Heat resistance of polymers

Synthesis and characterization of fully rodlike poly(4,4?-biphenylene pyromellitimide)s with various short side groups

“…Packing coefficients (Ks) of films were estimated from the measured densities using the following equation proposed by Slonimskii et al 26 : Figure 5. Chemical structures of fully rodlike poly(4,4Ј-biphenylene pyromellitimide)s with various short side groups.…”

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] In particular, aromatic polyimides have found diverse applications in the microelectronics industry as flexible circuitry carriers, stress buffers, interdielectric layers, and passivation layers because of their good electrical and mechanical properties, high thermal stability, high chemical resistance, and high dimensional stability. [22][23][24][25] In general, for aromatic polyimides without side groups, a higher molecular packing coefficient 26 provides a higher mechanical modulus and a low thermal expansion coefficient. 8,[27][28][29] For this sense, fully rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA) and poly(4,4-biphenylene pyromellitimide) (PMDA-BZ) are so attractive to both industry and academia because they can potentially provide a high modulus and a low thermal expansion coefficient in addition to a high dimensional stability.…”

Concepts of Trapping Topologically by Shell Molecules

“…The CH group takes a volume of 10.9 A J in the hydrocarbon molecule (25], In Table 1 are results of calculations describing the perfect cascade branched polymer constructed from CII units, depending on the polymerization degree m of a branch of. the molecule.…”

Bimodal character of polyester–solvent interactions. I. Evaluation of the solubility parameters of the aromatic and the aliphatic ester residues of poly(ethylene terephthalate)

“…The value of R as given by expression (24) assumes the validity of the geometric mean additivity rule and is consistent with the definition of 6 as given by expression (15). The incorporation of the factor 2 by Hansen is not needed to make the polymer-solvent interaction domain spherical in shape.…”

“…The spread in the values of 6d for most solvents is small compared to that of 6, and &-hence giving the observed "apparent" nonspherical representation of the data. Presumably, if solvents could be found (and had been used) with 6d values smaller and larger than those used by Hansen, then the resultant polymer-solvent interaction domain would approach that of a sphere as defined by expressions (15) and (24). bringing about volume swelling, longitudinal shrinkage, and crystallization of the polyester structure.…”