Compatibilizers for polymer blends

Short block copolymers with well defined number of units in the blocks could be applied as selective absorbents, compatibilizers for polymer blends, components for polymeric membranes, etc. 

Styrene-containing block copolymers are commercially very important materials. Over a billion pounds of these resins are produced annually. They have found many uses, including reinforcement of plastics and asphalt, adhesives, and compatibilizers for polymer blends, and they are directly fabricated into articles. Most styrene-containing block copolymers are manufactured using anionic polymerization chemistry. However, anionic polymerization is one of the more costly polymerization chemistries because of the stringent requirements for monomer and solvent purity. It would be preferred, from an economic cost perspective, to have the capability to utilize free radical chemistry to make block polymers because it is the lowest cost mode of polymerization. The main reasons for the low cost of FR chemistry are that minimal monomer purification is required and it can be carried out in continuous bulk polymerization processes. 

Sf methacrylate copolymers as compatibilizers for polymer blends with PMMA. Both, the calculation of interaction parameters and experimental results showed... 

Zhang Wengong, Lin Minyue, Winesett Werner Ade, et al. The use of functionalized nanoparticles as non-specific compatibilizers for polymer blends. Polym. Adv. Technol. 22 no. 1 (2011) 65-71. 

Suitable block and graft copolymers can be used as compatibilizers for polymer blends. A suitable block or graft copolymer contains a segment miscible with one blend component and another segment with the other blend component. The copolymer segments are not... 

Bicerano J. A practical guide to polymeric compatibilizers for polymer blends composites and laminates, www.plas2006.eom/uploadfile/topicfile/20063112235119.doc 2006 [accessed 20-02-2015],... 

Paul DR. Interfacial agents ( compatibilizers ) for polymer blends. In Paul DR, Newman S, editors. Polymer blends, vol. 2. New York Academic Press 1978. p. 35-62. 

One very t5 ical example for the useful application of 2D-LC is the deformulation of graft copolymers. The combination of styrene and butadiene in different copolymer stmctures is important for a huge variety of technical polymeric materials. The present application describes the analysis of the grafting reaction of methyl methacrylate onto polybutadiene by online coupled 2D chromatography. Such graft copolymers are interesting as compatibilizers for polymer blends. In order... 

However, a reactive styrene acrylonitrile copolymer (SAN)/gly-cidl methacrylate copolymer was found to be an effective reactive compatibilizer for the blends. Ethyltriphenyl phosphonium bromide was used as the catalyst. Probably, the epoxide groups react either with carboxyl or with hydroxyl groups of the PLLA end groups. This so modified polymer acts as the compatibilizer. Compatibilized PLLA/ABS blends exhibit an improved impact strength and an im-... 

The possibilities for applications of these block copolymers are extremely broad. Amphiphilic systems are of interest for all applications similar to low molecular weight surfactants. Copolymers without a water soluble block can be used e.g. for the compatibilization of polymer blends. The bulk materials offer broad applications in the field of advanced materials having outstanding mechanical properties. 

Intense commercial and academic interest in block copolymers developed during the 1960s and continues today. These materials attract the attention of industry because of their potential for application as thermoplastic elastomers, tough plastics, compatibilizing agents for polymer blends, agents for surface and interface mo dification, polymer micelles, etc. Academic interest arises, primarily, from the use of these materials as model copolymer systems where effects of thermodynamic incompatibility of the two (or more) components on properties in bulk and solution can be probed. The synthesis, characterization, and properties of classical linear block copolymers (AB diblocks, ABA triblocks, and segmented (AB)n systems) have been well documented in a number of books and reviews [1-7] and will not be discussed herein except for the sake of comparison. 

In this chapter, compatibilization of polymer blends by means of addition of a compatibilizer will be discussed. First, the theories will be summarized of the (i) interface, (ii) interphase, and (iii) compatibilization process. This brief summary is to provide a general framework for understanding the phenomena associated with compatibilization, and guidance for optimization of the process to gain maximum performance. 

Ternary blends that comprise two immiscible polymers and a copolymer are of a particular interest. They not only represent an ideal model for studying compatibilization of polymer blends, but also they have found direct commercial applications. Phase diagram information can be found in reviews by Ajji and Utracki [1996, 1997] and in Chapter 2 in this Handbook. 

Another way of compatibilizing immiscible polymer blends is by addition of a mumally miscible ingredient, a co-solvent, usually polymeric in namre. The objective here is not to generate a wholly miscible three component system, but to add just enough mutually miscible polymer. The co-solvent is to induce interactions between the immiscible polymers, thus compatibihze the blend, but preserving its two-phase structure. To help in the judicious selection of appropriate cosolvent for a given immiscible blend a partial list of miscible systems are given in Table 4.1. For more detailed information see Appendix 2 in this Handbook. 

Effective compatibilization of binary polymer blends by addition of a copolymer reduces the dispersed particles size and Vj [Anastasiadis et al, 1987 Wu, 1987 Patterson et ai, 1971]. An illustration is shown on Figure 4.15. The effect of compatibilizer addition is similar to the emulsification of the classical emulsions. In the former systems, the compatibilizer effect on the drop size and Vj follows the same behavior as the emulsion drop size reduction upon addition of a surfactant. The latter behavior is usually described as the titration curve that characterizes the surfactant efficiency. The shape of the titration curve depends on the type of emulsifier and the emulsification process, e.g., mixing time and equipment. However, the amount of emulsifier to saturate the interface also depends on the affinity of emulsifier to the dispersed phase, the size of the dispersion, the orientation of the emulsifier at the interface and its ability to prevent flocculation and coalescence [Djakovic et al., 1987]. A similar behavior is to be expected for polymer blends upon addition of a compatibilizer. 

Flow of emulsions provides the best model for polymer blends, where the viscosity of both polymers is comparable. The microrheology of emulsions provides the best, predictive approach to morphological changes that take place during flow of polymer blends. The effect of emulsifiers on the drop size and its stability in emulsions has direct equivalence in the compatibilization effects in polymer blends. 

Blending two immiscible polymers always creates the third phase — the inteiphase. In binary blends, thickness of this third phase, AZ, is inversely proportional to the interfacial tension coefficient, When the blend approaches miscibility, approaches zero and AZ goes to infinity. Thus the interphase, with its own set of characteristic parameters e.g., viscoelasticity) may dominate the behavior of nearly miscible systems, as well as that of compatibilized blends. For further details on this topic see Chapter 4. Interphase and Compatibilization of Polymer Blends. 

In addition, there has been an increasing interest in new synthetic methods for the preparation of well-defined polymers with controlled chain-end functional groups [23], such as telechelic polymers, which are characterized by the presence of reactive functional groups placed at both chain ends. These materials can then be used as precursors in the synthesis of block copolymers, as modifiers of the thermal and mechanical properties of condensation polymers, as precursors in the preparation of polymer networks, and as compatibilizers in polymer blends [24]. 

Nonetheless, Monte Carlo results suggest that in order for a copolymer to be an effective compatibilizer in polymer blends, the copolymer must be blocky in nature. This interpretation of the simulation results are in agreement with the experimental results which show that the random copolymers that are better than the diblock copolymer at compatibilizing a blend are those that are blockier than a statistical random copolymer. The copolymers that do not behave as effectively as a compatibilizer are more alternating than a statistically random copolymer. 

Liquid Crystal Polymers 533 Table 16.5 Compatibilizers for LCP Blends... 

Uses Coatings/emulsions/floor polish ingred. dispersion aid for pigments, mins., glass-filled plastics adhesion promoters in hot melt applies. compatibilizer in polymer blends and alloys coupling agent in reinforced PE and PP Manuf./Distnb. Aldrich http //www.sigma-aldrich.com... 

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