Abstract
Polyacrylic pressure-sensitive adhesives (PSAs) based on butyl acrylate (BA), 2-hydroxyethyl acrylate (HEA), and acrylic acid (AA) were prepared by a bulk polymerization process triggered by a radical photoinitiator under UV irradiation and UV-crosslinking. 1,6-Hexanediol diacrylate (HDDA) with difunctional groups was introduced into the PSAs to modify semi-interpenetrating network structures. The effect of HDDA content on the pressure-sensitive performance was comprehensively tested. The viscosity of the prepolymer was measured by a rotational viscometer. Prepolymers obtained by a photoinduced process and UV crosslinking process were confirmed via Fourier transform infrared spectroscopy (FTIR). All double bonds participated in the copolymerization without any remaining monomers, which reflected the concept of green environmental protection. Gel content in the crosslinked portion was examined by Soxhlet extraction, whilst the soluble molecular weight of PSAs was characterized by gel permeation chromatography (GPC). The viscoelastic properties of polymer films were determined by dynamic mechanical analysis (DMA). The Tg value and storage modulus (G′) of the PSAs were enhanced with the addition of HDDA. Moreover, three fundamental adhesive properties, i.e. loop tack force, peel force and shear strength of PSAs, were measured. The results showed that UV crosslinking technology achieved a good balance of the three forces with excellent pressure-sensitive properties.
Highlights
Pressure-sensitive adhesives (PSAs) are viscoelastic materials that can be bonded to a wide range of solid surfaces, such as metallic and non-metallic surfaces, using slight pressure with a short contact time.[1]
Acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) available from Shanghai Macklin were passed through a column of activated aluminum oxide to remove the inhibitors. 2-Hydroxy-2-methyl-1-phenylpropanone (1173) supplied by Tianjin Jiuri Chemical Co was used as the initiator of UV-crosslinking process
The spectra of prepolymers synthesized by UV LED radiation and a er UV crosslinking process were obtained via Fourier transform infrared spectroscopy (Vector-22, Bruck Company, Germany)
Summary
Pressure-sensitive adhesives (PSAs) are viscoelastic materials that can be bonded to a wide range of solid surfaces, such as metallic and non-metallic surfaces, using slight pressure with a short contact time.[1]. Among them, solventbased polyacrylic PSAs account for 50%, water-based polyacrylic PSAs account for 40%, and less than 10% of the solvent-free polyacrylic PSAs. Polyacrylic PSAs prepared by solution polymerization or emulsion polymerization have a reaction time of several hours, resulting in high energy consumption, and contain volatile organic compounds (VOCs) leading to increase costs for post-treatment and environmental pollution problems.[6] On the contrary, UV technology can address these issues. The mechanism for the formation semi-IPNs is that the network structures of polymers pack linear backbones tightly.[16] research on preparing acrylic prepolymer and polyacrylic PSAs both using UV irradiation technologies is scarce and not widely reported. Emphasis was placed on the effects of different contents of cross-linking agents on the molecular structures and pressure-sensitive properties, and to achieve a good balance between adhesion and cohesion
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