fep uv transmission data

Background

Current GMP practices in food and pharmaceutical processing plants demand that production areas are glass free, or that any glass, if broken, cannot find its way into the products. This poses problems in the use of EFKs (electronic fly killers) and sterilising plants which use ultraviolet emitting lamps.

This is because the UV radiation is notoriously harmful to polymers that would be able to protect the lamps. Any polymers used would not only have to be resistant to the UV, but also transparent to it over the whole life of the lamp.

Various polymers have been tried over the years, and many found to be totally useless, as they mostly age with the dose of UV radiation so that they become discoloured, and worse, become brittle. The most successful have been found to be the fluoropolymers containing high amounts of the -CF2- and -CF3 in the molecule chain, and the very best appear to be the completely fluorinated polymers.

Manufacturers' data on the UV transmission is variable or non-existent, and it has been found impossible to compare one material with another from their data. Tests commissioned by Adtech using a UV spectrophotometer to measure the transmission of flat polymer films showed up an unforeseen problem.

It was found that at UV frequencies the light was scattered by the polymer films, which were clear to visible light. The parallel beam of light used in the spectrophotometer was scattered passing through the film and gave a value significantly less than the total transmittance. The answer to this was to test the films or sleeves in situ and measure the loss in output of the UV lamp with the various coatings.

UVA Testing

The following test method was developed. A standard cylindrical UV lamp was mounted in a holder, and a calibrated UV radiometer mounted with its sensing head 25mm from the surface of the lamp.

As the output of UV lamps varies significantly over time, it was important to use one lamp for all tests, and not turn off the lamp in between testing.

Therefore, coatings were removed (cut) from lamps and reapplied to the standard lamp by making a join on the lamp opposite to the sensor head. The various coatings could be quickly applied and removed this way, yet the lamp could remain on and the sensor and lamp did not move from their relative positions.

Readings were taken as 1-minute total dose of UV, made alternatively on the various samples. This was then repeated 6 times including the lamp uncovered as control.

Technical Details

Lamp: Sylvania F15 T8 BL 15-watt 25mm diameter
Sensor: EIT UVIRAD UV integrating radiometer Model UR365CH1
Spectral Response: 320-390 nm (UV-A)

Sample Details

Sample 2 & 7: Adtech FEP 0.25mm
Sample 3: Adtech FEP 0.5mm
Sample 4 & 8: Competitive coating 1 0.22mm
Sample 5: Adtech development product XP 05 0.3mm
Sample 6: Adtech development product XM 04 0.2mm

UVA Test Results

in millijoules/cm²/min
Batch 1	Test 1	Test 2	Test 3	Test 4	Test 5	Test 6	Total	% UV-A loss
No coating	258	257	249	255	255	249	1523	0
Sample 2	245	243	243	243	246	237	1457	4.33
Sample 3	221	243	226	229	232	227	1378	9.52
Sample 4	207	211	205	213	207	207	1250	17.92
Sample 5	225	224	220	218	220	218	1325	13
Sample 6	249	244	244	242	240	239	1458	4.26


Batch 2	Test 1	Test 2	Test 3	Test 4	Test 5	Test 6	Total	% UV-A loss
No coating	252	253	255	252	253	253	1518	0
Sample 7	245	244	245	247	245	242	1468	3.30
Sample 8	211	210	214	218	211	214	1278	15.81

UVA Testing Conclusions

The test method is very consistent, easy to do, and gives the actual practical losses shown by lamp coatings as in use.

There is a very big difference between the coatings tested. A loss of 15% or more is unacceptable in EFKs, as the efficiency of the machine attracting and destroying flying insects is proportional to the UV-A output.

The test apparatus used here is portable and can be demonstrated by request.

© Adtech Polymer Engineering Ltd. 1999

UVC Research

Customers often ask for data regarding the long-term use of FEP with UVC lamps. Adtech did not have the data readily available and as such, gladly offered FEP heat shrink samples to be used for a research conducted by Light Sources on the long-term change in transmission of fluoroplastic heat shrink exposed to intense UVC radiations.

The research found that fluoropolymer heat shrink minimally degrades after 8000 hours. The UVC transmittance degradation amounted to approximately 3-7% on amalgam lamps and 0-3% on standard and high output lamps. The research also found that the UVC transmittance degradation levelled off to an approximately linear rate after 2000 hours.