Unlike linear polypropylene (PP),
PP with long-chain
branches (LCB-PP)
has been known to have high value in polymer processing that requires
high melt strength characteristics, such as thermoforming, foaming,
and blow molding. In this study, LCB-PP is prepared utilizing the
C–H insertion capability of an azidoformate (AF) group. A small
molecule with two AF groups at both ends, tri(ethylene glycol) di(azidoformate)
(GDAF), is synthesized, where the AF groups are thermally activated
to afford nitrene intermediates to interconnect PP chains. Propylene/1-butene
copolymer is employed as a dispersant of GDAF, which is first melt-blended
with each other at 100 °C to afford a master batch. Then, the
mixture is reactive melt mixed with PP at 165 °C to thermally
activate the AF groups of GDAF to afford LCB-PP. The amount of branches
is controllable by adjusting the GDAF loadings. Due to the branched
chain architectures, investigation of rheological characteristics
reveals more elastic and strain hardening melt behaviors of the resulting
LCB-PPs with higher GDAF loadings, which demonstrates a simple and
scalable melt mixing procedure to afford value-added polyolefins.