Abstract: A polyethylene cap, for use with containers, particularly polypropylene containers for containing medical specimens in preservative fluid such as formaldehyde, is provided with a 3-face seal, wherein a rim portion of the container is trapped in sealing, contacting relation on three mutually adjoining faces, whereby any tendency of the container rim to "relax" out of sealing engagement with a contacting face portion of the cap is effectively precluded by the fit and the geometry of the cap seal. In the case of polypropylene, which is susceptible to such "relaxation", the subject cap enables the effective sealing of polypropylene containers so that advantage may be taken of the superior properties of polypropylene in non-reactive, secure containment of possibly contaminated medical specimens in liquids such as formaldehyde, a known carcinogen.

Abstract: A biological sample collection tube suitable for use in collecting and processing blood samples, is of high strength, transparent plastic. The tube wall is substantially gas impermeable, permitting the retention of samples therein, under conditions of vacuum, for prolonged periods. The selected material is combustible in air, yielding products of combustion that are substantially non-toxic, to facilitate the safe disposal of the tubes, together with the enclosed samples. The tube is made of plastic copolymer or monomer resin such as polyethylene, polypropylene or polyamide. A preferred material group is amorphous nylon, in particular Nylon 6 (T.M.) such as polyethylenenaphthalate and ethylene vinyl alcohol. The tube may be made from a combination of such materials by mechanical integration in manufacture, through co-extrusion, co-injection, or by a dual material indexed molding process.