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FAQ

Sealant FAQ

Q.1: What is Sealant?

A sealant is a viscous material that changes state to become solid, once applied, and is used to prevent the penetration of air, gas, noise, dust, fire, smoke or liquid from one location through a barrier into another. Typically, sealants are used to close small openings that are difficult to shut with other materials, such as concrete, drywall, etc. Desirable properties of sealants include insolubility, corrosion resistance, and adhesion. Uses of sealants vary widely and sealants are used in many industries, for example, construction, automotive and aerospace industries.

Q.2: Why sealant differs from adhesive?

The main difference between adhesives and sealants is that sealants typically have lower strength and higher elongation than do adhesives. Since the main objective of a sealant is to seal assemblies and joints, sealants need to have sufficient adhesion to the substrates and resistance to environmental conditions to remain bonded over the required life of the assembly. When sealants are used between substrates having different thermal coefficients of expansion or differing elongation under stress, they need to have adequate flexibility and elongation. Sealants generally contain inert filler material and are usually formulated with an elastomer to give the required flexibility and elongation. They usually have a paste consistency to allow filling of gaps between substrates. Low shrinkage after application is often required. Many adhesive technologies can be formulated into sealants.

Q.3: What is silicone sealant?

Silicone sealant or adhesive is a powerful, flexible product that can be used in many different applications. Silicone sealant can also withstand very high temperatures, making it ideal for applications that suffer high heat exposure,

Q.4: What is RTV?

One type of single-product silicone sealant is called Room Temperature Vulcanizing (RTV). This form of sealant starts to cure as soon as it is exposed to the air - or, more precisely, the moisture in the air. Therefore, it is necessary that you work quickly when using RTV silicone sealant.

Q.5: What is an acrylic sealant?

Acrylic sealant is a synthetic protective material used in a wide range of applications. It seals all types of materials to make them gap-free as well as resistant to infiltration from foreign matter. Variations of acrylic sealant are used extensively in the construction industry on residential and commercial properties. The drying or curing time for acrylic sealant varies according to the humidity and temperature of the location. When fully cured, flexible sealant then forms an elastic, rubbery coating over building surfaces and gaps. In addition to building joints, rubber-like sealant is used around windows and doors as well as to seal foundation cracks. Gaps in building siding can also be sealed with acrylic flexible sealants.

Q.6: What is polyurethane sealant?

Manufactured through the reaction of glycol and an isocyanate, polyurethane is an organic compound with particularly good moisture- and corrosion-resistance characteristics. Thus, polyurethane sealant is useful in both industrial and commercial applications. Additionally, polyurethane is often used as a heavy-duty adhesive, as well as a coating. A polyurethane sealant may be pressed, layered, sprayed, or brushed onto joints. However, the most common method of application is with a caulk gun.

Q.7: What is Gasket sealant?

There are many applications for mechanical joints, which are often used in liquid and vapor systems that operate under temperature and pressure. Generally, these joints are not absolutely tight and there is a limit to how well one will seal. A gasket is often used for joints that must seal tightly to prevent leaking and maintain operating performance. Gasket sealant is a material that is used, alone or in combination with a gasket, to prevent the escape of a liquid or a gas. Gasket sealant usually comes in a tube and has a paste-like consistency when applied. Sealant materials are available in foam, rubber, silicone, plastic, and metallic-based forms. Gasket sealant is frequently used for automotive repair. A head gasket is used to seal the engine block and cylinder head in an automobile engine. The head gasket is a flat, semi-rigid, graphite material cut to the shape of the two mating surfaces. A sealant is often applied to both sides of the head gasket to ensure that the small surface irregularities in each mating surface are filled, and that the two surfaces seal properly when joined together.

Q.8: What is an open time?

The maximum amount of time that an applied adhesive can be exposed to air before joining the both substrates.

Q.9: Which silicone should I use to seal PVC windows?

For PVC it is always necessary to use neutral silicones, the adhesion of an acetic silicone is not ideal on PVC.

Q.10: When do you need primer on a porous substrate?

If there is a possibility that the surface gets wet, the use of primer is necessary. In that case you get a better adhesion and protect the sealing against the water pressure that can appear.

Q.11: What is the good joint dimension?

This depends on the type of sealant:
•  For elastic sealants:
   Depth = 1/2 of the width of the joint
•  For plastic sealants:
   Depth = width of the joint

Q.12: What is the cure time of a silicone?

The cure time depends on:
•  Thickness of the joint
•  Humidity
•  Temperature
•  Surface
At normal conditions (20°C and 60% RH) a sealant will cure 2-3 mm in 24 hours. In the beginning it goes a little bit faster, after some days it goes a little bit slower.

Q.13: What is the difference between a low and a high modulus sealant?

This is related to the E-modulus, which is the force you need to stretch the
sealant by 100%.
If you need more than 0.4 N/mm² it is a high modulus.
If you need less than 0.4 N/mm² it is a low modulus.
Low modulus sealants are weaker and more flexible.
High modulus sealants are stronger and less flexible.
You can only define a E-mod for an elastic sealant (silicone, PU, MS) and not for a plastic sealant (acrylic, ...)

Q.14: Does the outside environment affect silicone?

No. Silicone is not affected by extremes of weather - hot, cold, dry, wet or humid. It also has excellent resistance to UV and ozone  degradation.

Q.15: How do I store open cartridge of sealant?

There is no data available on the shelf life of a sealant after it has been opened. Opened cartridges of sealant should be stored in a cool, dry place. Before storing, purge a small amount of sealant so fresh silicone will be at the tip of the nozzle. Replace the cap, quickly wrap duct tape around the tip, or put a nail down the nozzle and wrap tape over it.

Q.16: What sealant to use for sealing air ducts?

It is very important to seal air ducts since they cause pressure losses and they are the main reason for contamination in a building. Most air ducts are made of galvanized steel or aluminium or aluminated textiles. Because of the steel, we need a neutral curing product. That is why a neutral silicone gives you the best solution for this application.

Q.17: What is a primer?

Primers can be composed of any number of chemical compounds but in the end they can be thought of as a chemical bridge between an adhesive or sealant and the bonding substrate. This chemical bridge can be likened to a weld between two sections of metal. Most primers are specially designed molecules carried in a solvent vehicle. Once applied the solvent must evaporate and in some cases the active ingredients must undergo a chemical reaction. The time necessary for these processes to take place differs from one primer to another. It is important to consult the technical data sheet for proper drying times before applying sealant to primed surfaces to ensure a long lasting quality seal.

Q.18: Should I prime before applying sealant?

The ideal answer to this question is that primer should be used whenever cohesive failure is not achieved in the absence of primer. Of course this is assuming that sealant applicators conduct field adhesion testing. Or that all construction projects take advantage of adhesion testing services offered by most sealant manufacturers.

Q.19:  What is the effect of temperature variation on application of a typical sealant?

Generally speaking, a sealant will increase in viscosity, that is, get thicker as the temperature decreases. When temperatures dip below 5°C the workability and application of a sealant can become difficult to impossible. Once the sealant is in the joint and temperatures are low the curing of the sealant can be substantially prolonged. When applying sealants at low temperatures, provisions should be made for the extra curing time necessary to form a fully cured elastomeric seal. At warmer temperatures, the opposite is true, that is, a sealant will drop in viscosity or get thinner at higher temperatures. Most sealants will also cure faster at higher temperatures. The optimum temperature range for sealant application is 10°C to 25°C.

Q.20: What is the effect of humidity on a typical one component sealant?

Humidity is generally only a factor when applying one-component moisture cure sealant. The effect of humidity can be summed up as follows. The higher the % relative humidity the faster the sealant will from a skin and ultimately cure through. And of course at lower humidity levels, the skinning process and ultimate curing will be extended. Low humidity levels are characterized as below 30% relative humidity and high humidity levels as above 70% relative humidity. The effects of temperature as explained above must also be considered when applying a one-component sealant. The higher the temperature and humidity, the faster the skinning and ultimate cure.

Q.21: What is an Accelerated Ageing Test?

An Accelerated Ageing Test is a short term test to simulate the effects of longer term service conditions.

Q.22: What is an adhesion promoter?

An adhesion promoter is a substance used in small proportions to increase the adhesion to specific substrates. McCoy Soudal Surface Activator is a liquid adhesion promoter which is applied with a cloth or tissue. After the evaporation of the solvent, the sealant can be applied within 4 hours.

Q.23: What is Adhesive Tensile Strength?

This is the force per surface unit (N/mm²) required to bring an adhesive joint to the point of failure by means of an essentially uniform stress at right angles to the bond line.

Q.24: What silicone should I use in a bathroom?

TIn general, you can use a sanitary silicone of acetic type. Depending on the substrates you need to use a neutral silicone. In case of acrylics, polyester or most other plastics as well as aluminium or steel substrates, you will need a neutral sanitary silicone. In case of an enamel, wood, stone or glass substrate, an acetic sanitary silicone can be used.

Q.25: What is an ideal storage temperature?

The ideal storage temperature for all most of general type sealants, adhesives and PU foam is 5°C to 25°C.

Q.26: What is an ideal application temperature?

The ideal application temperature for all most of general type of sealants are 10°C to 35°C

 

Adhesive FAQ

Q.1:  What is adhesive?

An adhesive is a non metallic substance which is capable, after changing from a liquid into a solid state, to bond materials together by means of adhesive and cohesive forces.

Q.2:  Why sealant differs from adhesive?

The main difference between adhesives and sealants is that sealants typically have lower strength and higher elongation than do adhesives. Since the main objective of a sealant is to seal assemblies and joints, sealants need to have sufficient adhesion to the substrates and resistance to environmental conditions to remain bonded over the required life of the assembly. When sealants are used between substrates having different thermal coefficients of expansion or differing elongation under stress, they need to have adequate flexibility and elongation. Sealants generally contain inert filler material and are usually formulated with an elastomer to give the required flexibility and elongation. They usually have a paste consistency to allow filling of gaps between substrates. Low shrinkage after application is often required. Many adhesive technologies can be formulated into sealants.

Q.3:  What is an ideal storage temperature?

The ideal storage temperature for all most of general type sealants, adhesives and PU foam is 5°C to 25°C.

Q.4:  What is an ideal application temperature?

The ideal application temperature for all most of general type of sealants are 10°C to 35°C.

Q.5:  What is an open time?

The maximum amount of time that an applied adhesive can be exposed to air before joining the both substrates.

Q.6:  What is an Accelerated Ageing Test?

An Accelerated Ageing Test is a short term test to simulate the effects of longer term service conditions.

Q.7: What is an adhesion promoter?

An adhesion promoter is a substance used in small proportions to increase the adhesion to specific substrates. McCoy Soudal Surface Activator is a liquid adhesion promoter which is applied with a cloth or tissue. After the evaporation of the solvent, the sealant can be applied within 4 hours.

Q.8: What is Adhesive Tensile Strength?

This is the force per surface unit (N/mm²) required to bring an adhesive joint to the point of failure by means of an essentially uniform stress at right angles to the bond line.

 

Foam FAQ

Q.1: What is an ideal storage temperature?

The ideal storage temperature for all most of general type sealants, adhesives and PU foam is 5°C to 25°C.

Q.2: What is an ideal application temperature?

The ideal application temperature for all most of general type of sealants are 10°C to 35°C.

Q.3: Is it necessary to moisten the surface before using foam?

TWe recommend moistening because the system needs water to cure.
Other benefits you will get:
•  Better cell structure
•  Better adhesion
•  Faster curing
•  General better foam quality
If you do not moisten the surface, there is a risk of post-expansion, what means that the foam will harden out in the first few days. After a while the uncured foam will react with moisture and you'll get post-expansion. 2K-foam is an exception. 2K-foam will harden out without water because the second component (hardener) will enable the reaction.

Q.4: Is foam resistant to water?

Cured foam provides a barrier to moisture. However, over time, small quantities (depending of skin is on the foam) of water vapor will migrate through the foam. If the skin stays on the foam, the weight will only increase by 5%. If the skin is cut away, the weight can increase upto 150%. In that case foam is not water resistant. The water vapour permeability depends on the density and the cell structure of the foam. If you got more open cell structure or a lower density the permeability will increase.

Q.5: Does PU-foam provide good adhesion to all building surfaces?

Generally yes. 1K , Gun and 2K PU-foams have a good adhesion on the most common building materials, such as brick, concrete, plaster, wood, glass, metal, PS, rigid PVC and PU.
Exception: PE, PP and Teflon.

Q.6: What are McCoy Soudal PU-foams used for?

PU-foam is a multi-functional material which can be used for many applications:
•  Mounting door frames and windows
•  Insulation
•  Soundproofing
•  Filling gaps

Q.7: Is PU-foam UV resistant?

All PU-foams are not UV resistant. Normally PU-foam is covered, if not, it is necessary to protect the foam (e.g. by painting). If PU-foam is in contact with UV-rays for a longer period, foam will get discolored from yellow to brown. Later on the foam will get even brittle.

Q.8: What are the health and safety recommendations for using foam?

•  Apply the usual industrial hygiene measures
•  Wear gloves and safety glasses
•  Never burn hardened foam away
•  Consult the safety information on the label

Q.9: Why should I store a can with valve pointed upwards?

The valve has a rubber which is going from outside to the inside of the can. A rubber is a not 100% waterseal. The water, which is slowly going through it, can react with the isocyanate in the can and this could block the valve.

Q.10: What is the expansion of PU foam?

•  he expansion is different for gun and hand-held foam.
•  Hand-held foam will expand by 150-200% which means that you only have to fill the
    joint by 40-50%.
•  Gun foam will only expand by 50-100%, so you have to fill the joint by at least 50%. 


The expansion depends on the temperature of the ambience, temperature of the can and the humidity.

Q.11: How should I store an opened can of gun foam?

The best thing you can do is leave the can on the gun. If you do not leave the can on the gun, clean the valve and the gun with Gun & Foam cleaner. We recommend to empty the can in the next weeks.

Q.12: What sort of paint should I use for covering urethane foam?

Typically, PU-foam is covered by interior or exterior wall coverings or ceiling or roofing details. That said, on occasions it is left exposed and the concern really is only that of ultra-violet light that will degrade the exposed foam over time. In exterior applications, a paint will not suffice, rather a protective coating should be used. Very often a putty or sealant is used to cover and a paint is put on top.

Q.13:  Is there a negative effect on the foam if can is not shaken thoroughly prior to use?

Polyurethane foam consists of a prepolymer and a propellant gas, which form two layers during storage. The can must be shaken vigorously before use to create a homogeneous mixture. Insufficient shaking will result in poor foam properties such as a coarse cell structure and reduced foam volumes.

Q.14: How much must the cans be shaken to ensure a homogeneous mix of the two constituents?

A canister should be shaken 15 to 20 times.

Q.15: Does the canister need to be shaken again during use?

It is recommended to shake the can occasionally during use, and especially after interruptions, to avoid re-separation of the propellant and prepolymer.

Q.16: How does the foam get the right amount of moisture?

Fresh foam absorbs moisture from its surroundings. In particularly dry environments it makes sense to wet the surfaces to be joined. But standing water droplets are to be avoided, as in this case the water would actually become a barrier to proper adhesion.

Q.17: What happens when there is insufficient moisture on the surfaces or in the surrounding environment and no water has been sprayed onto the foam?

A lack of moisture leads to inefficient curing of the foam and, depending on the amount of foam applied, may lead to foam compression - even months later.

Q.18: Some polyurethane foam was spilt on unprotected window frames during application. Despite removing the spillage with cleaning fluid,the uPVC frame started to turn brown several months later - why was this?

You did not manage to remove all the spillage from the uPVC surface; a thin, almost invisible film has been left. Over the course of time this film has turned brown under the action of UV light; to which polyurethane foam is not resistant.

Q.19: What is the scientific basis of one-component polyurethane foam?

The chemical base is a prepolymer produced from Polyols, Isocyanate and various additives.

Q.20: Does the foam develop and exert pressure during expansion & curing?

Yes, the foam exerts a pressure during expansion and through hardening. It is therefore advisable to fill gaps and cavities by no more than one third.

Q.21: Is there any way to accelerate the curing process?

Yes, wetting; ideally from a spray gun. This will help to speed up the hardening process.

Q.22: How can foam spots be removed?

Fresh foam can be removed with PU cleaner. Cured foam can only be removed mechanically or by using special hard foam cleaner.

Q.23: Is cured foam subject to ageing?

Cured foam does not age. There has never been a case during the thirty years that polyurethane foam has been in use that any failure has occurred through ageing.

Q.24: What should I do with excess foam such as that round doors and windows?

Cured excess foam can be cut away with a knife, saw or any similar implement.

Q.25: Can polyurethane foam be used to fill profiles such as aluminium, steel or uPVC section?

Filling such profiles is not recommended, because the necessary curing moisture cannot generally be delivered along the entire length of the profile. A two-component foam is better for such applications.

Q.26: Can gaps between polystyrene insulation panels be filled with one - component polyurethane?

Yes, one-component polyurethane foam can be freely used for such applications. It is free from solvents and does not attack polystyrene.

Q.27: Is it OK to leave half-empty canisters attached to applicator guns?

Yes; in fact we recommend leaving a partially-full container attached to the gun. To store the gun and canister safely, the security screw should be tightened to secure the trigger.

Q.28: Why does foam spurt out sideways when the canister is re-used?

In such cases cured foam has partially blocked the nozzle, pushing newly-expelled foam to one side. We recommend cleaning fresh foam from the nozzle from time to time, especially if work is interrupted for any period.

Q.29: Is it necessary to remove excess foam from the adapter, or can I simply insert the next canister?

Though the adapters are constructed from a non-stick material, it is advisable to remove any excess foam straight away with gun cleaning fluid: well-maintained tools last longer.

Q.30: How long can a partially used container be left attached to a gun?

If the trigger has been completely secured with the security screw, a canister can be stored attached to the gun for a period of one to two weeks.

Q.31: Are there any special conditions to be observed during polyurethane
foam canister storage?

This is the force per surface unit (N/mm²) required to bring an adhesive joint to the point of failure by means of an essentially uniform stress at right angles to the bond line.

Q.32: Can a polyurethane cylinder which has been properly stored and temperature-maintained explode?

No, under no circumstances can a correctly stored, temperature-controlled, properly used PU foam canister explode. PU foam canisters are produced and tested to exacting industrial standards.

Q.33: What is the problem when no foam is released when a can is re-used?

Generally, cured foam residues which should have been removed have blocked the vent outlet.

Q.34: What happens when polyurethane canisters are stored for a protracted period in cold conditions?

The viscosity [flow resistance] of the foam will increase significantly, making the material flow more slowly. The canisters should therefore be brought to the proper temperature before use.

Q.35: Are there any special safety requirements for storing polyurethane foam canisters?

Yes, there are important considerations in the storage of aerosol cans in general and polyurethane foam canisters in particular. Each individual canister has information on safe storage printed on the label.

Q.36: Is it true that polyurethane foam in a canister has a limited shelf life?

Yes, because of a chemical reaction between the contents of the canister, a typical shelf life ranges from 9 to 18 months, depending on the product.

Q.37: Is the shelf life of PU foam influenced by external conditions?

Pronounced shortening of the shelf life will occur if the polyurethane foam is

subject to storage in warm surroundings over a prolonged period.

Q.38: Does the propellant gas have an effect on the ozone layer?

The propellant mixture is totally free from CFC's and HCFC fluorinated hydrocarbons. The products contain no ozone-damaging materials and conform to the requirements of EU-Directive (EC) Nr. 842/2006 on fluorinated propellants.

Q.39: How does the viscosity of the polyurethane influence the output of released foam?

The higher the viscosity of the prepolymer of polyurethane products, the slower will be the flow or fluidity. A viscous product has a lower rate of expansion. So the output from an older, more viscous prepolymer falls off; whereas the cell structure of the cured foam becomes correspondingly finer.

Q.40: What is the recommended optimum temperature for using polyurethane foam?

The best results are obtained when the operating ambient is between +15 and +25 °C.