Melting-point temperature aromatics

The melting points of a large number of polymers have been determined and are shown in Table 2. Aliphatic polyanhydrides generally melt at lower temperatures than do aromatic polyanhydrides. The melting point of aromatic-aliphatic copolymers is proportional to the aromatic content in the copolymer. Introduction of fatty acids in copolymers also lowers the melting point of the bulk polymer. 

Despite their high melting point, semi-aromatic, semi-crystalline polyamides cannot be equated with high-temperature thermoplastics in terms of continuous operating temperature. The resistance of non-stabilized grades to thermal-oxidative... 

The rigid rod structures and high melting points of aromatic polyesters make it dfficult to dissolve these polymers at lower temperatures in concentrations of more than a few per cent. Some of the solvents and solvent combinations which have been used for this purpose are listed in Table 4 with a qualitative indication of their solvent ability. Most of these... 

TABLE 2.8 Melting Point, Tm (°C), and Glass Transition Temperature, 7 (°C), of Aliphatic, Aromatic-Aliphatic, and Cycloaliphatic Polyesters... 

Fatty acids have also been converted to difunctional monomers for polyanhydride synthesis by dimerizing the unsaturated erucic or oleic acid to form branched monomers. These monomers are collectively referred to as fatty acid dimers and the polymers are referred to as poly(fatty acid dimer) (PFAD). PFAD (erucic acid dimer) was synthesized by Domb and Maniar (1993) via melt polycondensation and was a liquid at room temperature. Desiring to increase the hydrophobicity of aliphatic polyanhydrides such as PSA without adding aromaticity to the monomers (and thereby increasing the melting point), Teomim and Domb (1999) and Krasko et al. (2002) have synthesized fatty acid terminated PSA. Octanoic, lauric, myristic, stearic, ricinoleic, oleic, linoleic, and lithocholic acid acetate anhydrides were added to the melt polycondensation reactions to obtain the desired terminations. As desired, a dramatic reduction in the erosion rate was obtained (Krasko et al., 2002 Teomim and Domb, 1999). 

The R group between the diamine or diol functionality can be widely varied to include straight chain and branched alkyl groups as well as additional functionality such as either olefin or acetylenic groups. R can also be an aromatic group which may or may not contain additional functionality. In general, all of the monomers are crystalline solids with melting points lower than 200 °C which is the minimal temperature required for the onset of efficient homopolymerization. 

At a temperature below the melting point nitroguanidine is said to be relatively stable—more so than nitric esters and similar in stability to aromatic nitro compounds. 

---