Study the shrinkage process of UV-curable adhesive using digital holographic interferometry

In this paper digital holographic interferometry (DHI) is implemented to study the shrinkage/hardening behavior of UV-curable acrylic adhesives. In the experiment, an aluminum plate as a reflective object was placed on top of the UV adhesive coating, and the temporal variation of the thickness of the UV adhesive coating during the curing process was determined from the vertical displacement of the aluminum plate using DHI. The effect of two different UV-illumination intensities on the curing process and shrinkage behavior were studied on two types of acrylic adhesives with different compositions and viscosity. In the case of first adhesive A, the experimentally calculated values of final shrinkage were 3.23 mu m for the UV illumination intensity of 30 mW/cm2, and 4.39 mu m for UV illumination intensity of 50 mW/cm2. While in case of second adhesive B, the measured final shrinkage values were 0.15 mu m for the UV illumination intensity of 30 mW/cm2, and 1.12 mu m for the UV illumination intensity of 50 mW/cm2. The proposed method for the experimental investigations of shrinkage behaviors/ hardening process of UV-adhesives provides useful information for analyzing the curing behavior of adhesives in their developing stages. Also, the quantitative investigations of shrinkage behavior of adhesives are highly required for the assembly of high-performance optical devices that require sub-mu m positional accuracy of optical components.