Development of Rheometer for Measuring the Viscoelasticity of Photosensitive Polymers and UV Inks during Curing.

研制了一种用于测量光敏聚合物和UV油墨动态粘弹性的新型流变仪。实际上，在基材上涂覆或印刷的层的厚度通常为几微米，并且在暴露于紫外线照射下的几秒钟内完成固化。因此，流变仪的设计可以连续跟踪这种液体薄膜流变特性的快速变化。考察了光引发剂浓度、颜料浓度、膜厚和波长对UV油墨及其载体固化性能的影响。由于引发聚合的自由基是由引发剂的光分解形成的，因此固化膜的能力取决于膜中给定深度处的光强度。固化速率随厚度的增加而降低。吸收系数可由固化速率对厚度的依赖关系确定。测定了热固性涂层在烘烤过程中的固化性能。利用加热粘度随时间变化曲线中的最小粘度，可以讨论其流平和下垂趋势。

A new type of rheometer for measuring the dynamic viscoelasticity of photosensitive polymers and UV inks was developed. Practically the thickness of layer which is coated or printed on a substrate is generally of the order of a few microns and the curing is completed within a few seconds on exposure to UV irradiation. Therefore, the rheometer is so designed as to continuously follow the rapid changes in rheological properties of such thin liquid films.The effects of photoinitiator concentration, pigment concentration, film thickness and wavelength on curing behavior were examined for UV inks and its vehicle. Since free radicals which initiate polymerization are formed by photodecomposition of initiator, the ability to cure a film depends on the light intensity at a given depth in the film. The cure rate decreases with increasing thickness. The absorption coefficient can be determined from the thickness dependence of cure rate.The curing behavior of thermosetting coatings was also measured during baking process. The levelling and sagging tendency can be discussed using the minimum viscosity in time-dependent curve of viscosity on heating.