Twisted polypropylene rope the least expensive synthetic.
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It compares pretty well vs other popular synthetics. It is two to three times stronger than manila, but not as strong as nylon. It has lower stretch than nylon, but not as low as polyester. It is more abrasion resistant than manila, but less than nylon or polyester. It is resistant to rot and mildew and most chemicals, can be stored wet, and it floats. And it's available in a number of colors, the most common being yellow. Other popular colors are white - often used for rental tent rope, blue and white for swimming pool lane rope, and tan, for a manila-like appearance.
The big downside is that polypro does not hold up well to extended exposure to sunlight compared to manila rope or to other popular synthetics. This makes twisted poly a poor choice for long term use outdoors, especially in load bearing applications.
Utility contractors use twisted poly rope for pulling cable (or heavy pull ropes) through conduit - its slippery surface is a plus here, as a short term visual barrier, and for general tie down use. Because it is not absorbant, polypro is especially useful in pulling applications where there is a possibility water may be present.