Hydrophilicity Enhancement of UV Cured Acrylic Materials
Sivapackia Ganapathiappan, Boyi Fu and Ankit Vora, Applied Materials, Inc.
Abstract: Products obtained from UV cured acrylic materials are in general strongly hydrophobic in nature. For UV curing, photoinitiators (PI) are required to effect the generation of radicals for the polymerization of acrylic monomers. Hydrophobicity of the cured material mainly arises from the usage of hydrophobic PI in the formulation resulted in its fragments present on the surface after the curing irrespective of the hydrophobic nature of the acrylic mixture. It is a good choice for applications requiring increased hydrophobicity due to the additional benefit arises from the PI influence. On the other hand, some applications (such as synthetic membranes or coatings in some semi-conductor field) may require enhanced hydrophilicity so that the cured surface becomes compatible with hydrophilic components. We have investigated the UV curing of several formulations and found that cured films are always strongly hydrophobic in nature consistently. Hydrophilicity is measured using goniometer by the water contact angle (CA) measurement. In general, if the water CA is <30o, it is considered as hydrophilic in nature. We tried to increase the hydrophilicity by adding poly(ethylene glycol) acrylates (water loving polar material) and found that they do not reduce CA much. We investigated with several other polar additives and found that none of them has a significant effect on reducing the CA. Only by the addition of some specific components significantly enhance the hydrophilicity and bring the CA to <30o. In this presentation such additives and curing method will be discussed.