Evaluation of a Family of Thermoplastic Co-polyester Elastomers with Polyether Soft Segments as an Alternative Backing for Silicone Pressure Sensitive Adhesives
Silicone pressure sensitive adhesives (PSAs) are polycondensation-cured, thermoplastic, bodied resin-in-polymer materials. These materials have high adhesion and long-wear enabling their use in device attachment and other applications requiring high tack and transfer coating capabilities. Due to the incorporation of the resin, PSAs can be transfer coated onto a wide variety of backing substrates including polyurethanes, polyolefins, polyesters, and non-woven fabrics. These backings need to be breathable and flexible, provide a good surface for the adhesive to anchor to, and not impact the performance of the PSA. The goal of this study was to evaluate a family of thermoplastic co-polyester elastomers with polyether soft segments (TPC-ET) as an alternative backing for silicone PSAs. The effect on breathability, or moisture vapor transmission rate (MVTR), was measured as compared to a standard polyurethane backing. Additionally, the effect of the backing on the anchorage and adhesion levels of the silicone PSA were also assessed.
This study sought to evaluate different families of TPC-ET films as alternative backing substrates for silicone pressure sensitive adhesives. Several grades and forms of TPC-ET were selected, each having different modulus/stiffness and MVTR values. Laminates were prepared by transfer coating the cured film of silicone PSA onto either extruded films of TPC-ET, non-woven TPC-ET fabrics or polyurethane as a control. The adhesion of each laminate to stainless steel was measured with an Instron. The anchorage or bonding/interaction between the adhesive and the backing substrate was evaluated with a TA Texture Analyzer. The MVTR of the laminates was also measured to see what impact, if any, the increased MVTR of the backing substrate would have. The laminates prepared with the more hydrophilic TCP-ET grades did show a correspondingly higher MVTR when compared to less hydrophilic TPC-ET grades and polyurethane.
It was determined that TPC-ET did not have any significant negative effects on the adhesion and anchorage of the PSA. The MVTR of the laminates, although reduced compared to neat TPC-ET, did show a dependence on the TPC-ET grade and could be improved over a standard polyurethane backing substrate. It is concluded that TPC-ET could be a viable alternative backing for PSAs.
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