Influence of the mechanism and parameters of hardening of modified novolac phenol-formaldehyde resins on the physicomechanical properties of the composite

We study the influence of concentrations of the components of reactive compositions and the conditions of production and hardening of phenol-formaldehyde resins with the help of epoxy resins in the presence of polyvinylpyrrolidone on the physicomechanical, thermal, adhesion, insulation, and anticorrosion properties of the composites. The positive effect of modifications with polyvinylpyrrolidone and epoxy resin manifests itself within the following ranges of concentrations: 0.5–1 wt.% of polyvinylpyrrolidone and 25–30 wt.% of ED-20 in the presence of 1 wt.% of N, N-dimethylaniline. Thus, the adhesion strength of a glue based on the developed composition becomes four times higher and constitutes 5–6 MPa; the impact strength, static strength in bending, surface hardness, and the specific bulk electric resistance of the specimens hardened at 150–160°C for 25–30 min become 1.5–2.5 times higher and are equal to 5–6J/m², 15–17 MPa, 350–420 MPa, and (5.5–6.5)⋅10¹⁰ Ω⋅m, respectively. The behavior of these characteristics strongly depends on the conditions of hardening. We optimized the composition of modified phenol-formaldehyde resins, which made it possible to produce materials with predicted properties.