Abstract: Provided are high-performance polyvinyl alcohol fibers having excellent resistances to hot water and dry heat as well as excellent strength and elastic modulus. The fibers are produced from a highly syndiotactic polyvinyl alcohol containing units from vinyl pivalate in an appropriate amount, which renders it possible to draw the highly crystalline fiber in a high drawing ratio of at least 16.

Abstract: Provided are a polyvinyl alcohol fiber having a specific higher order structure, obtained by having the orientation and arrangement of molecular chains forming the fiber which comprises a crystalline region and an amorphous region lie in specific ranges to thereby making the fiber have a break-ing temperature in hot water of at least 125.degree. C., or further at least 130.degree. C. and be excellent in abrasion resistance, while maintaining the tenacity and the modulus of the fiber at high levels; and a process for producing the same.

Abstract: Provided is a high-performance PVA fiber and its production.Each filament of the PVA fiber of the present invention having a structure comprising an aggregate of substantially innumerable fibrils, the fiber has high strength, elastic modulus, and resistances to fatigue, hot water and chemicals and can be pulpified while keeping its excellent features such as high strength. The PVA fiber of the present invention cannot, even drawn to a high ratio, be readily whitened by virtue of its fibril-aggregate structure, and can hence be made still higher in performances. The PVA fiber can be obtained by adding to a PVA solution a relatively large amount of surface active agent, and wet or dry-jet-wet spinning the thus prepared dope solution into an aqueous alkaline coagulating bath.

Abstract: Heat resistant organic fibers comprising a wholly aromatic polymer having amide group and/or imide group, said fibers having properties satisfying the following formulasTm.gtoreq.350.degree. C.,Tm-Tex.gtoreq.30.degree. C.Xc.gtoreq.10%DE.gtoreq.10%DSR(Tm).ltoreq.15%, and ##EQU1## wherein Tm is a melting point; Tex is an exotherm starting temperature; Xc is a degree or crystallization; DE is an elongation; DSR is a dry shrinkage factor at Tm; and DSR(Tm+55.degree. C.) is a dry shrinkage factor at Tm+55.degree. C. The process for producing the fibers is also disclosed.

Abstract: Shaped articles comprised of PVA and PVC having improved flame-retardancy and resistance to discoloration resulting from heat treatment are provided by the incorporation therein of calcined stannic acid, characterized by a specific crystal size.