Polyester felts offer very good resistance to chemicals, abrasion and dry heat degradation. They offer excellent dimensional stability and are the most common type of filter bag used today. Polyester are good for dry heat applications and are superior to other synthetics with the exception of Nomex (Aramid) and Teflon in this regard. Polyester is not a good choice for moist heat and subject to hydrolytic degradation under certain circumstances. Polyester offers good resistance to most mineral and organic acids except high concentration of nitric, surfuric and carbolic acids. It has good resistance to weak alkalis and moderate resistance to strong alkalis at low temperature. Polyester also has good resistance to most oxidizing agents and excellent to most organic solvents. It is not recommended for some phenolic compounds. Not recommended for high concentration of strong alkalis at high temperatures.