Improving Melt Strength of Polypropylene by Minimal Branching and Blending

GUAPACHA, JORGE; JONATHAN BARBOSA; ENRIQUE M. VALLÉS; LIDIA MARÍA QUINZANI; MARCELO DANIEL FAILLA

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 2020 vol. 137 p. 1 - 11

0021-8995

Publicación on-line: Noviembre-2019Publicaciónimpresa: 137(26), Julio, 11 pág., 48845 (2020)Resumen: Branched polypropylenes(PPb) with markedly improved melt strength were produced without significantlyaffecting the processability of the original PP. A two-step process offunctionalization with MA and crosslinking with m-XDA was used, both by batchmixing and extrusion. Branching degrees of ~0.06 LCB/1000 monomer units or smaller were obtained. All PPbs display clearand significant strain hardening, being the PPb obtained by extrusion the onethat shows the largest melt strength. This polymer has a zero-shear-rateviscosity slightly smaller than that of PP while its strain hardening index isabout 10times higher. Moreover, the nonlinear behavior of PP at elongation begins at atime similar to its terminal relaxation time or larger, while the ratio ofthese times reduces significantly with branching. PP/PPb blends wereprepared to extend the range of obtainable melt strength in PP. They displayrheological behavior between those of the mixed polymers with slight positivedeviation.