Protective films are designed for temporary protection of products, home appliances, screens, metal surfaces from scratches, and dirt, which can spoil the appearance of the product or goods during transportation, storage and installation. While putting a product in operation, protective film have to be removed from the surface. It leaves no traces (if was properly selected).
Modern production technology of adhesive films follows the path of specialization, and provides for every specific type of problems in everyday life, trade, transport, industry, your specific type of adhesive film that meets the requirements of the consumer.
The protective adhesive films basically represent a thin polymer coating, on one side covered with an adhesive composition, which is capable of adhering to various surfaces.
What is the basis of a protective film?
As the base material of the protective films high density polyethylene (LDPE) is used.
Polyethylene - most inexpensive polymer for creating the base for an adhesive film. Polyethylene sufficiently durable, yet capable of significant distortion – as a result, film on this basis is able to stretch strongly, but irreversibly. Polyethylene - practically inert polymer, under normal conditions, it is resistant to all fluids. Polyethylene does not emit harmful substances, so it is widely used with food.
On the extruder a sleeve is blown with the width up to 1.5 m, consisting of 1 to 4 layers of p/e, which is wound in rolls up to 6000 m. To make a film of various colors (white, blue, green, black) including black and white (when different layers of p/e of a different color) different painters are added. At this stage, if necessary, in p / e some additives are implemented for protection from UV radiation.
Then, if you want to put a logo, these rolls are given to print. It is possible to apply both surface and interlayer printing, during which the film is laminated on top by another layer of p / e. With both types of printing, the method of its application - deep. You can print up to three colors. In this case, for each color cliché must be made individually.
Next step - application of the adhesive layer.
From what an adhesive layer of a tape consists of?
The adhesive layer provides adhesion of the film to the surface to which it is applied. Sticking phenomenon - it is a complex physical and chemical process that takes place at the interface between the adhesive and the solid surface. In science the term is used - adhesion, so substances used as a components of the adhesive layer, called an adhesive.
Adhesives used in the adhesive films, as well as their base have polymer nature. Depending on the chemical composition, there are usually three groups of adhesives:
- Rubber adhesives of natural or synthetic origin. Their closest analogue is the usual "rubber" glue. They have the highest adhesion to a variety of surfaces. Rubber adhesives retain their adhesive properties at the extremely low temperatures, up to -700C, which ensures their successful use in winter conditions of all climatic zones. However, they have insufficient heat resistance during heating. Rubber adhesives are successfully used indoors, but they are not resistant to UV radiation, thus limiting their use outdoors.
- Silicone adhesives. They are substantially more expensive than other types of adhesives, but have high heat resistance, which is essential where the adhesive film is exposed to high temperatures. Although silicone adhesives have weaker adhesion than rubber ones, their use is preferred in the case of bonding to the surfaces of silicone nature.
- Acrylic adhesives. A large group of polymers representing various esters of polyacrylic and polymethacrylic acids. Acrylic adhesives (because of their diversity) provide the greatest flexibility when used as adhesive layers. They are characterized by weak adhesion and weaker frost-resistance than rubber, but they are more heat-resistant and considerably more stable to UV light. Acrylic adhesives are widely used in protective adhesive films of temporary use and when the transparency of the adhesive layer is need to be ensured.
To apply the adhesive, rolls of p/e with logo are placed in a special machine, with a length of several tens of meters, on which adhesive solution and drying are applied. For the adhesive surface of the film held, it was treated by corona charge. Number of applied adhesive regulated by lineature of shafts.
After gluing rolls are rewound into rolls of the desired length (100 meters to 1000 meters), and then straight edges are cut according to the width dimension of the roll, and then roll is packaged.
How to determine the adhesive properties of adhesive tape?
Among the various laboratory methods for testing the adhesion of the film, the method of ASTM D-3330, based on the measurement of the detachment force of the adhesive film from the standard steel plate is the most widely used.
A film sample with the width of 25-50 mm, one end of which is left free is glued to the steel strip. To the free end an effort is applied, by using special equipment, and then the minimum load level, under the influence of which the film will peel off from the steel strip, is measured. This load serves as an indicator that describes the adhesive properties of the adhesive film. This indicator is called Peel Adhesion to steel and measured in grams (g) / (25-50) mm or in N (Newton) / (25-50) mm. When comparing different data, it is important to remember that 1H ~ 100g, while also paying attention to the number of mm, indicated in the denominator.
To the same polymer base of the adhesive film index of adhesion to steel can vary greatly, depending on the thickness of the adhesive layer and its brand. For example, protective films based on polyethylene with an acrylic adhesive possesses the index of adhesion to steel which can vary from 50 g / 50 mm to 2 kg / 50 mm, that is, 40 times.
Depending on the amount of applied adhesive, the following classes of protective films on the value of force peel adhesion to polished steel plate are distinguished:
- L (low) - 100 g / 50 mm
- ML (moderate low) - ~ 100-200 g / 50mm
- M (moderate) - ~ 200-350 g / 50mm
- H (high) - ~ 350-550 g / 50mm
- VH (very high) - ~ 550-800 g / 50mm
- SH (super high) - more than 1000 g / 50mm
With this range of the protective films, they are used at all possible surface types.
Protective films with low adhesion (L) are used to protect the following surfaces: acrylic sheet (PMMA), PVC sheet, ABS plastic, steel plates, anodized aluminum and other smooth shiny surfaces.
Protectors ML are used for protection of furniture fittings, smooth aluminum, tile, covered with a metal coating, surface conditioners and various household appliances.
Protectors M are used to protect galvanized aluminum sheets, artificial marble, plastic, and steel profile.
Protectors H are used to protect rougher materials, composite panels, aluminum sheets, laminates, PVC profiles, etc.
VH Screen Protectors are used to protect matte surfaces, profiles, surfaces treated with sand blasting method, and etc.
SH Protectors are used to protect carpet (with glue outside) car mats.