ISO 16790:2021 Plastics — Determination of drawing characteristics of thermoplastics in the molten state

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Plastics — Determination of drawing characteristics of thermoplastics in the molten state是国际标准化组织(International Organization for Standardization，简称ISO)于2021-02-17发布的ISO标准，适用于全球范围。

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INTERNATIONAL STANDARD ISO 16790:2021

Plastics — Determination of drawing characteristics of thermoplastics in the molten state

1 Scope

This document specifies a method for determining the drawing and break characteristics of molten plastics. The method involves the measurement of the force generated in deforming a molten filament under defined extrusion temperature and drawing conditions.

Data is generated under non-isothermal and non-homogeneous deformation conditions. However, it is useful for the interpretation of polymer behaviour in extensional flow.

The method is suitable for thermoplastics moulding and extrusion materials that can be extruded using a capillary extrusion rheometer, or an extruder with capillary rod die or other extrusion devices and have sufficient melt strength to be handled without difficulty.

The method is applicable to chemically stable materials that produce a uniform extrudate free from heterogeneities, bubbles, unmelted impurities, etc.

This method can provide information on

— processability for all extrusion techniques,

— the effect of mechanical and thermal history, and

— the effect of chemical structure, such as branching, entanglements and molecular mass.

This technique is one of a number of techniques that can be used to measure the extensional flow behaviour of a material. This method of measurement does not necessarily reproduce the drawing conditions to which thermoplastics are subjected to during their processing.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 291, Plastics — Standard atmospheres for conditioning and testing

ISO 11443, Plastics — Determination of the fluidity of plastics using capillary and slit-die rheometers

3 Terms a nd definiti ons

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at http://www.electropedia.org/

3.1

drawing

process of stretching a filament of polymer melt that is being continuously formed by a capillary extrusion rheometer or extruder or other extrusion device

ISO 16790:2021

3.2

melt strength

F b

value of the melt tension at break of the extrudate

Note 1 to entry: Also known as the force to break.

Note 2 to entry: It is expressed in newtons.

3.3

draw ratio at break

DR

ratio of the drawing velocity (3.7) of the material at break to the mean velocity (3.4) of the material flowing from the die

3.4

mean velocity

v m

average velocity of the extrudate at the die exit, determined as the ratio of volume flow rate to die cross-sectional area

Note 1 to entry: It is expressed in metres per second.

3.5

initial diameter

D i

maximum diameter the extrudate attains after swelling on exiting from the die, the extrudate not yet having been subjected to significant drawing

Note 1 to entry: Initial diameter is expressed in metres.

Note 2 to entry: If no swelling of the extrudate occurs after exiting the die, the initial diameter is taken as the diameter of the die.

Note 3 to entry: This method can be unsuitable for testing materials that do not exhibit swelling of the extrudate after exiting the die as such materials will be difficult to handle in drawing off and will exhibit small drawing forces (3.8).

3.6

initial velocity

v i

velocity of the extrudate near the die exit after swelling, the extrudate not yet having been subjected to significant drawing (3.1)

Note 1 to entry: It is determined at the position of the initial diameter of the extrudate.

Note 2 to entry: It is expressed in metres per second.

3.7

drawing velocity

v t

velocity imposed on the lower end of the extrudate by the drawing unit

Note 1 to entry: It is expressed in metres per second.

3.8

drawing force

F t

force exerted on the extrudate by the drawing unit

Note 1 to entry: It is expressed in newtons.

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