Adhesives for Needle Bonding

Following is a list of factors that adhesive specialists will wish to review to assist in the adhesive selection process for the best needle bonding adhesive for a specific application.

Needle Purpose

Needles are used throughout healthcare for injection, blood drawing, biopsy, etc…  Other industries use needles for dispensing, test fluid extraction, and injection, etc…  Understanding the use of the needle supports a good understanding of the optimal test methods (eg. Straight needle pull or 90 degree twist) and chemical resistance requirements.  Many industrial needles have prolonged exposure to harsh chemicals making epoxy adhesive preferable to light cure adhesives for needle bonding.  In other applications, the placement of the needle bonding adhesive is critical. And in-line QC testing with fluorescent indicators makes light cure adhesive the ideal choice.

Bond Area

The cannula gauge, length of the well, and length of engagement with the hub all contribute to the total bond area.  In some needle bonding applications, a structural bond is formed between the cannula and the hub.  Whereas, in others, the bond is very strong to the needle and simply locked into the hub by annular rings and other design features.

Design & Viscosity

The appropriate viscosity will quickly fill and level out in the well. In some designs, it is desirable for the adhesive to also fill the area beyond the well to utilize the full engagement with the cannula.  In designs in which the cannula is fully seated or designs in which the cannula extends past the hub engagement area, there is little opportunity for the adhesive to wick into the cannula and occlude it. 

Process & Adhesive Chemistry Selection

Single component epoxy adhesives and light cure adhesives are generally the first choices.  Single component epoxy adhesives provide tough, environmentally resistant strong bonds to metals and eliminate concerns related to depth of cure. While light cure adhesives provide ease of process and bond clarity. They are also ideal for needle bonding applications that require a penetrative viscosity to wick between close fitting components.

For further help with needle bonding and adhesive selection, please contact Permabond here.