DE102022122216A1 - Polymer molding and method for producing it - Google Patents

Abstract

The invention relates to a dual stimuli-responsive polymer molding comprising at least 2 different polymers, wherein the first polymer has an orientation of the polymeric chains in at least one orientation direction and a degree of crystallization of less than 10% of its maximum degree of crystallization and a glass transition temperature TG1 and wherein the first Polymer can have a crystallization temperature depending on the cooling rate and wherein crystallization does not occur at a cooling rate of >X K/min and wherein cold crystallization of the first polymer takes place at a cooling rate between 0 and TG1 loses the orientation of the polymeric chains through relaxation and where TKS1 is at least 40 K larger than TG1 and where in the first polymer the relaxation of the orientation is a faster process than cold crystallization and where cold crystallization and relaxation of the orientation in the orientation direction in the first polymer a reduction in the volume and wherein the heat resistance temperature THDT2 of the second polymer is a maximum of 10 K below the start temperature of the cold crystallization TKS1 of the first polymer and wherein the second polymer either has no start temperature of the cold crystallization or the start temperature of the cold crystallization TKS2 of the second polymer is at least 20 K above of TKS1 and where the second polymer does not experience a reduction in volume during the subsequent heating and where .

Description

The invention involves a molded part comprising at least two different polymers, a method for additive manufacturing of the molded part and the use of the molded part as an adaptable, assembly-free mechanism.

US 2015/158 244 A1 claims a 3D-printed molded part that can change its shape using a downstream external stimulus and is therefore adaptable. The effect is based on the different swelling behavior of the polymers used, especially in the event that a polymer undergoes a change in state from glass-like to plastically deformable during swelling.

The DE 10 2019 007 939 A1 is about a so-called 4D printing process for producing polymer molded parts from thermoplastic polymers with shape memory properties. During printing, the polymer in question is not completely melted, so that hard and soft segments are present next to each other. By rapidly cooling below the glass transition temperature, the soft segments solidify. During a subsequent heat treatment step at the so-called “switching temperature”, the soft segments return to the amorphous state and no longer offer any resistance to the restoring force generated by the hard segments acting as network points. The molded part returns to its “programmed” shape.

In the conference paper “Additive manufacturing of precise non-assembly mechanisms”, IFToMM-D-A-CH conference published on February 22, 2022, DOI:10.17185/duepuplico/75421, 3D printed assembly-free mechanisms made of two different polymers are described. The assembly-free mechanisms can be adjusted through a one-time heat treatment to eliminate bearing play. With further use, the bearing play occurs again and cannot be remedied.

The disadvantage of the previously known molded parts that can be adjusted by a subsequent stimulus is that an adjustment can only be made between two states and therefore only once in the desired direction to achieve the programmed shape.

It is therefore the object of the invention to provide a polymer molded part which can undergo a further adjustment of its dimension in order to achieve the programmed shape due to a new different external stimulus.

und eine Glasübergangstemperatur T_G1 aufweist und wobei das erste Polymer abhängig von der Abkühlrate eine Kristallisationstemperatur aufweisen kann und wobei die Kristallisation bei einer Abkühlrate von ≥ X K/min unterbleibt und wobei eine Kaltkristallisation des ersten Polymers bei einer Abkühlrate zwischen 0 und X K/min ab einer Starttemperatur T_KS1 stattfindet und wobei das erste Polymer oberhalb von T_G1 die Orientierung der polymeren Ketten durch Relaxation verliert und wobei T_KS1 mindestens 40 K größer ist als T_G1 und wobei beim ersten Polymer die Relaxation der Orientierung ein schneller ablaufender Prozess ist als die Kaltkristallisation und wobei Kaltkristallisation und Relaxation der Orientierung in Orientierungsrichtung bei dem ersten Polymer mit einer Verkleinerung des Volumens einhergehen und wobei die Wärmeformbeständigkeitstemperatur T_HDT2 des zweiten Polymers maximal 10 K unterhalb der Starttemperatur der Kaltkristallisation T_KS1 des ersten Polymers liegt und wobei das zweite Polymer entweder keine Starttemperatur der Kaltkristallisation aufweist oder die Starttemperatur der Kaltkristallisation T_KS2 des zweiten Polymers mindestens 20 K oberhalb von T_KS1 liegt und wobei das zweite Polymer bei vorangegangener Abkühlung keine Verkleinerung des Volumens während der folgenden Aufheizung erfährt und wobei X Werte zwischen 500 und 4 annimmt.The object of the invention is achieved by a dual stimuli-responsive polymer molding comprising at least 2 different polymers, the first polymer having an orientation of the polymeric chains in at least one orientation direction and a degree of crystallization of less than 10% of its maximum degree of crystallization $\left(\frac{H_{KS}}{H_{ScHmel\mathrm{e.g}}}\le 0.9\right)$

and has a glass transition temperature T _G1 and wherein the first polymer can have a crystallization temperature depending on the cooling rate and wherein crystallization occurs at a cooling rate of ≥ XK/min and wherein cold crystallization of the first polymer occurs at a cooling rate between 0 and XK/min from one Starting temperature T _KS1 takes place and where the first polymer loses the orientation of the polymer chains through relaxation above T _G1 and where T _KS1 is at least 40 K greater than T _G1 and where in the first polymer the relaxation of the orientation is a faster process than cold crystallization and wherein cold crystallization and relaxation of the orientation in the orientation direction in the first polymer are accompanied by a reduction in the volume and wherein the heat deflection temperature T _HDT2 of the second polymer is a maximum of 10 K below the starting temperature of the cold crystallization T _KS1 of the first polymer and wherein the second polymer either has no starting temperature of the cold crystallization or the starting temperature of the cold crystallization T _KS2 of the second polymer is at least 20 K above T _KS1 and the second polymer does not experience any reduction in volume during the previous cooling and where X assumes values between 500 and 4.

In a preferred embodiment of the invention, the first polymer is polylactide (PLA) or a compound of this polymer and the second polymer is selected from the group of acrylonitrile-styrene-acrylate (ASA), acrylonitrile-butadiene-styrene copolymer (ABS), methyl methacrylate-acrylonitrile -Butadiene-styrene copolymer (MABS) Styrene-acrylonitrile copolymer (SAN), polystyrene (PS), high density polyethylene (PE-HD), polypropylene (PP), polyamides (PA), polyethylene terephthalate (PET), polybutethylene terephthalate (PBT ), polycarbonate (PC), polyoxymethylene (POM) and/or mixtures or compounds of these polymers.

In an alternative embodiment of the invention, the first polymer is polyethylene terephthalate (PET) or a compound of this polymer and the second polymer is selected from the group polyamides (PA), polycarbonate (PC), polyethylene terephthalate (PBT), polyoxymethylene (POM), polyphenylene sulfide (PPS ), polysulfone (PSU), polyetherimide (PEI), polyamidimide (PAI), polyethersulfone (PESU) and / or mixtures or compounds of these polymers.

In an alternative embodiment of the invention, the first polymer is polycyclohexylenedimethylene terephthalate (PCT) and/or a copolyester and/or compounds of this polymer and the second polymer is selected from the group of polyamides (PA), polyoxymethylene (POM), polyphenylene sulfide (PPS), polysulfone ( PSU), polyetherimide (PEI), polyamidimide (PAI), polyethersulfone (PESU) and/or mixtures or compounds of these polymers.

und/oder Compounds dieses Polymers und das zweite Polymer ausgewählt aus der Gruppe Polyamide (PA), Polyoxymethylen (POM), Polyphenylensulfid (PPS), Polysulfon (PSU), Polyetherimid (PEI), Polyamidimid (PAI), Polyethersulfon (PESU) und/oder Mischungen oder Compounds dieser Polymere.In a preferred embodiment, the first polymer is a copolyester of hexylenedimethylene terephthalate and hexylenedimethylene isophthalate (PCTA) with the following formula:

and/or compounds of this polymer and the second polymer selected from the group polyamides (PA), polyoxymethylene (POM), polyphenylene sulfide (PPS), polysulfone (PSU), polyetherimide (PEI), polyamideimide (PAI), polyethersulfone (PESU) and/or or mixtures or compounds of these polymers.

In a further alternative embodiment of the invention, the first polymer is selected from the group of polyaryletherketone (PAEK), polyetherketone (PEK), polyetheretherketone (PEEK), poly(etherketoneketone) (PEKK), poly(etheretherketoneketone) (PEEKK), and/or poly (etherketone-etherketoneketone) (PEKEKK) and mixtures or compounds of these polymers and the second polymer selected from the group polysulfone (PSU), polyetherimide (PEI), polyethersulfone (PESU), polyamideimide (PAI) and / or mixtures or compounds of these polymers.

Table 1 shows an overview of the embodiments of the invention and typical characteristics for the polymers. Table 1: Embodiments of the invention Polymer 1 Polymer 2 Surname T _G [°C] T _KS [°C] Surname T _G [°C] T _KS [°C] T _HDT [°C] 0.45 MPa PLA 45-65 90-105 SECTION 95-105 - 70 - 125 MABS 100-110 - 104-106 ASA 95 - 105 - 80 - 95 SAN 95-110 - 105-115 PE-HD -130--100 Unknown 60 - 90 PP -20 - 20 Unknown 75 - 120 P.S 80 - 105 - 75-110 P.A 40-90 Unknown 60 - 240 PET 70 - 85 135-150 75-115 PBT 40 - 60 Unknown 115-150 PC 140 - 150 - 120 - 130 POM -75 - -60 Unknown 145 - 170 PET 70 - 85 135 - 150 P.A 40 - 90 Unknown 60 - 240 PC 140 - 150 - 120 - 130 PBT 40 - 60 Unknown 115-150 POM -75 - -60 Unknown 145 - 170 PPS 85 - 100 Unknown 140 - 160 PSU 185-190 - 175-185 P.E.I 215-230 - Unknown PAI 215-200 - Unknown PESU 225 - 230 - Unknown PCTA 90-100 160 P.A 40 - 90 Unknown 60 - 240 POM -75 - -60 Unknown 145 - 170 PPS 85 - 100 Unknown 140 - 160 PSU 185-190 - 175-185 P.E.I 215-230 - Unknown PAI 215-200 - Unknown PESU 225 - 230 - Unknown PEAK family 145-175 165 - 190 PSU 185-190 - 175-185 P.E.I 215-230 - Unknown PESU 225 - 230 - Unknown PAI 215-200 - Unknown

1. i. Auswahl zweier Polymere anhand des Vorhandenseins folgender Kriterien:
   1. a. Vorliegen je eines Temperaturbereiches, in dem ein zersetzungsfreies Schmelzen oder Plastifizieren des ersten Polymers und ein Schmelzen oder Plastifizieren des zweiten Polymers möglich ist;
   2. b. Vorhandensein eines Glasübergangs beim ersten Polymer und beim zweiten Polymer mit den Glasübergangstemperaturen T_G1 und T_G2;
   3. c. Teilkristallisierbarkeit des ersten Polymers oberhalb von T_G1;
   4. d. Unterdrückung der Kristallisation beim ersten Polymer bei einer Abkühlrate von ≥ X K/min ;
   5. e. Beginn der Kaltkristallisation des ersten Polymers bei einer Kaltkristallisationsstarttemperatur T_KS1;
   6. f. Orientierbarkeit der polymeren Ketten des ersten Polymers in mindestens einer Richtung während der additiven Fertigung;
   7. g. Relaxation der Orientierung in Orientierungsrichtung beim ersten Polymer oberhalb von T_G1;
   8. h. Relaxation der Orientierung in Orientierungsrichtung schneller als Kristallisation beim ersten Polymer;
   9. i. Relaxation der Orientierung in Orientierungsrichtung beim ersten Polymer wird durch die Abkühlung mit einer Abkühlrate von ≥X K/min zumindest teilweise unterbunden;
   10. j. Kaltkristallisationsstarttemperatur T_KS1 des ersten Polymers ist um mindestens 40 K höher als die Glasübergangstemperatur T_G1;
   11. k. Kristallisation und Relaxation der Orientierung in Orientierungsrichtung bei dem ersten Polymer gehen mit einer Kontraktion in mindestens einer Richtung einher;
   12. l. Wärmeformbeständigkeitstemperatur des zweiten Polymers T_HDT2 liegt maximal 10 K unterhalb von T_KS1;
   13. m. Beim zweiten Polymer ist entweder keine Kaltkristallisation möglich oder die Starttemperatur der Kaltkristallisation des zweiten Polymers T_KS2 nach vorheriger Abkühlung mit einer Abkühlrate von ≥X K/min liegt mindestens 20 K oberhalb von T_KS1;
2. ii. Fördern der im Schritt i. ausgewählten Polymere zu einer beheizten Düse;
3. iii. Passieren der Düse bei der Temperatur T_Ext dabei Plastifizieren und Orientieren der im Schritt i. ausgewählten Polymere durch die Temperatur T_Ext und Scherung während der Förderung;
4. iv. Schichtweises Ablegen und weiteres Orientieren senkrecht zur Richtung der Orientierung der in Schritt iii plastifizierten und orientierten Polymere auf ein Substrat mit einer Abkühlrate ≥ X K/min,

wobei T_Ext > T_G für amorphe thermoplastische Polymere und wobei T_Ext > T_Schmelz für teilkristalline thermoplastische Polymere und wobei die Abkühlrate X K/min eine Abkühlung von T_Ext1 auf T_G1 ermöglicht, die schneller ist als die Relaxationszeit der Orientierung des Polymers 1 t_Relax1.Also according to the invention is the process for producing the polymer molding according to the invention comprising the following steps:

1. i. Selection of two polymers based on the presence of the following criteria:
   1. a. Presence of a temperature range in which decomposition-free melting or plasticization of the first polymer and melting or plasticization of the second polymer are possible;
   2. b. Presence of a glass transition in the first polymer and in the second polymer with the glass transition temperatures T _G1 and T _G2 ;
   3. c. Partial crystallizability of the first polymer above T _G1 ;
   4. d. Suppression of crystallization for the first polymer at a cooling rate of ≥ XK/min;
   5. e. Start of cold crystallization of the first polymer at a cold crystallization start temperature T _KS1 ;
   6. f. Orientability of the polymeric chains of the first polymer in at least one direction during additive manufacturing;
   7. G. Relaxation of the orientation in the orientation direction for the first polymer above T _G1 ;
   8. H. Relaxation of the orientation in the orientation direction faster than crystallization for the first polymer;
   9. i. Relaxation of the orientation in the orientation direction of the first polymer is at least partially prevented by cooling at a cooling rate of ≥XK/min;
   10. j. Cold crystallization start temperature T _KS1 of the first polymer is at least 40 K higher than the glass transition temperature T _G1 ;
   11. k. Crystallization and relaxation of the orientation in the orientation direction in the first polymer are accompanied by a contraction in at least one direction;
   12. l. Heat resistance temperature of the second polymer T _HDT2 is a maximum of 10 K below T _KS1 ;
   13. m. With the second polymer, either cold crystallization is not possible or the starting temperature of the cold crystallization of the second polymer T _KS2 after previous cooling with a cooling rate of ≥XK/min is at least 20 K above T _KS1 ;
2. ii. Promote the in step i. selected polymers to a heated nozzle;
3. iii. Passing through the nozzle at the temperature T _Ext while plasticizing and orienting the in step i. selected polymers by the temperature T _Ext and shear during conveying;
4. iv. Deposition in layers and further orientation perpendicular to the direction of orientation of the polymers plasticized and oriented in step iii onto a substrate with a cooling rate ≥ XK / min,

where T _Ext > T _G for amorphous thermoplastic polymers and where T _Ext > T _melt for partially crystalline thermoplastic polymers and where the cooling rate XK/min enables cooling from T _Ext1 to T _G1 which is faster than the relaxation time of the orientation of the polymer 1 t _Relax1 .

shows a schematic sketch of the shear during steps iii. and iv. First, the polymer melt is sheared through the die, then the side of the die moves over the deposited strand, shearing the melt strand. The melt is cooled directly behind the nozzle. Depending on the material and printing strategy, the polymer melt can be sheared sufficiently to orient the molecules during printing. Due to rapid cooling behind the nozzle, the time until the glass transition temperature is reached can be shorter than the relaxation time for some polymers. In this case, the molecular orientations in the printed parts are frozen.

In a preferred embodiment of the method, the information about whether the criteria correspond to i. a., b., c., d., e., i., j., m. are achieved using differential scanning calorimetry (DSC).

In a further preferred embodiment of the method, the information about whether the criteria i. f., g., h., k. fulfilled are determined using isothermal dilation measurements.

In a further embodiment of the method, the information about whether criterion i. l. is met, determined by heat resistance measurements according to DIN EN ISO 75 with a sample tension of 0.45 MPa or according to ASTM D648 with a sample tension of 66 psi. Alternatively, this value can be found on the polymer data sheet.

The information corresponding to step i a., b., c., d., e., j., m. can be obtained by the person skilled in the art, for example, using measurements using differential scanning calorimetry (DSC). shows an exemplary DSC curve from which the information i a., b., c., d., e., j., m. can be taken.

ia

The existence of a temperature range in which decomposition-free melting or plasticization of the first polymer and melting or plasticization of the second polymer is possible is shown in the DSC curves by the fact that a baseline can be seen at the corresponding temperatures. If endothermic or exothermic decomposition is present, the curve will deviate from the baseline.

i.b.

The glass transition can be observed as a step in the baseline of the measurement curves. The mean value of the extrapolated line corresponds to the glass transition temperature.

i.c.

The partial crystallizability of the first polymer above T _G1 is indicated by an endothermic melting range.

i.d.

The suppression of the crystallization of the polymer at a cooling rate of ≥

i.e.

The start of the cold crystallization of the first polymer at a cold crystallization start temperature T _KS1 can be determined after evaluating the onset of the cold crystallization region after cooling with XK/min. shows the evaluation of the onset as the intersection of the tangent of the baseline and the tangent of the crystallization peak at the turning point.

There must be a sufficiently large temperature window of at least 40 K between the glass transition temperature T _G1 and the start of cold crystallization at T _KS1 of the first polymer in order to separate orientation relaxation and cold crystallization from one another. This should be measured at the lowest possible heating rates (close to equilibrium), since the start of cold crystallization is shifted to higher temperatures more strongly as the heating rate increases than the glass transition. However, the heating rate must remain so high that the glass transition can still be determined.

i.j.

The DSC curve can also be used to determine whether the cold crystallization start temperature T _KS1 of the first polymer is at least 40 K higher than the glass transition temperature T _G1 .

in the.

By comparing the DSC curves of the first polymer with those of the second polymer, it can be determined whether the starting temperature of the cold crystallization of the second polymer T _KS2 is at least 20 K above T _KS1 .

The test for the criteria if, g., h., k. can be carried out as follows using isothermal dilation measurements. The isothermal process progress as a function of time can be used as a relevant comparison variable. shows the time dependence of isothermal dilation. For the process progress P(t) of the orientation relaxation, the dilatation D(t) perpendicular to the orientation direction (here Z direction) can be used. Since only orientational relaxation can cause irreversible expansion during the heat treatment, the maximum of the dilatation can be approximately considered as the end of the process D _max . The process progress depending on the time t can be determined as follows: $$P\left(t\right)=\frac{D\left(t\right)}{D_{max}}$$

i.f. and i.g.

The orientability of the polymeric chains of the first polymer in at least one direction during additive manufacturing and the relaxation of the orientation in the orientation direction for the first polymer above T _G1 can be determined by evaluating the contraction of one after steps ii. to iv. produced sample in the orientation direction (here X & Y direction) with simultaneous expansion orthogonal to the orientation direction (here Z direction) at the desired temperature above T _G. This connection is also refer to.

i.e.

• Es wird die Dauer der Kontraktion einer orientierungsfreien mit X K/min abgekühlten Probe bei gewünschter Temperatur (siehe ) sowie die Messung orthogonal zur Orientierungsrichtung einer entsprechend den Schritten ii. bis iv. hergestellten Probe bei gewünschter Temperatur (siehe ) gemessen. Es erfolgt ein Vergleich der Effektfortschritte in Abhängigkeit der Zeit. Der Effektfortschritt der Kaltkristallisation P(t)_KS kann aus erster Messung direkt entnommen werden. Der Effektfortschritt der Orientierungsrelaxation kann durch Subtraktion erster Messung von der zweiten erhalten werden.

$$P{\left(t\right)}_{KS}=\frac{D{\left(t\right)}_{KS}}{D_{min}}$$

$$P{\left(t\right)}_{Relax}=\frac{D\left(t\right)-D{\left(t\right)}_{KS}}{D_{max,Relax}}$$

The determination of whether the relaxation of the orientation in the orientation direction is faster than the crystallization of the first polymer is done as follows:

• The duration of the contraction of an orientation-free sample cooled with XK/min at the desired temperature (see ) as well as the measurement orthogonal to the orientation direction according to steps ii. to iv. prepared sample at the desired temperature (see ) measured. A comparison is made of the effect progress depending on time. The progress of the cold crystallization effect P(t) _KS can be taken directly from the first measurement. The effect progression of the orientation relaxation can be obtained by subtracting the first measurement from the second.

$$P{\left(t\right)}_{KS}=\frac{D{\left(t\right)}_{KS}}{D_{min}}$$

$$P{\left(t\right)}_{Relax}=\frac{D\left(t\right)-D{\left(t\right)}_{KS}}{D_{max,Relax}}$$

Alternatively, a two-stage isothermal dilation measurement can be carried out in accordance with steps ii. to iv. The sample produced must be carried out perpendicular to the orientation direction (here Z direction). This connection is in shown. The first isothermal stage is at a temperature between T _G1 and 25 K below T _KS1 , preferably at the temperature of the first heat treatment _{T W1} , and the second stage above T _KS1 - 25 K, preferably at the temperature of the second heat treatment T _W2 , carried out. The first isothermal stage is maintained until the maximum expansion is reached. The mixture is then heated to the second isothermal stage at a moderate heating rate (here 2 K/min). If a contraction occurs in this second isothermal stage, there must still be cold crystallization potential in the component, which leads to this contraction. In order to be able to determine the process progress of the cold crystallization when the relaxation is complete with this method, another sample must be measured near equilibrium in the DSC after the first isothermal stage has been completed. The cold crystallization enthalpy H _KS and the amount of melting enthalpy |H _melt | are then calculated compared. The following applies: $$P_{KS}=1-\frac{H_{KS}}{\left|H_{ScHmel\mathrm{e.g}}\right|}$$

i. k.

By evaluating the direction-dependent dilation behavior, it can be determined whether the crystallization and relaxation of the orientation in the orientation direction in the first polymer are accompanied by a contraction in at least one direction.

i.i.

• In einer gescherten Schmelze finden sowohl makro-brownsche Bewegungen als auch Orientierungsprozesse gleichzeitig statt. Die Brownschen Bewegungen führen mit der Zeit zu einer Relaxation der eingebrachten Orientierungen. Ist der Orientierungsprozess schneller als der Relaxationsprozess, orientieren sich die Moleküle in der Polymerschmelze. Sobald die Scherung gestoppt wird, finden keine Orientierungsprozesse mehr statt, aber die Brownschen Bewegungen bleiben bestehen, solange die Temperatur über der Glasübergangstemperatur liegt. Daher werden die Orientierungen im Polymer mit der Zeit sukzessive abgebaut. Die für diesen Prozess erforderliche Zeit wird als Relaxationszeit bezeichnet, die empfindlich von der Temperatur abhängt.

The person skilled in the art obtains the information as to whether relaxation of the orientation in the orientation direction of the first polymer is at least partially prevented by cooling at a cooling rate of ≥XK/min and thus criterion ii is fulfilled as follows:

• In a sheared melt, both macro-Brownian motions and orientation processes occur simultaneously. Over time, the Brownian movements lead to a relaxation of the introduced orientations. If the orientation process is faster than the relaxation process, the molecules in the polymer melt orient themselves. As soon as the shearing is stopped, none are found Orientation processes take place more, but the Brownian motions persist as long as the temperature is above the glass transition temperature. Therefore, the orientations in the polymer are gradually broken down over time. The time required for this process is called the relaxation time, which depends sensitively on the temperature.

mit
t_Relax: Relaxationszeit
T_Ext: Extrusionstemperatur
T_G: Glasübergangstemperatur
v_K: AbkühlgeschwindigkeitIn order to freeze the orientations, the following applies: $$t_{Relax}>>\left(T_{Ext}-T_G\right)/v_K$$

with
t _Relax : relaxation time
T _Ext : extrusion temperature
T _G : glass transition temperature
v _K : cooling rate

1. 1. Es wird ein Prüfkörper (Beispielsweise Würfel) mit entsprechenden Parametern ii bis iv gedruckt anschließend die Dilatation in Abhängigkeit der Zeit und Temperatur gemessen. Ist eine irreversible Expansion senkrecht zur Orientierungsrichtung (Schichtungsebene) vorhanden, waren vor der Messung Orientierungen im Bauteil vorhanden, welche während der Messung relaxiert sind. (vgl. -Richtung)
2. 2. In einem Rotationsrheometer-kann die Polymerschmelze auf T_Ext erhitzt und dann entsprechend den Scherraten im Druckprozess konstant geschert werden. Anschließend wird die Scherung des Polymers gestoppt und im selben Zug mit v_K unter T_G abgekühlt. Der Abbau des Drehmoments entspricht dabei der Relaxation.

Determining whether this is possible can happen in several ways:

1. 1. A test specimen (e.g. cube) with corresponding parameters ii to iv is printed and then the dilatation is measured as a function of time and temperature. If there is an irreversible expansion perpendicular to the orientation direction (layering plane), there were orientations in the component before the measurement that relaxed during the measurement. (see. -Direction)
2. 2. In a rotational rheometer - the polymer melt can be heated to T _Ext and then constantly sheared according to the shear rates in the printing process. The shearing of the polymer is then stopped and at the same time it is cooled with v _K below T _G. The reduction in torque corresponds to relaxation.

If there is still residual torque when T _G is reached, orientations in the component are still frozen. The connection between temperature, relaxation and freezing of orientations is in to see.

The information according to step i l. can be determined using heat resistance measurements according to DIN EN ISO 75 with a sample tension of 0.45 MPa or according to ASTM D648 with a sample tension of 66 psi. Alternatively, this value can be found on the polymer data sheet.

The effects of orientation relaxation and cold crystallization must occur at different rates in the material during heat treatment. This means that there is a heat treatment temperature at which orientation relaxation already takes place, but cold crystallization is still prevented. The connection is in to recognize. In order to have sufficient contraction potential through cold crystallization after the complete relaxation of the orientations, the process progress of the cold crystallization at the time of completion of the orientation relaxation should not exceed a value of 25%.

Through a subsequent first heat treatment (first external stimulus) at a temperature T _W1 above T _G1 and 25 K below T _KS1 , the play of the polymer molded part manufactured using the method according to the invention can be adjusted to a precise bearing gap.

If the bearing gap increases again as a result of the use of the polymer molding, the bearing gap can surprisingly be increased again by a renewed heat treatment (second external stimulus) at a temperature T _W2 in the range between T _KS1 - 25 K (lower limit) and T _HDT2 (upper limit) can be set.

Also according to the invention, the polymer molding according to the invention is used as a kinematic pair in a multi-body system.

The polymer molding according to the invention is preferably used as a kinematic pair in a multi-body system, the multi-body system being an assembly-free mechanism.

Non-assembly mechanisms are movable mechanisms that can be manufactured without assembly in a single production step nen. With conventional manufacturing technologies such as injection molding, only assembly-free mechanisms in the form of solid-state joints are currently possible. Additive manufacturing processes make it possible to produce assembly-free mechanisms with joints made of kinematic pairs.

shows an assembly-free mechanism with a joint made of a kinematic pair.

Since the two processes of orientation relaxation and cold crystallization can be separated in the first polymer, it is possible to use it twice in the life cycle of assembly-free mechanisms to compensate for bearing play.

The play of the assembly-free mechanism can initially be adjusted via orientation relaxation with a first external stimulus at the temperature T _W1 .

After some wear on the mechanism, the remaining crystallization potential can be exploited by giving the mechanism another heat treatment at the temperature T _W2 (second external stimulus). The shrinkage induced by cold crystallization is then used to compensate for the wear-related play.

This opens up completely new possibilities for extending the lifespan of such a mechanism - equipped with a type of “induced self-healing” - and thus making it more sustainable.

To investigate the performance of an assembly-free mechanism with joints made of kinematic pairs, these can be assembled into a Watt's link. An example of such a Watt's handlebar can be found in . A Watt mechanism was used with four of the previously discussed kinematic pair joints.

Without limiting the generality of the teaching, the production and use of a polymer molding according to the invention will be described below.

• Typ DSC: Polyma 214 Netsch Gerätebau GmbH
• Typ TMA: TMA 402 Netzsch Gerätebau GmbH

The following device types are used:

• Type DSC: Polyma 214 Netsch Gerätebau GmbH
• Type TMA: TMA 402 Netzsch Gerätebau GmbH

1. 1. Das Polymer wird gleichgewichtsnah in der DSC bis in die Schmelze aufgeheizt und die Kaltkristallisationsenthalpie H_KS (exothermer Prozess) und die Schmelzenthalpie H_Schmelz (endothermer Prozess) evaluiert. Ist |H_KS| < |H_Schmelz| ist ein Teil des Polymers in der vorangegangenen Abkühlung kristallisiert. Somit erhalten wir Aufschluss über den Kristallisationsgrad nach der vorangegangenen Abkühlung
2. 2. Anschließend wird die Polymerschmelze mit einer definierten Abkühlgeschwindigkeit heruntergekühlt
3. 3. Schritt 1 wird erneut wiederholt
4. 4. Schritt 2 wird mit einer andern Abkühlgeschwindigkeit wiederholt.

First polymer: Polylactide (PLA) from DAS FILAMENT

1. 1. The polymer is heated to near equilibrium in the DSC down to the melt and the cold crystallization enthalpy H _KS (exothermic process) and the melting enthalpy H _melt (endothermic process) are evaluated. Is |H _KS | < |H _enamel | part of the polymer has crystallized during the previous cooling. This gives us information about the degree of crystallization after the previous cooling
2. 2. The polymer melt is then cooled down at a defined cooling rate
3. 3. Step 1 is repeated again
4. 4. Step 2 is repeated with a different cooling rate.

gilt. Diese Temperatur ist als Schwellwert für die Abkühlgeschwindigkeit zu betrachten (im Fall von PLA bei 6 K/min). Diese Abkühlrate muss im späteren Druckprozess realisierbar sein (Kriterium i.d.) zeigt die DSC-Kurven der Aufheizung von PLA bei verschiedenen vorangegangenen Kühlraten. Es zeigt sich an der Basisline, dass ein zersetzungsfreies Schmelzen oder Plastifizieren des PLA möglich ist (Kriterium i.a. ist erfüllt). Die Teilkristallisierbarkeit des PLA oberhalb von T_G1 wird durch einen endothermen Schmelzbereich angezeigt (Kriterium i.c. ist erfüllt).This routine is repeated systematically until the cooling rate has been determined $\frac{H_{KS}}{H_{ScHmel\mathrm{e.g}}}\le 0.9$

applies. This temperature should be considered as a threshold value for the cooling rate (in the case of PLA at 6 K/min). This cooling rate must be feasible in the later printing process (criterion id) shows the DSC curves of heating of PLA at different previous cooling rates. The baseline shows that decomposition-free melting or plasticization of the PLA is possible (criterion ia is met). The partial crystallizability of the PLA above T _G1 is indicated by an endothermic melting range (criterion ic is met).

There must be a sufficiently large temperature window of at least 40 K (step ij) between the glass transition temperature and the start of cold crystallization in order to separate orientation relaxation and cold crystallization. This should be measured at the lowest possible heating rates (close to equilibrium), since the start of cold crystallization is shifted to higher temperatures more strongly as the heating rate increases than the glass transition. However, the heating rate must remain so high that the glass transition still occurs can be determined. In the DSC curve of PLA is shown, the glass transition T _G (center) of the investigated PLA can be found at 58 °C (criterion ib), followed by the onset of cold crystallization T _KS at 101 °C (criterion ie). The enthalpy of cold crystallization H _KS at approx. 23.5 J/g, minus minor inaccuracies in the evaluation, is the same amount as the enthalpy of fusion H _melt at approx. -23.8 J/g.

In the isothermal dilation measurements of PLA are shown. Test specimens in the form of cubes (dimensions 7 x 7 x 7 mm ³ ) are produced according to steps ii to iv and their isothermal dilatation in one direction is measured in a TMA. To do this, the sample is heated at a moderate heating rate (here 2 K/min) to the isothermal temperature (here 70°C). This temperature is then maintained until an almost constant dilatation value is reached (here 4 hours). The sample is then cooled so slowly (here 0.2 K/min) that the sample can follow the cooling well across the entire cross section. This measurement is repeated in all directions (here XY plane = pressure plane = orientation plane, Z direction = layer structure). It can be seen that after completion of the measurement, an irreversible contraction in the X and Y directions took place, as well as an irreversible expansion in the Z direction (criterion if, ig, ik met).

In is a two-stage isothermal dilation measurement corresponding to steps ii. to iv. The sample (cube 7 x 7 x 7 mm ³ ) made of PLA can be seen perpendicular to the orientation direction (here Z direction). The first isothermal stage is at a temperature between T _G1 and 25 K below T _KS1 , preferably at the temperature of the first heat treatment T _W1 (here 70 ° C) and the second stage above T _KS1 - 25 K, preferably at Temperature of the first heat treatment T _W2 , (here 80 °C) carried out. The first isothermal stage is maintained until the maximum expansion is reached. The mixture is then heated to the second isothermal stage at a moderate heating rate (here 2 K/min). It can be clearly seen that a contraction now occurs at the second isothermal stage (criterion ih).

shows the DSC measurement of a PLA sample after the first stage of the multi-stage isothermal dilation measurement. The progress of the cold crystallization process is determined by comparing the cold crystallization enthalpy H _KS and the enthalpy of fusion |H _melt | obtained and amounts to approx. 22% (criterion ih).

Second polymer: Acrylonitrile styrene acrylate (ASA) from Fillamentum Manufacturing Czech s.r.o.

In the DSC curve of ASA is shown. It can be seen at the baseline that decomposition-free melting or plasticization of the ASA is possible (criterion ia is met). The glass transition T _G (center point) of the examined ASA can be found at 102 °C (criterion ib fulfilled). Neither a melting range nor cold crystallization can be determined. (criterion met)

The heat resistance of ASA was taken from the manufacturer's data sheet. It is 96 °C and is therefore not more than 10 K smaller than T _KS1 (criterion il)

• Die zuvor identifizierten Polymere, erstes Polymer (PLA) und zweites Polymer (ASA) liegen als Filamente für den additiven Fertigungsprozess vor.

The assembly-free mechanisms according to the invention with a joint made of kinematic pairs are manufactured as follows:

• The previously identified polymers, first polymer (PLA) and second polymer (ASA), are available as filaments for the additive manufacturing process.

The geometry for the assembly-free mechanisms with joints made up of kinematic pairs was a swivel joint with an undercut according to selected as well as a Watt mechanism according to consisting of several swivel joints.

All parts are printed using an Ultimaker S3 from Ultimaker BV without any enclosure. Both extruders are equipped with a standard type AA nozzle with a diameter of 0.4 mm. A standard glass building board is used and coated with DIMAFIX from Dima3D before each print.

The print files were generated using CURA 4.8.0 from Ultimaker BV. The printing parameters are set for each material and kept constant for all printed copies. An excerpt of the most important printing parameters can be found in the following table2 Table 2 printing parameters: parameter PLA ASA Layer thickness 60 µm 60 µm Railway prices 350 µm 350 µm Number of external contours 3 4 Infill density 100% 100% Infill pattern ± 45° ± 45° Extrusion temperature 200°C 260°C Temperature of the building board 40°C 40°C Print speed 20mm/s 20mm/s Component fan speed 100% 100%

A universal oven UFE 400 from Memmert GmbH&Co.KG is used for the heat treatment of the polymer molded parts. The polymer moldings were placed in the oven at room temperature and then heated to the corresponding heat treatment temperature T _W1 or T _W2 . A heating rate of approx. 2 K/min is selected. The temperatures T _W1 and T _W2 were set at T _W1 = 70 °C and T _W2 = 80 °C according to the above criteria. The desired temperature is then maintained for 4 hours. The samples are then slowly cooled to room temperature. To ensure a constant cooling rate over the entire cooling cycle, a cooling rate of 0.2 K/min is selected.

After the polymer molding is produced, it has a large amount of play between the kinematic pairs. The first stimulus (heat treatment) at T _W1 reduces this to a usable bearing fit. After the first heat treatment, the polymer molding is put into use. During use, signs of wear occur, which lead to an increase in the bearing gap. At some point the tolerated level for this increase in the bearing gap is exceeded. In this condition, the polymer molded part is initially no longer usable. Now the polymer molding is heat treated a second time (second external stimulus) at T _W2 . This results in a further reduction in the bearing gap and thus the polymer molded part is returned to a usable condition.

shows a schematic representation of the functional principle of the polymer molding according to the invention when using the invention as a kinematic pair in a multi-body system. By using another different external stimulus (T _W2 ), the dimension is once again adjusted to achieve the programmed form.

List of illustrations:

• : Schematic sketch of shearing during the additive manufacturing process
• : Exemplary DSC curve of PLA
• : Determination of T _KS values based on the onset of an exemplary DSC curve
• : Time dependence in isothermal dilation of an oriented sample
• : Time dependence during isothermal dilation in an orientation-free sample cooled with XK/min
• : Two-stage isothermal dilation measurement
• : Relationship between temperature, relaxation and freezing of orientations in the first polymer
• : Course of orientation relaxation and cold crystallization for the first polymer
• : Assembly-free mechanism with a joint made of kinematic pairs
• : Watt mechanism with four joints made of kinematic pairs
• : DSC curves of the first polymer, in this case PLA, at different heating rates
• : Isothermal dilatation measurements of PLA
• : DSC curve of PLA
• : DSC curve from ASA
• : Schematic representation of the use of the invention as a kinematic pair in a multi-body system
• : Sketch of the relevant temperatures

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed 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.

Cited patent literature

• DE 102019007939 A1 [0003]

Claims (12)

Dual stimuli-responsive polymer molding comprising at least 2 different polymers, wherein the first polymer has an orientation of the polymeric chains in at least one orientation direction and a degree of crystallization of less than 10% of its maximum degree of crystallization and a glass transition temperature T _G1 and wherein the first polymer depends on the cooling rate can have a crystallization temperature and wherein crystallization does not occur at a cooling rate of >XK/min and wherein cold crystallization of the first polymer takes place at a cooling rate between _{0 and} the orientation of the polymeric chains loses due to relaxation and where T _KS1 is at least 40 K greater than T _G1 and where in the first polymer the relaxation of the orientation is a faster process than cold crystallization and where cold crystallization and relaxation of the orientation in the orientation direction in the first polymer accompanied by a reduction in the volume and wherein the heat resistance temperature T _HDT2 of the second polymer is a maximum of 10 K below the start temperature of the cold crystallization T _KS1 of the first polymer and wherein the second polymer either has no start temperature of the cold crystallization or the start temperature of the cold crystallization T _KS2 of the second polymer is at least 20 K above T _KS1 and where the second polymer does not experience a reduction in volume during the previous cooling during the subsequent heating and where X assumes values between 500 and 4. Dual stimuli-responsive polymer molding Claim 1 , characterized in that the first polymer is polylactide (PLA) or compounds of this polymer and the second polymer selected from the group of acrylonitrile-styrene acrylate (ASA), acrylonitrile-butadiene-styrene copolymer (ABS), methyl methacrylate-acrylonitrile-butadiene Styrene copolymer (MABS) Styrene-acrylonitrile copolymer (SAN), polystyrene (PS), high density polyethylene (PE-HD), polypropylene (PP), polystyrene (PS), polyamides (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyoxymethylene (POM) and/or mixtures or compounds of these polymers. Dual stimuli-responsive polymer molding Claim 1 , characterized in that the first polymer is polyethylene terephthalate (PET) or a compound of this polymer and the second polymer is selected from the group of polyamides (PA), polycarbonate (PC), polyethylene terephthalate (PBT), polyoxymethylene (POM), polyphenylene sulfide (PPS), Polysulfone (PSU), polyetherimide (PEI), polyamidimide (PAI), polyethersulfone (PESU) and / or mixtures or compounds of these polymers. Dual stimuli-responsive polymer molding Claim 1 , characterized in that the first polymer is polycyclohexylenedimethylene terephthalate (PCT) and / or a copolyester and / or compounds of this polymer and the second polymer selected from the group polyamides (PA), polyoxymethylene (POM), polyphenylene sulfide (PPS), polysulfone (PSU) , polyetherimide (PEI), polyamideimide (PAI), polyethersulfone (PESU) and / or mixtures or compounds of these polymers. Dual stimuli-responsive polymer molding Claim 4 , characterized in that the first polymer is a copolyester of hexylenedimethylene terephthalate and hexylenedimethylene isophthalate (PCTA) with the following formula:

and/or compounds of this polymer. Dual stimuli-responsive polymer molding Claim 1 , characterized in that the first polymer is selected from the group of polyaryl ether ketones (PAEK), polyether ketone (PEK), polyether ether ketone (PEEK), poly (ether ketone ketone) (PEKK), poly (ether ether ketone ketone) (PEEKK), and / or poly (ether ketone) ether ketone ketone) (PEKEKK) as well as mixtures or compounds of these polymers and that second polymer selected from the group polysulfone (PSU), polyetherimide (PEI), polyethersulfone (PESU), polyamideimide (PAI) and / or mixtures or compounds of these polymers. Method for producing a dual stimuli-responsive polymer molding according to one of the preceding claims, comprising the following steps: i. Selection of two polymers based on the presence of the following criteria: a. Presence of a temperature range in which decomposition-free melting or plasticization of the first polymer and melting or plasticization of the second polymer are possible; b. Presence of a glass transition in the first polymer and in the second polymer with the glass transition temperatures T _G1 and T _G2 ; c. Partial crystallizability of the first polymer above T _G1 ; d. Suppression of crystallization for the first polymer at a cooling rate of ≥ XK/min; e. Start of cold crystallization of the first polymer at a cold crystallization start temperature T _KS1 ; f. Orientability of the polymeric chains of the first polymer in at least one direction during additive manufacturing; G. Relaxation of the orientation in the orientation direction for the first polymer above T _G1 ; H. Relaxation of the orientation in the orientation direction faster than crystallization for the first polymer; i. Relaxation of the orientation in the orientation direction of the first polymer is at least partially prevented by cooling at a cooling rate of ≥XK/min; j. Cold crystallization start temperature T _KS1 of the first polymer is at least 40 K higher than the glass transition temperature T _G1 ; k. Crystallization and relaxation of the orientation in the orientation direction in the first polymer are accompanied by a contraction in at least one direction; l. Heat resistance temperature of the second polymer T _HDT2 is a maximum of 10K below T _KS1 ; m. With the second polymer, either cold crystallization is not possible or the starting temperature of the cold crystallization of the second polymer T _KS2 after previous cooling with a cooling rate of ≥XK/min is at least 20 K above T _KS1 ; ii. Promote the in step i. selected polymers to a heated nozzle; iii. Passing the nozzle at the temperature T _Ext while plasticizing and orienting the in step i. selected polymers by the temperature T _Ext and shear during conveying; iv. Layer-by-layer deposition and further orientation perpendicular to the direction of orientation of the polymers plasticized and oriented in step iii onto a substrate with a cooling rate XK/min where T _Ext > T _G for amorphous thermoplastic polymers and where T _Ext > T _melt for partially crystalline thermoplastic polymers and where the cooling rate XK/min allows cooling from T _Ext1 to T _G1 , which is faster than the relaxation time of the orientation of the polymer 1 t _Relax1 and where Procedure according to Claim 7 , characterized in that the information about whether the criteria according to ia, b., c., d., e., i., j., m. are met is obtained by means of dynamic differential calorimetry (differential scannig calorimetry DSC). Procedure according to Claim 7 or 8th , characterized in that the information about whether the criteria if, g., h., k. are met, is determined using isothermal dilation measurements. Procedure according to Claim 7 , 8th or 9 , characterized in that the information about whether criterion il is met is determined by heat resistance measurements according to DIN EN ISO 75 with a sample tension of 0.45 MPa or according to ASTM D648 with a sample tension of 66 psi. Use of a dual stimuli-responsive polymer molding according to one of the Claims 1 until 6 as a kinematic pair in a multibody system. Use after Claim 11 , characterized in that the multi-body system is an assembly-free mechanism.

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