GB/T 12027-2004 in English

《GB/T 12027-2004塑料 薄膜和薄片 加热尺寸变化率试验方法》由TC48（全国塑料制品标准化技术委员会）归口，主管部门为中国轻工业联合会。
本标准规定了塑料薄膜和薄片加热时纵向和横向尺寸变化测定的试验方法。本方法适用于厚度小于1mm的热收缩或非热收缩的塑料薄片尺寸变化的测定。

Plastics - film and sheeting - Determination of dimensional change on heating

1 Scope

This standard specifies a method of determining the dimensional change, in the longitudinal and transverse directions, of plastic films and sheeting on heating. This method may be applied to plastic sheets, whether qualified as thermoshrinking or not, up to 1 mm thick.

2 Normative references

The following standard contains provisions which, through reference in this text, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding correction), or revisions, of any of these publications do not apply to this standard. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. For undated references, the latest edition applies.

GB/T 2918-1998 Plastics - Standard atmospheres for conditioning and testing (ISO 291:1997)

3 Principle

The test consists of

a) measuring the initial lengths of two gauge lengths marked on each specimen in the longitudinal and in the transverse direction;

b) heating the specimens for a specified time at a specified temperature on a kaolin bed in an oven;

c) measuring the longitudinal and transverse gauge lengths again after cooling, and subsequently calculating the changes in the gauge lengths.

4 Apparatus

4.1 Circulating-air oven, of such a size that the total volume of the test assemblies (kaolin beds plus test specimens) does not exceed 10% of the free space in the oven. Provision shall be made for placing the test assemblies on shelves so that they are not less than 50 mm from each other and from the sides of the oven.

Foreword i
1 Scope
2 Normative references
3 Principle
4 Apparatus
5 Test specimens
6 Procedure
7 Expression of results
8 Precision
9 Test report
Annex A (Informative) Examples of temperature and heating time