A airtight seal is a sealing type that makes an airtight airtight object (excluding parts of air, oxygen, or other gases). The term was originally applied to an airtight glass container, but because of the advanced technology it applied to a larger material category, including rubber and plastic. Hermetic seals are essential for proper and safe functioning of many electronic products and health care. Used technically, expressed along with specific test methods and conditions of use.
Video Hermetic seal
Etimologi
The word hermetic comes from the Greek god Hermes, through alchemical vocabulary. Alkemis invented the process of making airtight glass tubes, which they used for distillation. This process uses a secret seal, whose discovery is attributed to the legendary alchemical inspiration, Hermes Trismegistus.
Maps Hermetic seal
Usage
Some types of packaging should keep the seal against the gas flow: food, medicines, some chemicals and some consumer goods. This term can explain food preservation practices, such as packing and vacuum canning. Barrier packs include containers such as glass, aluminum cans, metal foil, and high barrier plastic.
The buildings are designed with the principle of sustainable architecture using airtight technology to save energy. Under low energy buildings, passive houses, low-energy homes, self-contained homes, zero energy buildings, and superinsulation standards, the structure must be more airtight than ever. Air resistance, sealing of construction joints and service penetration (holes for pipes, etc.) Achieve this. Airtight minimizes the amount of warm (or cold) air that can pass through the structure, so that mechanical ventilation systems can recover heat before removing the air from the outside. The green building may include a window that combines insulated triple-pane insulated glass with argon or krypton gas to reduce thermal conductivity and increase efficiency. In landscaping and exterior construction projects, airtight seals protect public services and electrical connections of landscape and connection lighting. Many other specific applications must meet airtight standards for waterproof or steam resistant for human safety and proper functioning.
Applications for hermetic sealing include semiconductor electronics, thermostats, optical devices, MEMS, and switches. It is used for electrical or electronic components that must be secure against water vapor and foreign objects to maintain proper function and reliability.
The Hermetic Closure for airtight conditions is used in the archiving of significant historical items. In 1951, the US Constitution, the US Declaration of Independence, and the Bill of Rights US were sealed with helium gas in a glass case stored at the US National Archives in Washington, DC. In 2003, they were transferred to a new glass box sealed with argon.
Type epoxy hermetic seal
A typical epoxy resin has a group of hydroxyl pendants (-OH) along their chain that can form strong polar bonds or appeals to the oxide or hydroxyl surface. Most inorganic surfaces - that is, metals, minerals, glasses, ceramics - have a polarity that has a high surface energy. An important factor in determining good adhesive strength is whether the surface energy of the substrate is close to or higher than the adhesive surface energy of the adhesive.
Certain epoxy resins and processes may create a hermetic bond to copper, brass, or epoxy itself with similar thermal expansion coefficients, and are used in the manufacture of electric hermetic and hermetic hermetic seals. The epoxy hermetic seal design can be used in airtight seal applications for vacuum or low or high pressure, effectively sealing gases or liquids including helium gas to very low levels of helium gas leaks similar to glass or ceramics. The hermetic epoxy seal also offers the flexibility of a wire sealing design or copper pin, rather than the much smaller electrically electric Kovar pin required in a ceramic hermetic glass or seal. Epoxy hermetic seals have a more limited operating temperature range compared to glass or ceramic seals with operating range typically -70 ° C to 125 ° C or 150 ° C, although some hermetic epoxy designs are capable of reaching 200 ° C.
Type of hermetic glass-to-metal seal
When the glass and the sealed metal have the same thermal expansion coefficient, the "suitable seal" obtains its power from the bond between the glass and the metal oxide. This type of glass-to-metal hermetic seal is weaker than two types and is commonly used for low intensity applications such as in alkaline bulbs.
"Compression seals" occur when glass and metal have different thermal expansion coefficients so that the metal condenses around compacted glass when cooled. Compression seals can withstand very high pressures and are used in a variety of industrial applications.
ceramic-to-metal hermetic seal
Co-fired ceramic seals are an alternative to glass. Ceramic seals outweigh the barriers of glass design to metal seals due to superior hermetic performance in high-pressure environments that require strong seals. Choosing between glass versus ceramics depends on application, weight, thermal solution and material requirements.
Glassware sealing
Sealing solids
The pointed glass joint can be sealed tightly with PTFE sealing rings (high vacuum hole, air leakage level 10 -6 mBar * L/dt and below), o-ring (encapsulated o-ring) or PTFE Arm, sometimes used as a substitute for fat soluble in contamination. The PTFE ribbon, PTFE resin string, and wax are other alternatives that find widespread use, but require little care when winding into the connection to ensure a good seal is generated.
Grease
The oil thin films made for this application can be applied to the glass surface of the soil to be connected, and the inner connection is inserted into the outer joint so that the glass surface of the soil from each side is adjacent to make the connection. In addition to making leaky connections, the lubricant allows the two connections to be more easily separated. The potential disadvantage of such greases is that if used in laboratory glass for a long time in high-temperature applications (such as for continuous distillation), the fat can eventually contaminate the chemicals. Also, reagents can react with fat, especially under vacuum. For this reason, it is advisable to apply a fat light ring on the tip of the pointed fat and not the tip, to keep it from the inside of the glass. If the fat smears the entire surface of the taper on mating, it is overused. Using greases specially designed for this purpose is also a good idea, as it is often better under sealing under vacuum, thicker and less likely to flow out of the taper, into a liquid at a higher temperature than Vaseline (a common substitute) and more inert chemically than any other substitute.
Clean
The ground glass joint is translucent when it is physically free of debris and is clean. Solvents, reaction mixtures, and old fats appear as transparent spots. The grease may be removed by wiping with a suitable solvent; ether, methylene chloride, ethyl acetate, or hexane work well for silicone-based gases and hydrocarbons. Fluoride-based greases are strongly unaffected by organic solvents. Most chemists simply remove it as much as possible. However, some fluorinated solvents can remove fluoroether grease, but are more expensive than laboratory solvents.
Test
Standard test methods are available to measure water vapor transmission rates, oxygen transmission rates, etc. Packaging materials. Complete packages, however, involve heat seals, connections, and closures that often reduce the effective barrier of the packet. For example, a glass from a glass bottle may have an effective total barrier but closing the screw cap and cover liner may not.
See also
- Building insulation
- Glass-to-metal seal
- Hot sealer
- Permeation
Note
Source of the article : Wikipedia
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