Compatibilizers copolymers

However, often it is difficult to produce suitable graft or block copolymers for important commercial applications. Alternatively, these compatibilizing copolymers can be generated in situ during the blend preparation through polymer-polymer grafting reactions using functionalized polymers (38). 

Tables 5 and 6 summarize key properties and applications for miscible and immiscible blends which are either commercial as of 1996 or were commercialized in the past (2,314—316,342,343). Most of the listed blends contain only two primary components, although many are compatibilized and impact-modified. Consequently, an immiscible system consisting of two primary components or phases may contain impact modifiers for each phase and a compatibilizer copolymer, for a total of five or more components.

First, the copolymer is automatically formed at the interface between the two immiscible polymers where it is needed to stabilize morphology. In contrast, when a compatibilizing copolymer is added as a separate entity to a polymer blend, it must diffuse to the polymer-polymer interface to be effective for promoting morphology stabilization and interphase adhesion. However, the added copolymer may prefer to form micelles as a separate phase that is useless for compatibilization. 

Table 5.3 shows dramatic examples of the stabilization of dispersed phase morphology in the presence of a compatibilizing copolymer. In all examples essentially no change in dispersed phase particle size occurs after annealing under static conditions for up to 90 min. The data shown in this Table 5.3 should be compared with those presented in Table 5.2, where the dispersed phase mean dimensions were presented for similar, uncompatibilized blends. 

Since there are multiple reactive sites on the epoxide-containing polymers, some crosslinked copolymer may result if the acid-containing polymer is functionalized at both ends. The proportion of crosslinked copolymer formed also depends upon blend composition and processing conditions. An example is also included in this section where a compatibilizing copolymer is postulated to form by reaction between acidic phenolic end-groups on polycarbonate and epoxide groups grafted to PP [Zhihui et al., 1997]. 

Hu and Lambla [1995] have blended EM Ac (90-65 parts) with mono-hydroxy-terminated PS (10-35 parts) in an internal mixer at 180-220°C in the presence of dibutyltin dilaurate or dibutyl-tin oxide catalyst. A compatibilizing copolymer arises from transesterification between pendent ester groups of EMAc and terminal hydroxy groups of PS. The effects on blend properties of PS molecular weight were reported. The effects of processing conditions and addition of solvent on conversion kinetics were studied. 

Copolymer formation by miscellaneous reactions Hourston et al. [1991] have prepared compositions of 60-0 parts PBT and 16-40 parts EPDM in the presence of 0-60 parts copolymer of PBT with maleate ester (3.5% maleate) using a TSE at 255°C. A compatibilizing copolymer resulted from the crosslinking reaction between maleate olefinic groups and EPDM olefinic groups. Blends were characterized by mechanical properties and TEM. Model studies were performed to understand the crosslinking process. Blends were also prepared using an internal mixer at 250°C. 

Compatibilizing copolymers have been formed by direct reaction between pendent alcohol groups of... 

A compatibilizing copolymer may be formed through reaction between carboxylic acid groups grafted onto a PO chain and acrylate epoxide groups grafted onto a PP chain. In an internal mixer Liu et al. [1993] have prepared compositions comprising 20 parts NBR-g-AA, 0-75 parts PP and 0-25 parts PP-g-GMA (0.8% GMA). The blends were characterized by torque rheometry, SEM, FTIR, and mechanical properties vs. use of unfunctionalized NBR and vs. different GMA levels. 

Immiscible polymer blends have been compatibilized through formation of a compatibilizing copolymer linked by ionic association instead of by covalent bonding. Although many examples have been published, most of these involve solutionmixing of the two immiscible polymers, viz. [Natansohn et al., 1990]. However, the examples given in this section describe only such polymer blends prepared by melt mixing. 

It has been reported that neo-alkoxy titanates or zirconates can re-polymerize polymers or joint several polymers into compatibilizing copolymers. These compounds have been used to repair degraded PEST or PC during reactive extrusion. For example, phosphato titanate (Ken-React Lica-12 from Kenrich Petrochemicals, Inc.) was used to ... 

Compatibilizer, block copolymer Compatibilizer, copolymer Compatibilizer, co-solvent Compatibilizer, graft copolymer Compatibilizer, ionic/ionomeric... 

It is also not the purpose of this chapter to describe examples of compatibilized polymer blends formed by polymerization of a monomer in the presence of a second polymer. In these cases, the growing polymer chain may react with functionality on the second polymer to form a certain fraction of compatibilizing copolymer. 

Graft copolymer formation has been the most common method of forming a compatibilizing copolymer between two immiscible polymers during reactive compatibilization. As shown in Table 5.4, there are at least four processes for... 

Examples of polyamide blends are listed in alphabetical order of the second polymer in the blend unless otherwise noted. When copolymer characterization was not performed, the stmcture of the compatibilizing copolymer is inferred from the functionality location on each of the two polymers. In some cases, more than one type of compatibilizing copolymer may have formed. 

---