Control of Degradation Reactions during Radical Functionalization of Polypropylene in the Melt

Abstract

Isotactic polypropylene (iPP) gives very extensive degradation when treated with peroxides above its melting temperature in mechanical mixers or extruders. This undesired reaction is very modestly affected by maleate molecules which on the contrary actively compete with side reactions of macroradicals in the case of ethylene polymers. In this work iPP was treated in a Brabender mixer at 180 °C with peroxide and different selected molecules capable of promptly reacting with the macroradical formed on iPP chain and converting it into a more stable free radical. Furan derivatives, successfully used for iPP cross-linking without any remarkable increase of MFR, were used as free radical removers and maleic anhydride as functionalizing monomer. The results indicate a detectable improvement with respect to the use of maleic monomers and peroxide only, allowing to us get a significant grafting of functional groups and only partial degradation. Moreover, furan derivatives bearing various reactive substituents were used as functionalizing molecules. The results are discussed in the frame of the general mechanism proposed for the free radical functionalization of polyolefin in the melt.

Compatibilization of polypropylene/recycled polyethylene terephthalate blends with maleic anhydride grafted polypropylene in the presence of diallyl phthalate

“…It must be pointed out that NBS can epimerize the backbone with decrease in the PP-g-MAH crystallinity. Heteroaromatic derivatives have also been used as coagents during MAH functionalization of PP [32][33][34]. A coagent, such as butyl 3-(2-furanyl) propenoate (BFA), which has an electron donating heterocyclic aromatic ring conjugated with a double bond bearing an electron-attracting group substituent, results in a high addition rate to the tertiary polypropylene macroradical with formation of a new resonance-stabilized macroradical that limits the polypropylene degradation and improves the grafting degree.…”

Nanocomposites Based on Phyllosilicates: From Petrochemicals to Renewable Thermoplastic Matrices

“…The problem of obtaining appropriately functionalized PP can be overcome by a new radical functionalization approach involving the use of a furan derivative (BFA). This is added as coagent during the radical functionalization of PP with MAH, which can yield a wide range of PP -g -MAH samples with different DFs and molecular weights, by controlling the macroradical formation and content [86,87] . These new functionalized PP samples were recently tested in the preparation of PP/OLS nanocomposites, both as a matrix or as a compatibilizer of the system, the aim being to study the effects of both polarity and chain structure/architecture on clay dispersion and the ultimate properties of the corresponding nanocomposites.…”

Mechanism and Kinetics

“…There is a continuum between " comonomers " and " additives " : bis(2 -furanyl aldazine) and N,N ′ -p -phenylenebis(maleimide), for example, have double -bonds susceptible to attack by polymer backbone radicals, but do not propagate or undergo scission [57] . While they are considered " additives, " they behave identically to the nonhomopolymerizable " comonomers " discussed above as promoters of crosslinking and inhibitors of chain scission.…”