POLYMERIC COMPATIBILISER

There are a number of polymeric compatibilisers, e.g., block/graft copolymers like tri-block copolymers of SBS used mostly in styrenic blend compatibilisation, and functionalised polymers with certain functional groups (epoxidised or maleated), which can act like a surfactant . 

Datta, S. and Lohse, D. J. (1996). Polymeric Compatibilisers. Munich, Hanser. 

Usually polymeric substances of appropriate chemical structure and morphology which promote the miscibility of incompatible materials. Block copolymers are especially useful surfactants at the polymer/polymer interface because the two blocks can be made up from molecules of the individual polymers to be mixed. Typical compatibilisers in polymer blends are LDPE-g-PS in PE/PS CPE in PE/PVC acrylic- -PE, -PP, -EPDM in polyolefin/PA and maleic-g-PE, -PP, -EPDM, -SEBS in polyolefin/polyesters. 

The use of polysilanes as photoinitiators of radical polymerization was one of the hrst means whereby they were incorporated within block copolymer structures [38 0], albeit in an uncontrolled fashion. However the resulting block copolymer structures were poorly defined and interest in them principally lay in their application as compatibilisers for polystyrene (PS) and polymethylphenylsilane blends PMPS. The earliest synthetic strategies for relatively well-defined copolymers based on polysilanes exploited the condensation of the chain ends of polysilanes prepared by Wurtz-type syntheses with those of a second prepolymer that was to constitute the other component block. Typically, a mixture of AB and ABA block copolymers in which the A block was polystyrene (PS) and the B block was polymethylphenylsilane (PMPS) was prepared by reaction of anionically active chains ends of polystyrene (e.g. polystyryl lithium) with Si-X (X=Br, Cl) chain ends of a,co-dihalo-polymethylphenylsilane an example of which is shown in Fig. 2 [43,44,45]. Similar strategies were subsequently used to prepare an AB/ABA copolymer mixture in which the A block was poly(methyl methacrylate) (PMMA) [46] and also a multi- block copolymer of PMPS and polyisoprene (PI) [47]. 

Thus, termination of oxazoline polymerization with potassium hydroxide gave hydroxy-terminated polymers, which in the presence of tin octoate were capable of initiating the anionic polymerization of -caprolac-tone [287] giving the corresponding block copolymer, acting as effective compatibiliser. 

Mixing of two or more polymeric liquids (along with an appropriate compatibiliser) to prepare polymer blends or polymer alloys. 

Reactive blending is an important method for the compatibilisation of polymer blends. Two or more immiscible polymeric components are functionalised with chemical units that are coreactive. During melt... 

Copolymerisation of these macromonomers with norbomene or norbomene acetate has yielded a series of poly(norbomene)-graft-poly-(e-caprolactone) copolymers of well-defined structures. Furthermore, PCL macromonomers were also homopolymerised in high yield into high molecular weight comb chains of narrow molecular weight distribution MJM =1.10). Such copolymers have potential applications as surface modifiers, polymeric surfactants, compatibilisers in polymer blends, and dispersion stabilisers. 

Compatibilisers make two largely incompatible polymers mix together to form a new blend or alloy. There has been a steep rise in demand for them in recent years, because polymer blends provide a fruitful way to tailor polymer properties to specific applications. They have also led to improved impact modifiers which, being polymeric, must form a blend whenever they are used. Some of the newer alloys, such as Rhodia s PA/ABS and Crompton s PP/SEBS, are highly impact-resistant. Compatibilisers are also used to improve the properties of mixed plastics waste and to compatibilise polymers with wood or mineral fillers. 

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