using a polydimethylsiloxane macroinitiator. The effect of these copolymers in the properties of a silicone pressure sensitive adhesive was evaluated. The addition of the copolymers resulted in lower peel strength (more than 50% reduction) from stainless steel panel while the moisture vapor transmission rate (MVTR) showed a significant increase (8× times higher) compared to the neat pressure sensitive adhesive. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis of benzocyclobutenone containing polymers for UV curable pressure sensitive adhesive applications

Synthesis of novel benzocyclobutenone (BCBO) containing polymers provide for residual-free pressure sensitive adhesives (PSA’s) that can be readily UV photo-crosslinked without the need for conventional photoinitiators.

Miniemulsion polymerization of acrylated methyl oleate for pressure sensitive adhesives

The focus of this work was to improve the aqueous emulsion polymerization of a highly water-insoluble monomer derived from plant oil, acrylated methyl oleate. Conventional emulsion polymerization requires excessive amounts of surfactant and long reaction time. Miniemulsion polymerization improved the polymerization significantly. Only a fraction of the surfactant and reaction time that was necessary in the conventional emulsion polymerization is required. The resulting polymers have properties comparable to petroleum-based polymers commonly used in pressure sensitive adhesive applications.