The photooxidative sensitization of bis(p-substituted diphenyl)iodonium salts in the radical polymerization of acrylates

The ability of two-component dyeing photoinitiating systems for the radical polymerization of 1,6-hexanediol diacrylate (HDDA) and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate (TMPTA) is presented. The systems under study comprised a hemicyanine dye as a sensitizer and iodonium salts that played a role of a coinitiator. The kinetic parameters of the polymerization reaction, such as the rate of polymerization (R_p) and the degree of conversion of monomer (C_%), were estimated. The thermodynamic feasibility of an electron transfer process in the systems studied was verified and calculated using the Rehm–Weller equation. It was found that a benzoxazole derivative in the presence of iodonium salts effectively initiated the polymerization of acrylate monomers. The polymerization rates of about 10⁻⁷ s⁻¹ and the degree of conversion of acrylate groups from 20% to 50% were observed. The effects of photoinitiator structures on the initiating ability and spectroscopic properties of sensitizers are described in this article.

The ability of two-component dyeing photoinitiating systems for the radical polymerization of 1,6-hexanediol diacrylate (HDDA) and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate (TMPTA) is presented.     

New BODIPY Dyes Based on Benzoxazole as Photosensitizers in Radical Polymerization of Acrylate Monomers

A series of 2-phenacylbenzoxazole difluoroboranes named BODIPY dyes (1–8) was designed and applied as photosensitizers (PS) for radical photopolymerization of acrylate monomer. The light absorption within the ultraviolet-visible (UV–Vis) range (λ_max = 350–410 nm; ε_max = 23,000–42,500 M⁻¹cm⁻¹), that is strongly influenced by the substituents on the C3 and C4 atoms of phenyl ring, matched the emission of the Omnicure S2000 light within 320–500 nm. The photosensitizer possess fluorescence quantum yield from about 0.005 to 0.99. The 2-phenacylbenzoxazole difluoroboranes, together with borate salt (Bor), iodonium salt (Iod) or pyridinium salt (Pyr) acting as co-initiators, can generate active radicals upon the irradiation with a High Pressure Mercury Lamp which initiates a high-performance UV–Vis light-induced radical polymerization at 320–500 nm. The polymers obtained are characterized by strong photoluminescence. It was found that the type of radical generator (co-initiator) has a significant effect on the kinetic of radical polymerization of acrylate monomer. Moreover, the chemical structure of the BODIPY dyes does not influence the photoinitiating ability of the photoinitiator. The concentration of the photoinitiating system affects the photoinitiating performance. These 2-phenacylbenzoxazole difluoroborane-based photoinitiating systems have promising applications in UV–Vis-light induced polymerization.     

Preparation and Characterization of Acrylic Pressure-Sensitive Adhesives Crosslinked with UV Radiation-Influence of Monomer Composition on Adhesive Properties

In this study, syntheses of acrylate copolymers were performed based on the monomers butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), and acrylic acid (AA) and the second-type unsaturated photoinitiator 4-acryloyloxybenzophenone (ABP). The structure of the obtained copolymers was confirmed via FT-IR spectroscopic analysis, and the viscosity and the content of non-volatile substances were determined. The adhesive films were then coated and cross-linked using ultraviolet radiation in the UV-C range at various doses (5–50 mJ/cm²). Due to the dependence of the self-adhesive properties of the adhesive layer on the basis weight, various basis weights of the layer in the range of 30–120 g/m² were tested. Finally, the self-adhesive properties were assessed: tack, peel adhesion, shear strength (cohesion) at 20 °C and 70 °C, as well as the SAFT test and shrinkage. The aim of the study was to determine the effect of the type of monomer used, the dose of ultraviolet radiation, and the basis weight on the self-adhesive and usable properties of the obtained self-adhesive tapes.     

Numerical and Experimental Analysis of Titanium Sheet Forming for Medical Instrument Parts

The paper analyses the forming of the surgical instrument handles made of Grade 2 titanium sheets. Sheet metal forming is a technology ensuring high strength and light weight of products. Replacing stainless steels with titanium further reduces instrument weight and additionally provides the required resistance to corrosive environments typical for surgeries. The low instrument weight is important to prevent fatigue of surgeons and allow them to maintain high operational accuracy during long term surgeries. The numerical analysis of the technological process was performed in order to adapt it to forming tool handles using titanium sheets instead of steel sheets. The numerical calculations were experimentally verified. It was found that, in the case of titanium handles, it is necessary to use a blank holder in the first forming operation to eliminate sheet wrinkling in the flange area. The shape and dimensional accuracy of the drawn part after trimming were high enough and the 4th forming operation became unnecessary. Moreover, the process modification included lubrication using rapeseed oil with the addition of boric acid, which effectively prevents the galling of titanium on the working surfaces of the steel tools and ensures a more uniform distribution of plastic strains in the drawn part.