Increasing the antioxidant capability via the synergistic effect of coupling diphenylamine with sterically hindered phenol

Solvent-Free Transformation of EVA Into Pressure-Sensitive Adhesives (PSAs) by Mixing Nonylated Diphenylamine: Improved Tack, Adhesion Strength, and Longevity

Pressure-sensitive adhesives (PSAs) bond surfaces with minimal pressure, eliminating the need for heat, water, or solvents. Ethylene vinyl acetate (EVA) is a well-established polymer in hot melt adhesives; however, research on EVA-based PSAs is limited. This study introduces nonylated diphenylamine (NDPA), a liquid derivative of diphenylamine, as a novel tackifier and antioxidant for EVA-based PSAs. By simply mixing NDPA with EVA at elevated temperatures, an EVA-based PSA is successfully formulated without the use of toxic solvents. The molecular structure of NDPA, characterized by alkyl chains and secondary amines, allows it to interact effectively with both the polyethylene (PE) and vinyl acetate moieties in EVA. These interactions significantly enhance the viscoelastic properties and adhesive strength of the formulations. Notably, the addition of NDPA increases lap shear strength from 98.67 kPa for pure EVA to 516.67 kPa for the EVA-NDPA formulation containing 40 wt.% NDPA. Furthermore, a 50 wt.% inclusion of NDPA achieves the highest peel strength of 6.5 N mm⁻¹, surpassing that of commercial PSA tape. Additionally, NDPA contributes to preventing oxidative degradation, significantly enhancing the longevity of adhesive properties and positioning it as a promising additive for improved EVA-based PSA formulations.

Semicarbazide and thiosemicarbazide containing butylated hydroxytoluene moiety: new potential antioxidant additives for synthetic lubricating oil

New multipotent antioxidants (MPAOs), namely semicarbazides and thiosemicarbazides bearing thiolated butylated hydroxytoluene (BHT), were synthesized. The antioxidant activity of the synthesized compounds was evaluated using in vitro DPPH assay. Compounds containing thiosemicarbazides (5a′–h′) were found more active in free radical scavenger than semicarbazides (5a–h). Among the other compounds, compound 5f′ (IC₅₀ of 25.47 ± 0.42 μM) showed the best antioxidant activity against DPPH radicals compared to standard antioxidant butylated hydroxytoluene (BHT). Based on DPPH results, compound 5f′ and its corresponding semicarbazide 5f were blended into trimethylolpropane trioleate (TMPTO) and isothermal differential scanning calorimetry (DSC) was carried out for the investigation of oxidative stability. At 125 °C isothermal DSC, TMPTO with 0.25 wt% of 5f′ showed 1.5 times higher oxidation stability than its corresponding semicarbazide 5f and was 2 times better than BHT. It was anticipated that due to the strong auto-synergistic effect, compound 5f′ showed promising oxidative stability to TMPTO by protecting from pre-mature oxidative degradation.

New multipotent antioxidants (MPAOs), namely semicarbazides and thiosemicarbazides bearing thiolated butylated hydroxytoluene (BHT), were synthesized.