A frequent tape question is “when should I recommend an acrylic adhesive carton sealing tape vs. a hot melt adhesive carton sealing tape?” If cost is “king” and if the tape is hand applied, utilize an acrylic. If the tape is going to be machine applied, start with a hot melt and examine the tape head tension and condtion of the rollers. If the end user is willing to adjust tape head unwind tension and allow cleaning of the rollers and blades, an acyrlic will perform well and create bottom line cost savings.
Hot melts, with the proper blend of resins and SIS, can have very high shear characteristics (holding power). The more SIS, the higher the shear. High shear hot melts are more expensive, relatively speaking, but they perform well in over-stuffed box applications and in situations where there the box flaps are under tension – wanting to push up and not stay flat (particularly with double wall vs. single wall boxes). Acrylics fail in these applications; they exhibit poor shear.
Acrylics have a wider temperature range than hot melts (32 degrees F to 150 degrees F). Hot melts (40 degrees F to 120 degrees F). In high humidity conditions such as food plants, they seem to perform better than hot melts. In low humidity conditions, they also seem to be more favorable. A high shear hot melt offers better quick tack than an acrylic. Both adhesive types appear to offer good fiber tear. For the most part, acrylics seem to take longer to completely wet out ( adhesive being absorbed into the surface of the substrate).
Both of these adhesives perform poorly on heavily printed surfaces, especially where a varnish or UV coating is applied over the print. Natural rubber adhesive carton sealing tapes and solvent acrylic carton sealing tapes should be tested for these applications. In dusty environments or heavily re-cycled corrugated sealing applications, natural rubber backed tapes perform very well. If a tape is going to be applied over a direct thermal bar code or ingredients label, use a hot melt…the acrylic adhesive will react with the print on a direct thermal label – distorting and fading the print on the direct thermal label (this does not happen on thermal transfer printed labels with the use of a ribbon).