Triblock copolymers, comprising cyclic anhydride moieties, acting as reactive re-processing enhancers for polyamides

Carbonate- and ether-based oligodiols have been converted into macro-RAFT agents via ATRAF reactions. They have been utilized in RAFT polymerization of styrene and maleic anhydride (MA) to obtain triblock copolymers (TBCs) with poly(styrene-co-maleic anhydride) side blocks. These copolymers have been used as chain extenders and tensile strength modifiers for polyamides (PAs) during reactive extrusion, which mimics mechanical recycling. TBCs of different chain lengths, number of MA moieties per chain, and stiff-to-elastic block ratio were utilized. The additives offset PA degradation during polymer processing. After 25 min of mixing (∼5 recycling acts), the melt viscosity of PAs have increased at least by over five times (from 55 to around 300 Pa s for PA12 and from 5 to 25 Pa s for PA6). The tensile strength of the blends was unchanged for PA12 and increased for PA6 (up to 17 %). The materials were stiffened by the presence of rigid side blocks (up to 40 % rise in Young's modulus). The type and weight fraction of oligodiol and the amount of TBC used affected the results. The presence of TBCs did not influence the morphology of the materials.