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Using Tackifiers and Plasticizers in Pressure Sensitive Adhesives

SpecialChem / Andy Extance – Feb 25, 2009

In the 1960s, a Swedish scientist named Dahlquist3 observed a minimum level of compliance that a PSA must have in order for it to exhibit tack. This observation can also be interpreted as a maximum value of the modulus, the measure of the stiffness and resistance of the adhesive, and is broadly known as the Dahlquist criterion. This can be broadly described as a need for the material to be pliable in order to absorb energy inputs rather than allowing it to propagate through cracks. The Dahlquist criterion is usually taken as a maximum modulus value of 106 Pa. The phase changes that the material's modulus undergoes with temperature also play an important role in its tack. The material moves from a free-flowing liquid, to a long plateau where it takes on a rubbery form over a wide temperature range. In the third phase the rubber undergoes a transition where it gradually becomes more like the fourth, glassy stage. The lower the glass transition temperature, Tg, the less effective the elastomer is at dissipating energy input at normal debonding rates and room temperature.

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