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.
Polyethylene film is a colorless, odorless, odorless, translucent non-toxic insulating material, used in a large number of bags; food bags, can also be made into a variety of containers. It is an inert material, so it is more difficult to print and must be processed before it can print better results.
PVC film has good light resistance and aging resistance and has good tear resistance. It is breathable. It is a clean, colorless and transparent film. It is usually added with plasticizer. It is soluble in acetone. , a solvent such as cyclohexanone. Therefore, it can be printed with an ink made of a polyvinyl chloride resin. Suitable for packaging bags, book covers, etc.
Polystyrene film is a soft and tough film, clean, colorless and transparent. When it is free of plasticizer, the film is always soft, freeze-resistant, and stored without aging. It is made by oxidative polymerization of synthetic binder ink during printing. The blot fastness is good.
Polyester film is colorless, transparent, moisture-resistant, gas-tight, soft, strong, acid-base oil ester and solvent, and is not afraid of high and low temperature materials. After EDM treatment, it has better surface fastness to ink. . Used in packaging and composites.
Polypropylene film has good gloss and good transparency, heat-resistant acid and alkali, solvent resistance, friction resistance, tear resistance, and gas permeability. It can not be heat sealed when it is lower than 160 °C.
Nylon film is stronger than 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 (reheating of food) 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 their affinity for inks is relatively poor, 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.