Stretch film is the most widely used in our lives and industrial production. It has good retraction memory and self-adhesiveness, which can tightly wrap the goods into a whole, and prevent flashover and collapse and dust pollution during transportation. The production of stretch film must comply with relevant international quality test standards.
what standards are used for stretch film testing when choosing stretch film?
1. Dimensions and appearance
Dimensions and specifications are the basic specifications of the user when ordering. This standard mainly refers to the ASTM D 4649 standard of the United States, and makes provisions for width deviation, thickness deviation, core length deviation, core inner diameter deviation, and film roll quality deviation items that are suitable for the actual situation in my country. These indicators are the same as or higher than the ASTM standard.
Appearance requirements are an important content in my country’s product standards. This standard specifies technical requirements for the quality of film breaks, bubbles, perforations, ruptures, lumps, fisheyes, and flatness. The evaluation method adopts the GB/T10457-1989 appearance item analysis method and has made certain modifications on its basis.
2. Physical and mechanical properties
BB/T0024-2004 “Stretch Wrap Film for Transport Packaging” mainly stipulates the physical and mechanical properties of tensile breaking force, elongation at break, viscosity, permanent deformation, elastic recovery, tensile retention, f-force value, puncture resistance, unit Technical indicators for area quality deviation, light transmittance, haze, and water vapor transmission.
1. Breaking force and elongation at break
Tensile force and elongation at break are also called tensile properties. Tensile performance is a very important index of stretch film. The test method adopts the test method standard of GB/T 13022-1991 “Plastic Film Tensile Performance Test Method”, and then From the standard type ⅰ, ⅱ, ⅲ and ⅳ four kinds of samples, finally choose ⅳ (long strip) test, the width is 15mm, the distance between the chuck of the tensile testing machine is 50mm, the gauge length is 50mm, The method of speed 250mm/min±25mm/min is used to test this item. This not only conforms to the customary usage of most domestic enterprises, but also achieves the purpose of convenient sample preparation. In addition, an extensometer is not necessary for the use of long specimens, which avoids the defect that the stretch film is very thin and the friction of the extensometer has a great influence on it, which can easily cause breakage. The testing instrument is recommended to use the XLW series intelligent electronic tensile testing machine produced by Labthink, which is widely used in the packaging industry.
2. Water vapor transmission rate
In order to characterize whether the stretch film can protect the product from moisture or moisture absorption in the sea or in an environment with high humidity, that is, the tightness after wrapping. The detection of water vapor transmission is very important. The detection method adopts the GB/T 1037-1988 water vapor transmission test method standard of plastic film and sheet to assess its water vapor transmission. The TSY-T series moisture permeability tester of the weighing principle produced by Labthink can be used for testing.
3. Other physical indicators
The viscosity, tension retention, permanent deformation, elastic recovery, and puncture resistance in the standard refer to the test method standards for stretch stretch film formulated by the American ASTM organization. The following briefly introduces the test items of viscosity, tension retention, permanent deformation, elastic recovery, and puncture resistance. Such detection indicators can be tested by XLW series intelligent electronic tensile testing machine or BLD-200S electronic peeling testing machine.
3.1 Adhesion: The adhesion between two layers of the stretch film in the stretched or unstretched state.
3.2 Elastic recovery: The stretch film will remain in this state for a certain period of time after being stretched for a certain proportion, and the ratio of the recovered size to the original size after release, expressed as a percentage.
3.3 Permanent deformation: The ratio of the increased length to the original length of the stretch film after a certain percentage is stretched, expressed as a percentage.
F force value: the maximum tensile force of the stretch film at a predetermined elongation.
3.4 Tensile retention: After the stretch film is stretched for a certain proportion, the ratio of the tensile force to the F-force value in the state for a certain period of time is the tension retention, which is expressed as a percentage.
3.5 Puncture resistance: used to indicate the ability of the stretch film to resist needle puncture. It is expressed by the force value when the membrane ruptures during the piercing process and the displacement when passing through.
3.6 Light transmittance, haze
Stretch film needs to have good transparency in use. The test method adopts GB/T 2410-1980 transparent plastic transmittance and haze test method. At present, most domestic production enterprises also use this standard for assessment. Note: The light transmittance and haze test are limited to products with a film thickness of 0.030mm or less and transparent and colorless.