Plastic surface treatment method before bonding

Plastics can be divided into two categories: thermoplastics and thermosetting plastics. In general, thermosets are easier to glue than thermoplastics. However, their surface energy is lower than that of hydrophilic materials such as glass, ceramics, and metals, and their surface often adheres to release agents or plasticizers, and thus are not easily wetted by the adhesive, thereby affecting the bonding strength. Therefore, it is generally necessary to surface-treat plastics. Due to the large variety of plastics and the wide range of properties, the surface treatment methods are very different. The following describes several common plastic surface treatment methods.

[method 1]
This method is mainly applicable to polyethylene, polypropylene, polyisobutylene, polyvinyl chloride, and perchloroethylene.
Degreasing solvents for the above plastics are acetone and butanone.
After degreasing, the oxidation flame treatment was performed: first, it was roughened with an abrasive cloth, and it was placed on an oxidizing flame for 3-5 s for three consecutive times. Then use 30% sodium hydroxide solution, immersed for 3-5min at 65-70°C, rinsed with cold water, then activated with the following solution, and impregnated at 65-70°C for 5-10min:
Chromic acid 10 Concentrated sulfuric acid 20 Water 40
After washing with water, oxidize at 70-75°C for 5-7min in the following solution:
Potassium dichromate 10 Concentrated sulfuric acid 50 Water 340
Then wash in hot water at 70-75°C for 5-7min, wash with distilled water and dry at 65-70°C.

[Method 2]
This method applies to the same object as above.
Treatment in the following solution at 20 °C for 90 min:
Sodium dichromate 5 Sulfuric acid (d=1.84) 100 Water 8
After washing with cold water, dry it at room temperature.

[Method 3]
This method is applicable to the same object as above.
Exposure treatment in any of the following gases activated by corona discharge:
(1) dry air, 15min;
(2) Nitric oxide, 10min;
(3) Wet air, 5min;
(4) In nitrogen, 5 min.
After processing, it should be glued within 15min.

[Method 4]
This method is applicable to polystyrene and its modified varieties such as ABS and AS.
Sandblasting or emery cloth after grinding and degreasing.
Degreasing solvent: acetone, anhydrous ethanol.
After degreasing, immersed in chromic acid solution at 60°C for 20 minutes.

[Method 5]
This method is suitable for nylon.
Degreasing solvent: acetone, anhydrous ethanol, ethyl acetate, butanone, coat the surface with a layer of 10% nylon-phenol solution, hold at 60-70°C for 10-15min, then wipe with solvent (or at the surface A layer of resorcinol-formaldehyde primer is applied and glued immediately.

[Method 6]
This method is suitable for polyester film.
Degreasing solvent: acetone, anhydrous ethanol.
After degreasing, it was immersed in a sodium hydroxide solution at 80[deg.] C. for 5 min and then immersed in a stannous chloride solution for 5 s.

[Method 7]
This method is suitable for polyoxymethylene and other acetal polymers.
Degreasing solvents: acetone, butanone.
Drying at 120°C for 1 hour and immersing in the following solution at 120°C for 5 minutes:
P-toluenesulfonic acid 1 dioxane 10 perchloroethylene 200
After washing with cold and hot water, dry with hot air.

[Method 8]
This method is suitable for polytetrafluoroethylene and other fluorocarbon polymers.
Degreasing solvents: trichloroethylene, benzene, toluene, acetone, butanone, cyclohexanone.
After degreased, immersed in the following solution at room temperature for 30 minutes:
Sodium hydroxide 10 Has diene melamine 8
Then dry at room temperature.

[Method 9]
This method is radiation-induced grafting. The applicable object is the same as above.
The use of high-energy radiation such as cobalt-60 radiation or ultraviolet light below 2000Ã… causes slight degradation of the fluoroplastic surface in the presence of styrene monomer, and generates an active center at the chain end to form a transparent graft copolymer.
With this method, the color remains unchanged, and the electrical properties do not decrease.

[Method 10]
This method is a fluorinated hydrocarbon-titanium polymer method. The applicable object is the same as above.
A solution containing tetrabutyl titanate, perfluorooctyl ester, and water was immersed to form a thin film layer of an alkyl-titanium-oxygen and perfluoro branched polymer on the surface.

[Method 11]
This method is applicable to the same object as above.
128g of refined naphthalene is dissolved in 1000ml of tetrahydrofuran (or ethylene glycol methyl ether, ethylene glycol dimethyl ether, dioxane), and 2g of sodium metal is slowly added under stirring for 2 hours, and the temperature is strictly controlled at 3-5. °C. After the addition was complete, stirring was continued until the solution turned blue-black. Under nitrogen protection, Teflon is placed for 5 min, then removed, rinsed with cold water, rinsed with distilled water, and warm air dried.
This method is stable and reliable, and has high bonding strength. It is the most commonly used method for surface treatment of fluorine plastics.

[Method 12]
This method applies to the same object as above.
After degreasing the fluorine plastic, the surface is coated with a layer of epoxy resin glue, heated at 370° C. for 10 minutes, and then heated at 400° C. for 5 minutes so that the adhesive layer is melted into the fluorine plastic surface, and then glued.

Source: 21st Century Fine Chemicals Network