Nonwovens 　　Polypropylene fiber is the lightest and the most easily to process among all   the synthetic fibers. It can stand for 90 ℃. Acid proof and alkali proof is great. So it generally   used for gas-solid separation and liquid ---solid separation under 100 ℃ and the environment   of strong alkali or strong acid. For liquid-solid separation, polypropylene needle punched felt is   used in frame and plate filter presses, vacuum filters, belt filter presses, and centrifuge filters. It   has stability, high tenacity, and small elongation. Because of its smooth and porous surface   and large air permeability, it has the characters of small vacuum resistance, energy   conservation and easiness for washing. In those industries which need precise filtration and   filtration of tiny particles, such as ore dressing, coal dressing, petroleum industry, and chemical   industry, etc, polypropylene needle punched felt is much more superior than traditional woven   filter fabric. Generally, the felt is made of 2.5D-6D polypropylene staple fiber for surface layer,   and woven fabric of polypropylene thread or HT yarn for scrim. After punching, calendering   and heat setting, the felt is made out. It is used for metallurgy industry, mine industry,   petroleum industry, chemical industry, synthetic fiber production, pharmacy, foodstuff industry,   and liquid-solid separation, etc.