Minimum Seal Strengths

I am always asked, �What is the proper minimum seal strength?� The answer I always give is twofold. 
First, the numerical value for seal strength should be based upon the characteristics of the materials being sealed and the sealing process. One should always achieve the optimum seal strength for the materials being sealed. If strength needs to be adjusted, it is usually better to alter the materials, such as coating weight, rather than the process conditions. 

The second answer I give is that the required seal strength should vary mostly with product size and weight. When packaging a low-profile or low-weight device, such as a gauze sponge, it might be possible to accept a seal strength value under 1 lb. Heavier and bulky products, like metal implants, might require minimum seal strengths of 3 lb. Of course, don�t fall into the number trap�be sure of your test method. A 3-lb, 180� supported seal strength might seem like a lot, but in reality it is only 1.25 lb unsupported. 

In all cases, the results of environmental testing should be used to assess package integrity. This testing is a requirement to validate package design, as put forth in ISO 11607.