Polypropylene, also known as olefin, is the predominate fiber used in the manufacture of synthetic area rugs in today’s market. Yes there are others such as nylon, and acrylic, but the lions share goes to polypropylene. Polypropylene is a BCF fiber, and is appealing from a cost point of view, as it is relatively inexpensive.
It is a solution-dyed fiber, which means color is added during the extrusion phase while the pre-fiber is still in its molten state. Because of the dying method the selection of colors is limited, on the other hand this dying method yields a fiber that is very colorfast.
Polypropylene cleans very well and most staining isn’t problematic. However, it has poor resiliency, which can lead to crushing. It also has poor abrasion resistance and its low melting point can cause fibers to fuse if furniture or heavy objects are dragged across its surface. As a result polypropylene isn’t the best performer in a commercial, or hospitality application, but if constructed properly, it will provide excellent value and good performance in your home, which is why it holds the largest portion of the area rug market in North America.
Polypropylene rugs are produced on a variety of machine looms, and manufacturers have become very proficient at producing a very nice looking rug. Wool has always been the fiber to copy and many of the polypropylene rugs have a very “wool look” and a “hand” that mimics that of wool.
Synthetic fiber, machine manufactured area rug makers, will often talk in terms of “points per square meter”, which is just as the name implies, the number of fiber points per square meter on the surface pile of the carpet. Generally you will want to have over 500,000 points, and personally I wouldn’t go much over 1,000,000 points. I have seen up to 2,000,000 points/M2, but I feel the whole rug becomes to “stiff” and it loses a natural “hand”, and feels artificial.