Mechanistic studies in tackified acrylic emulsion pressure sensitive adhesives

Abstract

Twenty-three wt % aqueous tackifier dispersion based on glycerol ester abietic acid (T g ϭ 64°C, M w ϭ 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 m 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 (GЈ) and damping factor (tan ␦). 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 4ϫ lower than that of the neat acrylic PSA film.

Skin Development during the Film Formation of Waterborne Acrylic Pressure-Sensitive Adhesives Containing Tackifying Resin

“…[35] There has been only limited published research on the characteristics of waterborne, tackified PSAs. [9,17,35,36] The work of Tobing and Klein [36] is particularly significant because it considers the mechanism by which tackifiers improve waterborne PSA performance. These authors commented, however, that the Published in Journal of Adhesion (2006) 82(3): pp 217-238 5 development of tackified PSA technology was being limited by a poor understanding of the film formation process.…”

A Comparison of Tackified, Miniemulsion Core−Shell Acrylic Latex Films with Corresponding Particle-Blend Films: Structure−Property Relationships

“…Tobing and Klein 25 elucidated the effects of TR on the viscoelasticity and the chain entanglement network of waterborne PSAs. Mallégol et al found that the addition of TR to an acrylic PSA latex led to better particle coalescence, because the tackifier acted as a compatibilizer between the acrylic and the serum phase.…”

“…13 In acrylic polymers, its primary role is to increase the viscoelastic dissipative properties (loss tangent) at room temperature. 2,25,26 Further research is especially required in tackified wb systems, because the processing of blends of latex and TR is a source of numerous problems. Water-dispersed TR contains a substantial amount of poorly-characterized surfactants and dispersants, which can affect the colloidal stability and the coatability of the latex into which it is blended.…”

Butyl Acrylate/Vinyl Acetate Emulsion‐Based Pressure‐Sensitive Adhesives: Empirical Modelling of Final Properties

“…Gel content was determined using the membrane partitioning method (Tobing and Klein, 2001a). A known amount of sample (approximately 0.1 g of dried polymer) was heat sealed between two polytetrafl uoroethylene membranes (pore size 0.2 μm, 47 mm diameter).…”