Acidic hot-melt adhesives are useful in many applications, as the acid functionality can contribute to better substrate wetting and better adhesion to polar, nonporous surfaces.

Acidic hot-melt adhesives are also quite corrosive to conventional iron and steel adhesive application equipment. The acid number determination will tell an equipment manufacturer if corrosion-resistant equipment for an application should be recommended. The need for corrosion-resistant equipment will vary depending on the acid number of the hot-melt adhesive and type of metal that will be bonded.

1.1 This test method covers the determination of acid numbers of hot-melt adhesives.

1.2 This test method is applicable for hot-melt and hot-melt/acid systems that are soluble under the conditions described. The hot melt must also give light- or medium-colored solutions when dissolved. If this is not the case another method must be used.

1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.

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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific caution statements are given in 7.1 and 7.2.