One‐pot Synthesis of Long Chain Branch PP (LCBPP) Using Ziegler‐Natta Catalyst and Branching Reagents

Abstract

A new class of long chain branched isotactic polypropylene (LCBPP) polymers with high molecular weights and well‐controlled structures are prepared via a combination of rac‐Me2Si(2‐Me‐4‐Ph‐Ind)ZrCl2/MAO catalyst and a T‐reagent, such as p‐(3‐butenyl)styrene. The T‐reagent can simultaneously serve two functions (comonomer and chain transfer agent) during metallocene‐mediated propylene polymerization in the presence of a small amount of hydrogen. 1H NMR and SEC equipped with triple detectors revealed most of polymer chain containing LCB structure. LCBPPs displayed a systematic increase in zero‐shear viscosity and Arrhenius flow activation energy as branch density increased. LCBPPs with high branch point density displayed thermorheologically complex behavior, and strain hardening was observed in extensional flow.

Rheology and thermal behavior of long branching polypropylene prepared by reactive extrusion

“…There are some reports on the direct synthesis of LCB-PP using metallocene catalysis. [7][8][9][10] But, this method is often used in laboratory. Electron beam irradia-tion 4,[11][12][13] and reactive extrusion process 1,2,5,6,14,15 can be applied easily in industry for branching PP.…”

“…The electron beam irradiation causes scission of PP chains, which is followed by some crosslinking, leading to LCB. Scheve et al 10 achieved the branched PP by irradiating a solid and linear PP with high-energy radiation in a nitrogen environment, and the modified PP exhibited substantial melt strain hardening. Even though most commercial HMS-PP is produced by electron beam irradiation, the method of using reactive extrusion has recently regained interest, as it can be directly applied also by the foam manufacturer on commercial linear PP.…”

“…There several possible routes to branching PP. There are some reports on the direct synthesis of LCB‐PP using metallocene catalysis 7–10. But, this method is often used in laboratory.…”

An Overview of the Potential of UV Modification of Polypropylene

“…PP produced by a metallocene catalyst has a narrower molecular weight distribution . Metallocene catalysis has not only been utilized for controlling the MWD, but also for producing grades of PP with long chain branches in their backbone (long chain branched PP) …”