BS-ISO-16790-2005.pdf

BRITISH STANDARD BS ISO 16790:2005 Plastics Determination of drawing characteristics of thermoplastics in? the molten state ICS 83.080.20 ? Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 16790:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 5 December 2005 © BSI 5 December 2005 ISBN 0 580 46378 8 National foreword This British Standard reproduces verbatim ISO 16790:2005 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee PRI/21, Testing of plastics, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 18, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference number ISO 16790:2005(E) INTERNATIONAL STANDARD ISO 16790 First edition 2005-06-15 Plastics Determination of drawing characteristics of thermoplastics in the molten state Plastiques Détermination des caractéristiques d'étirage des thermoplastiques à l'état fondu BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 16790:2005 iii Contents Page Foreword iv 1Scope . 1 2Normative references . 1 3Terms and definitions. 1 4Principle . 3 5Apparatus 3 6Calibration . 7 7Sampling 8 8Procedure 8 9Calculation and expression of results 13 10Precision 15 11Test report . 15 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 16790:2005 iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 16790 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical- chemical properties. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 1 Plastics Determination of drawing characteristics of thermoplastics in the molten state 1 Scope This International Standard 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. Such materials should be chemically stable and produce a uniform extrudate free from heterogeneities, bubbles, unmelted impurities, etc. This method may provide information on: ? processability for all extrusion techniques; ? the effect of mechanical and thermal history; ? 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 referenced documents are indispensable for the application 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 1133, Plastics Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics ISO 11443, Plastics Determination of the fluidity of plastics using capillary and slit-die rheometers 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 2 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 3.2 melt strength Fb value of the melt tension at break of the extrudate. NOTE 1 Also known as the force to break. NOTE 2 It is expressed in newtons. 3.3 draw ratio at break DR ratio of the drawing velocity of the material at break to the mean velocity of the material flowing from the die 3.4 mean velocity vm average velocity of the extrudate at the die exit, determined as the ratio of volume flow rate to die cross- sectional area NOTE It is expressed in metres per second. 3.5 initial diameter Di initial diameter of the extrudate after swelling on exiting from the die, the extrudate not yet having been subjected to significant drawing NOTE 1 It is the maximum diameter the extrudate attains. NOTE 2 It is expressed in metres. NOTE 3 If no swelling of the extrudate occurs after exiting the die, the initial diameter is taken as the diameter of the die. NOTE 4 This method may not be suitable 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. 3.6 initial velocity vi velocity of the extrudate near the die exit after swelling, the extrudate not yet having been subjected to significant drawing NOTE 1 It is determined at the position of the initial diameter of the extrudate. NOTE 2 It is expressed in metres per second. 3.7 drawing velocity vt velocity imposed on the lower end of the extrudate by the drawing unit NOTE It is expressed in metres per second. BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 3 3.8 drawing force Ft force exerted on the extrudate by the drawing unit NOTE It is expressed in newtons. 3.9 drawing length le distance between the die exit and the point where the extrudate first contacts the drawing units rotating wheels NOTE It is expressed in metres. 3.10 drawing acceleration a rate of increase in the drawing velocity NOTE It is expressed in metres per square second (m/s2). 3.11 drawing velocity at break vb velocity recorded at break when a constant drawing acceleration is used NOTE It is expressed in metres per second. 4 Principle Molten polymer is extruded from a capillary rheometer, extruder or other extrusion device at a specified temperature. The extrudate is drawn from the die by take-off wheels. Two techniques are used: a) A series of take-off wheel velocities is used to determine the drawing force as a function of the drawing velocity. b) A constant rate of acceleration of the take-off wheels is used to determine the melt strength (force to break) of the extrudate. 5 Apparatus 5.1 Apparatus for heating the polymer and forming the extrudate 5.1.1 General The device to supply the molten polymer at a controlled temperature and flow rate shall consist of a heatable barrel either a capillary extrusion rheometer (5.1.2) or an extruder (5.1.3), the bore of which is closed at the bottom end by a die (see Figure 1). The test pressure shall be exerted on the melt contained in the barrel by a piston, a screw or pressurized gas. 5.1.2 Capillary extrusion rheometer If a capillary extrusion rheometer is used, it shall have capillary dies, a piston, a temperature-measuring device and a pressure-measuring device meeting the requirements of ISO 11443, unless otherwise stated in this International Standard. BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 Key 1 rheometer or extruder 2 melt (temperature T) 3 capillary (diameter D, length l) 4 axis 5 extrudate/roller contact 6 drawing bench 7 drive rollers (radius r) 8 data acquisition: rotational speed n drawing force Ft le drawing length vi initial velocity vt drawing velocity (= 2?rn) Figure 1 Drawing unit Direct drawing by two take-off rollers BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 5 5.1.3 Extruder 5.1.3.1 General If an extruder is used, it shall be a small extruder with a screw diameter of 25 mm or less. This unit shall be equipped with a rod die and temperature-measuring device. 5.1.3.2 Melt pump If available, a melt pump may be used to provide a uniform flow of material from the extruder to the die. If a melt pump is used, an extruder with a screw diameter larger than 25 mm may be used. 5.1.3.3 Dies The die, of known dimensions, shall be angled vertically downwards to allow gravity to act on the extrudate. For determining the apparent shear rate ap ? and the apparent shear stress ?ap with one capillary die, in accordance with ISO 11443, the ratio l/D of the length l to the diameter D of the die shall be at least 16 to 1 and its inlet angle shall be 180° 5.1.3.4 Temperature-measuring device To measure the temperature of the molten polymer (see 6.2), thermocouples or platinum resistance sensors are preferred, but thermometers may be used. 5.2 Apparatus for drawing the polymer extrudate 5.2.1 Drawing unit 5.2.1.1 The drawing unit shall draw the extrudate over a specified length (the drawing length) at a controlled drawing velocity and measure the resulting drawing force. 5.2.1.2 The drawing unit shall have take-off wheels to draw the extrudate. 5.2.1.3 The drawing unit shall have controllers for the speed and acceleration of the take-off wheels. 5.2.1.4 The drawing unit shall have a force sensor to measure the drawing force exerted on the extrudate. 5.2.2 Drawing unit design Drawing may be carried out directly under the die using two rollers to take off the extrudate without excessive slippage or pinching (see Figure 1). Alternatively, it may be carried out, after the extrudate passes around the groove of one or more free-return pulley(s), by a set of two rollers that pinch and take off the extrudate without excessive slippage (Figure 2 shows a possible design: other designs are applicable). Drawing can also be done by winding up the extrudate onto a single wheel. In all cases, the axis of the extrudate in contact with the rollers (see Figure 1), the first return pulley (see Figure 2) or the take-off wheel shall coincide with the capillary die axis. Where the extrudate passes over a return roller, drawing is considered to occur only in the section between the die exit and the initial point of contact between the extrudate and the pulley groove. In this case, the speed and drawing force of the first return pulley should preferably be measured. NOTE The return pulley may be cooled in order to prevent any sticking of the molten polymer. The same precaution may be taken for the drawing rollers. In both cases, it is important to ensure that these devices do not have a significant influence on the measurement of the drawing force due to frictional or inertial effects or on the drawing velocity and drawing acceleration due to slippage and pinching. BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 6 Key 1 rheometer or extruder 2 melt (temperature T) 3 capillary (diameter D, length l) 4 axis 5 driven, pinched extrudate 6 drive rollers (radius r) 7 return pulleys (free axis of rotation) 8 extrudate contact 9 data acquisition 10 force transducer le drawing length vi initial velocity vt drawing velocity (= 2?rn) Figure 2 Drawing unit Typical “take-off after return pulley” design BS ISO 16790:2005 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 08:14:58 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 7 5.3 Data-acquisition system The data-acquisition system shall be capable of continuously monitoring the drawing force, the drawing velocity, the temperature of the molten material, and the pressure of the melt at the entrance to the die throughout the test. 6 Calibration 6.1 General The extruder or the rheometer shall be calibrated with respect to the measured variables and parameters, such as temperature, pressure, volume flow rates and capillary dimensions, in compliance with the procedures described in ISO 11443, unless stated otherwise in th