4 4 diaminodiphenylmethane ddm

The diglycidyl ether of bisphenol-A (DGEBA; YD-128; Kukdo Chemical Co., Seoul, Republic of Korea) was used as the epoxy resin. The epoxide equivalent weight of DGEBA was 185–190 g/equiv., and its density was 1.2 g∙cm⁻³ at 25 °C. Furthermore, 4,4′-diaminodiphenylmethane (DDM, 45–49 g/equiv.; Sigma-Aldrich Co., St. Louis, MO, USA) was used as the curing agent [29 (link)]. The chemical structures of DGEBA and DDM is shown in Figure 1. The BNNS (98% purity; Sigma-Aldrich Co., St. Louis, MO, USA) had a lateral size of 150 nm and thickness of 4 nm.

The epoxy resin employed in this study was a difunctional diglycidyl ether of bisphenol A (DGEBA) with an equivalent weight of 175–180 g/equiv. and a hydroxyl/epoxy ratio of 0.03, supplied by Sigma-Aldrich (St. Louis, MI, USA). The hardener was a solid tetrafunctional aromatic amine, 4,4′-diaminodiphenylmethane (DDM), from Sigma-Aldrich, with a molecular weight of 198 g/mol and an amine equivalent weight of 49.5 g/mol.
Commercial powder graphite containing 99 wt % minimum of carbon, 0.8 wt % maximum of ash, and 0.05 wt % maximum of sulfur from Acros Organic was selected for the preparation of GO and rGO. For the oxidation of graphite, sodium nitrate was purchased from Acros Organic, whereas sulfuric acid (95–97%), potassium permanganate (extra pure) and hydrogen peroxide (30 wt %) were purchased from Scharlau. For the GO reduction, monohydrated hydrazine (64–65%) from Sigma Aldrich was used. Pure water by ELIX Advantages (type II) was employed in the current work. All reagents have been used without further purification.

The biobased epoxy used in this research work was diglycidyl ether of vanillin (DGEVA) supplied by Specific Polymers, Castries, France. The curing agent was 4,4′-diaminodiphenylmethane (DDM), purchased from Sigma-Aldrich, Darmstadt, Germany. The block copolymer used was poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-PPO-PEO) triblock copolymer (Pluronic F-127) supplied by Sigma Aldrich, Darmstadt, Germany. Chemical structures of employed materials are shown in Table 2. An amine:epoxy ratio of 1:1 was used for the DGEVA/DDM system, while PEO-PPO-PEO block copolymer content was varied from 10 to 50 wt% to design different BCP-DGEVA/DDM systems.
Sample preparation was carried out in the following way. First, DGEVA resin and PEO–PPO–PEO triblock copolymer were blended at 80 °C under mechanic stirring. Then, a corresponding amount of DDM was added with continuous stirring, in an oil bath at 80 °C, until a homogeneous mixture was achieved. Finally, the mixture was poured to the mold, and samples were degassed in a vacuum oven and cured at 120 °C for 6 h and post-cured under vacuum at 190 °C for 2 h. In both cases, a mechanical vacuum pump device was employed.