Introduction to the method of surface pretreatment of plastic products

the surface treatment of plastic products mainly includes coating cladding and coating treatmentGeneral plastic crystallization is large, polarity is small or non-polarity, the surface can be low, which will affect the coating coating adhesionBecause plastic is a non-conductive insulator, so can not be directly coated on the plastic surface according to a plating process specification, so before surface treatment, should be necessary pretreatment to improve the binding force of the coating and for the coating to provide a good binding effect of the conductive bottom1Pretreatmentcoating is covered, including de-oil treatment on plastic surfaces, i.eoil and release agents for cleaning surfaces, and activation treatment of plastic surfaces, with the aim of increasing the adhesion of the coating(1) of the removal of oil from plastic productsSimilar to surface degrease of metal products, plastic products can be cleaned with organic solvents or with alkaline aqueous solutions containing surfactantsOrganic solvent de-oil is suitable for cleaning paraffin, beeswax, fat and other organic dirt from the plastic surface, the organic solvent used should deal with the plastic insoluble, insoluble, non-cracking, its own low boiling point, volatile, non-toxic and non-combustiblealkaline aqueous solution is suitable for de-oiling of alkali-resistant plasticsThe solution contains caustic sodium, alkaline salts and a variety of surfactantsThe most commonly used surfactant is the OP series, the alkyl phenol polyoxyethylene ether, which does not form foam and does not remain on plastic surfaces(2) the activation of the surface of plastic productsThis activation is to improve the surface energy of the plastic, that is, to create some polar base on the plastic surface or to thicken it, so that the coating is easier to wet and adsorbed to the surface of the productionThere are many methods of surface activation treatment, such as chemical oxidation, flame oxidation, solvent vapor erosion and corona discharge oxidationOne of the most widely used is the chemical crystal oxidation treatment method, which is commonly used in chromic acid treatment liquid, its typical formula is potassium potassium potassium potassium is 4.5%, water 8.0%, concentrated sulfuric acid (96% or more) 87.5% plastic products, such as polystyrene and ABS plastics, can be coated directly without chemical oxidation treatment In order to obtain a high-quality coating is covered, also with chemical oxidation treatment, such as ABS plastic after degreasing, can use a thinrnoch of chromic acid treatment liquid immersion, the typical treatment formula is chromic acid 420g/L, sulfuric acid (proportion 1.83) 200ml/L The typical treatment process is 65 degrees C 70 degrees C/5min10min, washed and dry the advantage of using chromiic acid to treat liquid erosion is that no matter how complex the plastic products are, they can be treated evenly, the disadvantage of which is that the operation is dangerous and there is a pollution problem 2 The pretreatment of the coating is coated the pre-treatment of the coating is intended to improve the adhesion of the coating and the plastic surface and to make the plastic surface form a conductive metal base The pre-processing processes include: mechanical roughing, chemical de-oilremoval, chemical roughing, sensitivity treatment, activation treatment, reduction treatment and chemical plating The first three are to improve the adhesion of the coating, and the last four are to form a conductive metal base (1) Mechanical roughing and chemical roughing Mechanical roughing and chemical roughing are used by mechanical and chemical methods to thicken the plastic surface, in order to increase the contact area of the coating and the substrate It is generally believed that the binding force of mechanical coarseness is only about 10% of the chemical coarseness (2) chemical de-oiling The plastic surface coating is treated with the same method of degrease before it is coated and degreased before coating is coated (3) sensitivity Sensitivity is to make plastic surface with a certain adsorption capacity to adsorption of some easily oxidized substances, such as tin dichloride, titanium trichloride and so on These adsorption-prone oxidizing substances are oxidized during activation treatment, while activators are reduced to catalytic nuclei and left on the surface of the product The role of sensitization is to lay the foundation for subsequent chemical coatings (4) activated Activation is the treatment of a sensitized surface by means of a solution of catalytically active metal compounds The essence is to adsorption of the product with reducing agent immersed in the water solution containing precious metal salt oxidant, so the precious metal ions as an oxidant was reduced by S2 -n, the restored precious metal is colloidal particles deposited on the surface of the product, it has a strong catalytic activity When such surfaces are immersed in a chemical plating solution, these particles become catalytic centers, speeding up the reaction of chemical plating (5) restore processing After activation treatment and washing with water after the product in chemical plating, with a certain concentration of chemical plating with the reducing agent solution to impregnate the product, in order to restore the unwashed activator to remove the clean, this is called reduction treatment When chemically plated copper, it is reduced with formaldehyde solution and when chemically nickel plated is reduced with sodium hypophosphate solution (6) chemical plating The purpose of chemical plating is to generate a conductive metal film on the surface of plastic products, creating conditions for the metal coating of electroplating of plastic products, so chemical plating is a key step for plastic plating