THE ROLE OF MACROMOLECULAR ENTANGLEMENTS IN THE GEL SPINNING PROCESS AND PROPERTIES OF HIGH-PERFORMANCE POLYACRYLONITRILE FIBERS

The mode of macromolecular entanglements may be varied and complicated . In most cases, the entanglement is generally just a looping between two molecular chains. In the formation process of ultrahigh-molecular- weight acrylic fibers by gel spinning, the influence of entanglements is present everywhere. The ultrahigh-molecular-weight polymer was born entangled; the chains may even form networks. To facilitate formation , the entanglements in the concentrated polymer solution must be prope rly controlled. The network structure may endow elasticity to the syst em, which is responsible for such peculiar rheological properties as d ie swell, Weissenberg effect, melt or solution fracture, etc. Part of the entanglements remaining in the finished fiber texture may affect t he mechanical properties of the fiber, such as loop strength, tensile stress-strain properties, etc. The results given in this pertain partl y to ordinary high molecular weight and partly to ultrahigh-molecular- weight polyacrylonitrile.