Influence of UV Polymerization Curing Conditions on Performance of Acrylic Pressure Sensitive Adhesives

Optical Adhesives and Screen Sealants for Foldable Displays: Analysis, Progress and Trends

The realm of flexible display devices, particularly centered around folding screen smartphones, is undergoing rapid advancements. As integral components, optical adhesives and screen sealants for these devices play pivotal roles in determining their overall performance. This paper provides a comprehensive overview of the evolution of display technology and display screens, delving into the critical function of optical adhesives within this framework. Notably, light-curing adhesives stand out for their paramount importance in display screen manufacturing, attributed to their swift curing capabilities. We synthesize the key research achievements and concomitant limitations pertaining to the characteristics of diverse flexible optical adhesives compositions over recent years. Furthermore, we delve into the influence of chemical modification techniques applied to various adhesive systems and the integration of physical doping fillers on enhancing the performance of screen sealants.

Material Characterization of Silicones for Additive Manufacturing

Three-dimensional printing is ideally suited to produce unique and complex shapes. In this study, the material properties of polysiloxanes, commonly named silicones, produced additively by two different methods, namely, multi-jet fusion (MJF) and material extrusion (ME) with liquid printing heads, are investigated. The chemical composition was compared via Fourier-transform infrared spectroscopy, evolved gas analysis mass spectrometry, pyrolysis gas chromatography coupled to mass spectrometry, and thermogravimetry (TGA). Density and low-temperature flexibility, mechanical properties and crosslink distance via freezing point depression were measured before and after post-treatment at elevated temperatures. The results show significant differences in the chemical composition, material properties, as well as surface quality of the tested products produced by the two manufacturing routes. Chemical analysis indicates that the investigated MJF materials contain acrylate moieties, possibly isobornyl acrylate linking branches. The hardness of the MJF samples is associated with crosslinking density. In the ashes after TGA, traces of phosphorus were found, which could originate from initiators or catalysts of the curing process. The ME materials contain fillers, most probably silica, that differ in their amount. It is possible that silica also plays a role in the processing to stabilize the extrusion strand. For the harder material, a higher crosslink density was found, which was supported also by the other tested properties. The MJF samples have smooth surfaces, while the ME samples show grooved surface structures typical for the material extrusion process. Post-treatment did not improve the material properties. In the MJF samples, significant color changes were observed.