Support Archive – MY Polymers

SELECTING THE RIGHT PRODUCT

We recommend using 2 stages for an efficient selection of the right product candidate(s).

Stage 1: Get a shorter list of the candidate products

There are 2 ways to get a shorter list:

1. Define a limited range of relevant refractive index: Go to the PRODUCTS by REFRACTIVE INDEX page. Use the 2 red sliders to define the range of interest. You can move the sliders and see the list of products in the table, which becomes shorter or longer, depending on how you move the sliders. We recommend you select a range a bit wider than the range you actually need.

2. Alternatively, you may select a relevant category of products: Go to the PRODUCTS by CATEGORY page and select the category which seems most relevant. You’ll get a shorter list of products. At this point you may use the red sliders, to focus on a more limited range of the refractive index.

Stage 2: Focus on the best product candidate(s):

Now, that you got a shorter list of products, use the properties listed on the table to guide you in your final selection. Note that the columns include the most important properties: Refractive index (cured state, at both 589 nm and 950 nm), adhesion, modulus, tensile strength, viscosity (in the liquid state, before curing), Curing method, Hardness, and shelf life.
Once you get one or more candidates, you can download the datasheet. Click either the product name (left-hand column) or the right-hand column, marked as a PDF file. The datasheet includes many more details on each product.
Send us a message if you have any technical questions, and we’ll do our best to help in selecting the right product, and answering any questions.

Few tips when selecting products:
The lowest-index adhesives have inferior mechanical properties.
Typically, the lowest index products tend to have inferior mechanical properties (modulus, hardness, tensile strength), compared to higher modulus products. When selecting a low-index material we recommend you look at the modulus as a representative mechanical property.

Adhesion and our adhesion primers:
Excluding some notable exceptions, the lowest index materials also tend to have lower adhesion. (You can see this in the products table).
When important, you may consider using one of our adhesion primers. As this may complicate the production process, consider selecting an Enhanced Adhesion product.

For example, if you need an index of 1.33 AND good adhesion, MY-133-EA with an adhesion of 27 gr/cm should be preferred over MY-133-V2000 with only 9 gr/cm. (However, MY-133-EA has a shorter shelf life, and lower modulus, compared to MY-133-V2000).

Non-UV cured products:
The vast majority of our products are UV cured, but we also have a few moisture-cured, dual-cured (UV or Heat), and pressure-sensitive products.

The moisture-cured (-MC, -AR) products:
The moisture-cured products do not need UV curing (and no inert atmosphere) for curing. Their typical use is as coatings. The MC/AR product are harder and have better adhesion compared to UV products with the same index. For example, MY-133-MC is harder and has better adhesion than MY-133-V2000; and AR-138 is much harder than MY-138.

The Double Cured (DC) products:
Double-cured products are used when a part of the area to be UV cured (or all of it) is shaded.

Pressure-sensitive products:
Pressure-sensitive products are an exception, combining both low indexes (1.33) and very strong adhesion. These are lamination adhesives. They are typically used to laminate films and flat substrates (e.g. in the electronic display industry).

Get us involved in the selection process:
Let us know if we can help!

Send us a message through the website, or send us an email to [email protected]. We try to respond quickly.

You can get us involved at any stage of the selection process, either beginning from scratch, after Stage 1, or after Stage 2.
Even if the selection process is done in the best way, many times it is not possible to zero in on only one single product. Quite often, not all the requirements are well defined. Therefore, it is typical for many first-time customers to focus on 2,3 or even more product candidates, order them, and run their own testing with their own specific target device to determine the final chosen product.

SPIN COATING

The product that is normally used for spin coating is MY-133-MC. The moisture-cured is preferred since it does not require inert curing and it is also the one with the best adhesion to glass and silicon wafers. Below is the spin curve for undiluted MY-133-MC:

Fig. 1 Spin curve of undiluted MY-133 MC polymer. Measured with 30 seconds spinning time and glass (BK7) substrate.

UV CURING AND INERTING

of low refractive index UV-cured polymers:

How to get good curing? How to get good inerting?

Inert Atmosphere Guide
The UV curing of acrylate monomers is a free radical polymerization process in which UV radiation is absorbed and activates a certain type of molecules, photoinitiators. The activated photo initiators normally break into reactive species called “free radicals” that start the polymerization of the acrylate groups. The free radicals are also very reactive towards molecular oxygen. Oxygen captures the free radicals to form stable peroxides and the polymerization thus stops. The continuous influx of oxygen into the coating layer during the irradiation process inhibits the polymerization reaction at the top surface.
The thickness of the inhibited layer is a function of the reactivity of the formulation and function of the rate of irradiation. A high dose rate of radiation helps to reduce the thickness of the non-polymerized layer. Longer irradiation time normally does not help and cannot substitute the need for intense radiation.
The most effective way to eliminate oxygen inhibition is to work in the absence of oxygen. That can be achieved by either working with a cover foil over the fluid. This is typically the situation in a lamination process. In other cases, working with an inert atmosphere is the better solution. Nitrogen is the most frequently used gas. Other inert gases are Argon and carbon dioxide.
Other less frequently used solutions are irradiation under a vacuum or under a layer of water.

Note: Inerting is only necessary at the instant of irradiation. No need for inerting before or after irradiation.

Most equipment manufacturers offer optional inert curing systems which are based on passing the substrate through a chamber under a positive pressure of nitrogen and irradiation through a quartz window.
For smaller lab installations, one can easily build an inert chamber. The following schemes demonstrate a few optional designs plus Do and Do-Not-Do principles.
The general idea is not to use a free flow of nitrogen over the object because that causes a Ventury dragging of air onto the surface. As much as possible, the flow of nitrogen has to be in a semi-closed system. A clear foil can replace the expensive quartz window. The family of FEP or PFA (such as Teflon FEP, and Teflon FPA) are the most suitable since they have a high-temperature resistance and perfect transparency through the whole UV/Vis./Nir IR range. These films can be used with highly intense radiation sources. In the case of lower-intensity sources, a simple polyethylene foil (sandwich bag material) will suffice. It is also perfectly clear through the whole UV and Visible range. Almost any other clear film or sheet will work as well. Some plastics such as PET and polycarbonate are only transparent in the UV-A and visible, and they are also fine since all MY Polymers products are activated by 320-390 nm (UV-A) radiation.

Picture 1: Do and Do-Not-Do in fiber bonding:

Picture 2: Situations that do not need inerting:

Picture 3: A scheme of an inerting tray with a transparent EFP foil being used for curing coated glass plates. The following picture shows the actual device.

Picture 4: A simple inerting tray with a transparent EFP foil being used for curing coated glass plates. The construction materials include wood pieces, metal foil, FEP foil, masking tape, nails, epoxy adhesive (to seal cracks), and plastic tubing. Nitrogen enters from the rear part (green tubing). The tubing serves to pull the tray back and forth on the conveyor belt. Aluminum strips surround and protect the transparent foil from overheating.

HOW TO DILUTE

Smaller thicknesses of the spin-coated layer are attainable with the dilution of the MY-133-MC polymer with a proper solvent. It is soluble in many common medium polarity solvents, but only above a certain concentration. The dilute solution is turbid and will eventually separate into two layers. In the table below you will find the suggested list of solvents for that purpose. You need to use a mixture of a fluoro
solvent with any one of the other mentioned solvents.

The table (below) shows the limits of solubility of some solvents arranged by their relative volatility. The data shows the minimum level of the product in a solvent below which the solution becomes turbid. Complete solubility is only reached with fluorinated solvents such as Freon 113 and the various Freon substitutes such as HFE-7100 (3M) or Vertrel (DuPont). The solubility is also obtained with mixed solvents containing 20-50% of the fluorinated solvents. For instance, 50% each of methanol and HFE-7100.