High strength porous polytetrafluoroethylene product having a coarse microstructure
OwnerJeffery B. Bowmaninventor
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Abstract
Porous polytetrafluoroethylene materials having high strength and coarse microstructure are produced by densifying the materials after removal of lubricant and then stretching. The term, "coarse," is used to indicate that the nodes are larger, the fibrils are longer, and the effective pore size is larger than conventional materials of the same matrix tensile strength. Densification can be achieved through the use of such devices as a densification die, a calender machine, or a press. This invention can be used to produce all kinds of shaped articles.
Claims23
A porous material consisting essentially of polytetrafluroroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and as measured along at least one direction, has a combination of average matrix tensile strength greater than about 15,000 psi and an average node height/width ratio greater than about 3.
A porous material consisting essentially of polytetrafluoroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and as measured along at least one direction, has a combination of average matrix tensile strength greater than about 40,000 psi and an average node height/width ratio greater than about 3.
A porous material consisting essentially of polytetrafluoroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and as measured along at least one direction, has a combination of average matrix tensile strength greater than about 15,000 psi and an average node height/width ratio greater than about 5.
A porous material consisting essentially of polytetrafluoroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and as measured along at least one direction, has a combination of average matrix tensile strength greater than about 40,000 psi and an average node height/width ratio greater than about 5.
A porous material consisting essentially of polytetrafluoroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and as measured along at least one direction, has a combination of average matrix tensile strength of about 49,000 psi, average fibril length of about 120 microns, and an average node height/width ratio of about 6.
A porous material consisting essentially of polytetrafluoroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and as measured along at least one direction, has a combination of average matrix tensile strength of about 55,000 psi, average fibril length of about 74 microns, and an average node height/width ratio of about 7.
A porous material consisting essentially of polytetrafluoroethylene polymer, which material is characterized by nodes interconnected by fibrils, said material having a matrix tensile strength greater than or equal to about 3,000 psi and less than or equal to about 25,000 psi and which has a corresponding coarseness index greater than or equal to the value on a line connecting the points A, B, C, and D in FIG. 3 and defined in the following table:
- ______________________________________ MATRIX TENSILE STRENGTH COARSENESS INDEX psi (gm/cc)/psi ______________________________________ A 3,000 0.40 B 12,000 0.40 C 16,000 0.20 D 25,000 0.20 ______________________________________
A porous material consisting essentially of polytetrafluoroethylene polymer, which material has a microstructure characterized by nodes interconnected by fibrils and has an ethanol bubble point of less than or equal to about 4.0, wherein said fibrils include first fibrils oriented substantially perpendicular to second fibrils, and wherein the ratio of the matrix tensile strength as measured along the first fibril direction to the matrix tensile strength measured along the second fibril direction is between about 0.4 and 2.5, and the matrix tensile strength in the weaker direction is greater than or equal to about 3000 psi.
Dependencies are inferred from the claim text.