Source：Link Testing Instruments Co.,Ltd
BOPP film has become an ideal cigarette packaging material because of its high brightness, good gloss, high stiffness, high moisture resistance and aroma retention. The shrinkage of BOPP film directly affects the smooth and beautiful appearance of cigarettes. Common cigarette packs are mainly divided into two types, one is a soft cigarette case, and the other is a hard cigarette case. For the former, it is generally required that the cigarette film used for packaging has a low shrinkage rate and a small contraction force to prevent excessive shrinkage. The cigarette pack is deformed, and even the cigarettes are squeezed and deformed. For the latter, the shrinkage rate and contraction force of the cigarette film are required to be relatively large, so as to maintain the smooth, uniform and compact packaging effect of the cigarette for a long time. Therefore, strengthening the detection of the shrinkage performance of the cigarette film to ensure the suitability and uniformity of the shrinkage performance has far-reaching significance for improving the appearance and quality of cigarettes.
Testing methods and test equipment
At present, there is no national standard related to BOPP cigarette film in China. The standard for this type of film is the local standard DB53/T 20-2008 "Biaxially oriented polypropylene film for cigarettes". There are two main methods for testing shrink film shrinkage: oil bath method and oven method. For example, the method specified in GB/T 10003 is the oven method, and GB/T 13519 specifies the oil bath method.This article we use the oil bath method to testing the shrinkage of the samples.
Test principle: After the shrink film is heated to the shrinking temperature, the film shrinks, the size changes, and a certain force value is generated at the same time. This equipment heats the test sample through the oil field, and then the sample under the set time Go out, test the change in its shrinkage size, and determine the shrinkage rate.
Test sample and test process
Test sample: BOPP film used in a certain brand of cigarettes.
1.Sample preparation: Use a sampler to cut 6 samples with a width of 15.0 mm and a length of more than 100 mm along the longitudinal direction of the BOPP smoke film sample, and perforate the samples with a special sampler.
2.Divide those specimens into three groups, one from machine direction and one from transverse direction for each group. For each group, one is used for shrinking force and contracting force tests, the other one is used for shrinkage ratio test.
3.Set test temperature, end temperature and other test parameters. Click Start Test to heat the oil.
4.After the temperature reach the setting value. Clamp one group of specimens in the sample grip net. Then put the specimens into the oil bath.
5.Repeat the operations of step 3 and 4 until all the specimen tests are finished.
The BOPP cigarette box film sample tested in this paper has a longitudinal shrinkage rate of 8.34%; a transverse shrinkage rate of 15.07%,
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