Polypropylene copolymers have outstanding chemical resistance and show the highest resistance of all thermoplastics to organic chemicals. High density polypropylene has some similarity with Polypropylene co-polymers in respect of chemicals resistance, although here again Polypropylene co-polymers possesses the additional advantages of being usable at higher operating temperature. Both the polymers have similar solubility parameters and tend to swell by the same solvents. In both the cases the absence of any possible interaction between the crystalline polymer and the liquid prevents solution of the polymers in any liquid at room temperature. Polypropylene copolymers also possess an extremely high resistance to inorganic environments. It is not attacked by aqueous solution of inorganic salts not by most mineral acids and bases, even when in concentrated form, though it is liable to be attacked by oxidising agents e.g. 100% fuming Nitric acid and Sulphuric acid or the halogens.