50 bar(g) is the pressure resistance of PET aerosol cans, MRX002

50 bar(g) is the pressure resistance of PET aerosol cans, MRX002

November 21, 2016

Summary: MRX002 vials were tested for pressure resistance. Their average burst pressure is 50 bar(g), ranging from 41 to 56 bar(g). This is well above the vapour pressure of HFAs at room temperature (5.7 bar for HFA134a), and at 60oC (16.8 bar), as required for leak testing by the FDA.

Purpose: MRX002 vials are clear PET containers designed to visualize aerosol formulations. In particular, MRX002 vials are designed as laboratory tools for the study of HFA pMDI formulations. MRX002 vials were tested for pressure resistance in order to document safe use pressure limits. Tests were carried on 35 MRX002 vials from one single batch.

Experimental: The burst pressures of 35 MRX002 vials were recorded with the DH Industry burst pressure tester (0325/100). MRX002 vials were fastened securely to the tester, filled with water that was pressurised at a constant rate (1.3 bar/s) until bursting. The vial pressure was recorded every 100 ms, and the pressure gauge was accurate within 0.01 bar. The room temperature was 22oC.

The main features of MRX002 vials are:
-clear PET vial
-Dimensions: Height 75 mm, Diameter 22 mm, Crimp diameter 20 mm
-Material: amorphous PET (Polyethylene terephthalate)
-Example of compatible pMDI valves: VARI KHFA range, Bespak MDI valves, Coster MDI valves.

Results: A simple statistical analysis of the burst pressures recorded can be found below. The average burst pressure was 50.1 bar(g), with a spread of 41.2 to 56.2 bar(g). The corresponding box plot and data spread is found in the graph below. No out-liers were recorded.

Burst pressures of MRX002 vials
Min 41.2
Average 50.1
StDev 4.2
Median 51.5
1st quartile 46.2
3rd quartile 52.8


Conclusions: The MRX002 vials burst pressure is above the vapour pressure of standard propellants (see table below), such as HFA143a, HFA227, Propane and Isobutane.

  HFA227 HFA134a Propane Isobutane
20oC 3.90 5.72 7.51 2.75
60oC 11.75 16.82 18.54 7.76

The 1998 FDA CMC guideline recommends stability testing of HFA pMDI formulations at the following conditions:
-accelerated testing 40± 2oC
-intermediate testing 30± 2oC
-long term testing 25± 2oC.
The vapour pressures of HFA formulations at these conditions will therefore be less than the burst pressure measured in this experiment.

In 2004, the FDA published recommendations for testing the leak rate of pMDI formulations. The tests need to be performed at 55± 5oC for 1.5 to 3.5 minutes. The burst pressures of the MRX002 vials recorded are less than the vapour pressure of HFA propellants at 60oC. When stress testing MRX002 vials at high temperatures (e.g. 60oC) care should be taken to monitor the vials carefully and take appropriate measures to ensure safe handling, as the softening temperature of amorphous PET is 67oC and creep can be expected as the PET is warmed up.

Merxin is very grateful for the assistance of DH Industries Ltd in performing these tests.

Warning: These experimental results demonstrate the pressure resistance of a single batch of MRX002 vials. Further batches will be tested to establish the robustness of the MRX002 manufacturing process. These results therefore do not constitute a legal pressure rating of the MRX002 vials. Users of the MRX002 vials must carry out their own risk assessments before using the vials, and make their own judgement on the best way to handle them. For more information and to order MRX002 vials, send us an email at info@merxin.com or get in touch via our website: merxin.com/contact-us.

About Merxin (www.merxin.com): Merxin is a generic medical device company that supplies generic inhalation devices “off the shelf and ready to use”. By supplying standardised off-the-shelf devices, Merxin provides clients with a lower cost and lower risk route to market. With the expertise and support of the Merxin team, you can develop and deliver your inhaled dosage forms easily and efficiently: www.merxin.com.

Merxin is a Partner of Aedestra Ltd:

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