No abstract

Hydrolytically stable phosphorus-containing monomers, such as 4,4'-bis(fluoro-pheny1)methylphosphine oxide (BFPMPO), 4,4'-bis(hydroxyphe1nyl)methylphosphine oxide (BOHPMPO), and 4,4-bis(hydroxyphenyl)phenylpliosphine oxide (BOHPPO), were synthesized and used in nucleophilic aromatic Substitution polycondensation to prepare poly(ary1ene ether phosphine oxide) engineering thermoplastics. The synthesis and characterization of these novel polymers are described. It was determined that by incorporating the phosphine oxide moiety into the polymer backbone, certain properties of the resulting poly(ary1ene ether) were substantially improved, such as an increase in Tg, thermal stability in air, modulus, and char yield compared with control poly(ary1ene ether su1fone)s. The :high char yields obtained for these polymers in air along with observed intumescence indicates that these materials have improved fire resistance. Preliminary cone calorimetry measurements support this conclusion.

In order to obtain materials for improved printed circuit boards (PCBs) with high thermal conductivity and low dielectric losses, hexagonal boron nitride (h-BN) was incorporated into a polytetrafluoroethylene (PTFE) matrix. The filler loading in the composite was varied up to a filler volume content of 50%. Thermal conductivity and coefficient of thermal expansion (CTE) were investigated with respect to filler orientation. Further dielectric and mechanical properties were investigated. The incorporation of h-BN improved the heat transport significantly, while the loss factor decreased. Fillers with a higher aspect ratio have a greater effect on increasing thermal conductivity. For a filler volume loading of 30%, the in-plane thermal conductivity was up to 14 times higher than the thermal conductivity of the matrix, while the loss factor decreased slightly. The permittivity increased with the increasing filler volume content, while the CTE also decreased. Though the filler affects the mechanical properties negatively, 40% of the tensile strength could be maintained if a filler volume content of 30% is not exceeded. Such compositions may be used as raw materials for future printed circuit boards.

The physical aging properties of amorphous thermoplastics having various terminal groups were investigated with creep recovery and linear dilatometry. The structure of the chain end groups affected physical aging at lower molecular weights; however, above the critical molecular weight for entanglements the end‐group effect on aging diminished. Experimental densities and glass‐transition temperatures were also end‐group dependent. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2850–2860, 2003