generally, we just use our eyes to see the transparency of this roll of tape. If the transparency is good and there are no impurities (there are black spots or something.) It is made of first-class materials. The film is relatively thin, but it has strong tensile resistance. Can stretch 100%. On the contrary, it feels thick, but the tensile resistance is not enough. If it is stretched to 50%, it will break. Another is viscosity, which is made with professional instruments. Take a steel ball, put the tape on the plane at 30 degrees, and roll down naturally. The weight of the ball is different, and the longer the weight of the ball stays, the better it seems.
routine test items: initial viscosity, holding viscosity, and 180 degree peel strength.
the user has no one to test
the only items to be tested for sealing tape products on the market are viscosity and die thickness
in fact, the viscosity of sealing tape is mainly composed of three indexes: initial viscosity, holding viscosity and peel strength. This is also the basic three items stipulated in the national standard for the viscosity test of sealing tape or self-adhesive products. The corresponding instruments are called initial viscosity tester, holding viscosity tester and electronic peel tester (tensile tester). You can also select the corresponding sealing tape testing instrument according to your own needs
BOPP tape film thickness measurement is one of the basic testing items in film manufacturing industry. Other properties of the film are related to thickness. Obviously, if the thickness of a batch of single-layer films is uneven, it will not only affect the tensile strength and barrier properties of the films, but also affect the subsequent processing of the films. For composite films, the uniformity of thickness is more important. Only if the overall thickness is uniform, the thickness of each layer of resin can be uniform. Therefore, whether the film thickness is uniform, whether it is consistent with the preset value, and whether the thickness deviation is within the specified range have become the premise of whether the film can have some characteristic indexes
film thickness measurement can be divided into on-line measurement and off-line measurement. The off-line thickness measurement technology was first used for film thickness measurement. After that, with the continuous development of ray technology, online thickness measurement equipment installed with film production line is gradually developed. In the 1960s, online thickness measurement technology has been widely used, and now it is more able to detect the thickness of a coating. The on-line thickness measurement technology is completely different from the off-line thickness measurement technology in the test principle. The on-line thickness measurement technology generally adopts non-contact measurement methods such as ray technology, while the off-line thickness measurement technology generally adopts mechanical measurement method or measurement method based on eddy current technology or electromagnetic induction principle, as well as optical thickness measurement technology and ultrasonic thickness measurement technology
1. The more common online thickness measurement technologies are β X-ray technology, X-ray technology and near infrared technology
1> β Ray technology β X-ray technology is the first ray technology used in on-line thickness measurement technology. It has been widely used in on-line thickness measurement of ultra-thin films since 1960s. It has no requirements for measuring objects, but β The sensor is sensitive to the changes of temperature and atmospheric pressure and the fluctuation of the film. The equipment has high requirements for radiation protection devices, and the replacement cost of signal source is expensive. Pm147 source can be used for 5-6 years, kr85 source can be used for 10 years, and the replacement cost is about us $6000
2> X-ray technology is rarely used in film production lines. The X-ray tube has short service life and expensive replacement cost. It can generally be used for 2-3 years, and the replacement cost is about 5000 US dollars. Moreover, it is not suitable for measuring polymers composed of multiple elements, and the signal source is highly radioactive. X-ray technology is often used to measure single elements such as steel plate
3> Near infrared technology the application of near infrared technology in the field of on-line thickness measurement was once affected by the phenomenon of fringe interference, but now the near infrared technology has broken through the limitation of fringe interference on the measurement of ultra-thin film thickness. It can measure the total thickness of multi-layer film. Due to the characteristics of infrared technology, it can also measure the total thickness of composite film and give the thickness of each layer of material at the same time. Near infrared technology can be used for biaxially stretched films, cast films and multi-layer coextrusion films. The signal source is non radioactive and the maintenance difficulty of the equipment is relatively low
4> Online thickness measurement can obtain the thickness test data at the fastest speed. Through data analysis, timely adjust the parameters of the production line and shorten the start-up time. However, the online thickness measuring equipment must be equipped with a scanning frame matching with the production line, which limits the reuse of the online thickness measuring equipment to a certain extent. Moreover, the film production line often needs long-term continuous work, so the corresponding online thickness measurement equipment must work for a long time. In terms of equipment price, online test equipment is generally much more expensive than non online test equipment, and the operation and maintenance costs of the former are also relatively high
2. Off-line thickness measurement off-line thickness measurement technology mainly includes contact measurement method and non-contact measurement method. The contact measurement method is mainly mechanical measurement method, and the non-contact measurement method includes optical measurement method, eddy current measurement method, ultrasonic measurement method, etc. Due to the low price and small volume of off-line thickness measurement equipment, it has a wide application field
1> The mechanical thickness gauge adopts the most traditional thickness measurement method, with stable and reliable data and no selectivity for the sample. It can be generally divided into point contact type and surface contact type. It is essentially different from the non-contact thickness measurement method – it can apply a certain pressure (point contact force or surface contact force) to the measurement surface of the sample before thickness measurement, so as to avoid using the non-contact thickness gauge to measure those with certain compressibility When the surface of the material fluctuates greatly. The test accuracy of mechanical thickness gauge mainly depends on the accuracy of thickness measuring element. Its core element – measuring head and measuring face are very sensitive to small vibration, so the measurement accuracy has no significance in the environment with vibration source. In order to avoid its own vibration and reduce the influence of external vibration as much as possible, the equipment base is made of heavy and wide metal, which ensures the thickness measurement accuracy to a certain extent, but also brings some difficulties to the miniaturization and portability of mechanical thickness gauge. Ambient temperature and wind speed can also affect the accuracy of the sensor, so it must be used in the laboratory environment. Due to the different contact area between the measuring head and the sample, the force application of the measuring head and the force application speed are different. The same sample (assuming uniform thickness here) is likely to get different test re
sults by using different types of thickness gauges, which is mainly due to the different deformation rates of compressible samples under different conditions. Therefore, the test conditions and requirements of the referenced standards must be strictly implemented when using the mechanical thickness gauge
2> Eddy current thickness gauge and magnetic thickness gauge eddy current thickness gauge and magnetic thickness gauge are generally small portable equipment, which use the principle of eddy current and electromagnetic induction respectively. It is specially used for measuring the thickness of various specific coatings. There is a possibility of error when measuring the thickness of film and paper
3> Ultrasonic thickness gauge ultrasonic thickness gauge is also mostly small portable equipment. Using the principle of ultrasonic reflection, it can measure the thickness of metal, plastic, ceramics, glass and any other good ultrasonic conductor. It can work at high temperature, which is not available for many other types of thickness gauges, but it is selective for the type of test samples
4> Optical thickness gauge uses optical principle. In terms of test principle, optical thickness gauge can achieve extremely high test accuracy, but this kind of thickness gauge has extremely high requirements in use and maintenance: it must be far away from vibration source; Strictly prevent dust; Professional operation and maintenance, etc. The application range is narrow, and it is only suitable for composite films with few composite layers
5> The sales volume of off-line thickness measuring equipment is larger than that of on-line thickness measuring equipment, because its price is cheap, and compared with on-line thickness measuring equipment, off-line thickness measuring instruments can be transported and moved more conveniently; In addition, the use of off-line thickness measuring equipment does not conflict with the use of on-line thickness measuring equipment. The two can cooperate effectively and improve the qualified rate of products. For some samples, different results may be obtained by using different thickness gauges. On the one hand, the test principles of various thickness gauges are quite different. On the other hand, most soft packaging materials are compressible. Therefore, other types of thickness gauges except mechanical thickness gauges often have selectivity for the material of samples and poor universality
3. Characteristics of flexible packaging materials common flexible packaging materials are mainly processed and manufactured by polymers and paper products. Polymers are divided into three categories: rubber, fiber, and plastic. Rubber is characterized by high elasticity at room temperature, that is, it can produce great deformation under the action of small external force; After the external force is removed, the modulus of elasticity is about 105 ~ 106m2, and the modulus of elasticity is about 106m2. On the contrary, the elastic modulus of the fiber is large, about 109 ~ 1010n /m2, and the deformation is small under stress. The elastic modulus of plastic is about 107 ~ 108n /m2. Some deformation is reversible and some are permanent deformation. These three types of polymers are difficult to be strictly divided. For example, polyvinyl chloride is a typical plastic, but it can also be pumped into fiber and mixed with an appropriate amount of plasticizer to make soft products similar to rubber. Generally, the paper is soft and has certain compressibility, and the surface is uneven. It can be seen that both polymer and paper products will deform and be in a compressed state after being stressed, so flexible packaging materials generally have a certain deformation rate. Therefore, whether there is pressure on the measuring surface of the sample during sample thickness measurement will directly affect the test results
for film manufacturers, the thickness uniformity of products is one of the most important indicators. In order to effectively control the material thickness, thickness testing equipment is essential. However, the specific type of thickness testing equipment to be selected depends on the type of soft packaging materials, the manufacturer’s requirements for thickness uniformity, and the testing range of the equipment.