1. The screen printed PVC of PVC plastics was put into industrial production in 1931. PVC plastics have the advantages of bright color, not easy to crack, acid resistance, alkali resistance and low price. However, because of the toxicity of some auxiliary materials, PVC products are not suitable for food. PVC film has a wide variety of designs and colors. Most of the colorful plastic cloth and artificial leather sold in the market are PVC products.
2. ABS plastic screen printing ABS resin plastic is an engineering plastic. In recent years, it is widely used in television, calculator and many fields of national economy. ABS plastic is a terpolymer of acrylonitrile, butadiene and styrene. Because ABS plastic is a terpolymer, it has the common characteristics of three components. Acrylonitrile can make the copolymer resistant to chemical corrosion and have certain surface hardness; butadiene can make the polymer rubber like toughness; styrene can make the polymer easy to process and form. ABS plastics have all kinds of colors. The products have glossy appearance, low water absorption, good impact strength and surface hardness in a certain temperature range, and good dimensional stability. Most ABS resins still have considerable impact strength and toughness at – 40 ℃. The temperature range of their products is – 40 ~ 60 ℃. ABS plastics have high molecular weight, good physical properties, easy processing and molding, and good printability.
3. Screen printed polyethylene (PE) plastics of polyethylene and polypropylene plastics: polyethylene plastics are widely used and can be made into various finished products through extrusion, injection and other molding processes. The molecular system of polyethylene is a long chain of methylene, which contains a certain amount of side groups. The longer the side groups in the polymer chain, the lower the crystallinity of the polymer. That is to say, the higher the density of polyethylene is, the worse it is for surface finishing. Polyethylene is not clear in many solvents, but when the temperature is over 70 ℃, polyethylene can be slightly dissolved in toluene, amyl acetate and other solvents. This property of polyethylene provides conditions for surface finishing. The adhesive force of the ink film on the plastic surface can be improved by soaking the plastic in a heated solvent to make its surface swell and destroy part of the crystallization. The mixture of fuming sulfuric acid, concentrated nitric acid, chromic acid and sulfuric acid can slowly act on polyethylene at room temperature; sulfuric acid and nitric acid can quickly destroy polyethylene at 90-100 ℃; the mixture of potassium lead, sulfuric acid and distilled water can soak polyethylene plastic at 70-75 ℃, which is beneficial to enhance the adhesion of ink film on the plastic surface.
Polypropylene (PP) Plastics: polypropylene has been one of the important varieties of plastics for many years. Applicable to all forming methods. It can be used for all kinds of pipes, boxes, films, fibers, etc. Industrial polypropylene has high spatial regularity, high crystallinity, isogenic index in the range of 89-95%, and a small amount of non crystalline random structure and low crystalline solid block structure macromolecular chain. When the melting point is in the range of 170-175 ℃, the glass transition temperature of isotactic polymer is – 13-0 ℃, while that of syndiotactic polymer is o ℃. Concentrated nitric acid and fuming sulfuric acid can etch polypropylene. At higher temperature, they can dissolve in aromatics and chlorinated hydrocarbons. Room temperature can only make them expand. Acids and esters also have some corrosion effects on it. With the increase of isotactic polymer content, the solvent resistance also increases.
Generally speaking, polyethylene and polypropylene are non-polar molecular materials with high crystallinity and low surface tension. There are no polar groups like carbon group, carboxyl group and hydroxyl group in their molecular structure. Compared with polyethylene, polypropylene surface coating is easier.
4. Screen printed electronic products of plastic parts of electronic products, especially radio products such as radio, recorder, television, etc., have high requirements for appearance. Art designers attach great importance to the appearance decoration of products. However, there are few technologies used in the appearance decoration in China, which limits the thinking of art workers, so that they can only change the appearance of products through the size of products, the use of various lines, and the limited color of plastic itself. After the development of plastic screen printing, it brings convenience to the decoration of electronic products, so in recent years, plastic screen printing of various electronic products in China has been widely used.
5. In recent years, the screen printing of plastic signs, plastic signs and decorative parts for screen printing graphics and characters after plastic molding have developed rapidly. For example, silk screen printing on PVC rigid board, polycarbonate, ABS, plexiglass and modified polystyrene plastic pressing parts has been widely used, and good decorative effect and economic benefit have been achieved.Screen printing of soft and hard plastic parts ① screen printing of plastic hose. There are several printing methods for plastic hose, the main method is heat transfer printing. The heat transfer process is to use sublimation dye ink or other materials to print the image and text on the transfer paper first, and then attach it to the substrate, and heat it from the back of the transfer paper to sublimate the paper dye and transfer the image and text to the substrate. After the surface treatment of the plastic hose, the transfer paper passes between the hose and a heated iron plate. The heated iron plate pushes the transfer paper to the hose, and the heat completes the transfer. After transfer, the hose enters the drying device, and the drying temperature is generally about 65 ℃. ② Silk screen printing of soft plastic. Soft plastic is often used to make toys, such as inflatable cartoon toys. When making, the silk screen pattern is usually first printed on the soft sheet plastic, and then cut and heat formed. The thickness of materials used is generally 0.8-3.0mm.If the screen printing with more than two colors is carried out, most of the plastics will stretch and contract, resulting in the chromatic error between the second color and the first color. This kind of chromatic error makes the commodity lose its original value and cannot be put on the shelf as a qualified product. For this reason, multi-color printing can only be carried out by using a long printing machine which can fix soft plastic. For long stage printing, the substrate should be fixed with adhesive. It is worth noting that the toy printing must use the non-toxic and harmless ink specified in the relevant standards. ③ Screen printing of hard plastic products. There are two kinds of hard plastic products: hard plate and molded product. Tickets, signboards, instrument dials, cosmetics containers, etc. are made of hard plastic.
7. The surface material of the screen printing panel of the instrument panel may be metal, various plastics and paints, etc. select appropriate ink, and screen some words and figures on the panel to indicate some functions of the instrument and equipment, and beautify the panel at the same time. Screen printing text and graphics requirements clear, good adhesion, wear-resistant, but also the requirements of soft and elegant tone, give people a sense of beauty. Here we mainly discuss how to improve the quality of panel by silk screen printing.
8. Silk screen printing of color polyester signs is a new type of signs developed rapidly in recent years in China. Because of its bright color, good decoration, easy paste, simple manufacturing method, low cost and other advantages, it is widely welcomed by the majority of users, and has been widely used in high, medium and low-grade electronic products, household appliances, and cultural goods. At present, many specialized factories in China have produced this kind of label. However, because the production processes of these factories are designed according to the needs of large-scale label processing, for those polyester label products with large variety and small quantity, they can not adapt to either the processing technology or the production cost. This paper introduces a screen printing technology to print color polyester label, which can be used as a reference for manufacturers engaged in small batch and multi variety color polyester label.