Influence of melt spinning variables on the tensile properties of high density polyethylene fibers

The tenacity and stiffness modulus of yarns melt‐spun from high density polyethylene are functions of the sum of the logarithm of the take‐up velocity in melt drawing and the true (logarithmic) deformation imparted in the cold‐drawing process (i.e., stretching at a temperature below the polymer melting temperature). Thus, for the conditions investigated the effective melt drawing deformation is independent of the calculated velocity of the melt in the spinneret orifices. The maximum cold draw ratio is shown to be a function of the production rate, increasing to a maximum value and then decreasing as the production rate is increased. The maximum cold draw ratio at a given production rate is found to be a function of the yarn temperature and the deformation introduced in melt drawing. The tenacity and stiffness modulus of yarns melt‐spun from polypropylene may also be expressed as functions of the summation of the logarithm of the take‐up velocity of melt drawing and the true deformation imparted in cold drawing. The orientation, as measured by birefringence, of yarns spun from an experimental polyester are a function of the ratio of the take‐up velocity and the orifice velocity, wheras the same measurement of the orientation of polyethylene is a function of the extrusion velocity alone. Equations of state for the tenacity and stiffness modulus of melt‐spun polyethylene yarns were found to be of the same form as for a wet‐spun madacrylic fiber.