There is a critical temperature for the crosslinking reaction of polyurethane adhesive, which is generally introduced as 18-19 ℃. When the temperature is increased, the reaction rate can be accelerated. Theoretically speaking, the reaction rate is doubled every 10 ℃, so many adhesive manufacturers require the curing temperature to be about 45 ℃.
The reasons for poor curing may be: the curing time and temperature are not appropriate, the water in the solvent damages the curing agent, the weather is humid, the water condenses into the glue liquid, and the ratio is not accurate.
There is another phenomenon that needs to be noted: the composite is very good, the aging state is also good, the peeling force is also OK, but when making bags, it is found that the heat seal is in the wrinkle state or the product is wrinkled after a period of time. The reason is that the curing state is not good, the adhesive does not fully react into large network molecules, only partially solidified. At this time, from the peeling force, the strength is good, but the molecular weight and state of the adhesive layer is in the hot melt adhesive state and creep state. With the change of the external environment, it loses the binding force on the upper and lower membranes or wrinkling occurs under the action of different shrinkage stress between the two membranes for a long time, resulting in wrinkling. Incomplete curing is basically caused by the above reasons.
In addition, because of the strong water absorption of polyamide (nylon) compounds and the formation of hydrogen bonds, as long as there is water invasion, water can not volatilize again, which will seriously affect the curing effect. Therefore, in the process of packaging, storage, printing, use and compounding of nylon film, attention should be paid to the factors such as the moisture of preservation, packaging and solvent, weather humidity, etc.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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