ARRK AND ACOMON CO-DEVELOP INNOVATIVE TRANSPARENT RESIN RESISTANT TO UV YELLOWING

Specializing in the production of optical monomers, Italian based ACOMON joined the Health Division of Mitsui Chemicals, ARRKs parent company, in 2011. With the success of acquisitions of companies like ACOMON and ARRK, Mitsui Chemicals intends to create synergies between its subsidiaries resulting in fresh innovative results. Thus, ARRK, a specialist in rapid prototyping and low-volume production, will rely on ACOMON’s expertise in polyurethane (PU) resin formulation to expand commercial opportunities in optical applications. For this Case Study, we head over to ARRK Europe, where the teams at ARRK and ACOMON, masterfully collaborated to develop and innovative transparent resin resistant to yellowing caused by UV radiation.

A TRUE COLLABORATIVE CO-DEVELOPMENT PROCESS

Faced with the global COVID-19 pandemic, the development of RAVolution™ LH transparent resin took over 3 years to complete. This process began when ACOMON took its RAVolution™ F4 resin as a start off point. ACOMON took it upon themselves to reformulate its chemical composition to flawlessly comply with the requirements of the Vacuum Casting process as well as meet the short deadlines offered in rapid prototyping.

Opposed to RAVolution™ F4’s resin conditions, ACOMON faced the challenge of reducing the mixing time of its components. Further, this was followed by shortening the polymerization phase from the usual 20-40 hours to just 3 hours. This was followed by several months of testing the aging of the resin, including a 4-month long outdoor environment examination.

ACOMON’s main interest in this collaboration is to be able to test new materials in real product conditions. As for ARRK, the main benefit of this collaboration is to confidently offer our customers transparent resin with notably improved performance unprecedented in today’s market.

2019 - 2022

AN INNOVATIVE TRANSPARENT RESIN, IDEAL FOR OPTICAL APPLICATIONS

A transparent PU Resin Resistant to UV Yellowing

RAVolution™ LH resin does not absorb UV-A radiation (wavelength between 315 and 400 nm). It offers excellent transparency with a transmission rate of over 92%. Black curve: RAVolution™ LH resin. Red curve: competing PU resin

« UV-A AND B ABSORPTION TEST

TESTING OF RAVOLUTION™ LH RESIN UNDER REAL ENVIRONMENT CONDITIONS (BUILDING ROOF)

The yellowing index of RAVolution™ LH resin is less than 0.3. A brief yellowing of the material is measured in its first days of use. It reaches its maximum on the 10th day and recedes from the 84th day on. The appearance of the material is stable over time.

Black curve: RAVolution™ LH resin »
Red curve: competing PU resin »

A PU RESIN WITH INTERESTING PHYSICOMECHANICAL PROPERTIES

In addition to the excellent transparency and low yellowing properties, RAVolution™ LH resin has the following characteristics:

Refractive index: 1.513
Strong impact resistance:
- Hardness = 98 Shore D
- Bending modulus: 3300 MPa

High thermal resistance: thermosetting polymer
Clear colorless resin. Mass coloration and dip-dye degradation
Light material. Density = 1.1 g / cm3

WHAT IS REFRACTIVE INDEX (IR)?

The refractive index of a lens measures how light is scattered through it. Meaning, the ability to deflect light from its original trajectory. A high IR lens provides a strong correction, which reduces the thickness of the material and as a result the weight of the product.

MULTIPLYING THE POSSIBILITIES OF OPTICAL APPLICATIONS

Andrea Vecchione, R&D Manager at ACOMON, a specialist in transparent polymer synthesis, explains:

“Our RAVolution™ LH resin is very promising. The stability of its properties, in particular UV transparency, is arousing the interest of manufacturers for prototypes of optical parts in the medical, automotive, electronics, and even solar sectors!”

THE PERFECT PU RESIN FOR LOW-VOLUME PRODUCTION

We at ARRK continue to notice our customers’ expectations to utilize prototypes as final products. With this, the longevity of material properties then becomes a hot topic. Offering transparent products with a reduced likelihood of turning yellow guarantees our customers a longer product lifespan compared to traditional materials.

RAVolution™ LH PU resin has been arduously tested and adapted to ARRK’s vacuum casting process. Thanks to RAVolution™ LH PU’s unique chemical composition, the VC process is noticeably less aggressive for the silicone mold when compared to competing market resins. This increases the cycles of use ARRK’s silicone mold resist- up to 25!

As an added bonus, due to mold spacing capacities, the unit price of low-volume vacuum casting parts is significantly lowered. Depending on the size of the mold and the parts, up to 2.30m at ARRK, our possibilities of running series of hundreds or even thousands of pieces on a single order are greater than ever.

A TRANSPARENT POLYURETHANE RESIN EXCLUSIVELY AVAILABLE FROM ARRK

Currently, the RAVolution™ LH transparent resin is exclusively offered to ARRK customers and readily available in ARRK Europe’s vacuum casting compatible material list. The manufacturing process is fully functional and produced in its entirety at ARRK France’s site.

TOWARDS AN ECO-FRIENDLY VERSION OF RAVOLUTION TRANSPARENT RESIN

Andrea concludes:
“Market demand for so-called ‘ecological’ materials, although more expensive, is growing strongly. Their marketing takes longer as they’re subject to a certification process.

There are 2 axes of development of a “green” resin. At ACOMON, from our ISO 9001 and 14001 certified site, we are able to work on the 2 options:

Develop a chemical formula composed of 30% bio-based ingredients (corn for example). They are more expensive but already available on the market.
Design a material whose overall manufacturing process is energy-efficient, i.e., reduction of CO2 emissions compared to conventional resin.

Today, we are focusing our research on the second option, which is currently sought after by our customers.”

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ARRK AND ACOMON CO-DEVELOP INNOVATIVE TRANSPARENT RESIN RESISTANT TO UV YELLOWING

A TRUE COLLABORATIVE CO-DEVELOPMENT PROCESS

2019 - 2022

Testing of RAWolution™ F4 resin at the Arrk workshop.

ObservaTion of the Vacuum Casting Process

Reformulation of the resin

Testing at the ARRK Workshop

ARRK EuropE Approves the formula of RAVolution™ LH resin.