DE102017221602A1 - Method and device for characterizing a deformation part made of an entropy-elastic material - Google Patents

Abstract

The present invention relates to a method and a device (110) for characterizing a deformation part (112) made of an entropy-elastic material during and / or after production of the deformation part (112) in a forming process. The method has the following steps:
a) providing at least one tool (114) adapted for the forming process, wherein the tool (114) has at least one cavity (116) for receiving an entropy-elastic material, and wherein in the tool (114) further comprises a test device (140) for providing and is integrated for the detection of ultrasound, being provided by the tester (140) guided ultrasonic waves;
b) introducing a material under pressure into the cavity (116) and maintaining the pressure and a temperature for a period of time such that the forming part (112) comprising the entropy-elastic material is produced; and
c) applying ultrasound to the cavity (116) during the period and / or after the period of time provided by the testing device (140) and detecting the reflected ultrasound by means of the testing device (140), whereby the characterization of the forming part (112 ) he follows.
The method and the device (110) enable a simple in-situ determination of properties and / or dimensions of entropy-elastic materials, in particular of formed parts (112) made of elastomers or heated entropy-elastic thermoplastics, during and / or after production of the forming part (112). in a forming process.

Description

The present invention relates to a method and a device for characterizing a deformation part of an entropy-elastic material. The characterization here preferably serves to determine the properties and / or dimensions of entropy-elastic materials, in particular components made of elastomers or heated, entropy-elastic thermoplastics, during and / or after production of the formed part in a forming process.

State of the art

Entropy elasticity or rubber elasticity refers to a resistance of rubber-like materials to their deformation. The resistance is based in particular on a reversible entropy change in the partially crosslinked materials, which are referred to as elastomers, as a result of an imposed deformation. According to the theory of rubber elasticity, in the deformation of elastomers, the angles between the molecules are changed frictionless at crosslinking points, whereby the material can assume a state of less disorder as a result of the deformation, thereby reducing the entropy. If, subsequently, the force leading to the deformation is removed, an energy intake from the environment, in particular a supply of heat, can cause the molecules to twist again and assume a state of higher entropy.

The observable deformation behavior is characteristic of elastomers or partially cross-linked plastics. In addition, the entropy elasticity can be observed even with heated thermoplastics. In the case of heated thermoplastics, crosslinking points can be formed by temporary entanglements and entanglements of long-chain molecules. The number of crosslinking points determines the deformation behavior of both elastomers and non-crosslinked, heated thermoplastics, which may be in amorphous or partially crystalline form.

Devices and methods for determining a degree of crosslinking of elastomers are already known from the prior art. The determination of the degree of crosslinking in elastomers is frequently used here for monitoring a curing of elastomers during an injection molding process, which is also referred to as "monitoring". In this type of process, a plastic, in particular a thermoplastic, a thermoset or an elastomer, is heated to a molten state and then introduced in the molten state under application of pressure into a cavity of a tool. From a plastic melt in the cavity of the tool, which is held at least partially at high pressure and temperature, there is a formation of a Umformteils, which can be finally removed by demolding from the cavity of the tool. The injection molding process can be used to produce both simple and complex three-dimensional formed parts.

The formation of the Umformteils from the plastic melt takes place here by a crosslinking reaction. The crosslinking reaction takes place with the choice of certain parameters, in particular of the pressure and temperature of the plastic melt, with a linkage of the macromolecules in the formed part generally increasing steadily. As a result of the crosslinking reaction results in a change in the chemical, physical and / or mechanical properties of the plastic, in particular an increase in hardness, toughness and melting point of the plastic while reducing its solubility. A measure of the degree of crosslinking is generally given as a measure of the change, the "degree of crosslinking" being defined by a proportion of crosslinked sites with respect to a total amount of the plastic.

In order to produce formed parts which have the desired properties, it is necessary to set and maintain the parameters, in particular pressure and temperature, during the injection molding process in such a way that the degree of crosslinking in the elastomer can be achieved by the course of the crosslinking reaction. If the crosslinking reaction in the plastic is interrupted too early, the elastomer generally does not undergo complete vulcanization, so that regions with unfavorable properties can occur in the shaped part, which may affect the function and / or life of the formed part. On the other hand, if the crosslinking reaction in the plastic exceeds the necessary degree of vulcanization, a degradation process may occur due to the high temperatures prevailing during the crosslinking reaction, as a result of which the well-vulcanized formed part can already be decomposed again.

For the production of the formed parts with the desired properties, it is therefore necessary to set a period within which the selected parameters, in particular pressure and temperature, on the formed part to be formed as optimally as possible within a time window. In practice, empirical empirical values are generally used for this purpose. Due to the high level of empirical knowledge, automation or process control is difficult to carry out. Alternatively, samples can be taken and to determine the degree of crosslinking by means of chemical analysis methods such as sol-gel analysis. Such a determination of the degree of crosslinking is therefore often made only after the end of the manufacturing process and is particularly disadvantageous in complex and valuable formed parts. In addition, the determination of the degree of crosslinking by means of known physical analysis methods, such as one in the DE 10 2007 0156 67A1 described exposure to laser light, consuming and requires the presence of crystalline and amorphous structural components in the sample.

Heated thermoplastics, regardless of whether they are in an amorphous or semi-crystalline state, exhibit similar deformation behavior as elastomers in a temperature range below the thermoplastic state. Good stretching behavior in the entropy-elastic state region forms the basis of various forming processes in plastics processing. Typical forming processes here are thermoforming, extrusion blow molding or injection stretch blow molding, in which first a plastic is heated to the entropy-elastic temperature range and then treated by means of pressure differences, which can be generated in particular by means of compressed air and / or a vacuum, and / or by means of stretching aids. The heating can in this case by means of heaters, in particular by means of at least one contact, convection and / or radiant heating, or by means of an in-line extrusion, in particular during the extrusion blow molding or inline thermoforming, take place.

The impression of a component can here predominantly, but not exclusively, via a one-sided tool contact. The one-sided tool contact causes low machine costs, but also ensures that the components can be impressed on the tool side only a dimensionally accurate contour. A wall thickness distribution is dependent on a large number of influences, in particular tool geometry, friction, temperature and / or semifinished properties, and thus represents an important parameter for characterizing the thermoforming process. Furthermore, the wall thickness distribution allows further properties of the thermoformed parts, in particular with regard to rigidity, Barrier properties and / or component optics determine.

According to the known state of the art, a characterization of the wall thickness distribution in such components can only take place offline by means of tactile test methods.

Object of the invention

The object of the present invention is therefore to at least partially overcome the disadvantages and limitations known from the prior art in a characterization of a deformation part from an entropy-elastic material during and / or after a production of the deformation part in a forming process. In particular, a method and a device for characterizing a deformation of an entropy-elastic material are proposed, which allow a simple in-situ characterization of the Umformteils during and / or after production of the Umformteils in a forming process.

In addition, the proposed method and apparatus should also be suitable for characterizing the material properties of heated thermoplastics having a deformation behavior similar to partially crosslinked elastomers in an entropy-elastic state. In the case of known material properties of the heated thermoplastics, the method and the device should also be applicable to the determination of wall thicknesses in components made of heated thermoplastics.

Disclosure of the invention

This object is achieved by a method and a device for characterizing a deformation part of an entropy-elastic material during and / or after production of the deformation part in a forming process with the features of the independent claims. Advantageous embodiments can be found in the dependent claims.

In a first aspect, the present invention relates to a method for characterizing a deformation part of an entropy-elastic material during and / or after a production of the deformation part in a forming process. The term "forming part" is understood to mean a three-dimensionally extended structure to be examined, which is produced from a suitable material in the forming process, wherein the forming part has a shape which is determined by the shape of a cavity in a tool adapted for the forming process , In this case, the formed part produced may have a material which has been structurally modified during the production of the forming part in such a way that it could take the form of a cavity. For this purpose, the forming part can be made from elastomers or in another forming process, in particular by injection molding, preferably by thermoforming, injection stretch blow molding or extrusion blow molding made of a thermoplastic. However, the present method can also be used for other types of materials and investigations. The forming part can be, for example, samples or workpieces for a laboratory or products or prototypes, for example parts of a motor vehicle whose production is subjected to online monitoring using the present method.

In a particularly preferred embodiment, the present method is suitable for the investigation of entropy-elastic thermoplastics, in particular for the determination of material properties or, in the case of known material properties, for on-line monitoring of wall thickness distributions in a forming tool for producing the entropy-elastic thermoplastics. Here, the term "entropy-elastic thermoplastics" refers to heated thermoplastics, regardless of whether they are in an amorphous or in a partially crystalline state before heating, but have a similar deformation behavior as elastomers in a temperature range below the thermoplastic state. Such conditions can be produced by means of a forming process used in plastics processing, in particular thermoforming, injection stretch blow molding or extrusion blow molding.

In a further embodiment, which is also particularly preferred, the forming part is produced from an elastomeric melt introduced into the cavity in a mold for an injection molding process specially designed for the production of the forming part. The term "elastomer" here denotes dimensionally stable, elastically deformable plastics which have a glass transition point which is below their use temperature. The term "glass transition point" refers to a temperature above which the elastomer passes from a solid state into a rubbery melt. The elastomer can thus deform elastically under tensile and compressive load, but go back to its original, undeformed shape at discharge. The elastomers include in particular vulcanizates of natural rubber, silicone rubber or thermoplastic elastomers, e.g. thermoplastic copolymers or polymer blends. Elastomers are commonly used in rubber bands, gaskets or tires.

As described above, the formation of the formed part takes place from the melt by means of a crosslinking reaction. The term "crosslinking reaction" here denotes a chemical reaction in which a combination of a plurality of macromolecules of the plastic takes place in a three-dimensional network, wherein the linkage in the construction of the macromolecules and / or to existing macromolecules can use. The crosslinking reaction takes place with the choice of certain parameters, in particular of pressure and temperature in the plastic melt, with the linkage of the macromolecules generally increasing steadily as the crosslinking reaction progresses. As a result of the crosslinking reaction results in a change in the chemical, physical and / or mechanical properties of the plastic, which are also referred to as "material parameters", in particular an increase in hardness, toughness and melting point of the plastic while reducing its solubility. As a measure of the change in the elastomer during the curing of the Umformteils is generally given a value for a degree of crosslinking, wherein the "degree of crosslinking" is defined by a proportion of crosslinked sites in relation to a total amount of the plastic. In the context of the present invention, the term "determination" of the degree of crosslinking designates a determination of at least one specific value, which is correlated with the degree of crosslinking.

1. a) Bereitstellen mindestens eines für das Umformverfahren eingerichteten Werkzeugs, wobei das Werkzeug mindestens eine Kavität zur Aufnahme eines entropieelastischen Werkstoffs aufweist, und wobei in das Werkzeug ferner eine Prüfeinrichtung zur Bereitstellung und zum Nachweis von Ultraschall integriert wird, wobei durch die Prüfeinrichtung geführte Ultraschall-Wellen bereitgestellt werden;
2. b) Einbringen eines Werkstoffs unter Druck in die Kavität und Aufrechterhaltung des Drucks und einer Temperatur über einen Zeitraum derart, dass das den entropieelastischen Werkstoff umfassende Umformteil hergestellt wird; und
3. c) Beaufschlagen der Kavität während des Zeitraums und/oder nach dem Zeitraum mit Ultraschall, welcher durch die Prüfeinrichtung bereitgestellt wird, und Nachweisen des reflektierten Ultraschalls mittels der Prüfeinrichtung, wodurch die Charakterisierung des Umformteils erfolgt.

The method for determining the degree of crosslinking in the elastomers during and / or after a production of the deformation part from the elastomers in an injection molding process comprises at least the steps a) to c) described in detail below:

1. a) providing at least one set up for the forming process tool, wherein the tool has at least one cavity for receiving an entropy-elastic material, and wherein in the tool further comprises a testing device for providing and detecting ultrasound is integrated, guided by the testing device ultrasonic waves to be provided;
2. b) introducing a material under pressure into the cavity and maintaining the pressure and a temperature for a period of time such that the forming part comprising the entropy-elastic material is produced; and
3. c) applying ultrasound to the cavity during the period and / or after the period of time provided by the testing device and detecting the reflected ultrasound by means of the testing device, whereby the characterization of the forming part takes place.

In this case, the steps a) to c) in the order given, starting with step a), continuing with step b) and ending with step c), wherein, depending on the choice of embodiment, one or more of steps a) to c), preferably the step b) and c), at least partially simultaneously can be performed. Farther In particular, step c) can be repeated several times, in particular until a relevant property, such as the degree of crosslinking, in the forming part has reached or exceeded a desired value. In addition, further steps, whether mentioned in the present application or not, may be additionally performed.

According to step a), provision is made of the at least one tool which is set up for a forming process, in particular an injection molding process or another forming process used in plastics processing, in particular thermoforming, injection stretch blow molding or extrusion blow molding. For this purpose, the tool has at least one cavity for receiving a material which already corresponds to the entropy-elastic material or from which the entropy-elastic material is formed during the production of the deformation part.

In a particularly preferred embodiment, in which elastomers are used as entropy-elastic materials, the cavity is thus adapted to receive a melt of the elastomers. During the injection molding process, the elastomer may preferably be heated to a molten state and then introduced into a cavity of a tool in accordance with step b) in the melt state under application of pressure. From the plastic melt in the cavity of the tool, which is held for a period of time at high pressure and temperature, the formation of the forming part, which can be finally removed by demolding from the cavity of the tool. For the production of the Umformteils from the elastomers, preferably temperatures of 100 ° C to 300 ° C, and pressures of 1 MPa to 3000 MPa used.

In a further, likewise particularly preferred embodiment, in which thermoplastics are used as entropy-elastic material, the cavity can thus be designed to accommodate a rubber-like thermoplastic, which may be in amorphous or partially crystalline form. The thermoplastic, which can exhibit a similar deformation behavior as elastomers during thermoforming, is subjected to a forming process used in plastics processing, in particular thermoforming, injection stretch blow molding or extrusion blow molding, according to step b), wherein the forming part is finally formed by removal from the cavity of the Tool can be removed. In this case too, temperatures of from 100 ° C. to 300 ° C., as well as pressures of preferably from 1 MPa to 3000 MPa, can be used for producing the forming part.

In accordance with the present invention, the tool further includes an integratable tester for providing and detecting ultrasound. The term "integrable" here refers to an arrangement of the test device, which is fixed or, preferably, releasably received in the tool. This has the consequence that the test device is preferably designed such that it can withstand the mentioned parameters, in particular the above-mentioned preferred value ranges for the temperature and the pressure, as they can occur in the cavity of the tool. In a particularly preferred embodiment, in this case the tool can be provided with a receptacle which is set up for insertion of the checking device into the tool in such a way that the checking device is located, as far as possible, on a side at which delivery and / or recording of the ultrasound takes place. can be in contact with a wall of the cavity. However, other embodiments are conceivable, in particular a configuration in which at least one conductor suitable for ultrasound is arranged between the test device and the at least one cavity.

The test device has at least one signal generator for generating and delivering the ultrasound for coupling according to step c) into the at least one cavity of the tool in which the entropy-elastic material to be examined is located. In this case, the investigation of the entropy-elastic material during the period and / or or after the period of manufacture of the entropy-elastic material can take place, as long as it is located in the at least one cavity of the tool. The term "ultrasound" here refers to the at least one signal generator stimulable fluctuations in pressure and / or density in an elastic medium in a frequency range of 100 Hz to 1 MHz, preferably from 20 kHz to 1 MHz. In the context of the present invention, the elastic medium comprises at least the entropy-elastic material located in the cavity of the tool and a coupling medium located between the at least one signal generator and the cavity for transmitting the ultrasound from the at least one signal generator to the volume of the cavity, in particular at least one wall of the cavity.

The term "signal generator", which may also be referred to as "loudspeaker", in the context of the present invention relates to a device for generating and emitting signals as continuous ultrasonic waves or in the form of ultrasonic pulses. Instead of the term "delivery", the terms "issue" or "emission" can also be used interchangeably. Starting from a usually small size of the volume The tool is preferably used only a single signal generator. With greater space in the tool, however, also an application of two or more signal transmitters is conceivable, which can be particularly advantageous, especially in the production of expanded and / or complex formed parts. The spatial design of the at least one signal generator is insignificant, as long as the signal generator is set up such that the output of the signal can preferably take place in a limited spatial angular range in order to be able to direct the radiated signal as completely as possible into the cavity in this way. For this purpose, the signal transmitter may preferably have a signal surface via which the signal generated in the signal generator can be radiated as completely as possible.

In this case, the generation and emission of the ultrasound takes place in particular with the aim of achieving coupling of the largest possible proportion of the emitted ultrasound into the cavity. The term "coupling-in" in this context describes a transfer of a portion of the ultrasound from the coupling medium into the volume of the cavity entropy-elastic material, whereby vibrations in the entropy-elastic material are excited, according to step c) for characterizing the entropy-elastic material can be used. In this case, the term "oscillations" designates repeated, temporal fluctuations of the ultrasound in the volume of the cavity, which are subjected to such a change by the entropy-elastic material in the cavity that, according to the invention, a determination of properties of the entropy-elastic material in the cavity is possible becomes.

According to the invention, the at least one signal generator provides guided ultrasound waves. The terms "guided waves", "plate waves" or "lamb waves" refer to ultrasonic waves that propagate between two parallel interfaces. How out M. Gaal, J. Döring, J. Prager, G. Brekow and M. Kreutzbruck, DGZfP Annual Meeting 2009, Di.1.A.2, pages 1-6, 2009 , known, corresponds to their wavelength at least the thickness of a plate used for this purpose, wherein the term "plate" describes an article whose thickness is smaller, preferably at least by a factor 10, than the extension in two perpendicular lateral directions. Due to their essentially two-dimensional propagation within the plate, the plate waves have a low divergence compared to longitudinal and transverse waves, and thus can spread over longer distances as compared to this. In addition, due to the geometry of the plate usually more symmetrical and asymmetric modes can form, the excitation of a few wave modes is particularly advantageous in terms of a clear evaluation of a reflected signal. The application of the cavity to the guided waves can thus lead to an excitation with different wave modes, wherein each of the wave modes can react differently to changes in the elastic constants of the entropy-elastic material. The signals are coupled via adapted probes into the tool, which are attached to the tool. These can be specially cooled or else designed as high-temperature probes

In addition to the guided ultrasonic waves, the at least one signal generator can also provide longitudinal and / or transverse ultrasonic waves. The longitudinal ultrasonic waves are particularly suitable for observing changes in the elastic constants with respect to the modulus of elasticity of the material during the crosslinking reaction. While transversal ultrasonic waves can not spread in liquids since no shear forces are transmitted therein, transverse ultrasonic waves are particularly suitable for observing changes in viscosity and the shear modulus. Due to the various preferred applications presented here, a combination of the different excitation modes for the ultrasonic waves can lead to an increase in the quality of the determination of the degree of crosslinking, since in this way several measured variables can be included in the evaluation.

The generation and / or the delivery of the ultrasound can preferably take place in the form of continuous ultrasound waves. Alternatively or additionally, the at least one signal generator can provide the ultrasonic waves in pulsed form as ultrasonic pulses which have wave packets from frequency spectra. Thus, not only the amplitude and the duration of a signal can be detected, but also the frequency spectra can be used. In this preferred embodiment, the ultrasonic pulse due to a scattering in the entropy-elastic material lose high frequency components, whereby the center frequency of the frequency spectrum decreases. As the degree of cross-linking increases the scattering in the entropy-elastic material, the observable center frequency decreases. As a result, by detecting the center frequency of the frequency spectrum, the degree of crosslinking in the entropy-elastic material can be determined. In addition, changes in the amplitudes and / or the transit times of different wave modes can be detected in the guided waves in addition to changes in the frequency spectrum.

• - der Veränderung einer Amplitude einer Ultraschall-Welle,
• - der Veränderung einer Laufzeit einer durch die Ultraschall-Wellen angeregten Mode und/oder
• - der Veränderung eines Frequenzspektrums der Ultraschall-Wellen bzw. der Ultraschall-Pulse.

Finally, according to step c), the desired characterization of the forming part takes place, which may in particular be in a determination of the degree of crosslinking of the elastomers or the wall thickness distribution of the forming part in the at least one cavity. However, a determination of further material parameters is possible. In order to characterize the forming part, the testing device has at least one detection device for detecting the ultrasound reflected from the cavity in the direction of the testing device, which may be changed by an interaction of the ultrasound with the entropy-elastic material located in the cavity with respect to the ultrasound irradiated into the cavity. The change in the ultrasound may preferably consist in the change of at least one measuring parameter of the ultrasound, in particular in FIG

• the change of an amplitude of an ultrasonic wave,
• the change in a transit time of a mode excited by the ultrasonic waves and / or
• - The change of a frequency spectrum of the ultrasonic waves or the ultrasonic pulses.

To carry out the method according to the invention, an electronic device, in particular a computer, may be provided which has a program code which is set up to carry out the present method.

In a further aspect, the present invention relates to a computer program which is adapted to carry out the described steps of the method and, if appropriate, further steps. For details, reference is made to the description of the method according to the invention.

In a further aspect, the present invention relates to a device for characterizing a deformation part of an entropy-elastic material during and / or after production of the deformation part in a forming process. The device according to the invention comprises at least one tool set up for carrying out the forming process, wherein the tool has at least one cavity for receiving the entropy-elastic material, and wherein the tool further has an integratable testing device for providing and detecting ultrasound, the testing device being set up for this purpose is to provide guided ultrasonic waves.

In a particularly preferred embodiment, the test device therefore has at least one signal generator, which can be set up to provide the guided ultrasound waves. Additionally or alternatively, the at least one signal generator may be further configured to also provide longitudinal and / or transverse ultrasonic waves. In addition, the at least one signal generator, irrespective of the type of ultrasound waves provided, may also be configured to provide the ultrasound in the form of continuous ultrasound waves and / or as ultrasound pulses.

• - Veränderung einer Amplitude der Ultraschall-Wellen;
• - Veränderung einer Laufzeit einer durch die Ultraschall-Wellen angeregten Wellenmode; und/oder
• - Veränderung eines Frequenzspektrums der Ultraschall-Wellen bzw. der Ultraschall-Pulse.

In a particularly preferred embodiment, the test device can be designed to determine the degree of crosslinking of an elastomer, for which purpose at least one of the following specific variables is used:

• Changing an amplitude of the ultrasonic waves;
• Changing a transit time of a wave mode excited by the ultrasonic waves; and or
• - Changing a frequency spectrum of the ultrasonic waves or the ultrasonic pulses.

In particular, the test device may be configured to determine the degree of crosslinking of the elastomer from the change in a center frequency of the frequency spectrum of the ultrasound pulses. As a preferred sensor, a hot test head is coupled to the tool via a supply line. The flow line can be cooled depending on the length. The piezo-based test head then records the acoustic signals. Alternatively, however, the signal can also be detected by a non-contact method by means of a laser vibrometer.

For further details with respect to the device according to the invention, reference is made to the description of the method according to the invention.

Advantages of the invention

The present method and the associated device enable a simple and reliable characterization of the forming part, in particular with regard to material parameters of the forming part, during and / or after production of the forming part in a forming process.

In particular, it could allow a determination of the degree of crosslinking in entropy-elastic materials, in particular elastomers, and thus allow reliable monitoring of the crosslinking reaction, thus leading to improved process stability, increased quality assurance and, in particular by a reduction of waste, to a total resource and more environmentally friendly injection molding process can lead. The recording of the degree of crosslinking during the injection molding process, preferably in the form of online monitoring, can be used in particular to ensure the best possible time for removal of the Umformteils with the desired properties of the injection mold can. By using several probes, it is possible to monitor a plurality of points in the resulting formed part, which may be advantageous, in particular, in the case of formed parts having an extended and / or complex shape.

Furthermore, they are preferably suitable for characterizing the material properties of heated thermoplastics which have a deformation behavior similar to partially crosslinked elastomers in an entropy-elastic state. In the case of known material properties of the heated thermoplastics, they can serve to determine wall thicknesses in components made of heated thermoplastics and thus preferably close an existing gap with regard to an inline wall thickness measurement, in particular a measurement of a wall thickness distribution in the formed part.

list of figures

• 1 eine schematische Darstellung eines bevorzugten Ausführungsbeispiels für eine erfindungsgemäße Vorrichtung zur Bestimmung eines Vernetzungsgrades in Elastomeren während und/oder nach einer Herstellung eines Umformteils aus den Elastomeren in einem Spritzgießverfahren; und
• 2A und 2B jeweils eine schematische Darstellung von zwei bevorzugten Ausführungsbeispielen für eine erfindungsgemäße Vorrichtung zur Charakterisierung eines Umformteils aus einem erwärmten Thermoplasten während und/oder nach einer Herstellung des Umformteils aus einem amorphem oder teilkristallinen Thermoplasten mittels Thermoformen.

Preferred embodiments of the present invention are illustrated in the figures and will be explained in more detail in the following description without limiting the generality. Hereby show:

• 1 a schematic representation of a preferred embodiment of an apparatus according to the invention for determining a degree of crosslinking in elastomers during and / or after a production of a Umformteils from the elastomers in an injection molding process; and
• 2A and 2 B each a schematic representation of two preferred embodiments of an inventive device for characterizing a formed part of a heated thermoplastic during and / or after a production of the Umformteils of an amorphous or semi-crystalline thermoplastic by means of thermoforming.

Embodiments of the invention

1 shows a schematic representation of a preferred embodiment of a device according to the invention 110 for determining a degree of crosslinking in elastomers as entropy-elastic material during and / or after production of a forming part 112 from the elastomers in an injection molding process. The preferred embodiment is for this purpose in the form of a cross section through a tool 114 shown, with the tool 114 for carrying out an injection molding process for the production of the Umformteils 112 is made of the elastomers at customary for injection molding pressures and temperatures.

The tool 114 has a cavity 116 on, with the cavity 116 in 1 for example, as a cavity between two mold plates joined together 118 , which usually as a nozzle-side mold plate 120 and as a closing side mold plate 122 be designated, is formed. The nozzle-side mold plate 120 has in this case an opening into which an injection device (nozzle) 124 is involved, which is the introduction of a melt 126 , which comprises the elastomers, into the cavity 116 allows. In the present embodiment, the tool receives 114 its stability due to two clamping plates 128 , which, with a centering ring 130 surrounded, the mold plates 118 press against each other. Other types of design of the tool 114 are possible, however. The tool 114 also has an embossing nip 132 on which a collapse of the two mold plates 118 of the tool 114 allows for the cavity 116 train. However, to prevent a part of the melt 126 through the embossing gap 132 from the cavity 116 can escape, are in the embodiment according to 1 the mold plates 118 arranged in such a way that they form a dipping edge 134 train the cavity 116 so seals that the cavity 116 despite the embossing gap 132 completely closed. The through an opening of the Prägespalts 132 enlarged cavity 116 can be about 80% to 95% with the melt containing the elastomers 126 are filled, which corresponds to about 100% of a volume of the formed part to be manufactured. When closing the tool 114 can by a closing movement, in particular in the form of a stamping, pressure on the melt 126 be exercised. To generate a high temperature in the melt 126 In addition, a heater 136 in the form of one or more heating wires, if possible in the vicinity of the cavity 116 arranged in at least one mold plates 118 be provided.

According to the invention, the tool 114 also a recording 138 for receiving a test device 140 preferably in one of the mold plates 118 on, here by way of example in the closing side mold plate 122 integrable testing device 140 is set up for the provision and detection of ultrasound. In this way, the testing device 140 fixed or, preferably, releasable with the tool 140 be connectable. By inserting the test device 140 in the recording 138 of the tool 114 may be a release of the ultrasound by the tester 140 and a Recording of the reflected ultrasound from the test device 140 directly through a wall 142 the cavity with which the test device 140 can be in contact. Other (in 1 not shown) embodiments insertion of the test device 140 in the recording 138 of the tool 114 are possible, in particular a configuration in which at least one conductor suitable for ultrasound between the test device 140 and the at least one cavity 116 is arranged. The insertion of the test device 140 in the recording 138 of the tool 114 On the other hand, however, has the consequence that the test facility 140 is preferably configured such that it meets the conditions occurring during the injection molding in the cavity 116 of the tool 114 , ie, temperatures preferably from 100 ° C to 300 ° C, and pressures preferably from 1 MPa to 3000 MPa, can withstand.

For generating ultrasonic waves, the test facility 140 via at least one signal generator 144 , which for coupling the ultrasound in the plastic melt 126 is set, wherein the melt 126 coupled ultrasonic vibrations in the melt 126 can stimulate present elastomers. The attachment and orientation of the signal generator 144 in this case is preferably such that the signal generator 144 as parallel as possible to the wall 142 the cavity 114 is aligned so that an exposure of the elastomers in the melt 126 through the signal generator 144 can be done as efficiently as possible. In particular, that is the signal generator 144 set up for the production of guided ultrasonic waves. At low surface temperatures of the tool of less than 60 °, the probe can also be coupled directly to the tool surface, otherwise an active cooling is integrated to protect the probe.

Additionally or alternatively, the signal generator 144 be configured to provide longitudinal and / or transverse ultrasonic waves. The signal generator 144 In this case, it can be configured to provide the ultrasound in the form of a continuous ultrasonic wave or, alternatively or additionally, as ultrasound pulses.

In the 1 schematically illustrated test device 140 further comprises a detection device 146 for detecting the excited ultrasonic vibrations in the elastomers in the melt 126 ,

• - Veränderung einer Amplitude der Ultraschall-Wellen;
• - Veränderung einer Laufzeit einer durch die Ultraschall-Wellen angeregten Mode; und/oder
• - Veränderung eines Frequenzspektrums der Ultraschall-Wellen.

The testing device 140 can continue via an evaluation device 148 which is adapted to be based on the detection means 146 data to determine the degree of crosslinking of the elastomer. At the evaluation device 128 This may be an electronic control device, which connections with the at least one signal generator 144 and the detection device 146 and on which a computer program can run to determine the degree of crosslinking of the elastomers, preferably by recording and evaluating at least one of the following specific quantities:

• Changing an amplitude of the ultrasonic waves;
• Changing a transit time of a mode excited by the ultrasonic waves; and or
• - Changing a frequency spectrum of the ultrasonic waves.

The degree of crosslinking of the elastomer can preferably be determined from the change in a center frequency of the frequency spectrum of the ultrasound pulses. Other ways of determining the degree of crosslinking of the elastomer are conceivable, however.

The evaluation device 148 can, as in 1 shown schematically in the testing device 140 be introduced. However, alternative embodiments are possible, in particular the embodiment in which the evaluation device 148 completely or partially outside the tool 114 located. Furthermore, the test device 140 continue via a communication device 150 Which is adapted to data and / or commands between the evaluation device 148 or, if the evaluation device 148 outside the tool 114 is arranged between the detection device 146 and an electronic control unit (not shown). The electronic control unit may in this case have a monitor and an input device, preferably in the form of a keyboard. While the monitor may preferably be configured to output data to a user or operator, an input device may in particular be used to input control commands to the test device 140 be furnished. In this way, an online monitoring of the degree of crosslinking can take place during the execution of the injection molding process. The online monitoring of the degree of crosslinking can in particular serve to be able to ensure the best possible time for a removal of the Umformteils with the desired properties of the injection mold.

Furthermore, the present invention may be useful for characterizing materials whose deformation properties are comparable to elastomers. The 2A and 2 B each show a schematic representation of a preferred embodiment of an inventive device for characterizing a formed part 112 from a heated thermoplastic during and / or after a production of the Umformteils 112 from a rubber-like thermoplastic by means of thermoforming. In analogy to 1 Here is in each case a test facility 140 in the test recording 138 of the tool 114 integrated. At the tool 114 in 2A it is a positive tool 152 , while 2 B a negative tool 152 shows. In addition, the two illustrated embodiments differ in that there are two test facilities 140 in 2A on the tool 114 while in 2 B the testing device 140 outside the tool 114 are arranged.

During forming, the rubbery thermoplastic, which may be in amorphous or partially crystalline form, contacts the tool 114 or gets in the cavity 116 of the tool 116 shaped. As a result of the deformation arises in the forming part 112 a wall thickness distribution, which by means of the test device 140 can be characterized. In addition to the information about the geometric dimensions of the formed part 122 , can be determined by means of the test device 140 also characterize material properties. In addition to the characterization of the material temperature, it is in particular possible to obtain spatially resolved information about molecular orientation and / or crystallinity.

LIST OF REFERENCE NUMBERS

110

device

112

remolded

114

Tool

116

cavity

118

mold plate

120

nozzle-side mold plate

122

closing side mold plate

124

Injection device (nozzle)

126

(Plastic) melt

128

platen

130

centering

132

embossing gap

134

dipping edge

136

heater

138

admission

140

test equipment

142

Wall of the cavity

144

signaler

146

detection means

148

evaluation device

150

communicator

152

positive tool

154

negative tool

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007015667 A1 [0007]

Cited non-patent literature

• M. Gaal, J. Döring, J. Prager, G. Brekow and M. Kreutzbruck, DGZfP Annual Meeting 2009, Di.1.A.2, pages 1-6, 2009 [0027]

Claims (12)

Method for characterizing a forming part (112) made of an entropy-elastic material during and / or after production of the forming part (112) in a forming process, comprising the steps of: a) providing at least one tool (114) adapted for the forming process, wherein the tool (114) has at least one cavity (116) for receiving an entropy-elastic material, and wherein in the tool (114) further comprises a test device (140) for providing and is integrated for the detection of ultrasound, being provided by the tester (140) guided ultrasonic waves; b) introducing a material under pressure into the cavity (116) and maintaining the pressure and a temperature for a period of time such that the forming part (112) comprising the entropy-elastic material is produced; and c) sonicating the cavity (116) during the time period and / or after the period of time provided by the testing device (140) and detecting the reflected ultrasound by means of the testing device (140), whereby the characterization of the forming part (112) he follows. A method according to the preceding claim, wherein the entropy-elastic material comprises elastomers, wherein the characterization of the forming part (112) comprises a determination of a degree of crosslinking in the elastomers during and / or after the production of the forming part (112) from the elastomers in an injection molding process Step b) introducing a melt (126) from the elastomers under pressure into the cavity (116) of the tool (114) and maintaining the pressure and a temperature over a period of time such that the forming member (112) is made of the elastomers and wherein during step c) the determination of the degree of crosslinking in the elastomers is carried out by detecting the reflected ultrasound by means of the test device (140). A method according to the preceding claim, wherein the tester (140) determines the degree of crosslinking of the elastomers by determining at least one of the following specific quantities: Changing an amplitude of the ultrasonic waves; Changing a transit time of at least one ultrasonic mode excited by the ultrasonic waves; and or - Changing a frequency spectrum of the ultrasonic waves. Method according to the preceding claim, wherein the degree of crosslinking of the elastomers is determined by the test device (140) from the change of a center frequency of the frequency spectrum of the ultrasonic waves in pulsed form. Method according to Claim 1 wherein the entropy-elastic material comprises at least one heated thermoplastic, wherein during step b) a plastic semi-finished product made of an amorphous or semi-crystalline thermoplastic under pressure differences in the cavity (116) of the tool (114) is introduced and heated, or wherein the tool (114) as a positive tool is configured and an impression of the thermoplastic under pressure differences and heating via a convex shape of the positive tool, and wherein during step c) the characterization of the Umformteils (112) from the heated thermoplastic by detecting the reflected ultrasound by means of the test device (140). Method according to the preceding claim, wherein the wall thickness distribution of the forming part (112) is determined by the checking device (140). A method according to any one of the preceding claims, wherein further longitudinal and / or transversal ultrasonic waves are provided by the inspection means (140). Method according to one of the preceding claims, wherein ultrasound is provided in the form of ultrasound pulses by the test device (140). A computer program adapted to perform the steps of the method of any one of the preceding method claims. Device (110) for determining the characterization of a forming part (112) of an entropy-elastic material during and / or after production of the forming part (112) in a forming process, comprising at least one tool (114) adapted for carrying out the forming process, wherein the tool (114) at least one cavity (116) for receiving the entropy-elastic material, and wherein the tool (114) further comprises an integratable tester (140) for providing and detecting ultrasound, the tester (140) being adapted to to provide guided ultrasonic waves. Apparatus (110) according to the preceding claim, wherein the tester (140) is further adapted to provide longitudinal ultrasound To provide waves and / or transverse ultrasonic waves. The apparatus (110) of the preceding claim, wherein the tester (140) is further configured to provide the ultrasound as ultrasound pulses.

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