RTP Company, a compounder of custom engineered thermoplastics, is offering tribology data from a friction test to help designers of drug delivery devices select the best possible material for single-use applications
It is critical that devices such as auto-injectors, injection pens, stop cocks, and safety syringes move easily and have a low break-away force to overcome friction
Designers, OEMs and molders are keenly aware of the issues that can arise when single-use drug delivery devices fail. It is critical that devices such as auto-injectors, injection pens, stop cocks, and safety syringes move easily and have a low break-away force to overcome friction.
Various external factors, such as long periods of inactivity, shipping, and cold storage conditions can all have an effect on the friction behaviour of plastic-on-plastic moving parts.
These factors increase the chances of stick-slip phenomena or “stiction”, resulting in poor performance of a drug delivery device.
RTP Company has developed a friction test to accurately predict friction behaviour in single-use devices.
The company has explored base resins including polycarbonate (PC), acetal (POM), acrylonitrile butadiene styrene (ABS), polycarbonate/ABS alloy (PC/ABS), high density polyethylene (HDPE), and polybutylene terephthalate (PBT).
These resins were tested in a variety of combinations with friction reducing additives including polytetrafloroethylene (PTFE), perfluoropolyether (PFPE) oil, and a selection of silicones, along with RTP Company’s own all polymeric wear alloy, known as APWA Plus.
Testing the friction behavior in various combinations of resins and friction reducing additives involves the measurement of the static and the dynamic coefficients of friction.
The threshold representing the smallest delta between the two measurements has been coined by RTP Company tribologists as the “glide factor”.
Consistent, repeatable tests showed that the ideal friction pairings exhibited low static coefficient of friction (< 0.15) and a Glide Factor of < 0.015.
