Kinetic polymer melt intercalation

J. Li, C. Zhou, G. Wang, and D. Zhao. Study on kinetics of polymer melt intercalation by a rheological approach. Journal of Applied Polymer Science, 89 2 (2003), 318-323. 

As widely available and easy method, WAXS is often used to define the nanocomposite structure and rarely to study the kinetics of the polymer melt intercalation. Most commonly, WAXS is applied for studies of layered nanocomposites with addition of montmorillonite (MMT) or silicates. This method, based on Bragg s law, enables understanding the intercalated or exfoliated structure of nanocomposites by describing direction, intensity and shape of the basal reflection resulting from the distribution of nanofiller layers [64]. X-ray patterns presented in Fig. 21.37 prove that intercalation of polymer chains is followed by increase of... 

Shen et al. studied nanocomposites obtained by melt intercalation based on PEO/Na -MMT and PEO/B34 (bentonite with dimethyl ditaUow ammonium cations)The presence of water molecules in the interlayers of MMT did not have any significant effect on the melt intercalation process, i.e. saturation ratio and final layer distance in the composites. In a hybrid composite PEO/B34/Na" -MMT, the PEO first intercalated into B34, and later into MMT. Polymer molecular weights did not affect the nanocomposite structure or saturation ratios of polymer to layered silicates, but did affect the kinetics of melt intercalation. ... 

Vaia R A, Jandt K D, Kramer E J, Giannelis E P (1995), Kinetics of polymer melt intercalation . Macromolecules, 28, 8080. 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

This system does not increase the carbon monoxide or soot produced during the combustion, as many commercial FRs do [233]. Other polymer silicate nanocomposites based on a variety of polymers, such as polystyrene, epoxy and polyesters, have been prepared recently by melt intercalation [236]. A direct synthesis of PVA-clay (hectorite) complexes in water solution (hydrothermal crystallization) was reported [237]. It was assumed that the driving force of this phenomenon, at least kinetically, can be described in terms of a simple diffusion reaction of polymers/monomers into clay-layered structures. 

Static Melt Intercalation This method involves the mechanical mixing of a polymer with an appropriately modified filler and subsequent annealing above the softening temperature of the polymer. This approach provides the best route to test with sensitivity the thermodynamic arguments detailed above and to yield well-defined systems for fundamental studies. However, due to the quiescent processing conditions (absence of external shear), which eliminate any mechanical contribution for the dispersion of fillers, and to the very slow interca-lation-exfohation kinetics," " such methods are typically very slow, thus having very limited applicabihty in industry. 

The latter effect is particularly important for polymers that possess very high attractions for the filler surfaces and can be kinetically arrested under static melt intercalation." In many cases, end users of polymer nanocomposites are hesitant to incorporate nanofillers directly (in the form of ultrafine powders) in their current processing practices, and the concentrate or masterbatch two-step approach is preferred. In this case, first a polymer nanocomposite (concentrate) is formulated at relatively high filler loadings of about 25 wt%, which can be processed and palletized to look like a normal polymer resin. This concentrate is subsequently diluted (i.e., let down) to the desired filler loading by pure polymer resin (cf. below). 

D. Wu, C. Zhou, and H. Zheng. A rheological study on kinetics of poly (butylene terephthalate) melt intercalation. Journal of Applied Polymer Science, 99 4 (2006), 1865-1871. 

The existence of MAH groups along the EVA chains may disrupt the optimum combination of EVA with Cloisite SOB, or too strong polymer-organic silicate layer interactions may increase the frictional coefficient associated with polymer transport within the interlayer and result in slower melt intercalation kinetics. ... 

The intercalation of polymers (PS, PEO, polypropylene, " etc.) from their melts into a silicate lattice is also a promising procedure. Molecular dynamics calculations and the kinetics of formation of these intercalates were considered in this study. A new line of investigation involves direct hydrothermal crystalhzation of sihcate layers from a polymer gel. This approach extends the range of intercalated polymers because it allows one to use compounds that do not contain functional groups. 

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