Some crystallisation phenomena in rapidly quenched 6.6 nylon

Abstract

In a study of the technology of the melt spinning of 6.6 nylon filaments of diameter in the range 30–100 μ, some new crystallisation phenomena have been noted. Because of the geometrical form of the filaments, cooling from the melt is extremely rapid. Solidification takes place in a fraction of a second, and further cooling to room temperature is also rapid. The polymer can be observed at various stages during its quenching, either by taking samples from the running filaments, or by examining it whilst it is running. Under these conditions, the solid polymer is seen to have a structure not very different from that of the melt. This structure is stable at room temperature for long periods in the absence of moisture. However, on exposure to moisture, diffusion of water into the filament may result in elongation with accompanying changes in the crystalline character. The effects of temperature and moisture concentration on the diffusion process have been studied. X‐Ray diffraction, depolarisation of light and microscopical techniques have been used to examine the crystallisation process in the filament as it is being spun and during the subsequent process of equilibration with water. X‐Ray and optical results show changes of structure to occur on different time scales: the implications of this on the concepts of polymer morphology are discussed. The important röle played by atmospheric moisture in the crystallisation of 6.6 nylon is established, and the likely dependence on water content of second‐order transition data is examined.

Extensional flow behaviour and spinnability of native silk

“…This is an important gap in our knowledge as control of extensional flow fields has been shown to be crucial in successfully designing fibre spinning devices in both polymer and biopolymer-based systems. 16,[29][30][31][32] This was first seen by Chappel and co-workers 33 in 1964 when they were trying to spin Nylon 6.6 and today with a range of groups across the world who are looking at how extensional flow imparts orientation and structure development during melt processing and especially in fibre spinning. [34][35][36][37][38][39] For silk, extensional flow has been hypothesised to provide uniaxial stretching of a liquid silk feedstock, resulting in a stress-induced alignment, denaturation, crystallisation, aggregation and fibrillation to form a solid fibre.…”