Materials of Construction

Materials of Construction

This module outlines the features, advantages, and disadvantages of the most commonly used materials found in the most sealing devices, whether they be gaskets, packing, expansion joints, or hydraulic components. It is important to know the properties of the individual constituents in order to have a better understanding of the features and benefits of the final sealing device.

Jump to a Section

  1. Basic Elastomers and Rubber

  2. Fibers 

  3. Other Common Materials

  4. Metals & Alloys

  5. Fillers

  6. Conclusion and Test

Basic Elastomers & Rubbers 

Rubber has three predominant characteristics:

  • Incompressible – Can be deformed but not reduced in volume
  • Extensible – Can be stretched
  • Impermeable – Can prevent the passage of gases through the material

 

Most Common Elastomers & Rubbers used in Fluid Sealing Components

Ethylene Propylene

Ethylene Propylene-Diene Terpolymer (EPDM) or Ethylene-Propylene Copolymer (EPM)

  • Resistant to animal and vegetable oils, strong and oxidizing chemicals and ozone
  • Attacked by petroleum oils and solvents, and aromatic hydrocarbons (I.E. toluene, benzene, xylene, etc.)
  • Excellent weathering properties, low temperature resistance, low permeability to air, and good dielectric strength
  • Good bonding properties (Expansion Joints)
  • Temperature limit: 300°F (149°C)

Fluoroelastomer

Hexafluoropropylene-Vinylidene Fluoride (FKM or FPM)

  • Most common trade names: DuPont VITON® and 3M FLUOREL®
  • Resistant to aliphatic, aromatic, and halogenated hydrocarbons, acids, animal and vegetable oils
  • Attacked by ketones, low molecular weight esters, and nitro-containing compounds
  • Good weathering properties and resistance to elevated temperatures
  • Available in several types and grades
  • Temperature limit: 400°F (205°C)

Neoprene

Chloroprene (CR)

  • Resistant to moderate chemicals, acids, oils, fats, grease, many solvents, and ozone
  • Attacked by strong oxidizing acids; esters; ketones; chlorinated, aromatic, and nitro hydrocarbons
  • Good weathering resistance
  • Flame retarding

Natural Rubber

Isoprene

  • Generally resistant to most moderate wet or dry chemicals, organic acids, and alcohols
  • Attacked by strong acids, fats, oils, grease, most hydrocarbons, and ozone
  • Excellent physical properties including abrasion and tear resistance
  • Temperature limit: 180°F (82°C)

Nitrile or Buna-N

Acrylonitrile Butadiene (NBR)

  • Generally resistant to fats, oils, greases, and aliphatic hydrocarbons
  • Not ozone resistant
  • Attacked by ketones; esters; aldehydes; and aromatic, chlorinated, and nitro hydrocarbons

SBR or Buna-S

Styrene Butadiene (SBR)

  • Fluid compatibility is similar to “Natural”
  • Good physical properties

Chlorobutyl

Chloro-Isobutylene-Isopren

  • Generally resistant to animal and vegetable fats, strong and oxidizing chemicals
  • Resistant to ozone
  • Attacked by petroleum solvents, coal, tar solvents, and aromatics hydrocarbons
  • Good heat resistance, weather resistance, and low permeability to air
  • Standard elastomer for Garlock® expansion joints
  • Temperature limit: 250°F (121°C)

HYPALON®

Chloro-Sulfonyl-Polyethylene

  • Excellent weather resistance – ideal expansion joint cover material for outdoor applications
  • Compatible with mild acids
  • HYPALON® is a registered trademark of DuPont Elastomers
  • Temperature limit: 250°F (121°C)

 

Fibers

The term “fiber” covers a very broad range of natural and man-made materials. Once again, only the most common fibers used in sealing devices are reviewed in this course; they are listed alphabetically by generic name.

 

Most Common Fiber Materials used in Fluid Sealing Components

Aramid

  • Man-made organic fiber
  • Introduced by DuPont under the trade name KEVLAR® in the early 1970s
  • Good wear resistance
  • Good thermal and electrical insulation properties
  • Very high tensile strength, high modulus, and low density
  • Starts degrading between 500°F (260°C) and 600 °F (315°C) with very little aramid left at 800°F (425°C)
  • Attacked by concentrated hot acids or caustics

Carbon

  • Rod-like fibers of various diameters and lengths
  • Produced by pyrolysis (heat treatment process) to various levels of carbon content materials (I.E. rayon, acrylonitriles, pitch, etc.)
  • Good heat and chemical resistance

Cellulose

  • Natural fibers; most common: cotton and so-called “vegetable” fibers
  • Readily available in huge quantities; low price
  • Moderate chemical and general fluid resistance
  • Not generally recommended for use over 250°F (121°C)

Fiberglass

  • Excellent heat resistance and incombustible
  • Begins to degrade at approximately 750°F (399°C)
  • Does not absorb moisture; will not rot or decay
  • Resistant to acids, oils, many solvents, weather, and corrosive vapors
  • Electrical insulator
  • Used in combination with aramid fiber to reinforce Garlock expansion joints

Graphite

  • Rod-like fibers of various diameters and lengths
  • Produced by special heat treatment of carbon fibers at approximately 5072°F (2800°C)
  • Excellent heat and chemical resistance
  • Versatile; popularity in the gasketing industry continues to grow

Mineral/Rock

  • Fibers are amorphous and highly homogenous because of their metamorphosis from volcanic rock
  • Do not burn; chemically inert
  • Resistant to high temperatures; above 930°F (500°C)

NYLON®

Tire Cord (expansion joints)

  • Man-made polyamide with high tensile strength and good ultimate elongation properties
  • Good resistance to common solvents, fuels, oils, and greases
  • Attacked by strong alkalines (caustics) and acids, oxidizing agents, phenol, and formic acid
  • Temperature limit: 250°F (121°C)

Polyester

  • High quality, synthetic material
  • In spun form, polyester has a very high density and thread count, making it resistant to permeation
  • Polyester cloth is considered the standard reinforcement material in Garlock expansion joints

Other Materials of Construction

Graphite, FEP, and PTFE are three commonly used components which are categorized separately in this module.

Graphite

  • One of the two crystalline forms of the element carbon (The other is diamond); man-made carbon, graphite, and diamonds also exist
  • One of the most stable and chemically-resistant materials in the world
  • Does not melt, but sublimes; changes from the solid to gas state, bypassing the liquid state, at temperatures over 5400°F (2980°C), or, in the presence of oxygen oxidation, above 850°F (450°C)
  • Excellent conductor of heat and electricity
  • Readily available in various forms; moderately priced to very expensive

Polytetrafluoroethylene (PTFE)

  • Man-made thermoplastic introduced in the late 1940s or early 1950s
  • Extremely good chemical inertness and resistance to a wide range of fluids; only a few, very rare fluids will attack it
  • Withstands a wide temperature range, from -450°F (-268°C) to 500°F (260°C)
  • A very low static coefficient of friction; very slippery
  • Poor heat conductor; good heat insulator
  • High coefficient of thermal expansion; swells significantly under heat
  • Flows (creeps) under relatively low loads, even at room temperature (usually stated as “cold flow”)
  • Can be readily blended with other materials to improve its features and performance characteristics
  • Readily available at moderately high prices

FEP

Fluorinated Ethylene Propylene

  • Similar chemical resistance to that of PTFE
  • In terms of Garlock® products, predominately used as the liner material in GUARDIAN® Expansion Joints
  • Temperature limit: 450°F (232°C)

Metals & Alloys

Metal is yet another common component of sealing devices. In many cases, metal components are used to reinforce the non-metallic components of a sealing device. In addition, the metal can be the main sealing element, such as with a double-jacketed gasket. Therefore, having a general understanding of the properties and temperature and chemical resistance of metals is important.

Common Metals used in Sealing Components

Aluminum

  • Excellent corrosion resistance to fresh and salt water
  • Maximum recommended operating temperature is 800°F (472°C)

Brass

  • Copper alloy typically used with non-oxidizing acids, alkaline, and neutral salt solutions
  • Maximum recommended operating temperature is 500°F (260°C)

Carbon Steel

  • Most common metal for double-jacketed gaskets
  • Poor resistance to corrosion
  • Not recommended for water or diluted acids
  • Maximum recommended operating temperature of 1000°F (540°C)

Copper

  • Used successfully in acetic acids, nitrates, and many organic chemicals
  • Maximum recommended operating temperature of 600°F (316°C)

HASTELLOY B®

  • Registered Trademark of Haynes International
  • Corrosion-resistant alloy
  • Resists hydrochloric acid, phosphoric acid, other halogen acids, and reducing conditions
  • Maximum recommended operating temperature of 2000°F (1090°C)

HASTELLOY C®

  • Registered trademark of Haynes International
  • Alloy with exceptional resistance to severe oxidizing conditions in nitric acid, free chlorine, and strong aqueous and acid solutions
  • Maximum recommended operating temperature is 2000°F (1090°C)

INCONEL®

  • Registered trademark of Inco Alloys International, Inc.
  • Excellent resistance to corrosion by halogen gases and compounds
  • Withstands high temperatures; maximum operating temperature of 2000°F (1090°C)

MONEL®

  • Registered trademark of Inco Alloys International, Inc.
  • Excellent resistance to most acids and alkalines, except extremely oxidant acids
  • Commonly used in hydrofluoric acid applications
  • Maximum recommended operating temperature of 1500°F (820°C)

Nickel

  • Resists caustic media and corrosion from neutral and distilled water
  • Maximum recommended operating temperature of 1400°F (760°C)

Stainless Steel Type 304

  • Widely used for industrial gasketing
  • Excellent corrosion resistance
  • Maximum recommended operating temperature of 1400°F (760°C)

Stainless Steel Type 316L

  • Greater corrosion resistance than SS Type 304, due to added molybendum
  • Maximum recommended operating temperature of 1400°F (760°C)

Stainless Steel Type 321

  • Similar to SS Type 304, but has titanium added
  • Widely used in high-temperature corrosive applications
  • Maximum recommended operating temperature of 1400°F (760°C)

Stainless Steel Type 347

  • Similar to SS Type 304, but has columbium and titanium added
  • Good performance in high-temperature corrosive applications, to 1600°F (870°C)

Stainless Steel Type 410

  • Martensitic stainless steel
  • Heat-treatable, 12% chromium steel
  • Good corrosion resistance, high strength
  • Maximum recommended operating temperature of 1200°F (650°C)

Titanium

  • Good resistance to wet chlorine and chlorine dioxide
  • Not suitable for dry chlorine
  • Maximum recommended operating temperature of 2000°F (1090°C)

Fillers

Fillers are any material added to another material, to improve quality, reduce cost, or both. Unfortunately, the term “filler” has often taken on the connotation of something used to cheapen products. Contrary to this, fillers can be very important ingredients when it comes to improving the physical properties and chemical resistance, which results in more efficient and effective sealing devices.

Fillers can take the form of powders, fibers, or a combination of the two.

Common Filler Materials for Sealing Components

Barium Sulfate

  • Commonly called “Barytes”
  • Natural and mined from the Earth, or can be synthetically manufactured
  • Good resistance against almost all fluids, except for concentrated sulfuric acid
  • Used in rubber products, compressed gasketing, and GYLON® Style 3510

Carbon Black

  • Same characteristics as carbon/graphite
  • Not recommended for temperatures over 850°F (450°C) in oxidizing atmosphere, or for strong chemical oxidizers
  • Used in some rubber products and compressed gasketing to enhance properties, such as chemical resistance

Ceramic

  • Fibrous, aluminosilicate filler material
  • Generally used for high-temperature, low-pressure applications, where sealability is not a primary concern
  • Does not interlock and densify under compressive stress, unlike other non-asbestos materials
  • Used in spiral wound gaskets
  • Valued for high-temperature capability to 2000°F (1090°C)

Flexible Graphite

  • Used in tape form as a filler in spiral wound gaskets
  • Excellent chemical resistance and fire safety
  • Temperature capability to 950°F (510°C) depending on grade of flexible graphite and application
  • Material makeup, such as leachable halogen content, can be controlled
  • Ideal for nuclear applications

PTFE

  • Widely used in GYLON® and spiral wound gaskets
  • High chemical resistance, low permeability
  • Especially successful in hydrocarbon alkylation units in refineries and in food-related industries
  • Temperature limitation with this material; not fire-safe

Silica

  • Natural material (sand)
  • Many different structures, all with similar properties
  • Recommended for most all fluids except inorganic fluorides, like hydrofluoric acid, and strong caustics

Conclusion and Test

This concludes the Garlock Materials of Construction course. You may proceed to the testing portion:

Take the Garlock Fluid Sealing Basics: Materials of Construction Test