ASTM C794-2018 pdf free download

ASTM C794-2018 pdf free download.Standard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants
1. Scope
1.1 This test method covers a laboratory procedure for determining the strength and characteristics of the peel prop- erties of a cured-in-place elastomeric joint sealant, single- or multicomponent, for use in building construction. 1.2 The values stated in metric (SI) units are to be regarded as the standard. The values given in parentheses are provided for information only. 1.3 The committee with jurisdiction over this standard is not aware of any comparable standards published by other orga- nizations. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Summary of Test Method
4.1 This test method consists ofpreparing test specimens by embedding a wire mesh screen between two thin layers of the sealant being tested, on test substrates, curing these specimens under specified time and conditions, then placing the specimen in a tension-testing machine in such a way that the embedded wire mesh screen is peeled back from the substrate at 180°, while measuring the force exerted as well as the mode of failure of the sealant from the substrate.
5. Significance and Use
5.1 There are differences in opinion among those concerned with sealant technology whether or not this adhesion-in-peel test simulates the type of strain and e-tensile stresses encoun- tered by a sealant in normal use. Nevertheless, this test provides a valuable measurement of the ability of the cured sealant to maintain a bond to the substrate under severe peel conditions. 5.2 Many sealant manufacturers utilize the adhesion-in-peel test for determining the adhesive characteristics of sealant/ primer combinations with unusual or proprietary substrates. This test is especially useful for quality measurements com- paring batches of the same sealant relative to adhesion or for studying adhesion of a given sealant to a variety of substrates. 5.3 This test method alone is not appropriate for comparing the overall performance of different sealants in a given appli- cation. The adhesive force that determines if a given sealant is useful in a given application also depends on the modulus of elasticity and the degree to which the sealant will be strained. This test, as it exists, does not consider the modulus of elasticity, nor amount ofstress that will be produced by a given strain in an actual sealant in a moving joint. No known correlations are given to relate and apply modulus values to the peel values. 5.4 This test requires that the results indicate whether the failure mode is primarily adhesive or cohesive. It is important to note that a cohesive failure is not necessarily better than an adhesive failure, if the adhesive value is sufficient for the application. Having adhesive failure allows one to study the change of adhesion with time and with the various stress conditions.
6. Apparatus and Materials
6.1 Tensile Testing Machine with tension grips capable of pulling at the rate of separation of approximately 50 mm (2 in.)/min, and having a chart indicator calibrated in 0.45-N (0.1-lbf) units. 6.2 Standard Substrates—This test method may be per- formed on a wide variety of substrates. See Guide C1375 for a description of standard substrates and recommended surface preparation. Since adhesive properties of a joint sealant are related to the nature of the substrate, it is strongly recom- mended that whenever possible that adhesion-in-peel testing be performed on substrate samples that are representative of the building materials. Examples of such substrates include brick, marble, limestone, granite, aluminum, stainless steel, plastic, ceramic tile, and others.