Synthesis and Properties of Silicone-Acrylic Pressure-Sensitive Adhesives for Low Surface Energy Substrates

Abstract

Recently IT industry shows IoT (Internet of Things) trends such as smart electronic devices, wearable devices such as smart band, mobile-based fusion technology such as convergence of mobile-based financial service development. IT device becomes more compact and slim device and needs to be low cost.

IoT IT device needs to be flexibility, slim, compact appearance. So many slim electric parts are assembled by physical bonds such as bolts or chemical bond such as adhesive (including pressure-sensitive adhesive). Silicone materials are good substrates that have good heat spread, flexibility, anti-thermal shock ability, so many wearable devices uses silicone material for the flexible substrate. But silicone has low surface energy and flexible surface, so many adhesive or pressure sensitive adhesive have a difficult to bond. So, although silicone adhesive or pressure sensitive adhesive is expensive, for the bond to low surface energy material, the silicone adhesive or pressure sensitive adhesive is used. In particular, pressure sensitive adhesive using silicone has to use the expensive fluorine-release films, so silicone pressure sensitive adhesive used on a limited basis.

In some papers, modified acrylic PSAs can be applied for a bond to low surface energy materials such as silicone. Modified acrylic PSA has main acrylic backbone such as 2-EHA (2-ethylhexyl acrylate), BA (butyl acrylate), AA (acrylic acid) with some low molecular functional additives such as PDMS crosslinking, fluorinated coupling agent or silicone modified branch structure.

In this study, modified acrylic PSA was synthesized by solution polymerization using PDMS-based macroinitiator (MAI, macro azo-based initiator). The MAI-acrylic PSAs used in this study were acrylic copolymers with different compositions. The model copolymers (poly-MAI-2EHA-IBA-AA copolymer) were synthesized by radical solution polymerization in a semi-batch procedure at 80℃/6 hrs in a solvent (EA, ethylene acetate). To monitor the synthesis of polymerization, FTIR, Gel fraction, GPC, PSA performances such as peel strength, probe tack, shear adhesion were evaluated. For surface analysis, Raman spectroscopy, XPS was tested.

Based on this study, suitable process parameters and conditions are proposed for the synthesis of modified acrylic PSAs and optimized their adhesion performances on low surface energy substrates.