Reactive compatibilization technique

Compatibility of immiscible PP-NBR blends was improved by the reactive compatibilization technique using various modified polypropylenes. In this study. 

Greco et al. [50] studied the effect of the reactive compatibilization technique in ethylene propylene rubber-polyamide-6 blends. Binary blends of polyamide-6-ethylene propylene rubber (EPR) and a ternary blend of polyamide-6-EPR-EPR-g-succinic anhydride were prepared by the melt mixing technique, and the influence of the degree of grafting of (EPR-g-SA) on morphology and mechanical properties of the blends was studied. 

The applicability of Noolandi and Hong s theory of compatibilization of immiscible blends using block copolymers has been extended to the reactive compatibilization technique by Thomas and coworkers [75,76]. According to Noolandi and Hong [77], the interfacial tension is expected to decrease linearly with the addition... 

In comparing the different blends, the specific advantages of each type, as well as any potential overlap in performance with other type of blends have also been discussed. The fundamental advantage of polymer blends viz. their ability to combine cost-effectively the unique features of individual resins, is particularly illustrated in the discussion of crystalline/amorphous polymer blends, such as the polyamide and the polyester blends. Key to the success of many commercial blends, however, is in the selection of intrinsically complementing systems or in the development of effective compatibilization method. The use of reactive compatibilization techniques in commercial polymer blends has also been illustrated under the appropriate sections such as the polyamide blends. 

Melt blending of PA-6 (or 66) with such an anhydride functionalized polypropylene causes a fast graft copolymer reaction between the polyamide and PP at the interface, which subsequently compatibilizes the blend. Some commercial polyamide/polypropylene blends may utilize such types of reactive compatibilization techniques. Properties of commercial PA/PP blends, both unfilled and glass filled grades, are shown in Tables 15.18 and 15.19. Typically, these blends... 

Reactive compatibilization techniques using MDI, MA, etc., are emerging as successful methods for modification of interfadal interaction within the biodegradable blends and nanocomposites. 

Liao and Wu [125] prepared and characterized ternary blends of PLA and PCL, using a reactive compatibilization technique. From their results, it can be seen that the thermal and mechanical properties of the blend improved owing to better compatibilization. 

There are a variety of reactive alloying techniques available to the compounder. They typically involve the use of a reactive agent or compatibilizer to bring about a molecular change in one or more of the... 

In another approach, the SAN backbone of ABS was modified through copolymerization with maleic anhydride. This modification introduced controlled amounts of an anhydride functionality on ABS, which upon subsequent melt blending with a PA reacts to form a graft copolymer of SAN and PA which effectively compatibilizes the blend. Commercial blends of ABS with PA-6 and PA-66, introduced by Monsanto under the trade name of Triax 1000, utilize this reactive compatibilization technology [Lavengood et al, 1987]. In another technique of reactive compatibilization, commercial grades of ABS were directly modified by reactive extrusion with maleic anhydride or fumaric acid and then melt blended with PA-6 and optionally adding small amounts of functionalized EP mbber [Akkapeddi et al, 1990]. 

The technology for impact modification of polyamides has evolved significantly over a period of several years through improved methods of compatibilization and particularly through reactive blending techniques [JCray and BeUet, 1968 Murch, 1974 Epstein, 1979 Mason and TuUer, 1983]. Several commercially successful... 

Dow has prepared a compatibilized blend of PC and linear PE. The compati-bilizer used was EPDM grafted with SAN. The product has high impact strength and good melt processability. Polymer alloys with S-AMS copolymer and PP with styrene-grafted polyolefin copolymer have been reported. Triax 1000 of Monsanto is a blend of nylon and ABS compatibilized with styrene-acrylonitrile and glycidyl methacrylate terpolymer. The compatibilizer often improves the property balance of an immiscible blend. Reactive compatibilization is an emerging technique. 

The two most common compatibilization techniques of additive and reactive compatibilization differ in the origin of the compatibilizer. In the former case, the preprepared compatibilizer is added to the blend and has to diffuse to the interface during mixing. In reactive compatibilization, the compatibilizer is generated in situ directly at the interface by a chemical reaction of one or both blend... 

Understanding reactive compatibilization from the standpoint of the ultimate compatibilizer structure has been difficult in that it is formed in situ and is very difficult to extract and characterize unambiguously. One of the unforeseen advantages of the reactive blending technique to some commercial organizations is that the process can be conducted in different ways with different property outcomes. Thus, the product... 

Reactive blending is an important technique which is very frequently used for control of the phase morphology, phase stabilization and interfacial adhesion in multiphase immiscible polymer blends. Recently a lot of attention has been focused on the reactive blending process in order to understand how phase morphology develops in reactively compatibilized blends. The stability of the in situ formed copol3aner at the interface and its influence on phase morphology generation, phase co-continuity and on the crystallization behavior of the ciystallizable component(s) are crucial aspects with respect to the blend material properties. 

This severe lack of compatibility between the polyamides and conventional rubbers necessitated the development of suitable techniques for reactive compatibilization [5, 8-10]. Reactive compatibilization is defined here as the melt blending process in which two polymers containing mutually reactive functionalities react with each other at the interface generating a block or graft copolymer in situ, which compatibilizes the blend by reducing the interfacial tension and improving the interfacial adhesion (Scheme 8.2). 

The fundamentals and practice of compatibilizing polymer blends using polymeric additives, has been amply discussed in several earlier chapters of this volume. Here we describe a relatively new technique for reactive compatibilization, which involves the addition of low molecular weight components. Using many two component systems we review how some of these components show the ability to form copolymers of the two starting polymer constituents during melt processing. 

The key to solve problems of coarse morphology is to reduce interfacial tension in the melt and to enhance adhesion between the immiscible phases in the solid state. One solution is to select the most suitable blending technique so that co-continuous phase morphology can be obtained, which results in direct load sharing. The second solution is the addition of a third homopolymer or block or graft copolymer or low molecular reactive compounds, which is miscible with either of the two phases. This can be considered as non-reactive compatibilization. The third way is to blend suitably functionalized polymers, which are capable for specific interactions or chemical reactions (reactive compatibilization) [35],... 

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