For reaction polymers there are chiefly the 4 raw materials already mentioned: PUR, EP, PMMA and UP. These raw materials are basic products. They are inherently inhomogenous. For example, if one talks about PUR, one must first of all define very accurately what product one is talking about. For each product the chemicals industry specifies certain measurement data with a partially substantial breadth of fluctuation for characterization purposes.

Owing to physiological, ecological and/or economic requirements there are again and again changes in the raw materials which make a farce of empirical information gained over decades, expertises and research reports. In one case a total a 40 material data were checked for product changes. Compliance was not very convincing. Then there was the question as to what importance measurement data actually have. How large may the tolerances be? At this point let us leave it at the question, without becoming involved in the difficulty of providing an answer.