Frequently Asked Questions (FAQ)
Let's get straight to it.
Do you have questions ? We have answers. Browse the topics below to find what you're looking for.
#1: How much material do I need to make a sample?
Just the right amount.
The VCM process is lossless. 1 gram powder will result in a solid sample of 1 gram without air inclusions or bubbles. If you work with expensive materials and your material characterization allows small samples sizes you need in general less than 100 mg for your characterization.
Samples with 2 mm in diameter and 1 mm in height would require only a few mg of material.
#2: Who uses VCM Technology?
In pharma 4 out of the top 10 companies, are using VCM for Hot Melt Extrusion developments. But the technology is strongly also used in other industries like food and plastics. We follow our customers' publications and list them on our publication page.
#3: What is the minimum thickness of the sample?
Wide range of choices.
We suggest thicknesses between 0.1 and 10 mm for the VCM samples. Thickness may also depend on the material characteristics.
If you have elastic polymers like TPU (Thermoplastic Poly Urethane) or EVA (Ethyl-Vinyl-Acetate) you can also reach thinner layers in the range of 50 µm for example.
#4: How many layers can you make?
We have demonstrated in the NuvaRing Screening (click to see the publication) a system of 3 layers. We do have some customers working on implants who are evaluating systems with up to 10 different layers. It's important to note that the materials need to be compatible. Adhesion, similar melting points and similar viscosity levels at the processing temperatures are required.
Multilayer Sample with distinct layers and sharp interface(s)
#5: Can the PTFE foils be reused?
Comfortable and easy.
Yes, the foils are reusable. The PTFE Foils are glass-fiber reinforced. That means the Teflon does not flow and keeps its shape. That's why they can be reused several times. As a rule of thumb, we recommend using them 10 times before they should be replaced.
#6: Can I use the VCM technology at constant temperature continuously for several hours?
Made to last.
Yes, there is no inconvenience in using the VCM technology during a long period of time at constant temperatures (i.e. 60 °C). The materials are prepared for a long exposure. You can work up to 200 °C for several hours, while up to 300 °C we recommend using it for short-time operations.
#7: Do I have to clean the VCM thoroughly after operations?
No need to clean.
No more tedious cleaning with VCM. The VCM sample chamber is fully PTFE-lined, adaptable in volume and the separation foils can be simply peeled off after the preparation process. No cleaning is required.
After the insertion of new foils, the equipment is ready for the next preparation cycle. The foils are non-stick and can be wiped down and reused multiple times, making the process even more cost-efficient.
#8: How can I empower mixing via diffusion?
From millimeter to micrometer range.
If you work with heterogeneous materials at large particle sizes and process it via VCM, you will obtain a heterogeneous sample. VCM is not applying mechanical mixing inside the Chamber. We have chosen to fuse multi-colored pellets in the mm-size range with VCM to illustrate the process. Pellets are squeezed and melted together, forming a solid disc without air inclusions but the individual pellets with a sharp interface are still visible.
Pellets (length scale = mm range)
One solid disc,
individual pellets visible.
Empowering diffusion is key to obtain a homogeneous sample out of heterogeneous materials. We can try to reduce the particles’ size by starting with a physical powder mixture. After the VCM processing, the result is better than the previous one but there are still some agglomerates and inclusions which are not completely dissolved. This might be due to insufficient mixing or too large particle sizes in general.
Inhomogenous sample with API crystals.
To empower diffusive mixing, it’s important to obtain a starting material which is homogeneous in the small micrometer range. Our customers usually apply a milling step, preferably under cryogenic conditions. After processing it with VCM the result will be a homogeneous and defined sample that has properties comparable to extruded formulations.
Route 1: Milling
Route 2: Solvent casting
Mixing Powder [5g] and tip of spatula with 100 ml Ethanol.
Let the solution evaporate until a thin layer remains
Another way to empower diffusion is particle dissolution via solvent casting. We can use suitable solvents (ethanol, acetone), let the particles dissolve in it and pour the solution on a Petri Dish. Afterward, we let the solvent evaporate until we obtain a thin thin layer of our materials. The layer is peeled off from the Petri Dish and transferred into the VCM Tool with which a homogeneous sample is obtained after processing.
#9: How do I set the sample height?
With the right amount.
The thickness of your sample will depend on the material amount filled and its solid density. Once you know your material density, sample height can be calculated by using this formula: