Tuning melt viscoelastic properties of LDPE via reactive extrusion: a dual-agent strategy using TMPTMA and Polyhexene-1

Abstract Long-chain branching (LCB) is achieved in low-density polyethylene (LDPE) via reactive extrusion using a dual-agent strategy. Trimethylolpropane trimethacrylate (TMPTMA) and dicumyl peroxide (DCP) function as a multifunctional grafting agent and free-radical initiator, respectively, and polyhexene-1 is used as a co-component to promote chain scission and enhance branching while suppressing excessive crosslinking. The incorporation of TMPTMA (2 wt%) into the LDPE backbone, verified using Fourier-transform infrared spectroscopy, results in a maximum grafting efficiency of 36.7 %. Rheological characterization reveals that the incorporation of TMPTMA significantly enhances the strain-hardening behavior, zero-shear viscosity, and shear thinning properties, indicative of LCB. Morphological analysis shows that reducing the phase domain size and improving the dispersion of the minor phase in the LDPE matrix increases interfacial compatibility. Notably, loading an excess of TMPTMA (>2 wt%) instigates homopolymerization and reduces the branching efficiency. These results demonstrate that the controlled architectural modification of polyethylene using reactive extrusion enables tailored viscoelastic behavior.