GB/T 41792-2022Plastics - Film and sheeting - Determination of cold-crack temperature (English PDF)

1 Scope

This document describes a method for evaluating the brittleness of plastic films and sheeting at low temperature.

The cold-crack temperature is usually used to compare the low temperature performance of plastic film and sheeting, which is used a reference for evaluation in this document.

This document applies to the characterization of finished products of a given thickness and pattern, regardless of the composition of their raw materials. Data derived from this document may not be transferred without limitation to any other type of application or condition.

2 Normative references

The following documents are normatively referenced in this document and are indispensable for its application. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document.

ISO 291, Plastics - Standard atmospheres for conditioning and testing

Note: GB/T 2918-2018, Plastics - Standard atmospheres for conditioning and testing (ISO 291:2008, MOD)

ISO 4593, Plastics - Film and sheeting - Determination of thickness by mechanical scanning

Note: GB/T 6672-2001, Plastics film and sheeting - Determination of thickness by mechanical scanning (ISO 4593:1993, IDT)

3 Terms and definitions

The following terms and definitions are applicable to this document.

4 Principle

Place the test specimen bent into a ring in the cooling chamber to make it withstand the instantaneous folding caused by the impact of the free fall of the impact block.

Repeat the test at temperatures in steps of 5 °C, starting when no test specimens are ruptured or damaged, and ending when all test specimens are ruptured or damaged.

5 Equipment

Figure 1 is a schematic diagram of a typical test setup. Other devices of the same

physical principles can also be used. Figure 2 shows a schematic diagram of another applicable design scheme.

7 Conditioning of specimens

Bow the test specimens into a ring shape and install them on the specimen holder. If the specimen film or sheeting is printed or textured on one side, this side shall be on the outside of the ring.

The installed test specimens shall be conditioned for at least 3 hours in an environment specified in ISO 291.

8 Selection of impact block

Where the impact block is not pre-agreed, if an impact block of 200 g is sufficient to effectively fold the specimen, start the test with this impact block, otherwise, use an impact block of 500 g.

The following specification can be used to verify effective folding. Bend a paper strip (approximately 70 g/m2) of the same size as the test specimen into a ring and place it in the specimen ring. According to the steps in Chapter 9, use a 200 g impact block to test the plastic/paper composite specimen, and use a temperature slightly higher than the cold-crack temperature to prevent the specimen from cracking. Check the paper strip, a sharp crease at the top of the ring indicates an effective folding.

9 Procedures