The Effect of Type-I Photoinitiators on the Kinetics of the UV-Induced Cotelomerization Process of Acrylate Monomers and Properties of Obtained Pressure-Sensitive Adhesives

Abstract

A new method of solvent-free acrylic pressure-sensitive adhesives (PSAs) based on UV-induced cotelomerization products was presented. The key acrylic monomers (i.e., n-butyl acrylate and acrylic acid) with copolymerizable photoinitiator 4-acrylooxybenzophenone in the presence of a selected chain transfer agent (tetrabromomethane, TBM) were used in the UV-cotelomerization process. Moreover, two kinds of UV-photoinitiators (α-hydroxyalkylphenones, HPs and acylphosphine oxides, APOs) were tested. Photo-DSC, viscosity, thermogravimetric, and GPC measurements for cotelomers were performed. The kinetics study revealed that the systems with APOs, especially Omnirad 819 and Omnirad TPO, were characterized by a much higher reaction rate and greater initiation efficiency than HPs systems were. Additionally, the APO-based syrups exhibited a higher solid content (ca. 60–96 wt%), a higher dynamic viscosity (5–185 Pa·s), but slightly lower molecular weights (Mn and Mw) compared to HP syrups. However, better self-adhesive features (i.e., adhesion and tack) were observed for PSAs based on cotelomers syrups obtained using APOs with lower solid contents (55–80 wt%). It was found that as the solids content (i.e., monomers conversion) increased the adhesion, the tack and glass transition temperature decreased and the type and amount of photoinitiator had no effect on polydispersity. Most of the obtained PSAs were characterized by excellent cohesion, both at 20 °C and 70 °C.

Asphaltene-Stabilized Polyisobutylene Pressure-Sensitive Adhesives for Ultraviolet Protection and Surface Bonding

“…PSAs have long viability, do not harden over time, and do not dry out; they are widely applied in industry, everyday life, and medicine [ 31 ]. Poly(ethylene-vinyl acetate) [ 32 ], polyurethanes [ 33 ], polyacrylates [ 34 ], polyvinylpyrrolidone [ 35 ], and some other polymers [ 36 ] are widely used as PSA polymer matrices. However, only PSAs based on polyisobutylene (PIB) are characterized by a combination of high stickiness, good oxidative and thermal stability, high availability, low price, and nontoxicity; but their problem is the propensity for irreversible distortion under the influence of small stresses—cold flow [ 37 ].…”

Recent progress in the development of highly active dyeing photoinitiators based on 1,3-bis(p-substituted phenylamino)squaraines for radical polymerization of acrylates

“…The forecasts for the coming years indicate that the coating and biomaterials industries will continue to grow rapidly, growth which will translate into the photoinitiators area. 25–28…”

“…The forecasts for the coming years indicate that the coating and biomaterials industries will continue to grow rapidly, growth which will translate into the photoinitiators area. [25][26][27][28] In recent years, enormous progress in the development of new photoinitiators operating not only under ultraviolet, but above all in the visible range of the spectrum, has occurred. It manifests in numerous publications on innovative systems for various types of polymerization.…”

Technologies for Joining and Forming Thin-Walled Structures in the Construction of Transportation Vehicles

“…The last two articles published in SI concern a modern and environmentally friendly method of obtaining adhesive binders for pressure-sensitive adhesives [ 33 , 34 ]. It has been proven that the light-induced telomerization and subsequent photocrosslinking of acrylate monomers is a particularly convenient method of obtaining thin adhesive films, with further potential applications in the automotive industry.…”

“…It was found that an increase in the acrylic acid content causes significant changes in the reaction rate, monomer transformation, and the solid content in prepolymers and their viscosity, as well as in adhesion and cohesion [ 33 ]. In turn, in the second paper, the key factors determining the properties of solvent-free acrylic pressure-sensitive adhesives were indicated [ 34 ].…”