TACK OF PRESSURE-SENSITIVE ADHESIVES WITH 4-NONYL-PHENOL FORMALDEHYDENOVOLAC RESINS AS TACKIFIERS

The tack, expressed as the rolling friction coefficient of some pressu re-sensitive adhesives obtained on the basis of natural rubber and 4-n onylphenol formaldehyde novolac resins of viscosities in the range of 13.6 - 2065.7 Pa . s, was measured at 20 degrees C by rolling motion o f a ball as a function of the nature of the resin in adhesives, its co ncentration, thickness of the adhesive and velocity of the ball. The m aximum amount of the tackifier resin to be used for a high tack of an adhesive depends on the type of resin and its solubility in the rubber phase. The tack of the tested adhesives is a function of the theologi cal properties. The correlation found between the apparent shear visco sity and the rolling friction coefficient showed that the best results are obtained for rubber-resin mixtures with viscosities ranging withi n 1.7 . 10(6) and 3.4 . 10(8) Pa . s.