Epoxy-Based Structural Self-Adhesive Tapes Modified with Acrylic Syrups Prepared via a Free Radical Photopolymerization Process

Abstract

New modifiers (i.e., acrylic syrups; ASs) of epoxy-resin-based thermally curable structural self-adhesive tapes (SATs) were prepared via a free radical bulk polymerization (FRBP) of n-butyl acrylate, butyl methacrylate, glycidyl methacrylate, and hydroxybutyl acrylate. In the process, two kinds of UV-photoinitiators (i.e., monoacylphosphine oxide/Omnirad TPO and bisacylphosphine oxide/Omnirad 819) and various mixing speed of the monomers mixture (200–1000 rpm) were applied. The TPO-based syrups exhibited a lower copolymers content (10–24 wt%), dynamic viscosity (<0.1 Pa·s), molecular weights (Mn and Mw, and polydispersity (1.9–2.5) than these with Omnirad 819. Additionally, the higher mixing speed significantly reduced monomers conversion and viscosity of ASs as well as molecular weights of the acrylate copolymers. These parameters influenced the properties of thermally uncured (e.g., adhesion) and thermally cured SATs (shear strength of aluminum/SAT/aluminum overlap joints). Better self-adhesive features were observed for SATs-TPO (based on ASs with lower monomers conversion, Mn and Mw); however, a slightly higher shear strength was noted for the thermally cured SAT-819 (ASs with higher monomers conversion, Mn and Mw). An impact of polydispersity of the acrylate copolymers as well as crosslinking degree of thermally cured SATs on the mechanical strength was also revealed.

Influence of Methacrylate and Vinyl Monomers on Radical Bulk Photopolymerization Process and Properties of Epoxy-Acrylate Structural Adhesives

“…One interesting approach seems to be the synthesis of ARs by the free-radical bulk photopolymerization process (FRBP), which is a new approach in mass polymerization. Such a method does not only allow the exclusion of organic solvents but also saves time and energy (it does not require an elevated temperature to decompose the initiator), especially since it can be carried out using conventional LEDs [ 16 ]. FRBP allows products called polymer syrups (PSs) to be obtained, which are equivalent to polymer resins.…”

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

“…Among the described photopolymerization processes, two general types can be distinguished, namely processes taking place in thin or thick layers. Relatively few publications have dealt with bulk photopolymerization processes with mechanically mixed monomers [ 18 , 30 ]. To the best of the authors’ knowledge, this publication is the first to describe the effect of the type (and amount) of radical photoinitiator on the bulk photo-cotelomerization process of acrylic monomers.…”

Novel Copper Complexes as Visible Light Photoinitiators for the Synthesis of Interpenetrating Polymer Networks (IPNs)

“…The elaboration of polymers by photochemical means, such as free radical photopolymerization (FRP) and cationic photopolymerization (CP), have been mainly based on the use of metal-free organic dyes and photoinitiators at the industrial and academic levels [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], and these synthetic processes (FRP and CP) are widely used in different fields, e.g., dentistry [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], adhesives [ 24 , 25 , 26 , 27 , 28 ], coatings [ 29 , 30 , 31 , 32 , 33 ], composites [ 34 ], medicine [ 35 , 36 , 37 , 38 , 39 , 40 ], direct laser write, 3D and 4D printing [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ], etc. On the other hand, organometallic compounds are not really used in industry; in other words, manufac...…”