The effect of initiator, polyfunctional monomer and polybutene-1 resin on the long chain branching of random polypropylene copolymer via reactive extruder

Polypropylene random copolymer (PPR) and polybutene-1(PB-1) are blended and long-chain branched (LCB) in the reactive extruder. The optimum amount of PB-1 resin, peroxide (DCP) and trimethylolpropane triacrylate (TMPTMA) for long-chain branching of PPR and probe topology formed by the branches were investigated. Fourier transformed infrared spectroscopy (FTIR) used to measure the branching degree and efficiency as well as obtaining TMPTMA grafts on PPR. Oscillatory shear rheological properties including complex viscosity, storage modulus, loss tangent, and uniaxial elongational rheometry were studied to differentiate the LCB-PPR from unmodified PPR with almost similar molecular weight samples. The LCB structure modified samples with TMPTMA and DCP, prominent higher zero-shear viscosity, longer relaxation time and pronounced strain-hardening behavior. It was found that different amount of DCP and TMPTMA can affect strain-hardening behavior and topology of branches and subsequently the foaming ability. PB-1 resin found to have a positive effect because of more sensibility to beta-scission degradation and mobilizing effects. The optimization of PB-1 for the highest zero-shear viscosity, shear, and uniaxial rheological behavior is achieved at 10 wt% PB-1, while 0.08% of DCP and 3% of TMPTMA are optimum amounts of additives needed for long-chain branching process. The optimum blend could be a great alternative for foaming applications.

Automated summary

In this study, the optimal ratio of PB-1 resin, peroxide, and TMPTMA for long-chain branching of PPR was investigated, as well as the topology formed by the branches. Different amounts of DCP and TMPTMA were found to affect strain-hardening behavior and foaming ability. The addition of PB-1 resin showed positive effects on the properties of the blended material.