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Significance and Use
Bonding of many polymeric substrates presents a problem due to the low wettability of their surfaces and their chemical inertness. Adhesive bond formation begins with the establishment of interfacial molecular contact by wetting. Wettability of a substrate surface depends on its surface energy. The surface activation with electrical discharges improves wettability of polymers and subsequent adhesive bonding. The surface activation with electrical discharges results in addition of polar functional groups on the polymer surface. The higher the concentration of polar functional groups on the surface the more actively the surface reacts with the different polar interfaces.
To achieve a proper adhesive bond the polyolefin substrate's polar component should be raised from near zero to 15 to 20 mJ/m2.
The pre-treated surfaces are ready for application of the adhesive immediately after the treatment.
1.1 This practice covers various electrical discharge treatments to be used to enhance the ability of polymeric substrates to be adhesively bonded. This practice does not include additional information on the preparation of test specimens or testing conditions as they are covered in the various ASTM test methods or specifications for specific materials.
1.2 The types of discharge phenomena that are used for surface modification of polymers fit into the general category of nonequilibrium or non-thermal discharges in which electron temperature (mean energy) greatly exceeds the gas temperature.
1.3 The technologies included in this practice are:
|Gas plasma at reduced pressure||8|
|Electrical discharges at atmospheric pressure||9|
|AC dielectric barrier discharge||9.1|
|High Frequency Apparatus||9.1.1|
|Suppressed Spark Apparatus||9.1.2|
|Arc Plasma Apparatus||9.2|
|Glow Discharge Apparatus||9.3|
Note 1—The term “corona treatment” has been applied sometimes in the literature to the different electrical discharge treatment technologies described in Section 9. This practice defines each electrical discharge treatment technology at atmospheric pressure presented in Section 9 and draws the necessary distinctions between them and corona discharge. See Test Method D1868 for “corona discharge.”
1.4 The values stated in SI units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements appear in Section 6.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D724 Test Method for Surface Wettability of Paper (Angle-of-Contact Method)
D907 Terminology of Adhesives
D1868 Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems
D2578 Test Method for Wetting Tension of Polyethylene and Polypropylene Films
D2651 Guide for Preparation of Metal Surfaces for Adhesive Bonding
D5946 Test Method for Corona-Treated Polymer Films Using Water Contact Angle Measurements
ICS Number Code 83.140.01 (Rubber and plastic products in general)