（北）美国家用水管最弱寿命部件，定期导致水龙头开关等报废，逼迫房主换新：O-ring 材料化工

（人工）橡胶密封圈。一般完好使用寿命2-3年吧。之后渣化破损，但还能拖用几年。

19780年代以前多是用美国（杜邦）的制造的橡胶密封圈。受命比较长。90年代开始黑心渣化用便宜的全球（中国）橡胶密封圈。使用寿命大大缩短。黑心渣会流入饮用水，有可能被饮用，还可能堵塞水龙头口的过滤网水流腻腻歪歪的（可以打开清理）。

水龙头开关的金属配件部分的寿命很久，可达几十年，所谓Life time。但金属和金属无法密封水漏，因为开关拧转部件配合必须有一定的容纳轻松活动的间隙。否则太紧压，无法开关，和或拆装。机械制造上有个正负DELTA

例如 配合直径15毫米+-0.05 之类的。如果不加橡胶密封圈的话，这会渗漏水的。

橡胶密封圈会逐渐分解黑渣化。而且开关拧动也会压力磨损之间的密封圈。这是最弱寿命命部件。几年后渗漏水很糟心。成本也就是几分钱。但是你很难买到尺寸材料正好配合的密封圈。所以DIY自己修理时一般是换新一套水阀芯（cartridge），2-30刀。或花钱雇人换新一整套水龙头，几百刀；或连台柜一起换新一整套，顺便按装一套石板面，几千刀；或换新整个浴室或厨房，可达几万刀。无论你咋换新一套，花多少万，几分钱O-ring 还装在其内，几年后渗漏水重新糟心。到目前为止，这是个可解的无解问题。

1984年 美国航天机挑战号因为O-ring泄露导致爆炸的惨剧

Google AI 材料化工信息：

• Potable Water Safety: For O-rings used in drinking water systems, materials (especially EPDM and Silicone) must be certified to standards such as NSF/ANSI 61 or WRAS BS6920 to ensure they do not leach contaminants into the water.
• Temperature: EPDM is excellent for the temperature ranges found in standard hot water heaters and supply lines. Silicone can handle higher temperatures (e.g., specific water heating ports) but is less physically durable.
• Chemical Exposure: The main differentiator is resistance to oils/grease vs. water/steam/acids. EPDM will degrade if exposed to petroleum products, while Nitrile will degrade with ozone and certain acids.
• Durability: Nitrile has good abrasion resistance, making it suitable for dynamic seals, while silicone is best suited for static seals due to poor tear strength. 

These articles compare the temperature resistance and chemical compatibility of EPDM, Nitrile, and Silicone O-ring materials for plumbing applications.

Common Types of O-ring Materials - R.E. Purvis

This article will discuss some of the common O-ring materials available. * Nitrile (NBR) Nitrile is a popular O-ring material due ...

R.E. Purvis

 

EPDM vs. Buna-N | Arizona Sealing Devices, Inc.

Aug 18, 2022 — While both EPDM and Buna-N rubbers are durable, reliable, and resistant to certain types of conditions, each material ...

Arizona Sealing Devices, Inc.

 

• Excellent Weathering Resistance: EPDM has superior resistance to UV radiation, ozone, and general weathering, making it ideal for outdoor applications and long-lasting seals.
• Temperature Tolerance: It functions well across a broad temperature range, typically from approximately -60°F to 300°F (-50°C to 150°C).
• Water and Steam Resistance: It resists hot water and steam very well, which is why it is the go-to material for most household plumbing O-rings and gaskets.
• Chemical Resistance: EPDM offers good resistance to many polar substances, including dilute acids, alkalis, and brake fluids.
• Electrical Insulation: It has good electrical insulating properties, making it useful in electrical applications. 

EPDM is a complex polymer (a large molecule made of repeating subunits), so it does not have a single fixed molecular formula or a simple, specific structural diagram like a small, simple molecule such as water (

H2OH sub 2 O

H2O

). Its composition is a variable mix of three different monomers. 

Molecular Chemical Formula 

The formula for EPDM is represented generally to show the repeating monomer units in a variable ratio: 

(C2H4)n⋅(C3H6)m⋅(Diene)popen paren C sub 2 H sub 4 close paren sub n center dot open paren C sub 3 H sub 6 close paren sub m center dot open paren Diene close paren sub p

(C2H4)????⋅(C3H6)????⋅(Diene)????

 

• 

  nn

  ????
  represents the variable number of ethylene units (
  

  C2H4C sub 2 H sub 4

  C2H4
  ).
• 

  mm

  ????
  represents the variable number of propylene units (
  

  C3H6C sub 3 H sub 6

  C3H6
  ).
• 

  pp

  ????
  represents the small, variable number of diene units. 

The ratio of

nn

????

and

mm

????

(ethylene and propylene content) can vary from 45% to 75%, and the diene content is usually low, around 2% to 12% by weight. This variability means EPDM refers to a class of rubber materials, not one specific compound. 

Structural Formula 

EPDM's structure consists of a main saturated carbon backbone (like polyethylene or polypropylene), with a small side chain containing a double bond from the diene monomer. This saturated backbone is key to its excellent resistance to ozone and UV light. 

The structural representation is complex and typically shown as a chain of repeating units. The diene monomer used can be one of several types, most commonly: 

• Ethylidene norbornene (ENB)
• Dicyclopentadiene (DCPD)
• Vinyl norbornene (VNB) 

A simplified representation of the polymer chain backbone (ignoring the specific diene structure) would show a random arrangement of ethylene and propylene units: 

—[CH2—CH2]n—[CH2—CH(CH3)]m—[Diene Unit]—— open bracket CH sub 2 —CH sub 2 close bracket sub n — open bracket CH sub 2 —CH open paren CH sub 3 close paren close bracket sub m — open bracket Diene Unit close bracket —

—[CH2—CH2]????—[CH2—CH(CH3)]????—[Diene Unit]—

The double bonds on the side chains (from the diene units) are what allow the polymer chains to be cross-linked (vulcanized) with sulfur to form the final elastic rubber material.