Microwave Processing of Functionalized Poly(Arylene Ether Ketones)

Amorphous poly{arylene ether ketones) (PEK) may be designed as either crystalline or amorphous high performance thermoplastics, however, wlth the appropriate terminal functionalities these ductile thermoplastics may also be transformed into tough solvent resistant networks. The functionality presently of interest includes the amine, maleimide and nadimide endgroups. Amine terminated amorphous PEK's were demonstrated in our laboratory to crosslink via ketimine formation at elevated temperatures. This condensation network polymerization involves reaction of the amine endgroups with carbonyl groups along the polymer backbone as demonstrated schematically in Figure l(a). Maleimide functionalized PEK's are believed to crosslink via a free radical mechanism via the reaction of one or more endgroups, as exemplified in Figure l{b). Nadimide terminated PEK's are also thought to undergo a free radical addition polymerization; however, it has been suggested that the mechanism proceeds via a retrograde Diel-Alder reaction generating cyclopentadienc and maleimide endgroups prior to croaslinking as shown in Figure l(c) [ 3,6]. A major drawback to all of these thermosetting systems is the long curing cycles required to develop the optimum mechanical properties.

Electromagnetic (EM) processing (specifically microwave radiation) possesses a number of possible commercial advantages over conventional thermal processing, some of which include; (i) reduction in the time required (or complete cure [7-14]; (ii) reduction in the capital cost of equipment; and (iii) reduced operating costs. There may also be the possibility of producing materials with low residual strenses. Despite the Advantages of this technique, there has been limited commercialization, since there remains no
systematic examination of the critical parameters occurring during EM irradiation which are required for good process control.

The long range goal of this research is to investigate the relationship between the EM and thermal processing conditions and endgroup structure with curing rates for a series of poly(ether ketone) oligomers.