Abstract
The objective of this study was initiated to synthesize a series of phosphonate-containing N-phenylmaleimide((N-phenylmaleimide) phosphate) and bismaleimide((4,4'-Bismaleimidophenyl) phosphate) monomers by a two-step reaction. The fundamental properties of all the maleimide and bismaleimide monomers and derived homopolymers were discussed. The phosphonate-containing monomers with a high reactivity of their unsaturated double bonds were also applied in the copolymerized and blending systems so as to study their basic value in applications.The degree of polymerization in phosphonate-containing maleimide homopolymers should be affected by their side chain. The introduction of phosphonate into side chain of maleimide polymer could reduce their glass transition temperature(Tg) and thermal stability, but increase apparently their char yield of solid residue as an excellent flame retardant. The Tg and thermal stability of the phosphonate-containing maleimide polymers also depended on the substitution pattern of phenyl ring in their side chain. The phosphonate-containing maleimide polymers with the halogen or sulfur atom could combine the flame retarding mechanism of gas-phase and solid-phase to promote their flame retardancy.In the application of MI-styrene copolymer, the variations of Tg with the compositions of MI-styrene copolymers were determined according to the modified Johnston's theory, taking into account to affect the increase of the segments distribution of the comonomers on Tg. The segments distribution of copolymer was homogeneous according to its composition nearby the Fox's theory, which enhanced its synergy effect of the comonomers on thermal stability and flame retardancy. Furthermore, a rigid structure or polar bromine atom within the phosphonate-containing maleimide segment of copolymer also promoted its thermal stability and substantial flame retardancy.The Tg of the curing resins derived from the synthesized phosphonate-containing BMI monomers were around 256℃and with T5% upon 350℃. They showed the better thermal stability than the general phosphides. BMI monomers were also reacted with various aromatic diamines to prepare a series of polyaspartimides successfully. The T5% of all the synthesized polyaspartimides were upon 310℃. Their flame retardancy was depended on the structures and phosphorus contents.In the application of MI-epoxy blends, the mode of thermal reaction of three kind of MI monomers with two different types of epoxy had got a little difference. But, in generally, the Michael addition between MI monomers and DDS was easier with increasing the MI contents. The storage modulus and Tg of the blending systems were reduced due to the MI contents. Although the mechanical strength of blends were decreased with increasing the MI contents, all the blends still maintained a good thermal stability. And, the flame retardancy of blends were promoted significantly with increasing the contents of phosphonate-containing MI monomer.In the application of BMI-epoxy blends, the mode of thermal reaction of two kind of BMI monomers with two different types of epoxy were also similar. The storage modulus and Tg were promoted in the Epon828 system due to the BMI contents. But in the system of phenol-novolac type epoxy, the variance of Tg was not obvious. Although the mechanical strength of blends were decreased with increasing the BMI contents, all the blends still maintained a basic strength. The T5% of all the blends were reduced with increasing the phosphorus contents. The mode of thermal degradation of two kind of BMI monomers with two different types of epoxy were also similar. The PBMI series with a higher phenyl density showed a better thermal stability. The LOI values of blends were promoted significantly with increasing the contents of phosphonate-containing BMI, and the tendency of LOI values was dovetailed to the variance of char yield measured by TGA.