Polypropylene-polyamide 6 blends reactive blending

Els and McGill [48] reported the action of maleic anhydride on polypropylene-polyisoprene blends. A graft copolymer was found in situ through the modifier, which later enhanced the overall performance of the blend. Scott and Macosko [49] studied the reactive and nonreactive compatibilization of nylon-ethylene-propylene rubber blends. The nonreactive polyamide-ethylene propylene blends showed poor interfacial adhesion between the phases. The reactive polyamide-ethylene propylene-maleic anhydride modified blends showed excellent adhesion and much smaller dispersed phase domain size. 

Toughened Polypropylene-Polyamide 6 Blends Prepared by Reactive Blending... 

Helmert, A., Champagne, M.F., Dumoulin, M.M. and Fritz, H.G. (1995) Compatibilization of polypropylene/polyamide-bb blends via reactive blending with maleated polypropylene, in Proceedings of the Conference on Polyblends 95, October 19-20, Boucher e, Canada, National Research Council Canada, BouchervUle, Canada. 

SEM photomicrograph (magnification lOOOx) of cryofracture surfaces showing the absence of adhesion in melt-blended 70 wt% polyamide 6/15 wt% polystyrene/15 wt% polypropylene ternary blend. All the visible particles are detached from the matrix of polyamide 6 as an indication of absence of interfacial adhesion between the minor phases (PS, PP) and the host matrix polyamide 6. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two- and Three-Phase Polymer Blends Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 200 under the supervision of C. Harrats and G. Groeninckx.)... 

Everaert et al. prepared poly (methylene oxide)/ polystyrene-poly (2,6-dimethyl-l, 4 phenylene ether) (POM/(PS/PPE)) and studied the fractionated crystallization of POM when different glass transition temperature matrices were produced by changing the composition of the PS/PPE phases [305,306]. Wilkinson et al. produced a series of polypropylene/polyamide 61 SEES ternary blends. The progressive replacement of SEES by reactive SEES-g-MA reduced the interfacial tension between the components and then the blends could exhibit significant variations in mechanical and thermal behavior [307]. 

This technology was first commercially applied to polyurethane blend [121] and patented as Rimplast (for Reactive Injection Molding), but many polymers have since been blended with polysiloxane thanks to this method polyethylene [122], polypropylene [122,123], polyamide [124-130], polyesters [128,131-133], poly(phenylene ether) [134], fluorocarbons [135] and many more. Many of them include reinforcing fillers such as fumed silica. The silicone base involved can moreover contain reactive groups such as the epoxy group [136,137]. A typical silicone base useful for these blends was de-... 

The second system was based on two semi-crystalline polymers polypropylene and polyamide. To attain potential reactivity, polypropylene was first grafted with maleic anhydride and the results of this radicalar melt-grafting are presented. The final blend was obtained in one-step extruding of the two homopolymers and the reactive polypropylene. 

Polyamide-6 (PA-6) and polypropylene (PP) are both semi-crystalline polymers and the combination of an engineering plastic (PA) and the best commodity product (PP) could lead to new blends with Interesting Intermediate properties. We tested systems containing 50 wt% of each product and the ones obtained by addition of 3% of the reactive PP-g-AM resulting from previous continuous grafting in the extruder. The blends were prepared by simple mixing in the ZSK 30 twin-screw extruder and the samples for mechanical testing were molded by injection in a BILLION equipment. 

Table 9 Material properties of polypropylene and polyamide 6 blends after reactive extrusion...

Melt blending of PA-6 (or 66) with such an anhydride functionalized polypropylene causes a fast graft copolymer reaction between the polyamide and PP at the interface, which subsequently compatibilizes the blend. Some commercial polyamide/polypropylene blends may utilize such types of reactive compatibilization techniques. Properties of commercial PA/PP blends, both unfilled and glass filled grades, are shown in Tables 15.18 and 15.19. Typically, these blends... 

Wu, Y, Yang, Y, Li, B., and Han, Y. 2006. Reactive blending of modified polypropylene and polyamide 12 Effect of compatibilizer content on crystallization and blend morphology. Journal... 

The first example of reactive blending is a system containing polyamide (PA-6) and polypropylene (PP) with a small amount of maleic anhydride (MAH) (Ide and Hasegawa 1974). A coupling reaction between the amino chain end of PA with MAH leads to the in situ formation of a PA-PP graft copolymer at the interface (see Fig. 8.35). 

An illustration of a composite (encapsulated droplet-in-matrix) phase morphology in melt-blended ternary blend 70 wt% polyamide/15 wt% polystyrene/15 wt% polypropylene. The droplet is polypropylene, the encapsulating phase is polystyrene, and the matrix is polyamide. (From G. Lei, Development of Three Phase Morphologies in Reactively Compatihilized Polyamide 6/Polypropylene/Polystyrene Ternary Blends, master s thesis, Katholieke Universiteit Leuven, Belgium, 2004.)... 

Two elastomers are made based on statistical copolymers of ethylene and propylene EPDM, in which the diene portion, D, serves as a cross-linking site, and its non-cross-linking counterpart, EPM. Since these materials have few reactive sites, they are relatively impervious to oxidation or hydrolysis. Frequently they are blended with either polyamides or polypropylene to form impact-resistant plastics see Section 13.8. 

In order to be able to modify and control the interfadal interactions in the above-described manner, it is extremely important to monitor the structure of the interfadal layer. Ellipsometry was used [15,40,50,51] to deted the procedure and influence of reactive compatibilization on polymer blends. In an early study, the reactive blending of polypropylene (PP) with amorphous polyamide (aPA) was carried out using maleic anhydride-grafted PP (MAH-gPP) as a reactive PP [50]. The emulsifying effect of the in situ-formed PP-aPA graft copolymer was indicated by finer particles and a better stability of the dispersed phase obtained in bulk. In accordance with these findings, ellipsometry showed that the interface established in the reactive system was rather thick (ca. 40 nm), indicating an improved compatibility. 

Similarly to non-reactive blends, Scott and Sundararaj showed that the major reduction of the particle size of reactive blends, e.g., polyamide/polystyrene and polypropylene/ polystyrene prepared in batch mixer or in twin-screw extruder, occurred during the softening/melting step of the blend components with, however, a clear influence of the chemical reaction at the interface [63, 46]. 

First, Figs. 7.24 and 7.25 illustrate the experimental results when monitoring the morphology development in the case of a maleated polypropylene (mPP)-polyamide (PA) binary reactive blending system (where A-1 1st kneading zone, A-2 intermediate, A-3 2nd kneading zone, A-4 die exit). 

The polymers used in this research are described in Table 1. Several mrrltiphase materials were prepared from these polymers to evduate the performance of the new miniature mixer. The blends were polystyrene/polypropylene (PS/PP), polyethylene/ polycarbonate (PE/PC) and polystyrene/polyamide (PS/PA) mixed at an 80/20 weight ratio. The polyamide was an amorphous nylon from DuPont (Zytel 330). A reactive polymer blend system, polystyrene-co-maleic anhydride (PSMA) blended with PA was also studied at 80 20 weight ratio. 

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