Shape memory polymer and method for producing the same

Abstract

The application belongs to the technical field of polymer materials, and particularly relates to a shape memory polymer and a preparation method thereof. The preparation method of the shape memory polymer comprises the following steps: taking polyethylene as raw material, preparing polyethylene plate through hot pressing, and preparing the shape memory polymer through programmed design; the programmed design is that the polyethylene is heated for the first time, the polyethylene is uniformly stretched for 5-7 times under the action of external force, the stretched length is kept unchanged and is lowered to room temperature, the external force is removed, the stretched sample is heated again, and the shape memory polymer is prepared by lowering to room temperature. The shape memory polymer prepared by the application has good reversible strain capacity, can realize directional liquid conveying when applied to a liquid conveying device, can arbitrarily control the liquid conveying effect of the switch, and meanwhile, the installation operation of the liquid conveying device is simple, which is conducive to popularization and use.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a shape memory polymer and its preparation method. Background Technology

[0002] In recent decades, with the modernization and intelligent development of industry and the increasing demand for energy, the demand for liquid and gas transportation has further increased. Against this backdrop, in addition to traditional transportation solutions using high-pressure pumps, researchers have begun to study entirely new liquid transportation solutions. Heat-driven liquid transportation devices utilize an external heat source to heat the working fluid within the device, causing changes in fluid pressure, temperature, and phase, thereby directly or indirectly achieving fluid transportation. While liquid transportation devices are currently widely used in the petroleum, textile, and pharmaceutical industries in China, the design of directional liquid transportation devices with arbitrary on / off control has not yet reached a unified understanding or standardization. Because the contact hysteresis effect and static friction when a liquid contacts a material surface hinder liquid movement, directional liquid movement is very difficult without external energy. In recent years, domestic and international experts have proposed many new liquid transportation device structures to improve the energy-saving performance of liquid transportation devices and have continuously improved upon them, but the results have not been very significant. Therefore, there is an urgent need to develop a liquid transportation device that can achieve directional liquid movement and allows for arbitrary on / off control. Summary of the Invention

[0003] This invention aims to provide a shape memory polymer and its preparation method. The shape memory polymer prepared by this invention has good reversible deformation ability. When applied to a liquid conveying device, it can achieve directional liquid conveying and liquid conveying effect with arbitrary controllable switching. At the same time, the liquid conveying device is simple to install and operate, which is conducive to its widespread use.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a shape memory polymer, comprising the following steps:

[0005] Using polyethylene as raw material, polyethylene sheets are produced by hot pressing, and shape memory polymers are produced through programmed design.

[0006] The programmed design is as follows: the polyethylene is heated for the first time, and then uniformly stretched under the action of external force. The stretching length is kept constant and cooled to room temperature. The external force is removed, and the stretched strip is heated again and cooled to room temperature to obtain the shape memory polymer.

[0007] This invention introduces internal stress into polyethylene samples through a programmed design process, enabling them to exhibit a temperature-responsive, reversible shape memory effect without the need for external forces. The programmed polyethylene sample uses chain entanglement as the provider of internal stress, with the melting / crystallization of crystalline regions as the reversible phase. During heating, the melting of crystalline regions, driven by entropy, causes the macromolecular chains within the polyethylene sample to change from an oriented crystalline state to a random coil state, resulting in a gradual contraction of the sample macroscopically. During cooling, the molten random coil state, under the internal stress provided by the chain entanglement, returns to an oriented crystalline state, causing the sample macroscopically to gradually elongate, thus ultimately achieving reversible deformation of the polymer at a specific excitation temperature.

[0008] The heating operation in the programmed design process of this invention has a significant impact on the reversible strain capability of the final shape memory polymer. The first heating and the second heating operation work together to control the temperature of the polymer within a suitable range, ultimately ensuring that the shape memory polymer achieves a high reversible strain capability.

[0009] Preferably, the temperature of the first heating is 145-165°C, and the heating time is 10-30 minutes.

[0010] Preferably, the reheating temperature is 140°C.

[0011] Preferably, the polyethylene has a relative molecular weight of 3 million to 5 million.

[0012] Preferably, the pressure of the hot pressing is 20-30 MPa, and the hot pressing time is 30-40 min.

[0013] Preferably, the uniform stretching involves stretching the polyethylene to 5 to 7 times its original length.

[0014] Preferably, the thickness of the polyethylene sheet is 3 to 5 cm.

[0015] A method for preparing the shape memory polymer to obtain the shape memory polymer.

[0016] A temperature-responsive liquid delivery device using the shape memory polymer is provided. The assembly method of the temperature-responsive liquid delivery device is as follows: a liquid delivery pipe is fixed with the shape memory polymer, and the shape memory polymer on the liquid delivery pipe is heated in sequence. The directional movement and residence of the liquid in the liquid delivery pipe are achieved by the shape memory polymer squeezing the liquid delivery pipe when heated and releasing the liquid delivery pipe when cooled.

[0017] Preferably, the heating of the shape memory polymer involves heating the shape memory polymer to 138–140°C.

[0018] When the shape memory polymer prepared by this invention is applied to a liquid conveying device, if the excitation temperature (heating temperature) is too low, the shape memory polymer does not have a reversible shape memory effect; if the excitation temperature is too high, the shape memory polymer can only exhibit a one-way shape memory effect and does not have a reversible shape memory effect.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The shape memory polymer prepared by the present invention has excellent reversible strain capability, with a reversible strain of up to 26%, which is significantly higher than the reversible strain capability of shape memory polymers in the prior art. The higher the reversible strain capability, the stronger the liquid transport capability.

[0021] (2) The shape memory polymer prepared by the present invention can be applied to liquid conveying devices. It can not only realize the directional conveying of liquid and arbitrary control of the switch, but also has a simple assembly process and does not require a specific driving device before use. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the liquid conveying device of the present invention.

[0023] Figure 2 This is a schematic diagram of the shape memory polymer of the present invention used for liquid transport. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0026] Manufacturer information for the polyethylene materials used in the embodiments and comparative examples of this invention:

[0027] Polyethylene: M-II type from Beijing Dongfang Petrochemical Company Additives Plant No. 2, with a relative molecular mass of 3 million;

[0028] Polyethylene-1: Yanshan Petrochemical Company MI-2 type, with a relative molecular mass of 1 million;

[0029] Polyethylene-2: Korean Oil & Chemical Co., Ltd. U050 type, with a relative molecular mass of 5 million.

[0030] Example 1

[0031] Preparation of shape memory polymers:

[0032] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0033] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0034] Preparation of liquid delivery device:

[0035] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0036] Example 2

[0037] Preparation of shape memory polymers:

[0038] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0039] 2. Programmed design: The polyethylene sample was placed in an oven at 155℃ and heated for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0040] Preparation of liquid delivery device:

[0041] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0042] Example 3

[0043] Preparation of shape memory polymers:

[0044] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0045] 2. Programmed design: The polyethylene sample was heated in an oven at 165℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0046] Preparation of liquid delivery device:

[0047] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0048] Example 4

[0049] Preparation of shape memory polymers:

[0050] 1. Preparation: Using polyethylene-2 ​​as raw material, it is pressed at 170℃ and 20MPa for 30min to obtain a polyethylene sheet with a thickness of 3.0mm, and then the polyethylene sheet is cut into strips using a cutter.

[0051] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0052] Preparation of liquid delivery device:

[0053] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0054] Example 5

[0055] Preparation of shape memory polymers:

[0056] 1. Preparation: Using polyethylene as raw material, it is pressed at 170℃ and 30MPa for 30min to obtain a polyethylene sheet with a thickness of 3.0mm, and then the polyethylene sheet is cut into strips using a cutter.

[0057] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0058] Preparation of liquid delivery device:

[0059] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0060] Example 6

[0061] Preparation of shape memory polymers:

[0062] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 25MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0063] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0064] Preparation of liquid delivery device:

[0065] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0066] Example 7

[0067] Preparation of shape memory polymers:

[0068] 1. Preparation: Using polyethylene as raw material, it is pressed at 170℃ and 20MPa for 40min to obtain a polyethylene sheet with a thickness of 5.0mm, and then the polyethylene sheet is cut into strips using a cutter.

[0069] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 30 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 7 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0070] Preparation of liquid delivery device:

[0071] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0072] Example 8

[0073] Preparation of shape memory polymers:

[0074] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0075] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0076] Preparation of liquid delivery device:

[0077] A horizontal silicone tube is fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 140°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to contract and compress the silicone tube, causing ethylene glycol droplets to flow. After the hot air gun is removed, the strip temperature drops to room temperature, the strip elongates, and the silicone tube returns to its original shape. When heating the next strip, the ethylene glycol droplets continue to move forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0078] Comparative Example 1

[0079] Preparation of shape memory polymers:

[0080] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0081] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 170℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0082] Compared with Example 1, the only difference in this comparative example is that the reheating temperature is 170°C.

[0083] Preparation of liquid delivery device:

[0084] A horizontal silicone tube was fixed to a wooden board with the prepared shape memory polymer, and the board was placed perpendicular to the ground. Heating to 138°C with a hot air gun, the programmed polyethylene strip (shape memory polymer) did not shrink, did not compress the silicone tube, and the position of the glycol droplet remained unchanged.

[0085] Because the polyethylene strip was reheated to an excessively high temperature during the programmed design process, it lost its reversible shape memory effect.

[0086] Comparative Example 2

[0087] Preparation of shape memory polymers:

[0088] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 15MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0089] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0090] Compared with Example 1, the only difference in this comparative example is that the pressure of hot pressing is 15 MPa.

[0091] Preparation of liquid delivery device:

[0092] A horizontal silicone tube was fixed to a wooden board with the prepared shape memory polymer, and the board was placed perpendicular to the ground. Heating the tube to 138°C with a hot air gun caused the programmed polyethylene strip (shape memory polymer) to shrink slightly. Even with slight compression of the silicone tube, the position of the glycol droplet remained almost unchanged.

[0093] Because the pressure during hot pressing in the preparation process is too low, the polyethylene raw material is not completely melted, resulting in a low reversible strain capacity of the polyethylene sample.

[0094] Comparative Example 3

[0095] Preparation of shape memory polymers:

[0096] 1. Preparation: Using polyethylene-1 as raw material, polyethylene sheets with a thickness of 3.0 mm were prepared by pressing at 170℃ and 20MPa for 30 min, and then the polyethylene sheets were cut into strips using a cutter.

[0097] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0098] Compared with Example 1, the only difference in this comparative example is that the raw material is polyethylene-1 with a relative molecular mass of 1 million.

[0099] Preparation of liquid delivery device:

[0100] A horizontal silicone tube is fixed to a wooden board using the prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) begins to slowly contract and compress the silicone tube, causing ethylene glycol droplets to move slowly. After the hot air gun is removed, the strip temperature drops to room temperature, and the strip slowly elongates, while the silicone tube slowly returns to its original shape. When heating the next polyethylene strip, the ethylene glycol droplet continues to move slowly forward, and the ethylene glycol liquid can be stopped at any position as needed, thus achieving a liquid delivery effect with arbitrary controllable switching.

[0101] Comparative Example 4

[0102] Preparation of shape memory polymers:

[0103] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0104] 2. Programmed design: The polyethylene sample was heated in an oven at 170℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0105] Compared with Example 1, the only difference in this comparative example is that the temperature of the first heating is 170°C.

[0106] Preparation of liquid delivery device:

[0107] A horizontal silicone tube was fixed to a wooden board with the prepared shape memory polymer, and the board was placed perpendicular to the ground. Heating to 138°C with a hot air gun, the programmed polyethylene strip (shape memory polymer) did not shrink, did not compress the silicone tube, and the position of the ethylene glycol droplet remained unchanged.

[0108] Because the initial heating temperature during the programmed design process was too high, a large number of physical cross-linking points inside the polyethylene sample were lost, and the prepared polyethylene sample did not have a reversible shape memory effect, thus failing to achieve the purpose of programmed design.

[0109] Comparative Example 5

[0110] Preparation of shape memory polymers:

[0111] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 10 minutes to obtain polyethylene sheets with a thickness of 3.0mm. The polyethylene sheets were then cut into strips using a cutter.

[0112] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0113] Compared with Example 1, the only difference in this comparative example is that the hot pressing time is 10 minutes.

[0114] Preparation of liquid delivery device:

[0115] A horizontal silicone tube was fixed to a wooden board with the prepared shape memory polymer, and the board was placed perpendicular to the ground. Heating to 138°C with a hot air gun, the programmed polyethylene strip (shape memory polymer) did not shrink, did not compress the silicone tube, and the position of the ethylene glycol droplet remained unchanged.

[0116] Because the hot pressing time during the preparation process is relatively short, the polyethylene raw material is not fully melted and recrystallized, resulting in fewer crystalline regions. Consequently, the polyethylene sample cannot achieve the reversible shape memory effect.

[0117] Comparative Example 6

[0118] Preparation of shape memory polymers:

[0119] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 50 minutes to obtain polyethylene sheets with a thickness of 3.0mm. The polyethylene sheets were then cut into strips using a cutter.

[0120] 2. Programmed Design: A polyethylene sample was heated in an oven at 145°C for 10 minutes. Then, under external force, the polyethylene sample was uniformly stretched 5 times and its stretched shape was maintained while it was cooled to room temperature. The external force was then removed. The stretched sample was then reheated to 140°C. The polyethylene sample shrank due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining a shape memory polymer.

[0121] Compared with Example 1, the only difference in this comparative example is that the hot pressing time is 50 minutes.

[0122] Preparation of liquid delivery device:

[0123] A horizontal silicone tube was fixed to a wooden board using a prepared shape memory polymer, with the board placed perpendicular to the ground. Heated to 138°C with a hot air gun, a programmed polyethylene strip shrank, compressing the silicone tube and altering the position of the ethylene glycol droplets. The polyethylene strip not only turned yellow, but after five heating cycles with the hot air gun, further heating caused the polyethylene strip to stop shrinking.

[0124] Because the hot pressing time during the preparation process is too long, it not only accelerates the aging of polyethylene raw materials, but also accelerates the release of internal stress, so that after repeated heating, it no longer has the reversible shape memory effect and cannot be reused.

[0125] Comparative Example 7

[0126] Preparation of shape memory polymers:

[0127] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0128] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0129] Preparation of liquid delivery device:

[0130] A horizontal silicone tube was fixed to a wooden board with the prepared shape memory polymer, and the board was placed perpendicular to the ground. Heated to 160°C with a hot air gun, a programmed polyethylene strip (shape memory polymer) began to shrink and compress the silicone tube. A low-potential point was formed at the point of compression, and ethylene glycol droplets flowed towards this low-potential point. After the hot air gun was removed, the strip temperature dropped to room temperature, the strip length remained almost unchanged, the silicone tube remained compressed, and the ethylene glycol droplets remained at the low-potential point.

[0131] Compared with Example 1, the only difference in this comparative example is that the excitation temperature is 160°C.

[0132] Because the excitation temperature was too high, the polyethylene sample lost the reversible shape memory effect, so it only exhibited a one-way shape memory effect during the first excitation.

[0133] Comparative Example 8

[0134] Preparation of shape memory polymers:

[0135] 1. Preparation: Using polyethylene as raw material, polyethylene sheets were pressed at 170℃ and 20MPa for 30min to obtain 3.0mm thick polyethylene sheets, and then cut into strips using a cutter.

[0136] 2. Programmed design: The polyethylene sample was heated in an oven at 145℃ for 10 minutes. Then, under the action of external force, the polyethylene sample was uniformly stretched 5 times and kept in the stretched shape while being cooled to room temperature. After removing the external force, the stretched sample was reheated to 140℃. The polyethylene sample shrank significantly due to the melting of the crystalline regions. It was then cooled to room temperature again to recrystallize, thus obtaining the shape memory polymer.

[0137] Preparation of liquid delivery device:

[0138] A horizontal silicone tube was fixed to a wooden board with the prepared shape memory polymer, and the board was placed perpendicular to the ground. Heating to 100°C with a hot air gun, the programmed polyethylene strip (shape memory polymer) did not shrink, did not compress the silicone tube, and the position of the glycol droplet remained unchanged.

[0139] Compared with Example 1, the only difference in this comparative example is that the excitation temperature is 100°C.

[0140] Because the excitation temperature was too low and did not reach the excitation temperature of the programmed polyethylene specimen, the programmed polyethylene specimen did not shrink, the silicone tube was not squeezed, and the position of the ethylene glycol droplet did not change.

[0141] Experimental Example 1: Determination of Reversible Strain Capacity

[0142] The reversible strain capacity of the shape memory polymers prepared in Examples 1-8 and Comparative Examples 1-8 was measured. The measurement method is as follows:

[0143] Instrument: DMA 850 dynamic thermomechanical analyzer;

[0144] Methods: The loading method adopted was tensile mode, and the test mode was controlled force mode. During the test, the strain curve of polyethylene strip (shape memory polymer) under three cycles of 90℃-138℃ was tested at a sampling frequency of 5.0 pts / s and a heating and cooling rate of 3℃ / min. The average reversible strain capacity of the three cycles was calculated.

[0145] The experimental results are shown in Table 1.

[0146] Table 1

[0147]

[0148]

[0149] As can be seen from the data in Table 1, the shape memory polymer prepared in the embodiments of the present invention has a high reversible strain capacity, which can reach up to 26.04%.

[0150] In Comparative Example 1, the reheating temperature during the programmed design process of the shape memory polymer was too high, causing the resulting shape memory polymer to lose its reversible shape memory effect. In Comparative Example 2, the hot-pressing pressure during the preparation of the shape memory polymer was too low, resulting in a low reversible strain capacity and difficulty in achieving liquid transport. In Comparative Example 3, the polyethylene raw material used had too low a relative molecular weight, resulting in a low reversible strain capacity of only 7.44% in the resulting shape memory polymer. In Comparative Example 4, the initial heating temperature during the programmed design process of the shape memory polymer was too high, resulting in the resulting shape memory polymer not exhibiting a reversible shape memory effect. In Comparative Example 5, the hot-pressing time during the preparation of the shape memory polymer was too short, resulting in the final shape memory polymer failing to achieve a reversible shape memory effect. In Comparative Example 6, the hot-pressing time during the preparation of the shape memory polymer was too long, causing the resulting shape memory polymer to age easily and lose its reversible shape memory effect after multiple heatings, making it unusable. In Comparative Example 7, the excitation temperature of the shape memory polymer was too high, resulting in the resulting shape memory polymer only exhibiting a single-pass shape memory effect during the first excitation. The excitation temperature of the shape memory polymer in Comparative Example 8 was too low, resulting in the shape memory polymer not exhibiting a reversible shape memory effect.

[0151] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A temperature-responsive liquid delivery device, characterized in that, The assembly method of the temperature-responsive liquid delivery device is as follows: the liquid delivery pipe is fixed with a shape memory polymer, and the shape memory polymer on the liquid delivery pipe is heated in sequence. The directional delivery and residence of the liquid in the liquid delivery pipe is achieved by the shape memory polymer squeezing the liquid delivery pipe when heated and releasing the liquid delivery pipe when cooled. The method for preparing the shape memory polymer includes the following steps: Polyethylene sheets are produced by hot pressing using polyethylene as raw material, and then cut into long strips using a cutter. Shape memory polymers were fabricated through programmed design. The programmed design is as follows: a polyethylene sample is heated for the first time, and then the polyethylene sample is uniformly stretched under the action of external force. The stretched length is kept constant and the sample is cooled to room temperature. The external force is removed, and the stretched sample is heated again and cooled to room temperature to obtain a shape memory polymer.

2. The temperature-responsive liquid delivery device as described in claim 1, characterized in that, It must include at least one of the following (1) to (2): (1) The temperature of the first heating is 145-165℃, and the time of the first heating is 10-30 min; (2) The reheating temperature is 140℃.

3. The temperature-responsive liquid delivery device as described in claim 1, characterized in that, The polyethylene has a relative molecular weight of 3 million to 5 million.

4. The temperature-responsive liquid delivery device as described in claim 1, characterized in that, The hot pressing pressure is 20-30 MPa, and the hot pressing time is 30-40 min.

5. The temperature-responsive liquid delivery device as described in claim 1, characterized in that, The uniform stretching refers to stretching the polyethylene to 5 to 7 times its original length.

6. The temperature-responsive liquid delivery device as described in claim 1, characterized in that, The thickness of the polyethylene sheet is 3 to 5 cm.

7. The temperature-responsive liquid delivery device as described in claim 1, characterized in that, Heating shape memory polymers involves heating the shape memory polymers to 138–140°C.

Images