Adhesive Quality Control Overview

Since the beginning of the 21st century, the adhesives industry has made considerable progress, and it has not been compared with the immature technological methods in the past. However, there are still the disadvantages of not being able to directly check the quality by visual inspection and must be tested in two ways, namely destructive testing and non-destructive testing.
1. The destructive inspection can be performed by using the same materials and adhesives as the product parts to inspect the test specimens. The process inspection test specimens undergo cleaning, assembly and curing processes along with the product parts, and the adhesive and adherend must be assembled at the same time. Cured in the same pressure or autoclave. The difference is that each part is labelled as part of the assembly. After curing, the label can be removed and the same test as the test sample can be performed. The test result is compared with the technical requirements. Unqualified parts are then subjected to non-destructive testing and the final trade-off is determined. Excluded parts do the damage of the system and study the actual problems of the parts.
Fokker's tests are closely linked to the strict control of operational processes and the sampling of bonded parts and the destructive testing of specimens. The level of quality control for special adhesive assemblies is related to their structural requirements. Critical joints are Destruction test high standard sampling and strict acceptance requirements for inspection, but the general method of testing adhesives does not have to be so strict.
The first step in quality control is to control the quality of the adhesive and quilt adherents that form the joints and perform the necessary checks and tests to ensure that the acceptance requirements are met. Samples of each batch of adhesive are bonded prior to use and subjected to destructive testing to ensure adequate bonding strength after proper curing. The storage conditions are carefully controlled so that the adhesives and adherends used in the bonding are qualified.
Strict process control ensures the correct operation of each batch of adhered parts during surface treatment, assembly and curing. The surface treatment process needs to control the temperature, the composition of the treatment liquid, the part soaking time, and then check the treated surface to determine the wettability. The assembly operation controls the size, positioning and pressure through a combination of process control and testing. The curing conditions are generally controlled by measuring the actual curing temperature and time with a thermocouple embedded in the adhesive layer. Although these rigorous controls do not fully guarantee the correct process operation, they have made it possible to meet the high standards required for the quality of each batch of parts.
The test specimens, which are labeled on the actual parts, perform the same bonding process with an assembly fitting that they represent. These specimens are subjected to destructive tests such as shearing, stretching or peeling. The measured strength represents the strength of each joint in a batch of assemblies. If the bond strength of the test piece does not meet the requirements, the entire batch of parts will be rejected. In addition, the destruction test only shows the quality of the initial product, but also through the sampling inspection of the assembly out of each process of the entire production line, in order to ensure good process and assembly conditions. This process control and sampling inspection method can determine the problems affecting the entire assembly, but it cannot evaluate the quality of bonding factors that affect individual joints or specific locations of specific joints.
2. Non-destructive test methods The non-destructive Fokker test method is introduced into inspection and testing, and it is possible to estimate various factors affecting the bond strength of individual joints. The main defect of the quality control of the existing bonding process is that it is impossible to detect the decrease of the bonding strength caused by the local poor adhesion. The root cause of this problem is poor surface treatment in some areas, non-uniformity of the surface of the adherend, or contamination of the treated adherend surface and the adhesive during the bonding process. Only process control cannot control these factors, and existing non-destructive tests cannot detect the strength reduction due to these problems. The defective product rate of the joints can be reduced through the strict control of materials and processes and the careful operation of the production personnel, but it cannot fully guarantee that the joints are of high quality. The solution is to develop this non-destructive test method, which measures the interfacial properties of the adhesive and the adherend and the adhesion of the adhesive film to the surface of the adherend. Only this non-destructive test method has been successfully studied. Strict process control, destruction test of the test piece, and non-destructive testing of each finished joint are combined to achieve the most reliable bonding and bonding structure quality. The guarantee.

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