As early as the 1940s, due to the shortage of silk screens during the war, some users began to use nylon and polyester mesh instead of silk. However, their development was carried out after World War II. With the use of people, its quality has also been improved, and the screen printing industry in many countries in the world are increasingly using them. Nylon is a thermoplastic fiber and belongs to the class of polyamides. It differs from silk in the number of fibers, silk threads are multi-fiber, and nylon threads are single-fiber. Single fiber yarns consist of one fiber, which is made up of multiple fibers twisted together. In general, multi-fibers, such as silk and cotton, have more “tooth” and are easy to attach to screen stencils, which have a relatively smooth surface and are difficult to affix to the printing stencil. There are many kinds of weaving structures of the screen, such as plain weaving, weaving, half-knitting, and the like. Today, nylon screens, which are used exclusively for screen printing, have a flat weave structure and a semi-woven structure. Nylon is highly adaptable, such as ceramic inks, dye inks, water-soluble inks, printed circuits, and all inks used in industry. Screen printers can use nylon screens alone or as a supplement to other screens. Because nylon is thermoplastic, the hot spot is about 455 to 482 degrees Fahrenheit (235 to 250 degrees C), so it may melt if used under excessive heat. In other words, if you must use the stencil after ironing, pay attention to the control of heat. At the same time, be aware that if you need to heat when tensioning the screen, also control the temperature. Nylon has high elastic strength, wear resistance and durability. Nylon silk screen can reach 10,000 India. Direct wire mesh can also reach 100,000 prints. The direct screen means that the emulsion is directly coated on the nylon screen. Nylon, like silk, is weak and should not appear concave. Not affected by alkalis, weak acids or organic solvents. These properties are also the reason why it can be used for dye printing. However, it is easily etched by acetic acid and formic acid and is soluble in phenol, cresol and methacrylic acid. Therefore, care should be taken not to contact these substances when using it. The high elastic strength of nylon fiber determines that it can make the diameter of the wire relatively thin, so that the diameter of the opening of the wire is also larger, which is more conducive to ink penetration through the screen. At the same time, the thinner screen line also makes it possible to produce high-line screens. Nylon can weave a screen with 16 to 465 threads per inch and 80 inches wide. Nylon mesh is usually white, yellow, and red. Since the single fiber thread does not absorb ink, the nylon screen plate does not easily clog the mesh and is easy to clean. The ink deposition corresponds to the thickness of the wire and the coating film. Because the nylon is thinner, the ink layer deposited on the printing surface is thinner and easier to cure and dry, so it can print more details. For example, the printing accuracy of NO.196 (77 lines/cm) nylon mesh is comparable to that of the NO.25XX silk mesh, and the amount of ink transmitted is equivalent to NO.10XX silk mesh. This shows that when the printer wants to use fine silk screens, it is better to use nylon mesh instead. Nylon screens are ideal for direct coating of screens. The stretch nets can be stretched into wooden net frames, metal net frames, floating net net frames, and some commercial net frames. In general, nylon should use a wet stretch net as tight as possible. Stretching the tight mesh will reduce the durability of the stencil, causing misprints, non-contact printing, and the problem that the screen cannot be properly separated from the substrate. Nylon should stretch 3% to 7% in both warp and weft directions when stretched. Finer screens should be pulled gently. Manufacturers recommend that mechanical and pneumatic screens be used to pull the net. When attaching nets and pulling nets, the screen line must be parallel to the four sides of the frame. Special pull networks require the use of pull rules. The following method can be used to pull nylon mesh. First, lightly pull the nylon mesh to remove the folds; then, mark the obvious pencil lines and pull them parallel to the four sides of the frame. Note that the pencil spacing should be set to 10 so that the percentage of draw can be clearly seen. For example, if the distance between two parallel lines in the width direction is 20 inches, and the line spacing in the length direction is 30 inches, if the degree of stretching is to reach 5%, the length and width direction of the stretching amount are respectively 31.5 inches. And 21 inches. Nylon is wetted with water after drawing and a reference line is drawn. Pull the four-cornered screen to be light so as not to scratch the screen. And the tension in the corners is smaller than in other places to prevent the corners from pulling too much. Nylon pull can be pulled wet or dry, but the silk screen must be wet, and the polyester screen does not require wet pull. Why should we emphasize the pull of the net? Because it determines the print screen's resistance to print and print quality. Cleaning Synthetic Wire Mesh Assume that the screen has been properly stretched on the frame, and the next task is to clean and degrease the screen to prepare for a better coating of the film or film. This step is especially important for synthetic materials such as nylon and polyester. In general, photosensitizer suppliers will explain how to achieve a good screen mesh pretreatment method. Although the sold nylon has been cleaned as much as possible, it is necessary to clean the screen before use in order to improve the quality of the stencil paste. The cleaning and degreasing of the nylon is performed after the screen is stretched over the frame. There are many ways to clean and degrease, the purpose is to make the screen has easy to attach "tooth." Screen printers in the U.S. and Europe use the following nylon cleaning and degreasing methods. This method is also recommended by manufacturers of nylon mesh screens. Manufacturers of direct coating sensitizers also recommend this method. 1. Caustic soda and detergent treatment The caustic soda and detergent powder treatment methods, while they look complicated, are actually simple. Apply a 20% solution of caustic soda (sodium hydroxide) to the front and back of a new stretched nylon mesh using a medium-hard brush or sponge. Wait 15 to 30 minutes. Note: Due to the relatively high concentration of caustic soda solution and its corrosive nature, it is advisable to use a long-handled brush or plastic gloves when coating, not to splash the solution into your eyes. In production, no matter what solution is used, it is safer to wear plastic gloves. After 15 to 30 minutes, the nylon mesh should be wetted with water again. Add enough kitchen detergent and brush or sponge to scrub both sides of the mesh. Some tiny abrasives can also be added to help coarsen the screen. Rough nylon uses strong wash strength. Care must be taken with finer screen cleaning, as these nylon threads may reduce some of the strength during processing. Kitchen detergents contain active agents that act as degreasing agents. After wiping, thoroughly flush the screen with a hose, wash away all the caustic soda and powder, pay special attention to the corners and edges of the frame flush, so as not to leave any residue. After the screen has been thoroughly rinsed with water, some household vinegar (5% to 6% vinegar) is applied to the nylon mesh for final treatment. Its purpose is to neutralize the caustic soda that has not been removed. Any remaining caustic soda will produce "pinholes" when exposed, affecting print quality. Finally rinse the vinegar solution with water. Also note that when applying vinegar do not use the same brush that is used to apply caustic soda. Use cotton or cloth. Recycling and degreasing of the nylon mesh used is different from the new nylon mesh. The 20% caustic soda solution should stay on the wire for 5 to 10 minutes, then rinse with strong water, neutralize with vinegar, and finally Rinse with water. This is because the used nylon mesh has good adhesion and does not require repeated roughening. 2. Phosphorus vinegar trisodium and detergent treatment This method is used to paste the treatment method before the photographic screen stencil. The stretched nylon is first thoroughly scrubbed with a hard cloth and a cleaner with fine abrasives, followed by detergent cleaning. The trisodium phosphonate powder is then sprinkled on the cloth or sponge and rubbed on both sides of the screen until all the powder dissolves. After the roughening of the powder, the powder should be thoroughly rinsed with a cloth with water. The cloth had 2% hydrochloric acid solution. After a few minutes, rinse the screen with water. After drying, the template can be pasted. 3. Toluene-based acid treatment In this method, nylon is first subjected to a roughening treatment with a cleaner containing fine abrasives, then washed with water to remove the detergent, and then a mixture of 10% methyl benzoate and 90% methanol is sprinkled on the screen. And grind it into the mesh until all the mesh is covered by the solution. After waiting for the screen to dry, the stencil can be adhered without rinsing with water. Another toluidine-based acid treatment is to coat the center of the dry silk screen with a solution of a little 5% of a cresylic acid solution in cotton for about 1 to 2 minutes. The solution is a few inches from the boundary of the frame. The toluyl acid is then washed off with water and dried before use. When using tolyl acid, be aware that when it is too strong, it will damage the nylon mesh. 4. Abrasive cleaners Some of the screen printing masks must be pasted, and only one kind of abrasive cleaner should be sprinkled on both sides of the nylon screen. Clean the sponge with a sponge until the surface of the nylon mesh is clean and slightly roughened. Then wash the detergent thoroughly with water and remove all abrasive particles. When the screen is dry, the stencil can be pasted. Note that nylon mesh cannot be ground more than once. 5. A bleached 8% to 10% aqueous solution of sodium hypochloroacetate can be applied to the nylon mesh for about 5 to 20 minutes. After the nylon is washed with water and dried, the stencil can be pasted. However, long-term and repeated use of bleach will reduce the strength of the nylon. 6. Other cleaning techniques 5% The mixture of caustic soda and liquid detergent is suitable for the degreasing treatment of nylon mesh. Before the film is applied, the mixture must be washed with water and thoroughly dried. Dissolve 5 cubic centimeters of sulfuric acid and 0.5 grams of sodium or potassium dichromate in 1 litre of water to prepare a cleaning mixture. This method is mostly used in Europe and is usually kept on the screen for 10 minutes. Then rinse the solution with water and dry. Some screen printers clean nylon webs using ordinary detergents that do not contain abrasives. They can also act as a cleaning agent, making the webs easier to apply. However, the detergent must be thoroughly removed before applying the film. Polyester mesh There is no universal mesh material, and each has its own advantages and disadvantages. However, in order to better meet the needs of the printer, people have made another synthetic screen, namely polyester screens, such as polyester screens. It has a variety of different wire meshes and has many advantages: good stability, good abrasion resistance, better mechanical strength, chemical resistance, and weather resistance than nylon mesh; higher stretch-tension levels, flatness stability Off-grid printing performance is also better than nylon mesh, which can be used for high-precision screen printing; it has good filming properties after cleaning and degreasing. In some jobs it can be used instead of metal cloth. It has both single and multiple fiber strands. This screen has a variety of brands, but also a variety of colors, such as white, anti-halberd, and orange. Since the synthetic screen is nailed to the frame, care must be taken when nailing so as not to scratch the screen. Just in case, it is best to use a cardboard strip under the nail. Adhesives can be painted, epoxies, and products suggested by the manufacturer. Polyester stretches about 2 to 3.5% when it is applied and stretched. To make the film very smooth can use chemical and mechanical methods. When using the cleaning method, a cleaning method suitable for nylon can be used, but it must be ensured that there is no damage to the polyester. Silica fine abrasives or mills can be used on new screens, and sponges must be lightly rubbed on both sides of the screen. After polishing, be sure to wash the abrasive thoroughly with water. In general, how to pretreat the screen, emulsion manufacturers have specific instructions. Metallic Polyester Mesh Metal Monofilament Polyester Mesh was developed in the 1970s. The entire screen has a metal plate with good abrasion resistance. It has wide adaptability and can be used directly, indirectly, directly or indirectly. Screen stencil. If you stretch the net in the required direction, you have space stability. It can be used to print thermoplastic inks that can be printed with nylon or polyester that cannot be printed. It is resistant to most inks, degreasing cleaners but does not have resistance to some solutions such as sodium hypochlorite, acids and concentrated alkalis. Therefore, be sure to follow the manufacturer's instructions when stretching, pulling, recycling, and other treatments. It is recommended that the screen be tested before work. In short, the easiest way to do it is to use it at work. The basic precondition for the use of nylon, polyester, or other screens is the importance and correctness of the screens. Do not cause the screens to weaken when cleaning the screens and degreasing. Some screen stencils require fine screen cleaning and only require a small roughening process. In addition, thorough removal of raffinate is also the removal of membranes, enzymes, or recycled liquid for screen regeneration.
