Difference between revisions of "Gasket Types"

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For further information, please see AIC wiki [http://www.conservation-wiki.com/wiki/Using_Gaskets_to_Seal_Exhibit_Cases Gaskets for Exhibit Cases]
 
For further information, please see AIC wiki [http://www.conservation-wiki.com/wiki/Using_Gaskets_to_Seal_Exhibit_Cases Gaskets for Exhibit Cases]
 
[[File:Gaskets NPS.jpg|thumb|Gasket types<br>Credit: National Park Service]]
 
[[File:Gaskets NPS.jpg|thumb|Gasket types<br>Credit: National Park Service]]
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A compressible material used in an interface to reduce gaps and create tighter fitting joints. Gaskets are held under pressure to reduce leakage, transmission, and or vibration.  As such, in museums, gaskets can be used to minimize air exchange between sealed cases and museums, to compensate for alignment irregularities between two edges, and to reduce potential for the transfer of dust, dirt, pollutants and pests. In the past, [[natural rubber]], [[paper]], [[metal]], [[felt]], [[asbestos]], and [[cork]] were used for gaskets.  More recently, synthetic options, called elastomers have become available.
+
A compressible material used in an interface to reduce gaps and create tighter fitting joints. Gaskets are held under pressure to reduce leakage, transmission, and or vibration.  As such, in museums, gaskets can be used to minimize air exchange between sealed cases and museums, to compensate for alignment irregularities between two edges, and to reduce potential for the transfer of dust, dirt, pollutants and pests. In the past, [[natural rubber]], [[paper]], [[metal]], [[felt]], [[asbestos]], and [[cork]] were used for gaskets.  More recently, synthetic options, called elastomers have become available. While this record is named 'Gasket', elastomers are also used as spacers, washers, shims and seals.  Some commercial products are filled with glass spheres, silica, graphite, pigments and other materials
  
−
Examples of some elastomers include:
+
Examples of some elastomers include:
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
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! Durometer Shore A (hardness)
 
! Durometer Shore A (hardness)
 
! General properties
 
! General properties
−
! Resistant to:
+
! Advantages
−
! Attacked by:
+
! Disadvantages
 
! Commercial names
 
! Commercial names
 
|-
 
|-
−
! Polyethylene foam
+
| Polyethylene   (LDPE, HDPE)
−
!
+
| 50-60
−
! Available as sheets, strips or rods
+
| Exceptional shock absorption and  cushioning; strong, lightweight, closed cell, impact resistant, lightweight,  low moisture absorption, high tensile strength, nontoxic, recyclable
−
!
+
| Water repellant; resistant to  most solvents; inert to biological attack
−
!
+
| Emits some methane and ethylene
−
! Climaloc, Magic Foamcord
+
| Climaloc, Ethafoam; Magic   Foam Cord; Plastazote; Volara; Zotefoam
 
|-
 
|-
−
| [[Ethylene propylene diene]] monomer (EPDM)
+
| Polypropylene  (EPP)
 +
|
 +
| Lightweight flexible; excellent  thermal insulation; readily resumes its original shape; absorbs impacts  without breaking, recyclable
 +
| Resists moisture and chemicals
 +
| Poor resistance to UV and high  temperatures; not recommended for outdoor use
 +
| Propafoam; Propazote; Polyzote;  Microfoam; Strandfoam
 +
|-
 +
| Ethylene propylene diene monomer (EPDM)
 
| 30-90
 
| 30-90
−
| Excellent resistant to  ultraviolet light, ozone, oxidants, heat, and compression set
+
| Excellent resistant to  ultraviolet light, ozone, oxidants, heat, and compression set , economical,  good durability
 
| Resists the swelling effects of  polar chemicals, animal and vegetable oils.
 
| Resists the swelling effects of  polar chemicals, animal and vegetable oils.
 
| Mineral oils and solvents,  aromatic hydrocarbons
 
| Mineral oils and solvents,  aromatic hydrocarbons
−
|  
+
| Santoprene
 
|-
 
|-
−
| [[Ethylene vinyl acetate]] closed-cell elastomeric seal (EVA)
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| Ethylene   vinyl acetate closed-cell elastomeric seal (EVA)
−
|
 
−
| Closed cell foam that is  lightweight, odorless with good flexibility and softness
 
−
| Excellent ozone, chemical  resistance.  Good acoustic properties
 
−
| low resistance to heat and  solvents
 
 
|  
 
|  
 +
| Lightweight, odorless with good  flexibility and softness; good durability; easy to work with, can be shaped  by heat
 +
| Excellent UV, ozone and chemical  resistance.  Good acoustic properties
 +
| low resistance to heat and  solvents; can give off vinegar odor
 +
| not generally used in museums
 
|-
 
|-
−
| [[Fluorocarbon]]   (FKM)
+
| Fluorocarbon  elastomer
 
| 50-95
 
| 50-95
 
| Excellent fluid resistance.  Work well at low temperatures.
 
| Excellent fluid resistance.  Work well at low temperatures.
 
| Very good chemical resistance to  acids and oils as well as hydrocarbon and halogenated solvents
 
| Very good chemical resistance to  acids and oils as well as hydrocarbon and halogenated solvents
 
| Ketones, low molecular weight  esters and nitro-containing hydrocarbons.
 
| Ketones, low molecular weight  esters and nitro-containing hydrocarbons.
−
| Viton
+
| Viton, FKM
 
|-
 
|-
−
| [[Isoprene]]   (butyl rubber)
+
| Isoprene  (butyl rubber)
 
| 40-80
 
| 40-80
 
| Excellent resistance to heat,  oxygen and water.
 
| Excellent resistance to heat,  oxygen and water.
−
| Low gas permeation.  High vibration absoprtion (dampening)
+
| Low gas permeation.  High vibration absorption (dampening)
 
| Hydrocarbons solvents and oils
 
| Hydrocarbons solvents and oils
 
|  
 
|  
 
|-
 
|-
−
| [[Nitrile rubber]] (NBR, Buna-N)
+
| Nitrile rubber (NBR, Buna-N)
 
| 20-100
 
| 20-100
−
| Good physical properties. Broad   temperature range.
+
| Good physical properties; stong   and durable with broad temperature range.
−
| Resistant to water, petroleums   and oils
+
| Resistant to water, solvents,  petroleums and oils
−
|  
+
| Attacked by ozone and  chlorinated solvents
−
|  
+
| Krynac
 
|-
 
|-
−
| [[Polychloroprene]]
+
| Polychloroprene
 
| 15-95
 
| 15-95
 
| Good weathering, flame  retardant.  High tensile and tear  strength
 
| Good weathering, flame  retardant.  High tensile and tear  strength
 
| Moderate chemicals and acids,  ozone, oils fats, greases and  many  solvents.
 
| Moderate chemicals and acids,  ozone, oils fats, greases and  many  solvents.
 
| Strong oxidizing acids, esters,  ketones, chlorinated, aromatic and nitro hydrocarbons
 
| Strong oxidizing acids, esters,  ketones, chlorinated, aromatic and nitro hydrocarbons
−
| [[Neoprene]]
+
| Neoprene
 
|-
 
|-
−
| [[Polytetrafluoroethylene]] (PTFE)
+
| Polytetrafluoroethylene (PTFE)
 
| 73
 
| 73
 
| Good electrical insulator.  Inflammable and stable to light. Inert, often used in drug and food contact
 
| Good electrical insulator.  Inflammable and stable to light. Inert, often used in drug and food contact
 
| Hydrophobic and very resistant  to all solvents, acids, and bases
 
| Hydrophobic and very resistant  to all solvents, acids, and bases
−
| Low strength and susceptible to  creep at room temerpature.
+
| Low strength and susceptible to  creep at room temperature. Does not return to pre-compression position
−
| [[Teflon]]
+
| Teflon
 
|-
 
|-
−
| [[Silicone|Silicone rubber]] (dimethyl silicone)
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| Silicone   rubber (dimethyl silicone)
 
| 50-70
 
| 50-70
−
| Most stable of all   elastomers.  Resistant to sunlight,   oxygen and moisture. No odor or taste.
+
| Most stable of all elastomers;   will bounce back even after long compression.   No odor or taste.
 
| Resistant to high and low  temperature ranges, fatigue, most chemicals, oils, oxygen, and ozone
 
| Resistant to high and low  temperature ranges, fatigue, most chemicals, oils, oxygen, and ozone
 
| Poor resistance to aromatic  solvents.  May have residual silicone  oil that creeps to other surfaces.
 
| Poor resistance to aromatic  solvents.  May have residual silicone  oil that creeps to other surfaces.
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|  
 
|  
 
|-
 
|-
−
| Aramid
+
| Nylon  (polyamide)
 
|  
 
|  
 +
| Lightweight, tough, strong,  very durable; resistant to chemicals, does not absorb gases or water; can be  used outdoors
 
|  
 
|  
 
|  
 
|  
 +
| Nomex; ZotekNB-50; Polyamide  NB;
 +
|-
 +
| Chloroprene
 
|  
 
|  
 +
| Closed cell is water proof, less  compressible and more expensive; Open cell is breathable.
 +
| Both types are inert, flame  resistant, and durable with excellent resistance to water, oils, and  chemicals.
 +
| Has potential for causing  allergic reactions; attacked by most acids and organic solvents
 +
| Duprene; Neoprene
 +
|-
 +
| Polystyrene,  expanded (EPS) or extruded  (XPS)
 
|  
 
|  
 +
| EPS is friable and breaks  easily; good thermal insulators, easy to cut; XPS is stiffer, both  dimensionally stable; inexpensive, not recyclable
 +
| water resistant but not  water-proof
 +
| Sunlight can cause bleaching and  degradation; some products use halogenated products  that are toxic and/or may corrode metal
 +
| not recommended for use in  museums
 
|-
 
|-
−
| Cellular   silicone sponge (poly-dimethyl siloxane also referred to as PDMS)
+
| Polyurethane   foam (PU-F)
 
|  
 
|  
−
| silicone rubber that has been   foamed into a uniform unicellular structure. It has the same characteristics   as silicone rubber and is shaped by either extrusion or cutting.
+
| Wide variety of densities;   commonly used for indoor products; often filled to improve mechanical   strength
 
|  
 
|  
 +
| Deterioration accelerated by UV  and water; usually contains flame retardants (Al hydroxides or halogenated  compounds); may fog
 +
| not recommended for use in  museums
 +
|-
 +
| Polyvinyl  chloride (PVC, vinyl)
 
|  
 
|  
 +
| Resistant to water and abrasion;  rigid; easily cut; can be shaped with heat;
 
|  
 
|  
 +
| Heat can release noxious fumes;  does not fully spring back when compressed
 +
| not recommended for use in  museums
 
|-
 
|-
 
| Magnetic gaskets
 
| Magnetic gaskets
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|}
 
|}
  
 +
== Resources and Citations ==
 +
* Jean Tetreault ''Products Used in Preventive Conservation'' CCI, December 2017. [https://www.researchgate.net/publication/323153775_Products_Used_in_Preventive_Conservation Link]
 +
* Blaylock Gasket and Packing: [https://www.blaylock-gasket.com/plastic-material.html?_vsrefdom=ppcbing&ex=9jt0e4-5bignv-kw7r4s&utm_source=bing&utm_medium=cpc&utm_term=Polyethylene%20Gasket&utm_campaign=Blaylock&msclkid=d22517df1cfc1d844c5d7121b9bf0f9e&utm_content=Polyethylene%20Gasket Comparison table]
  
 
[[Category:Materials database]][[Category:MWG]][[Category:Comparisons]][[Category:Gaskets]]
 
[[Category:Materials database]][[Category:MWG]][[Category:Comparisons]][[Category:Gaskets]]

Latest revision as of 11:38, 3 October 2024

Gasket types: 1. o ring, 2. fiber washer, 3. paper gaskets, 4. cylinder head gasket
Credit: Sonett72, Wikipedia

Description

For further information, please see AIC wiki Gaskets for Exhibit Cases

Gasket types
Credit: National Park Service

A compressible material used in an interface to reduce gaps and create tighter fitting joints. Gaskets are held under pressure to reduce leakage, transmission, and or vibration. As such, in museums, gaskets can be used to minimize air exchange between sealed cases and museums, to compensate for alignment irregularities between two edges, and to reduce potential for the transfer of dust, dirt, pollutants and pests. In the past, Natural rubber, Paper, Metal, Felt, Asbestos, and Cork were used for gaskets. More recently, synthetic options, called elastomers have become available. While this record is named 'Gasket', elastomers are also used as spacers, washers, shims and seals. Some commercial products are filled with glass spheres, silica, graphite, pigments and other materials

Examples of some elastomers include:

Material Durometer Shore A (hardness) General properties Advantages Disadvantages Commercial names
Polyethylene (LDPE, HDPE) 50-60 Exceptional shock absorption and cushioning; strong, lightweight, closed cell, impact resistant, lightweight, low moisture absorption, high tensile strength, nontoxic, recyclable Water repellant; resistant to most solvents; inert to biological attack Emits some methane and ethylene Climaloc, Ethafoam; Magic Foam Cord; Plastazote; Volara; Zotefoam
Polypropylene (EPP) Lightweight flexible; excellent thermal insulation; readily resumes its original shape; absorbs impacts without breaking, recyclable Resists moisture and chemicals Poor resistance to UV and high temperatures; not recommended for outdoor use Propafoam; Propazote; Polyzote; Microfoam; Strandfoam
Ethylene propylene diene monomer (EPDM) 30-90 Excellent resistant to ultraviolet light, ozone, oxidants, heat, and compression set , economical, good durability Resists the swelling effects of polar chemicals, animal and vegetable oils. Mineral oils and solvents, aromatic hydrocarbons Santoprene
Ethylene vinyl acetate closed-cell elastomeric seal (EVA) Lightweight, odorless with good flexibility and softness; good durability; easy to work with, can be shaped by heat Excellent UV, ozone and chemical resistance. Good acoustic properties low resistance to heat and solvents; can give off vinegar odor not generally used in museums
Fluorocarbon elastomer 50-95 Excellent fluid resistance. Work well at low temperatures. Very good chemical resistance to acids and oils as well as hydrocarbon and halogenated solvents Ketones, low molecular weight esters and nitro-containing hydrocarbons. Viton, FKM
Isoprene (butyl rubber) 40-80 Excellent resistance to heat, oxygen and water. Low gas permeation. High vibration absorption (dampening) Hydrocarbons solvents and oils
Nitrile rubber (NBR, Buna-N) 20-100 Good physical properties; stong and durable with broad temperature range. Resistant to water, solvents, petroleums and oils Attacked by ozone and chlorinated solvents Krynac
Polychloroprene 15-95 Good weathering, flame retardant. High tensile and tear strength Moderate chemicals and acids, ozone, oils fats, greases and many solvents. Strong oxidizing acids, esters, ketones, chlorinated, aromatic and nitro hydrocarbons Neoprene
Polytetrafluoroethylene (PTFE) 73 Good electrical insulator. Inflammable and stable to light. Inert, often used in drug and food contact Hydrophobic and very resistant to all solvents, acids, and bases Low strength and susceptible to creep at room temperature. Does not return to pre-compression position Teflon
Silicone rubber (dimethyl silicone) 50-70 Most stable of all elastomers; will bounce back even after long compression. No odor or taste. Resistant to high and low temperature ranges, fatigue, most chemicals, oils, oxygen, and ozone Poor resistance to aromatic solvents. May have residual silicone oil that creeps to other surfaces.
Styrene butadiene (SBR, Buna-S) 40-100 Low cost, general purpose elastomer. Excellent flex and strength Resistant to alcohols and ketones Petroleum based fluids
Nylon (polyamide) Lightweight, tough, strong, very durable; resistant to chemicals, does not absorb gases or water; can be used outdoors Nomex; ZotekNB-50; Polyamide NB;
Chloroprene Closed cell is water proof, less compressible and more expensive; Open cell is breathable. Both types are inert, flame resistant, and durable with excellent resistance to water, oils, and chemicals. Has potential for causing allergic reactions; attacked by most acids and organic solvents Duprene; Neoprene
Polystyrene, expanded (EPS) or extruded (XPS) EPS is friable and breaks easily; good thermal insulators, easy to cut; XPS is stiffer, both dimensionally stable; inexpensive, not recyclable water resistant but not water-proof Sunlight can cause bleaching and degradation; some products use halogenated products that are toxic and/or may corrode metal not recommended for use in museums
Polyurethane foam (PU-F) Wide variety of densities; commonly used for indoor products; often filled to improve mechanical strength Deterioration accelerated by UV and water; usually contains flame retardants (Al hydroxides or halogenated compounds); may fog not recommended for use in museums
Polyvinyl chloride (PVC, vinyl) Resistant to water and abrasion; rigid; easily cut; can be shaped with heat; Heat can release noxious fumes; does not fully spring back when compressed not recommended for use in museums
Magnetic gaskets 79-80 A silicone rubber gasket filled with magnetite. Can be molded and extruded as needed Elastosil R781 (Wacker)

Resources and Citations

  • Jean Tetreault Products Used in Preventive Conservation CCI, December 2017. Link
  • Blaylock Gasket and Packing: Comparison table

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