Effect of lamp cycling on conversion and stress development in ultraviolet‐cured acrylate coatings

Abstract

ABSTRACT:In radiation-cured acrylate coatings, a high conversion of monomer is generally desired to improve hardness, prevent further slow reaction upon aging, and avoid surface toxicity; however, shrinkage and, consequently, stress in coatings tend to increase with conversion. One route to achieve high conversion while maintaining low coating stress is to promote stress relaxation. In this study, acrylate coatings were cured with a UV lamp that was cycled on and off, varying the period from 2 to 60 min while keeping the total dose constant. All samples reached nearly the same conversion, between 46 and 48% conversion of functional groups, as measured by FTIR spectroscopy. The coating stress (measured with cantilever deflection) at the end of the exposure cycles, however, was lowered from 8 MPa (tension) to less than 3 MPa (tension) as the period was decreased from 60 to 2 min. The cycling had no significant effect on either the coating hardness or the modulus, as measured by a Hysitron triboscope. Stress relaxation and/or slower reaction during the dark periods are the likely causes for the lower coating stress. It was advantageous to introduce dark periods early in the processing.

Effect of oligomer length on the buckling of long and high aspect ratio microwalls UV embossed from oligomer/monomer mixtures

“…Fig. 8 demonstrates that the large majority of the overall stress is developed in the final stage of polymerization when the modulus is high, which is consistent with the general observations in the polymerization of other kinds of (meth)acrylate [13,44,45].…”

“…Stress increase is insignificant until 40%, 50%, 70% and 80% conversion for E0, E3, E10 and E30, respectively. Wen et al reported in neat oligoethylene glycol multi-(meth)acrylate systems, significant stress develops only at high conversions, which are much higher than gelation conversion and R max p conversion [44]. Their results show that the stress developed in the gelled state is small because of low modulus and fast relaxation.…”

Nanoimprint Lithography with UV‐Curable Hyperbranched Polymer Nanocomposites

“…[40,41] In the standard photoresists SU-8 stresses are around 20 MPa [42] before and up to 75 MPa [43] after postexposure bake. A further advantage for the production of stable nano-patterns is the reduced CTE (Table 1) for better thermal stability.…”

Dissolution of Al2O3-polystyrene latex composites: a fluorescence study

“…Processing and microstructure development of ceramic and polymer coating prepared by depositing a solution or dispersion have been of interest in last few years [2,3]. Nano-sized antimony-doped tin oxide particles and poly(n-butyl methacrylate) lattices were combined to construct transparent conductive coating and a reduction in the percolation threshold was observed in the latex-based matrix [4].…”