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A pesquisa demonstra como é o comportamento de dois materiais conhecidos comercialmente como mastic em relação às forças de cisalhamento de selantes. No mercado existem dois tipos de mastic, um da família de silicones e outro da borracha butílica. A pesquisa teve o objetivo de esclarecer junto à receita federal e ao mercado, que as propriedades dos dois tipos são muito diferentes, apesar de ambos sofrerem um processo de cura. Com o tempo há aumento das forças de coesão e adesão de ambos, o que evidencia o processo de cura.This study reveals the response to shear forces for two materials known as mastic. There are two kinds of mastic in the market, one of the silicone family and another made with butyl rubber. The aim was to demonstrate to the Inland Revenue and to the market that these materials exhibit very distinct properties, although both undergo the curing process. As time goes by, there is an increase in the forces of cohesion and adhesion for both types of mastic, which is evidence of the curing process.

Butyl mastic is used in a number of industrial areas and in particular in the production of adhesives. The performance of this material can be improved by using ionizing radiation. In this work we showed that the shear forces in butyl mastic were modified when the material was exposed to radiation, and as a consequence the adhesion strength was increased. This was done by comparing the shear forces of butyl mastic before and after the exposure to ionizing radiation. The result was an increase of 440% of the average shear strength between the sealant and the substrate after the irradiation. This work can be considered as an important contribution to the field of butyl mastic, sealants and adhesives. [ABSTRACT FROM AUTHOR]