Basic characteristics of UV resin

(1) Small swelling. In the process of model forming, the liquid resin has been covered on some cured workpieces, which can penetrate into the cured parts and swell the cured resin, resulting in the increase of part size. Only when the resin swelling is small can the accuracy of the model be guaranteed.

(2) Small curing shrinkage. The distance between liquid resin molecules is the van der Waals force action distance, which is about 0.3 ~ 0.5 nm. After curing, the molecules are crosslinked and form a network structure. The distance between molecules is transformed into covalent bond distance, which is about 0.154 nm. Obviously, the distance between molecules before and after curing decreases. The distance of one addition polymerization reaction between molecules should be reduced by 0.125 ~ 0.325 nm. The contribution of C = to the intermolecular transition is small, although the chemical distance of C = changes slightly. Therefore, volume shrinkage is inevitable after curing. At the same time, before and after curing, from disorder to more order, there will also be volume shrinkage. Shrinkage is very unfavorable to the forming model, which will produce internal stress, which is easy to cause deformation, warpage and cracking of model parts, and seriously affect the accuracy of parts. Therefore, developing low shrinkage resin is the main problem faced by SLA resin at present.

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

The composition analysis of UV resin shows that the main application fields are: UV coating, UV ink, UV glue, etc., among which UV coating is the most widely used, including the following types of UV water-based coating, UV powder coating, UV leather coating, UV optical fiber coating, UV metal coating, UV paper polishing coating, UV plastic coating, UV wood coating, etc.