Structure-mechanical property relationships in acrylate networks

The objective of this work is to investigate the effect of the molecular mobility and resin formulation of UV-curable acrylate systems on conversion and ultimate mechanical properties. Thin single-layer films are produced from a series of nine mixtures of bisphenol A ethoxylate diacrylate, having different molecular weights (BisDA(n = 2), BisDA(n = 4), and a 50/50 mixture), with different amounts of tetraethylene glycol diacrylate (TEGDA) (0, 10, and 30 wt %). Fourier transform infrared analysis, tensile, and dynamic mechanical tests are carried out on UV post-cured resins, and the results are correlated with the amount of TEGDA. A higher content of TEGDA gives rise to an increase in conversion and glass-transition temperature. Tests on pure BisDA(n = 2) and mixtures of BisDA(n = 2) and BisDA(n = 4) (BisDA(n = 2 + 4)) show that with increasing TEGDA content, the crosslink density increases. An increase in molecular weight of the acrylate monomer changes the final mechanical properties of UV-cured products. A material having a rubber behavior is the result of this change. Next to UV post-curing, the effect of thermal post-curing is studied. The results show that thermal treatments affect the mechanical properties mainly if the polymer has a low crosslink density. Formulations highly loaded with TEGDA lead to polymers with high crosslink density, low network mobility, and consequently low mechanical properties if thermally treated. Correlations between, on the one hand, resin formulation and process conditions and, on the other hand, the final mechanical properties of UV-cured systems are established allowing to optimize the structure-mechanical properties relationship in acrylate networks. (c) 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48498.