Types of In Situ Chemical Reactions Involved

The chemical reactions used in reactive blending depend on the types of the functional groups one is able to graft to or incorporate into a polymer chain. Liu and Baker [12] have reviewed and listed most of the reactions, reactive groups as well as functional polymers encountered in reactive blending and this is updated in Chapter 2. 

The types of chemical reactions that are frequently used in reactive blending can be grouped into imidization, ring opening and amidation reactions, and interchange reactions between polycondensates. Other types of reactions that are less frequently used include esterification, urea and urethane link formation, ionic bonding, and concerted addition in which a comonomer such as maleic anhydride is copolymerized with a double bond of an unsaturated polymer. 

Imidization is a very well known amine/anhydride reaction in organic chemistry. It is a spontaneous reaction, does not require a molecular catalyst and has the advantage to take place also in the absence of solvent at high melt temperature. Examples of reactive blends making use of an imidization reaction are listed in Table 3.1. Amine bearing polymers 

Co-reactive groups Reactive copolymers Blends References 

Amidation results from the reaction of carboxylic acid and amine groups. It is less efficient and less fi equently used compared to the imidization reaction described above. Substantial differences in reactivity between primary, secondary and tertiary amine towards carboxylic acid groups were reported in the literature. The primary amine was found to be more reactive towards carboxylic acid groups attached to polyolefins backbone than secondary or tertiary amines [13]. 

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