Frequently Asked Questions
- Reflectance, Transmittance & Fluorescence Standards & Products
- Materials & Coatings
- Integrating Spheres
- Measurement Services
How stable is Fluorilon-99™ to aging?
Under ‘normal’ conditions, Fluorilon-99W™, as with any sintered PTFE product, will have indefinite stability. The only causes of instability are contaminants introduced into the material from the environment in which it is used. Advanced aging studies on sintered PTFE such as Fluorilon™ have indicated stability in excess of 100 years.
How stable is it with UV energy/time?
This again depends on cleanliness. If the material is kept clean, the UV stability is greatly enhanced. Extensive research has shown that UV radiation above 350 nm has little, if any, effect on Fluorilon™ and other sintered PTFE materials if they are kept clean. Fluorilon™ itself is not affected by UV; the contaminants are.
What kind of effects happen with temperature/reflectance? Do high or low temperatures cause any difference?
Sintered PTFE such as Fluorilon™ has been used extensively as a standard for spectrophotometers and spectroradiometers in low-earth orbit space platforms. Under such conditions, it experiences temperatures from about 4K to about 450K. While the expansion and contraction of the material may cause minor changes in reflectance, there are no literature citations (and the literature is extensive) that indicates that there IS a change.
What kind of cleaning is recommended for Fluorilon™?
The best way to clean Fluorilon-99 is to sand the optical surface with 220 grit waterproof silicon carbide paper (we suggest 3M brand) on a flat surface, using a stream of running water to clean the abrasive. For volatile contaminants, a vacuum bake at 10^-6 torr at 90°C for 24-48 hours is recommended.
What kind of known changes are happening to the standard in a box in a stock?
None that we’ve seen. It depends where the box is, however- if there are chemical fumes around, these may be absorbed by the Fluorilon™ and affect its performance in the UV (under 300 nm) and in the NIR (above 1500 nm).
What are the effects of humidity?
Humidity has no effect unless you are working in the NIR where water bands may be observed. This comes from surface adsorption that will occur with any
material. Fluorilon-99W is, itself, very hydrophobic.
How fast does Fluorilon-99 become yellow?
Under typical laboratory and field conditions, Fluorilon™ will not yellow. Only the contaminants that it absorbs will yellow. PTFE- the starting material- is a remarkably stable material but any porous substance such as Fluorilon™ or other low density sintered PTFE materials will absorb organics from the environment. These materials will degrade, causing the yellow coloration, but this will only occur under very harsh conditions. Remember, this is an optical material and should be treated as you would any other reflecting or transmitting optical component.
Can Fluorilon-99 be sprayed onto a substrate?
Fluorilon-99 is a monolithic thermoplastic. It is not a coating and thus cannot be applied like one. However, thin sheets of Fluorilon-99 can be prepared and adhered to substrates with certain adhesives. While this procedures is not recommended, in certain cases it can be successfully employed.
When should I use Avian-D and when should I use Avian-B coating?
Avian-D was initially designed to be a coating used outside and in adverse environmental conditions. However, we have modified its formulation to also make it an excellent coating for laboratory applications. The primary difference is in the reflectance in the UV (below 350 nm) and in the NIR (above 1200 nm). Avian-B coating is a better coating to use if your application requires high reflectance below 350 nm or above 1200 nm. Other than those spectral ranges, the coatings are essentially equivalent when applied correctly.
Why is Avian-B coating shipped without the alcohol?
The primary reasons are safety and cost. While the proper denatured alcohol (which we specify) is readily available, the cost of shipping coating with the alcohol is prohibitive. We would rather keep our prices low and specify the alcohol to use and give mixing instructions. And, since the events of 2001, shipping flammable materials has become a very difficult matter to arrange. The good news is that each liter of Avian-B coating that you purchase yields almost two liters of coating that can be sprayed. In addition, the shelf life of the pre-mix is quite a bit longer than the mixed coating, and small portions can be made for each coating job as needed.
What is the shelf life of Avian-B and Avian-D coating?
Unopened, the shelf life of Avian-B coating is appx. 2 years. This is also true of Avian-D. Once opened, if stored away from air (under nitrogen), the coatings should have a shelf life of at least 6 months. Once mixed with alcohol, the Avian-B coating should be used within 3-4 weeks. Once mixed with the activator, Avian-D has a pot life of 2-3 days.
What substrates are best for each coating? What is proper surface preparation?
Avian-D can be applied to just about any substrate, while Avian-B adheres best to metal surfaces that have been slightly roughened. Roughening of any substrate increases the adherence quality of both coatings.
What are temperature limitations of Avian-B and Avian-D?
Avian-B and Avian-D have similar thermal properties in that degradation of the reflectance , especially in the UV and blue regions of the spectrum, begin to degrade if the sprayed coating is maintained above 85° C for more than a few minutes. The degradation is not often visibly apparent, as the coating degrades from the substrate outward. If subjected to temperatures above 120°C for extended periods, a distinct yellow color will appear.
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