Normal packaging rates for any application influence both the selection of strap and its joining methods. For low-volume, low-tension strapping of lightweight packages or bundles, buckles are a more economical method of joining strap since they do not require a unique sealing tool.
Plastic strapping can be sealed with poly hand tools using metal seals. Snap-on-seals can be used in combining strapping tools with seal magazines.
To ensure positive joint strength on plastic strapping, steel seals and special sealers can be used to form crimp joints. Crimp joints are formed by compressing the seal onto overlapping straps. The holding power of the joint is generated by squeezing the straps and the seal together.
Snap-on-seals use a grit coating on the inside to increase friction between the plastic strapping and the seals, while Nestack seals use steel teeth.
The Friction-Weld process joins polypropylene strapping and polyester strapping without the use of seals or applied heat.
One approach to lock strap ends is to cut, or "notch" the seal and the strapping it joins to develop tabs at the edges. These tabs are bent down (down notch joint) or bent up (reverse notch joint). The strength of the notch joint comes from the mechanical interlock between the seal strapping. Notch joints are typically used in waxed strapping in packaging and unitizing applications.
Another way to seal the ends of strapping is to press or "crimp" undulations into the seal and strapping ends. The strength of the crimp joint issues from the deformed seal creating high frictional forces. Crimp joints create high static and dynamic joint strengths are used in applications like carloading in which the strapped load is subject to severe impact.
Seallesss joints can be created with manual strapping tools or pneumatic combinations strapping tools. Using interlocking keys, the sealless joints provide static joint strength equal to that of notch-type joints. The reverse lock sealless joint emphasizes one reversed interlocking key for added security in impact conditions.