Compatible Compatibilising effect

Diblock copolymers, especially those containing a block chemically identical to one of the blend components, are more effective than triblocks or graft copolymers. Thermodynamic calculations indicate that efficient compat-ibilisation can be achieved with multiblock copolymers [47], potentially for heterogeneous mixed blends. Miscibility of particular segments of the copolymer in one of the phases of the bend is required. Compatibilisers for blends consisting of mixtures of polyolefins are of major interest for recyclates. Random poly(ethylene-co-propylene) is an effective compatibiliser for LDPE-PP, HDPE-PP or LLDPE-PP blends. The impact performance of PE-PP was improved by the addition of very low density PE or elastomeric poly(styrene-block-(ethylene-co-butylene-l)-block styrene) triblock copolymers (SEBS) [52]. 

Compatibility of PE with PVC is improved by poly(ethylene-graft-vinyl chloride) or partial chlorinated PE. To compatibilise blends of PE with PET, common for the scrap of beverage bottles, EPDM or SEBS are effective additives [56]. 

Generally, octadecyl-trimethoxy silane, dodecyl-trichlorosilane and y-aminopropyl-trimethoxy-silane are used for the compatibilisation of nonmiscible or poorly miscible polymer-polymer systems. These compounds can connect to the apolar plastic constituent by their aliphatic groups via both physical and chemical bonds while the silane groups connect to the other polar polymer constituents. Figure 9.4 summarises the compatibility effect of commonly used siloxane-type compatibilisers. 

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