Abstract: Improvements in preventing heat- and moisture-shrink problems in specific polypropylene tape fibers are provided. Such fibers are basically manufactured through the initial production of polypropylene films or tubes which are then slit into very thin, though flat (and having very high cross sectional aspect ratios) tape fibers thereafter. Such fibers (and thus the initial films and/or tubes) require the presence of certain compounds that quickly and effectively provide rigidity to the target polypropylene tape fiber after heat-setting. Generally, these compounds include any structure that nucleates polymer crystals within the target polypropylene after exposure to sufficient heat to melt the initial pelletized polymer and upon allowing such a melt to cool. The compounds must nucleate polymer crystals at a higher temperature than the target polypropylene without the nucleating agent during cooling.