Combined effects between activating group Z and leaving group R in dithiocarbamates for controlling degradation and branching reactions of polypropylene

- The effect of dithiocarbamates on the melt reaction of modified PP is proposed.
- The topological structure of the LCBPP depends on the chemical structures of dithiocarbamates.
- The proposed mechanism explains the resultant star-like and comb-like topology of the LCBPP.

Four dithiocarbamates with different chemical structures (S-Propyl N,N-dipropyldithiocarbamate, S-allyl N,N-dipropyldithiocarbamate, S-Propyl N-pyrrolocarbodithioate and S-allyl N-pyrrolocarbodithioate) were used to adjust the melt radical reaction of polypropylene (PP). The combined effects between activating group Z (N,N-dipropyl and N-pyrrolo) and leaving group R(allyl and propyl) in the dithiocarbamates on melt reaction of PP were studied in the presence of peroxide and trimethylolpropane triacrylate monomer. The results from 1H NMR, FTIR, GPC, rheological measurements and model experiments showed that chemical structures of activating group Z and leaving group R played a key role in the molecular structures and melt properties of modified PP samples. The presence of S-allyl N-pyrrolocarbodithioate with stronger activating group N-pyrrolo and easier leaving group allyl led to the formation of long chain branching structure with more branched points (comb-like topology). The possible reactions in the above systems were also discussed.

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