ADDITION CURE

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Curing Two-Part Silicones for Potting, Encapsulating, and Mold Making

Two-part silicones are used for potting electronic assemblies, encapsulating electronic components, and making molds for cast urethane rubber. Each part contains functional ingredients, and the two parts are mixed together in a specific ratio. The entire system requires curing so that the silicone hardens and acquires its end-use properties. Curing, the crosslinking of polymer chains, is a chemical reaction that is accelerated using a catalyst. Sometimes, post-curing is also used. For design engineers who want to learn more about curing systems, this Gluespec Q&A answers frequently asked questions (FAQs).

What are some common systems for curing two-part silicones?

Two-part silicones that are used for potting, encapsulating, and mold making are usually either addition cured, or condensation cured. Addition curing uses a platinum catalyst for crosslinking or curing. Condensation curing uses an organotin catalyst instead. These are not the only curing systems for silicones, but they are the most common types for the two-part silicones that are used in potting, encapsulating, and mold making.

What are some of the advantages of addition cure silicones?

Addition cure silicones have quick curing times and very low shrinkage rates. Importantly, they are not subject to reversion, an unwanted process that returns a catalyzed silicone to a liquid state. Addition curing is also less prone to silicone migration, which can contaminate electronics, and provides more durable coatings. Plus, post-curing is not required for the silicone to achieve its ultimate properties. This reduces curing costs and speeds cycle times.

What are some of the disadvantages of addition cure silicones?

Cure inhibition, or catalyst poisoning, can occur if an addition cure silicone contacts amines, sulfur, phosphides, PVC plasticizers, sulfur vulcanized rubber, some epoxy resin catalysts, or tin catalyzed silicones. Cure inhibition is also caused by contact with the latex, vinyl, or neoprene gloves that workers wear to handle assemblies. In machine shops, oils in the air can cause mild cure inhibition. There is also the potential for cure inhibition if there is contact between an addition cure silicone and acrylics.

Is there anything that can be done to overcome these disadvantages?

Accelerated curing with heat, the careful control of substrates, and using an additional catalyst have all been shown to be effective in overcoming cure inhibition.

What are some of the advantages of condensation cure silicones?

Condensation cure silicones work well with most substrates and resist cure inhibition.  They are not  subject to reversion if the cured silicone has access to the atmosphere. They have a relatively low risk of cure failure and can support deep section curves.

What are some of the disadvantages of condensation cure silicones?

Condensation cure silicones are not the best choice for use with SBR rubber. They also have the potential for reversion if the silicone is totally enclosed and subject to heat and/or pressure over time. For example, reversion may occur if a condensation cured silicone is subjected to 150°F temperatures in a completely sealed environment for a period of several months.    

Do two-part condensation cure systems require atmospheric moisture for curing?

No, they do not. The moisture that is needed for crosslinking is included in the system.

What about one-part silicones?

One-part silicones are also available for potting, encapsulating, and mold making. For example, one-part room temperature vulcanizing (RTV) silicones are typically moisture cured. The moisture that they need for curing usually comes from the atmosphere. There are also one-part heat cured silicones that use an addition curing system. Because heat initiates cross-linking, the system components can be combined in an easily handled package and crosslinking will not occur until heat is applied.

VACUUM BAGGING TECHNIQUES

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What is vacuum bagging?

Vacuum bagging (or vacuum bag laminating) is a clamping method that uses atmospheric pressure to hold the adhesive or resin-coated components of a lamination in place until the adhesive cures. (When discussing composites, “resin” generally refers to the resin system— mixed or cured resin and hardener—rather than unmixed epoxy resin.)

Modern room-temperature-cure adhesives have helped to make vacuum bag laminating techniques available to the average builder by eliminating the need for much of the sophisticated and expensive equipment required for laminating in the past. The effectiveness of vacuum bagging permits the laminating of a wide range of materials from traditional wood veneers to synthetic fibers and core materials.

Fig: Sketch of a vacuum bag, the individual elements and a leakage.

SILICONE FOR VACUUM BAG

Silicones for Producing Reusable Vacuum Bags

  • Our silicone rubber is a brushable platinum cure silicone developed especially for making high performance, reusable vacuum bag. It is easy to mix and apply. Rubber can be applied with a brush or spatula to vertical surfaces without sagging.
  • CHEMZEST offers a series of addition cure silicone elastomers for the manufacture of reusable vacuum bags for resin infusion. These silicones formulated as a sprayable material allowing for exceptionally low cost composite manufacture using resin infusion technology.
  • Our silicone solutions enable composite manufacturers to decrease production times, achieve consistent part production and reduce material waste. In addition, the closed mold process enables a much safer working environment since VOC emissions are reduced.

General Attribute

  • 1:1 mix ratio
  • Easy to apply using fully automated mixing and spray equipment
  • Fast curing heat accelerated RTV
  • High tear and tensile strength for repeated uses of the bag
  • Low viscosity

Applications

  • Automotive parts such as bumpers and windscreens
  • Aerospace components
  • Marine & RV components
  • Laminating
  • Composite part building
  • Molded composites

How it works?

  • Vacuum bagging uses atmospheric pressure as a clamp to hold laminate plies together. The laminate is sealed within an airtight envelope.
  • The envelope may be an airtight mold on one side and an airtight bag on the other. When the bag is sealed to the mold, pressure on the outside and inside of this envelope is equal to atmospheric pressure: approximately 29 inches of mercury (Hg), or 14.7 psi.
  • As a vacuum pump evacuates air from the inside of the envelope, air pressure inside of the envelope is reduced while air pressure outside of the envelope remains at 14.7 psi. Atmospheric pressure forces the sides of the envelope and everything within the envelope together, putting equal and even pressure over the surface of the envelope.
  • The pressure differential between the inside and outside of the envelope determines the amount of clamping force on the laminate. Theoretically, the maximum possible pressure that can be exerted on the laminate, if it were possible to achieve a perfect vacuum and remove all of the air from the envelope, is one atmosphere, or 14.7 psi.
Fig: A typical vacuum bagging lay-up before and after vacuum is applied

Vacuum bagging equipment

The vacuum bagging system consists of the airtight clamping envelope and a method for removing air from the envelope until the epoxy adhesive cures. This section discusses the components of this system , which include both specialized equipment and commonly available materials.

Vacuum Bagging Materials

  • Release Fabric
  • Perforated Film
  • Breather material
  • Vacuum bag
  • Mastic sealant
  • The plumbing system
  • Mold release

Our product benefits

  • High mechanical characteristics
  • High dimensional stability
  • Self bonding properties ( a second layer can be cast within 24hrs after casting the first layer)
  • Good chemical resistance against polyester,vinylester
  • Perfect surfaces in both side of the mold
  • Translucent product in order to recognize the filling of the resin

MAJOR APPLICATIONS

CURING TWO PART SILICONE

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  Curing Two Part Silicones for Potting, Encapsulating and Mold Making

  • Two-part silicones are used for potting electronic assemblies, encapsulating electronic components, and making molds for cast urethane rubber.
  • Each part contains functional ingredients, and the two parts are mixed together in a specific ratio.
  • The entire system requires curing so that the silicone hardens and acquires its end-use properties.
  • Curing, the crosslinking of polymer chains, is a chemical reaction that is accelerated using a catalyst. Sometimes, post-curing is also used.

Addition Cure Silicones

Silicone elastomers are designed with either addition (platinum) cure or condensation (tin) cure chemistry. Addition curing systems are 2-part liquid silicones that utilise a platinum catalyst to cure by either room temperature vulcanisation (RTV) or heat to accelerate cure.

Addition cure silicones do not produce by-products during the crosslinking (curing) process. The cure chemistry takes place internally, making them ideal for moulds or parts that are manufactured in a sealed environment. Addition cure silicones have very low shrinkage properties with great dimensional stability when exposed to either humidity or heat. This type of chemistry should be considered if the final mould will be stored for long periods of time between use.

Properties include:

  • Extensive range of durometers/hardnesses
  • Compatible with silicone fluids to increase softness
  • Can be heat cured
  • Casting resin resistance
  • Low shrinkage, below 0.1%
  • High tear and tensile strength
  • Good abrasion resistance
  • Excellent dimensional stability resulting in durable moulds
  • Fine detail reproduction
  • Food grades available

Addition cure silicones can be used with various resins and materials including concrete, stone, brick, fibre glass filled resin, polyurethane, polyester, acrylic resin, and even another addition cure silicone.

Applications: 

General mouldmaking, Prototyping, Dental replication, Food moulding, Architectural replication & sculpting, Composites/fibre glass part production, Tampo pad printing, Special effects, Prosthetics & orthotics

Avoiding inhibition with addition cure silicones

When working with addition cure silicones, it is important to avoid inhibiting the cure process by bringing the uncured material into contact with certain chemical compounds. The poisoning of the cure catalyst stops the crosslinking necessary for the silicone to properly cure. The result of inhibition is tackiness at the pattern interface or a total failure of the silicone to cure.

Materials known to inhibit cure are sulphur-containing modeling clays, natural rubber such as latex and rubber gloves, masking tape, amine or sulphur-containing material, condensation cure (tin-catalysed) silicones, PVC stabilizers, and epoxy resin catalysts.

TIN CATALYST CURING

  • For liquid silicone rubber cured with a tin catalyst, it could be assumed that the tin catalyst does not respond to heat.
  • Only the addition of more catalyst or the crosslinker will increase the speed of the curing.
  • The higher the quantity of reactants used, the higher the amount of heat evolved during the curing process and the faster the curing process will be.
  • The amount limit of the catalyst or the crosslinker will depend on the reaction temperature; if it is too high, it could cause degradation in the silicone rubber, so the final product would have lower mechanical properties than desired.
  • The resultant temperature profile also depends on the thickness of the final product: the thicker the part, the lower the initial temperature of the reaction will be and the slower the temperature will be increased due to the slower thermal conduction but after some time the overall temperature will be higher in comparison with standard thickness products.

PLATINUM CATALYST CURING

  • For liquid silicone rubber cured with a platinum catalyst, the increase of the processing temperature has an effect similar to increasing the amount to be cured.
  • To optimize the speed in this case, in general, it could be said that for every ~10°C, the cure rate could be increased in approximately 20-25%.
  • If the built-up temperature is not well controlled, the probability of degradation will be higher. It is recommended that if the processing temperature is increased, the amount of curing agent should not be increased at the same.
  • First, it is necessary to analyze the effect of specific temperature on the cure speed and then, an adjustment of the curing agent.

RTV SILICONE IN AEROSPACE AND AVIATION

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Manufacturers in aerospace and aviation have used silicones since their inception, however not everyone is familiar with all of their capabilities. Silicones seal joints, coat and encapsulate electronics and insulate and shield sensitive equipment from extreme temperatures and weather exposure. The versatility of silicone and its high temperature resistance have made it a reliable choice for decades and today it is still one of the most effective materials used in aerospace and manufacturing.

Silicone supports engines that experience high temperatures during liftoff, as well as on the exterior of a space capsule that experiences low and high temperatures and needs shock absorption when re-entering Earths atmosphere. Silicones effectiveness and versatility make them suitable for atleast 20 different areas of a launch vehicle.

RTV Silicone Rubber:

RTV Silicone rubber is short form of room temperature vulcanization silicone rubber. Once part A and part B mixed together at normal room temperature, it will create High flexible to medium flexible rubbers. RTV silicone is available in a variety of viscosities-ranging from low viscosity options that can be incorporated with additives to boost the thermal protection properties, to high viscosity formulations that can be applied to overhead surfaces.

Aviation applications

  • Silicones are very effective for aircraft original equipment manufacturing(OEM) and for maintenance, repair and overhaul(MRO).
  • Aircraft components are frequently replaced due to wear experienced through time. Silicone offers convenience and efficiency benefits in MRO because it comes in individual use tubes for easy delivery and in dual cartridges that deliver the materials precisely and simultaneously to save time and avoid product waste.
  • Many epoxy and polyurethane adhesives can become rigid when cured and may not be able to absorb Coefficient of Thermal Expansion(CTE) mismatches between different substrates. Silicones have a low modulus that maintains flexibility even in extreme high and low temperatures, allowing silicone adhesives to more effectively cope with CTE mismatch effects.

Aircraft applications

  • Black box encapsulant
  • Avionic display unit adhesion
  • Protective coating for critical circuits, terminals
  • Radome sealant
  • Sealant, encapsulant: computers, LED modules, sensors
  • Engine component, thrust reverser thermal protection
  • Fuel tank coating, sealant
  • Epoxies and polyurethanes generally offer poor electrical properties at low or high temperatures and in damp conditions. They can also be harder to work with due to toxicity and an affinity for water absorption, and they are difficult to remove or repair when equipment needs to be serviced.
  • The strongest attribute of an RTV silicone is its ability to maintain critical properties throughout a wide temperature range. That temperature range makes RTV silicones suitable to bond lenses onto telescopes and secure optics onto satellites and other structures. Since this equipment remains in orbit for a long time, it is subjected to large temperatures fluctuations due to repeated, intermittent exposure to the sun, and silicones can withstand those extreme conditions.
  • A silicone coating is applied to electronic components to protect against extreme environmental conditions. RTV silicone are rubber and gel silicones that cure without heat and are used for bonding, sealing, encapsulation, coating and potting applications.

Other benefits of room temperature vulcanized(RTV) silicones

  • Heat resistance, flexibility-In thermal protection systems, RTV silicones can maintain their properties in extreme heat, such as securing thermal sheilds on the exterior of aircraft and space vehicles. They can maintain adhesion during the extreme heat of re-entry and remain elastomeric in low-temperature environments. They also protect launch pads and structures during launches and landings.
  • Spark, fire protection-RTV silicones resist long term smoke and fire penetration. They can be self-extinguishing, and the fumes from ignition are non-hazardous to humans. Silicones also insulates fuel lines to help keep fuel flowing in the event of an engine fire.

Electronics applications

  • Advanced aviation electronics have a very high power density that generates more heat than those typically used in the past. When circuit boards that support the operation of planes and radar systems generate heat, onboard electronics are also constantly exposed to fluctuating temperature throughout their lifespan. To last longer, electronics coatings and adhesives must outlast the effects of repeated temperature changes.
  • Room temperature vulcanizing(RTV) silicones are a prominent ingredient in aerospace manufacturing due primarily to their ability to withstand extreme temperatures while maintaining their physical properties. When protecting these delicate electronics and circuit board assemblies or sealing power modules and sensors, manufacturers should use compounds that provide stable dielectric, thermal and mechanical properties such as silicones. Thermally conductive silicones can also passively remove heat. There are many methods to apply liquid silicone to sensitive components, such as with pneumatic applicator guns, syringes and metered dispensive valves. The silicone is then cured into an elastomeric rubber that excels in thermal interface applications.
  • Electrostatic dissipative and electromagnetic shielding silicones can electrically ground composite structures while tolerating a low electrical charge.

ENCAPSULATION AND POTTING

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Flexible Epoxy and Silicone Rubber

EPOXY RESIN BUFFING

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Polishing resin is a relatively simple process that just takes a little patience and effort. This instructable will address how to polish resin to a high gloss. The same methods I will address in this how to, apply to all cast resin polishing, and can be used to polish virtually any type of resin be it polyester or epoxy based.
The method first starts with some good old fashioned detail sanding working up through the grits, from very rough, to a very fine wet sanding. Then we move into two different grits of polishing compounds, and finally finish everything off at the buffing wheel using two very fine polishing abrasives, and finally, a carnuba wax polish to buff everything to a bright shine.
When done correctly, well polished resin casts and parts look absolutely amazing, and are works of art, ready for display, jewelry and enjoyment in and of themselves.

Step 1: Cast Part

The support material is a waste product of the print and must first be cleaned off before polishing can begin. Use a pressure washer, surform tools, dental tools.

If you are polishing a cast resin part, clean the outside of the resin with soap and water to remove any mold release that may be on the part.

Step 2: Tools and Materials
Gather the tools and materials below to polish your resin part: sand paper 120, 180, 220, 400, 600, 800, 1000, 1500, 2000 grit. sanding block water.
scratch remover compound polishing compound
Lint free, scratch free polishing cloth mothers polishing ball Buffing wheel buffing compounds wax product
While there are many different buffing compounds and waxes available, I went to a regular car parts supplier box store and purchased low cost but totally effective rubbing compound made by Turtle Wax for car scratches, a Mothers Polishing Ball with a drill attachment and some Mothers Carnuba Car Wax

Step 3: Sand Paper Grits – From 120 to 2000

Start sanding the resin with 120 grit sandpaper. Make sure to sand all the surfaces of the resin part before going up to the next grit paper. It’s much easier to notice a deep scratch once the resin is sanded smooth and begins to become polished. The bummer with that however is that you’ve then got to backtrack all the way back to the beging and spot sand the blemish out. A better method is to sand the entire part comprehensively with the rough paper before moving up a grade.

Step 4: Hand Sanding

When we began polishing this piece of resin we were exclusively hand sanding. we took turns and rested before moving up to the next grit paper.

We used the sanding block only for the one flat side on this model, the rest of the time we just used our hands as a backer.

We experimented a bit using flexible foam sanding pads, and sponge-like backers on the sandpaper, but all in all, our hands proved to be a pretty effective and flexible support for the paper to get inside all the detailed contour sand crevices.

Step 5: Power Sanding

Larger sanders that one would want to use if you were working with a larger piece of resin.
It’s easy to make custom sanding pads of the finer grit sanding papers for the detail sander. Simply take a spent Fein brand pad, spray it down with 3M adhesive, and slap a piece of fine sandpaper on it that’s been cut down to the same size. Presto – cheap and reusable fine grit sanding pad.

Step 6: Wet Sand by Hand

Once you get to 400 grit or so, depending on the type of sandpaper that you are using, it’s time to start wet sanding.

This process we did by hand for more control, and so we wouldn’t get electrocuted. Start sanding at 400 and work your way up to 600, 800, 1000, 1500 and finally, 2000.

Step 7: Check for Scratches

We found it easiest to check for scratches by completely wiping down the resin with a clean towel and then wetting it down with water. If you rub the water in a bit with your fingers it helps to bring any potential scratches, pot marks and inconsistencies out for inspection.
If the resin passes the scratch test, keep on sanding all the way up to 2000. By 2000 it should start to look pretty clear, but not polished. That comes in the next step.

Step 8: Rubbing Compound

I used two different polishing compounds to start the polishing process – first was Turtle Wax brand Rubbing Compound.
Follow the instructions – apply a small amount to a clean polishing cloth and rub it vigorously onto the surface of the resin. Let it sit for a second and then buff it off with another part of the cloth.
This polishing compound is a finer grit than the sandpaper, but not quite as fine as the buffing compounds that are used on the mechanical buffing wheel.

Step 9: Polishing Compound

Follow the same procedure as described in the previous step for the finer of the two polishing compounds – Turtle Wax brand Polishing Compound.
This creamy white polishing compound really starts to bring out the initial polished surface in the resin…and in the next steps it just gets better and better.

Step 10: Mechanical Polishing With Mothers Ball

While we preformed the previous two steps by hand with a polishing cloth, I thought it’d be useful to try a mechanical solution to this process as well. I picked up a Mothers Ball polishing tool at the car parts store and loaded into the chuck of my corded drill.
Lock the drill trigger on, load the ball with polishing compound and polish all the surfaces of the resin piece. Hold on to the resin piece as the drill spins. It doesn’t have much friction, but if it caught en edge on the resin piece, it’s possible it might try to come away from your hands.
Where an apron as this step tends to flick polishing compound around and about.Since this photo was taken I’ve begun polishing these models on the drill press, as it spins the ball with a bit more stability and speed control

Step 11: Buffing Wheel – Tripoli

After polishing comes buffing on the motorized buffing wheel. Any motor that rotates at around 1500 – 2000 rpm will suffice. Mount the first all-linen buffing wheel in the kit to the arbor and load the wheel with tripoli compound. Again, I’m using a buffing kit from Beall Tool, but any buffing compound system that you’d like to work with will work just as well.Loading the wheel with compound means holding the bar to the wheel for a few seconds. Once some red material is deposited on the wheel, it’s good to go. If you are buffing a large area, you may need to reapply compound to the wheel.
Hold the resin piece tightly in your hands and engage it into the wheel.Always have the wheel spin down and away from you, and always buff on the bottom of the wheel in case something catches an edge – otherwise it will get launched right at you. If you buff down and away, it will at least get launched away from the operator.Always hold on to the part you are buffing with two hands, and try not engage any hard edge against the wheel. Better to buff the surface of the resin part parallel to the face of the buffing wheel, and never perpendicular to it as it has a tendency to “grab” the part.Keep the resin moving across the buffing wheel, never staying in the same place too long. The process builds up significant heat and we want to keep things cool by keeping everything on the move.

Step 12: Buffing Wheel – White Diamond

The Beall Kit’s next step is a diamond buffing compound. It gets used on a softer wheel than the first, so swap wheels, load up the new linen/cotton blend wheel with white diamond compound, and use the same buffing technique described
in the previous step.

It’s possible to buff the entire model – even concave areas by using different parts of the wheel, and even digging into the corner of the wheel if needed for smaller, detail areas

Step 13: Finish With Carnuba Wax

Swap wheels one last time to the all flannel wheel and load it with just a little bit of carnuba wax.

The more wax you load on the worse the final buffing will be since too much wax will build up upon the surface and ruin your finish! Just touch the carnuba wax bar to the wheel and load it up for a second or two. You can always reapply more later.

Step 14: How to Polish Small, Highly Detailed Parts Hands Free (hopefully)

I am currently working on a completely automated, “hands off” version of this process using lapidary equipment – a vibratory polisher and different abrasive mediums.

I hope to be able to achieve the same results over several hours or days of parts vibrating in different grit medias that could run unattended, except for the changing of the media as the part moves up the grits.
I’m also going to test spraying a clear high gloss resin, as well as flame polishing any surface too detailed, or too small to sand in order to achieve a glossy finish.

MONOCHLORAMINE-INTRODUCTION & APPLICATION

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Chloramines are a group of chemical compounds that contain chlorine and ammonia.

The particular type of chloramine used in drinking water disinfection is called monochloramine which is mixed into water at levels that kill germs but are still safe to drink.

pH and Monochloramine

  • If the pH of water is above 7 (neutral) then you naturally have monochloramine- the “chloramine” as used by water industry.
  • If pH is lower, get bi-chloramine and tri-chloramine.
  • Drinking water is pH adjusted.

Safe levels of Chloramine in water

  • Chloramine levels up to 4 milligrams per liter (mg/L) or 4 parts per million (ppm) are considered safe in drinking water.
  • At these levels, harmful health effects are unlikely to occur.
Fig: Concentration of monochloramine produced during chlorination of water.

CHLORINE VS MONOCHLORAMINE

S.NOCHLORINE CHLORAMINE
1Chlorine is a gaseous compound having a yellow green color and it is a toxic gas.Chloramine is a gaseous compound and it is comparatively less toxic gas.
2Chlorine dissipates and evaporates into the air quickly. Chlorine will usually evaporate after sitting for 24 hours.Chloramine is more stable and will last longer in the water system.
3Chlorine inactivated, no power to kill microbes at end of water delivery pipe.Chloramine still present, killing microbes at end of water delivery pipe.

APPLICATIONS

DRINKING WATER

  • Monochloramine is favored because it is less reactive and remains in solution longer, providing added protection from contamination.
  • It is safe for dialysis patients to drink, cook with and bathe in monochloraminated water because the digestive process neutralizes monochloramine before it enters the bloodstream.
  • Monochloramine is emerging as an integral part of controlling the growth of Legionella bacteria

Chloramine has been used as a drinking water disinfectant in the United States in places like Cleveland, Ohio, Springfield, Illinois, and Lansing, Michigan since 1929. In 1998, an EPA survey estimated 68 million Americans were drinking water disinfected with chloramine. Several major U.S. cities such as Philadelphia, San Francisco, Tampa Bay, and Washington, D.C. use chloramine to disinfect drinking water. Chloramine is recognized as a safe disinfectant and a good alternative to chlorine.

More Information

EPA: Drinking Water Regulationsexternal icon
EPA: Drinking Water Treatability Databaseexternal icon
EPA. Chloramines in Drinking Waterexternal icon

Monochloramine for wastewater reuse

Legionella growth and spread

  • Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.
  • Legionella reside in water distribution pipes and can live in premise water tanks where temperatures are between 20ºC and 50ºC

Temperature affects the survival of Legionella

Monochloramine Use for Prevention of Legionella

  • Monochloramine disinfection of municipal water supplies is associated with decreased risk for Legionnaires’ disease.
  • Increasing use of monochloramine in water supplies throughout the United States may reduce Legionella transmission and incidence of Legionnaires’ disease.
  • Controlling water temperatures is one of the most effective ways of preventing the growth and spread of Legionella bacteria.
  • The ideal temperature range for the growth of the bacteria is between 20 and 45 degrees Celsius. Outlet temperatures for cold water should therefore be kept below 20 degrees Celsius, and hot water outlets above 50 degrees Celsius to control the bacteria.

EU
The European drinking water guideline does not contain standards for chloramines. When chloramines are used, few disinfection byproducts, such as trihalomethanes, are formed. However, other disinfection byproducts can form. Examples are toxic halonitrils (cyano chloride), halonitromethanes (chloropicrin) and other nitrogen-rich compounds. Some of these compounds can endanger human health. When the European Drinking Water Directive is revised, standards for these compounds will be added.

USA
According to American guidelines by EPA, drinking water that is treated with chloramines can contain a maximum amount of 4 mg/L Cl2. (National Primary Drinking Water Regulations EPA, 2002)

WHO
The WHO (World Health Organization) only dictates a standard for monochloramine as a disinfectant. The standard is 3 mg/L. For di- and trichloramine there are no standards, because the available information is not satisfactory for the establishment of a health guideline. (WHO, Guidelines for drinking-water quality – 3rd edition. Chemical aspects).