(1) The surface tension of the film substrate is low
The low surface tension of the film substrate is one of the most common factors causing the low peel strength of the solvent-free composite products. Therefore, when the peel strength of the composite product is found to be low, the surface tension of the substrate should be checked first. If the surface tension of the substrate cannot meet the minimum requirements of the composite, it should be corona treated. If the surface tension of the substrate still fails to meet the requirements after corona treatment, then The substrate should be replaced before laminating.
(2) The ratio of the two components of solvent-free composite adhesive is improper
The improper ratio of the two components of the solvent-free adhesive is also a common reason for the low peel strength of the composite products. The improper distribution ratio of the two groups of adhesives and the poor chemical reaction of the adhesive during aging will inevitably lead to the low peel strength of the composite products, Therefore, if the surface tension of the substrate is OK, once the peeling strength is found to be poor, the proportion of the components of the adhesive should be considered first, and carefully check whether the ratio of the main agent of the adhesive to the cross-linking agent is within the range of the reference value provided by the adhesive supplier. If it deviates from the reference value, it should be adjusted in time.

It is self-evident that the accuracy of the two-component adhesive ratio is directly related to the product quality after compounding. In order to ensure the accuracy of proportioning, automatic glue supply and mixing system are generally used. The mixing pump (whether plunger pump or gear pump) in the automatic glue supply and mixing system is generally equipped with an automatic alarm system for the imbalance of glue liquid ratio. The new rubber pump will not have problems when it is used. However, with the extension of service life or the failure of relevant guarantee measures, the mixing pump may have problems (the mixing pump will not alarm due to the imbalance of the adhesive ratio).

In this case, if there is no necessary and timely monitoring means, there will be a large number of quality accidents; ordinary physical property testing feedback is slow, generally 24 hours after the results will be known, if there is a problem, then such a long time of loss is also great. In order to make up for this kind of defect, the most original method is to weigh and proportioning manually at fixed time, which is simple and effective. However, this method is suitable for implementation before startup, but it is not convenient to implement in equipment operation. Wu Xiaojun and others put forward a monitoring method for the actual proportion of adhesive components, which has a great reference value for actual production, that is, to use refractometer to test the refractive index of the adhesive to observe whether the component proportion of the adhesive is abnormal. As long as the proportion of the two components of the adhesive is determined, at a certain temperature, the refractive index of the mixed glue is certain. Although in the process of solvent-free compounding, due to the influence of temperature and test time, the refractive index will have some changes, but there are rules to follow. If the proportion of the adhesive changes significantly, the measured refractive index of the glue will also change accordingly.
The refractive index detection can be carried out at any time without affecting the on-line production, and the operation is very convenient. Once the proportion of the two components of the adhesive is found to be abnormal, remedial measures can be taken in time (Abbe refractometer is generally used for solvent-free adhesive refractive index test instruments, and Abbe refractometer has many domestic brands for selection).
(3) Other factors affecting peel strength
Other common factors affecting peel strength are as follows:
① The setting of curing temperature and time is improper or the control in the production process is not strict, and the curing of adhesive is not good. Check whether the setting value of curing temperature and time is within the range recommended by the adhesive supplier. If the curing temperature is too low or the curing time is insufficient, it is necessary to increase the curing temperature and prolong the curing time.
②  The insufficient amount of adhesive is also one of the reasons for the low peel strength of composite products. After eliminating the possibility that the peel strength of composite products decreases due to the above factors, the adhesive loading amount can be increased to improve the peeling strength of composite products (the glue loading amount of transparent composite products for light packaging is about 1.2g/m2, and that of boiled products is 1.4g/m About 2, the glue amount of printing composite products is 1.5-2 0 g / m2, the composite of high-temperature cooking film or aluminum plating material is generally more than 2.0 g / m2. When the glue amount is lower than the required empirical value, the peel strength of the product will be affected. Of course, the glue loading amount of the specific product is slightly different due to the actual situation of different manufacturers). If the coating amount of adhesive is properly increased, the problem of peeling strength decline can not be solved, and the adhesive products should be applied Make investigation, contact the adhesive supplier or other adhesive manufacturers in time to replace the adhesive.
③ If the base material is multi-layer structure, if the bonding force between the layers is low and the peeling strength between the base materials is poor, the peeling force of the composite products must also be low (the peeling failure occurs at the low interlayer bonding strength of the substrate). In this case, the above measures to improve the peel strength of solventless composite products will be powerless. For example, BOPP is usually a multi-layer structure. If the bonding force between BOPP layers is poor, when the solvent-free composite products such as BOPP / PE are tested, there will be no peeling at the adhesive, but there will be peeling between BOPP layers, which will cause the phenomenon of low peeling force, which shows that the peel strength of composite products is poor.
A method to judge whether the low peel strength of composite products is due to the low bonding strength between the substrate layers is proposed in the literature. It is pointed out in the literature that there is a kind of adhesive dye which can dye polyurethane materials and show red, while nylon film will show yellowish brown, other films will not. This dye is often used to determine which side of the substrate the adhesive stays on.For BOPP / CPP composite film, the film was peeled off without breaking the BOPP and dyed with dye. The results showed that the peeling off place was not the interface of adhesive, nor the interface after ink (polyurethane system) transfer (because solvent-free adhesive and polyurethane oil should show red after dyeing), but BOPP The film was exfoliated between layers. This conclusion can also be verified by further experiments: after the peeling film is lightly rubbed back and forth with sandpaper on the side containing CPP, the adhesive layer is exposed after the sandpaper rubs off a layer of BOPP on the surface, we can observe that the sanding place is red. In this case, the problem of low peel strength can only be solved by replacing BOPP film with good interlayer adhesion.
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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