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LaRC-SI - General Information
LaRC-SI (Soluble Imide) is a unique amorphous thermoplastic developed at NASA/Langley Research Center. LaRC-SI exhibits a unique combination of properties which allows it to be the choice for mechanical, optical, electronic, adhesive, composite and coating applications. LaRC-SI has the versatility for mechanical applications because it is extremely tough, lightweight, solvent resistant, and has a high glass transition temperature (Tg). Its self-bonding properties allows materials to be incorporated into the resin which affords parts with unique characteristics such as increased hardness, lower Coefficient of Thermal Expansion, decreased friction, higher compressive strength and wear resistance.
The melt-flow properties of LaRC-SI permit extrusion, injection, and compression molding, and fiber melt spinning. LaRC-SI has been used as a hot-melt adhesive to bond a variety of metals, ceramics, and polyimide films. LaRC-SI has also been blended with commercial printed circuit boards (PCBs resins to provide multilayer PCBs with increased shear strength and durability at elevated temperatures.
In addition, LaRC-SI has been used to create novel strong ultrathin composite coatings by combining different materials with the sprayable solution. Materials such as metals, synthetic diamond, graphite, plastic, and ceramic powders are just a few examples of compounds which have been combined and sprayed using conventional techniques. Initial applications for these new forms of composite coatings include:
These methods are also easily adapted for continuous manufacturing processes which can be dictated by the users and their specific needs.
Perhaps the single most beneficial advantage to the multi-applicability of LaRC-SI resides in the fact that LaRC-SI can be processed as the fully imidized polymer. Typically, polyimides must be processed as the polyamide acid intermediate and undergo imidization after fabrication. This requires extra prep time and can lead to imperfect parts. One of the unique attributes of LaRC-SI is that when it is exposed to temperatures above its softening point of 250 oC, it cannot be redissolved, yet it maintains its amorphous character and melt processability.
This property is unique for both thermoplastics and thermosets and, in conjunction with its self-bonding property, allows LaRC-SI to form bonded distortion-free solvent resistant multilayer coatings. Moreover, these multilayer coatings are stable at temperatures ranging from cryogenic to at least 200 oC. Since LaRC-SI has a low dissipation factor and high dielectric strength, these coatings have been used to form extremely thin flexible multilayer circuits, dielectric interlayers, protective coatings, etc. without the use of additional adhesives.
This truly unique combination of properties makes LaRC-SI significant among both polyimide thermoplastics and thermosets. It is the "choice" resin for a variety of applications and has demonstrated the potential to improve and enable new technologies. In summation, LaRC-SI is best described as "one-stop-shopping" stand alone material.
LaRC-SI Physical Properties
LaRC-SI Solvent Resistance
| Test Temperature | Tensile Modulus | Tensile Strength | % Elongation |
| 23 oC | 4.05 | 141 | 7.2 |
| 177 oC | 2.63 | 76 | 33 |
Machined Resin Moldings (ASTM D-638, E-399)
| Test Temperature | Tensile Modulus | Tensile Strength | K1c | G1c |
| (oC) | (GPa) | MPa | (g/N/m-3)/2 | kJ/m2 |
| 4.23 | 111.2 | 4.4 | 4.6 | 23 |
| 4.45 | 111.2 | 4.3 | 4.2 | 177 |
| 3.16 | 4.28 | ND | ND | 177 |
| 3.26 | 53.1 | ND | ND | ND |
- LaRC-SI powder molded at 300 oC/30 min./200 psi
- LaRC-SI powder molded at 350 oC/30 min/150 psi
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