Polypropylene is a relatively low temperature fibre with excellent chemical resistance which makes it a perfect use in specialist applications like the chemical industry. The PP needlefelt is widely used in liquid-solid filtration. Besides some properties as ordinary filter felt have, the properties of anti-acid, anti-alkali and lower soften point of PP are better than polyester, and its stability of water solution is excellent. The fibre is of low density (it floats in water) and so a given denier of the fibre is much larger in diameter than the polyester equivalent. This makes the felt being quite thick, nearly 50% thicker than for the same polyester weight.
The fibres cannot hydrolyse, the only chemical weakness being a susceptibility to oxidising agents. Apart from that they can be used almost universally provided the temperature is below 90 °C. Few other benefits are it has a smooth surface, more defined pore size and good air permeability (under 90 °C).