Epoxy structural adhesives have strong adhesion, minimal shrinkage and high thermal and chemical resistance. However, despite these excellent properties, their high-energy impact resistance should be improved to satisfy the increasing demands of the automotive industry. For this reason, we used four types of silica nanoparticles with different surface groups, such as polydimethylsiloxane (PDMS), hydroxyl, epoxy and amine groups, as toughening agents and examined their effect on the glass transition temperature (Tg), crosslinking density and phase separation of epoxy structural adhesives. High-energy impact resistance, mode I fracture toughness and lap shear strength were also measured to explain the effect of surface functional groups. Silica nanoparticles with reactive functional groups increased the mode I fracture toughness of epoxy structural adhesives without sacrificing the crosslinking density. Although the mode I fracture toughness of epoxy structural adhesives could not clearly show the effect of surface functional groups, the dynamic resistance to cleavage obtained by impact wedge-peel tests showed quite different values. At a 0.3 vol% content, epoxy-functionalized silica nanoparticles induced the highest value (40.2 N/mm) compared to PDMS (34.1 N/m), hydroxyl (34.9 N/mm), and amine (36.1 N/m). All of these values were significantly higher than those of pristine epoxy structural adhesive (27.7 N/mm).

Acrylic pressure-sensitive adhesive (acrylic PSA) has advantages such as high adhesion, low cost, and high light transmittance, but it has a low adhesion to low-surface-energy substrates and low thermal stability. To solve these problems, PSA was modified with low surface energy moieties and crosslinked by UV curing. In this study, a polydimethylsiloxane (PDMS) structure with a low surface energy and good thermal properties was introduced into PSA through grafting polymerization to compensate for the disadvantages of acrylic PSA. PDMSgrafted acrylic PSAs (PGPs) were synthesized by grafting through method using macromonomers with PDMS of three different lengths. They showed improved loop tack and 180 peel strength values on polypropylene, a low-surface-energy substrate. However, when a long PDMS-based macromonomer (M w $ 5000) was used, phase separation was observed even at a low concentration, and the degree of improvement was decreased. The peel strength of PGPs significantly changed with dwelling time. As the surface energy difference between the substrate and PSA increased, the peel strength increased dramatically with dwelling time. 90 peel strengths measured with varying temperature (25-100 C) showed that a long PDMS chain was most effective in improving the thermal stability of the acrylic PSA by its own domains.

Photoreactive pressure-sensitive adhesives (PSAs) were prepared by grafting mono- or difunctional photoreactive monomers onto acrylic PSA, and their adhesion properties were evaluated before and after UV curing for application as dicing tape.

Correction for ‘Preparation of UV-curable PSAs by grafting isocyanate-terminated photoreactive monomers and the effect of the functionality of grafted monomers on the debonding properties on Si wafers’ by Hee-Woong Park et al., RSC Adv., 2023, 13, 11874–11882, https://doi.org/10.1039/D3RA00398A.