UV stable translucent inflammable polymer
UV stable translucent inflammable polymer
(OP)
Glass seems to be the only suitable material for the bulb part of a lightbulb, because of all the demands on thermal,optical, inflamability and mechanical requirements....however I have a design need for a secondary off-white opaque covering adjacent to the glass bulb on a low-energy lightbulb.....effectively a second skin to the glass bulb but with a small (circa 5mm)air gap between them. This immediately removes the thermal demand but the optical (UV stability) and inflammable requirements remain.
I have looked at blow-moulding using PC or a PC alloy but am concerned about Yellowing of the cover.
I am looking for advice on the most suitable polymer to use.
Many Thanks
Mark
I have looked at blow-moulding using PC or a PC alloy but am concerned about Yellowing of the cover.
I am looking for advice on the most suitable polymer to use.
Many Thanks
Mark





RE: UV stable translucent inflammable polymer
Second issue is the exposure, the UV stability has to be OK for the source light over 4000 hours as well as daylight exposure.
RE: UV stable translucent inflammable polymer
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RE: UV stable translucent inflammable polymer
RE: UV stable translucent inflammable polymer
There are other materials that are inherently translucent-like, like Kynar, which is used for the color coating on aluminum roofs and in vinyl siding.
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RE: UV stable translucent inflammable polymer
Domestic use is usually heavier than the automotive, ie. taking the 4000 hrs target then for an average 30mph that gives 120K miles, perhaps the average life of a vehicle?
thanks
Mark
RE: UV stable translucent inflammable polymer
""Plastic" (polycarbonate) lenses can become cloudy and discoloured. This is due to oxidation of the painted-on lens hardcoat by ultraviolet light from the sun and the headlamp bulbs. If it is minor, it can be polished out using a reputable brand of a car polish that is intended for restoring the shine to chalked paint. In more advanced stages, the deterioration extends through the actual plastic material, rendering the headlamp useless and necessitating complete replacement. Sanding or aggressively polishing the lenses, or plastic headlight restoration, can buy some time, but doing so removes the protective coating from the lens, which when so stripped will deteriorate faster and more severely."
Because my cover needs to be fairly thin (circa 1mm) and is very close to the light source then the polymer of choice must be as UV stable as possible.
RE: UV stable translucent inflammable polymer
Check www.lurans.com there is one FR grade.
Chris
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: UV stable translucent inflammable polymer
Unless the bulb "glass" is actually quartz, or pure fused silica, it is unlikely to pass any significant amount of UV radiation.
It will, however, pass quite a bit of IR radiation, and I'm not sure a 5mm airspace would be sufficient to keep the temperature of a polymer cover below an arbitrary limit in all possible surroundings...
RE: UV stable translucent inflammable polymer
Trueblood..interesting comment re: UV and IR..the lightbulb type I'm working with is the low-energy type, basically a compact fluorescent, so the heat side is low, circa 50C.
RE: UV stable translucent inflammable polymer
If the ASA is too milky at that thickness then you could dilute it with either SAN or PETG to make it more transparent. That'll let you adjust the opacity.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: UV stable translucent inflammable polymer
Your posting reminded me of it as you're going for a translucent effect.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: UV stable translucent inflammable polymer
I think your stuck with a heavily UV stabilised FR PC.
You need to check if the opalescent pigment, UV stabiliser and FR additives interact to reduce effectiveness. I know the opalescent pigments used for light diffusers are difficult formulations.
The difficulties are translucent at a repeatable level of transmission and diffusion along with transparent flame retardants. FR additives in general tend to be unstable
Regards
Pat
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RE: UV stable translucent inflammable polymer
Chris, interesting sounding polymer, Thermoshift, reminds me of a glaze used in the ceramics industry for indicating when a mug (cup) has hot fluid in it. If it goes transparent when cool and gradually less so when hot there must be many applications out there wanting to speak to you!
RE: UV stable translucent inflammable polymer
FR to UL Vo at 1mm is not going to happen if you want transparent.
iirc, 10% GF PC is Vo at thin sections. With a good UV package might work.
(We make PC covers for CF festoon lights - never had a problem reported yet regarding yellowing, but the PC is around 15mm from the tubes.)
www.tynevalleyplastics.co.uk
RE: UV stable translucent inflammable polymer
RE: UV stable translucent inflammable polymer
ThermoShift is getting a lot of interest alright, just keen to get someone to try it in a lighting application as I think it'd look cool. You can choose whatever transparency temperature you want from -20C to +80C.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: UV stable translucent inflammable polymer
I really do keep looking for an application for thermoshift as I find it fascinating.
Bayer certainly make a transparent FR PC, but it does not get down to V0 at 1mm. To get that level, transparency is (or was last time I looked) lost.
What is the real maximum temperature and what is the real risk of fire.
Regards
Pat
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RE: UV stable translucent inflammable polymer
The cover has to comply with "Luminaires – BS-EN 60588 – 1 , to amendment A11" this is because the cover would be within 30mm of a potential heat source. i.e the electrics of the Compact Fluorescent. So the risk is not the normal running temperature (a contact thermo-couple gave 65C peak on the glass of the CF, with 5mm air gap I'd expect circa 50C for the cover)but the risk, however small, of the ignition source from the FC electrics causing the cover to catch fire. I shall check up on the above standard to see if it specifies a performance standard to comply with, such as V0, V1, V2 from UL94, but all that I've been told to date is that the polymer must be inherently inflammable.
Concerning the translucency a very frosted look wouldn't be acceptable, it has to be a homogeneous dispersion resulting in a look just as for Opal lightbulbs (I note these are clear glass that have been painted on the inside).
Thanks again for your input.
Mark
RE: UV stable translucent inflammable polymer
http://www.frxpolymers.com/
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: UV stable translucent inflammable polymer
For 50C, PVC might be ok. Inherently FR and good UV too. Blow mouldable. Try a mineral water bottle!
H
www.tynevalleyplastics.co.uk
RE: UV stable translucent inflammable polymer
Thanks for the suggestion, I'll try one out (and check for the markings on the base first!), however difficulty is knowing whether I'll get discolouration of an opal coloured one after a couple of years use?
I'll see if the suppliers do them in a translucent off white for 1mm thick.
Thanks again, Mark
RE: UV stable translucent inflammable polymer
How are you going to insure that there is always a 5mm gap? What happens if the bulb gets bumped or assembled wrong and the plastic touches the glass?
RE: UV stable translucent inflammable polymer
I have considered using a clear PC and doing something similar because this is more tolerant to yellowing, but I'm hopeful that I can find a polymer, translucent but opal tinted that is coloured in the batch.
There's no problem working to the 5mm gap.
Thanks again, Mark
RE: UV stable translucent inflammable polymer
Makrolon LED2643, FR7087, 6717, and 3103
Harold
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RE: UV stable translucent inflammable polymer
Luckily I realised the OP was not aware of the idiosyncrasy in the English language in that flammable and inflammable mean the same thing which is the opposite of non-flammable and flame retardant.
Regards
Pat
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RE: UV stable translucent inflammable polymer
RE: UV stable translucent inflammable polymer
That is how I picked it up. I thought why on earth would he want that part to be flammable.
Regards
Pat
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RE: UV stable translucent inflammable polymer
I may have missed it in the postings. . . Do I understand correctly that ThermoShift does not necessarily have a "normal" state and can be customized to go opaque to transparent OR vice-versa at that wide range of temperatures? When at its most opaque, what wavelengths are effectively blocked?
Would its properties make it suitable for a glazing material in architectural or agricultural applications?
It does sound like interesting stuff.
Regards, Ornery.
RE: UV stable translucent inflammable polymer
Regards
Pat
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RE: UV stable translucent inflammable polymer
Sorry for the delay in the reply, I've been away on business.
The best way to describe the ThermoShift is the movie of it in action on my website. It speaks louder than words.
You're right that you can pick whatever transparency temperature you want so that material is very tunable. One grade is transparent at -20C another is transparent at +80C and we can make anything in between. The material becomes opaque above and below your chosen transparency temperature.
The mechanical properties are just like ABS so a great balance of modulus, strength and impact resistance. To use it in glazing you'd have to add a film to protect it against UV light.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry