Morphology reactive blends

Fig. 9 Plausible representation of morphology evolution of reactive blending of immiscible and miscible blends...

Y. Li and H. Shimizu, Improvement in toughness of poly(l-lactide) (PLLA) through reactive blending with acrylonitrile-butadiene-styrene copolymer (ABS) Morphology and properties, Eur. Polym. J., 45 (3) 738-746, March 2009. 

We have previously used the term interfacial reaction to describe mixing between two reactive blend components. In reality, as we have seen in the Example 11.2, there is an interphase that is formed on the surface of the dispersed phase where molecules of both components can be found and react (66,67). If the nonfunctionalized blend components have high immiscibility, then the thickness, Si, of the interphase around the droplets, as well as the volume of the interphase, Vh will be small and, thus, the probability of the functional groups to react forming compatibilizing products will be low, giving rise to coarse and not very stable morphologies. Helfand (66) defines Si as... 

M. Marie, N. Ashuror, and C. W. Macosko, Reactive Blending of Poly- (dimethylsiloxane) with Nylon 6 and Poly (styrene) Effect of Reactivity on Morphology, Polym. Eng. Sci., 41, 631-642 (2001). 

Marie M, Ashurov N, Macosko CW (2001) Reactive blending of poly(dimethyl silox-ane) with nylon 6 and polystyrene effect of reactivity on morphology. Poly Eng Sci 41 (4) 631—642... 

The formation of compatibilizer frequently occurs by interfacial reaction of the modified polymers. An example is the use of maleic anhydride grafted to a polyolefin elastomer (EPM/EPM-g-MA) as the interfacial additive for reactive blending with a polyamide, nylon-6 (Van Duin et al., 2001), in a twin-screw extruder. It was found that the consumption of MA occurred rapidly and different blend morphologies were produced. However, it was found that the nylon-6 degraded during processing, due to the reaction of anhydride with the... 

Reactive blending of thermoplastic starch/polymer blends has been examined recently and aims to increase properties and performance via control of blend morphologies. Mani [58, 59] examined different techniques for compatibilising starch-polyester blends. They examined development of maleic anhydride grafted polyester/starch blends and starch-g-polycaprolactone... 

In 1983, Monsanto developed blends with co-continuous morphology, Triax 2000. These alloys comprised PC, ABS, and styrene-methylmethac-rylate-maleic anhydride (SMMA-MA) [Jones and Mendelson, 1985]. One year later, PC was reactively blended with either ABS, SAN-GMA, and NBR, or with graft copolymers of acrylonitrile-butadiene-a-methyl styrene-methyl-methacrylate (MeABS) and acryloiutrile-a-methyl styrene-methyl methacrylate copolymer (MeSAN) [Kress et al., 1986]. The blends were commercialized by Bayer as Bayblend . 

Amorphous PA (20) / S-IPO (1% IPO) (80) internal mixer at 200°C / torque rheometry / selective solvent extraction / SEM study of morphology development in reactive and in non-reactive blends Scott and Macosko, 1995... 

For either reactive or non-reactive blends in an extruder, internal mixer, or a miniature cup-and-rotor mixer, similar morphological features were observed. Initially, during melting, the polymers were stretched into sheets and ribbons, which broke into fibers, then in turn into drops. One reason that may explain the reported differences in morphology is the concentration of the dispersed phase — 5 vol% was used by the first authors, whereas > 20 wt% by the latter. More detailed information of this, as well as on the topic discussed in the following part, will be found in Chapter 9 Compounding Polymer Blends. 

Poly(styrene-co-maleic anhydride) (SMA) is frequently mixed with SAN before the reactive blending with PA [Takeda and Paul, 1992]. Much attention has been paid to morphology control during the reactive processing [Serpe et al, 1990 Campbell et al., 1990 Willis and Favis, 1990]. Frequently, a third polymer is added as a com-patibilizer for binary systems, e.g., MA-grafted SEES to compatibilize (and impact-modify) blends of PE with PET [Carte and Moet, 1993]. 

Other types of morphological changes during blending in TSE were also observed [Sundararaj et al., 1992, 1995]. The authors reported that both reactive and non-reactive blends in an extruder, internal mixer, or a miniamre cup-and-rotor mixer, show similar morphological features. Initially, during the melting, the polymers stretch into sheets and ribbons that first broke into fibers then into drops. 

The desired compatibilization can be obtained by different methods such as the addition of a third component (copolymer or functional polymer) or by inducing in situ chemical reactions (reactive blending) among blend components, leading to the modification of the polymer interfaces and tailoring the blend phase structure and the final properties. The final properties of a blend will be determined not only by the components properties but also by the phase morphology and the interface adhesion, both of which determine the stress transfer within the blend and its end-use applications. 

Nakason, C., Saiwaree, S., Tatun, S., and Kaesaman, A. 2006. Rheological, thermal and morphological properties of maleated natural rubber and its reactive blending with poly (methyl methacrylate). Polymer Testing 25(5) 656-667. 

Mar Martuscelli, E., Musto, P., Ragosta, G., Scarinz, G. Reactive blending of thermosets Molecular, morphological and mechanical analysis. Angew. Makromol. Chem. 211 (1994) 159-190. 

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