No abstract

Thirteen aliphatic and aromatic polyhydrazides have been converted as bulk polymer by a unique polymer by a unique polymer post reaction into high molecular weight poly(1,3,4‐oxadiazoles). This reaction proceeds by thermal cyclodehydration at 170–280°C. with elimination of water. The resulting poly(1,3,4‐oxadiazoles) have been characterized by microanalysis, inherent viscosity, x‐ray diffraction patterns, and by infrared and ultraviolet absorption spectra. Films could be pressed from the melt of polyoxadiazoles melting below 350°C., while very high melting or infusible aromatic polyoxadiazoles could not be manufactures into films and fibers by conventional means. Such polymers are extremely thermally and oxidatively stable and decompose between 450 and 500°C.

The liquidus temperature plays an important role in the manufacture of fiberglass and glass melts and in the design of new energy‐saving commercial compositions, which must be formulated to be crystallization resistant, possess a lower operating temperature and require less energy than incumbent commercial compositions. In the manufacture of glass melts and glasses, the temperature at the furnace exit must be above the liquidus temperature to avoid crystallization and many operations beyond the furnace exit are carried out below the liquidus temperature. This paper establishes the relationship between liquidus temperature and operating temperatures in various process steps and analyzes the parameters, which are required for the manufacture of new and more energy‐saving variants.

A polyoxidiazole fiber, alt. poly[1,3‐/1,4‐phenylene‐2,5‐(1,3,4‐oxadiazole)], with excellent thermal stability was prepared from poly(isophthalic‐terephthalic hydrazide) fiber by thermal cyclodehydration. Conversion of this polyhydrazide fiber proceeded at 280°C. in a muffle furance under positive nitrogen pressure and was completed in 48–72 hr., as evidenced by elemental analyses. The resulting polyoxadiazole fiber had the following typical fiber properties: T/E/Mi/den. = 2.6/3.1/124/3.1. It was thermally stable when exposed for prolonged periods of time at temperatures of 400°C. During heat treatment between 300 and 400°C. the initial polyoxadiazole fiber undergoes a structural change and final properties were: T/E/Mi/den. ∼ 1.5/1.5/90/3.0. The polyoxadiazole structure was found to degrade severely at 450°C.