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U-Varnish Polyimide Varnish
U-Varnish is a solution of polyimide precursorpolyamic acid. It is coated on substrate and heated to high temperatures to vaporize the solvent, accelerate the imidization reaction and make a non-soluble, non-melting film coating with superior heat resistance, chemical resistance and electric insulation properties.
1. Grade of U-VARNISH
U-VARNISH has two grades according to applications
- U-VARNISH-A (Normal heat resistant type)
- U-VARNISH-S (High heat resistant type)
2. Characteristics of U-VARNISH
(1) General properties of U-VARNISN Properties of U-VARNISH | Item | Unit | U-VARNISH-A / U-VARNISH-S | Remarks | | Solvent | - | NMP | N-Methyl-2-Pyroridon | | Concentration | wt% | 20.0 | | | Solid Content | wt% | 18.0 ± 1.0 | 350°C, 30min. | | Density | g/cm3 | 1.10 - 1.11 | at 30°C | | Viscosity | Poise | 50 ± 10 | at 30°C |
(2) Temperature dependence of viscosity
(3) Concentration dependence of viscosity
U-VARNISH is used in the desired concentration by diluting with NMP or DMAc (N, N-dimethylactoamide)
(4) Storage stability
U-VARNISN has superior storage stability than the other type polyimide. U-VARNISH has very low viscosity increase at room temperature and can be used even after 3months storage, while the other type polyimide need to be stored below 5°C.
3. Film properties of U-VARNISH
U-VARNISH coated film has superiority not only in mechanical and electric properties but also in wide temperature range applicability, flammability and abrasion resistance.
(1) Mechanical properties
Mechanical properties U-VARNISH coated film (25µm) | Item | Unit | U-VARNISH-A | U-VARNISH-S | | Tensile Strength | Kg/mm2 | 20 | 40 | | Elongation | % | 100 | 30 | | Tensile Modulus | Kg/mm2 | 380 | 900 |
(2) Electric properties
U-VARNISH coated film has superiority in high dielectric constant, high insulation breakdown voltage and low dissipation factor.
Electric properties of U-VARNISH coated film (25µm) | Item | Unit | U-VARNISH-A | U-VARNISH-S | | Breakdown Voltage | KV/mm | 150 | 150 | | Volume Resistivity | Ω-cm | 1.5 x 1016 | 1.5 x 1016 | | Surface Resistance | Ω | >1016 | >1016 |
(3) Thermal properties
U-VARNISH coated film has no melting point and high thermal decomposition temperature, U-VARNISH-S particularly has over 550°C of thermal decomposition temperature, so it does not soften, fluidize and decompose.
| Item | Unit | U-VARNISH-A | U-VARNISH-S | | Heat Shrinkage | % | 0.2 | 0.1 | | CTE | ppm/k | 28 | 12 | | Water Absorption | % | 1.3 | 1.2 |
(4) Chemical resistance
U-VARNISH coated film has excellent resistance to metallic salt solution acid and alkali.
Chemical Resistance | Chemical | Typical Value (Thickness:25µm) | | Strength RetentionRate (%) | Elongation RetentionRate (%) | | Methylenechloride | 95 | 96 | | Chloroform | 88 | 90 | | Trichloroethylene | 93 | 102 | | Methylethylketone | 92 | 89 | | Ethanol | 89 | 100 | | Xylene | 99 | 84 | | m-Cresol | 90 | 90 |
Condition: immersed at 30°C for 24hr | Chemical | Typical Value (Thickness:25µm) | | Strength RetentionRate (%) | Elongation RetentionRate (%) | | N-Methyl-2-Pyroridon | 98 | 107 | | Acetic Acid | 91 | 1108 | | 10% Hydrochloric Acid | 91 | 82 | | 10% Sulfuric Acid | 93 | 94 | | 2% Sodium Hydroxide | 99 | 91 | | 10% Sodium Hydroxide | 82 | 81 |
4. Warning of handling
Please keep U-VARNISH in a dark and cool place in case of long term storage.
Please keep a lid on in storage because it might be dehydrated due to moisture in air when it opens.
Please wipe out with cloth or paper when it contacts to skin.
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