Compared with metal parts, plastic electroplating products can not only achieve a good metal texture, but also reduce the weight of products, effectively improve the appearance and decoration of plastics, but also improve their electrical, thermal, and corrosion resistance, but the selection of plastic materials for electroplating should comprehensively consider the processing performance, mechanical properties, material cost, electroplating cost, electroplating difficulty and dimensional accuracy and other factors.
Because of its structural advantages, it not only has excellent comprehensive properties, easy to be processed and mold but also has high coating adhesion due to easy erosion on the material surface, so it is widely used in electroplating.
Purpose.
The purpose of plastic plating is to cover the plastic surface with metal, which not only increases beauty, but also compensates for the shortcomings of plastics, endows them with the properties of metals, and gives full play to the characteristics of plastics and metals. a large number of plastic electroplating products have been used in electronics, automobiles, household products, and other industries.
Process
(1) cleaning: remove the dirt and fingerprints left in the plastic molding process, which can be washed with alkali and then neutralized with acid and washed with water.
(2) solvent treatment (solvent treatment): wetting the plastic surface (wetting) to interact with the regulator (conditioner) in the next step.
(3) adjusting treatment (conditioning): coarsening the plastic surface into an inner locking hole to make the coating tight and difficult to peel off, also known as chemical coarsening.
(4) sensitization: the reducing agent is adsorbed on the surface, and stannous chloride (stannous chloride) or other tin compounds are commonly used, that is, sn ions are adsorbed on the plastic surface with a reducing surface.
Compared with metal parts, plastic electroplating products can not only achieve a good metal texture, but also reduce the weight of products, effectively improve the appearance and decoration of plastics, but also improve their electrical, thermal, and corrosion resistance, and improve their surface mechanical strength.
However, the selection of plastic materials for electroplating should comprehensively consider the processability of the materials, the difficulty of electroplating, and the dimensional accuracy.
Because of its structural advantages, ABS plastic has not only excellent comprehensive properties, easy processing and molding, but also high coating adhesion due to easy erosion on the material surface, so it is widely used in electroplating.
With the rapid development of industry and the increasingly wide application of plastic plating, it has become one of the important means of surface decoration in plastic products.
Electroplating has been widely used on ABS, polypropylene, polysulfone, polycarbonate, nylon, phenolic glass fiber reinforced plastics, polystyrene, and other plastics at home and abroad, among which ABS plastic electroplating is the most widely used and the electroplating effect is the best.
Advantages of plastic plating (plastic plating):
Good corrosion resistance.
Drug resistance is good.
Excellent electrical insulation.
The price is low.
Can be mass-produced.
Disadvantages
Poor weather resistance and brittleness caused by light exposure.
The heat resistance is not good.
Low mechanical strength.
The wear resistance is very poor.
High water absorption.
Selection of injection machine.
Improper selection of injection machine, sometimes because the pressure is too high, the nozzle structure is not suitable or mixing makes the parts produce greater internal stress, thus affecting the adhesion of the coating.
Material selection of plastic parts.
There are many kinds of plastics, but not all of them can be electroplated.
Some plastics have poor adhesion to the metal layer and have no practical value; some of the physical properties of some plastics and metal coatings, such as the coefficient of expansion, are too different, so it is difficult to guarantee their performance in a high-temperature difference environment.
ABS is the most commonly used in electroplating, followed by PP.
In addition, PSF, PC, PTFE and so on also have successful electroplating methods, but they are difficult
Molding of Plastic Parts
Under the premise of not affecting the appearance and use, the modeling design of plastic parts should meet the following requirements as far as possible.
(1) Metal luster will make the original shrinkage become more obvious, so it is necessary to avoid uneven wall thickness of the products, so as to avoid shrinkage, and the wall thickness should be moderate, lest the wall is too thin (less than 1.5 mm), otherwise, it will cause poor rigidity, easy to deform during electroplating, poor adhesion of the coating, and easy to deform and make the coating fall off in the process of use.
(2) avoid the blind hole, otherwise, the treatment solution left in the blind hole is not easy to clean, which will cause pollution in the next process, thus affecting the quality of electroplating.
(3) the sharp edge becomes thicker in the electroplating process.
The sharp edge in electroplating will cause tip discharge, resulting in the uplift of the corner coating.
Therefore, the fillet transition should be adopted as far as possible, and the fillet radius is at least 0.3 mm.
The plated parts are difficult to be electroplated, the central part of the plated part is thinner, and the close to the edge, the thicker the coating is, and the whole coating is uneven, so the plane shape should be changed to a slightly curved surface or a matte surface made of orange peel pattern.
The larger the surface area of electroplating, the greater the gloss difference between the center and the edge, and the slightly parabolic surface can improve the gloss uniformity of the plating surface.
(4) minimize grooves and protruding parts on plastic parts.
Because the deep concave part is easy to be exposed during electroplating, and the protruding part is easy to be scorched.
The depth of the groove should not exceed 1 of the width of the groove, and the bottom should be an arc.
When there is a grille, the hole width should be equal to the beam width and less than 1 prime 2 of the thickness.
(5) the plated parts should be designed with sufficient mounting position, and the contact surface with the hanger should be 2 or 3 times larger than that of the metal parts.
(6) the plastic parts should be designed to make it easy to release the mold when sinking, otherwise, the surface of the plated parts will be strained or sprained, or the internal stress of the plastic parts will be caused and the adhesion of the coating will be affected.
(7) when knurling is needed, the knurling direction should be consistent with the demolding direction and be linear. The distance between the knurled stripes and the stripes should be as large as possible.
(8) plastic parts should not use metal inserts as far as possible, otherwise, the inserts are easy to corrode during pre-plating treatment.
(9) the surface of plastic parts should have a certain surface roughness.
Mold design.
In order to ensure that there are no defects on the surface of plastic plated parts, no obvious directional structure, and internal stress, the following requirements should be met in the design and manufacture of molds.
(1) the mold material should not be made of beryllium bronze alloy but should be made of high-quality vacuum-cast steel. The cavity surface should be polished to mirror bright along the exit direction, the roughness is less than 0.2mm, and the surface should be plated with hard chromium.
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