Specific migration testing rubber

In most cases the pigments used are also required to be migration-resistant. The suitability test is also carried out with 5 different pigment concentrations. To test the fastness to bleeding, the unvulcanized colorations are brought into defined contact with a white milled sheet of specific composition and vulcanized wet for 20 minutes in open steam at 140°C. During this process, half the coloration is often covered with a wet cotton cloth to determine whether the cloth, the rubber or both are stained by bleeding. 

The finished rubber product will have to meet a specification in which a number of properties (e.g. hardness, tensile strength and elongation) are given target values. A number of other properties can be assessed, and these will depend upon the type of rubber and the application that it is going to be used in. An important example is the overall migration limit test, with the food simulant and test conditions (temperature and time) being dictated by the end use conditions. 

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