Control of structure and tack properties of acrylic pressure‐sensitive adhesives designed by a polymerization process

Abstract

Free radical emulsion polymerization of methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA) results in the synthesis of pressure-sensitive adhesives (PSAs) with good tack properties. Management of both the copolymer composition and the polymerization process allows one to control the behavior of the PSA. Semicontinuous (SC) processes create polymer particles whose instantaneous composition is close to that of the feed particle The SC Mixture process (continuous feeding with comonomer blends) affords nearly homogeneous latex particles and PSA films. The SC Gradient process (separate feedings at inversely varying rates) affords heterogeneous particles and films. The Batch process leads to somewhat heterogeneous films, but the hard (MMA-rich) microdomains are made compatible with their soft (EHA-rich) matrix because of the assumed formation of tapered-type copolymers. Tack measurements indicate the importance of the particle and film structures. Too much hardness or softness leads to unacceptable lacks of adhesion and cohesion, respectively. Homogeneous structures prove adequate, but their tack properties collapse with rising temperature. Heterogeneous structures, with extensive phase segregation, prove unsatisfactory because they lack adhesion and cohesion. Finally, the association of well-balanced composition and compatible heterogeneity is the criterion for suitable PSA behavior.

Design of Nanostructured Waterborne Adhesives with Improved Shear Resistance

“…The influence of particle morphology on adhesive performance has already been studied by Aymonier et al20–22 However, no special effort to control molecular weight and gel fraction of both phases was made, and in that case not much improvement was obtained using a heterogeneous morphology or a gradient composition compared to a homogeneous one. The heterogeneous structure of Aymonier et al21 shows e.g., a lack of adhesion and cohesion probably because the composition of each phase, outer and within the particle, is not optimized for this type of structure.…”

“…The influence of particle morphology on adhesive performance has already been studied by Aymonier et al20–22 However, no special effort to control molecular weight and gel fraction of both phases was made, and in that case not much improvement was obtained using a heterogeneous morphology or a gradient composition compared to a homogeneous one. The heterogeneous structure of Aymonier et al21 shows e.g., a lack of adhesion and cohesion probably because the composition of each phase, outer and within the particle, is not optimized for this type of structure. More recently Deplace, Foster and coworkers have explored this concept of heterogeneous particle in more detail and in addition to the structure of the particle itself,19, 23–25 have focused also on the synergy between particle structure and polymer architecture and saw a clear improvement in macroscopic adhesive properties.…”

The influence of the polymerization on properties of an ethylacrylate/2-ethyl hexylacrylate pressure-sensitive adhesive suspension

“…The effect of different composition profiles of copolymer latex particles derived from 2-EHA/MA with similar MWDs on the adhesive properties were investigated by Laureau et al [13]. The effect of methyl methacrylate (MMA) on the tack in MMA/2-EHA copolymers for emulsion-based PSA was reported by Aymonier et al [14]. The possibility of tuning the adhesion properties through different holding tank temperatures, different types of chain transfer agents and the post-polymerization process were studied by Alarcia et al [15].…”

Miscibility and tack of blends of poly (vinylpyrrolidone)/acrylic pressure-sensitive adhesive

“…It was believed that no tackifier is needed in acrylic PSA because it can easily produce polymers of various properties by combining different kinds of comonomers. However, recently, tackifier resins are often added to the formulation of acrylic PSAs to modify the practical performances [4].…”