Mechanism of reactive compatibilisation of a blend of recycled LDPE/HIPS using an EPDM/SB/aromatic diamine co-additive system

First-life outdoor use of low-density polyethylene (LDPE) results in complicated chemical, physical and mechanical changes, decreasing material properties of the reclaimed polymer commingled with small amounts of other polymers. An upgrading system was developed exploiting beneficially chemical changes of the recycled LDPE collected from municipal sources. Analysis of experimental data of melt reprocessing of thermally or photochemically pre-aged LDPE blends with high-impact polystyrene (HIPS) indicated an improvement of impact tensile strength and phase structure after addition of a 1:1 mixture of styrene-butadiene copolymer (SB) with ethylene-propylene-diene monomer (EPDM) (the SB component playing a key role) and by restabilization with N,N′-disubstituted 1,4-phenylenediamine (PD), the latter having a bifunctional character arising from its ability to scavenge both alkyl-peroxy and alkyl radicals. The mechanism of the diamine-mediated compatibilization process is presented.