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In this, the first of a series of five papers, the historical development of formaldehyde polymers, beginning with the work of Butlerov and continuing through the investigations of Staudinger and his collaborators, is reviewed. Recent studies in these laboratories have led to thermally stable high polymers of formaldehyde. Initiators and the role of impurities in the polymerization are described. An explanation is offered to account for differences in thermal stabilities between old and new polymers. Esterification, by which further increases in thermal stability are achieved, is described. It is proposed that the generic term “acetal resin” be used to described high polymers that are composed of repeating oxymethylene units.

Copolymers of ethylene and propylene in which none of the propylene units are reversed have low levels of crystallinity over the entire range of composition. Molecular mechanics calculations indicated that the polyethylene-type planar-zigzag conformation and the polypropylene-type helical conformation would have similar energies in copolymers containing 33-55 mol % ethylene. Measurements by X-ray diffraction and differential scanning calorimetry showed that samples in this range contained both kinds of crystals. When a copolymer of propylene with 36 mol % ethylene was incorporated in a blend of isotactic polypropylene and low-density polyethylene, the polyethylene phase was more finely dispersed, and the interfacial adhesion and notched Izod impact strength were improved. These effects were attributed to the ability of the copolymer to cocrystallize with both homopolymers.

A series of polyamides was prepared by interfacial polymerization of diamines with 1,2,5‐thiadiazole‐3,4‐dicarbonyl chloride. Polyamides from secondary cycloaliphatic diamines and aromatic diamines have high softening points, high glass transition temperatures, and good thermal stability. Secondary amines, in particular cycloaliphatic secondary amines, form very high molecular weight polyamides. The polyamide from trans‐2,5‐dimethylpiperazine and 1,2,5‐thiadiazole‐3,4‐dicarbonyl chloride is soluble in chloroform and 1,1,2‐trichloroethane and has been cast into films and spun into fibers from those solvents. Fibers of this polymer are strong and have very high work recovery from small strains. In addition, these fibers show good retention of strength and work recovery over a range of temperatures and humidities.