Polymer blends, functional groups

A novel approach is used to compatibilise a blend without addition of premade copolymers or functionalisation of polymers lacking functional groups. Solid-state shear pulverisation (S3P) processes polymers at temperatures below the melt transition (for semicrystalline polymers) or the glass transition (for amorphous polymers). The polymer, introduced as pellets or flakes into the pulveriser. 

Blends of condensation polymers containing functional groups internally or at chain ends (such as polycarbonates, polyesters, polyamides, and the like) may undergo intermolecular exchange reactions when mixed in the molten... 

By modifying the functional groups they can be used,for example, as crosslinkers in high solid or powder coatings and in thermosets. Because of their good miscibility and low melt viscosity, they find applications as melt modifiers and as blend components. Modified hyperbranched polymers, like alkyl chain substituted poiy(ether)s and po-ly(ester)s sometimes exhibit amphiphilic behavior.They can, therefore, be used as carriers for smaller molecules,for example, dyestuff into polypropylene. 

As pointed out in the introduction, because of the ease with which the carbonyl group can be chemically modified, the polyketones should be excellent starting materials for the synthesis of other classes of functionalized polymers. Indeed, a large number of derivatives of the C2H4—CO copolymer has been prepared and, not surprisingly, the vast majority of these are described in the patent literature. Patents concerning the use of these derivatives in polymer blends have also appeared but these are outside the scope of this review. 

Apparently, with a very small interphase thickness the two end-cap groups are too few and not easily accessible to affect compatibilization. On the other hand, when four anhydride (An) groups are attached, randomly on each PDMS chain, then the blend of 20% PDMS/4-An and PA 6/di-amine have a very fine and stable morphology (ca 0.5 pm). Thus, the amount of interfacial reaction product, although diminished by small < / values of the unmodified polymer components, is promoted by the larger number and more accessible functional groups in either or both of the reactive components. Finally, Macosko and co-workers (62) have estimated that the minimum fraction of the interphase that has to be covered by reacted compatibilization products to achieve fine and stable morphologies is about 0.2. 

---