Testing Requirements(ASTM 4649) Stretch Wrap Films for Transport Packaging

Wrap film is also called stretch film that features light weight, flexibility and flimsy with excellent tensile resistance performances, expansion and self-adhesive performances. Its application in transport packaging is a way to improve packaging efficiency and to reduce costs.

BB/T0024-2004 Stretch Wrap Films for Transport Packaging refers to stretch wrap films for transport and indirect food contact with polyolefin plastics as main material. ASTM D 4649 further includes EVA, PVC, EMA and other special materials.

BB/T0024-2004 Stretch Wrap Films for Transport Packaging came into implementation on June 1, 2006. This standard adopts ASTM D4649 – 03(2009) Standard Guide for Selection and Use of Stretch Wrap Films. The technical requirements for wrap films in the standard have three parts: size and specification, appearances, and physical and mechanical properties.

1. Size and Specifications:

Thickness Testing refers to GB/T 6672 and ASTM D4649. Labthink PARAM CHY-C2 Thickness Tester and PARAM CHY-CA Thickness Tester (with high accuracy) are applicable.

Appearance refers to GB/T10457－1989, Visual measurement or magnifier is applicable.

Physical and Mechanical Properties

BB/T0024-2004 Stretch Wrap Films for Transport Packaging requires many indexes for physical and mechanical properties, including tensile force, adhesiveness, elastic recovery, permanent deformation, tensile maintenance, force value, puncture resistance, unit area quality deviation, transparency, fogging degree and water vapor permeation quantity, etc.

Tensile force and breaking elongation are also called stretching property, which is an important index for wrap film. Its testing method is GB/T 13022-1991 Plastics-Determination of Tensile Properties of Films. Choose the iv type (long strip) from I, ii, iii and iv types for testing with a width of 15mm. the clamp distance of the tensile tester is 50mm. The testing speed is 250mm／min±25mm／min. The above settings are in compliance with domestic practices, and achieve the convenient sample preparation. Besides, by using long strip, extensometer is not a must any more; and the shortcoming of breakage caused by its thin thickness and extensometer can be avoided. The recommended testing instrument is Labthink PARAM XLW series of Auto Tensile Testers, which has already been popular in packaging industry.

2.In order to determine whether wrap film is capable of protecting the goods free from wetting and moisture absorption during voyage or humid environment, the testing for water vapor transmission quantity is of vital importance. GB/T 1037-1988 Test Method for Water Vapor Transmission of Plastic Film and Sheet-Cup Method can be used for water vapor transmission quantity testing. Labthink PERME TSY-T Water Vapor Transmission Testers of weighing method are the proper testers for WVT testing.

3.Other Physical Indexes

3.1 Cling (peel): the adhesiveness of the two layers of wrap film under stretch or non-stretch state. ASTM D 5458 is applicable, and BLD-200S Auto Stripping Tester, FPT-F1 Friction/Peel Tester as well as other specialized instruments with even horizontal movement function.

3.2 Elastic Recovery: the ratio between the original size and the recovery size of the wrap film after a certain stretching period. The ratio is expressed in percentage. ASTM D 5459 is the method, and Labthink PARAM XLW series of Tensile Testers and BLD-200S Auto Stripping Tester are the applicable testers.

3.3 Permanent Deformation: the ratio of the wrap film stretching and the original length in percentage.

 Force at elongation, ASTM D 882 is applicable, and Labthink PARAM series of Auto Tensile Testers are proper testers.

3.4 Stress retention: after stretching the wrap film for a certain ratio, the tensile of keeping this state for a certain period of time vs. force at elongation is the stress retention, which is expressed in percentage. ASTM D 5459 and Labthink PARAM series of Auto Tensile Testers, PARAM BLD-200S Auto Stripping Testers are applicable.

3.5 Protrusion Puncture: is to express the puncture resistance of wrap films, and is expressed by the force when film breaking and the movement. Labthink PARAM series of Tensile Testers are applicable the test.

3.6 Clarity and Haze

Good clarity is necessary for wrap film in application. This test is only for the products less than 0.030mm thickness or transparent products. For clarity, ASTM D 1746 is applicable; for haze, ASTM D 1003 is applicable.

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