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Silicones

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Jose Sanchez Marquez

on 28 March 2013

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Transcript of Silicones

, as an
important Building Material Silicone by Jose Sanchez Marquez Why we use it ? To separate the inside of buildings from the outside
To conserve energy by insulating walls and
To stop air leaks. How It Look Like? Silicone products Compared with others sealants, why Silicone is better? Some research examples about basic sealants properties Elastic recovery test Using samples of size 35x5x2 (mm) after 14 days of curing under standard conditions, they simulated weather conditions immersing the samples in water (25-30°C), hot water (70 °C), in the oven at 70 °C and QUV conditions- 4h UV (70°C); 4 h condensation (5O°C) by Chew et al (1997) the silicone is the one that presented the smallest changes on elastic recovery under different weather conditions and - is suitable for moving joints and harsh weather conditions and it is aesthetically acceptable [2]. Different results presented during the study Curing test by Chew et al (1997) the samples were cast in moulds of 300x100x15 mm and cured statically under standards conditions at 26+/-2°C and relative humidity of 65+/-5% It was observed that for one-part polysulphide materials the average fully cures were reached after 85 days and for the polyurethane materials fully cure were reached after 7days. Instead, the silicone after just one day (100%) of elastic recovery was reached indicating high resistance against stress during curing [3] for two-part systems (polysulphide and polyurethane) after one day of curing values around (98 - 100%) of elastic recovery was reached [3]. In practice the one-part silicone and the two-part polysulphide and polyurethane are ideal for rapid installations Curing test Moisture Influence High humidity and excessive water are two of the most important conditions that affect sealant durability in building joints, all because - chemical and physical changes near the substrate-sealant interface, arising from the penetration of moisture into the joint, affect the adherence between the sealant and the cement mortar (CM) or glass-reinforced concrete (GRC) [4]. Moisture test Aubrey et al [4] developed a testing method using concrete blocks of 50x50x5 mm prepared with Portland cement and cured for 28 days by Aubrey et al (1989) Test Results The joints were immersed in water at (20 - 25°C) for several days (14, 24 and 46 days), and dried to the ambient for (6-16 days) at (20 - 35°C) [4 At the end of the study it was observed that, the one-part silicone was the only sealant that for short and long time did not absorb a significant amount of water and the modulus did not change. For the rest of the sealants a reduction on their modulus was detected suggesting that - water weakened the joint by reducing the tear strength. Fatigue test by Wolf et al (1999) The samples dimensions were 12x12x5 mm, every specimen was cured under standard conditions for a range of hours or days (1/2, 2, 4, 8, 24, 7 and 30 days). A cyclic movement was induced in extension only at movement amplitudes of 10%, 25% and 50 % of the joint width, and then a cyclic of loading was also induced at a frequency of 10 cycles per minute. A maximum of 100.000 cycles (10 days) was allowed for each specimen on every frame material (aluminum, PVC and wood) [5]. Test Results The low modulus silicone showed the best response to high movements with a short cure period (less than 1) and in just 7 hours was capable to reach a maximum of 100.000 cycles with the aluminum frame, indicating a strong failure resistance compare with the high, latex and polyurethane materials or what it means, a more durable window seal [5]. What is a good Sealant? A good sealant is the one who develop a high degree of adhesion to the substrate surfaces or primer layer.
it’s necessary to have two situations, Absence of contamination (dust) at the interfaces. Good molecular attraction between the sealant and the substrate surfaces Is possible to say now that, compare with others sealants, Silicone exhibit better properties and performances than Polyurethane or Polysulphide Weather Seal
Expansion and control joints in buildings and facades
Window and door perimeters
Smoke and fire control
Architectural wall coatings Glazing
Waterproof sealant for joints, perimeters, and openings
Frame joinery http://www.siliconeforbuilding.com/Specialty/silicone-SCS1200Construction In the market is possible to find different types of Silicone products. Table shows average values of the most important differences between them. What is structural silicone glazing? Is only bonded to the glass on just TWO sides due to, transfer easily all the stresses to the frame.

Family includes one- and two-part structural silicone sealants and adhesives. Typically used;
Facade glazing
Curtain wall and window wall Cladding applications
Blast and hurricane mitigating protective designs Is basically, the adherence between the surface glass or other materials, to a framing system such as anodized aluminum, painted metal or certain stones using a specifically formulated structural silicone sealant as both an adhesive and a sealant However, Any sealant can fail for the same reasons,
user’s lack of knowledge of sealant properties;
usage of unsuitable sealant material for a given substrate and conditions; improper workmanship;
improper sealant dimension;
quality control of sealant [2],
but in many cases, failures are believed to be associated with chemical or physical changes near the substrate-sealant interface, arising from the penetration of moisture into the joint [3]. In fact, field studies indicate that 50 percent of building sealants fail within 10 years, and 95 percent fail within 20 years [1]. The SSG Advantages The aesthetic appeal, the ability to connect the inside with the outside environment,
No need to use mechanical fasteners such as screws, bolts or clamps the SSG can provide a full glass facade without protuberances picking up less dirt,
Reducing energy consumption inside buildings especially on corridors, hallways, atriums, etc. leading to energy-efficient buildings.
Aids to decrease the Heat island effect in urban areas due to the sunlight reflection of the glass, helping to reduce the city temperature [10]. http://www.wwglass.com/ The best way to reach full cure is under standards conditions, (relative humidity of 50 ±5% at an air temperature of 23 of ±1°C),
The average products can attain - a cured thickness of 3-4 mm per 24 hours if the material have access to atmospheric moisture (open spaces), otherwise in confined spaces with limited access to atmospheric moisture will cure only from that surface which has access to the atmosphere [13].
Finally, is important to remind that, as temperature decreases, the cure rate slows down (and vice versa) [13]. Most of the structural silicone manufactory companies emphasize that, Merci, Thank You.
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