UV resin, also known as photosensitive resin, is an oligomer that can undergo rapid physicochemical changes within a short period of time after light irradiation and then cross-linked and cured.UV resin is a low molecular weight photosensitive resin with reactive groups that can perform UV, such as unsaturated double bonds or epoxy groups.UV resin is the base resin for UV coatings and is compounded with photoinitiators, reactive diluents and various additives to form UV coatings.

Properties:Cross-linked curing oligomer

UV resin is the advantage of UV coating base resin.

(1) Fast curing speed and high production efficiency.

(2) High energy utilization and energy saving.

(3) Less organic volatile compounds (VOC), environmentally friendly.

(4) can be coated with various substrates, such as paper, plastic, leather, metal, glass, ceramics, etc.

UV resin is the largest component in UV coatings, and is the base resin of UV coatings. It generally contains groups that further react or polymerize under light conditions, such as carbon double bonds, epoxy groups, etc. Depending on the type of solvent, UV resins can be divided into solvent-based UV resins and water-based UV resins. Solvent-based resins do not contain hydrophilic groups and can only be dissolved in organic solvents, while water-based resins contain more hydrophilic groups or hydrophilic chain segments and can be emulsified, dispersed or dissolved in water.

Solvent-based UV resins: The commonly used solvent-based UV resins are mainly: UV unsaturated polyester, UV epoxy acrylate, UV polyurethane acrylate, UV polyester acrylate, UV polyether acrylate, UV pure acrylic resin, UV epoxy resin, UV silicone oligomer.

Water-based UV resin:Water-based UV resin is a UV resin that can be dissolved or dispersed in water. The molecule contains a certain number of strong hydrophilic groups, such as carboxyl, hydroxyl, amino, ether, amide groups, etc. and unsaturated groups, such as acryloyl, methacryloyl or allyl. Water-based UV tree is divided into emulsion type, water dispersion type and water soluble, mainly including water-based urethane acrylate and water-based epoxy acrylate three categories.

UV resin characteristics

(1) Low viscosity. Light curing is based on CAD models, resin is laminated layer by layer to form parts. After a layer is done, it is difficult for the liquid resin to automatically cover the surface of the cured solid resin, because the surface tension of the resin is greater than that of the solid resin. The resin liquid surface must be scraped once with an automatic squeegee, and the liquid surface is leveled before the next layer can be processed. This requires the resin to have a low viscosity to ensure good leveling and ease of handling. At present, the viscosity of the resin is generally required to be below 600 CP-s (30℃).

(2) Small curing shrinkage. The distance between molecules of liquid resin is the distance of van der Waals force, which is about 0.3~0.5 nm. After curing, the molecules are cross-linked and the distance between molecules forming the network structure is converted into the covalent bond distance, which is about 0.154 nm. Obviously, the distance between molecules before and after curing is reduced. The intermolecular distance of an addition polymerization reaction will decrease by 0.125-0.325 nm. The chemical change process, in which C=C becomes C-C, increases the bond length slightly, but the contribution to the change in intermolecular action distance is small. So the volume contraction after curing is inevitable. Also, before and after curing, disorder becomes more ordered and volume shrinkage occurs. This is very unfavorable to the shrink molded model, which will generate internal stresses and easily lead to deformation, warping, cracking, etc. of the model part. , and seriously affect the accuracy of the part. Therefore, the development of low shrinkage resins is the main problem facing SLA resins at present.

(3) Fast curing speed. Generally each layer thickness of 0.1 to 0.2 mm to be cured layer by layer during molding, curing a finished part requires hundreds to thousands of layers. Therefore, the curing rate is very important if the solid is to be manufactured in a short time. The exposure time of the laser beam to a spot is only in the range of microseconds to milliseconds, which is almost equivalent to the lifetime of the excited state of the photoinitiator used. Low curing rate not only affects the curing effect, but also directly affects the efficiency of the molding machine, making it difficult to apply to commercial production.

(4) Low expansion. During the molding process, the liquid resin always covers the cured part of the workpiece and can penetrate into the cured part, causing the cured resin to swell, resulting in an increase in part size. Only the low swelling of the resin can ensure the accuracy of the model.

(5) High Sensitivity. Because SLA uses monochromatic light, it is required that the wavelengths of the photosensitive resin and the laser must match, i.e., the wavelength of the laser should be as close as possible to the maximum absorption wavelength of the photosensitive resin. At the same time, the absorption wavelength range of the photosensitive resin should be narrow, which can ensure that curing occurs only at the point of laser irradiation, thus improving the manufacturing accuracy of the part.

(6) High degree of curing. It can reduce the shrinkage of the post-curing molding model, thus reducing post-curing deformation.

(7) High wet strength. High wet strength ensures that the post-curing process does not produce deformation, swelling and interlayer peeling.

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