What can cause silicone sealants to fail?

HP International Comes Out With Basic Guidelines

Strong Seal Silicone sealants are manufactured at the most state-of-the-art units with total control on the production in respect to quality parameters

There are more than five online production checks and further tests at the laboratory to ensure product performance and adherence to various specifications. HP International is looking forward to associate with channel partners who are like minded, quality conscious and financially stable in order to supply the market with a high quality product and service to match the best in the industry. Earlier, HP International had highlighted on the uses of silicone sealants and advantages of using Strong seal silicone sealants. Here, focus will be on the reasons for failure of sealants and corrective actions to be taken to ensure that failures do not happen. The main function of silicone sealant is to accommodate movement. This is more easily performed if the sealant does not have to also act as weather protection. When a sealant does form the joint’s sole weather protection, the spacing, location and sizing of the joint are even more crucial to the ultimate success of the seal.

Basic Guidelines for the proper application of a sealant

A. The substrate must be clean and dry for the sealant to adhere properly. All sealant manufacturers state this in their recommended application procedures. When this basic rule is violated, the most common of all adhesion problems begin. Some of the most basic clean deficiencies are: • Not cleaning at all • Using contaminated or dirty solvent • Using the wrong solvent for a particular sealant. • Allowing contaminated solvent to dry on the substrate • Using contaminated rags or brushes • Using a rag containing lint

B. Improper use of sealant. The second most common adhesion issue is caused by the improper use of primers. Though usage of primers are not required in most of the cases. • Not using the primer at all, when it is required to be used. • Using too much primer • Using the wrong primer for the specific sealant or substrate • Not allowing the primer to dry completely before adding the sealant

C. Weather on day of application. Temperature is the key. In most of the cases, a silicone application fails not due to the silicone being bad but, because of not understanding the right atmospheric conditions when it is applied. • Cold temperatures causes the sealant to lose viscosity which makes it difficult to apply without gaps and voids and it will be too thick to properly tool. Cold air may retard the cure and if the substrate has contracted due to the temperature then the joint will be wide open. Issues occur when the substrate warms up and expands, causing the joint to close and the sealant to be squeezed out entirely. • High temperatures can cause the sealant to sag or flow out of the join resulting in failure. Premature skinning over the sealant bead can also occur resulting in craze cracking. • Dry surfaces are imperative. Dew, frost or any sort of precipitation will guarantee adhesive failure. The same applies if the substrate is still damp from a previous rain or cleaning done with water.

D. Field applications that can go awry. • The most common is substitution of the specified product. Many sealants look alike, but they do not perform in the same way. Understanding what sealant is to be used, where and how should be clearly understood before using the product. • Improper storage can cause sealants to freeze, prematurely cure, or exceed their shelf life. Most cases the vendors may not store the sealants in a proper storing condition, thus making the sealant to dry from inside. HP International gives a product warranty for their shelf life, but the warranty will be valid only if the sealants are properly stored and are for any manufacturing defects.
E. Don’t paint your sealant! • Most paint will not adhere to your sealants and are not formulated nor intended to take the kind and amount of movement to which sealants are subjected. • If the paint does adhere it will crack when the joint moves.
• If the paint cracks so does the sealant. • If you need a paintable sealant, please use a Polyurethane sealant, MS Polymer or acrylic sealants. Please contact HP International sales team or technical team for details.
F. Joint surface detail. • The edges of the joint must be smooth and not jagged so the sealant doesn’t develop air pockets during installation. Very specifically this problem is noticed while weather sealing is done. Similarly, do not apply sealant when the application temperature is more than 45 deg C, as the sealant may develop air pockets/ bubbles.
• Any mortar must be removed or cohesive failure can result.
G. Importance of backer rods. • Backer rods create the proper depth to width ratio, act as a bond breaker, and provide a firm surface for tooling. • Failure to specify an appropriate bond breaker can cause big time problems • A joint with three sided adhesion will fail cohesively, adhesively or both. • Closed-cell backer rods should not be used with sealants that cure by reacting with moisture in the air. These rods must also be protected from puncturing to avoid outgassing. • Open cell backer rods should not be used where moisture absorption into the backer rods can be a problem. • Backer rods are held in place by compression therefore, the rod selection should be about 20% larger than the maximum expected joint opening. If it is too small it will not function as intended and proper tooling will be impossible.
H. Usage of bond breaker tape. • Bond breaker tape should be used only where there is a firm bottom surface and when the joint is so shallow that a backer rod will not fit.
• Tape sizing is very important. If it is too small, three sided adhesion will result, and if it is too large, the tape will wrap around the bottom and sides of the joint, eliminating some of the bonding area required for good adhesion.
I. Benefits of Tooling • Helps protect the weather tightness of the joint by eliminating air pockets created behind the sealant during gunning. • Forces sealant contact with the side of the joint promoting good adhesion. • Sealant is pushed against the backer rod and pressed into an hourglass shape allowing it to stretch properly. • Without tooling, the bond area between the sealant and the sides of the joint may not be sufficient to prevent the sealant from pulling away from the sides of the joint. HP International advises all users and applicators to understand a very important fact that the best set of specifications become useless if the joint sealant is not applied properly. HP International provides the best silicone sealant to cater to all needs of consumers. It is a continuous endeavour that the company’s R & D team and the production team work together to work out the best sealants that can perform to the toughest applications today as required in various sealing applications, be it in construction, general sealing, wood, aluminium, UPVC windows and doors, sanitary applications, solar panels, clean room applications, facades, curtain walls and any sort of cladding applications, concrete, stone and composite claddings. HP International introduces various sealants for a choice of applications:- Strong seal Acetoxy sealant for General purpose applications • 3600 GP Gold • 3400 GP Silver • 3200 GP Bronze • GP Fast • Glass & Aquarium • Strong seal Neutral sealants • N 7400 General purpose Neutral sealants • W 7800 Weather sealants Strong seal silicone sealants are available in most of the standard colours, and can be customised as per the requirements of customers for their various colour requirements too.