Which commercially manufactured adhesive has the lowest thermal expansion coefficient? 1

Overly broad questions lead to useless answers

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This is not overly broad question as only one adhesive can have the lowest coefficient of thermal expansion (CTE). There are tables of CTE for various materials, but I was unable to find one for adhesives. Also, I appreciate the link to epoxies, however, epoxies are known to have raltively high CTE in range of 10 to -6 compared to some UV cured adhevsives which have CTE in range of 10 to -7 (particularly those made for bonding optical elements).

As you mention - UV adhesives are used in optical elements because the elements are transparent to UV, allowing the adhesive to cure. Are you bonding optical elements?

Mainly the film thickness is small enough and the elasticity is large enough that the CTE is not important. One does need to be concerned with strength internal to the adhesive and the bond strength to the substrate and the differential thermal expansion of the parts being bonded.

How did you conclude you need the only adhesive material that has the lowest CTE in the entire world?

Good luck finding adhesive CTE data. Its typically not generated or used for adhesives. Exceptions are spacecraft that have to maintain dimensional stability in orbit with large temperature ranges. Try searching NASA spacecraft documents.

Your question is overly broad because you gave zero information about strength, substrates, environment, etc.

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@3DDave I'm working on a physics measurement experiment and I'm trying to bond layers of bare optical fibers together so they don't vibrate when the experimental instrument is being moved. I can use UV cured adhesive because each layer of fibers will have adhesive applied from the top, and can be cured from the top before another layer is applied. However because optical fiber is made of glass which has very low CTE and the fiber is very fragile, so it is unlikely to overcome forces of elasticity of the adhesive, therefore I need to find an adhesive with ultra low CTE. I wrote in the question that I'm looking for one which has the lowest known CTE because glass fibers have CTE 5.5 x 10 to -7, which is lower than any adhesive that I know of. However, I have seen some papers about experimental adhesives made from molecules of silica with ultra low CTE, so maybe some company is manufacturing commercially such an adhesive.

Run a test. Or will it come out you already have tested and some material you tried failed? If this is on a college campus then there should be an engineering materials department who can look at the geometry of the fiber and tell how strong the fiber is. There are some highly elastic adhesives - like 0.3 psi per degreeF which can be reduced farther by foaming or makeing the bond line thicker.

You have omitted the temperature range.

I talked to the engineering department and it was of no use, they started googling for adhesives, which I have already done . However, I devised my own test of impact of adhesives on the fiber by measuring changes in polarization in the fiber due to stresses caused by the thermal expansion. And the bare fiber without any adhesive had the lowest changes in polarization due to thermal expansion but the highest sensitivity to vibration, while the best adhesive at my disposal had exactly the opposite effect, albeit, the change in polarization due to thermal expansion was smaller than the change caused by vibrations. So while this adhesive is not optimal it is better than none at all. But I'm hoping that maybe we have someone on the forum who is an expert on adhesives and will be able to give some advice.

The shift from concern about fiber strength to fiber deflection - would have been obvious at first that you would not find an adhesive that was an exact CTE match for the fiber if no thermal effects at all were allowed.

Are you trying to stabilize a q-bit?

No, not q-bit, but rather the changes in polarization and phase of light are my main concern. I'm building a new type of interferometer, and when the fiber elongates (or shrinks) the light coming out of the fiber has a shift in phase and when it deflects the polarization changes, and both of these factors affect the rate or intensity of interference. So I'm trying to reduce or eleminate those factors that affect polarization and phase.

A typical solution is to control the temperature very precisely, often by elevating the temperature, eliminating the effect of thermal differential expansion.

In my setup precise control of temperature will have severe limitations due to fact that the interferometer must be mobile, so dragging along batteries and temperature controller is not possible. That's why I need ultra low CTE adhesive.

You are far better at adding design constraints than I am at guessing what you won't allow next.

Best of luck.