Cross photocuring

For aqueous inks, the resins are water- or alkali-soluble or dispersible and the solvent is mosdy water containing sufficient alcohol (as much as 25%) to help solubilize the resin. To keep the alkah-soluble resin in solution, pH must be maintained at the correct level. Advances include the development of uv inks. These are high viscosity inks that require no drying but are photocurable by uv radiation. In these formulations, the solvent is replaced by monomers and photoinitiators that can be cross-linked by exposure to uv radiation. The advantage of this system is the complete elimination of volatile organic compounds (VOC) as components of the system and better halftone print quaUty. Aqueous and uv inks are becoming more popular as environmental pressure to reduce VOC increases. 

The nanocomposite of cross-linked ESO and supramolecular (/ )-12-hydroxystrearic acid (HSA) nanofibre was obtained by photo curing ESO/ HSA (10/1 weight ratio) at 100°C. The study revealed that dendritic clusters of HSA nanofibres are formed in the cross-linked ESO matrix. A thermal transition from the mesophase composed of supramolecular nanofibres to the isotropic state was observed at 67°C (A// = 22.6 Jg HSA), while the of crystalline HSA is 11.1°C (AH = 159 J g HSA).The tensile strength at 20°C of the ESO/HSA was 80% higher than that of photocured ESO without HSA. ... 

The group of Nagata incorporated UV-curable moieties directly into the main chain of the related polymers [41-43]. Thus, photocurable, biodegradable multiblock SMPs were prepared by polycondensation from PCL diol, PEG, and 5-cinnamoyloxyisophthalic acid [41]. The latter compounds acted as UV cross-linker without any photoinitiator. The semicrystalline photosets exhibited Tg----60 C, and in the range 35-47°C. Both and R values were... 

The authors successfully prepared chemically cross-linked temperature-responsive electrospun nanofibers by thermal curing [llj. As a member of the NIPAAm family, N-hydroxymethylacrylamide (HMAAm) was copolymerized with NIPAAm by free-radical copolymerization because temperature-responsive HMAAm can be cross-linked by self-condensation at high temperatures (above 110°C). As a result of cross-linking, very stable nanofibers in aqueous solution were obtained and manipulated as a bulk material. By extension of the above-mentioned examples, the authors successfully prepared temperature-responsive electrospun nanofibers by photocuring [12]. The temperature-responsive nanofiber mats were prepared using the copolymers NIPAAm and 2-carboxyisopropylacrylamide conjugated to 4-aminobenzophenone, a photoinitiator. The crosslinked temperature-responsive nanofibers were obtained by UV irradiation for 30 min (Fig. 5.4.3). Chemically cross-linked nanofibers were also reported by... 

Photopolymers These are photoinitiated and photo-cross-linked polymers e.g., photoresists, printing inks, can coatings, etc. Fouassier J-P (1995) Photoinitiation, photopolymerization and photocuring. Hanser-Gardner Publications, New York. Leach RH, Pierce RJ, Hickman EP, Mackenzie MJ, Smith HG (eds) (1993) Printing ink manual, 5th edn. Blueprint, New York. 

The solid model is fabricated by exposing a liquid photocurable polymer of 2 mm thickness to UV radiation, and subsequently stacking the cross-sectional solidified layers. 

Cross-linking in LEDs clearly addresses the device development issue. By generating chemical bonds between polymer chains, the former layer can no longer be dissolved by the solvent of the subsequent layer. Devices comprising up to four cross-linked layers have been fabricated. Cross-linking is also going beyond the unique simplification of the device fabrication. Benefits in terms of device performance, device lifetime and thermal stability have also been evidenced. Photocuring is often combined to... 

Miyamoto, K., Waki, M. (1996) Photocured cross-Unked-hyaluronic acid gel and method of preparation thereof. US Patent US6031017, filed Nov. 14, 1996, and issued Eeb. 29, 2000. 

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