Whitepapers

The problem of ice build-up in an engine or on the leading edges of a plane is a significant problem in the aircraft industry. Ice build-up can affect many aspects of flying such as lift, drag, and thrust. Under the direction of Pratt & Whitney in 2004, the Department of the Army, Engineer...

The problem of ice build-up in an engine or on the leading edges of a plane is a significant problem in the aircraft industry. Ice build-up can affect many aspects of flying such as lift, drag, and thrust. Under the direction of Pratt & Whitney in 2004, the Department of the Army, Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, NH, U.S, performed adhesion strength tests designed to measure the adhesion strength of ice to several different commercially available ice-phobic coatings. The results show that the silicone material, R-2180, dropped the adhesion strength by a factor of 40 over bare steel and aluminum surfaces. These results were the lowest mean failure stress that CRREL has ever seen at 37 kPa while Teflon® was previously the lowest tested value measured at 238 kPa.

The unique chemistry of silicone polymers are customizable to create a variety of material types with a specific properties. The polymer properties have proved useful in a number of applications, including drug delivery. Silicone polymers represent the basis of all silicone systems, adhesives, gels, elastomers, and resins. Silicone polymers are...

The unique chemistry of silicone polymers are customizable to create a variety of material types with a specific properties. The polymer properties have proved useful in a number of applications, including drug delivery. Silicone polymers represent the basis of all silicone systems, adhesives, gels, elastomers, and resins. Silicone polymers are created via acid or base catalyzed polymerizations of silicone cyclics and endblocking silicone molecules. The polymerization process is an equilibrium reaction that yields both starting materials and a polymer distribution of varying molecular weight. The subsequent processing and testing of these polymers is critical to their performance in silicone systems. Lack of proper processing may lead to variable physical properties in elastomer systems. These variations may, in turn, affect the system’s function in drug delivery systems, influencing factors like drug permeation rates. The paper critically evaluates the polymerization process and subsequent purification processes that are critical to producing consistent silicone systems.

The Aerospace Industry has used silicone adhesives and coatings for over five decades. Silicones ability to maintain its elasticity and low modulus over a broad temperature range, –130 to 260°C, provides excellent utility in space, where spacecraft are often exposed to these extreme temperatures. The National Aeronautics & Space Administration...

The Aerospace Industry has used silicone adhesives and coatings for over five decades. Silicones ability to maintain its elasticity and low modulus over a broad temperature range, –130 to 260°C, provides excellent utility in space, where spacecraft are often exposed to these extreme temperatures. The National Aeronautics & Space Administration (NASA) and the European Space Agency (ESA) recommend testing low outgassing materials per ASTM E-595 prior to use in space. These materials should meet the specifications outlined in NASA SP-R-0022A and ESA PSS-014-702, which require a maximum Total Mass Loss (TML) of 1% and Collected Volatile Condensable Material (CVCM) of 0.1%. TML and CVCM levels higher than this specification can cause outgassing and subsequent contamination of expensive equipment. Although a standard for many years, many in the industry question whether these specifications are low enough.

Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been...

Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been used throughout the last decade1, 2. The high light flux and associated heat proved too much for the traditional epoxies. Data confirms silicone encapsulants/adhesives provide longer optical transmission life than epoxy encapsulants 3. Almost all optical devices have some interaction with UV wavelengths. Manufacturers of Blue LEDs with wavelengths near 405nm, and other LEDs that emit wavelengths deeper into the UV (365-399nm), have concerns about the effects of this radiation on the light transmission of the encapsulant over time. LCD and sensor devices may have UV radiation from the sun to contend with. This paper looks at many different encapsulants/adhesives, silicone, epoxy and acrylate, for their change in optical transmission due to a 680- 68000J/cm2 dose of radiation with the following spectral output: 34% in the UVA (320-399nm), 17% in the UVB (280-319nm), and 49% concentrated at 405nm and 450nm. All samples were prepped and exposed the same way so that comparisons between the samples would be meaningful. Results show that silicones perform better than acrylates, which perform better than epoxies, and not all silicones perform equally. Data will be provided of the best performing materials and a discussion of future work given the understanding of the chemistry.