UV -curable materials

Hot melt aerylie polymers for UV cure are generally of lower moleeular weight than their solution counterparts in order to maintain an aceeptable application viscosity. Consequently more crosslinks are needed to produce a complete network and thus peel and tack suffer to some degree. Nonetheless, several UV curable materials have been commercialized for PSA tapes and labels. 

Ultraviolet-curable pressure sensitive adhesives (PSA) are based on two types of UV-curable materials ... 

Stereolithography The trend is to develop UV-curable materials that mimic engineering plastics, such as polycarbonate or ABS (see below). 

The type of crosslinking achieved with electron beam and uv radiation is very similar, but the way curing initiates is different. Electron beams have the higher energy, and the electron itself has sufficient energy to initiate polymerization. In uv curable materials, the polymerization reaction is not directly initiated by uv light, and a photoinitiator is required to interact with the uv radiation and produce the initiating species. 

In this technique, layers of liquid UV curable material are alternately spread and selectively cured by a laser which scans the surface according to specific slice size and shape. The laser causes the liquid layer to polymerize wherever the laser beam strikes the surface, resulting in the creation of a solid plastic layer just beneath the surface. 

Digital Material is a new and special type of Composite Material, produced during the printing process by the selective deposition of different UV curable materials, from different inkjet nozzles, and according to a predefined Composite Material phase structure. This phase structure is design by Computer-Aided Design (CAD) software. 

Alternatively, if one of the component UV curable materials is soft and elastic and the other is hard and brittle. Digital Materials with intermediate or varying mechanical properties can also be produced. In addition, because Digital Materials are not simply a homogeneous combination of two different materials, but Composite Materials, where each component material maintains its own properties within a microscopic phase range, their properties are not just the average of the properties of the component materials, but much more. Because Digital Materials are defined by means of precise software... 

Zinc sulfide has the next highest refractive index to titanium dioxide and zirconium oxide making it a very efficient pigment. The spectrum of absorption of zinc sulfide resembles more closely anatase than rutile. Because it does not absorb certain UV wavelength, zinc sulfide is useful as a pigment for UV curable materials. 

The kinetics of reaction is discussed in Section 6.10 and polymerization reactions in Section 6.7. Grafting is discussed in Section 6.8, crosslink density in Section 6.9, and bound rubber in Chapter 7. Here, UV-curable materials, epoxy resins, polyurethanes, rubbers, polyesters, and phenolic resins are discussed. 

Another processing option made possible with UV curable materials would be the in-situ development of a barrier to retard flow of coatings and encapsulants during application.(Lutz, M. 

Figure 5. Photobarrier processing example for in situ generation of flow barriers during processing of UV curable materials.

Adhesion to metal is sometimes difficult to achieve. However, due to the development of adhesion promoters industrial applications on metal exist. Electronics applications are important photoresists (both wet and dry film), solder masks, potting compounds, and conformal coatings are products based on UV-curable materials. 

Optical fibers have been coated with a protective layer of UV-curable materials for a long time. 

Intaglio inks (special inks used to avoid counterfeiting of items such as bank notes) are also employed and ink-jet printing with UV-curable materials is starting. 

A differential photocalorimeter can be interfaced with a thermal analysis system to measure the heat absorbed or released by a sample as the sample and an inert reference are simultaneously exposed to UV radiation of known wavelength and intensity during programmed heating or in an isothermal manner. Important applications include UV curing studies of compositions, formulations, and mechanisms of UV-curable materials and coatings. 

Using this TGA/WVT capsule technique, vapor transport data have been collected not only for glassy PC and rubbery silicone films as reviewed here but also for crystalline films of poly(ethylene terephthalate) (PET) and a microporous Gortex membrane (Holcomb and Bair 2005). With a small modification this WVT capsule can be employed to confine volatile reactive liquids such as the UV-curable materials studied in DPC work at elevated temperatures (see Section 2.11, on differential photocalorimetry). 

Zovi, O., Lecamp, L., Loutelier-Bourhis, C., Lange, C.M., Bunel, C., 2011. A solventless synthesis process of new UV-curable materials based on linseed oil. Green Chem. 13, 1014-1022. 

Initial development of UV-curable materials for imprint lithography predates NIL and was inspired in the 1980s by the need to make reliable replicas in a short amount of time, and at a low cost, for LaserVision videodiscs. " Researchers at the Philips Research Laboratories in the Netherlands coined the production process of videodisc replication as photopolymerization process or 2P process." The 2P process requires the use of photosensitive materials that become extremely hard, with low shrinkage, once exposed to UV radiation (typically 300-400nm). The 2P process is based on free radical chemistry, and UV-curable materials consist of liquid monomers, usually acrylates or acrylate oligomers, to which a suitable photoinitiator is added. A little over a decade later, Haisma et extended this work to mold-assisted nanolithography and is the first reported work of UV-NIL with 100 nm features. 

To alleviate several issues with free radical-initiated UV-curable materials, such as oxygen sensitivity, curing rate, and shrinkage upon curing, cationic-initiated UV-curable materials have been explored. For example, Kim et have... 

UV-curable materials for controlled bmsh growth via living free radical polymerization techniques of atom transfer radical polymerization (ATRP) and NMP to tune the size of nanoscale features down to 20 nm. Bmshes grown from the surfaces... 

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