CS246238B1 - Plastic's specific volume dependence on pressure and temperature measuring device - Google Patents

Abstract

Apparatus for measuring the dependence of a specific volume of a plastics material on pressure and temperature comprises a heat-insulated pressure cell (2) and a program controlled straight line hydromotor 12 with an electrohydraulic servo valve (13) for application of a load, means (3,4,5,6) for adjustably heating or cooling said heat insulated pressure cell (2), and feed back means comprising a pick-up device (14) for measuring force and a pick-up device (15) for tracking the movement of the pressure piston. The electrohydraulic valve (13) is connected to a summary recorder (22), and the pick-up devices for tracking movement and for measuring force (14,15) are connectable in turn to an input of the summary recorder (22) via a change-over switch (23). A programmer (19) is also connected to the summary recorder (22) via a change-over switch (24), and an output of said summary recorder (22) is connected to the servo valve (13). The arrangement enables the measurement of specific volume change when test piece 1 is subjected to isothermal hydrostatic compression or isobaric heating and cooling. <IMAGE>

Description

(54) Equipment for measuring the specific volume of plastic on pressure and temperature

A device for measuring the dependence of specific volume of plastics on pressure and temperature, realizing measurement of dependence of specific volume of plastic on isothermal hydrostatic compression or isobaric cooling or heating. The device consists of a controlled heated or cooled thermally insulated pressure cell and a program controlled load device consisting of a linear hydraulic motor with an electrohydraulic servo valve, force sensor and displacement sensor in conjunction with the respective programmer.

The present invention relates to a device for measuring the dependence of the specific volume of plastic on pressure and temperature, i.e. the detection of so-called pvT diagrams. These diagrams give an idea of the material's response to isothermal hydrostatic compression or to isobaric cooling or heating. Both types of measurements are realized by one device.

The knowledge of the measured values of the given dependencies in particular plastics is used in practice especially in the design of plastic processing machines, to determine adiabatic heating of plastics and lately especially in the preparation of a set of input parameters for automatic regulation and control of the technological process of plastic injection.

Instruments for measuring the dependence of the specific volume of plastics on pressure and temperature are different concepts, the most commonly used are three basic types:

the first group consists of devices based on a pressure cell in the form of a pressing tool clamped on a table of a hydraulic press;

the second group comprises a device wherein the pressure cell is placed in a thermostat and the pressure on the test body is applied hydraulically; a modification of this system consists of a device in which the hydraulic fluid acts directly on the test body;

- the third group is represented by devices in which the test specimen of any shape is placed in a malleable container filled with mercury and immersed in a tempered pressure container filled with liquid.

None of the mentioned devices allows measurement of both types of dependence.

These drawbacks are overcome by an apparatus for measuring the specific volume of plastics on pressure and temperature, consisting of a thermally insulated pressure cell and a loading device.

SUMMARY OF THE INVENTION The heat-insulated and controlled-heated or cooled pressure cell comprises a pressure piston of a programmed load-bearing device comprising a linear hydraulic motor with an electrohydraulic servo valve and its feedbacks formed by a force sensor generated by the linear hydraulic motor on the pressure piston. pressure piston travel. The electrohydraulic servo valve is connected to a summation element, to which a force sensor and a travel sensor are connected via the measuring point switch, and a programmer is connected via the program switch. At the output of the summation element there is an electrohydraulic servo valve. .

The device for measuring the specific volume of plastics on pressure and temperature according to the invention enables fast, accurate and highly automated measurement and evaluation of the required dependencies. For example, in automatic computer control of the injection molding process, an injection mold is used in the mold cavity, which in turn results in a substantial increase in the quality of the parts so produced. The problem of perfectly filling the working space of the pressure cell with the material being evaluated, which is a precondition for the accuracy and reproducibility of the results, is solved by using a body of defined shape and size, which is inserted into the thermally insulated pressure cell.

The attached drawing shows a diagram of a device for measuring the specific volume of plastics on pressure and temperature, consisting of a thermally insulated pressure cell with temperature control, a loading device and a control unit with appropriate control circuits.

The test body 7 is located in the working space of a thermally insulated pressure cell 2, in the wall of which a cooling screw 6 is connected, connected via a temperature sensor 8 with a temperature control device 1 connected to a programmer 19 and a flowmeter 9; heater .3 connected via a temperature sensor 5 to a controller. The pressure piston 10 is tightly seated on the test body 2, in the front of which there is a temperature sensor 11 of the test body 2 located in the borehole. The pressure piston 10 is mechanically connected with a linear hydraulic motor 12 and to which the pressure piston 10 is simultaneously connected via the force feedback sensor 14 and the measuring point receiver 23, to which the travel sensor 15 is also connected.

Adder 22 is then via the switch 24 channels connected to a programmer 22 · ^to the bottom of pressure cell 2 P ° d specimen 2 engages the lower piston 16, ^whose head is a pressure sensor 22 · Pressure Cell 2 ^te provided with a sensor 18 of the temperature, located in a borehole in its wall. The test body temperature sensor 11, the force feedback sensor 14, the travel sensor 15, the pressure sensor 17 and the pressure cell temperature sensor 18 are connected to the evaluation unit 21 via the recording device 20;

The measurement of the specific volume of plastics on pressure and temperature is carried out as follows:

The test body 1 located in the working space of the pressure cell 2, which is heated by means of an electric heater 2 controlled by the electric heater regulator 4 via a heating temperature sensor 2 or cooled by a liquid or gas medium in a cooling screw 6, is loaded by a pressure piston 22 * ^at its face the sensor body temperature sensor 11 is located in the bore 2 ·

The temperature of the cooling medium in the worm 2 ^e j controlled tempering device 2 ^sensor 2 and the temperature of the tempering medium flowmeter ninth drive the piston is derived from the linear hydraulic motor 12 controlled by means of the electrohydraulic servovalve 13 and a feedback sensor 14 of linear hydraulic motor force applied to the pressure piston 12 or 10 by using a travel sensor 15 for measuring the movement or deformation of the piston rod.

Ejection of the test specimen 2 ^{2 of the} working space and its cleaning is performed by the movable lower piston 22 * ^, which is headed by a pressure sensor 22 · Measurement of the pressure cell temperature -2 is carried out by the pressure cell temperature sensor 18. the temperature, force or path values are recorded by the recording device 20 and evaluated in the evaluation unit 21.

The summation member 22 serves to compare the actual force or displacement values detected by the force sensor 14 or the displacement sensor 15 with the values set in the programmer 22. The programmer 22 determines whether the actual force or deflection value γ is recorded via the switch 23. On the other hand, the program switch 24 determines whether the specific volume versus temperature at constant pressure or the specific volume versus pressure at constant temperature will be detected.

The device works either at isothermal hydrostatic compression, ie at T = const, when the test body 2 is loaded with constant deformation у = const. ^In this case, the pressure piston travel path sensor 15 gives a signal to the programmer 19 and the summation member 22 whose value corresponds to the actual deformation Υ _{χ of the} test body and where this signal is compared to the value у - const. and optionally commanding to change Ду, thereby equalizing the desired and actual value of the motion of the pressure piston 10.

In order to capture the real test run, the actual deformation value is continuously recorded. Similarly, the test is performed in isobaric cooling or heating, i.e., in const. pressure p = const, when the test body 2 is loaded with a constant force F = const. The force F is set on the programmer 19 and is compared in the summation 22 with the actual force F detected by the force sensor 14. The principle is based on the fact that when changing the length of the specimen 2 ^{as a} result of its controlled cooling or heating const is changed to F ^ and after processing in the summation member 22 a signal of F value is given to change the setting of the piston of the linear hydraulic motor 22. Both described processes are repeated for given levels F = const and у = const.

To maintain a constant temperature of the test body 2 during long-term heating, the electric heater 3, which is controlled by the controller 4 · ^{2 of the} programmer 19, is guided by the set temperature Tg const d ° of the regulator 4 which controls the electric heater. The heater temperature sensor records the actual temperature ΤΕχ, which is compared to the Tg constant in regulator £, ^and this compares the power change Pw. At the same time, the temperature cell Τχ of the pressure cell 2 is recorded ^from the pressure cell temperature sensor 18.

For direct cooling or heating of the test body £ is used liquid or gaseous medium is tempered in a tempering unit 2 to the desired temperature T _K const isothermal compression, or a desired temperature gradient during compression isobaric · Tempering medium at temperature T _K ^{const, and the} flow Qkonst passes temperature cell _R 2 at the outlet of the cell, its temperature T _{Rx is} determined by means of sensor J3 temperature of the tempering medium.

Throughout the measurement, both isothermal and isobaric conditions, the readings from the test probe temperature sensor 11 and the pressure transducer 17 are recorded and stored, i.e. the temperature T _s indicated by the test probe temperature sensor 11 represents the closest inclination. to the real temperature of the test body 6 as well as the force F _g or the pressure p _s from the pressure sensor 17, which also serve as control values for the value given by the force sensor 14.

The following description is used in the activity description:

y = const - constant deformation of the specimen y - actual deformation of the specimen

J x & y - difference between у = const and y ^

F3 - actual force applied to the specimen

AF - difference between F = const and F _x ^T E const ”set temperature of the electric heater

_{^ Ε} χ - actual temperature near electric heater p ^ - electric heater input ^T K const “set temperature for heating or cooling, event. set temperature gradient T _K x - temperature of the tempering medium at the cell outlet

Τχ - the actual 3 temperature of the cell and specimen

Qconst ~ the flow rate of the tempering medium

Ts - actual test specimen temperature

Fs - actual test force applied to the test specimen

Ps - actual pressure in the specimen

The entire measurement procedure on the described apparatus, including sample preparation, is described in more detail in the following examples.

Example 1

Determination of dependence of specific volume of plastic on pressure and temperature under isothermal conditions.

Measurements were performed with a heat insulated pressure throughout the following parameters: r ^y Chlost heating ^{0, 12} 5 ° C / s, max. Temperature scatter ^y pr ^ur cut cel ^y · ^0.4 ° ^C

The specimen of ^{the poly-1} et ^y ene Liten MB 62 was machining work of the ejection section of 12 mm, inserted into the pressure cell under a pressure of 0.1 MPa, and cooled melted down onto the POCA ^{No 19} ° C.

Dimensions of test specimen: - diameter 8 mm,

- length 45 mm,

- volume 2261,97 mm

Test condition ^{y Sky -} r ^y c ^{h Photogene, white} lost for o ^{ck 0,} 5 mm. min ¹

- Temperature control electronic temperature controller, 100% power, feedback 1.2 s, the number of divisions deducted 3 ^{- i} from ^t erm ^{i s} measuring CK-measurement. ^{MPLEMENTATION} at 19, ^{50, 10} °, ¹⁵ °, ²⁰⁰ ° C

- endurance at temperature prior to measurement after running from below 60 min.

The test parameters were recorded: F _x , y _x , _{χ χ} , T _s , p> p, Τ _Εχ , time. From these parameters these specific volume dependencies were found - see Table 1.

Example 2

Determination of values of specific volume of plastic on pressure and temperature under isobaric conditions.

Measurements were performed with a heat insulated pressure throughout the following parameters: r ^y s ^l ost DC ^hl Azov ^{ck p} ro the te ^p e ^l Nou ^and isolation of the ^I and ^P r ^Ut of ^the c ^{hl di} C water ⁰ 0 ² ° C / sec.

The test specimen as in Example 1 was produced in the same manner.

When ^d m ^{d y} nk test ^Sky - Hzen ^é ^ oc ^ Azov with graphite ^di Ente ^0.02 ° ^{C /} s

- isobaric measurements at 0.1, 20, 40, 60, 100 and 160 MPa

- run from below to the initial test temperature, hold at this temperature for 60 min.

The test parameters were recorded: Noven Specific Volume - see Table 2. ^F x ' ^y x' ^p s ' ^Τ χ' Table 1 —S ^J Trx ' ^Q const * ^From results by! sta- Te ^pl ota ( ^O C) Pressure (MPa) Change specific volume ~ -L ° c (%) ^V 19 19 Dec 20 May 0.446 19 Dec 60 1, 198 19 Dec 100 ALIGN! 2,099 19 Dec 150 3,132 19 Dec 200 4,000 50 20 May 0.528 50 60 1,462 50 100 ALIGN! 2,442 50 150 3,630 50 200 4,455 100 ALIGN! 20 May 0.594 100 ALIGN! 60 1,584 . 100 ALIGN! 100 ALIGN! 2,772 100 ALIGN! 150 4,000 100 ALIGN! 200 4,884 150 20 May 0,660 150 60 2,000 150 100 ALIGN! 3,135

246238. 6 Continuation tables Temperature (° C) Pressure (MPa) Change in specific volume -A ^V - ^V 19 ° C 150 150 4,785 150 200 6,402 200 20 May 0.792 200 60 2,192 200 100 ALIGN! 4,125 200 150 6,336 200 200 • 8,118

Table 2 Pressure (MPa) ' Te ^pl ota (° C) ^b specific of diarrhea (cm ³ g H 0.1 30 1,05266 0.1 60 1,06942 0.1 90 1,10176 0.1 110 1.13804 0.1 130 1.26345 0.1 150 1.28080 0,1 ‘ 180 ¹ 1.30470 0.1 200 1.32123 20 May 30 1,04589 20 May 60 1,06110 20 May 90 1,08628 20 May 110 1,11825 20 May 130 1,24023 20 May 150 1,25499 20 May 180 1.27677 20 May 200 1.29108 40 30 1,03842 40 60 1,05210 40 90 1,07297 40 110 1,09933 40 130 1.15989 40 150 1,23264 40 180 1,25221 40 200 1.26605 60 30 1.03208 60 60 1,04542 60 90 1,06311 60 110 1.08558 60 130 1,13232 60 150 1,21417 60 180 1,23331 60 · 200 1.24638 100 ALIGN! 30 1,02007 100 ALIGN! 60 1,03085 ‘100 90 1.04682

Table continuation

Pressure (MPa) (° C) - 'u, 3 - lv specific volume (cm g) 100 ALIGN! 110 1.06153 100 ALIGN! 130 1,09097 100 ALIGN! 150 1.18284 100 ALIGN! 180 1,20069 100 ALIGN! 200 1,21290 160 30 1,00601 160 60 1,01544 160 90 1.02865 160 110 1.04013 160 ’ 130 1,05575 160 150 1.08785 160 180 1,16731  160 · ·. . 200 1, 17780

Claims (1)

SUBJECT Y N LEZU Apparatus for measuring the specific volume of plastic to pressure and temperature, consisting of a thermally insulated pressure cell and a loading device, characterized in that a pressure piston (10) of a programmed load loading device extends into the working space of a controlled heated or cooled pressure cell (2). comprising a linear hydraulic motor (12) with an electrohydraulic servo valve (13) and its feedback. (10), wherein the electrohydraulic servo valve (13) is coupled to a summation member (22) to which an input force sensor (14) and a travel sensor (15) and a switch (24) are connected via a brewing switch (23). ) of the programmer (19), and whose output is an electrohydraulic servo valve (13).