Flexible packaging plays an important role in food packaging . With the increasing attention of the Chinese government to food safety, food terminal enterprises have higher and higher requirements for packaging quality, which makes flexible packaging enterprises have to systematically test soft packaging before leaving the factory. To ensure the yield rate and maintain the company's reputation. However, most of the domestic flexible packaging companies only cover the projects that the end customers care about, which is very unfavorable for the expansion of new customers. The author has been engaged in the quality inspection of plastic film and bag for packaging for many years. Now it is combined with GB/T 10004-2008 "Plastic composite film for packaging, bag dry compounding, extrusion compounding", from test considerations to key inspection project control. Systematic analysis provides a reference for flexible packaging companies to understand product performance and master product quality.
Test considerations
Preparation condition
Before the test sample is tested, some preparatory work is required. The two most important ones are the adjustment of the sample state and the setting of the test standard environment. The purpose of sample state adjustment is to ensure that all tested film samples are in a constant temperature and humidity environment to eliminate the influence of environmental factors on the measured data, and obtain reproducible and comparable test results. The ambient temperature and humidity and the length of time the film sample is placed in a constant environment have a great influence on the performance test results of flexible packaging products. For example, when the ambient temperature rises, it tends to cause certain mechanical properties of plastics, especially thermoplastics, such as tensile strength, modulus of elasticity, yield stress, and hardness.
The standard environment for the test is equivalent to the average environmental conditions of the laboratory. The plastic film is composed of a plurality of polymer groups with repeating links. After the molding is cooled, the macromolecular chain is temporarily frozen, and it takes a certain time for the molecular chain to be fully stretched, and the speed of stretching is closely related to the temperature and humidity of the environment. Therefore, the state of the sample should be adjusted under the standard environment of the test and tested in this state, so that the results of the test are comparable. The state of the sample and the test standard environment shall be adjusted and set according to the standard environment and normal deviation range specified in GB/T 2918-1998 "Standard Environment for Condition Adjustment and Test of Plastic Samples", that is, the temperature is (23 ± 2) °C. The relative humidity is (50 ± 10)%. It should be noted that the adjustment time cannot be less than 4h.
Sampling requirements
Sampling should be carried out from the test object in accordance with relevant technical standards and specifications. Sampling includes the collection (sampling) of the test subject and the preparation (preparation) of the test sample.
Sampling requires that the sample taken is representative and uniform. The detection of the sample is used to estimate and infer the characteristics of all samples. This is a cost-effective method commonly used in scientific experiments, quality tests, and social surveys.
Sample preparation refers to the processing of a sample into a standardized sample with uniform characteristics for test operation, according to the purpose of the test. The samples produced must also be representative to truly reflect certain characteristics of the material being analyzed.
Sampling is the primary condition for proper detection. The representativeness and uniformity of sampling reflect the quality of the batch product. The standardization of the sample preparation ensures the reproducibility of the test results and the comparability of the comparison test data. It is worth noting that the samples obtained during the sampling process should be intact and the number of samples must be sufficient to complete all the test items.
Basic inspection project
external assessment
The main purpose of appearance inspection is to identify the appearance defects of the sample. Generally, the artificial sensory recognition method is adopted. Therefore, the evaluation of the appearance quality of the product has certain subjectivity. In this process, the author suggests that the following points should be noted.
(1) The evaluation of the appearance quality must establish certain conditions. For example, the environmental conditions, assessment methods, and the visual acuity, touch, practical experience, and technical level of the assessor should be as similar as possible.
(2) Most of the appearance quality is assessed by the sensory test of the tester, so the evaluation term of the appearance quality must be clearly defined. For example, the use of terms such as “must†or “notâ€, “should†or “should notâ€, “available†or “not allowedâ€, “allowed†or “not to have†should be clearly defined to reduce the assessment. Subjectivity.
GB/T 10004-2008 specifies visual inspection under natural light, and measures with a measuring instrument with an accuracy of not less than 0.5mm. It mainly checks whether the surface of the sample has wrinkles, bubbles, scratches, perforations, adhesions, foreign matter, delamination, dirt, etc. .
Print quality inspection
The printed pattern of the package cannot be ignored for the promotion and display effect of the product. The use of laboratory density meter, spectrophotometer, such as testing equipment, flexible packaging and printing quality objective evaluation, if necessary, can be established as a physical reference standard samples of print quality, in order to detect personnel have a clear assessment basis.
Regarding the basis of printing quality, gravure printing products shall be tested according to the provisions of GB/T7707-2008 "Gravure Decorative Prints", and flexographic printing products shall be tested according to the provisions of GB/T 17497-2012 "Flexible Edition Decorative Prints". Bar code printing shall be tested according to the provisions of GB/T 18348-2008 "Inspection of printed bar code symbol quality", and other 1D bar codes shall be printed according to GB/T 14258-2003 "Information technology automatic identification and data acquisition technology bar code symbol printing". The inspection of the quality inspection is carried out.
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