A cartonboard package is often sealed and closed with an adhesive – either a hot-melt adhesive (adhesives that are applied in a molten state on the cartonboard) or a dispersion adhesive (adhesives that are applied as water-based dispersions). This thesis focuses on the process of hot-melt gluing, and how material properties and process conditions affect the performance of the adhesive joint. Requirements vary depending on how the package is to be used. A package that is only supposed to protect the product during transport differs from one that is supposed to attract consumers and facilitate their use of the product. If a package has been opened, due to external or internal forces that cause a fracture in the adhesive joint, the consumer may choose another package instead. A fracture of the adhesive joint may occur in several different ways; for example, a cohesive fracture in the adhesive, an interfacial fracture between the adhesive and one of the cartonboard surfaces, and a cohesive fracture in the cartonboard. The traditional way of testing the adhesive joint is to subjectively evaluate the fibre tear after manually tearing the joint apart. The primary interest of this study has been to find an objective method that can characterise the adhesive joint – that is, its strength and joint characteristics. The work has principally concentrated on physical experiments where the Y-peel method has been evaluated and further developed, including the construction of a laboratory adhesive applicator. Adhesive joint failure is analysed and correlated to the force-elongation curve during Y-peel testing in order to explore various mechanisms of the failure. The force versus elongation curves are transformed into a force versus inelastic deformation curve for the adhesive joint. The inelastic deformation of the adhesive joint is defined as the inelastic opening of the adhesive joint perpendicular to the cartonboard surface. The dissipative descending energy has been used to characterise the adhesive joint. High descending dissipative energy showed high resistance against final failure of the joint. This correlates very well with the manual fibre-tear test. Characteristic force-elongation curves in Y-peel testing – that is, the shape of the curve – have been analysed, and four main failure modes have been identified. The finite element method has been used to predict mechanical behaviour in the ascending part of the force-elongation curve. When it comes to local behaviour, a high stiffness adhesive results in bending behaviour while a low results in shearing, but on a global scale, no big difference was detected on the ascending part of the force-elongation curve. The new laboratory adhesive applicator and finite element method can be used to objectively design the interaction between the adhesive and the cartonboard for a specific application. This can be achieved by modifying the cartonboard, the adhesive or the process parameters.

Yes / A composite silicone skin adhesive material was designed to improve its water vapor permeability to offer advantages to wearer comfort compared to existing skin adhesive dressings available (including perforated silicone and hydrocolloid products). The chemical and mechanical properties of this novel dressing were analyzed to show that it has a high creep compliance, offering anisotropic elasticity that is likely to place less stress on the skin. A participant study was carried out in which 31 participants wore a novel silicone skin adhesive (Sil2) and a hydrocolloid competitor and were monitored for physiological response to the dressings. Trans-epidermal water loss (TEWL) was measured pre- and postwear to determine impairment of skin barrier function. Sil2 exhibited a higher vapor permeability than the hydrocolloid dressings during wear. Peel strength measurements and dye counter staining of the removed dressings showed that the hydrocolloid had a higher adhesion to the participants’ skin, resulting in a greater removal of proteins from the stratum corneum and a higher pain rating from participants on removal. Once the dressings were removed, TEWL of the participants skin beneath the Sil2 was close to normal in comparison to the hydrocolloid dressings that showed an increase in skin TEWL, indicating that the skin had been highly occluded. Analysis of the skin immediately after removal showed a higher incidence of erythema following application of hydrocolloid dressings (>60%) compared to Sil2, ( / T.S. received partial funding to study skin adhesive materials from a Medical Research Council Confidence in Concept grant obtained by John Bridgeman at the University of Bradford (MC_PC_19030). Initial formulation and characterization work benchmarking the Sil2 material was funded in part by Trio Healthcare Ltd., who have had no role in the analysis or interpretation of the data presented. All data was obtained independently by staff at the University of Bradford. We also wish to thank the Royal Society of Chemistry for funding Edward Dyson’s position as a research technician via a Research Enablement Grant (E21-8346952505).

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