The effect of reprocessing of polypropylene on fiber spinning

Because of the environmental considerations, recycling is becoming a very important factor in any production planning within the fiber industry and textile industrial sectors. One of the determining factors for recycling of fibrous assemblies into fiber is the spinnability of the incoming material. The hypothesis underlying the present work is that by carrying out rheological analysis of the polymer melt it should be possible to predict the state and level of degradation of the polymeric fibrous waste material—hence its spinnability. Our experimental studies show that a melt spinning grade polypropylene could be recycled five times without significant decreases in fiber properties. Afterward, the fiber production failed in the cold-drawing step before melt rupture occurred in the draw-down step. Rheological analysis of the melt in long-term stability experiments showed that unspinnable melts show an abrupt change in loss factor at a certain level of loss and storage modulus. The reasons for this behavior are associated to changes in molecular weight, viscosity, and melt strength. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1859–1867, 1999