Solid‐state modification of isotactic polypropylene (iPP) via grafting of styrene. II. Morphology and melt processing

Abstract

Grafting of vinyl monomers onto isotactic polypropylene (iPP) in the solid state represents a convenient route to chemically modify iPP and, consequently, its properties. Solid-state modification can be carried out on iPP powder directly from the polymerization reactor. The modified powder is then processed in the melt, usually with the addition of fillers and/or additives, to obtain the final product. In this work we have studied the effect of melt processing on the morphology of solid-state polymerized PP/polystyrene (PS) blends, i.e., of a iPP powder previously modified in the solid-state with styrene (St) and optionally in the presence of divinylbenzene (DVB). A series of samples containing different amounts of PS and displaying different grafting efficiencies were investigated before and after processing in the melt. Transmission electron microscopy, scanning electron microscopy, and solid-state NMR were used to investigate the morphology on different length scales. It was shown that PS coalescence during processing can be hindered, thereby stabilizing the initially polymerized iPP/PS blends morphology. Indeed, reducing the PS amount in the blend or increasing the grafting efficiency resulted in less coalescence of the PS domains. Crosslinking of the PS phase during the solid-state polymerization resulted also in a very fine but heterogeneous morphology.

Rheology and morphology of polypropylenein situgrafted and blended with methyl methacrylate/n-buthylacrylate copolymer

“…The grafting process can be quantified by various means such as titration method , gravimetrically and using Fourier transform infrared spectroscopy (FTIR) instrument . In some researches, a good agreement has been observed between the results obtained by these various methods in evaluating of grafting level of a vinyl monomer on to PP . Sometimes using FTIR results was preferred because of large experimental error involved in measuring the weight increase after grafting .…”

“…Solid state grafting of vinyl polymerizable monomers such as styrene and n ‐butyl methacrylate on to PP powder bellow its melting point is used in some research works. In this way, they tried to avoid the degradation of PP via β‐scission reaction which may happens in melt grafting at high temperature.…”

Morphology stabilization of the polypropylene/polystyrene nanoblends prepared by diffusion and polymerization of styrene in isotactic polypropylene pellets during melt mixing by the incorporation of divinylbenzene

“…[1][2][3] For most polymer blends processed under traditional extrusion conditions, it is hard to achieve nanoblends as a limited dispersed-phase particle size exists due to the equilibrium between drop breakup and coalescence during melt processing. [6][7][8][9] For example, Picchioni et al 6,7 prepared isotactic polypropylene/polystyrene (iPP/PS) blends with PS particle size of 10-50 nm in the amorphous phase of iPP microparticles via diffusion and in situ polymerization of styrene (St) in porous iPP powders. [6][7][8][9] For example, Picchioni et al 6,7 prepared isotactic polypropylene/polystyrene (iPP/PS) blends with PS particle size of 10-50 nm in the amorphous phase of iPP microparticles via diffusion and in situ polymerization of styrene (St) in porous iPP powders.…”

“…4,5 In contrast, in situ polymerization of one monomer inside a polymer matrix is demonstrated to be a feasible and promising method to produce nanoblends. [6][7][8][9] For example, Picchioni et al 6,7 prepared isotactic polypropylene/polystyrene (iPP/PS) blends with PS particle size of 10-50 nm in the amorphous phase of iPP microparticles via diffusion and in situ polymerization of styrene (St) in porous iPP powders. Han et al 8,9 achieved nanoblends via supercritical CO 2 -assisted impregnation of monomer and subsequent polymerization in PP films.…”

Nonisothermal crystallization kinetics of polypropylene/polypropylene‐g‐polystyrene/polystyrene blends

“…Their blends usually result in serious phase separation, low interfacial adhesion, and poor mechanical properties. As a compatibilizer, the PP‐ g ‐PS copolymer actually improves the interfacial adhesion and produces a finer dispersion mixing of PP/PP‐ g ‐PS/PS polymer blends and, thus, enhances the mechanical properties 4–11. Researchers have reported the development of morphologies and the rheological and isothermal crystallization behaviors of PP/PP‐ g ‐PS/PS polymer blends in detail.…”