engleski

Spectroscopy for problem solving in production of pressure sensitive adhesives

The versatility of pressure-sensitive adhesive tapes (PAT)s is achieved by using various components to obtain the most important property of PAT – having the adhesive on (usually) a single side of the carrier. Most common carriers are OPP, PVC, PE, paper, etc. Primer coating is usually applied to connect the adhesive to the carrier although there are PATs without primer. Various compositions of the main adhesive can be divided in two main groups: solvent-based and hot melt. The adhesives can also be divided according to the elastomer used what is more important from the chemical point of view. The adhesivity depends on the (combination of) resins used and is adjusted according to the type of the carrier and the application of PAT. The non-adhesive side of the carrier may be coated with release coating to ease unwinding of the tape nd/or printed after applying the coating. The pigments may be added to the adhesive and/or the carrier. Even from such simplified description it is obvious that the PATs are very complex systems that have not been much studied so it is quite a challenge to approach any of the problems that might be encountered in course of their production. A part of investigations performed during more than a decade long cooperation with Sipro d.d., Umag in solving some of their production problems is presented. In number of occasions various spectroscopic techniques were used to analyse PATs with solvent-based adhesives and their components to determine the cause of problems encountered in production. Differences in abietic acid based resins were observed in FTIR spectra resulting in selection of more appropriate one. Similar resin that is a component of titan-dioxide based white pigment reduced cohesion of the adhesive to which it was added resulting in contamination of nonadhesive side of the tape what caused problems on printing onto the tape. NMR analysis of the main adhesive were performed on dissolution with an appropriate solvent and a correlation of noisy unwinding and the ratio of elastomer to reisns were determined. These experiments confirmed the role of spectroscopy in resoving problems in production of PATs and its importance in quality assessment. The need of further improvement in the use of those methods for research on polymer based adhesives became more obivous.

pressure sensitive adhesive tape; FTIR; NMR; abietic acid; rubbber; pigments

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