Abstract
A new environmentally friendly method of photoreactive pressure-sensitive adhesives (PSAs) preparation was demonstrated. PSAs based on n-butyl acrylate (BA), acrylic acid (AA) and 4-acryloyloxy benxophenone (ABP) were prepared via the UV-induced cotelomerization process in the presence of a radical photoinitiator (acylphosphine oxide) and telogen (tetrabromomethane). Hydroxyterminated polybutadiene was used as a crosslinking agent. Influence of AA concentration (0–10 wt %) on kinetics of the cotelomerization process was investigated using a photodifferential scanning calorimetry method, selected physicochemical features of obtained photoreactive BA/AA/ABP cotelomers (molecular masses, polydispersity, monomers conversion and dynamic viscosity) and self-adhesive properties of obtained PSAs (adhesion, tack and cohesion) were studied, as well. It turned out that AA content is the important factor that influences monomers conversion (thereby the volatile parts content in prepolymer) and PSAs’ properties. As the acrylic acid content increases, the reaction rate increases, but the total monomers conversion and the solid content of the prepolymer decreases. Additionally, the adhesion and cohesion of PSAs were grown up, and their tackiness decreased. However, the AA content has no effect on molecular weights (Mw and Mn) and polydispersity (c.a. 1.5) of photoreactive cotelomers. The optimal AA content necessary to obtain a prepolymer with low volatile parts content and good PSA properties was determined.
Highlights
Pressure-sensitive adhesives (PSAs) are ubiquitous and exceptional materials
The first formulations based on polybutyl acrylate and polyiso-butyl ether did not have the required tack and cohesive strength
In the 1950s, it was found that the performance of pressure-sensitive adhesives (PSAs) could be substantially improved by adding certain amounts of acrylic acid [4]
Summary
Pressure-sensitive adhesives (PSAs) are ubiquitous and exceptional materials. They are used in most consumer applications and many industrial assembly operations. PSAs are unique because they create a strong bond with the surface with only finger pressure and they do not require activation (e.g., heat or water) [1,2]. Natural rubber [poly(1,4-cis-isoprene)] was used as base material for PSAs [3]. Since 1929 it is known that alkyl acrylate ester had the characteristic tack of PSAs. the first formulations based on polybutyl acrylate and polyiso-butyl ether did not have the required tack and cohesive strength. Today PSAs are made from a great variety of elastomers, i.e., natural, butyl, nitrile, styrene butadiene rubbers and polyurethanes, polyether, ethylene-vinyl acetate copolymers (EVA) and silicones [5]. Acrylic PSAs consists mainly of a “soft” monomer with a low glass transition temperature
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