The decrease of adhesion force and poor peel strength of the composite film are related to many factors. Such as: the influence of adhesive, composite substrate surface tension value not meet the requirements, affect peel strength, the operation process is not standardized, the influence of drying temperature, the temperature of hot steel roller is not appropriate, and the influence of film substrate additives, etc. Now give analysis and find the appropriate solution to make the peel strength of poor failure phenomenon to the lowest point.
The variety and quality of adhesive are not suitable for the substrate to be compounded, which affects the peel strength
The suitable substrate and adhesive should be selected for different applications of composite film. For example: when there is no aluminum foil in the composite, the general adhesive can be used. If there is aluminum foil composite, and the final purpose is to package sour and spicy food containing liquid (such as pickled mustard, juice, soy sauce, peanut, etc.), the special adhesive for aluminum foil with anti acid and spicy substances should be selected. When selecting special adhesive for aluminum foil, the adhesive with higher molecular weight, more uniform molecular weight distribution, good solvent release and good coating performance should also be considered. Although the adhesive with small molecular weight has good coating performance, it has strong molecular activity, which will pass through the extremely thin aluminum layer, resulting in the decrease of peel strength and adhesion force. If the composite bag is to be sterilized by high-temperature cooking, the high-temperature resistant (121 ℃ or 135 ℃) cooking adhesive should be selected, and the general adhesive must not be used. The general adhesive is not resistant to temperature, and the composite film will be layered under 80 ℃, which can not meet the requirements of packaging for peeling strength. Our company often uses pu1750 and pu1875 adhesives produced by Huaguang resin company of Zhejiang New Oriental ink group for high temperature cooking and sterilization packaging. The effect is good. It can reach 10-12n / 15mm in PET / CPP structure and 10-12n / 15mm in PET / Al and NY / Al structures.
For the composite structure of 15 μ PA / 70 μ m LDPE, it is effective to use pu-1875 polyurethane adhesive without 300 type. Several points should be paid attention to when using the adhesive: 1) the surface of the film after corona treatment should reach more than 3.8 × 10 ˉ 2n / M; 2) the diluent usually uses ethyl acetate or ethyl acetate, the water content should not exceed 3 ﹤ 10 ˉ 2n / m 3) do not mix solvent containing active hydrogen into the glue. For example: water, alcohol, amines; 4) pu-1875 adhesive ratio of the main agent: curing agent: Acetate = 1:0.2:1.8 (weight ratio).
The poor penetration of the adhesive to the ink, floating on the surface of the ink, and poor adhesion fastness between the ink and the substrate, will also lead to lamination of the composite film, which is manifested in the place with ink, especially the multicolor overprint. The ink is pulled off by the adhesive. The use of high solid content adhesive has sufficient time to penetrate into the ink layer and reach the substrate surface. Increasing the amount of glue properly can improve the composite fastness. It is also one of the methods to solve the problem by selecting appropriate ink and improving the surface tension of substrate to improve the ink adhesion fastness. In the process of compounding, it is required that the adhesive has good fluidity and flattening property. If the adhesive is deteriorated, turbid and white and emulsified, it can not be used again. Therefore, proper amount of adhesive must be prepared according to the needs.
Insufficient amount of glue, uneven coating will directly affect the adhesion and peel strength

Insufficient coating amount and uneven coating of adhesive will also lead to the decrease of peel strength and adhesion force, which is the most easy to appear in the use of one component hot melt adhesive, which can not be ignored. When using one component hot melt adhesive, the concentration of main adhesive will directly affect the peeling strength. We notice that if the inner layer thickness of BOPP / OPP, BOPP / vmopp and BOPP / OPP composite films is used, the peeling strength will be reduced When it is more than 30 μ m, the peel strength decreases most easily. If one component adhesive is used, a small section of the finished product should be taken for stripping test during the process of compounding, and corresponding records should be made at the same time. In general, the ratio of main adhesive to ethyl ester is 50:50, and the effect is good. The amount of glue is determined by the mesh volume of anilox roller, and is closely related to the operation concentration. If the adhesive concentration is high, the substrate tension value is appropriate, the amount of glue is moderate, and the peeling strength of the composite film is still not ideal, it should be considered to replace the anilox roller to increase the amount of glue. The general specifications of the roller are 80 μ m, 100 μ M, 120 μ m and 140 μ m, which can be adjusted or selected according to the actual composite.

If the diluent purity is not high enough, the composite peel strength will be affected
The role of diluent is to increase the fluidity of the adhesive, improve the spreading ability, better coating uniformity, and make the glue liquid better infiltrate with the base material. If the diluent is not pure enough and contains active substances such as water and alcohol, a part of curing agent will be consumed, resulting in the imbalance of the actual proportion of the main agent and curing agent in the adhesive, and the adhesive force is reduced. There are three points in the selection of solvent Reference from peers: 1) regular and quality guaranteed manufacturers must be selected for purchase; 2) after purchase, sampling inspection shall be conducted for each barrel, and it is forbidden to use active substances containing water or alcohols. Only solvent with high purity can ensure strong adhesion of composite membrane; 3) before use, the solvent must be clean, and if there is dirt, it is better to filter or separate Be careful not to affect the coating effect and peel strength.
Effect of drying temperature
In the process of compounding, the temperature of hot pressing roller in drying channel should be adjusted according to the actual situation. Generally, the temperature of hot pressing roller should be controlled at 50-70 ℃. The more complete the solvent volatilization is required in the drying device, the peel strength will also be increased accordingly. The temperature out of control will also affect the peel strength, and the adhesion force will be reduced. Generally, the temperature of drying inlet should be 60 ℃, while the temperature of zone 2 and zone 3 should be increased accordingly. If the temperature of inlet and outlet is too high, only the surface of adhesive film is dried, and the inner layer cannot be dried, which not only affects the peeling strength, but also produces peculiar smell.
The corona treatment of plastic film is not enough, which affects the peel strength
Poor corona treatment and low surface tension of plastic film will lead to low adhesion fastness of ink layer and low bonding strength of composite film. Before putting the film into operation, the surface tension value must be increased to more than 3.8 × 10 ˉ 2n / m, and it is better to reach 4.0-4.2 × 10 ˉ 2n / m, because 3.8 × 10 ˉ 2n / M is the minimum requirement, and the film with surface tension lower than 3.8 × 10 ˉ 2n / M can not make oil at all Ink and adhesive completely spread, the composite product can not meet the requirements of peel strength. There are usually two methods to detect the surface tension of the film: 1) dyne pen test, the pen liquid of the dyne pen is usually red, with specifications of 3.8 × 10 ˉ 2n / m, 4.0 × 10 ˉ 2n / m, 4.2 × 10 ˉ 2n / m, 4.4 × 10 ˉ 2n / m and 4.8 × 10 ˉ 2n / m. if the pen liquid on the film does not shrink, uniform and has no fault, the surface tension of the film has met the requirements If the solution shrinks, disappears, is uneven and discontinuous, it indicates that the treatment is not enough; 2) test with BOPP single-sided adhesive tape, stick the BOPP single-sided adhesive tape on the surface of the film to be tested, and then tear it. The corona treated film usually has low peeling sound and firm adhesion, on the contrary, it is not firmly pasted and easy to peel off. This test method relies on experience and is not suitable for testing pet, PA and other films. The base material which does not meet the requirements of corona treatment must not be compounded, because the peeling strength of the packaging product can not be met after lamination. The surface tension values of common substrates are: bopp3.8 × 10 ˉ 2n / m, pet5.0 × 10 ˉ 2n / m, pa5.2 × 10 ˉ 2n / m.
Too much residual solvent affects the peel strength and adhesion
If there are too many residual solvents, many tiny bubbles will be formed after compounding, which will cause the adjacent composite substrate to separate, delamination, and the more bubbles, the lower the peeling strength. In order to improve the peeling strength, it is necessary to reduce the generation of bubbles. The generation of bubbles is related to many factors, such as uneven glue application, low temperature of drying channel, low temperature of hot pressing roller and inappropriate indoor temperature and humidity. Generally, the indoor temperature should be controlled at 23-25 ℃, and the relative humidity should be controlled at 50% - 60%. In addition, avoiding the use of high boiling point solvent can also reduce the generation of bubbles. In conclusion, in order to improve the peel strength and adhesion strength, the residual solvent should be reduced as much as possible.
Incomplete aging affects peel strength
After curing, it is also called as compound adhesive. If the curing is not complete, the peeling strength will also be reduced. Incomplete aging has two meanings: 1) the curing temperature is low; 2) the curing time is not enough. Generally speaking, the composite products should be aged at 50-60 ℃ for more than 48 hours, and some even need longer time to achieve satisfactory results. It is noted that the final peel strength of the composite film can not reach 3.5n/15m no matter how long it is stored at low temperature. If the ambient temperature is raised to 55 ℃ and stored for 4 days, the peel strength can reach 6N / 15mm.
Effect of additives in plastic film
The additives in the plastic film can also affect the adhesion fastness, and this effect will appear after a certain period of time, generally after 7 days, and there is a gradual downward trend. When polyethylene, polypropylene and other films are pelletized or made, some auxiliary agents, such as antioxidant, stabilizer, anti adhesion agent and opening agent, should be added. These additives are low molecular substances, which will gradually penetrate from the inside of the film to the surface over time. A thin layer of powder or paraffin material can be found when you touch it with your hand. It is slippery and white. If you wipe it with a cloth soaked in ethyl acetate, it will be wiped off. Through observation, we found that the amount of additive migrated out of the film in a short time is not much, which will not cause the decrease of the adhesion fastness. However, after a long time, the migrated additives will isolate the adhesive film from the base film. The original bonding state is destroyed and the composite fastness is reduced.In order to solve this problem, it is necessary to control the feeding, choose the raw materials without or less additives, and do not add the opening agent artificially when processing the film. There was such a failure. The washing powder packaging bag did not have poor bonding fastness at that time. However, after the finished bag was filled with detergent, the lamination of printing substrate and composite substrate appeared after storage for a period of time, and even the heat sealing part was also cracked, resulting in the leakage of washing powder. The powder is mainly composed of anionic surfactant, fluorescent agent, nonionic surfactant, alkaline buffer, water softener and efficient stain suspending agent. First of all, it is considered that the problem of the composition of the washing powder / PEM is in line with the technical requirements of the composition of the washing powder. Therefore, the special pet printing ink was selected for printing, and then starting from the adhesive, compounding and curing again, the peeling strength test was carried out, and then the washing powder was loaded for storage and extrusion test. The results showed that the failure was eliminated, the packaging bag was no longer layered, and the peel strength met the requirements. It can be seen that selecting composite substrate and ink according to different contents can solve the problem of poor peel strength A method of.
There are many factors that lead to the decrease of adhesive force and poor peel strength of composite film, such as the imbalance of adhesive ratio, insufficient amount of adhesive, uneven coating and low temperature of hot roller, etc., which may lead to the decrease of peel strength of composite film. In order to make the composite product have greater adhesive force and excellent peel strength, we must control every step, not only from material selection, ink, diluent, adhesive We should also have a conscientious and responsible attitude in operation.
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.
We uphold the integrity of cooperation, good quality, good service business philosophy, won the industry's approval, products sold to all over the world; welcome friends from all walks of life to inquire, visit our factory to investigate guidance and business negotiations.