1 metal material
1.1, aluminum alloy: according to degreasing - alkali treatment - chromic acid etching method. The solvent degreasing method can only remove the dirt on the aluminum surface to make the natural oxidation of the surface clean; the alkaline solution removes the oil stain, and the surface natural oxide film is dissolved in the alkali solution, and a new oxide film is formed; the acid etching treatment energy Dissolve the natural oxide film of the surface layer, and then generate a dense and hard oxide film, the film thickness is 1-3um, the cohesive strength is high, the adsorption force is strong, and the bonding performance is good. The surface after the acid etching treatment is often in tap water. Rinsing is clean and a uniform film of water appears. Wipe and dry below 70°C.
2Al(OH)3+3H2SO4 → Al2(SO) 4+6H2O
Na2CrO7+ H2SO4 → Na2SO4+2CrO3+ H2O
2Al+2CrO3 → Al2O3+ Cr2O3
US Standard H2SO4 - Sodium Bichromate Solution Formula:
Na2CrO7 1 (2.4%) (66-71°C)/10-12 min H2SO4 10 (22.4%) (66-71°C)/10-12 min distilled water (73.2%) (66-71°C) /10-12 points British Standard Treatment Formula: Cr2O3 5% or 0 (60-65°C)/30 minutes Na2CrO7 0 or 7.5% (60-65°C)/30 minutes H2SO4 127.3% or 27.3% 60-65 °C) / 30 minutes of distilled water 67.7% or 65.5% (60-65 °C) / 30 minutes 1.2, carbon steel: in the humid air easily oxidized to generate Fe2O3.n H2O.
(1) Solvent degreasing - soak in concentrated HCL1 and H2O1 parts solution at room temperature for 5-10min - polymerize rinse, dry - dry (93°C, 10min)
(2) Degreasing the solution: soak in Na2CrO7 (4 parts), concentrated H2SO4 (10 parts) and 30 parts of distilled water at 71-77°C for 10 min. The rest is the same as (1).
(3) Degreasing the solution: Soaking in sodium sulfate (30 parts), washing powder (3 parts), and water (96.7 parts) at 60-65°C for 5-10 minutes - rinse clean and at 100-105 °C drying.
1.3, stainless steel
(1) After degreasing, immersed in 100 parts of concentrated H2SO4 and 3 parts of Na2CrO7 solution at 60-65°C for 15 minutes, washed and dried.
(2) After degreasing, immersed in 100 parts of concentrated HCL, 4 parts of H2O2 (30%), 20 parts of formaldehyde (40%) and 90 parts of H2O for 10 minutes at 65°C. After washing, they were soaked in concentrated H2SO4 (100 parts), Na2CrO7 (10 parts) and H2O (30 parts) at 65°C for 10 minutes, washed and dried.
(3) After degreasing, soak in concentrated HCL (2 parts), hexamethylenetetramine (5 parts), H2O2 (1 part) and H2O (20 parts) at 65-70°C for 10 minutes, wash and dry.
1.4, titanium alloy:
(1) After degreasing, treat 1-2H at room temperature in 2.7g H2O2 (50%), 9.6NaOH and 1000ml H2O, wash and dry.
(2) After degreasing, immersed in 841 ml of concentrated HCL, 63 ml of concentrated HF and 89 ml of H3PO4 for 2 min at room temperature, washed and dried (10-15 min at 82-93°C). Adhesives include epoxy, phenolic, polyimide, polybenzimidazole and other high temperature adhesives.
1.5, magnesium alloy: Magnesium alloy is a very light metal, its surface activity is easy to generate oxide film. Magnesium is more alkali-resistant, but reacts with methyl esters easily, so the degreasing solvent can only be acetone, trichloroethylene, and the like.
(1) After degreasing, immerse in NaOH (80%) at 60-80°C for 5-10 minutes, wash in 1.8 parts of Ca(NO3) 2, 24 parts of chromic acid, and 123 parts of H2O for 5 minutes at room temperature. -10min, wash and dry.
(2) After degreasing, immersed in Cr2O3 (17 parts), NaNO3 (20 parts), 105 parts of acetic acid and 100 parts of H2O for 3 minutes at room temperature, washed and dried. Choose EPOXY - polyamide or EPOXY - rubber adhesive.
1.6, Copper: Copper is susceptible to corrosion in wet environments, especially with ethylenediamine or DTA-cured epoxy adhesives that have a greater corrosive effect on copper.
(1) After degreasing, soak in the mixed solution at room temperature for 3 minutes, wash and dry, and use immediately (mixed solution is concentrated HCL: FeCl3: H2O = 50:20:30)
(2) After degreasing, soak in solution HNO3 for about 15 minutes, and scrub until all the corrosive sites disappear to the net. Dry immediately. Choose EPOXY, polyamide, silicone, phenolic, neoprene and nitrile rubber.
1.7, zinc
(1) After degreasing, soak in HCL (6%) for 4 min at room temperature, wash and dry immediately.
(2) After degreasing, soak in the mixed solution at 38°C for 5 minutes, wash and dry. (The mixed solution is Na2CrO7: concentrated H2SO4:H2O=1:2:8), and the epoxy, polyurethane, silicone, phenolic, etc. are bonded.
2. Polymer materials
2.1 Reasons for difficult adhesion of polymer materials:
A, the surface performance is very low, it is difficult to completely infiltrate such as silicone rubber. PTFE and so on.
B. The surface is non-polar and the force between the adhesive and the adhesive is low.
C. Easy surface liposuction and other low-molecular substances are difficult to remove.
D, higher thermal expansion coefficient, easy to produce thermal stress.
E. Low modulus of the material and stress concentration at the interface. (Use an adhesive with a solubility parameter close to that of the adhered material; surface treatment to increase the bond strength)
2.2 Fluoropolymers (Polytetrafluoroethylene PTFE)
A, sodium - naphthalene - THF solution etching method. Rc = 18.5 dyn/cm The surface of the fluorine-containing material was sanded with fine sandpaper, washed with acetone, and allowed to dry for 1-15 min in a treatment solution at room temperature. At this time, a uniform brown carbonized film (about 1 μm in thickness) was formed on the surface. Take out acetone or acetic acid and then wash with water, dry immediately glue or dry after storage within 2-3 months have good adhesive properties.
Preparation of treatment solution: In a three-necked bottle, 118-128 g of refined naphthalene was placed, and 100 ml of tetrahydrofuran to which peroxide was removed was added. After stirring and dissolving, slowly add 23-30g sodium tablets, react 1-2H, the solution appears green (in dry nitrogen, prevent O2 and moisture effects). The treatment solution must be kept in an inert gas and acetic acid sealed dry container for three months, with water vapour and air immersed.
The treated PTFE was glued with EPOXY-polyamide glue, and its room temperature was 11 mpa or more (PTFE/AL).
B molten potassium acetate method: in the molten k + CH3COO- at 320-330 °C for 6min, washed dry.
Bonded with silicone, epoxy, polyurethane, phenolic-nitrile rubber