Test and Research on soft plastic composite materials - permeability

4、 The test and control of air permeability of packaging materials are very important in medicine and food industry, which directly affects the quality of products Single film can not meet the overall demand of flexible packaging In recent years, multilayer composite film has been widely used in various fields with excellent barrier and chemical resistance, among which barrier material plays a key role Different packaging materials have different requirements for air permeability In the food industry, the important barrier of Zui is oxygen barrier, which is generally classified as 05cm3 / m2 · ATM · 24h (take oxygen permeability as an example), which is mainly used in milk, fresh-keeping film, special medicine and other packaging, 5-200cm3 / m2 · ATM · 24h is the medium barrier, which is mainly used in general food bags, and 200cm3 / m2 · ATM · 24h is the low barrier, which is mainly used in the packaging without any requirements Special packaging for cooking and disinfection is required There are many testing methods in the world, such as concentration difference method and pressure difference method 2 In the world, there are many brands of breathers, such as American mengkang, Danish PBI, Japanese Toyo precision machine, etc their calibration instruments generally use reference materials, and the storage requirements of reference materials are extremely strict, so it is difficult to calibrate According to a large number of test data, due to the difficulty of calibration between instruments, the comparability of test results is not strong, and the test time is long, and the price is high 3 Bty-b1 air permeability tester adopts high-precision sensing equipment micro differential pressure transmitter, uses eddy current principle to avoid the use of silicone oil, safe operation, avoid the shortcomings of traditional vacuum leakage, and the price is moderate And the pressure calibrator is used for calibration, which is intuitive, convenient and convenient The test method discussed below (taking bty-b1 air permeability tester as an example) is the differential pressure method The test principle is to maintain a certain gas pressure difference on both sides of the sample at a certain temperature, measure the gas pressure change measured at low pressure of the sample, and calculate the air permeability coefficient and air permeability The specific steps are as follows: 1 There is no wrinkle and the surface is clean on the sample and the sample with the diameter of 75mm 1.2 1.3 each group of 3 samples 1.4 samples are dried in an anhydrous calcium chloride dryer for 24 hours, or treated according to the product standard 2 Test condition 2.1 temperature: 25 ± 2 ° C or as per product standard 2.2 pressure: the pressure difference between the upper and lower chambers is 1atm 2.3 The gas type shall be selected according to the use requirements and shall be dried O2, N2 or other gases 3 test step 3.1 measure the thickness of the sample, at least 5 points, and take the arithmetic mean value 3.2 place the sample on the coarse filter paper (diameter: 66mm), seal it in the air permeability chamber, start the whole process of automatic test, and then pop up the air permeability tester report 4 The test data of air permeability can be used to guide the production of packaging film 4.1 the components of optional packaging film include basic resin such as LDPE, LLDPE, PP, BOPP, PE, etc.4.2 The barrier coating materials such as EVOP, PA and PVDC can be selected, among which PVDC is a high barrier transparent material approved by FDA to contact with food at present Taking BOPP as an example, the oxygen permeability after coating is reduced by 1000 times 4.3 the process research of barrier coating can be carried out, which can be single-sided, double-sided or multi-layer as required Or select coating methods such as vacuum aluminizing, physical or chemical deposition of silicon oxide, etc.