Complete list of inspection items and methods for vacuum composite packaging bags

Vacuum composite packaging bags are widely used for internal and external packaging of various products due to their good barrier, heat sealing, moisture resistance, acid resistance, alkali resistance and wear resistance. With the increasing requirements for the quality of vacuum packaging composite bags, packaging enterprises pay more and more attention to the quality inspection of flexible packaging composite bags. The editor of Dongguan Mingxin Packaging Material Products Factory will summarize the testing methods of composite bag products in combination with practice, hoping to help colleagues.

1. Visual inspection of appearance

Visual inspection of appearance includes inspection of flatness and transparency of composite bags. It is mainly used to detect whether there are obvious scratches and pinholes on the surface of the composite bag, and whether there is pollution at the sealing point.

Our company has a relatively complete set of visual inspection methods, as follows.

(1) Place the composite bag in the center of your hand, aim at the 40W fluorescent lamp and gently shake it. Through the reflected light on the surface of the composite bag, you can clearly find whether there are scratches or traces on the surface of the composite bag, which is often called "bag surface wire drawing" in the industry. If the wire drawing is serious, find the fault according to the actual situation, reduce the impact to Z low point, and ensure the product quality. The wire drawing phenomenon we found through observation is mostly caused by the unclean traction guide roller of the bag-making machine, so we must ensure that the guide roller is clean. In addition, the non-rotation of the guide roller will also cause wire drawing failure of the composite bag. The reason why the guide roller does not rotate is mostly caused by the lack of oil in the bearing, so good lubrication is the fundamental condition for the bearing to rotate.

(2) Check the flatness of composite bag. The specific method is to take several samples of finished bags and drop them "from the air to the ground", let them land naturally and clean, and observe the situation of composite bags after landing. If the composite bag bends, warps outward or arches inward when landing, it indicates that the flatness of the composite bag is poor, and vice versa.

The reasons for poor flatness are generally as follows: the high temperature of bag making has damaged the stress stiffness of the inner layer of the composite bag; The structure composition is unreasonable; The thickness of the material itself is uneven. We note that when the total thickness of PET/PE and BOPP/PET/PE composite is not more than 80 μ M, the phenomenon of poor flatness is easy to occur.

(3) Visual inspection of appearance also includes transparency inspection. Some products have no patterns in large areas, so transparency is particularly important. The test method for transparency is to take a finished bag and observe it through the indoor indirect light source. If there are "pits", "rings", "fog" and other phenomena in the blank, it means that the transparency is poor, and vice versa, it means that the transparency is good.

There are many reasons for poor transparency. For example, when compounding, due to the yellow or red color of the composite glue itself, the corresponding color deviation will occur when transferred to the composite bag, affecting its transparency; If the transparency of the material itself is poor and "foggy", it will also affect its transparency. Therefore, the quality of the material should be strictly controlled when entering the warehouse, so that unqualified raw materials will not enter 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-extrusion CPP.