29 сентября, 2015 
Pokraskin It was noted above that, during the second half of the nineteenth century, mixtures of terpene resins (e. g. rosin) and natural rubber were introduced as PSAs, and used initially for the production of adhesive plasters and simple adhesive tapes (see Section 5.1). The mixtures are produced in suitable organic solvents which evaporate after application of the adhesive, and this results in a self-adhesive mass characterized by a non-homogeneous dissolution of terpene resin in natural rubber.
The terpene-rich phase forms low-rubber domains that are responsible for tack (the property that enables the adhesive to form a bond immediately on contact with another surface). Although the remaining rubber is an elastomer that may transmit forces, it is still sufficiently flowable to fill the surface roughness to a certain extent, even after the application of a second adherent. The molecular fundamentals underlying the phenomenon of tack is not yet been fully elucidated.
In the medical sector, these mixtures of rubber and terpene are still used today, whereas in other industrial sectors natural rubber has been replaced by synthetic rubber copolymerized with styrene; this results, upon solidification, in the formation of loadable domains.
Self-adhesive gummings that are used to fasten envelopes are based on natural rubber lattices that are used to coat both parts of the envelope closure. Bonding takes place by compressing both coatings, resulting in a diffusion process (see Section 8.5).
94 I 5 Chemistry and Properties of Adhesives and Primers
5.9.4
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