Preparation of pressure-sensitive adhesives for the production of sticky foam at ambient temperature

In this paper, formulations for producing thermoplastic sticky foam, useful in preventing, delaying, or impeding access to protected materials or areas for military or law enforcement purpose, were investigated. Various formulations of pressure-sensitive adhesives (PSAs) using different amounts of thermoplastic elastomers (isoprene or Kraton D), tackifying agent (petroleum resin), chlorinated paraffin and silicone surfactant were prepared in toluene at ambient temperature. After vacuum stripping the solvent, the stability of the formulations and their tack properties (by tensile and hold tests) were determined. Combinations of the optimized formulations with different foaming agents were studied and compared concerning the expansion ratio and the stability of the foam (t_1/2 life time). A thermoplastic sticky foam with a density of 20 kg/m³ and a foam stability of 30 min (t_1/2) can be obtained by mixing two foaming agents (CHClF₂ and CO₂) with the optimized composition (comprising 60 parts of isoperene, 40 parts of petroleum resin, 50 parts of silicone surfactant and 250 parts of chlorinated paraffin (formulation no. 8)) in a pressurized vessel and releasing the contents to atmospheric pressure.