Лако-красочные материалы — производство

Tests are performed for a wide variety of different reasons. Many tests have as a goal to compare different materials, procedures, products, and so on. For such comparisons to be meaningful, it is important that some type of standard procedure be used to obtain the information that will be used for comparison. This is, of course, one of the most important reasons for having standards. The goal is to separate, as much as possible, the results obtained from differences due to the laboratory or operator. In principle, one should be able to compare results from one operator (say, in Europe) with those in another place (say, in the United States).

Furthermore, all tests are not conducted with equa1 rigor. Quantitative testing is generally expensive and time consuming. Testing organizations have at times, therefore,

developed qualitative tests that might be used to eliminate obvious unlikely candidates quickly. ASTM-D-3808, Spot Adhesion Test, is a good example of such a test. It is well established both theoretically and empirically that all adhesive-substrate pairs are not equally compatible. An adhesive that might tightly adhere to one substrate may form very weak bonds with other substrates with varying degrees between these extremes. To prepare and test standard quantitative test geometries (some of which will be described subsequently) for a large number of candidate adhesives for a given substrate could be prohibitively expensive. ASTM D-3808 suggests the following alternatives:

1. Prepare candidate substrates using techniques similar to those expected in service.

2. Mix a quantity of the candidate adhesive according to the procedures specified by the adhesive manufacturer.

3. Small spots of the adhesive (typically 5-10 mm in diameter) are placed on the substrates using application and curing techniques comparable to those expected in service or specified by the manufacturer.

4. The operator then uses a thin stainless steel spatula (or similar probe) to pry or lift the spot from the substrate. The operator then uses his or her senses to assess ease of separating the spot from the substrate.

Based on this operation, a decision is made as to whether this system is worthy of further quantitative analysis. Some quantitative tests are the subject of the next section.