Mechanical response of melt-spun amorphous filaments

Abstract

High-speed melt spinning of a cyclo-olefin polymer (COP) and a copolyamide (CoPA) have been performed. Differential scanning calorimetry curves of the resulting monofilaments show that they remain in an amorphous state even after hot drawing. Wide angle x-ray diffraction patterns of undrawn and drawn COP filaments show that although the material remains in an amorphous state, a degree of orientation is induced in the polymer after drawing. The amorphous filaments show an enhanced bending recovery with respect to different semi-crystalline monofilaments commercially available. However, single fiber axial compressive testing indicates that the amorphous filaments exhibit a compressive modulus value which is 50% lower than what is observed for a reference semi-crystalline PET filament. Analysis of the compressive strains applied by the bending recovery test indicates that while the maximum applied strains remain well within the region of elastic deformation of the amorphous materials, the threshold between elastic and plastic deformation is reached for the semi-crystalline materials.

Body-monitoring with photonic textiles: a reflective heartbeat sensor based on polymer optical fibres

“…Fibre ID-1143 shows higher resiliency to bending, reaching 100% within 12 s (figure 1b). From this, we can conclude that fibre ID-1143 is not plastically deformed at a bending radius of 3 mm, comparing to sole COP fibres [20]. Even with an optical cladding, the good resiliency of the COP material is preserved.…”

Spectroscopic elucidation of structure-property relations in filaments melt-spun from amorphous polymers

“…The fiber specimens under Raman analysis were deformed to a radius of curvature of approximately 2 mm, which corresponds to applied compressive (ε c ) and tensile (ε t ) strains at the periphery of the bent fiber in the order of 6% and 1%, respectively. It is known from previous work that ε c = 6% will already induce plastic deformation in the material [5]. Micro-Raman spectroscopy performed by Herrera Ramirez et al [41] on polyamide 66 filaments under axial deformation has shown that the wavenumbers representative of the amorphous domains do not shift when the fiber is subjected to an external load for ε values of up to 12%, a value well beyond the yield point of the material.…”

“…The melt-spun amorphous filaments under analysis display a significantly better recovery from a bending deformation than various semi-crystalline melt-spun fibers commercially available, such as for polyester and polyamide [5]. This is likely possible as the amorphous fibers are able to redistribute applied compressive strains in a way which prevents them from reaching their yield strain criterion at radii of curvature where semi-crystalline materials already undergo plastic deformation [5].…”

“…Table 1 shows the winding speeds for the different specimens under analysis in the present study. It has been shown that the presence of bulky cycloaliphatic substituents attached to the polymer backbone prevents the melt spinning and drawing processes from inducing the molecular order required for the development of fibers having a semi-crystalline structure, and therefore both materials remain in an amorphous state, as indicated by dynamic scanning calorimetry and wide angle X-ray diffraction measurements [5].…”

“…Years later, Bukosek and Prevorsek showed that although the three phase model can be used to describe the microstructure of other fibers such as high tenacity polyamide 6 (PA6), it cannot be employed for instance to explain the morphology of textile PA6 which is produced by standard melt spinning [4]. In recent years, melt spinning and drawing of fully amorphous fibers has been performed in our research group, where the use of X-ray diffraction techniques has confirmed the presence of oriented amorphous domains in the melt-spun fully amorphous filaments, indicating that the degree of orientation is directly proportional to the draw ratio employed during fiber production [5,6].…”