Commonly used plastic films are polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyester film (PET), polypropylene (PP), nylon, and the like. The performance of various plastic films is different, the degree of difficulty in printing is also different, and the use as a packaging material is also different.
1. Polyethylene film is a colorless, odorless, odorless, translucent non-toxic insulating material, which is widely used as a packaging bag; food bags can also be used to make various containers. It is an inert material, so it is more difficult to print and must be processed before it can print better results.
2, PVC film film light resistance, aging resistance is better and has better tear resistance, can be breathable, is a clean, colorless, transparent film, generally added plasticizer, it is soluble In acetone, cyclohexanone and other solvents. Therefore, it can be printed with an ink made of a polyvinyl chloride resin. Suitable for packaging bags, book covers, etc.
3, polystyrene film is a soft and tough film, clean, colorless and transparent, without plasticizer, the film is always soft, freeze-resistant, storage is not aging, printing using oxidative polymerization of synthetic binder ink, The print fastness can be better.
4, polyester film is colorless, transparent, moisture-resistant, airtight, soft, strong, acid and alkali-resistant esters and solvents, materials that are not afraid of high and low temperature, after the electric spark treatment, the ink has a better surface Fastness. Used in packaging and composites.
5, polypropylene film has good gloss and good transparency, heat-resistant acid and alkali, solvent resistance, friction, tear resistance, breathable, can not be heat sealed below 160 °C.
6. The strength of nylon film is larger than that of polyethylene film, odorless, non-toxic, impervious to bacteria, oil, ester, boiling water and most solvents. It is generally used for load-bearing, wear-resistant packaging, and retort packaging (food re- Hot), it can be printed without surface treatment.
Polyethylene has essentially no polar groups and is a non-polar imprinting. In polypropylene molecules, each structural unit contains a methyl group, which is a weakly polar group. They are also non-polar polymers, so they have poor affinity for inks, so they must be processed before printing to obtain a satisfactory print before printing.
Most of the treatment methods are by oxidation, which increases the polarity and changes the surface structure. Specific treatment methods include discharge (commonly known as corona, electric spark), flame method, ultraviolet radiation method, acid (sulfuric acid, chromic acid) treatment, and the like. The discharge method is relatively simple and popular.