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Plastic material which is permeable for IR (infra red) signals
3

Plastic material which is permeable for IR (infra red) signals

Plastic material which is permeable for IR (infra red) signals

(OP)
As mentioned in subject - Can anyone tell me what plastic material shall I use for device with IR antena(reciever)?

thx in advance

RE: Plastic material which is permeable for IR (infra red) signals


Iirc, tv remote sensor windows are acrylic (PMMA). IR transparent dyes are used to make them black/dark grey.

As IRstuff mentioned, very frequency dependant.

Cheers

Harry

RE: Plastic material which is permeable for IR (infra red) signals

Every organic compound including polymers adsorbs specific IR frequencies characteristic of what chemical bonds are in the material. This is used to identify compounds. If you go to www.sigmaaldrich.com you can search "polyethylene" and that will give you a link to the FTIR spectrum.

PMMA: http://www.sigmaaldrich.com/spectra/ftir/FTIR002075.PDF

PE: http://www.sigmaaldrich.com/spectra/ftir/FTIR002060.PDF

Other polymers are there too.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

RE: Plastic material which is permeable for IR (infra red) signals

(OP)
thx to all of You guys

By IR - I mean "Infra Red".

I`haven`t got direct fraquency value yet(till this moment I do not know which exactly type of antena-receiver will be choosen).

However I do know that all types range from 30 kHz to 56kHz

RE: Plastic material which is permeable for IR (infra red) signals

seems that you are confusing IR with ultrasonic when you talk about 30 to 56 kHz
IR is in the THz range and ultrasonic is above about 20 kHz

RE: Plastic material which is permeable for IR (infra red) signals

Sounds like a TV remote or IRDA, which is usually around  800 nm, in which case, just about any clear red plastic will work.

N.B.  This is normally called near IR, which extends to around 3000 nm.  At that point, it's referred to as mid or medium IR.  Each requires vastly different materials and devices.

TTFN

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RE: Plastic material which is permeable for IR (infra red) signals

IR or infra red covers a broad band of the microwave spectrum. Various plastics transmit some in areas and block in other areas of the IR band. In fact, the transmission peaks are used to identify plastics as no two types have the same transmission and absorption characteristics.  

Regards

eng-tips, by professional engineers for professional engineers
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RE: Plastic material which is permeable for IR (infra red) signals

(OP)
thx again for great replies

further details are :

The modulation is at 38khz, but the wave length of the IR is 950nm

I spoke with consultant from Basf already and he suggested me to consider Terlux(MABS)material.

I spent some time on investigation among existing parts. I noticed some parts which plays a role as glass between two houshould are made by PC(these parts hide IR antena and diplay of chanels).

Is there serious condition to consider between use such PC material between other - ABS, MABS - for little housing design?

The question

RE: Plastic material which is permeable for IR (infra red) signals

I have worked at BASF in the past and know quite a bit about MABS if you have a question at some point.


PC has brilliant impact resistance and very bad chemical resistance (it will shatter if you expose it to solvents or cleaning agents). PC has poor flow and thus is not great for thin walled parts. PC has very good HDT.

MABS has good impact resistance and chemical resistance. Good flow but lower HDT. The impact modifier in MABS is butadiene based so it is not suitable for use outdoors because sunlight will attack it.

Price per unit volume is about the same. PC is cheaper per kilo but has a higher density so you have to adjust the price for the density.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

RE: Plastic material which is permeable for IR (infra red) signals

(OP)
well this device is going to be use within laptop, so I suppose the outdoor use is out of scope.

The neat thing is how to paint such material to be less transparent for human eye, and still well transparent for IR.

I am close to accept MABS compound becouse of its good conditions for filling small areas.

RE: Plastic material which is permeable for IR (infra red) signals

Paint?  You don't paint these things.  They should be molded with the correct absorbers to begin with.  That's required to ensure a low SNR for the system.

But, why does it matter what the eye can see if it can't see 950 nm at all?

TTFN

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RE: Plastic material which is permeable for IR (infra red) signals

(OP)
IR I do not get the clue of Your last sentence.

As I said - I need a material transparent for Infra Red, but   in parallel it should be les transparent for human eye to hide what is covered inside.


Guys, please excuse me but I am not a material engineer at all so I do know I would sound as total newbie, which in the end I am

RE: Plastic material which is permeable for IR (infra red) signals

What difference does it make?  If I see a reddish window on something, I pretty much assume that there's a NIR receiver behind the window.

If I were inclined, I would simply take it apart to see what's inside, in any case.

TTFN

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RE: Plastic material which is permeable for IR (infra red) signals


The gentleman may want the parts behind to be hidden for aesthetic reasons.  A normal user of such devices would not be inclined to see what is inside so would not take it apart.

The gentleman asked how to make it transparent to near IR and opaque to visible light.

Maybe a bit late to help but try Makrolon 2805 or 2405.

RE: Plastic material which is permeable for IR (infra red) signals

Ummmm What makes Makrolon opaque to visible light.

Regards

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RE: Plastic material which is permeable for IR (infra red) signals


I am not sure how they do it but the variants have been developed specifically to transmit near IR and block out visible light.

The spectrum graph for the two variants I suggested suggests theat in the visible light range transmissivity is as follows:

2805
Wavelength:  <700nm, transmittance: 13%
Wavelength:  >700nm, transmittance: 90%

2405
Wavelength:  <700nm, transmittance: 2%
Wavelength:  >700nm, transmittance: 90%

Contact BayerMaterialScience for more information.

RE: Plastic material which is permeable for IR (infra red) signals

I don't need to. I worked for Bayer as a Market Development Engineer for Engineering Plastics for several years and spent a few months training in their labs in Leverkusen.

I have the manual at hand now but cannot scan the page and the graph, so I will quote word for word the text.

Quote

"Bayer Thermoplastics Technical Ring Binder.
Makrolon Propertes 2
2.1.1.2 Optical Properties
A knowledge of the optical properties of Makrolon is of considerable importance for it's applications in lighting engineering and optics etc.

The graph in Fig. 1" (not scanned into here) "gives a general idea of the transmission of Makrolon in the ultraviolet, visible and infrared ranges.

It can be seen that in the ultraviolet range light is absorbed totally with wavelenghs of up to approx. 275nm.

The light transmission the increases progressively with the wavelength, reaching a value of 85-89% at the beginning of the visible range above 400 nm; it then remains more or less constant up until the beginning of the infrared range. The light transmission diminishes with increasing wall thickness."  

Makroln 2800 is a medium to high viscosity injection moulding grade.
Makroln 2400 is a medium to low viscosity injection moulding grade.
The 5 instead of a 0 for the last digit of the code indicates an additive to enhance mould release.

Makrolon is Bayer's trade name for their polycarbonate. There are probably now about 20 manufacturers of PC (polycarbonate) throughout the world. Lexan by GE is the other long standing well recognised trade name.

PC was mentioned as a possible material very early in this thread by Demon3 who is someone with excellent knowledge of the subject.

Dyes opaque to visible but transparent to IR was mentioned by Pud in a very early post. Pud also has a very good knowledge base, especially on processing, but also on available materials.

That is how Bayer, or anyone else makes their PC or any other normally transparent to visible light plastic opaque to visible but retain their IR transmission characteristics.

Natural colour PC is reasonably transparent to some parts of the IR spectrum, especially in the 700 to 1600 nm range where it transmits about 80% in thin sections.

To do his right you need to know:-
1) The specific spectrum of the light to be transmitted.
2) The transmission of the naturally coloured plastic in that wavelength band.
3) The transmission of dye formulation in the visible and IR in that wavelength band.

Any previous sarcastic remarks were intended to discourage a response that required this type of reply to refute misinformation. Obviously it did not work.

End of lesson.


 

Regards

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RE: Plastic material which is permeable for IR (infra red) signals

Opps

I forgot to credit IRstuff's very relevant and knowledgeable contribution re wavelength band also.

Regards

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RE: Plastic material which is permeable for IR (infra red) signals

Part of the problem appears to be sloppy terminology.  "Opaque," in optical parlance, implies NO transmission.  Most, if not all, NIR transmitter covers are "clear" red, i.e., they will look red with bright backlighting, and while dark, they are not "opaque."  

That said, they are usually sufficiently dark enough to prevent the average person from seeing through the window into the circuitry.  That said, anyone truly interested in the circuitry will simply remove the cover, or, use a NIR configured-camera to see inside.

TTFN

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RE: Plastic material which is permeable for IR (infra red) signals

Opaque is indeed no transmission.
Translucent is transmission with light being scattered so that form cannot be seen, such s frosted glass.
Clear means al light passes straight through with no scatter.
Colour means some parts of the spectrum of visible light is absorbed and some passes through or is reflected.
A coloured tint is when some part of the visible spectrum is transmitted, like sun glasses.

IR receiver lenses are normally a dark red tint with quite low transmission of visible light, but good transparency of IR light in the required wavelength band, but they could be clear or opaque at visible light wavelengths either by the natural colour or opacity of the base resin or by an colour od dye or pigment that is still transparent in the required IR wavelength band.  

Regards

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RE: Plastic material which is permeable for IR (infra red) signals

The questioner asked specifically:

"Can anyone tell me what plastic material shall I use for device with IR antena(reciever)?@

Followed by:

"it should be LESS transparent for human eye to hide what is covered inside."

I therefore suggested a material that would fulfil this criteria, in the belief that this would give the questioner an option to look into, and that if they required more information to contact Bayer.

I did not imply that I knew everything about it or that that is the ONLY material to use.  In fact I suggested the opposite, that I have limited knowledge of the subject.  The last thing I intended was to tell the questioner what to use.  They should make up their own mind based on as much information that they have available.

If it is for secrecy resons then yes, a fully opaque material (to visible light) would be more appropriate.

I had also seen that PC was mentioned earlier but I thought I would add some additional information.  Now further information has been added by other posters it is even better.

I suggetested the poster contact Bayer as they would have received exactly the information that you posted and that I have in front of me.

RE: Plastic material which is permeable for IR (infra red) signals

But your transmission figures were wrong in fact. They might be correct for a specific colour of Makrolon, but that was missing and it was incorrect to suggest it as a property of the grade in general.

I find it good practice to not recommend brand names unless there is no option. I also find it good practice in a "non commercial" technical only forum to recommend several prominent suppliers or a variety of suppliers.

I also try to avoid such lengthy replies unless necessary. Sadly this case became necessary to refute incorrect information.

I also try to aim my reply to the OPs level. In this case he was obviously a bright and competent technician with a decision outside his normal experience. He had done his homework and only appeared to need guidance not high level of detail. He was obviously English second language, so easy to read answers were required. When asked for missing information, he always provided it so he could be trusted to follow a lead without spoon feeding.

Regards

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