Momentive Performance Materials



  LIM® 8040
  Self Bonding Liquid Silicone Rubber
Product Description 
 LIM8040 liquid silicone rubber is a 2-component liquid injection molding material which offers primerless adhesion to a wide range of substrates including metals and many engineering plastics, making it an ideal material for insert molding applications. LIM8040 liquid silicone rubber is designed to be used in a 1:1 mix ratio and cures rapidly at molding temperatures of 150°C - 190°C to a high tear strength, translucent silicone elastomer.
Key Performance Properties 
  • Primerless adhesion to many substrates
  • High strength, low modulus properties
  • Rapid molding cycle times- 20-60 seconds
  • Convenient 1:1 Mix Ratio
  • Outstanding Thermal Cycling Performance
    • Typical Product Data 

    Uncured Properties

    LIM8040A

    LIM8040B

    Appearance

    Translucent

    Translucent

    Specific Gravity, gm/cc

    1.08

    1.08

    Application Rate, gm/min

    90

    95

    Mixed A & B

    LIM8040 A + B

    Work Life (25C), Hours

    48+

    Cure Rate (@ 177C/350F) (Monsanto Rheometer - MDR2000E)

    		 

    T-02, seconds

    11

    T-90, seconds

    17

    Peak Rate, in/lb/min

    98

    Torque, max reading, in-lbs

    13

    Cured Properties (75 mils thick)

    		 

    Physical

    As Molded
    30 secs 177C/(350F)

    Postbaked
    1 hr 177C/(350F)

    Hardness, Shore A Durometer

    43

    46

    Tensile Strength, MPa (psi)

    5.17 (750)

    5.55 (805)

    Elongation, %

    385

    375

    Tensile Modulus, 100% MPa (psi)

    1.19 (172)

    1.55 (225)

    Tear Strength, Die B KN/M (lb/in)

    37.8 (215)

    30.2 (172)

    Compression Set, % @150C (302F)

    		    

    168 hours

    67

    27

    1000 hours

    76

    35

    Thermal Conductivity, W/m°K

    0.19

    0.19

    Electrical

    		    

    Dielectric Strength, V/mil

    500

    500

    Dielectric Constant

    2.85

    2.85

    Dissipation Factor

    0.003

    0.003

    Volume Resistivity Ohm-cm

    2.9 x 1014

    2.9 x 1014
    Specifications 

    Typical product data values should not be used as specifications. Assistance and specifications are available by contacting Momentive Performance Materials.
    Instructions for Use 

    Compatibility

    LIM8040 liquid silicone rubber will cure in contact with most clean and dry surfaces. However, certain materials, such as butyl and chlorinated rubber, sulfur-containing materials, amines, and certain metal soap cured RTV silicone rubber compounds can cause cure inhibition. Cure inhibition is characterized by a lack of cure of the liquid silicone rubber at the interface between it and the insert. Compatibility tests should be performed on all materials in contact with LIM8040 liquid silicone rubber, including painted surfaces, to ensure adequate cure.

    Surface Preparation

    The adhesive performance of any polymer system is highly dependent upon proper surface preparation. In order to maximize the adhesion of LIM8040 liquid silicone rubber, and minimize the potential for cure inhibition. All parts should be as clean and dry as possible prior to the molding of the LIM8040 liquid silicone rubber. Particular attention should be given to these areas which will come in direct contact with the silicone during the molding process.

    Bonding

    LIM8040 liquid silicone rubber is formulated to develop adhesion to a range of substrates without the use of a primer.

    Typical Adhesion Properties to Common Substrates

    Substrate

    Adhesion*

    ABS (CYCOLAC®)

    G

    Aluminum

    E

    PBT (VALOX®)

    E

    Polyamide (unfilled)

    G/E

    Polycarbonate (LEXAN®) - untreated

    U

    Polycarbonate (LEXAN®) - UV treated

    E

    Polyphthalamide (AMODEL®)

    E

    Polypropylene

    U

    PPO/Nylon (NORYL GTX®)

    G

    PVC

    E

    Steel

    E

    * G = Good, E = Excellent, U - Unsatisfactorily

    Bonding (continued)

    For difficult-to-bond-to-substrates, or where more aggressive chemical adhesion is desired, the adhesion may be enhanced by using SS4155 silicone primer, available from Momentive Performance Materials. To apply the primer, thoroughly clean the surface and let dry. Then apply a uniform film (0.01-0.02 mm/0.5-1.0 mil) of SS4155 silicone primer and allow the primer to air-dry for one hour or more before insert molding with LIM8040 liquid silicone rubber. For more details on priming and adhesion, please refer to Momentive Performance Materials product data sheet on silicone primers (CDS1873).

    Mold Release

    Because LIM8040 liquid silicone rubber is formulated to offer primerless adhesion, it is necessary to use a release coating on the mold. For most applications, the use of a permanent mold coating, such as nickel-teflon, is recommended. Spray applied release agents may also be used, but should be very carefully evaluated to eliminate the potential for cure inhibition. For more information, contact Momentive Performance Materials.

    Mixing

    LIM8040 liquid silicone rubber is a kit-matched product. As such, work time (pot-life), cure time, and final cured properties can only be assured if the batch numbers on the A component and B component are identical and the material is mixed at a ratio of 1:1 (by weight).

    LIM System Equipment

    Pumping and meter-mixing systems for LIM8040 liquid silicone rubber and appropriate injection molding machines are available from a number of manufacturers, most of whom will provide a complete integrated system (exclusive of the mold itself). Contact Momentive Performance Materials for further information.
    Handling and Safety 

    Material Safety Data Sheets are available upon request from Momentive Performance Materials. Similar information for solvents and other chemicals used with Momentive Performance Materials Products should be obtained from your suppliers. When solvents are used, proper safety precautions must be observed.
    Storage and Warranty Period 

    The warranty period for LIM8040 liquid silicone rubber is 6 months from date of shipment if stored in the original unopened containers at temperatures of 25C (77F) or below.

    Availability 

    LIM8040 liquid silicone rubber may be ordered from Momentive Performance Materials, Waterford, NY 12188, or the Momentive Performance Materials' sales office nearest you.
    Government Requirement 

    Prior to considering the use of a Momentive Performance Materials' product in fulfilling any Government requirement, please contact the Government and Trade Compliance office at 413-448-4624.

    ® LIM is a registered trademark of Momentive Performance Materials.
    ® Cycolac, ®Valox, ®Lexan, and ®Noryl are registered trademarks of Momentive Performance Materials.
    ® Amodel is a registered trademark of Amoco Oil Company.

    CDS5388
     
     

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