No abstract

No abstract

No abstract

Synthetic fibres with high strength and modulus of elasticity can be fabricated from aromatic polyamides and copolyamides [1][2][3]. The level of these indexes is determined by the chemical structure of the initial polymers, fibre manufacturing technology, and structural and morphological characteristics of their supermolecular organization. Armos fibres manufactured in Russia occupy a special position among the synthetic fibres made from totally aromatic polyamides. For this reason, obtaining data on the structure of such fibres is of theoretical and practical interest.The results of an electron-microscopic study of the structure of Armos fibres are reported. The fibres were wet spun on a laboratory bench from solutions in dimethylacetamide into an aqueous-organic spinning bath. The as-spun fibre underwent the usual operations characteristic of this type of fibre manufacturing process; plasticization drawing, washing, drying, heat treatment, and thermal drawing. The fibre not undergoing the heat treatment and thermal drawing stages will be called the initial fibre below.The initial, heat-treated, and thermally drawn fibres obtained in the different stages were investigated by scanning electron microscopy using a JSM-840 A Jeol (Japan) electron microscope.The electron microscopic photographs of the initial fibre are shown in Fig. 1. Their analysis shows that the fibre diameter is 18-20 lum. The surface of the fibres is furrowed. The furrows run along the axis of the fibre and intersect at acute angles. The furrow width varies from 0.1 to 1 ~tm. At the sites of intersection of the furrows, the fibrils on the surface go out into the inner layers of the fibre, and the fibrils from the inner layers go out on the surface of the fibre. Such surface morphology is characteristic of many fibres wet spun from solutions containing 5-10% polymer and is due to the characteristics of solidification of the liquid jet of spinning solution when it falls into the spinning bath and subsequent plasticization drawing. In all probability, the sites of intersection of the furrows are unusual stress concentrators. Due to this, cracks and defects on the surface of the fibre appear with large loads primarily at sites of intersection of the furrows. This can be hypothetically judged by the photomicrographs shown in Fig. 2.It shouid also be noted that a relatively large number of defects, broken macro-and microfibrils, is observed oll the surface of the initial fibre. These defects are clearly visible in the photomicrographs of the surface of the initial fibre shown in Fig. 3.The character of the surface morphology and fibre diameter change very little after heat treatment and them~al drawing. This is indicated by the photomicrographs of the surface of heat-treated and thermally drawn fibres (Fig. 4). The structural morphology formed in the initial fibre on the level of micro-and macrofibrils is preserved without visible changes, while the fundamental changes in these treatments probably take place in the fine structure, phase state, and in...

No abstract