Effects of oxidized/treated non‐metallic fillers obtained from waste printed circuit boards on mechanical properties and shrinkage of unsaturated polyester‐based composites

The investigation of the influence of acid/base treatment and addition level of non‐metallic fractions (NMFs), obtained by processing of printed circuit boards, on the mechanical properties and shrinkage of unsaturated polyester resin (UPR)‐based composites was main topic presented in this paper. NMF particles were treated using four different oxidative/etching agents: H₂SO₄/KMnO₄ (NMF1), H₂SO₄/HNO₃ (NMF2), HNO₃ (NMF3), and NaOH (NMF4). Treated NMF(1–4) particles were characterized using fourier transform infrared, Boehm titration, optical microscopy and SEM analysis. Tensile strength and micro Vickers hardness of UPR/NMF(1–4) composites were the most improved with addition of 0.5wt% of filler, for 5.9–24.7%, in comparison to composite filled with non‐treated NMF particles. Cross‐linking density (ν), storage, and loss modulus (G' and G''), damping factor (tanδ) and glass transition temperature (T_g) of the composites were determined from the dynamic–mechanical analysis (DMA) testing. Shrinkage measurements, performed using Aramis 6.2.0, showed significant improvement in shrinkage reducing, for 17.8–30.6%, by introduction the oxidized NMF particles. Qualitative/quantitative evaluation of NMF(1–4) surface functionalities helped in understanding their influences on mechanical, DMA and shrinkage properties change of studied composites. POLYM. COMPOS., 40:1170–1186, 2019. © 2018 Society of Plastics Engineers