Recorded October 16th, 2012
Presented by RTP Company
Color extends beyond what you can see to the realm of light control. Learn how to manage light through diffusion and attenuation along with practical applications for extending light manipulation into the UV and near IR spectrums. Tim Duncan, color veteran at custom compounder RTP Company, will be your guide as he explains a variety of light controlling concepts during this illuminating webinar: Diffusion and transmission, Attenuation and filtering, UV, visible spectrum, and near IR applications, Laser marking and laser welding, and Combining light control with visible color. Do not miss this opportunity to explore the world beyond simply coloring plastics.
Questions and Answers
Q: How is black on black laser welding easier than other options?
A: Black is one of the highest volume colors in our industry and the most common black colorant is a very effective absorber for NIR energy. The challenge is the laser transparent black, but this is well understood and has a long history of success. There are several options depending on the polymer and compound characteristics.
Q: I generally need high flame retardant resins (5VA) but I find it hard to find resins with these other capabilities you’ve discussed that are also very flame resistant. Comments?
A: The challenge is related to the specific flame retardant performance requirement, the polymer or compound used, and finally the aesthetic or optical property needs. The greater the complexity of the material, the more limited the options for coloring and other appearance parameters. RTP Company addresses these demands daily and more often than not we have an acceptable solution.
Q: Acrylics and polycarbonates frequently have anti-scratch coatings. Are there special considerations in laser marking these coated products? For example, undesired release of the coating?
A: The anti-scratch coatings can be an issue depending on the specific coating, the polymer and the base color. There are options to reduce or eliminate the potential for release of the coating. When possible, we prefer to assist in the coloring of both the base compound and review options for the coating.
Q: What is the best material for a clear cover, to laser weld to a black glass filled PBT?
A: The best material depends on the environmental and mechanical property needs of the cover, but polycarbonate has been used successfully with PBT.
Q: What family of polymers is the most chemical resistant, either transparent or translucent?
A: There are chemically resistant polymers both transparent and translucent, but for extreme resistance the answer is opaque. Generally, crystalline (opaque to translucent) resins are more chemically resistant than amorphous (transparent) resins.
Q: If you need a release agent in your part, what are your options for laser welding?
A: It will depend on the resin system, but migratory release agents should be avoided.
Q: It’s been indicated greater than 40% is good for contrast; for reference what is the approximate contrast for black on white & black on yellow?
A: Typical contrast for black on white and black on yellow is 55-60%.
Q: Can the depth of the foaming in etching be controlled to tight tolerance?
A: Precision for laser marking is controlled by both formulation and marking parameters. Specific tolerances will depend on the polymer compound, formulation, type and laser marking parameters, however, significantly narrow tolerances have been achieved with very fine marking of small parts.
Q: Can laser welding be used to weld a thermoplastic to elastomeric rubber parts?
A: Yes, it is possible to weld dissimilar polymers, but each application and material combination should be reviewed for the best possible outcome. A common practice is molding elastomer seals to rigid housings.
Q: What do you recommend for accelerated testing of a LED transmitting polymer to assess light fastness form both the LED and ambient light (interior) and weatherability (outdoors)?
A: LED’s do not contribute UV energy that would degrade the polymers used for lighting applications. The primary source for UV degradation of the polymer is outdoor light. The specific test parameters for accelerated testing vary greatly with application. We generally suggest testing that will most closely match the expected real world exposure.
Q: Can flame retardant polycarbonate be laser welded?
A: Yes, but it depends on the type can concentration of the flame retardants used for the laser transparent layer. The laser absorbing layer has greater options.
Q: Do you provide samples of different diffusion levels in stock?
A: Yes, we can provide samples in a variety of forms – pellets, molded plaques or extruded sheet. However, we prefer to discuss your application and assist with material recommendations to reduce your development time and costs.
Q: Do you have a sample of something that has been laser welded that you could show us?
A: Yes, we can demonstrate and share examples of welded materials, but we prefer to discuss your specific application to more appropriately address your needs and provide more personal support.
Q: We make lighting fixtures where I work. What resins/colorants are available that diffuse light & have maximum light transmission?
A: Any clear resin can be made to diffuse light more effectively while maximizing transmission. Specific selections should be based on a detailed discussion of your application and goals. White is the most common color, but most any color can be produced. However, color does reduce transmission, regardless of hue. White will always be the choice for maximum transmission.
Q: Are there translucent white colorants that can be added to polycarbonate that don’t degrade/yellow at 120 deg. C or more?
A: Yes, we have options for higher heat applications that are sensitive to yellowing.
Q: But using acrylic is more possible to break it?
A: PMMA or acrylic is more brittle than other amorphous resins, but it has some of the best clarity available. We are happy to assist in material selections and are prepared to fully explain the benefits and limitations of each.
Q: Masterbatch can affect the dimension and material contraction?
A: In general, coloring by masterbatch does not have significant influence on shrink or dimensional stability. Some colorants can have an influence, but we formulate to minimize this issue when dimensional stability is a critical factor in your design. Most tooling issues are influenced by host polymer choice rather than coloring. We are happy to review tooling and suggest polymer and coloring solutions.
Q: What is the thinnest specimen that can hide the ‘hot spots’ of an LED source?
A: The answer depends on many factors. Distance from the LED source, distance between the individual LED’s if there are multiples, transmission limitations, etc. However, most applications are between 0.5 and 1.0mm in thickness.
Q: What is the highest reflectivity required in the LED lighting applications?
A: Our highest reflectivity products are 97-98% reflective. Most applications are 95-97%.
Q: Is it possible to increase light transmission for thermoplastics such as Ultrason PESU by adding additives etc.?
A: Unfortunately, it is not possible to improve the transmission of the base polymer with the addition of additives. It is a physical characteristic of the particular polymer. Any modification to diffuse the polymer will reduce its direct transmission from the unmodified state.
Q: Is an annealing process required after laser welding?
A: In many cases it can improve the strength of the weld. Especially when welding dissimilar polymers. However, many applications of welding like polymers do not require annealing
Q: Are your resins UL approved?
A: We have many UL listed materials and our Flame Retardant team is working daily to provide new options. We would be happy to review your application and suggest the best option from our currently approved grades or work with you to develop something new.
Q: Do the laser weldable and laser marking formulations allow the use of regrind?
A: While this is technically possible, there are significant concerns, specifically with the laser transparent material. We would be happy to discuss your specific application and help to highlight areas of concern and offer suggestions for material handling.
Q: Are there patent infringement difficulties when selecting color combinations for laser welding?
A: We are happy to review specific applications and discuss patent issues for your specific application. RTP Company is very sensitive to both protecting our IP and those of our suppliers and competitors.
Q: Is there any diffusion material that would not require an air gap between itself and the led to achieve a good performance?
A: The air gap is a significant part of the diffusion solution. The change in refractive index between air and the polymer definitely improves performance. We can offer product for direct contact, but they are a compromise for both diffusion and transmission.
Q: Is RTP Company doing UV block in clarified PP amber color?
A: Yes, this is a familiar application and one we are happy to discuss. Most applications require blocking in the UV through 550nm. Thickness of the molded part is a critical part of the discussion and material recommendation.
Q: Have you worked with IC packaging on how to better mark epoxy molded parts? Mold compounds for IC packaging typically is quite stringent on compositions.
A: I am not aware of any activity for marking epoxy boards. Our materials have been developed for thermoplastic applications. We do have options for marking the packaging if this is of interest.
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