UV-curable monomer

Scheme 52 Preparation of UV-curable monomers from glycerol chloroformate-carbonate.

Taki, K. Okumura, S., Production of Porous Polymer Foams with Unimodal or Bimodal Pore-Size Distributions via Depressurization and Photopolymerization-Induced Bubble Nucleation in Low-Viscosity UV-Curable Monomer/High Pressure CO Solutions. Macromolecules 2010,43, 9899-9907. 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

Commonly used monomers for UV curing include acrylates (7), styrene/unsaturated polyesters (8,9), and thiol-ene compositions (10-12). Currently, acrylate-functional systems constitute a major share of the UV curable polymers market, mainly due to their rapid curing via free radical chain polymerization. 

Fig. 21 Representative microfluidic device and resulting data from ATRP on a chip a image of a microfluidic device (dimensions 25 mm x 75 mm) fabricated from UV curable thiolene resin between two glass slides b reaction data for ATRP of HPMA synthesized on a chip showing the correlation of flow rate (or residence time) to reaction time and resulting conversion of monomer (M) to polymer (ln([M]o/[M]) c comparison of number average molecular mass (M ) and poly-dispersity for -butyl acrylate prepared in a traditional round bottom flask ( Flask ) and on a chip ( CRP Chip ). (Reproduced with permission from [102])...

The most widely used UV curable radical-initiated systems are based on acrylate unsaturation with the general formula H2C = CR-COOR (if R = H, the monomer is an acrylatel if R = CH3, it is a methacrylate). Methacrylates are less reactive than acrylates,but are less toxic and cause less skin irritation than acrylates. 

Polyurethane hydrogels derived from UV curable urethane prepolymer and hydrophilic monomers were prepared and their properties were evaluated. The urethane prepolymer used in this study contained well-defined hard segments centered with a polyether-based soft segment and end-capped with methacrylate groups. The hydrophilic monomers studied were 2-hydroxyethyl methacrylate (HEMA), N-vinyl pyrrolidone, and glycerol methacrylate. Methacryloxypropyl tris(trimethysiloxy) silane (TRIS) was also used in some cases to modify properties. All compositions were UV... 

The generation of a protonic acid (HX) is responsible for the initiation of cationic polymerization. Various monomers are polymerized by sulfonium photoinitiators. Especially this system has been shown to be potentially useful for UV curable coatings of metal and plastics with epoxy resins. 

The majority of the monomers and oligomers used in UV curable inkjet ink formulations are acrylates of varying functionalities, although occasionally materials such as unsaturated polyester resins are used as well. Figure 2 shows examples of the acrylate moiety. Acrylates are skin sensitizers and should be handled with caution. 

Table 2 lists only four raw materials, if the photoinitiator package is considered to be one material. However, it will have all the critical properties of a UV curable inkjet ink — low viscosity due to the monomer selection and the abUity to polymerize because of the photoinitiators included. Also, the use of a pentafunctional acrylate will... 

Formulating UV curable inkjet inks for piezoelectric print heads requires technical knowledge as well as creativity to meet the strenuous requirements that the print markets, particularly the industrial printing arena, demand. The basic components found in most inkjet ink formulas include monomers and oligomers, pigments and dyes, photoinitiators, and additives. 

One way of minimizing the detrimental effect caused by chain transfer on decreasing molecular weight and crosslink density of UV curable coatings has been successfully applied [115] by using copolymerizable methacrylic monomers containing the tertiary amine moiety as components of reactive acrylic formulations in the presence of benzoin ether derivatives. 

Our interest in the photochemistry of benzoin ethers was prompted by two major reasons (1) a discrepancy existed between recent mechanistic studies on the photochemistry of benzoin ethers and earlier reports on the benzoin ether photo-initiated polymerization of reactive monomers, and (2) the extensive, commercial utilization of benzoin ethers as photoinitiators in uv curable coatings and printing inks warranted further investigation of this discrepancy. 

Photosensltlzers or Photolnltlators. The primary component In the UV-curable coating system Is the photosensitizer or photolnltlator (a light sensitive catalyst that upon absorption of energy results In a free radical species that can initiate acrylic monomer polymerization). C2.)... 

After light absorption by the photocatalyst the next step is photoproduction of free radicals that initiate polymerization of the acrylate unsaturated monomers, oligomers, and polymers contained in the UV-curable coating system. 

Photopolymer systems are photocurable resins incorporating reactive liquid monomers, photoinitiators, chemical modihers and hhers. Typically stereolithography utilizes UV radiation, so UV-curable systems are used. Free-radical-photopolymerizable acrylate systems were originally used however, newer cationic epoxy-resin and vinyl ether systems (based on iodinium- or sulfonium-salt cationic initiators) are now being utilized. 

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