An indispensable part of the product packaging of composite bags. Composite bags have excellent barrier properties, heat sealability, moisture resistance, and are acid-resistant, alkali-resistant, and wear-resistant, so they are widely used in food packaging. With the increasing progress of everyone's request for the quality of composite bags, packaging companies have paid more and more attention to the quality of composite bags. So as a customer, where should you start when accepting a composite bag? What are the acceptance criteria? Today, Xiaoou will make an introduction to how to check the products of composite bags, and hope to help everyone.
The acceptance of the composite bag can be viewed from the visual appearance and sealing tightness, as follows:
The visual inspection of appearance includes the inspection of the flatness and transparency of the composite bag. It is mainly used to check whether there are obvious scratches and pinholes on the surface of the composite bag, and whether there is pollution at the seal. Our company has a more complete set of methods to check the appearance, as detailed below.
1. Place the composite bag in the center of your hand and gently shake it against the 40W fluorescent lamp. After the reflected light from the surface of the composite bag, you can clearly see whether the surface of the composite bag is scratched or traced. . If the drawing is severe, you should find the faulty location according to the actual situation, reduce the impact to the lowest point, and ensure the quality of the product. The wire drawing scene we found after investigation is mostly formed by the unclean guide rollers of the bag making machine, so we must ensure that the guide rollers are clean. In addition, if the guide roller does not roll, the composite bag will also suffer from drawing problems. The reason why the guide roller does not roll is mostly caused by the lack of oil in the bearing, so outstanding smoothness is the basic condition for the bearing to roll.
2. Check the flatness of the composite bag. The detailed method is: take several product bag samples for "air-to-ground" drop, let it land naturally (the site should be clean), and investigate the situation of the composite bag after landing. If the compound bag flexes when it touches the ground, warping outward or arching inward, it means that the flatness of the compound bag is poor, otherwise it means that the flatness is excellent.
The factors that cause poor flatness are generally the following: the bag-making temperature is too high, the stress stiffness of the inner layer of the composite bag has been damaged; the structural composition is unreasonable; the data itself is unequal in thickness. We have noticed that when the total thickness of the composite data of PET / PE and BOPP / PET / PE structure does not exceed 80 μm, it is easy to have a situation where the flatness deteriorates.
3. Visual viewing also includes transparency viewing. Because some products have no patterns on a large area, transparency is particularly important. The way to check the transparency is: take a product bag and investigate through the indirect light source in the room. If there are "pits", "rings", "fog" and other scenes in the blank space, the transparency is poor, otherwise the transparency is marked as outstanding .
The factors that cause poor transparency are many, for example: when compounding, because the color of the compound glue is yellow or red, the color shift will occur on the compound bag, which will affect its transparency; if the data itself has poor transparency , "Haze" will also affect its transparency, so the quality should be strictly controlled when the data is put into the warehouse, so that unqualified raw materials will not be put into the warehouse. In addition, the transparency of different composite raw materials is also different. For example, the transparency of cast CPP is much higher than that of blown co-extruded CPP.
Viewing the seal tightness
Slight small slits at the seals, if overlooked slightly in visual inspection, will bury the danger of food leakage in the future, so it is necessary to check the seal tightness of the composite bag. A common method is to spray a surface-active agent with a dye into the seal and investigate its penetration. If the color of the dye passes through the seal, it indicates that the sealing function is not good. On the contrary, it clarifies that the seal quality requirement is met. In practical work, we often use a smooth, burr-free small iron ruler 20 cm long, 5 cm wide, and 0.8 mm thick to push the seal tightly against it. If there are drops, perforations, etc. with a light touch, the sealing function is poor; if the seal still adheres to the proper sealing standard, the sealing function is outstanding.
Factors that lead to poor sealing function are: the sealing knife pressure is not good or uneven, this condition can be dealt with as long as the sealing knife spring pressure is adjusted; the low temperature will also make the sealing of the composite bag worse. We have noticed that when the total thickness of the composite data exceeds 80 μm, the problem of poor adhesion tends to occur during bag making, especially the structure of BOPP / OPP. If you want to ensure good product adhesion, you must have a uniform and stable sealing pressure and a suitable temperature.