Caps and Closures

Q. Do the rubber stoppers that WHEATON sells, contain natural rubber latex?
A. Stoppers made from natural red rubber and stoppers made from chlorobutyl-isoprene blend contain natural rubber latex. All of the other stoppers are latex-free.

Q. What is the maximum dry-heat temperature the stoppers can withstand?
A. Stoppers made from silicone or FKM can withstand dry-heat temperatures up to 200°C. All of the other stoppers can withstand dry-heat temperatures up to 100°C. It should be noted that all of the stoppers can be steam autoclaved at 121°C. The given temperature limits are for dry heat environments.

Q. Which stopper is usually used when packaging contact lenses in serum vials?
A. Our item 224100-178 is made from silicone and was originally referred to as the contact lens stopper.

Q. Is a polypropylene cap with a poly-vinyl liner compatible with DMSO?
A. No. Please check the Chemical Resistance Chart found in the Technical Data under eCatalogs in Resources on our web site for more compatibilities.

Q. How can I tell the thread size of my cap?
A. Please refer to “Determining a Cap’s Thread Finish” in the Technical Data under eCatalogs in Resources on our web site.

Q. Can I steam autoclave aluminum crimp seals?
A. Yes. The aluminum seals can be steam autoclaved at 121°C at 15 psi for 30 minutes.

Q. Which cap lining material provides the best gas/moisture barrier properties?
A. If compatible with the product, a metal foil liner would provide the best barrier to gas and moisture transmission.

Q. What is the recommended application torque for a 20 mm screw cap?
A. The industry rule-of-thumb for determining application torque in inch-pounds, is to divide the screw thread size in half. For a 20mm screw cap, the application torque would be 10 in-lbs. The rule-of-thumb should be used for guidance only.