Two types of alumina particles, commercial (c-Al₂O₃) and iron doped (Fe-Al₂O₃), were functionalized with 3-(aminopropyl)trimethoxysilane (one-step) and two-step consecutive process, i.e. firstly using 3-(aminopropyl)trimethoxysilane followed by methyl ester of linseed oil (biodiesel) to produce Al₂O₃ATPMS-BD reinforcement, respectively. The effect of modifier type and variable amount of alumina particles on the dynamical and mechanical properties of unsaturated polyester resin–based composites was studied. The highest improvement of the tensile strength and micro Vickers hardness, 78.1 and 163%, respectively, was obtained at 1.0 wt% of Fe-Al₂O₃APTMS-BD addition. The obtained multifunctional composites can be potentially applied in construction and mining industries.

Two types of polymer waste materials, poly(ethylene terephthalate) (PET) and polycarbonate based Colombian Resin (CR-39), were used for the designing of fully recycled composite materials. Waste PET was employed for the synthesis of thermoset unsaturated polyester resin (UPR), while CR-39 was used as reinforcement in the UPR matrix. Prior to mixing, CR-39 particles were subjected to oxidation and chemical activation using acids/base and ethanol amine, respectively. The effect of the modifier type and variable loading of the activated CR-39 particles on mechanical and dynamic-mechanical properties of the corresponding composites was investigated. The greatest improvement in the tensile and flexural strength of UPR resin was achieved with the composite containing 0.5 wt% of amine activated filler particles, 96.0% and 62.2%, respectively. The Arrhenius equation was used to calculate the activation energy for glass transition from dynamic mechanical properties measured at various frequencies. The activation energy of the main transition for UPR resin and composites were calculated to be 173 and 350 kJ·mol⁻¹ indicating that reinforcement results in an increase in the energy barrier to macromolecules viscoelastic relaxation. In addition, erosion resistance was studied during exposure of samples to cavitation tests. According to the obtained results, these materials can be applied in construction and mining industry.