F.A QUESTIONS


Sealants
  • What is a sealant compression set ?

      Compression set concerns a sealant’s capability of returning to its original configuration following compression . In a working joint, a sealant with high compression set is undesirable, since continued expansion and contraction can be anticipated. Once a sealant with high set is compressed, the result is high internal and adhesive stress when the joint again expands,
      because the width of the sealant bead has been permanently reduced. If the stresses are great,
      there can be failure in the adhesive bond or cohesive failure in the sealant.

  • What is a sealant stress relation ?

      Stress Relation can occur when a sealant as poor elastic recovery and stress caused by expansion or contraction is reduced internally in the sealant after it has been deformed.
      Non-elastic, low modulus sealants tend to stay in this deformed condition and « pump » out of the joint or fail cohesively.

  • What is a sealant hardness ?

      There are different Shore Hardness scales for measuring the hardness of different materials. These scales were invented so that people can discuss these materials and have a common point of reference.

      The Shore A Hardness Scale measures the hardness of flexible sealants that range in hardness from very soft and flexible, to medium and somewhat flexible, to hard with almost no flexibility at all.

  • What is the elastic recovery ?

      Elastic recovery means return of the sealant to its original form while it is extended. A sealant with good elastic recovery maintains its original configuration even after repeated cyclic movement.

  • 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.

  • What is an Accelerated Ageing Test?

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

  • 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, ...)

  • 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.

  • What is an open time?

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

  • How good is the freeze-thaw stability of sealants during transport and storage?
      Generally, it is not recommended to store and transport sealants based on silicon and polyurethane below 0°C ; but it is possible for a while. Whereas Akfix All Seasons Acrylic Sealant and Akfix Allbond MS High Tack sealants have freeze-thaw stable property at tempratuers below 0°C. These kind of products exposed to cold should be waited at room temperature before application. They are usable after freeze and thaw.
  • When can newly-applied silicone sealants exposed to water first?

      The places with newly-applied silicone sealants can begin providing service after 1 to 3 days.

  • 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

      Using backer rod between section ofthe joints is recommendedto reduce consumption of sealant and for easy tooling. That also saves money.

  • What is an ideal application temperature?

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

  • 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. If the products are stored at a higher temprature, the shelf life will be reduced. If those are stored at a lower tempratures , there would be slower curing and harder application.

  • What is an ideal storage temperature?

      Humidity is generally only a factor when applying single 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 single component sealant. The higher the temperature and humidity, the faster the skinning and ultimate cure.

  • What is the effect of humidity on a typical single component sealant?

      Humidity is generally only a factor when applying single 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 single component sealant. The higher the temperature and humidity, the faster the skinning and ultimate cure.

  • What is the effect of temperature variation on the 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.

  • 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 manufacturesrs.

  • 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.

  • How can cured silicone be removed?

      By using carpet knife, the cured silicone is cut out and then the thin residue is removed using silicone remover.

  • Are there any precautions which have to be taken into account when sealing wooden construction elements?

      Preliminary tests are recommended before applying sealant on the whole areas of application of wood types such as oak, teak, parquet etc.

  • 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, water and ozone degradation. But if the joint sealed with silicone is exposed to chemical or physical damage it has to be renewed in order to avoid significant damages.

  • Which silicone sealant should I use for natural stone and vulnerable materials?

      Non-corrosive neutral sealants should be used for natural Stones and vulnerable subtrates such as neutral silicones, siliconized acrylic sealants and MS sealants.

  • What silicone should I use in a bathroom?

      In 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.

  • 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.

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