There are references within current plastic aerosol regulation and development
requirements that can help to understand the effects of UV degradation in
plastic aerosol containers; however, few technical references or literature
are available to guide this testing...
Figure 4: Tensile (Strain, Stress and Modulus) comparison values for (left) artificial radiation exposure for duration of chamber study (1,500 hours) & (right)
empty bottles and filled/pressurized bottles exposure to outdoor weathering radiation (12 months).
Solar Radiation
Sunlight includes the UV, visible and the infrared radiation in
the form of wavelengths between 295–3,000nm. Solar Radiation
(dosage) is measured with a pyranometer, reported in terms
of total radiation, measured between the wavelength of 295–
3,000nm and dosage that account for the UVA and UVB range
between the 295–385nm wavelengths. In order to correlate solar
radiation exposure to simulated radiation dosage, the TUVR was
used since the UV wavelengths typically cause the most polymer
degradation, even though the UV range is only about 7% for the
overall total sunlight radiant energy.
The 12-month accumulation of TUVR dosage value was used
and converted to a daily value. The PARG chamber method
settings were chosen to provide dosage and control temperatures
inside the chamber to allow for a pressurized PET plastic
container.
Conclusion
Physical and analytical properties were measured from samples
exposed to UV. A slight change in molecular characteristics was observed,
but there was no negative impact to the physical properties,
such as burst strength. The burst pressures through the timeframe
of the study stayed well above all the minimum regulatory requirements.
An interested party may consider evaluation of other physical
properties, e.g. environmental stress crack resistance (ESCR),
dimensional stability, volume expansion, etc., when developing a
container. Through the correlation studies, a lab method was developed
and validated that could accurately simulate UV radiation
using the Xenon-Arc. Moreover, the conditions inside the chamber
could be conducive to testing a plastic pressurized container.
PARG not only developed a methodology for the plastic
container integrity (PARG 20.0) testing but applied the same
premise to product evaluation, as well (PARG 21.0), which
can be used to assess product performance with a non-opaque
container. PARG makes no judgment to product performance or
container integrity but provides applicable test methods.
Test Methods 20.0 and 21.0 are now available to members for
purchase through thehcpa.org. If interested in this data or PARG
membership, contact: info.ignitesolutions@TheHCPA.org. Spray
References
1. ISO 877-2, 2009 (confirmed 2017), Plastics-Methods of exposure to Solar
radiation, Part 2: Direct weathering and exposure behind window glass,
Method B, copyright International Organization for Standardization, ISO
Central Secretariat, Chemin de Blandonnet 8, CP 401 - 1214 Vernier, Geneva,
Switzerland.
2. ISO 4892-2, 2013 (confirmed 2018), Plastics-Exposures to laboratory light,
using window glass filters, Method B, Cycle No. 2, copyright International
Organization for Standardization, ISO Central Secretariat, Chemin de Blandonnet
8, CP 401 - 1214 Vernier, Geneva, Switzerland.
3. PARG 20.0: Ultraviolet Exposure Using Xenon Arc Light Apparatus for
Aerosol Products in Plastic Containers, Aerosol Products in Plastic Containers
Guide, Third Edition, 2020, copyright PARG, LLC, 1667 K Street, NW #300,
Washington, DC, 20006.
4. PARG 21.0: Ultraviolet Exposure of Product Formula using Xenon Arc Light
Apparatus for Aerosol Products in Plastic Containers, Aerosol Products in
Plastic Containers Guide, Third Edition, 2020, copyright PARG, LLC, 1667 K
Street, NW #300, Washington, DC, 20006.
June 2021 SPRAY 27