Diallyl isophthalate, polymerization

The most extensive research and development activity has involved diallyl o-phthalate. The studies on the cyclopolymerization of this monomer have already been discussed at length in Section 3 of this chapter. Diallyl isophthalate polymerizes more rapidly than the the ortAo-isomer. It cyclizes less during the early stages of polymerization. Consequently the prepolymer of the isophthalate has more reactive double bonds available for further reaction than the o-phthalate and the final resin produced from it is more highly cross-linked [91]. 

Diallyl Isophthalate. DAIP polymerizes faster than DAP, undergoes less cyclization, and yields cured polymers of better heat resistance, eg, up to ca 200°C. Prepolymer molding materials such as Dapon M of EMC, are not sticky. Maleic anhydride accelerates polymerization, whereas vinyl isobutyl ether retards it and delays gelation in castings. Copolymers with maleic anhydride are exceptionally hard and tough and may scratch homopolymer surfaces. 

Studies of the pre-gel stage of free radical polymerizing diallyl isophthalate as well as of diallyl sebacate have been shown to involve significant intramolecular cyclization. On the average six to eight monomer units appear to be involved in each cycle [112, 113]. 

Radical branching polymerization of diallyl isophthalate in bulk and in benzene solutions [132]. 

After removal of water and cooling, the fluid polyester may be dissolved in a reactive monomer in the same kettle, or it may be shipped to users who add the monomer and catalyst in their plants. Styrene is most widely used as the reactive monomer. Others sometimes used as diallyl phthalate, diallyl isophthalate, and triallyl cyanurate. A peroxide catalyst is generally used for the final co-polymerization. These unsaturated polyesters are thermosetting and are most widely used in reinforced plastics for making boat hulls, trays containers, and panels, and in potting of electrical assemblies. 

On heating with a peroxide, DAP therefore polymerizes and eventually cross-links, forming an insoluble network polymer. However, it is possible to heat the DAP monomer under carefully controlled conditions, to give a soluble and stable partial polymer in the form of a white powder. The powder may then be blended with peroxide catalysts, fillers, and other ingredients to form a molding powder in the same manner as polyester alkyds. Similar products can be obtained fi-om diallyl isophthalate (DAIP). 

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