Reactive modifiers

Al-Malaika, S., Ed. Reactive Modifiers for Polvmers Chapman Hall London, 1996. 

Van Duin, M. and Borggreve, R., Blends of polyamides and maleic anhydride containing polymers Interfacial chemistry and properties, in Reactive Modifiers for Polymers, Al-Malaika, S. (Ed.), Blackie Academic Professional, London, 1997. 

Properly functionalised additives can react with polymer substrates to produce polymer-bound functions which are capable of effecting the desired modification in polymer properties, hence the use of the term reactive modifiers. As an integral part of the polymer backbone, reactive modifiers are useful vehicles for incorporating the desired chemical functions to suit the specialised application. Being molecularly dispersed, the problem of solubility expressed under 2 above is avoided. Implicitly, the bound-nature of the function is not subjected to the normal problems of the loss of additives from the surface which are common with both high and low molecular mass additives. The bound nature of the function must be fully defined for the conditions of service. 

Current interest in reactive modifiers is in the areas of polymer property enhancement and improvement in additive performance. Reactive modifiers can be incorporated into commercial polymers by,... 

Tieing of reactive modifiers into polymers after their manufacture (via route 2), on the other hand, can be achieved (5.10) by either,... 

Approach ii is applicable to all thermoplastic polymers and offers considerable practical advantage since reactively modified polymers can be readily produced by normal commercial high-shear mixing procedures at no additional cost. 

REACTIVE MODIFIERS FOR IMPROVING ADDITIVE PERFORMANCE-REACTIONS DURING MELT PROCESSING... 

In the absence of oxygen or any other radical trap, however, mechanochemically formed macroalkyl radicals (scheme I, I) can be made to react with chemically reactive modifiers, RM, (see scheme Id) this forms the basis of an in-situ synthesis of polymer adducts i.e., the functionalised additive/modifier becomes chemically bound onto the polymer backbone. 

Enhancing the properties of the relatively cheap commodity plastics through the use of small amounts of reactive modifiers during melt processing (as in method 2(10 above) is both attractive and rewarding. 

A good example of a reactive modifier which has been used (14) to enhance properties of polyolefins is maleic anhydride (MA). The formation of maleic adduct in polypropylene (PP), for example, can be used to effect several modifications e.g. to improving hydrophilicity, adhesion and dyeabflity. Moreover, the polymer-maleic adduct has an availabla additional functionality to effect other chemical modifications for achieving the desired material design objectives. Reactions of MA with polymers in solution are described in the patent literature (15). 

Radiation chemistry in polymer research, 168-169 Reactive macroalkyl radicals, formation, 409 Reactive modifiers addition of reactive antioxidants on rubbers, 417 adhesion, 420,422 demanding applications, 414,416 improving additive performance during melt processing, 412 polymer bound antioxidant, 418-419/ Reduced poly(vinyl chloride),... 

Figure 14.11 Variation of the notched Izod impact strength of PET containing 20 % of an elastomeric toughening system as a function of the ratio of reactive to non-reactive modifier. It can be seen that the 30 70 reactive non-reactive mixture provides the optimum balance. The reactive modifier acts more as a compatibilizer in this system. Note units for impact strength (kJ m 2) can be converted to J nr1 by multiplying by 10...

Property Non-reactive modifier Non-reactive modifier Reactive modifier Reactive modifier ... 

Phenoxy resins can also be used for the modification of PET and PBT. Phe-noxy resins such as Paphen PKFE (Inchem Corporation) are polyhydroxyether materials with pendant hydroxyl groups that can react with the PET. Paphen phenoxy resins are reactive modifiers that can modify and upgrade brittle polymers. Such resins contain 6 % of secondary hydroxyl groups. The latter serve as reactive sites for reaction with polyesters, polyamides, polycarbonates, epoxies and phenolics. 

These authors found that to achieve supertoughness in PET by shear yielding, a reactive modifier is superior to a non-reactive rubber modifier and that a dispersed particle size and interparticle distance of 200 and 50 nm, respectively, are... 

Chlorophosphazenes (NPCI2), in the form of hexachlorocyclotriphos-phazene (m.p. 112-113°C, Inabate Co., Japan) as well as cyclic oligomers (m.p. 87-91°C, Poland) and terephthaloyl chloride (Merck, FRG), served as reactive modifiers. 

Coran AY, Patel RP (1997) In Al-Malaika S (ed) Reactive modifier for polymers. Chapman and Hall, London... 

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