High Melt Strength Polylactic Acid: Synergistic Effect of Peroxides and Branching Coagents on Long-Chain Branching

In this study, we employed two distinct branching coagents to optimize the topology structure of long-chain branched polylactide (LCB-PLA) via melt grafting with 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (Trigonox301) and PLA. Our findings reveal that an impressive 22.8% degree of branching degree in PLA was attainable with the addition of merely 2 wt % allyl glycidyl ether (AGE) and 0.75% Trigonox301. Three mathematical models were applied to quantitatively assess the degree of branching based on molecular weight distribution, zero-shear viscosity η₀, and phase angle. Notably, the presence of gel complicated the precise determination of the branching degree when using LCB_G derived from molecular weight distribution fitting. Comparatively, the η₀ and LCB_C, derived from complex viscosity fitting for LCB-PLA samples enriched with 2 wt % AGE, saw a marked escalation from 2140 Pa s and 0 mol % to 13286 Pa s and 22.8 mol %, respectively.

Furthermore, the preferential end-group reaction between the epoxy group of AGE and the carboxyl group of the PLA molecule chain indicated that AGE was more efficacious in enhancing the branching degree than trimethylolpropane triacrylate (TMPTA).