DE102021131438A1 - Functional element with a plurality of actuators made of two-way shape memory polymers - Google Patents

Abstract

A functional element with a first actuator made of a first two-way shape memory polymer and at least one second actuator made of a second two-way shape memory polymer is proposed, which are programmed in such a way that the first and second actuators reversibly move back and forth between a first shape and a second shape are switchable, the first and second two-way shape memory polymer of the first and second actuator having a first switching temperature at which it is converted from its second shape into its first shape, and a second switching temperature different from its first switching temperature at which it changes from its first form is converted into its second form. The first and/or second two-way shape memory polymer of the first and/or second actuator is provided with an electromagnetic radiation absorbing or reflecting medium in order to ensure accelerated or decelerated heating in the event of exposure of the two-way shape memory polymer to electromagnetic radiation, the Functional element can include in particular a plurality of such actuators.

Description

• - eine erste Schalttemperatur, bei welcher es aus seiner zweiten Form in seine erste Form überführt wird, und
• - eine von seiner ersten Schalttemperatur verschiedene, zweite Schalttemperatur, bei welcher es aus seiner ersten Form in seine zweite Form überführt wird, aufweist.

The invention relates to a functional element with at least one first actuator, which contains at least one first two-way shape memory polymer or is essentially formed entirely from it, which is programmed in such a way that the first actuator can be reversibly switched back and forth between a first shape and a second shape , wherein the at least one first two-way shape memory polymer of the first actuator at least

• - a first switching temperature at which it is transformed from its second form to its first form, and
• - A different from its first switching temperature, second switching temperature at which it is transferred from its first form into its second form.

Shape memory polymers are polymers which usually consist of at least two polymer components or, in particular, of one polymer component with different segments. On the one hand, these are “hard” segments that also function as network points.

On the other hand, there are "soft" segments that connect the network points with each other and act as switching segments and are also referred to as such. The switching segments are amorphous or elastic at elevated temperatures, while rigid at lower temperatures (they are in semi-crystalline or vitrified form in this case). Such polymers can be programmed in terms of their shape by being heated to a temperature which corresponds at least to the so-called switching temperature at which the phase transition (glass transition or melting transition) of the soft or switching segments takes place. At such a temperature, the polymer can then be mechanically deformed under the action of a deforming force, after which it can be cooled to its so-called shape-fixing temperature while maintaining the deformation, which corresponds to the crystallization temperature or glass transition temperature of the soft or switching segments and is in the range of the switching temperature of the shape memory polymers can, but in contrast is usually at least somewhat lower. The soft or switching segments are then again in a partially crystalline or vitrified form, so that the shape is retained. However, this shaping is only temporary insofar as when a shape memory polymer that is “programmed” in this way, i.e. mechanically deformed, is heated to a certain temperature, namely to its switching temperature, the soft segments (switching segments) are converted back into their amorphous or flexible form , so that they can no longer counteract the entropy-elastic restoring force induced by the hard component (network points) and the shape-memory polymer resumes its original shape, i.e. the mechanical deformation is "reversed" without the need for a new force to be applied. Furthermore, there is often also the possibility of programming by cold deformation, in that the shape memory polymers can be deformed at a temperature below their switching temperature, e.g. at ambient temperature, and optionally, if the shape-fixing temperature is lower than this, can be cooled to their shape-fixing temperature. In this case, too, only temporary deformation takes place insofar as repeated heating at least to the switching temperature in order to convert the soft segments (switching segments) into the amorphous or flexible phase and thereby relax the mechanical stresses induced during the cold deformation, recovery takes place without having to apply a deformation force again.

In addition to such a shape memory, thermoresponsive polymers usually also have a temperature memory. This means that when the shape memory effect is triggered, the shape recovery begins at about the temperature at which the mechanical deformation was introduced into the material beforehand. Such material behavior is exhibited, for example, by shape memory polymers with semi-crystalline network structures, such as thermoplastic polyurethane elastomers (N. Fritzsche, T. Pretsch in Macromolecules 47, 2014, 5952-5959; N. Mirtschin, T. Pretsch in RSC Advances 5, 2015, 46307- 46315) .

In addition, shape-memory polymers are known which have two-way shape-memory properties and can therefore be switched thermoreversibly, with the switching segments of such two-way shape-memory polymers undergoing a change in shape during the transition between their primarily partially crystalline state and their primarily amorphous or flexible state such that on the one hand they can be changed by cooling of the polymer below the crystallization temperature, which is referred to as the "first switching temperature" in the context of the present disclosure, on the other hand by heating the Polymers in the switching temperature range, which is referred to as the "second switching temperature" in the context of the present disclosure, can be reversibly switched back and forth between its permanent shape and its temporary shape, ie the correspondingly programmed two-way shape memory polymer deforms back and forth automatically with appropriate temperature control here. Such two-way shape memory polymers are, for example, from T. Pretsch, M. Bothe: "Bidirectional actuation of a thermoplastic polyurethane elastomer", Journal of Materials Chemistry A, 46 (2013), 14.491-14.497, or from M. Bothe, T. Pretsch: "Two-way shape changes of a shape-memory poly(ester urethane)", Macromol. Chem. Phys. 213 (2012), 2378-2385).

The back and forth deformation of such two-way shape memory polymers can, on the one hand, take place more or less purely temperature-induced, without deformation forces having to be applied for this purpose. In addition, two-way shape-memory polymers are known which develop their two-way shape-memory properties in particular under the influence of a permanent mechanical preload, such as as a result of a permanent pressure, so that they are under permanent tension in order to favor the crystallization of the soft segments during cooling, such as it, for example, from the article by M. Bothe, T. Pretsch: "Two-Way Shape Changes of a Shape Memory Poly(ester urethane)" in Macromol. Chem. Phys. 213 (2012), 213, 2378-2385.

In order to modify the switching temperature of shape memory polymers - be it conventional one-way or two-way shape memory polymers, as addressed in the context of the present disclosure - it is also known to add additives in the form of electromagnetic radiation-absorbing media to the shape memory polymers, so that heat the shape memory polymer as a result of irradiation with electromagnetic radiation in the respective frequency range and bring it to one of its switching temperatures more quickly. For example, describes the WO 2020/228920 A1 an energy self-sufficient water reservoir for the temporary storage and dispensing of water, in particular in the form of humidity and/or rainwater, which on the one hand contains a compressible storage material suitable for the reversible absorption of water and on the other hand a supporting structure in which the storage material is embedded. The support structure is made of a reversibly switchable two-way shape memory polymer, which in one form accommodates the storage material essentially without pressure (environmental moisture can thus be absorbed at cool temperatures) and in its second form compresses the storage material (water absorbed on the storage material can thus be pressed out of the storage material at higher temperatures), in which case the two-way shape-memory polymer can be provided with sunlight-absorbing media as required, in order to ensure that it heats up more quickly, so that it can be brought to its (higher) switching temperature earlier.

More recently, two-way shape memory polymers have also started to be used for functional elements or actuators in order to initiate mechanical switching and/or actuating processes that do not require external energy, depending on the respective switching temperatures of the two-way shape memory polymers. For example, describes the DE 10 2020 001 380 A1 a latent heat storage device with a phase change material accommodated in a storage device and with a triggering mechanism for triggering the crystallization of the phase change material by the latter being brought into contact with a crystallization nucleating agent. The triggering mechanism further comprises a mechanical functional element made of a two-way shape memory polymer, which is programmed in such a way that the functional element switches between its first form, in which it brings the nucleating agent into contact with the phase change material in order to trigger its crystallization, and a second form, in which it brings the nucleation agent out of contact with the phase change material, can be reversibly switched back and forth, the change in shape of the functional element being triggered by heating or cooling the two-way shape memory polymer to its first or second switching temperature.

From the DE 10 2020 000 159 A1 an insulating device with an insulating material element made of a foamed two-way shape memory polymer is known, which is reversible between a first form, in which the insulating material element has a first heat transfer coefficient, and a second form, in which the insulating material element has a second heat transfer coefficient that differs from the first heat transfer coefficient can be switched back and forth, the change in shape of the insulation element being triggered by heating or cooling the two-way shape memory polymer to its first or second switching temperature. This can be done, for example, by the shape memory polymer having air passages in its one form, which are closed in its other form.

The invention is based on the object of further developing a functional element with at least one first actuator based on two-way shape memory polymers of the type mentioned in a simple and cost-effective manner such that additional functionalities are imparted to it and in this way novel areas of application can be opened up.

• - zumindest eine erste Schalttemperatur, bei welcher es aus seiner zweiten Form in die erste Form überführt wird, und
• - eine von seiner ersten Schalttemperatur verschiedene zweite Schalttemperatur, bei welcher es aus seiner ersten Form in seine zweite Form überführt wird, aufweist, wobei das erste Zweiwege-Formgedächtnispolymer des ersten Aktuators und/oder das zweite Zweiwege-Formgedächtnispolymer des zweiten Aktuators mit einem elektromagnetische Strahlung absorbierenden oder reflektierenden Medium versehen ist, um im Falle einer Exposition des Zweiwege-Formgedächtnispolymers mit elektromagnetischer Strahlung für eine beschleunigte oder verlangsamte Erwärmung zu sorgen.

According to the invention, this object is achieved with a functional element of the type mentioned at the outset in that the functional element has at least one second actuator, which contains at least one second two-way shape memory polymer or is essentially formed entirely from it, which is programmed in such a way that the second actuator is between a first shape and a second shape is reversibly switchable back and forth, wherein the at least one second two-way shape memory polymer of the second actuator

• - at least a first switching temperature at which it is transferred from its second form to the first form, and
• - has a second switching temperature different from its first switching temperature, at which it is converted from its first form into its second form, the first two-way shape memory polymer of the first actuator and/or the second two-way shape memory polymer of the second actuator being exposed to electromagnetic radiation absorbing or reflective medium to provide accelerated or decelerated heating upon exposure of the two-way shape memory polymer to electromagnetic radiation.

The configuration according to the invention consequently provides a functional element with a plurality of actuators made of two-way shape memory polymers, the two-way shape memory polymer of at least one or more actuators being provided with a medium absorbing or reflecting electromagnetic radiation in order, in the event of exposure of the two-way shape memory polymer of the respective To provide actuators with electromagnetic radiation for accelerated or slowed heating. In this way, for example, depending on the exposure of the actuators of the functional element to electromagnetic radiation, either a more or less synchronous switching of all actuators of the functional element between the at least two preprogrammed shapes can be achieved, provided the actuators are made of the same two-way shape memory polymers or at least those with practically identical switching temperatures are formed, or a selective, accelerated and/or retarded switching of at least some actuators of the functional element between the at least two pre-programmed forms can also be achieved, for example, if only one or some actuators are exposed to the electromagnetic radiation, as a result of which they either move faster (in the case a medium absorbing the electromagnetic radiation) or more slowly (in the case of a medium absorbing the electromagnetic radiation) to one of their switching temperatures in order to be switched from one form to the other. In addition, in the case of a functional element with a large number of such actuators, it is conceivable, for example, for the functional element to be able to assume a large number of different shapes or intermediate positions between the first and the second shape of a respective actuator if some actuators move as a result of the different effects of electromagnetic radiation are in their first and others in their second form.

The first two-way shape memory polymer of the at least one first actuator can be a different two-way shape memory polymer than the second two-way shape memory polymer of the at least one second actuator, so that in addition to different heating and cooling rates of the actuators of the functional element at the respective Under the influence of electromagnetic radiation, different switching temperatures of the two-way shape memory polymers are also provided for at least some actuators of the functional element, which can thus be switched back and forth between their shapes at different temperatures. Alternatively, the first two-way shape memory polymer of the at least one first actuator can also be the same two-way shape memory polymer as the second two-way shape memory polymer of the at least one second actuator, so that although all actuators of the functional element have the same switching temperatures, due to the electromagnetic Radiation-absorbing or reflecting medium at least some actuators are heated or cooled more quickly or more slowly to the respective switching temperature when exposed to such radiation.

As is known as such from the prior art cited above, it is also conceivable that the at least one two-way shape memory polymer of at least one, some or all actuators of the functional element are not mechanically preloaded, with the at least one two-way shape memory polymer of a respective actuator a purely temperature-dependent and without the influence of programmed to undergo a reversible change in shape between its first shape and its second shape under the influence of external forces. Instead, depending on the type of two-way shape memory polymer used for the actuators of the functional element, it can also be provided that the at least one two-way shape memory polymer of one, some or all actuators is mechanically under permanent tension, with the generation of such a permanent tension, for example, the gravitation of a acting on a respective actuator surface load, a spring or the like can be used, so that the permanent mechanical preload to promote the two-way shape memory effect does not require any external energy supply.

Depending on the desired switching of the actuators of the functional element according to the invention depending on the electromagnetic radiation acting on them, either all actuators or at least one or more actuators can be provided with the medium absorbing electromagnetic radiation. In addition, it is conceivable that at least two or more actuators are provided with (each) different electromagnetic radiation-absorbing media and/or with different proportions of the electromagnetic radiation-absorbing medium, so that the absorption capacity of at least some actuators for electromagnetic radiation is different and these Exposure to electromagnetic radiation consequently reach their respective switching temperature more quickly or more slowly in order to trigger the shape memory effect.

The medium absorbing or reflecting electromagnetic radiation, with which at least some actuators of the functional element according to the invention are provided, can preferably absorb or reflect electromagnetic radiation in the electromagnetic spectrum of the sun, e.g. in the infrared spectrum, in the ultraviolet spectrum and/or in particular in the visible spectrum, so that when exposed to electromagnetic radiation in such a frequency range, heating is either accelerated (if the radiation is absorbed) or retarded (if the radiation is reflected) and the switching temperature of the two-way shape memory polymer is thus reached more quickly or more slowly. Of course, artificial irradiation of at least some actuators of the functional element with electromagnetic radiation in the corresponding frequency range is also possible in this way, e.g. by means of light sources specific to the wavelength, such as lasers, infrared radiators and the like.

The medium absorbing or reflecting electromagnetic radiation can be applied to the two-way shape memory polymer of at least one actuator, for example in the form of a coating, e.g. in the form of a paint, a film, etc., with the coating being e.g To absorb radiation, or bright, largely white or mirrored to reflect as much electromagnetic radiation as possible. The medium absorbing or reflecting electromagnetic radiation can also be introduced into the two-way shape memory polymer of at least one actuator or dispersed in its polymer matrix, for example in the form of a filler, in particular in finely particulate form. Such fillers can consequently be fillers that absorb or reflect electromagnetic radiation, preferably in fine-particle form. Fillers that absorb electromagnetic radiation in the sunlight spectrum, with which the at least one two-way shape memory polymer of at least one actuator can be added and/or coated and which cause the two-way shape memory polymer to heat up more quickly when exposed to light in the sunlight spectrum, can, for example, be based on Carbon, e.g. in the form of graphite or expanded graphite, soot, carbon nanotubes (CNT), graphene flakes or the like, metals and metal compounds including their alloys and oxides, etc., whereby of course combinations of several different filler materials can also be used . In addition, the at least one two-way shape memory polymer of the actuators of the functional element can, of course, also have other additives that are largely known from the prior art, such as lubricants and other processing aids, plasticizers, antioxidants, UV stabilizers, reinforcing materials, flame retardants, antistatic agents, Hydrolysis stabilizers, impact modifiers, biostatics, etc.

Depending on the intended use of the functional element according to the invention, the two-way shape memory polymer of at least one or some or all actuators can be programmed, for example, in such a way that the actuator has at least one passage channel with a first cross section in its first form and a passage channel with one of the first cross section in its second form Cross-section having different second cross-section or no through-channel at all. In addition, the two-way shape memory polymer of at least one or some or all of the actuators can be programmed, for example, in such a way that the actuator has a different length, height and/or width in its first shape than in its second shape. Alternatively or additionally, it is conceivable, for example, that the two-way shape memory polymer at least one or some or all of the actuators is programmed such that the actuator has a different bending and/or torsion in its first form than in a second form.

While in principle any known two-way shape memory polymers can be used for the actuators of the functional element according to the invention, the switching temperatures of which are in a range that is suitable for the respective application of the functional element, the at least one two-way shape memory polymer of the actuators can, for example, preferably be a polyurethane elastomer, in particular a polyester or polyether urethane elastomer, although of course polymer mixtures or blends or compounds made from or with two-way shape memory polymers can also be used. Examples of such two-way shape memory polymers are known, for example, from the article by T. Pretsch, M. Bothe: "Bidirectional actuation of a thermoplastic polyurethane elastomer", Journal of Materials Chemistry A, 20 (2013), 14.491-14.497, with a thermoplastic polyurethane elastomer being used as an example with hard segments or network points based on methylenediphenyl isocyanate (MDI) and 1,4-butanediol (partially crystalline/amorphous) and with switching or soft segments based on polybutylene-1,4-adipate, which is obtained by reacting 1,4 -Butanediol can be obtained with adipic acid, should be mentioned. When this polymer is first heated to a deformation temperature of about 60°C, it can be deformed for the purpose of programming its two-way shape memory, preferably at a slow deformation rate of, for example, about 1%/s, e.g. with a total elongation of up to about 1000%. whereupon it is cooled to about 0°C to achieve elongation of the material. If the polymer is then heated up to the switching temperature range ("second switching temperature") of around 30°C to 55°C, the switching segments are melted and converted from their primarily semi-crystalline state into their primarily amorphous or flexible state, so that the polymer is switched back again or contracts without a deformation force having to be applied again for this purpose. If it is then cooled back to its crystallization temperature (“first switching temperature”) in the range below about 20°C, the switching segments crystallize again and the polymer is switched or deformed again, etc. Examples of two-way shape memory polymers, their two-way shape memory properties can be favored in particular by the action of a permanent compressive force, so that the two-way shape memory polymer is under permanent mechanical stress, for example from the article by M. Bothe, T. Pretsch: "Two-way shape changes of a shape memory poly(ester urethane)” in Macromol. Chem. Phys. 213 (2012), 213, 2378-2385, with a polyester urethane having soft segments made of crystallizable poly(1,4-butylene adipate) (PBA) being mentioned as an example, which has two-way shape-memory properties in the correspondingly programmed state in order to change under the when cooled crystallization temperature (“first switching temperature”) to expand and to contract when heated above the switching temperature range (“second switching temperature”). In order in particular to favor the transition between an amorphous state of the PBA at high temperatures into a semi-crystalline state of the PBA at low temperatures and to achieve a very high proportion of crystallinity of the PBA - accompanied by a very strong deformation - such a two-way shape memory polymer can be subjected to a mechanical stress, e.g. in the range of about 1.5 MPa. In addition, it should be pointed out at this point that by varying such a mechanical stress, in particular the crystallization temperature (“first switching temperature”) of the soft segments of the two-way shape memory polymer and, as a result, their melting temperature (“second switching temperature”), can also be adjusted specifically to the respective intended use of the device according to the invention Latent heat storage or can be adapted to the local conditions of its location. Furthermore, the at least one two-way shape memory polymer of the actuators of the functional element can also only be under permanent mechanical stress in certain areas, for example as a result of the gravitational pull of a surface load acting only in certain areas on the respective actuator.

In addition, the at least one two-way shape memory polymer of the actuators of the functional element can advantageously be a plasticizable, thermoplastic polymer, which makes it easy to produce using practically any thermoplastic processing method and makes it more environmentally friendly than thermosets in terms of easy recycling . While such thermoplastic two-way shape memory polymers, as I said, largely by means of conventional thermoplastic processing methods such as extrusion, injection molding, hot pressing, calendering, blow molding, rotational molding, etc., can be processed into the actuators of the functional element, which then, for example, in the manner described above their first and second form can be programmed, the actuators of the functional element can also be produced, for example, by means of a rapid prototyping method, such as in particular by a fused layer method, as is primarily used in 3D printers. Also known as fused deposition modeling (FDM) or fused filament fabrication (FFF). Driving is a manufacturing process in which a thermoplastic polymer or a polymer blend of thermoplastic polymers is plasticized and deposited in layers using a nozzle usually provided in the print head of the 3D printer in order to permanently replace the actuator, which is ultimately formed from a large number of such layers to generate shape. On the one hand, this enables the layered production of relatively complex actuators, which is also suitable for small series and cannot be produced or can only be produced with difficulty using conventional thermoplastic processing methods such as injection molding, extrusion, etc., with the melt layer process also being used for the series production of actuators with relatively complex geometry and / or surface structures can be used. In the case of 3D printing, also referred to as “additive manufacturing”, a three-dimensional model of the actuators to be produced is usually created digitally, which can be done in particular using the known methods of computer-aided design (CAD). In addition, using suitable software, such as a so-called slicer program (e.g. Cura™ or similar), the three-dimensional model of the actuators to be produced is broken down into a plurality of thin layers, whereupon the plasticized polymer is cut layer by layer using the nozzle of the correspondingly moved print head is deposited to build up the actuator layer by layer. The hardening process - or more precisely: the solidification process - begins immediately after the discharge of the more or less strand-like or droplet-shaped polymer plasticate from the nozzle of the print head, whereby the separated plasticate solidifies, for example at ambient temperature or with active cooling. If an actuator produced in this way from a thermoresponsive two-way shape memory polymer is heated or cooled to the respective switching temperature after it has previously been programmed in the manner described above, it can also be switched back and forth reversibly between its first shape and its second shape become.

The CN 105 936 747 A describes, for example, such a filament made of a polymer blend of thermoplastic polyurethanes on the one hand and acrylonitrile-butadiene-styrene (ABS) on the other hand, which can be processed using the melt layer process using 3D printers and has two-way shape memory properties. In addition, in the context of the present invention is also preferred polymer blend with such two-way shape memory properties based on thermoplastic polyurethanes and polyolefins, such as in particular high density polyethylene (HDPE), from the DE 10 2018 003 274 A1 known, which is hereby made the subject of the present disclosure.

In addition, the thermoplastic two-way shape memory polymer of the actuators of the functional element can also be produced, for example, by means of selective laser sintering (SLS), as is described, for example, in the technical article "Characterization of creeping and shape memory effect in laser sintered thermoplastic polyurethane" by S. Yuan et al. , Journal of Computing and Information Science in Engineering, 16 (2016), Issue 4, pages 041007-041007-5, it being possible for the actuators to be given very complex geometries and/or surface finishes as well.

Two exemplary embodiments of two-way shape memory polymers suitable for the actuators of a functional element according to the invention in the form of thermoplastic polyester urethanes (TPU) based on poly(1,6-hexylene adipate)diol (PHA) or poly(1,4-butylene adipate) are given below merely as examples ) diol (PBA) as the polyol component and 4,4'-methylenediphenyl isocyanate (MDI) as the diisocyanate component with 1,4-butanediol (BD) as the chain extender, which have been synthesized from the tabulated starting materials.

Example 1:

• - Kristallisationstemperaturbereich der Schalt- bzw. Weichsegmente auf Basis von PHA („erste Schalttemperatur):
  • ca. 0°C bis ca. 20°C,
• - Schmelztemperaturbereich der Schalt- bzw. Weichsegmente auf Basis von PHA („zweite Schalttemperatur):
  • ca. 30°C bis ca. 50°C,
• - Hartsegmentanteil (MDI/BD): ca. 15%,
• - NCO-Index: 1,005.

Komponente Substanz Anteil Molmasse Polyol PHA 100 3000 Diisocyanat MDI 15,5 250,25 Kettenverlängerer BD 2,5 90,12 Katalysator Titan-(IV)-Kat. 0,0005 - Additiv 1 Antioxidans 0,1 - Additiv 2 Verarbeitungsadditiv 0,7 - Additiv 3 Hydrolysestabilisator 0,6 Two-way shape memory polymer "TPU-PHA 3000/15":

• - Crystallization temperature range of the switching or soft segments based on PHA (“first switching temperature”):
  • approx. 0°C to approx. 20°C,
• - Melting temperature range of the switching and soft segments based on PHA (“second switching temperature”):
  • approx. 30°C to approx. 50°C,
• - Hard segment content (MDI/BD): approx. 15%,
• - NCO index: 1.005.

component substance Portion molar mass polyol PHA 100 3000 diisocyanate MDI 15.5 250.25 chain extender BD 2.5 90.12 catalyst Titanium (IV) Cat. 0.0005 - additive 1 antioxidant 0.1 - additive 2 processing additive 0.7 - additive 3 hydrolysis stabilizer 0.6

Example 2:

• - Kristallisationstemperaturbereich der Schalt- bzw. Weichsegmente auf Basis von PBA ("erste Schalttemperatur):
  • ca. -10°C bis ca. 10°C,
• - Schmelztemperaturbereich der Schalt- bzw. Weichsegmente auf Basis von PBA ("zweite Schalttemperatur):
  • ca. 30°C bis ca. 50°C,
• - Hartsegmentanteil (MDI/BD): ca. 15%,
• - NCO-Index: 1,005.

Komponente Substanz Anteil Molmasse Polyol PBA 100 4000 Diisocyanat MDI 14,8 250,25 Kettenverlängerer BD 3,0 90,12 Katalysator Titan-( IV)-Kat. 0,0005 - Additiv 1 Antioxidans 0,1 - Additiv 2 Verarbeitungsadditiv 0,7 - Additiv 3 Hydrolysestabilisator 0,6 Two-way shape memory polymer "TPU-PBA 4000/15":

• - Crystallization temperature range of the switching or soft segments based on PBA ("first switching temperature):
  • approx. -10°C to approx. 10°C,
• - Melting temperature range of the switching or soft segments based on PBA ("second switching temperature"):
  • approx. 30°C to approx. 50°C,
• - Hard segment content (MDI/BD): approx. 15%,
• - NCO index: 1.005.

component substance Portion molar mass polyol PBA 100 4000 diisocyanate MDI 14.8 250.25 chain extender BD 3.0 90.12 catalyst Titanium (IV) Cat. 0.0005 - additive 1 antioxidant 0.1 - additive 2 processing additive 0.7 - additive 3 hydrolysis stabilizer 0.6

However, it should be pointed out at this point that the at least one two-way shape memory polymer of the actuators of the functional element does not necessarily have to be a thermoplastic polymer, but in principle primarily elastomeric or duroplastic polymers can also be considered. Suitable representatives of such duroplastic two-way shape memory polymers are, for example, in the technical article "Catalyst-free thermoset polyurethane with permanent shape reconfigurability and highly tunable triple-shape memory performance" by N. Zheng et al. in ACS Macro Letters 6, 4 (2017), pages 326-330.

According to a further development of the functional element according to the invention, it can be provided that it also comprises at least one mirror and/or at least one screen, which is designed to focus electromagnetic ambient radiation onto at least one or more of the actuators in order to target one or more actuators to a greater extent to electromagnetic radiation than other actuators of the functional element, so that they can, for example, heat up more quickly than other actuators and thus reach their switching temperature more quickly in order to be switched from one form to the other with a time offset to the other actuators.

Alternatively or additionally, it can be provided in this context that the functional element also comprises at least one shield, which is used for at least partial shielding of elec romagnetic ambient radiation is designed on at least one or more of the actuators in order to expose one or more actuators to the electromagnetic radiation in a targeted manner to a lesser extent than other actuators of the functional element, so that they heat up more slowly than other actuators, for example, and thus reach their switching temperature later, in order to be switched from one form to the other at a different time than the other actuators. Instead of a shield, for example, a cooling device can also be provided for corresponding purposes, which is designed to cool at least one or more of the actuators, the cooling device being powered, for example, by a cooling device operated with external, in particular electrical, energy, for example in the form of a Peltier element or The like, can be formed or a cold reservoir, such as a water reservoir, a natural body of water, soil, etc., can include.

The functional element according to the invention, formed from a plurality of such actuators, can be used for a wide variety of applications, for example having a plurality of actuators arranged essentially in parallel, which have a first shape and a second shape with different geometric dimensions and as control elements for windows , doors or shading devices are formed.

The functional element according to the invention can also include, for example, a plurality of actuators arranged essentially in parallel, which have a first shape with at least one through-channel and a second shape with at least one through-channel of different cross-section or no through-channel and are designed as a valve unit for fluids. Such functional elements can be used, for example, in (micro)fluidics or as photosensitive insulating materials.

In addition, a functional element according to the invention can also be used, for example, as an alternator for generating kinetic energy, in which case the functional element can have, for example, a plurality of actuators arranged on the circumference of a drive wheel, which have a first shape and a second shape with different geometric dimensions with a radial extension component of the drive wheel have to rotate the drive wheel gravimetrically.

• 1 eine fotografische Ansicht eines Prototypen eines nach Art einer Lichtkraftmaschine ausgestalteten Funktionselementes mit einer Mehrzahl an am Umfang eines Antriebsrades angeordneten Aktuatoren aus Zweiwege-Formgedächtnispolymeren;
• 2 eine fotografische Detailansicht des mit den Aktuatoren ausgestatteten Antriebsrades des Funktionselementes gemäß 1;
• 3A eine fotografische Detailansicht eines der Aktuatoren des Funktionselementes gemäß 1 und 2, wobei sich das Zweiwege-Formgedächtnispolymer in einer ersten Form des Aktuators befindet;
• 3B eine fotografische Detailansicht eines der Aktuatoren des Funktionselementes entsprechend der 3A, wobei sich das Zweiwege-Formgedächtnispolymer in einer zweiten Form des Aktuators befindet;
• 4A eine fotografische Detailansicht einer alternativen Ausgestaltung eines Aktuators des Funktionselementes gemäß 1 und 2, wobei sich das Zweiwege-Formgedächtnispolymer in einer ersten Form des Aktuators befindet; und
• 4B eine fotografische Detailansicht eines der Aktuatoren des Funktionselementes entsprechend der 4A, wobei sich das Zweiwege-Formgedächtnispolymer in einer zweiten Form des Aktuators befindet.

Further features and advantages of the invention result from the following description of an exemplary embodiment with reference to the drawing. show:

• 1 a photographic view of a prototype of a functional element designed in the manner of an alternator with a plurality of actuators made of two-way shape memory polymers arranged on the circumference of a drive wheel;
• 2 a detailed photographic view of the drive wheel of the functional element equipped with the actuators according to FIG 1 ;
• 3A a detailed photographic view of one of the actuators of the functional element according to FIG 1 and 2 wherein the two-way shape memory polymer is in a first shape of the actuator;
• 3B a photographic detailed view of one of the actuators of the functional element according to FIG 3A wherein the two-way shape memory polymer is in a second shape of the actuator;
• 4A a photographic detail view of an alternative embodiment of an actuator of the functional element according to FIG 1 and 2 wherein the two-way shape memory polymer is in a first shape of the actuator; and
• 4B a photographic detailed view of one of the actuators of the functional element according to FIG 4A , wherein the two-way shape memory polymer is in a second shape of the actuator.

In the 1 is an embodiment of a functional element according to the invention based on a photographic view of a prototype of an alternator for generating kinetic energy, wherein the in the 2 The functional element, which is again shown separately, comprises a rotatably mounted drive wheel, on the circumference of which a plurality of actuators made of a two-way shape memory polymer is arranged. How from the 3A and 3B As can be seen, the two-way shape memory polymer of the actuators is programmed in such a way that the actuators switch between a first shape (cf 3A ) and a second form (cf. the 3B ) can be switched back and forth reversibly. The two-way shape memory polymer of the actuators has on the one hand a first switching temperature at which it is converted from its second form into its first form, and on the other hand one of its first switching temperature temperature different, second switching temperature at which it is converted from its first form into its second form. In addition, the two-way shape memory polymer of the actuators is mixed with a medium that absorbs electromagnetic radiation, for example in the sunlight spectrum, e.g. in the form of a filler of the type described above, in order in the event of exposure of the two-way shape memory polymer to electromagnetic radiation in the corresponding wavelength range , like this in the 1 can be seen by means of a lamp to ensure accelerated heating of the irradiated actuators to their respective higher switching temperature.

How to continue in particular 3A and 3B can be seen, the actuators arranged on the circumference of a drive wheel have a first shape ( 3A ) and a second form ( 3B ) with different geometric dimensions with a radial extension component of the drive wheel, the actuators in their second form ( 3A ) protrude further in the radial direction of the drive wheel than in their first form ( 3B ). If the functional element is now from one side with electromagnetic radiation, for example with the light in the 1 lamp shown, is irradiated, the actuators that are directly exposed to the electromagnetic radiation (here those that face the lamp) heat up faster than the actuators that are less exposed to the electromagnetic radiation (here those that face away from the lamp), so that the former due to their the medium absorbing electromagnetic radiation can be brought more quickly to its higher (second) switching temperature, in which it changes from its first form ( 3A ) into its second form ( 3B ) can be switched. Due to the fact that the actuators are now in the second form on the side of the drive wheel facing the electromagnetic radiation source, which due to their larger radial projection cause a greater torque on the drive wheel than the actuators on the opposite side of the drive wheel, which are still in their first form , the drive wheel is now set in rotation gravimetrically.

With continued rotation of the drive wheel, those in the second form ( 3B ) located actuators of the electromagnetic radiation source - here in the form of the lamp according to 1 - Opposite side of the impeller, on which its two-way shape memory polymer is cooled to its lower (first) switching temperature, so that the actuators from their second form ( 3B ) back to their first form ( 3A ) can be switched. Due to the fact that the actuators are now in the first form on the side of the drive wheel facing away from the electromagnetic radiation source, which, due to their smaller radial projection, cause a smaller torque on the drive wheel than the actuators on the opposite side of the drive wheel, which are still in their second form , the impeller is rotated gravimetrically as described above. Furthermore, on the side of the drive wheel facing away from the electromagnetic radiation source, a shield (not shown in the figures), for example in the form of a shading device, and/or a cooling device, for example in the form of a water reservoir, can be provided in order to ensure faster cooling of the in the second form ( 3B ) located actuators to their lower (first) switching temperature so that they go into their first form ( 3A ) before they are again exposed to the electromagnetic radiation of the lamp as the drive wheel rotates further, whereupon they quickly heat up again to their higher (second) switching temperature with the help of the electromagnetic radiation-absorbing medium in order to switch to their second form ( 3B ) to be switched.

In the 4A and 4B is another embodiment of an actuator reproduced photographically, which are also used as actuators for the drive wheel 1 and 2 are suitable, with the actuators in the shape ( 4B ) also have a larger radial projection over the circumference of the drive wheel than in their first form ( 4A ), in which they are roughly spirally coiled, whereas in their second form ( 4B ) elongated or at least partially unrolled.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• WO 2020/228920 A1 [0007]
• DE 102020001380 A1 [0008]
• DE 102020000159 A1 [0009]
• CN 105936747A [0021]
• DE 102018003274 A1 [0021]

Claims (12)

Functional element with at least one first actuator, which contains at least one first two-way shape memory polymer or is essentially formed entirely from it, which is programmed in such a way that the first actuator can be reversibly switched back and forth between a first shape and a second shape, the at least a first two-way shape memory polymer of the first actuator at least - a first switching temperature at which it is converted from its second shape into its first shape, and - a second switching temperature different from its first switching temperature at which it changes from its first shape into its second Shape is transferred, having, characterized in that the functional element has at least one second actuator, which contains at least one second two-way shape memory polymer or is essentially formed entirely from it, which is programmed in such a way that the second actuator between a first shape and a second shape can be reversibly switched back and forth, the at least one second two-way shape memory polymer of the second actuator having - at least one first switching temperature at which it is converted from its second shape into the first shape, and - a second switching temperature that is different from its first switching temperature, in which it is transformed from its first shape into its second shape, wherein the first two-way shape memory polymer of the first actuator and/or the second two-way shape memory polymer of the second actuator is provided with an electromagnetic radiation absorbing or reflecting medium in order to in case to provide accelerated or decelerated heating upon exposure of the two-way shape memory polymer to electromagnetic radiation. functional element after claim 1 , characterized in that the first two-way shape memory polymer of the first actuator is - a different two-way shape memory polymer than the second two-way shape memory polymer of the second actuator, or - the same two-way shape memory polymer as the second two-way shape memory polymer of the second actuator acts. functional element after claim 1 or 2 , characterized in that - all actuators are provided with the electromagnetic radiation absorbing medium; or - only at least one of the actuators is provided with the medium absorbing electromagnetic radiation; or - at least two actuators are provided with different media absorbing electromagnetic radiation and/or with different proportions of the medium absorbing electromagnetic radiation. Functional element according to one of Claims 1 until 3 , characterized in that the electromagnetic radiation absorbing or reflecting medium absorbs or reflects electromagnetic radiation in the electromagnetic spectrum of the sun, in particular in the visible spectrum. Functional element according to one of Claims 1 until 4 , characterized in that the electromagnetic radiation absorbing or reflecting medium - is applied in the form of a coating to the two-way shape memory polymer of the actuator and/or - is introduced into the two-way shape memory polymer of the actuator in the form of a filler. Functional element according to one of Claims 1 until 5 , characterized in that at least one of the actuators - in its first form has at least one through-channel with a first cross-section and in its second form has a through-channel with a second cross-section different from the first cross-section or has no through-channel; and/or - in its first form, has a different length, height and/or width than in its second form; and/or - in its first shape, has a different bending and/or torsion than a second shape. Functional element according to one of Claims 1 until 6 , characterized in that the two-way shape memory polymer is at least one of the actuators, in particular a thermoplastic, polyester or polyether urethane elastomer. Functional element according to one of Claims 1 until 7 , characterized in that it further comprises at least one mirror and/or at least one screen, which is designed to focus ambient electromagnetic radiation onto at least one of the actuators. Functional element according to one of Claims 1 until 8th , characterized in that it further comprises - at least one shield, which is designed for at least partial shielding of ambient electromagnetic radiation on at least one of the actuators; and/or at least one cooling device, which is designed to cool at least one of the actuators. Functional element according to one of Claims 1 until 9 , characterized in that it has a plurality of substantially parallel actuators, which have a first shape and a second shape with different geometric dimensions and are designed as control elements for windows, doors or shading devices. Functional element according to one of Claims 1 until 9 , characterized in that it has a plurality of essentially parallel actuators, which have a first shape with at least one through-channel and a second shape with at least one through-channel of different cross section or no through-channel and are designed as a valve unit for fluids. Functional element according to one of Claims 1 until 9 , characterized in that it comprises a plurality of actuators arranged on the periphery of a drive wheel, which have a first shape and a second shape with different geometrical dimensions with a radial extension component of the drive wheel, in order to set the drive wheel in rotation gravimetrically.

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