Polyolefine polyamide graft copolymers

Keywords Block copolymers, Interface reactive injection moulding, Polyamide degradation, Polyolefine polyamide graft copolymers, PTFE polyamide materials... 

Polypropylene block and graft copolymers are efficient blend compatibilizers. These materials allow the formation of alloys, for example, isotactic polypropylene with styrene-acrylonitrile polymer or polyamides, by enhancing the dispersion of incompatible polymers and improving their interfacial adhesion. Polyolefinic materials of such types afford property synergisms such as improved stiffness combined with greater toughness. 

The most common method for compatibilizing PA/amorphous polyolefin blends involves graft copolymer formation by reaction of polyamide... 

PA/PP blends have been compatibilized through graft copolymer formation between polyamide amine end-groups and pendent anhydride groups on a functionalized polyolefin (Table 5.12). 

PA/PO blends have been compatibihzed through graft copolymer formation between polyamide amine end-groups and pendent anhydride groups on a functionalized styrene copolymer. Also, in one example [Lu et al, 1995] this ternary blend is compatibihzed through copolymer formation between PA and anhydride-functionalized polyolefin (Table 5.14). 

Polyethylene, 70 wt% PE polyamide, 20 wt% PA-66 and 3 wt% of ethylene-fumaric acid graft copolymer were mixed to reduce moisture permeation and to improve impact strength. In 1982 DuPont introduced PA/PO blends, Selar , to be used as additive to polyolefin to reduce permeability... 

As we have indicated above the presence of these block and graft copolymers at the interface between two polymer melts has a substantial influence on the interfacial tension between the two melt phases (see Section 5.7). This effect has been investigated by various researchers [26, 44 to 47]. Typical results are shown in Table 6.1 for the polyethylene-poly(ethylene terephthalate) system [47]. This indicates that block copolymers where the two segments dissolve in different melt phases cause substantial reductions in interfacial tension. This also is the case when the block/graft copolymer are added they are chemically react with the molecules of one of the phases as in the case of the maleated polyethylene and maleated ethylene copolymers with polyamides or polyesters in blends with polyolefins. 

Direct chemical reaction between functional groups, so that graft or block copolymers are formed. For example, a polyolefin may be maleated so that it may then react with a polyamide during melt blending to give an imide that functions as the compatibilizer. 

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