Frequently Asked Questions

International Copyright 1987 © M-Cor Inc, All Rights Reserved

WHAT IS ENCAP-O-SEAL®?
ENCAP-O-SEAL® is the trade name of M-COR, Inc.’s Teflon® encapsulated o-ring.

WHAT IS A TEFLON® ENCAPSULATED O-RING?
A Teflon® encapsulated o-ring is a universal chemical resistant seal used in industry to prevent passage of corrosive fluids or gases. It is made of two components: (1) A Teflon® encapsulation (i.e. jacket or covering), and (2) an elastomer (i.e. rubber) core material, which is completely enclosed within the encapsulation.

WHAT IS AN ELASTOMER?
An elastomer is a general term for elastic, rubber-like substances.

WHAT IS THE REASON FOR ENCAPSULATING A RUBBER CORE MATERIAL WITH TEFLON®?
First, the Teflon® encapsulation, which is virtually chemically inert, enables the o-ring to resist practically all chemicals (thereby extending seal life, preventing contamination, etc.). Second, the elastomer core material imparts its mechanical properties to the o-ring. Thus, unlike solid TFE o-rings, Teflon® encapsulated o-rings resist cold flow. The synergism of these components gives the Teflon® encapsulated o-ring its unique properties: it is chemically resistant and anti-stick as well as resilient and resistant to cold flow.

WHAT TYPES OF TEFLON® ARE USED TO ENCAPSULATE THE RUBBER CORE MATERIAL?
M-COR, INC. uses only the highest quality certified virgin Teflon® resins: FEP 160, PFA 350.

WHAT IS TEFLON® FEP 160?
Teflon® FEP 160 fluorocarbon resin is a melt processible copolymer of Tetrafluoroethylene and Hexafluoropropylene. Teflon® FEP 160 is practically chemically inert, having an operating temperature of 2050C/ 4000F and has the highest molecular weight of the FEP family of resins. It is Teflon® FEP 160 that is responsible for our products’ ability to withstand chemical attack at elevated temperatures. Teflon® FEP resins were invented by DuPont and first became commercially available in 1960. Engineers specify Teflon® FEP 160 encapsulation when corrosive resistant seals with operating temperatures of up to 205oC/ 400oF are required for industrial sealing applications.

WHAT IS TEFLON® PFA 350?
Teflon® PFA 350 Fluorocarbon resin is a melt processible copolymer of Tetrafluoroethylene and Perfluorinated vinyl ether from the Perfluoroalkoxy group. Teflon® PFA 350 is practically chemically inert, having an operating temperature of 2600C/ 5000F and has one of the highest molecular weights of the PFA family of resins. M-COR, INC. utilizes PFA type 350 upon request in the manufacture of ENCAP-O-SEALTM Teflon® encapsulated O-rings. Teflon® PFA 350 is responsible for our products’ ability to withstand chemical attack at elevated temperatures. Teflon® PFA was invented by DuPont and became commercially available in the 1970’s. Engineers specify Teflon® PFA 350 encapsulation in corrosive sealing applications that exceed operating temperatures of 205oC/ 400oF and up to 260oC/ 500oF.

WHAT TYPES OF ELASTOMER (RUBBER) CORE MATERIAL ARE USED IN M-COR’S TEFLON® ENCAPSULATED O-RING?
The primary elastomers we use are specially formulated, high temperature FDA compliant, USP Class VI Compliant solid core and hollow core Dow Corning® silicone, or a DuPont Performance Elastomer Type A solid core or hollow core Viton®. EPDM is available upon request.

WHAT ARE THE ADVANTAGES OF USING A VITON® ENCAPSULATED O-RING RATHER THAN SILICONE ENCAPSULATED O-RING?
If the application has a wide temperature range in diverse chemical service, a Viton® core is likely the better choice. Due to the effects of chemical permeation, the core material may be compromised in some cases. Viton® has a greater range of chemical compatibility than silicone core and therefore may extend seal life. *See Gas Permeability.

WHAT IS A HOLLOW CORE O-RING AND WHY IS IT USED?
ENCAP-O-SEAL® hollow core o-rings are manufactured using two components: (1) a Teflon® encapsulation (i.e. jacket or covering) and (2) an elastomer (rubber) hollow core material, which is completely enclosed within the Teflon® encapsulation. M-COR, INC. encapsulates hollow-core o-rings to create a softer durometer seal. When the durometer is decreased, the amount of clamping force needed to effect a seal is reduced. The durometer of our standard hollow core ENCAP-O-SEAL® o-ring is decreased approximately 10%. M-COR, INC. can design special core configurations to meet durometer requirements. Engineers specify ENCAP-O-SEAL® hollow core o-rings in applications where clamping force is minimized due to other mechanical design considerations. Example applications would be ID/OD static or dynamic cylinder o-ring glands, hand tightened lids, caps, etc.

WHAT IS DUROMETER?
Durometer is a numerical scale for measuring the hardness of rubber.

WHAT ARE THE DUROMETERS OF ENCAP-O-SEAL® O-RINGS?
ENCAP-O-SEAL® solid silicone core = 85-90 Shore A.
ENCAP-O-SEAL® solid Viton® core = 90-95 Shore A.
ENCAP-O-SEAL® hollow core silicone = 70-80 Shore A.

WHAT IS THE HARDNESS SHORE A?
The Hardness shore A is the durometer reading in degrees of the hardness of the rubber. (Shore A hardness of 35 is soft; 90 is hard.)

DO TEFLON® ENCAPSULATED O-RINGS MEET AS568 STANDARDS?
All Teflon® encapsulated o-rings are manufactured to meet AS 568 standards as closely as possible. However, it must be noted that Teflon® encapsulated o-rings have a greater cross sectional and inside diameter tolerance range than AS 568 standards dictate. Teflon® encapsulated o-rings are not necessarily molded products; thus, all inside diameter tolerances conform to those for straight-length, unspliced extrusions. M-COR, INC. adheres to the highest precision standards published in the RMA HANDBOOK (Rubber Manufacturers Association).

WHAT QUALITY CONTROL STANDARDS OR INSPECTION CRITERIA DO YOU USE?
Due to the critical sealing applications in which ENCAP-O-SEAL Teflon® encapsulated o-rings are used, strict quality control standards must be met. First, cross sectional and inside diameter dimensions must meet the criteria set forth in the Tolerance Chart section of our Quality Manual. Using the RMA handbook, an o-ring inspection guide for surface imperfections control, M-COR, INC. has published a quality control manual to establish quantitative levels of acceptance for ENCAP-O-SEAL® Teflon® encapsulated o-rings relative to imperfection type, size and quantity (* See Quality Assurance).

WHAT IS THE RMA HANDBOOK?
The RMA Handbook was researched and published by the Technical Committee of the Rubber Manufacturers Association. It describes visual quality acceptance criteria for O-rings. The Rubber Manufacturers Association is a cooperative manufacturing trade association.

WHAT IS COLD FLOW?
Cold flow denotes continued deformation under stress.

WHAT IS COMPRESSION SET?
Compression set is the decrease in thickness of a rubber specimen, which has been deformed under specific conditions of load, time and temperature.

WHAT IS A COPOLYMER?
Copolymer is a polymer consisting of two different monomers chemically combined.

WHAT IS A CROSS-SECTION?
A cross-section is an o-ring as viewed if cut at right angles to the axis.

WHAT IS A CURING DATE?
The cure date denotes when the manufacturing process is complete and the o-ring is ready for shipment.

WHAT IS A STATIC APPLICATION?
A static application is a stationary application.

WHAT IS A STATIC SEAL?
A static seal is a seal designed to work between parts having no relative motion.

WHAT IS A DYNAMIC APPLICATION?
A dynamic application is an application in which the o-ring is subject to movement or moving parts.

WHAT IS A DYNAMIC SEAL?
A dynamic seal is a seal that is required to prevent leakage past parts that are in relative motion.

WHAT IS EXTRUSION?
Extrusion denotes distortion under pressure that forces the seal into the clearance between mating metal parts.

WHAT IS A GLAND?
A Gland is a seal assembly groove, which includes the o-ring, the groove and the mating/sealing surfaces.

WHAT IS HOMOGENEOUS?
A homogeneous material is of uniform composition throughout.

WHAT IS PERMANENT SET?
The permanent set is the deformation remaining after a specimen has been stressed in tension a prescribed amount for a definite period, and released for a definite period.

WHAT IS PERMEABILITY?
Permeability is the property of rubber, plastic or other materials that permits passage of gas through the molecular structure of the material.

WHAT IS A POLYMER?
A polymer is a material formed by the joining together of many (poly) individual units (mer) of a monomer.

WHAT IS RESILIENCE?
Resilience refers to the ability to return to an original size and shape after deformation.

WHAT IS RMS?
The RMS is the Root Mean Square: The measure of surface roughness, obtained as the square root of the sum of the squares of micro-inch deviation from true flat.

WHAT IS THE ACTUAL SIZE?
The actual size is the actual dimensions of the o-ring, including tolerance limits.

WHAT IS THE NOMINAL SIZE?
The nominal size is the approximate size of the o-ring in fractional dimensions.

WHAT IS SPECIFIC GRAVITY?
Specific gravity is the ratio of the weight of a given substance to the weight of an equal volume of water at a specified temperature.

WHAT IS SQUEEZE?
Squeeze is the cross-section diameter compression of an o-ring between the bottom surface of the groove and the surface of other mating metal parts in the gland assembly.

WHAT IS STRESS?
Stress is the force per unit of original cross-sectional area required to stretch a specimen to stated elongation.

WHAT IS O-RING SWELL?
The swell is the increased volume of an o-ring caused by immersion in fluids.

WHAT IS TENSILE STRENGTH?
Tensile strength is the force in pounds per square inch required to cause the rupture of a specimen of a rubber material