TABLE OF CONTENTS Since the coating materials have to meet numerous requirements regarding performance, processing and storage consistency, they have to be well characterized in order to enable constant product quality. A good compilation of the various characterization methods available for coating raw materials is given in Handbook on Basics of Coating Technology.74 In this chapter some of the most relevant characterization methods for UV-curable raw materials are described briefly.
The most common characteristic values for the raw materials used in UV-curable systems are given in Table 4.7.
| Oligomeric resins | Diluents | Photoinitiators |
|---|---|---|
| Functionality | Viscosity | Absorbance spectrum |
| Viscosity | Density | Appearance |
| Density | Colour | Melting point |
| Molar mass | Molar mass | Solubility |
| Colour | Acid value | |
| Hydroxyl value | ||
| Acid value |
The viscosity of a coating formulation governs the film formation and surface characteristics, like the appearance of a film.
The viscosity of coating formulations or raw materials is measured by the kinematic viscosity, when flow is driven by gravity [measured in m 2 /s or stokes (St): 1 m 2/s = 10,000 St]. A simple equipment to determine the kinematic viscosity often used in the coatings industry is a 100 cm 3 beaker (DIN 53211 and ASTM D-4212) with defined nozzle geometry (e.g., 4 mm for DIN beaker 4). The flow time is...
