Whitepapers - General
NuSil Technology's commitment to silicone education is manifested in part by our investment in
Whitepapers. Although many of the documents are in true Whitepaper format, we provide additional
resources like a Terms & Definitions document and an Adhesive / Primer study. While some papers are
broad in scope, others are industry specific. Papers are typically added monthly. Registering with
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For further reading, please see our Technical Resources section.
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May 22, 2012
Characterization of Fuel Resistant Fluorosilicones
Silicones are commonly used in automotive applications as potting compounds, adhesives, gaskets, seals and encapsulants due to their ability to remain elastic at low temperatures and resist breakdown at high temperatures or in UV light. In addition to a broad operating temperature range, silicones inherently possess high dielectric strength (=...
Silicones are commonly used in automotive applications as potting compounds, adhesives, gaskets, seals and encapsulants due to their ability to remain elastic at low temperatures and resist breakdown at high temperatures or in UV light. In addition to a broad operating temperature range, silicones inherently possess high dielectric strength (= 500 V/mil), low modulus and a low glass transition point (Tg), as compared to organic-based rubbers. These characteristics make silicones ideal for use in high-power electronic applications, yet gentle enough for delicate wire bond encapsulation and other applications in which thermal cycling is a concern. Ultimately, the quality that contributes most to silicone’s wide use in the automotive and other industries is the opportunity for formulation flexibility.
May 21, 2012
Non-toxic novel silicone foul-release marine coatings
This study evaluates modified silicone elastomers as foul-release coatings. The coatings are easy to apply, cure rapidly and relatively tough materials. They are non-toxic and biologically inert but still prevent the adhesion of marine life. The coatings were tested by a novel barnacle adhesion test with adhesion results in two...
This study evaluates modified silicone elastomers as foul-release coatings. The coatings are easy to apply, cure rapidly and relatively tough materials. They are non-toxic and biologically inert but still prevent the adhesion of marine life. The coatings were tested by a novel barnacle adhesion test with adhesion results in two weeks. The test consisted of coated glass slides upon which a barnacle was transferred from one substrate and re-attached to the test slide. After the barnacle re-attached, the adhesion was directly measured by a force displacement tester. Results are measured in psi.
May 21, 2012
Novel Adhesions Methods for Solar Cell Assemblies
Traditionally, engineers and solar cell assemblers have used liquid silicone adhesives to bond solar cells to panel substrates such as satellites, and silicones with high light transmittance to bond cover glasses to cells. Using next generation silicone technology, low outgassing silicone pressure sensitive adhesives (PSA) and thin film sheeting can...
Traditionally, engineers and solar cell assemblers have used liquid silicone adhesives to bond solar cells to panel substrates such as satellites, and silicones with high light transmittance to bond cover glasses to cells. Using next generation silicone technology, low outgassing silicone pressure sensitive adhesives (PSA) and thin film sheeting can serve the same purpose as liquid adhesives but eliminate long wait times for room temperature cures or additional equipment, such as ovens, required to heat accelerate the cure process. Moreover, the processing these low outgassing materials undergo allows them to be used on extraterrestrial applications like satellites as mentioned above.
Apr 2, 2012
LED Packaging with Silicone Encapsulants
A Light Emitting Diode (LED) is not “one size fits all.” While many LEDs may appear similar, various applications call for different needs. Whether one is deciding how to construct the LED or what the final application is going to be, decisions on what material to use can vary drastically.
A Light Emitting Diode (LED) is not “one size fits all.” While many LEDs may appear similar, various applications call for different needs. Whether one is deciding how to construct the LED or what the final application is going to be, decisions on what material to use can vary drastically. It is for this reason that a relationship needs to be maintained between the LED packager and material supplier. In most cases, the material of choice for LED packagers is silicone. To accommodate the various needs of the LED packager, silicone has become widely used due to its flexibility. Some attributes of silicone that lend themselves well to the LED industry are a high transparency in the UV-visible spectrum, thermal stability, mechanical and optical properties and an ability to control the Refractive Index (RI).
Jan 26, 2012
Designing low permeability, optical-grade silicone systems – Guidelines for choosing a silicone based on transmission rates for barrier applications
Unprotected electronic components exposed to moisture from high humidity may fail due to corrosion of metal leads or other unfavorable reactions on chemically sensitive components. This is of high interest for silicones that encapsulate Light Emitting Diodes (LEDs) dies. For these applications, moisture and oxygen may react with materials, such...
Unprotected electronic components exposed to moisture from high humidity may fail due to corrosion of metal leads or other unfavorable reactions on chemically sensitive components. This is of high interest for silicones that encapsulate Light Emitting Diodes (LEDs) dies. For these applications, moisture and oxygen may react with materials, such as phosphor, used to make white LEDs for back-lighting applications and decrease or change the light output and color over time. Of the polymeric adhesives and sealants commercially available, silicones are used for their thermal stability, clarity, and comparably low modulus that provides stress relief during thermal cycling. In addition, silicones are also known to be very permeable to low molecular weight gases such as water vapor and oxygen. Recently, several types of silicones were tested for the oxygen and water vapor transmission rates, and it was found that they can have drastically different results. Silicone properties strongly affecting permeability are polymer backbone chemistry, crosslink density and fillers. Phenyl (C6H5) and trifluoropropyl (CF3CH2) groups are used to optimize the refractive index of optically clear silicones. The effect of chemical composition on the water vapor transfer rate (WVTR) and the oxygen transfer rate (OTR) at 400 C and 90% Relative Humidity was investigated on several silicones with various refractive indices and compared to polydimethylsiloxane (PDMS) with similar durometers. It was found that polymer backbone chemistry had a significant influence on the permeation rates and will assist in material selection when designing for low-permeable barriers to improve package reliability.
Jan 9, 2012
Choosing a Silicone for Joining Technologies
Engineers and material scientists are constantly looking for a polymeric adhesive that can perform in a broad operating temperature range, maintain chemical stability and offer unique mechanical properties. The dynamic attributes of silicone adhesives, sealants, coatings and encapsulants provide design engineers with a variety of solutions to the complex challenges...
Engineers and material scientists are constantly looking for a polymeric adhesive that can perform in a broad operating temperature range, maintain chemical stability and offer unique mechanical properties. The dynamic attributes of silicone adhesives, sealants, coatings and encapsulants provide design engineers with a variety of solutions to the complex challenges they face. The advantages of silicone lie in the chemistry of the polymer chain, which can be modified to achieve desired mechanical properties.
Oct 21, 2011
Fluorosilicones in the Aerospace Industry
Fluorosilicone’s advent into the commercial marketplace offers opportunities for manufacturers to pursue new applications for silicones in the automotive, aircraft and general markets. The unique properties of fluorosilicones provide a solution for products that need broad operating temperatures, fuel resistance and long-term reliability. Conventional dimethyl silicones cannot survive the harsh...
Fluorosilicone’s advent into the commercial marketplace offers opportunities for manufacturers to pursue new applications for silicones in the automotive, aircraft and general markets. The unique properties of fluorosilicones provide a solution for products that need broad operating temperatures, fuel resistance and long-term reliability. Conventional dimethyl silicones cannot survive the harsh environments that fluorosilicones can endure. Similar to other silicones, fluorosilicones can be provided as high consistency rubbers (HCRs), liquid silicone rubbers (LSRs), dispersions, gels and even foams. Silicone manufacturers offer a variety of fluorosilicone solutions that fit the unique processes of any end-user. Whether fluorosilicones are used as adhesives, molded parts or protective coatings, flexibility of application is possible.
Apr 4, 2011
Choosing a Silicone Encapsulant for Photovoltaic Applications
Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when...
Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when using a RI matching silicone to minimize light loss versus a non-phenyl containing silicone.
Dec 15, 2009
Versatility and Flexibility from Low Outgassing Silicones
Miniaturization of electronic packages has led to using thinner and more fragile materials. This, in combination with the use of lead-free solder with solder reflow temperatures up to 260°C, can cause high shear stress during heating and cooling that can damage a device. Subsequently, there is growing interest in...
Miniaturization of electronic packages has led to using thinner and more fragile materials. This, in combination with the use of lead-free solder with solder reflow temperatures up to 260°C, can cause high shear stress during heating and cooling that can damage a device. Subsequently, there is growing interest in silicone adhesives and encapsulants for terrestrial electronic packaging applications.
May 18, 2008
Material and Process Innovations with Filled Silicone Elastomers
Today the technological progress of modern military aircraft design has been greatly influenced by the use of advanced composite materials. These materials permit design of lighter stronger more flexible aircraft yet offers a new set of challenges in design, production and quality.
Today the technological progress of modern military aircraft design has been greatly influenced by the use of advanced composite materials. These materials permit design of lighter stronger more flexible aircraft yet offers a new set of challenges in design, production and quality.
Feb 13, 2008
A Characterization of Yellowing Caused by UV Radiation on Silicone Encapsulants, and Improvements in Future Materials
This study evaluates twenty-one samples for their change in optical transmission due to a 680-6800J/cm2 dose of UV radiation.
Samples were made from UV curing acrylate, epoxy and silicone chemistries. All samples were prepared and exposed the same way
so that comparisons between the samples would be meaningful. Given the same dosage...
This study evaluates twenty-one samples for their change in optical transmission due to a 680-6800J/cm2 dose of UV radiation.
Samples were made from UV curing acrylate, epoxy and silicone chemistries. All samples were prepared and exposed the same way
so that comparisons between the samples would be meaningful. Given the same dosage of UV, silicones perform better than UV
curing acrylates, which perform better than epoxies.
Jun 8, 2004
Adhering to Difficult Substrates
Adhesive echnology is equal parts chemistry and ‘black magic’. Because there are so many different substrates, each adhesive can not be actually tested before hand on each and everyone. However, by testing on some novel substrates, or difficult to adhere to, inferences can be made which can narrow the choices...
Adhesive echnology is equal parts chemistry and ‘black magic’. Because there are so many different substrates, each adhesive can not be actually tested before hand on each and everyone. However, by testing on some novel substrates, or difficult to adhere to, inferences can be made which can narrow the choices of adhesives. We can define adhesion as the chemical bonding of two substrates. Substrates that have reactive groups available for bonding like OH groups on glass and aluminum make this chemical bond easier. Substrates with nothing to react to make adhesion difficult; graphite and PTFE. Multiple other substrates fit somewhere in-between.
Sep 25, 2003
Silicone Adhesives and Primers on Low Surface Energy Plastics and High Strength Metals
This paper will demonstrate the ability of silicone adhesives, with the aid of primers, to adhere to low surface energy plastics and to high strength metals. In general, some plastics are difficult to adhere to because of their low surface energy, available bond sites, and chemical interaction. Most plastic have...
This paper will demonstrate the ability of silicone adhesives, with the aid of primers, to adhere to low surface energy plastics and to high strength metals. In general, some plastics are difficult to adhere to because of their low surface energy, available bond sites, and chemical interaction. Most plastic have a surface energy under 50 dynes/cm while aluminum, an easier substrate to adhere to, is closer to 825 dynes/cm. Surface energy is a thermodynamic effect of how a liquid will ‘wet out’ on a surface. Low surface energy materials, like plastics, do not allow a liquid, like an adhesive, to ‘wet out’ on its surface. Adhesion chemistry tells us that the better an adhesive can ‘wet out’ on a substrate, the more surface area it can cover and allow more reactive groups to bond, making a stronger bond. Several low surface energy plastics and high strength metals were tested with silicone adhesives and primers to achieve cohesive bond failure when performing lap-shear testing. This list of substrates evaluated include polycarbonate, polyetherimide, polyamide, polyurethane, polymethylmethacrylate, polysulphone, titanium, stainless steel, and aluminum.
Feb 17, 2003
Accelerating Cure of Silicone Adhesives
This paper will demonstrate the availability of dramatically accelerating the cure of certain silicone adhesives and their advantage to the manufacturing process. A ‘fast cure’ adhesive is defined as full cure in less than ten minutes—or partial cure for handling under five minutes and full cure at room temperature in...
This paper will demonstrate the availability of dramatically accelerating the cure of certain silicone adhesives and their advantage to the manufacturing process. A ‘fast cure’ adhesive is defined as full cure in less than ten minutes—or partial cure for handling under five minutes and full cure at room temperature in 8 hours or one shift. Using a specific cure system and materials that have been developed to obtain fast-cure with heat acceleration, an experiment was performed to determine how fast, and at what temperatures these adhesives will cure. In conclusion, to obtain fast-cure at low temperature, 65ºC, R31-2186 can be fully cured in one minute. When adhering to temperature sensitive substrates, this provides a fast-cure choice. Although needing a higher temperature to obtain ‘fast-cure’, R32-2186 fully cures in 2 minutes at 100ºC. This can be useful because of R32-2186’s extended worktime. LSR-9820-20 proves the best choice for high temperature cure, 185ºC. In just 30 seconds it has a 300psi lap shear. Although this figure reaches optimum over time, for many applications this is a great partial cure.