Testing of flexible packaging also cannot be ignored

[China Packaging Network News] Flexible packaging in food packaging occupies an important position, with China's government's increasing emphasis on food safety, food terminal companies have higher and higher requirements for packaging quality, making flexible packaging companies have to be Conduct comprehensive system testing to ensure product yield and maintain corporate reputation. However, most of the domestic flexible packaging companies are only affiliated with end-customer-focused projects for testing, which is very detrimental to the expansion of new customers. The author has been engaged in the quality inspection of plastic films and bags for packaging for many years. It is now combined with GB/T 10004-2008 "Plastic Composite Films for Packaging, Bag Dry Compounding, and Extrusion Compounding", from the test considerations to the control of key test items. Systematic analysis will provide reference for flexible packaging companies to understand product performance and master product quality.

Test considerations

Preparation conditions

Prior to testing the sample, some preparation work must be done, of which two important ones are the adjustment of the sample state and the setting of the test standard environment. The purpose of the sample conditioning is to ensure that all the tested thin film samples are in a constant temperature and humidity environment to eliminate the influence of environmental factors on the measured data and to obtain reproducible and comparable test results. The temperature and humidity of the environment 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, elastic modulus, yield stress, and hardness to decrease.

The standard environment of the test corresponds to the average environmental conditions of the laboratory. The plastic film is composed of many polymer groups with repeating links. After the molding is cooled, the macromolecular chains are temporarily frozen. It takes a certain time to fully stretch the molecular chains, and the speed of stretching is closely related to the environment temperature and humidity. Therefore, the state of the sample should be adjusted in the standard environment of the test, and the test should be performed in this state, so that the results of the test are comparable. The state of the sample and the test standard environment are adjusted and set according to the standard environment and normal deviation range specified in GB/T 2918-1998 “Standard Environment for Conditioning and Testing of Plastic Specimens”, ie the temperature is (23±2)°C. The relative humidity is (50±10)%. It should be noted that the adjustment time can not be less than 4h.

Sampling requirements

Samples shall be taken from the test object in accordance with relevant technical standards and specifications. Sampling includes the acquisition of the test object (sampling) and the preparation of the test sample (sample preparation).

Sampling requires that the extracted sample be representative and uniform, and the characteristics of all samples should be estimated and inferred through the detection of this sample. This is a cost-effective method commonly used in scientific experiments, quality inspections, and social surveys.

Sample preparation refers to the process of processing the sample into standardized samples with uniform characteristics for test operation. The resulting sample must also be representative in order to truly reflect certain characteristics of the analyzed material.

Sampling is the primary condition for ensuring correct detection. The representativeness and uniformity of the sampling reflect the quality of the batch product. The standardization of sample preparation ensures the reproducibility of the test results and the comparability between the test data of each comparison. It is worth noting that the samples obtained during the sampling process should be intact and the sampling quantity must be sufficient to complete all test items.

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Basic test items

external assessment

The main purpose of appearance detection is to identify the appearance defect of the sample, and generally adopts an artificial sensory identification method. Therefore, the appearance quality evaluation of the product has a certain subjectivity. In this process, the author suggests that the following points should be noted.

(1) The assessment of appearance quality must establish certain conditions. For example, the environmental conditions, assessment methods, and assessment staff’s visual acuity, touch, practical experience, and technical level when assessing the appearance quality of flexible packaging should be as same as possible.

(2) The appearance quality is mostly assessed by the sensory test of the inspector. Therefore, it is necessary to clearly define the evaluation term of appearance quality. For example, terms such as “must” or “must not”, “should” or “should not”, “available” or “not allowed to use”, “allowed to have”, or “should not exist” should be clearly defined, thereby reducing the number of Subjectivity.

GB/T 10004-2008 provides visual inspection under natural light and measurement with a measuring tool with an accuracy of not less than 0.5 mm. The main observation is whether the surface of the sample has wrinkles, bubbles, scratches, perforations, adhesions, foreign matter, delamination, dirt, etc. .

Printing quality inspection

The printed printing pattern of the packaging can not be ignored for the promotion and display of the product. The laboratory uses densitometers, spectrophotometers and other test equipment to objectively evaluate the printing quality of flexible packaging. If necessary, standard samples can be established as a physical reference for the printing quality so that the testing personnel can have a clear assessment basis.

Regarding the standards of printing quality, gravure printing products should be tested in accordance with GB/T 7707-2008 "Intaglio Prints", and flexographic products should be tested in accordance with GB/T 17497-2012 "Flexible Printed Decorative Prints". Barcode printing should be tested in accordance with the provisions of GB/T 18348-2008 "Inspection of Barcode Symbol Printing Quality", and other 1D barcodes are printed according to GB/T 14258-2003 "Information Technology Automatic Identification and Data Collection Technology Barcode Symbols." "Quality Inspection" provisions of the test.