More Than Merch.
It's a Scientific Instrument!
Our sunglasses are more than just a statement piece for the fashionable scientist; they are a scientific instrument. The key to their functionality lies in their polarization, which simply means only light with one orientation can pass through them. Most natural light sources are understood as non-polarized light, since the wavelength of the light has multiple directions. However, when filters are applied to light sources, they only emit light in one direction, creating polarized light. For example, standard screens, such as TVs or computer screens, use tech that requires polarized light for its functional principle.
Polarized Sunglasses as Polarizing Filters
Our journey with polarized sunglasses began when we sought a more efficient way to test material stress in VCM polymer samples. Initially, this involved a complex setup with different filters and a stationary light source. However, the rapid and straightforward formulation development offered by VCM inspired us to find a quicker solution for material stress testing, leading to the creation of our unique sunglasses.
The setup is simple: all you'll need are your polarized MeltPrep sunglasses, a computer screen as a polarized light source (or a smartphone if you're on the go), and a specimen that causes birefringence.
Some substances rotate light when it passes through them. This can be a material property for crystals or induced by internal stresses in transparent plastic components. It makes the invisible visible and is called birefringence. Try stretching or slightly bending a plastic part between the glasses and the screen. Simple plastic films result in colorful spectacles. Testing material stress has never been this easy!
During molding, the materials soften and flow into the shape defined by the VCM Tool. The image below shows two samples produced with a VCM Bar Tool at 10x40 mm using pellets as a starting material. The fusing process depends on the material's flow properties and relaxation behavior. To the naked eye, both Ethylene Vinyl Acetate (EVA) samples looked identical. However, when analyzed with the polarizer setup, remaining internal stresses were revealed in the sample processed at a lower temperature. The same processing time was sufficient at a higher processing temperature to relax the sample's internal stresses. Internal stresses can be advantageous or disadvantageous, depending on the application. For instance, internal stresses are sometimes purposefully planned into the manufacturing process to counteract stress during the application and make materials even stronger as they gain extra strength when designed in the appropriate direction. Internal stresses can cause stress nucleation and crystallization of materials.
These are some common polymeric materials that show photoelasticity. Did you find one more? Please submit your material here so we can add it to the list.
Releasing Stress with Heat
Internal stresses can be released by tempering. For this, the materials need to be brought to temperatures close to their glass transition temperature. The example below shows safety glasses, which are typically manufactured with transparent polycarbonate. When viewed through a polarizer, they appear colorful due to residual stresses introduced by fast cooling rates during manufacturing by injection molding. The example shows the same pair of safety glasses before and after tempering (t=2 hours @20 °C).
Common materials that experience birefringence are transparent plastics with internal stresses. These internal stresses can be a permanent occurrence in injection molded plastics, as well as be introduced when the material is stretched. Seeing the birefringence in molded plastic parts can help us understand and visualize how they were manufactured.
In pharmaceutics, visualizing birefringence is additionally utilized to distinguish crystals under a microscope. In the case of tiny crystals, the polarizer can also be fitted between the sample and a microscope. With this, you have everything you need to learn more about the sample you have generated.
Are Your Sunglasses Polarized?
Find out! A simple test with a polarized light source can reveal whether your glasses are polarized. Hold your glasses in front of a screen and rotate. When the field of view through the glasses darkens at a specific point, you’ve found the standard orientation (90°) between the light source and the polarizer of your glasses and can surely say that your sunglasses are polarized.
If polarizing filters are a scientific instrument, why are they so common in sunglasses?
Polarizing filters, like the glass of our sunglass lenses, can be used as scientific instruments. However, polarizers are a common feature in so many sunglasses on the market because reducing the light input to light coming from a single orientation also reduces the glare and light reflections that strain our eyes. They are popular amongst fishers and photographers to reduce glare and maximize the visibility of their points of interest.
Next time you want to go outside or test a plastic component's stress, grab our MeltPrep sunglasses – they're more than shades, they're your window into the world of scientific exploration!
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Embrace creativity with polarization
Frugal Science is a discipline that requires creativity and ingenuity. It is not always about having the newest and most expensive materials to contribute meaningful scientific content to the knowledge pool. Often, it’s about connecting the dots in new ways. Let the examples shown above inspire you to get creative with polarizing filters!
Fuel your inventive spirit by participating in our Polarizer Contest. It's simple! Click the button below to submit a photo showcasing your creative use of polarizing filters. Your unique perspective might allow you to win a VChamber Family for your lab. Learn more about VChamber
No need to worry about photography skills – just upload, and our creative team will sprinkle some magic with photo editing. Every idea is valuable, and we can't wait to see what you've got!