Investigation of accelerated aging of lignin-containing polymer materials

This paper presents the results of an accelerated aging test of biocomposites containing kraft lignin, where the resistance of the materials against humidity and light exposure was investigated. Low molecular weight lignin, modified with methacrylic anhydride (LWL-Met), was copolymerized with two commercial monomers: styrene (St) and methyl methacrylate (MMA). The biocomposites were obtained by a bulk polymerization method using α,α'-azoiso-bis-butyronitrile (AIBN) as a free radical polymerization initiator. The Shore D hardness of the obtained materials was determined before and after aging test. The changes in the chemical structures of polymers, as the result of aging were analyzed by using the attenuated total reflection Fourier transform infrared (ATR/FT-IR) spectroscopy method. The thermal behavior and stability of the obtained materials were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The surface topography was determined using the optical topography method to evaluate the changes on the surface of synthesized materials resulted from accelerated aging. Application of modified lignin as a biocomponent in the polymerization process and its influence on the properties of the obtained materials before and after the accelerated aging test are discussed.