Gasket types, generic
Description
For further information, please see AIC wiki Gaskets for Exhibit Cases
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', these materials are also used as spacers, washers, shims and seals.
Examples of some elastomers used in museums include:
| Material | Durometer Shore A (hardness) | General properties | Resistant to: | Attacked by: | Commercial names |
|---|---|---|---|---|---|
| Polyethylene foam | 50-60 | Strong, lightweight, closed cell, impact resistant, lightweight, low moisture absorption, high tensile strength, nontoxic, recyclable. Available as sheets, strips or rods | Excellent UV, ozone and chemical resistance. Water repellent | Plastazote, Evasote, Climaloc, Magic Foamcord | |
| Ethylene propylene diene monomer (EPDM) | 30-90 | Excellent resistant to ultraviolet light, ozone, oxidants, heat, and compression set | Resists the swelling effects of polar chemicals, animal and vegetable oils. | Mineral oils and solvents, aromatic hydrocarbons | |
| 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 | ||
| Fluorocarbon (FKM) | 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 |
| Isoprene (butyl rubber) | 40-80 | Excellent resistance to heat, oxygen and water. | Low gas permeation. High vibration absoprtion (dampening) | Hydrocarbons solvents and oils | |
| Nitrile rubber (NBR, Buna-N) | 20-100 | Good physical properties. Broad temperature range. | Resistant to water, petroleums and oils | ||
| 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 temerpature. | Teflon |
| Silicone rubber (dimethyl silicone) | 50-70 | Most stable of all elastomers. Resistant to sunlight, oxygen and moisture. 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 | |
| Aramid | |||||
| Cellular silicone sponge (poly-dimethyl siloxane also referred to as PDMS) | 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. | ||||
| 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