Photopolymers undergo a process called curing, where oligomers are cross-linked upon exposure to light, forming what is known as a network polymer. However, the development of dye-based photoinitiator systems have allowed for the use of visible light, having the potential advantages of being simpler and safer to handle. In some instances, an enamel can cure in a fraction of a second when exposed to light, as opposed to thermally cured enamels which can require half an hour or longer. Photoinitiators are compounds that upon radiation of light decompose into reactive species that activate polymerization of specific functional groups on the oligomers. Common functional groups that can be hydrolyzed by a photo-generated acid catalyst include polycarbonates and polyesters. Photopolymerization is known to be limited in depth by light absorption. Photopolymerization processes make use of liquid, radiation curable resins, or photopolymers as their primary materials.  An example of a mixture that undergoes cross-linking when exposed to light is shown below. The most common photoinitiated polymerization-imaging systems use photoactivated free radical initiators and multifunctional acrylates and methacrylates as the monomers. So how do you know which material is right for your... Simulate. For example, ferrocinium salts have received much attention for commercial applications. In this case the acid group of the polyimide precursor poly(amic acid) is functionalized with methacrylate groups and coated in the presence of a photoactivated free radical initiator. A figure that gives the basics as to how photopolymers are made and what properties change upon illumination, etc. The field of 3D printing is continuing its rapid development in both academic and industrial research environments. These changes either polymerize the liquid oligomers into insoluble cross-linked network polymers or decompose the already solid polymers into liquid products. The use of specialized water-soluble PIs enables 2PP of photopolymers with up to 80% initial water content (Torgersen et al., 2012). A complete summary of all 39 production-ready photopolymer 3D printer OEM’s, including 3D Systems, Atum3D, Azul3D, BMF, Carbon, Coobx, Envisiontec, FormLabs, Fortify, Genera, Nexa3D, Origin, Prodways, Raplas, Rapidshape, RPS, Sisma, Stratasys, and many others. Therefore, it can be relevant to build thick ph When the laser beam strikes the photopolymer it quickly solidifies, i.e., polymerizes into 2D structure due to curing reaction as shown in Fig.  Some monomers, such as styrene, are toxic or carcinogenic. In order to satisfy this, liquid neat oligomer can be doped with either anionic or cationic photoinitiators that will initiate polymerization only when radiated with light. The word polymer means “many parts” and is defined as any material, synthetic or organic, consisting of small simple molecules chained together to form a larger molecule. The support material, which is also a photopolymer, is removed by washing it away in a secondary operation.  The active monomer that is formed is then propagated to create growing polymeric chain radicals. Chemical structure of stereolithography-based photopolymer acrylic resins. Procedural principle of digital light processing (DLP): The layer-by-layer curing process with photopolymers is comparable to the stereolithography approach. In most cases, a hydrogen atom is abstracted from the oligomer by the pyridinium radical. Most negative-working microresists are based on the formation of cross-linked networks as a result of the photodecomposition of azides to highly reactive nitrenes. Figure 16.8. The above equation shows that if the rate of initiation doubles, the rate of polymerization is increased by the factor 2: where φ—quantum field for initiation, Ia—absorbed light intensity, Io—incident light intensity, ∈—extinction coefficient, [ln]—photoinitiator concentration, b—layer thickness. Other less common onium salts include ammonium and phosphonium salts.. , Most commonly, photopolymerized systems are typically cured through UV radiation, since ultraviolet light is more energetic. Resin cements are utilized in luting cast ceramic, full porcelain, and veneer restorations that are thin or translucent, which permits visible light penetration in order to polymerize the cement. The low viscosity of the material solution enables its extrusion through a fine nozzle with an inner diameter as small as 10 µm. There are other polymers which can change their properties (or cured) under radia-tion condition such as heat and microwave. The viscosity can be further adjusted by the addition of nanofillers in the case of nanocomposite-based inks. The image is cut in slices; each slice is then reconstructed through radiation curing of the liquid polymer, converting the image into a solid object. As a whole layer is cured at a time, the DLP technology is known for its relatively high printing speed. Photopolymers are organic materials that transform the light intensity into a refractive index modulation through a photopolymerization process. The development of photopolymers generally makes use of one of the changes in properties that occurs on exposure, most typically by washing away the more soluble regions, or more recently by removing one component by vacuum processes, such as etching with reactive ions. Medical device applications molecules from sewer water have also been explored for uses in drug delivery, engineering... 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