Influences of heat seal lacquer thickness on the quality of blister packages.

A sealability of aluminium lidding foils against formable polymer materials of blister packages is usually achieved by a coating of aluminium with certain grammages of heat seal lacquers. To investigate influences of their thickness on quality of blister packages, lidding foils with different grammages of two lacquer types were manufactured. Sealing experiments (variation of temperature, pressure and sealing time) were performed. Sealed seam strengths were determined with mechanical tensile tests, tightness of cold form blisters were analysed by means of helium leakage tests. Time-dependent moisture uptake of stored blisters was monitored with micro-gas chromatography. By means of a simple calculation model the permeability coefficients of the heat seal lacquers were determined. Lidding foils with higher lacquer grammages showed significantly greater sealed seam strengths. Helium leakage tests showed only slight effects of heat seal lacquer grammage on tightness of blisters. But cold form blisters with lidding foils of higher lacquer grammages showed a significantly greater moisture uptake. Since the heat seal lacquers and the rigid polyvinyl chloride of the formable aluminium compound foils had similar permeability coefficients, the contribution of the lacquers to the total permeability of the investigated cold form blisters was only slightly.