Physical compatibilization

Physical compatibilization that generates fine, non-equilibrium morphology, and locks it by nucleated crystallization. The process may take place either in the molten or solid state. 

Physical compatibilization Compatibilization by physical means high stress field, thermal treatment, irradiation, etc. 

By adding a nonreactive or physical compatibilizer, separately synthesized, such as block or graft copolymers with segments capable of specific interactions, and/or chemical reactions with the blend constituents. 

FIGURE 1.5 Variation of the first normal stress difference versus strain for (O) uncompati-bilized blends of polydimethylsiloxane (PDMS) in polyisoprene (PI) and for ( ) 10% com-patibilized blends of polydimethylsiloxane (PDMS) with polyisoprene (PI). (Adapted from Van Hemelrijck Ellen. Effect of physical compatibilization on the morphology of immiscible polymer blends. PhD thesis, K U Leuven, 2005.)... 

Van Hemelrijck Ellen. Effect of physical compatibilization on the morphology of immiscible polymer blends. PhD thesis, K U Leuven, 2005. 

Addition of a physical compatibilizer is obviously the simplest and most straightforward technique for the average plastics processor. However, the compatibilizer must be matched to the polymers in the blend, with segments either identical to the base polymers, or else similar, miscible, or at least compatible with them. Such tailor-made compatibilizers are rarely available commercially, and when they are, they are usually speciality materials, made in small volume and quite expensive. For many polyblend systems, they do not exist at all, and require considerable research and custom synthesis, which are very expensive. 

As noted earlier for physical compatibilizers, the compatibilizer for polyA + polyB might optimally be a block or graft copolymer of A-B, but often it may be easier, and just as effective, to make a compatibilizer AM2 where C is merely compatible with B, or even C D where C is compatible with A and D is compatible with B [7, 8,11, 31]. Such compatibihty may come from similarity, polarity, hydrogen bonding, or ionic groups. Incidentally, these may actually be superior to primary covalent bonds, because they generally weaken on heating and thus facUitate thermoplastic processability [8, 9]. 

A compatibilizer must be located at the interfaces to play its roles. This determines, to a great extent, the pros and cons of physical and reactive compatibilization methods. However, direct comparisons are scarce because of experimental difficulties. By direct comparisons it is meant that at least the molecular architectures and the concentrations of the interfacial agents employed in both compatibilization methods are the same or very similar. Unfortunately, these two minimum requirements can hardly be met in practice. Nevertheless, one would expect that an in-situ generated interfacial agent (reactive compatibilization) would be more efficient than an externally added one (physical compatibilization) provided their molecular architectures and concentrations are the same. Nakayama et al. [30] confirmed this expectation by comparing PS/PMMA (70/... 

Oommen Z, Groeninckx G, Thomas S. Dynamic mechanical and thermal properties of physically compatibilized natural rubber/poly(methyl methacrylate) blends by the addition of natural rubber-graft-poly(methyl methacrylate). J Polym Sci B Polym Phys 2000 38(4) 525-36. 

Dufresne et al. [153] noted that surface adsorption of potyojq ethylene chains on the surface nanocrystals can improve dispersibility and thermal stability of nanocrystals during the melt processing of polyethylene based nanocomposites. The chemical modification of cellulose is a most effective approach to avoid irreversible agglomeration during drying, and enhance the adhesion between nanocellulose and nonpolar matrices [132]. Dufresne et al. [98] showed also, that chemical and physical compatibilization imparted by poly(ethylene glycol) and polyoxyethylene layers promoted the interfacial interaction between cellulosic nanoparticles and polystyrene. 

---