Adhesive sealant testing

A sealant s adhesion is commonly studied by 180 degree peel tests such as ASTM C794 or by tensHe/adhesion joints tests such as ASTM C719. The adhesion test protocol should simulate actual field conditions as closely as possible. Sealants often have good adhesion to dry substrates, but this adhesion may be quickly destroyed by water. Because most sealants are exposed to water over their lifetime, adhesion testing should include exposure to water for some length of time. ASTM C719 is one of the better tests to determine a sealant s adhesion durabHity as it exposes sealants to seven days of water immersion. 

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. 

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. 

Test Method for Adhesion in Peel of Elastomeric Joint Sealants Recommended Practice for Surface Preparation of Concrete for Application of Chemical Resistance Resin Monolithic Surfaces Method of Testing Release Papers Used with Preformed Tape Sealants Test Method for T-Peel Strength of Hot Applied Sealants Test Method for Tensile Adhesive Strength of Preformed Tape Sealants by Disk Method... 

The adhesion-in-peel test was used to determine peel strength and adhesion characteristics of a cured-in-place silicone elastomeric joint sealant on aluminium substrates. The sealant used was Dow Corning Type 3145 RTV Adhesive Sealant. The results showed that the silicone sealant had poor adhesive bonding to the untreated aluminium. Plasma polymerisation of hexamethyl-disiloxane(HMDS) onto the aluminium was shown to move the locus of adhesive failure to between the plasma film and the silicone. Plasma polymerisation of HMDS... 

Nordson Corp. is a leading global producer of precision dispensing equipment that applies adhesives, sealants, powder and liquid coatings, and other materials to a range of consumer and industrial products. In addition, the company manufactures equipment used in the test-... 

Test for adhesion after impact of preformed tape sealants Test for weight loss after heat aging of preformed sealing tapes... 

Test for effects of accelerated weathering on elastomeric joint sealants Test for adhesion-in-peel of elastomeric joint sealants... 

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. 

We will not describe the laboratory equipment and the detailed test methods that may be used for all the tests hereunder, because this will be done later in the chapter titled Methods of testing adhesives, sealants and their joints in Volume 7. 

Keywords Additives Aliphatic Aliphatic isocyanates Amine-isocyanate reaction Aromatic isocyanates Blocked isocyanates Chain extenders Construction (application in) Glass transition temperature Hydroxyl-isocyanate reactions Hot melt reactive PU Isocyanates MDl Moisture curing PU One-component PU Packaging (application in) Plastic and composites (application in) Polyester Polyether polyols Polyisocyanates Sealants Silane PU hybrids TDI Testing of PU adhesives testing of PU sealants Testing standards TPU thermoplastic PU Transportation (application in) Two-component PU Water-borne PU... 

Test for footwear and footwear materials. Measurement of green strength of adhesive joints Cold applied sealants test method for the determination of tack free time... 

This chapter gives a brief description of special mechanical tests for various types of material and sample geometries, such as blister tests, tensile tests, and shear tests for sealants/foam adhesives, indentation tests, scratch tests, tack tests, and tests for the evaluation of residual stresses. 

A sealant is a material that is installed into a gap or joint to prevent water, wind, dirt, or other contaminants from passing through the joint or gap. This joint or gap may be a fixed joint, but is often an expansion joint which may also be called a working joint. Sealants, which can also be defined by how they are tested, are rated by their ability to stretch, twist, bend, and be compressed while maintaining their bulk properties so that they do not tear apart under stress. A most important rating of a sealant in many applications is the movement ability of the sealant. The adhesion required of a sealant is simply the strength to hold the sealant in position as it is stressed and strained. 

Compatibility of TATB PBX with Weapons Materials , PlastOtherMaterExplosProplntsSymp, IIIA (1976) CA 87,87227 (1977) [Reported is the use of Viton-A, Kel-F 800 and Estane 5702-F1 as a binder for TATB contg expl compns. Compatibility tests (the object of the study with stainless steel, V, polyamide film and several sealant/adhesives at 120° for 1 to 4 months revealed no definite reaction. However, it was concluded that the major cause of gas evoln and chemical interaction between expl and test materials is the presence of w]... 

The formulator has the unenviable task of responding to the latest issues impacting the end users of adhesives and devising the technology and resources to come up with practical solutions. It may seem that as soon as a product is developed, tested, and commercialized, the demands change. This is, of course, not necessarily the fault of the end user. There are many outside influences that affect the end users processes, just as there are many influences affecting the type of raw materials and equipment that can be utilized for formulating adhesives and sealants. 

TABLE 15.2 ASTM Test Methods for Determining Environmental Resistance of Adhesives and Sealants... 

Metering. The components of multiple-part adhesive or sealant systems must be measured out carefully. The concentration ratios have a significant effect on the quality of the joint. Strength differences caused by varying the curing agent concentration are most noticeable when the joints are tested at elevated temperatures or after exposure to water or solvents. 

The Bonding Process. Before the actual assembly operation, the cleanliness of the shop and tools should be verified. The shop atmosphere should be controlled as closely as possible. Temperature in the range of 18 to 32°C and relative humidity from 20 to 65 percent are best for almost all bonding operations. All parts should be fitted together without adhesive or sealant to indicate possible production problems due to fit. The suitability of fit is established by either visual inspection or direct measurement with gauge or shim. It is desirable that the extremes in mechanical tolerances also be noted and that test specimens be made with the worst possible fit to ensure that the bonding process will always provide reliable joints. 

Bond Inspection. After the adhesive or sealant is cured, the joint area can be inspected to detect gross flaws or defects. This inspection procedure can be either destructive or nondestructive. The nondestructive type of tests can be visual or use advanced analytical tests. These types of bond inspections are described below. 

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. 

All the materials to be tested for shelf life are stored in unopened containers. Storage in containers that have been opened exposes the resin to oxygen and humidity that, depending on the type of resin, could drastically reduce the shelf life and affect final properties. Most polymeric adhesives and sealants and their components have a shelf life greater than 6 months at room temperature. However, some one-component adhesives need to be stored at refrigerated conditions to have a practical shelf life. 

ASTM D 1489 offers a test method for determining the nonvolatile content of aqueous adhesives. The solids content (or conversely the volatile content) is a measurement of the actual nonvolatile materials that are contained within the formulation. Addition of solvent can be used to correct the viscosity of adhesives or sealants to account for variability in the manufacturing process or inconsistent base materials in the resin formulation. 

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