What is the protective film curing?
Curing is a process in which a composite film is placed in a drying room (curing chamber) to crosslink the main component and curing agent of the polyurethane adhesive and interact with the surface of the composite substrate. The main purpose of curing is to make the main agent and the curing agent react fully for a certain period of time to achieve the best composite strength. Secondly, remove the low boiling point residual solvent, such as ethyl acetate.
The curing control is mainly the control of the curing temperature and the curing time. The curing temperature and the curing time are determined by the properties of the adhesive used and the final performance requirements of the product. Different adhesive types have different curing temperatures and times. If the curing temperature is too low, below 20 ° C, the reaction of the adhesive will be extremely slow. If the curing temperature is too high, the substrate film additive precipitates, which affects the performance of the composite film and increases the odor. Too long curing time will also affect the performance of the composite film and increase the odor, which is mainly caused by the precipitation of processing aids in the polyethylene film.
Isaac believes that the curing conditions also depend on the following factors:
1. PET, BOPA, AL, CPP and other films have good heat resistance, high shrinkage temperature, so the curing temperature can be improved. However, the curing temperature of LDPE, BOPP, EVA, etc. should not be too high.
2. The curing time of protective film can be longer when the amount of glue is high.
3. The curing time of protective film rolls can be appropriately reduced.
4. The curing time of protective film product with longitudinal ribs can be lengthened.
5. When the film thickness and the diameter of the film roll are large, the curing time should be appropriately extended.
6. The curing time can be appropriately extended to reduce the amount of residual solvent.
7. Adjust the curing time according to the use of the product.
There is also an accelerated curing that is used in production control. Take the newly produced composite film about 1 meter long, full width, and place it in an 80 degree oven for 30 minutes. Check its appearance and peeling and find problems in time, then take measures. This is also an indispensable part of dry compositing process management.
The following are requirements for the curing room:
1. The size and position of the curing chamber should be constructed according to the convenience of turnover storage. To facilitate the entry and exit of the film roll, the door should be convenient to open.
2. The height of the curing chamber is generally 2 - 2.5m, topped into a tower shape, leaving 5-10cm of venting holes upwards, can be directly through the outdoor. Or add a small exhaust fan for timing exhaust to discharge the curing room odour.
3. The ceiling of the curing room should be equipped with a ceiling fan. The rotation of the ceiling fan can make the temperature of the curing chamber uniform, and can destroy the slightly cold air layer wrapped around the protective film.
4, The shelf of the curing room can be laid flat or stereoscopic shelf type, depending on the transportation conditions of each enterprise. But the film roll must not be directly erected or lying on the ground;
5. The thermal insulation of the curing room's four walls, doors, roofs and etc., generally uses perlite, foam board and etc. The function is to increase the time of insulation, power saving, cost reduction and uniform temperature.
6. Heating control. The curing chamber can be electrically heated, steam heated, heating heated and etc. No matter what kind of heating, it should be equipped with a temperature automatic control device. The mercury thermometer should be used indoors to check whether the temperature is consistent with the setting. The high heat part should be kept at a certain distance from the protective film roll or add a baffle to prevent partial overheating of the protective film roll.