Nano-reactors for controlling the selectivity of the free radical grafting of maleic anhydride onto polypropylene in the melt

Abstract

This paper reports on a successful application of the concept of nanoreactors to effectively controlling the selectivity of the free radical grafting of maleic anhydride (MAH) onto polypropylene (PP) in the melt, an industrially relevant process. More specifically, a free radical initiator of type ROOR was first confined into (or encapsulated by) the galleries of an organically modified montmorillonite (o‐MMT) whose interdistance was 2.4 nm. Primary free radicals (RO ·) formed inside the o‐MMT galleries had to diffuse out before they could react with the PP backbone. The controlled release of the primary free radicals significantly increased the grafting degree of MAH onto PP and greatly reduced the level of the chain scission of the latter. Those results were better understood by electron spin resonance studies on model systems and by Monte Carlo simulations. POLYM. ENG. SCI. 46:1443–1454, 2006. © 2006 Society of Plastics Engineers.

Mathematical Modeling of the Grafting of Maleic Anhydride Onto Poly(propylene): Model Considering a Heterogeneous Medium

“…Shi et al [11] presented experiments using the concept of nanoreactors. Their nanoreactor was a solid material (montmorillonite) that contained the initiator and liberated it slowly into the medium.…”

“…The predictions of the models are in good agreement with experimental data taken from the literature for processes conducted under different conditions. flow index (an indirect measurement of the effect of the scission) [2,7,8] ; sometimes molecular weight-averages [11] and, more rarely, molecular weight distributions (MWD) are reported. [20] The grafting degree is a function of the peroxide type and concentration, MAH concentration, reaction time, temperature, rotation speed, sequence of reactant feeding, presence of stabilizers, etc.…”

“…[20] Maleation of PP involves grafting of MAH onto PP in the presence of organic peroxides, whose decomposition acts as a source of free radicals. [1][2][3][4][5][6] This process has been experimentally studied under high temperatures (molten polymer), either in batch mixers and torque rheometers [2,5,[7][8][9][10][11] or in continuous single-screw and twinscrew extruder reactors. [5,9,[12][13][14][15][16] There are also studies of this process in solution, [17][18][19] in the solid state under supercritical CO 2 , [6] or using vapor phase film surface modification.…”

Modelagem matemática do processo de enxerto de anidrido maleico em polipropileno na forma fundida.

“…Os resultados estão representados através da referência. As simulações foram feitas com os dados de Güldoğan et al (2003), Shi et al (2006), Shi et al (2001), Akzo (2007), Cha e White (2001) e Chang e White (2003). Os resultados das simulações estão detalhados a seguir.…”

“…Entretanto o maior problema deste processo é a quebra das cadeias de polímero (SHI et al, 2006 Caminho D: O radical primário reage com um átomo de hidrogênio do PP para formar um macro-radical.…”