Silicone adhesive for use
Why are there multiple types of sealant ?
You can use three steps to ensure that the sealant reaches its optimum design life. First, according to experience to design glue seam , and then determine the sealant performance to be achieved , and finally select an appropriate sealant to meet these properties. The information on these functions through the introduction, you can help to correct the appropriate sealant.
Correct selection of one kind of sealant, glue seam must consider the function of glue seam substrate contact with the environment and glue seam sealant to achieve required mechanical properties . Caulk sealant two main function is to provide weather sealing and structural sealing , so asked to consider the glue seam sealant movement capability , tensile strength and hardness , but must also consider the following criteria : temperature range , chemical media , UV irradiation and project life cycle. Substrate side, it must consider glue adhesion and compatibility, including support rods and double-sided tape and other auxiliary materials .
02 sealant glue seam design
The best glue seam sealant should be uniformly filled cracks in the gel , and with both sides of the substrates have a better bonding. Sealing adhesive bonding performance is not good cause glue seam failure , glue seam sealant will lead to unreasonable design cracking , poor environment and climate will cause hardening and cracking sealant . Silicone sealant composition due to its inorganic chemistry , than other sealants have better UV aging resistance capability , it has a particularly long life.
03 support rods
Glue seam must have a bottom , which can ensure that the sealant can better fill glue seam , with the sides of the substrate with sufficient contact , and the glue seam to maintain the correct shape. In most weather sealing applications, we recommend the use of closed-cell polyethylene support rod, sealant and polyethylene sticky, thus avoiding the formation of three-sided adhesion . Support rod contains air , to ensure that no deformation when sizing adhesive seam slippage does not ; same time, it is not entrained water. When pressed into the support rod to be sharp with no facility to operate so as not to pierce the surface and it will release the air inside , so easily lead sealant bubbling destruction. Support rod diameter than the plastic slot width to be 25% to 50%. Other types of support rods are open-cell foam , this material can be entrained moisture like a sponge leaving sealant solidified ; And when the elastic sealant curing presence of water vapor is bad, when it is injected with lead seal sealant increased use of plastic , changing the shape of strips , affecting full contact with the substrate adhesive , causing the adhesive to fail.
04 three-sided adhesive
Mosaic panels on three sides bonded structures are very common , such as aluminum hybrid structure , GRC frame structure. With the glue seam shift changes , sealants change shape ( intermediate becomes concave shape) , but the volume does not change . Therefore, they must be able to move in the rubber cracks , but they also must have good adhesion to the substrate remain . Figure 1 shows the three sides adhesive sealant will reduce the ability to change shape , thus leading to increased pressure on the sealant , sealant caused by the fracture . Three sides of the adhesive sealant will prevent the glue seam from the third slide surface , the displacement of such a request in all the glue seam between the two substrate surface between the bottom and the third generation , through the use of a suitable disconnect the adhesive tape , sealant produced only two sides of the seam adhesive , sealant so that when affected by external changes shape , and can be kept in a patchwork sliding groove shape .
05 weather sealing
When the sealant applied two or more frame-shaped structure when caulking , weather seal appeared. Sealant is required to produce an adhesive frame structure , frame structure when moving the movable surface sealant on the seams provide displacement and deformation , while preventing heat , dust, moisture and bacteria through the sealant is not fixed on the frame structure from the structure function .
06 joint displacement
Produce joint displacement due to:
1 , with the temperature ( thermal motion )
2 , with the change of water content
3 , building load ( high-rise buildings to increase floor caused by compression, or a change in existing buildings furniture )
4 , architectural treatment
5 , environmental forces ( wind , earthquakes, etc. )
Sealant must be able to change with the patchwork , and provide corresponding displacement deformation. Typically cycling displacement and deformation , such as the temperature of thermal motion with lift generated daily , and with alternating hot and cold seasons per year arising from a large circle.
07 sealant strip width
According to the following calculation to determine the minimum width of the glue seam . Generally speaking , the elastic sealant caulking width can not be less than 6mm, is not greater than 30mm, glue seam too difficult to trim the plastic surface . Sizing thickness not less than 6mm, and generally half the width ( eg : 12mm wide take 6mm deep ) , however, usually do not require sizing thickness greater than 10mm ( eg 25mm wide 10mm deep gum glue seam thickness taken , is enough to meet the requirements ) . Sealant glue sealant width control to provide the maximum displacement capacity, but will not produce sealant fracture. Wider joints require greater displacement capacity . Therefore, we must calculate the total displacement of the joint and then to determine the optimum sizing of the width of the seam . Heat displacement resulting from changes easy to calculate ; but shall calculate the other forms of displacement and deformation , and then derive the joint width .
08 joint displacement calculation
Use the following formula to calculate the deformation of the substrate may occur :
M = (MT-T) × S × L
Wherein: M represents a substrate deformation mm.
MT represents the maximum possible substrate temperature ℃, containing cited by radiation, temperature and elevated temperatures . Such as the temperature 40 ℃, black aluminum surface temperature may reach above 80 ℃ . T represents the substrate surface may reach a minimum temperature ℃, including temperature changes caused by the wind . S represents the thermal expansion coefficient of the substrate , below the typical coefficient of expansion material . L represents the length of the substrate m.
There are two seams displacement cycle , day and night temperature changes resulting diurnal cycle and the winter and summer temperature changes resulting annual cycle . Sealants after so many years still requires the ability to meet these displacements cycling without losing its elasticity , while displacement to meet these requirements , as required to satisfy the maximum possible and the minimum displacement , required to calculate the actual sealant joint dimensions .
09 joint width
Displacement of the substrate may be calculated after deformation , we can calculate the size of the smallest seams , calculated as follows:
W = (100 × M) × S%%%
Where : W means the minimum joint width mm.
M represents the maximum possible joint displacement .
S indicates the permissible sealant displacement and deformation , expressed as a percentage , by providing product index .
According to the substrate deformation range calculated in advance the maximum possible displacement of the joint , if the base expansion joints becomes smaller , the joint will be compressed ; if the substrate contraction becomes large glue seam . Displacement and deformation around the joints sometimes tend to be different, such as mechanically fixed at the bottom of the bottom of the vertical plate will not move , then the thermal deformation of the substrate causes the deformed upward . In ( Figure II ) being supported at the bottom of the substrate , and the Y-axis direction so that all relevant shape effects . Although the deformation displacement in the X- axis direction each 50 %, but in the base material A and B can be achieved between the displacement and deformation of 100%, B between the wall fixing , only 50% of the horizontal displacement , it is with the wall displacement deformation from moving in the horizontal direction . When each puzzle is not the same size they would need to consider the patchwork produce different displacement and deformation ; such as the patchwork of different materials on both sides , such as glass and aluminum curtain wall , you need to calculate their joint deformation of the displacement generated . Each of the different deformation results in the deformation of the joint displacement . Displacement and deformation may also be caused by other reasons , such as buildings or moving device fixed tilt suspension , or when added to the structure will form a floor . Porous materials such as concrete and masonry due to different moisture expansion and shrinking. All of this change on the deformation of the joint should be considered . Typically, the construction should also be considered at different times would produce a certain bias. Construction of thermal expansion of the substrate summer , joints become smaller , sealants working life has been extended ; during the winter glue seam will be wider, plastic working life will be shortened . Only the above formula to calculate the minimum width of the glue seam sealing adhesive performance and the substrate will affect the actual use of the joint width. We require a width not less than 6mm. There is also a maximum joint width . Swelling sealant , glue and curing time of the sealing adhesive has limitations. For silicone rubber , the maximum joint width 40 ~ 50mm.
10 depth of sealant tape / glue seam depth
The whole rationale for the application of the substrate and the sealing performance will affect the optimal depth glue seam
11 weather sealing
Typically, the glue seam depth of half the width . If the depth is too large, joint deformation increases , sealants prone to uneven surface displacement phenomenon , leading to excessive pressure deformation caused by adhesion failure . If the glue seam depth is too small, the glue less than normal, having regard to stress concentration or the formation of bubbles caused by cracking, and even lead to adhesion failure . Solvent-based sealant ( such as butyl rubber ) also increased by virtue agent losses caused by shrinkage cracking . Therefore, the weather rubber deeper than 12mm. Width of not less than 6mm.
12 structural sealant
Structural adhesive only bearing support structure , and must withstand the deformation displacement of the structure , therefore , a sufficient amount of structural adhesive to make full contact with the substrate is exposed to the weight of structural units . Structure to provide structural strength bonding site part sealant. It is when the aluminum plate by the external force in a certain range of expansion and contraction of the right angle to the bottom of that portion of the adhesive sealant.
This part of the calculation formula of the sealant is as follows:
W = ((D × 5) × P) / S
Where : W means structural bonding width m. D represents the minimum edge width aluminum m.
P denotes the glass can withstand the maximum pressure Kpa. S represents sealant allows maximum pressure to bear Kpa.
13 sealant sustained capacity
The calculation formula is discontinuous sealant capacity, such as glass , and the glass is subjected to the aquarium is continuous bearing pressure , there are various other formulas .
14 the shape of the sealant
Then the best sealant should be square or rectangular shape . When Substrates displacement , the conical surface of the substrate with three or more face set pressure , the narrow edge of the glue joints cause bonding failure .
15 adhesive function / weather sealing
Some non- silicone sealant over time , exposure to the natural environment suffered UV rays , the hardness will increase . Therefore, careful consideration needs to choose a stable quality sealant. Fill in the substrate to be weather resistant sealant that will withstand wind, rain, and dust and other natural factors against. Therefore , the substrate with the sealant to be able to change the size and displacement , with good stretchability , and associated parts can be fully adhered .
16 structural sealant
Structural adhesive generally used for structural glazing bonding between the components , while the tensile strength and resolve suffered stress. Therefore, it requires a degree equivalent mechanical structural strength requirements of the standard , with the said modulus and tensile strength , the greater the value , the greater the strength of the product . Structural adhesive not sustained over time , resulting in adhesion between the substrate structure and the performance deteriorated. Common structural assembly , such as glass structure assembly , aquarium, mirror installation.
Mechanical properties 17 / displacement capability : the ability of the dynamic displacement of the cured sealant that a technical indicator , when the actual operation of the adhesion value of the width of the design draft inconsistent, is usually the maximum value .
18 Tensile strength: good adhesion to the substrate is the case of fracture of the product can withstand the maximum power.
19 Hardness: Shore hardness we represent . High hardness can reduce the soft sealant sealant brought extrusion and abrasion hazards. Softer sealants generally have greater flexibility , easy to produce suitable displacement glue seam area.
20 Environmental factors: the changing of the natural environment, the different types of the same kind of sealant or sealant will have a different reaction condition . Environmental factors affecting : ultraviolet radiation .
21 chemical reaction : temperature changes ( sealant application and adaptation range )
22 glue seam design life : Inferior for different products , please refer to the specific technical parameters