Sealants Standards

Many technical characteristics or test methods are similar for adhesives and sealants, for instance, viscosity, specific gravity, shear strength. But the test methods usually differ because sealants have different properties and different functions from adhesives sealants must usually fill a large gap (several mm), they must remain flexible and much softer in order to accept movements, while adhesives must provide a stronger and harder bond. 

In the present chapter, we will study aU the technical characteristics and test methods of adhesives, but only 20% of these characteristics and test methods 

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ISO sealant standards, 22 28, 46. See also International Standards Organization (ISO)... 

Specification for Elastomeric Joint Sealants Test Method of Compression Recovery of Tape Sealant Standard Test Method for Determination of Water Absorption of Sealant Backing (Joint Filler Material)... 

The issue is complicated by the parallel existence of aerospace committees within BSI, and in Europe within the Association Europeene des Constructeurs de Materiel Adrospatial (AECMA). This is the European organization responsible for standardization related to aerospace materials and, hence, covers many structural applications of adhesives, as well as aircraft sealants. Standards published by AECMA, like normal European standards, are required to be adopted by member states. 

Fire and product Acceptable resistant sealants standards... 

Typical specifications for the polysulfide polymers are summarized in Table 1. Specifications for the sealants vary widely depending on the specific apphcation and the needs of the appHcators. Standards for sealant testing vary in different countries. Ultimately, the tests should simulate the environment the sealants will be exposed to and measure their performance under these conditions. 

Although sealant manufacturer s Hterature commonly reports modulus values, these values must be interpreted carefully. Specimen sizes, test rate, cure conditions, and the time a sealant has been allowed to cure when tested can all have a significant effect on modulus. Therefore, for a tme comparison, sealants should be evaluated by a standard test that examines all sealants by the same procedure. In general, the longer a sealant has been allowed to cure, the more reaUstic the modulus data. 

Prior to May of 1998 when the commercial product was approved by the FDA in the United States, surgeons in this country formed fibrin sealant by using topical bovine thrombin, which is a commercially available product, together with concentrated fibrinogen most frequently obtained from the blood bank. Standard blood bank cryoprecipitate is a good source of concentrated fibrinogen. Also... 

Three different commercial formulations of silicone sealants from Dow Corning was used in the NSF sponsored studies. They were DC-790, DC-995, and DC-983, in the order of increasing modulus. Dumbbell test coupons (samples) were prepared as per the ASTM standards. Some test coupons were maintained at ambient conditions as control and the rest were subjected to simulated weathering. The weathered coupons were removed from the test layout at regular intervals of time and were tested for any changes in crosslink density due to exposure. 

Flame retardants cause the plastic material to be safer in use in its final form. They are only used when the marketplace requires it in a wide range of applications spanning the construction, moulded parts, sealants, coatings and textile industries. High levels (up to 25 %) of FR are required in polypropylene - one of the most difficult plastics to render flame retardant - to meet standards for certain applications, such as in the... 

Since then, uses have shifted more toward civilian applications. Polysulfides have unusually good resistance to solvents and to the environment and good low temperature properties. This makes them particularly useful in a variety of sealant applications. For example, the outstanding resistance of polysulfides to petroleum (qv) products has made them the standard sealant for virtually all aircraft integral fuel tanks and bodies. Another important application is in insulating glass window sealants (qv). Sealants based on liquid polysulfides have had an excellent record since the 1950s and are the worldwide market leader in this application. 

Acrylic latex sealants. Basic acrylic latex sealant formulations were compounded in a sigma blade mixer, as shown in Table 3. The water-borne silanes were then incorporated into a base. Standard wet and dry peel adhesion determinations from various substrates were performed periodically in accordance with ASTM C794-8. 

Crack and joint sealants are applied only on cracks and joints. Seal coats include hot asphalt-rubber sprayed on the surface followed by precoated aggregate. Interlayers are the application of seal coats followed by either a standard overlay or an asphaltic-rubber overlay. Asphalt-rubber, when blended with an aggregate hot mix at about 9 to 10 percent by weight, serves as a binder in the thin overlay applied to the road surface. The hot mix binder holds the greatest potential for using large quantities of scrap rubber because of the thickness and quantity of the overlay. 

A sealant, such as Apiezon W, is a good example of a material that was designed for an extremely limited application. Apiezon W is a hard black wax that needs to be heated to 80°-90°C before it is soft enough to apply to the members you wish to join. At room temperatures it is hard and has no lubrication abilities whatsoever and is therefore not usable for a stopcock. It has a relatively high vapor pressure (10 3 torr), so it cannot be used for most vacuum work. However, at temperatures of about 100° to 150°C, it becomes very thin like hot honey and can easily be applied to joint members. Therefore, if you have a standard taper joint that will not be in a high-heat or ultrahigh-vacuum environment, there is no need to separate often, and you don t want it to accidentally separate, Apiezon W is the type of sealant you need. 

Construction. Polymeric materials such as adhesives, sealants, and composites have been used considerably in the last several decades for the construction, repair, and rehabilitation of our transportation infrastructures. Even though most processes were experimental until recently, they have evolved to the point where many are now standardized and well accepted. Table 1.6 hsts several common applications for advanced polymeric materials (as well as the polymeric resins that are most commonly employed). In the construction or repair of roads and bridges, epoxy adhesives have primarily been used for bonding concrete and for bonding stiffening members or repair structures to degrading concrete facilities. 

An adhesive or sealant specification, like all material specifications, is a document that specifies values for all the important properties, together with limits of variability and methods for determining these values. There are many adhesives and sealant specifications, of which the most prominent are the industrial and government specifications. These describe and establish the technical and physical characteristics or performance requirements of adhesive materials. The most common sources of standards and specifications for the adhesives and sealants industry are the following ... 

Relevant ASTM specifications and standards are presented in App. G. A variety of federal and military specifications describing adhesives and test methods have been prepared. Selected government specifications are also described in App. G. Table 19.4 identifies several other sources of specifications for adhesives, sealants, and related equipment. 

Certain specifications and standards provide excellent tutorials on adhesives and sealants. For example, MIL-HDBK-691 offers a complete handbook on adhesive bonding, and MIL-HDBK-725 provides a guide to the properties and uses of adhesives. ASTM C 962 provides an excellent source of information regarding sealant joint design and the types of sealants that are appropriate for various substrates. Although this specification is primarily for construction sealants, much of the information that it contains is generally useful for other sealant applications. 

TABLE 19.4 Sources of Common Specifications and Standards for Adhesives and Sealants... 

A number of standard tests for adhesives and sealants have been specified by the American Society for Testing and Materials (ASTM) and other professional organizations such as the U.S. Department of Defense and the Society of Automotive Engineers. By far, ASTM standards are the most commonly referenced test methods. Selected ASTM standards are presented in App. G. The properties usually reported by suppliers of adhesives and displayed in the technical literature generally reference ASTM standards. 

The viscosity of nonflowable products is determined by an extrusion test. A Semco 440 nozzle or its equivalent is attached to a standard adhesive/sealant cartridge filled with the material to be tested. The cartridge is then placed in an air-operated sealant gun set for a pressure of 90 to 95 psi. The weight of material that is extruded in 10 s is measured, and the extrusion rate is reported in grams per minute (g/min). Care must be taken to clear trapped air from the cartridge and nozzle. 

It should be apparent by now that numerous parameters can affect the performance of a joint, and many combinations of those parameters are possible. Therefore, a prime rule in any adhesive or sealant testing program is to standardize and document test variables as thoroughly as possible. The adhesive formulator, supplier, and end user should all utilize the exact same procedures and specimen construction. One should make every effort to ensure that similar tests that are performed at different locations in the company and by different personnel are identical duplicates of one another. 

Standard Test Method for Determining Compatibility of Liquid Applied Sealants with Accessories Used in Structural Glazing Systems Determining Tensile Adhesion Properties of Structural Sealants Specification for Structural Silicone Sealants... 

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