Regeneration and utilization of waste phenolic formaldehyde resin: A performance investigation

Recycled thermosetting phenolic formaldehyde (RPF) resins were pulverized to micron-sized powders and successfully reused as an effective component by reactive-injecting with neat phenolic formaldehyde (PF) and/or trioxymethylene (TOX) to prepare regenerated phenolic formaldehyde (i.e., PF _x RPF ^w _y and PF _x RPF ^w _y TOX _z ). Tensile strength (σ _f ), impact strength (I _s ), and density (ρ) of PF _x RPF ^w _y and PF _x RPF ^w _y TOX _z specimens were reduced as RPF concentrations or average particle sizes increased. It is worth emphasizing that σ _f , I _s , and ρ of each reaction-injected PF _x RPF ^w _y TOXz series having a fixed RPF concentration and average particle size improved to a maximum value, as TOX concentrations reached a corresponding optimal value. This is the first investigation to report that σ _f and I _s of proper regenerated PF/RPF/TOX specimens using ≦20 wt % RPF waste were ≥ 95% of those of the virgin reaction-injected PF. Possible reasons accounting for these improved mechanical properties were proposed based on results from their Fourier transform infrared analysis (FTIR).