CN115960360B - Press-clamping effect material and preparation method and application thereof - Google Patents
Press-clamping effect material and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a clamp effect material which is a PEG/PET solid-solid phase change copolymer material, wherein the clamp effect material comprises PET serving as a carrier framework material and PEG serving as a phase change material, and the mass ratio of the PET to the PEG is 1:15-25. The PEG/PET material has huge latent heat and entropy change of phase change in the phase change process, huge pressure-heat entropy change and relatively high sensitivity of phase change to a pressure field, and can achieve huge isothermal entropy change value and pressure-heat entropy change under small pressure, so that the material has potential application value in the aspect of pressure-heat refrigeration technology. The PEG with different molecular weights and the PEG with different proportions are used together to realize the regulation and control of thermal properties such as phase transition temperature, so that the PEG/PET system becomes a regulatable piezothermal material system, and the method has potential application value in the aspects of meeting the refrigeration technical requirements under various conditions, optimizing the refrigeration efficiency and the like.
Description
Technical Field
The invention relates to a material with a clamp pressing effect, a preparation method and application thereof
Background
The application of the refrigeration technology in the society is more and more widespread nowadays, and the refrigeration energy consumption is more than 15% of the total energy consumption, which is equivalent to 450×10 each year 6 Ton of CO 2 Discharge amount. The working gas freon and the like of the vapor compression refrigeration technology commonly used at present have extremely strong ozone depletion effect, and the Carnot cycle efficiency can only reach 25 percent. Finding a refrigeration technology which can be environment-friendly, efficient and energy-saving is important, and meanwhile, the selection of refrigeration working media cannot be ignored.
Solid state refrigeration technology based on thermal effects is a particular concern and is considered to be a promising alternative to more environmentally friendly and more efficient gas compression based refrigeration technology. The solid phase change material can generate entropy change and temperature change under the driving of a magnetic field, an electric field, axial force or isostatic pressure, namely magnetic card (heat), electric card (heat), spring card (heat) and pressing card (heat) effects, which are collectively called solid heat effects. The thermal effect of the solid-state primary phase change offers the possibility of controlling the latent heat exchange by an external field, with refrigeration energy efficiency up to 75%.
Among the solid-state thermal effects studied at present, the research of magnetocaloric and electrothermal effects is more sufficient. The use of magnetocaloric effects often requires a large magnetic field to drive, which is not easily achieved in practical use; meanwhile, the refrigerating working medium magnetic material generally contains rare earth elements in nature, so that the use cost is increased to a certain extent. The refrigeration temperature span of the electrothermal effect is usually limited, and the practical application is limited when the refrigeration temperature span is often generated at a temperature different from the ambient temperature; the polar material of the refrigeration working medium needs to be driven by an electric field, and a complex material synthesis process is also needed to reduce the obstruction leakage current.
Compared with magnetic card, card flicking and electric card effect, the research of card pressing effect is still in the starting stage, so that the research of novel card pressing material and the elucidation of card pressing effect mechanism are main research directions in the current stage. The autoclave effect refers to a physical phenomenon in which a material generates exothermic or endothermic behavior due to pressure. Mechanical thermal effects driven by mechanical force, particularly autoclave effects, are commonly existing in primary phase change materials, but do not require that the materials have magnetic or electric polarization characteristics, so that the external field driven phase change is easier and more convenient to realize; meanwhile, the preparation of the pressure heating material is easy, and the packaging technology is not limited to the shape of the material. The study of the autoclave effect is indispensable for the pursuit of green sustainable development of refrigeration technology.
The giant autoclave effect typically occurs near the primary phase transition of a material, which will be driven by pressure to produce a thermal response when an appropriate pressure is applied near the phase transition temperature of the material. In current studies, the autoclave effect is generally evaluated based on isothermal entropy change under pressure or adiabatic temperature change. In recent years, the autoclave effect of many materials has been reported to exhibit excellent refrigeration performance and a distinctive field-induced phase change. Such as MnCoGe 0.99 In 0.01 、MnCoGeB 0.03 、(MnNiSi) 0.62 (FeCoGe) 0.38 、(Ni 50 Mn 31.5 Ti 18.5 ) 99.8 B 0.2 Iso-alloy material, (NH) 4 ) 2 SO 4 、(NH 4 ) 2 NbOF 5 、(NH 4 ) 2 SnF 6 、(NH 4 ) 2 MoOF 4 Equal inorganic salts and superionic conductors AgI, caF 2 Can reach more than 50 J.Kg under certain pressure -1 ·K -1 Isothermal entropy change of (c). TRIS [ (NH) 2 )C(CH 2 OH) 3 ]、PG[(CH 3 )C(CH 2 OH) 3 ]、AMP[(NH 2 )(CH 3 )C(CH 2 OH) 2 ]、NPG[(CH 3 ) 2 C(CH 2 OH) 2 ]The novel plastic crystal piezocaloric material has more excellent piezocaloric property, the isothermal piezocaloric entropy change of the material can be higher than that of the inorganic material by an order of magnitude, and the maximum value can reach 680 J.Kg -1 ·K -1 Left and right. The discovery of plastic materials plays an indispensable role in the development of the autoclave effect due to the considerable autoclave effect.
Suitable solid materials for commercial use are considered to be formedThe problems of toxicity and the like, and the phase change of the high latent heat under the condition of required working temperature. For example, the plastic crystal material generates huge isothermal entropy change after undergoing primary phase change under pressure, so that the plastic crystal material becomes an excellent candidate material for the autoclave effect. However, in practical applications efficient and viable refrigeration technology necessarily requires materials with a high sensitivity to applied external fields while having a large latent heat. Such materials are like MnCoGe 0.99 In 0.01 The alloy is subjected to a pressure of 3kbar to obtain a alloy of 52 J.kg -1 ·K -1 Is a piezothermal entropy change of (1); inorganic Compound (NH) 4 ) 2 SO 4 Although it is possible to achieve 60 J.Kg at a pressure of 1kbar -1 ·K -1 But the entropy change value of the pressure-heat entropy change is not comparable with that of plastic crystal materials; the plastic crystal material such as TRIS which has great interest has isothermal piezothermal entropy change of 682 J.Kg at the highest -1 ·K -1 But high pressures of about 50kbar are required in applications due to their great thermal hysteresis. The application of high pressure is difficult to achieve in practical applications like high magnetic fields. It is therefore more promising to find a phase change material with a small pressure driving a large latent heat.
Disclosure of Invention
It is therefore an object of the present invention to provide a novel high performance autoclave material system, a process for its preparation and its use.
The inventor of the invention has found through intensive research that the PEG/PET copolymer with solid-solid phase transition prepared by a physical modification method is a typical primary phase transition material, and the phase transition process is accompanied by larger phase transition latent heat and entropy change, and the entropy change of the phase transition process can reach 430 J.Kg at maximum -1 ·K -1 . Compared with the plastic crystal material with giant entropy change, the phase change of the PEG/PET copolymer is more sensitive to the action of a pressure field, and the reversible entropy change is 41 J.Kg under the pressure of 1kbar -1 ·K -1 . The maximum pressure-driven phase change rate can reach 10.7K/kbar, and the maximum reversible entropy change can be achieved under the driving of small pressure of 3 kbar. The giant autoclave effect under small pressure is shown for the first time, and the sensitivity to the pressure field is also better than that of most of the giant autoclave materials reported before. By regulating the molecular weight of PEG, the preparation method canThe phase transition temperature and entropy change of the PEG/PET copolymer are effectively regulated and controlled, and the performance of the autoclave material is optimized.
According to the invention, polyethylene terephthalate (PET) is used as a framework material, polyethylene glycol (PEG) is used as a phase change material, and a solid-liquid phase change material PEG is fixed on a carrier framework PET by a physical modification method, so that a PEG/PET solid-solid phase change copolymer material with different PEG molecular weights is prepared. The two ends of the PEG molecule are bound to the rigid PET molecular chain by hydrogen bonds or other intermolecular forces, so that the PEG molecule cannot be separated from the binding and cannot translate freely, and therefore, the PEG cannot be converted from solid state to liquid state at the melting point; however, PEG molecules with two bound ends can still rotate or vibrate, and can form an amorphous state or a crystalline state along with the change of temperature, so that solid-solid phase transformation occurs. The eutectic reaction of PEG with different molecular weights in the PEG/PET copolymer causes the synergistic effect of eutectic addition, so that the PEG/PET copolymer becomes a novel solid-solid phase change material with larger phase change enthalpy and controllable phase change temperature. The material has the advantages of simple preparation method, low cost, capability of achieving huge isothermal entropy change value under small pressure, and great potential of the piezocaloric refrigeration working medium.
The term PEG as used herein is a commercial chemical Composition HO (CH) 2 CH 2 O) n H (n=13 to 454); PET is commercially available in chemical form (C 10 H 8 O 4 ) m (m=52 to 104).
As used herein, "molecular weight" is the relative molecular weight.
In the present invention, since PET is used as a carrier skeleton and PEG is a phase change material, only the molecular weight of PEG is shown in abbreviations of PEG/PET materials, for example, PEG/PET materials having a relative molecular weight of 4000 of PEG is denoted as PEG4000/PET; the molecular weight of PEG is shown by the molecular weight and proportion of PEG and the (PEG 1+ PEG 2)/PET material used in combination of two or more types is shown by the molecular weight and proportion of PEG, for example, the PEG/PET material formed by mixing PEG with the molecular weight of 4000 and 20000 is denoted as (aPEG4000+bPE20000)/PET, wherein a and b are relative mass parts of PEG4000 and PEG20000 respectively.
The aim of the invention is achieved by the following technical scheme.
The invention provides a clamp effect material which is a PEG/PET solid-solid phase change copolymer material and comprises polyethylene terephthalate serving as a carrier framework material and polyethylene glycol serving as a phase change material, wherein the mass ratio of the polyethylene terephthalate to the polyethylene glycol is 1:15-25.
The press-clamping effect material provided by the invention, wherein hydroxyl groups in PEG molecules and hydroxyl groups at the ends of PET molecules form hydrogen bond connection so as to retain the crystal characteristics of PEG.
The weight ratio of PET to PEG is preferably 1:18-20.
The press-clamping effect material provided by the invention, wherein the molecular weight of PEG can be 600-20000, and the relative molecular weight of PET can be 10000-20000.
The clamp effect material provided by the invention, wherein the entropy of the phase change process is changed into 300 J.Kg -1 ·K -1 ～500J·Kg -1 ·K -1 。
The invention provides a clamp effect material, wherein the maximum isothermal entropy change of the clamp effect material is 300 J.Kg under the pressure of 0.1GPa -1 ·K -1 ～500J·Kg -1 ·K -1 。
The pressure card effect material provided by the invention has the pressure driving phase change rate of 76-105K-GPa -1 。
The invention also provides a preparation method of the card pressing effect material, which comprises the following steps:
1) Respectively dissolving PEG and PET in an organic solvent to obtain a PEG solution and a PET solution;
2) Mixing the PEG solution and the PET solution according to the mass ratio of the PEG to the PET, carrying out copolymerization reaction at 180-200 ℃, and cooling to obtain the clamp effect material.
According to the preparation method provided by the invention, preferably, the organic solvent in the step 1) is dimethyl sulfoxide. Preferably, the step 1) includes: at 40-60 ℃, PEG and dimethyl sulfoxide are prepared into PEG solution according to the mass ratio of 1:2-5; at 180-200 ℃, PET and dimethyl sulfoxide are prepared into PET solution according to the mass ratio of 1:15-25.
Preferably, the step 1) may further include: drying the raw material PEG with a silica gel desiccant until the weight is constant before preparing the solution; and placing the PET in an oven, and drying at 100-120 ℃ for more than 4 hours until the weight is constant.
Preferably, the step 2) may further include: washing and filtering the products of the polymerization reaction, and then placing the products in a vacuum drying oven for vacuum drying for 1 to 48 hours at the temperature of 80 to 120 ℃.
The invention also provides application of the press-clamping effect material or the press-clamping effect material obtained by the preparation method in the press-heating refrigeration technology.
Compared with the prior art, the invention has the following obvious advantages: firstly, the PEG/PET material is easy to prepare and the raw materials are low in cost. Meanwhile, on one hand, the PEG/PET material prepared by the inventor is a typical primary phase change material, and the phase change causes huge phase change latent heat and entropy change, and the entropy change in the phase change process can reach 430 J.Kg -1 ·K -1 . Compared with the plastic crystal material with the giant entropy change reported in the past, the PEG/PET phase change material in the invention is more sensitive to the action of a pressure field, and has reversible entropy change of 41J Kg under the pressure of 1kbar -1 ·K -1 The pressure-driven phase change rate is 10.7K/kbar, and the maximum reversible entropy change (-430 J.Kg) can be achieved under the driving of small pressure of 3kbar -1 ·K -1 ). The giant autoclave effect at small pressure is shown for the first time, and the sensitivity to the pressure field is also better than all the giant autoclave materials reported previously. On the other hand, the inventor finds out through the thermal test result that the entropy change is maximum in the phase change process when the pure PEG molecular weight is 10000; the PEG with different molecular weights can generate synergistic effect after being properly combined, the entropy change is larger than that of the PEG when the PEG is singly used, and the phase transition temperature can also be subjected to synergistic effect. Therefore, the phase transition temperature and entropy change of the piezothermal material can be effectively regulated and controlled by regulating and controlling the molecular weight of PEG, and the optimization of the performance of the piezothermal material is realized. The PEG/PET system material has the advantages of phase change regulation and giant pressure heating effect, and has great potential application value in pressure heating refrigeration technology.
Drawings
Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:
FIGS. 1A to 1C are SEM scanning electron micrographs of PET6000/PET obtained in example 1 and graphs showing XRD results at room temperature.
FIGS. 2A to 2E are heat flow curves under normal pressure of PEG6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET and (1/2 PEG4000+1/2PEG 20000)/PET prepared in examples 1 to 5, and arrows represent the heating and cooling processes.
Fig. 3A to 3E are heat flow curves under different pressures of PEG6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET and (1/2 PEG4000+1/2PEG 20000)/PET prepared in examples 1 to 5, and arrows represent the heating and cooling processes.
FIGS. 4A-4E are graphs showing entropy change under different pressures of PEG6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET, and (1/2 PEG4000+1/2PEG 20000)/PET prepared in examples 1-5.
FIG. 5 is a graph showing isothermal entropy change curves caused by pressures of PEG6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET, and (1/2 PEG4000+1/2PEG 20000)/PET prepared in examples 1-5, wherein P represents pressure, and arrows represent pressurization and depressurization processes.
FIG. 6 is a graph showing adiabatic temperature change curves caused by the pressure of PEG6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET, and (1/2 PEG4000+1/2PEG 20000)/PET prepared in examples 1 to 5. In the figure, P represents pressure and arrows represent pressurization and depressurization processes.
FIG. 7 shows the reversible isothermal entropy change curves of the PEG6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET and (1/2 PEG4000+1/2PEG 20000)/PET prepared in examples 1-5. In the figure, P represents pressure and arrows represent pressurization and depressurization processes.
Detailed Description
The following detailed description of the invention is provided in connection with the accompanying drawings that are presented to illustrate the invention and not to limit the scope thereof.
Examples 1 to 23
The raw materials and equipment used in the examples are described below:
1) Polyethylene glycol and dimethyl sulfoxide (DMSO, molecular formula C 2 H 6 OS) were purchased from national pharmaceutical group chemical reagent limited, and the purity was not less than 98%.
2) Polyethylene terephthalate has a purity of not less than 98% and is available from the company sciences of the astrology of su-state.
3) The magnetic stirrer used to prepare PEG/PET was purchased from Beijing Ligawa technology Co., ltd, and was designated as magnetic stirrer C-MAG HS7 Control.
4) The source of the instrument used by the scanning electron microscope is compound scientific instrument (Shanghai) limited company, feina China, and the model is phenol proX; the measuring instrument used for room temperature XRD was a Rigaku-SmartLab temperature-variable X-ray diffractometer manufactured by Japanese Kabushiki Kaisha;
5) The entropy change and the autoclave effect of the phase change process are measured by a SETARAM microcalorimeter (i.e., differential scanning calorimeter under pressure DSC) manufactured by Kapu technologies, france.
The molecular weights of PEG used in the examples of the present invention are 600, 2000, 4000, 6000, 8000, 10000, 12000, 20000, and the molecular weight of pet is 15000, and the molecular weights of PEG and the synthesis temperature conditions used in each example are specifically listed in table 1.
The preparation method comprises the following steps:
1) Drying the raw material PEG by using a silica gel drying agent until the weight is constant; placing PET in an oven, and drying at 110 ℃ for more than 4 hours until the weight is constant;
2) PET and PEG with different molecular weights are weighed according to the mass ratio. Preparing PEG and dimethyl sulfoxide into solution according to the mass ratio of 1:3 at 60 ℃; preparing PET and dimethyl sulfoxide into solution according to the mass ratio of 1:20 at 200 ℃;
3) Mixing the two solutions in the step 2) at the mass ratio of PEG to PET of 95:5 at 200 ℃, carrying out copolymerization reaction, releasing a large amount of heat, quickly forming a viscous paste by the solution, cooling to room temperature, washing and filtering;
4) And (3) placing the copolymer obtained by filtering in the step (3) in a vacuum drying oven, and vacuum drying at 100 ℃ for 24 hours to obtain the PEG/PET copolymer.
TABLE 1
| Examples numbering | PEG molecular weight | PEG/PET copolymer |
| 1 | 6000 | PEG6000/PET |
| 2 | 10000 | PEG10000/PET |
| 3 | 20000 | PEG20000/PET |
| 4 | 4000，20000 | (2/3PEG4000+1/3PEG20000)/PET |
| 5 | 4000，20000 | (1/2PEG4000+1/2PEG20000)/PET |
| 6 | 2000 | PEG2000/PET |
| 7 | 4000 | PEG4000/PET |
| 8 | 8000 | PEG8000/PET |
| 9 | 2000，20000 | (1/2PEG2000+1/2PEG20000)/PET |
| 10 | 2000，20000 | (2/3PEG2000+1/3PEG20000)/PET |
| 11 | 2000，20000 | (1/3PEG2000+2/3PEG20000)/PET |
| 12 | 4000，20000 | (1/3PEG4000+2/3PEG20000)/PET |
| 13 | 6000，20000 | (1/2PEG6000+1/2PEG20000)/PET |
| 14 | 6000，20000 | (2/3PEG6000+1/3PEG20000)/PET |
| 15 | 6000，20000 | (1/3PEG6000+2/3PEG20000)/PET |
| 16 | 2000，10000 | (1/2PEG2000+1/2PEG10000)/PET |
| 17 | 2000，10000 | (2/3PEG2000+1/3PEG10000)/PET |
| 18 | 2000，10000 | (1/3PEG2000+2/3PEG10000)/PET |
| 19 | 4000，10000 | (1/2PEG4000+1/2PEG10000)/PET |
| 20 | 4000，10000 | (2/3PEG4000+1/3PEG10000)/PET |
| 21 | 4000，10000 | (1/3PEG4000+2/3PEG10000)/PET |
| 22 | 600，4000，10000 | (1/6PEG600+1/6PEG4000+2/3PEG1000)/PET |
| 23 | 600，6000，10000 | (1/6PEG600+1/6PEG6000+2/3PEG1000)/PET |
Performance testing and characterization:
1) Copolymer morphology analysis
The morphology of the resulting samples was determined using a Scanning Electron Microscope (SEM) and the diffraction pattern at room temperature was given using an X-ray diffractometer. Typically, fig. 1A to 1C show SEM images of example 1 and diffraction patterns thereof. It can be seen that the synthesized PEG/PET samples did not show phase separation, and the copolymer morphology exhibited a uniform continuous structure. In the solid copolymer, the polarity of PET and PEG is similar, and the PET and PEG have good compatibility. The hydroxyl groups in the PEG molecules and the hydroxyl groups at the ends of the PET molecules form hydrogen bond connection, and the crystal characteristics of the PEG are maintained.
2) Thermodynamic performance measurement at atmospheric pressure
The entropy change of the phase change process of the sample was measured using a differential scanning calorimeter. Typically, FIGS. 2A-2E show the heat flow curves of the materials (PEG 6000/PET, PEG10000/PET, PEG20000/PET, (2/3 PEG4000+1/3PEG 20000)/PET, (1/2 PEG4000+1/2PEG 20000)/PET) prepared in examples 1-5 at a temperature change rate of 1K/min. At a heating rate of 1K/min, the measured heat flow curve shows that: PEG6000/PET changes phase near 329K, and the entropy change in the phase change process is calculated to be 368 J.Kg -1 ·K -1 Thermal hysteresis was 24K; PEG10000/PET changes phase around 335K, and the entropy in the phase change process is calculated to be 425.5J.Kg -1 ·K -1 Thermal hysteresis is 22K; PEG20000/PET undergoes phase transition near 327K, and the entropy of the phase transition process is calculated to be 384 J.Kg -1 ·K -1 A thermal hysteresis of 25K; the (2/3 PEG4000+1/3PEG 20000)/PET undergoes phase transition near 324K, and the entropy of the phase transition process is found to be 376 J.Kg by calculation -1 ·K -1 Thermal hysteresis 21K; the (1/2 PEG4000+1/2PEG 20000)/PET undergoes phase transition near 324K, and the entropy of the phase transition process is calculated to be 402.3 J.Kg -1 ·K -1 The thermal hysteresis was 19.7K. The material has huge phase change entropy change, but the thermal hysteresis is smaller than most of reported entropy change of more than 100 J.Kg -1 ·K -1 Giant autoclave materials (e.g., TRIS with thermal hysteresis of 75K; AMP with thermal hysteresis of 60K).
3) Measurement of the autoclave effect
The thermal flow curves and specific heats at different pressures are measured by a Differential Scanning Calorimeter (DSC) under pressure, and entropy curves at different pressures are calculated to calculate the thermal entropy change under pressure, the adiabatic temperature change under pressure, and the reversible thermal entropy change and the reversible adiabatic temperature change. Typically, FIGS. 3A-3E show the heat flow curves of examples 1-5 (PEG 6000/PET, PEG10000/PET, PEG20000/PET, (2/3PEG4000+1/3 PEG 20000)/PET, (1/2PEG4000+1/2 PEG 20000)/PET at different pressures as determined by pressure DSC.
The heat flow curve indicates that the pressure can drive the phase transition temperature toward the high temperature region. Compared with normal pressure, the pressure of 0.1GPa can lead the phase transition temperature of the PEG6000/PET heating process to be moved by about 9K, and the phase transition temperature of the cooling process to be moved by about 10K (the pressure-driven phase transition rate heating process is 87K-GPa) -1 The temperature reduction process is 101 K.GPa -1 ) The method comprises the steps of carrying out a first treatment on the surface of the The phase transition temperature of the PEG10000/PET heating process is shifted by about 9K by 0.1GPa pressure, and the phase transition temperature of the cooling process is shifted by about 10K (the pressure-driven phase transition rate heating process is 87K-GPa) -1 The temperature reduction process is 95K-GPa -1 ) The method comprises the steps of carrying out a first treatment on the surface of the The phase transition temperature of PEG20000/PET in the temperature rising process is shifted by about 10K by 0.1GPa pressure, and the phase transition temperature in the temperature lowering process is shifted by about 8K (the pressure-driven phase transition rate temperature rising process is 96K-GPa) -1 The cooling process is 76K-GPa -1 ) The method comprises the steps of carrying out a first treatment on the surface of the The pressure of 0.1GPa can lead the phase transition temperature of the (2/3 PEG4000+1/3PEG 20000)/PET heating process to be shifted by about 10K, and the phase transition temperature of the cooling process to be shifted by about 11K (the pressure-driven phase transition rate heating process is 97K-GPa) -1 The temperature reduction process is 105K-GPa -1 ) The method comprises the steps of carrying out a first treatment on the surface of the The pressure of 0.1GPa can lead the phase transition temperature of the (1/2 PEG4000+1/2PEG 20000)/PET heating process to be shifted by about 10K, and the phase transition temperature of the cooling process is shifted by about 10K (the pressure-driven phase transition rate heating process is 97K-GPa) -1 The cooling process is 104K-GPa -1 ) The phase change process of these samples was shown to be sensitive to pressure driven induction, and superior to most of the giant autoclave materials reported, for example: AMP, TRIS, PG pressure drive in cooling processThe dynamic phase transition rates are about 85+ -27, 15+ -6K-GPa, respectively -1 ，94±3K·GPa -1 The rate of AMP, TRIS, PG pressure driven phase change during the temperature rising process is about 64+/-4, 37+/-2K-GPa respectively -1 ，79±2K·GPa -1 。
According to the heat flow curves measured under different pressures in fig. 3A to 3E, entropy change curves (as shown in fig. 4A to 4E) with temperature change under different pressures are calculated, and the isothermal entropy change and the adiabatic temperature change (as shown in fig. 5 and 6) caused by the pressure are obtained by subtracting the entropy change curves by using an indirect measurement method. In the phase change process: the maximum isothermal entropy change of PEG6000/PET is about 380 J.Kg -1 ·K -1 The maximum isothermal entropy change of PEG10000/PET is about 435 J.Kg -1 ·K -1 The maximum isothermal entropy change of PEG20000/PET is about 408 J.Kg -1 ·K -1 The maximum isothermal entropy change of (2/3 PEG4000+1/3PEG 20000)/PET is about 383 J.Kg -1 ·K -1 The maximum isothermal entropy change of (1/2 PEG4000+1/2PEG 20000)/PET is about 402 J.Kg -1 ·K -1 . The maximum thermal entropy change of PEG6000/PET is about 360 J.Kg under a pressure of 0.1GPa -1 ·K -1 The maximum piezothermal entropy change of PEG10000/PET is about 400 J.Kg -1 ·K -1 The maximum piezothermal entropy change of PEG20000/PET is about 390 J.Kg -1 ·K -1 The maximum piezothermal entropy change of (2/3 PEG4000+1/3PEG 20000)/PET is about 357 J.Kg -1 ·K -1 The maximum piezothermal entropy change of (1/2 PEG4000+1/2PEG 20000)/PET is approximately 373 J.Kg -1 ·K -1 The intrinsic phase change entropy change value of the material is almost reached, which is superior to the reported thermal entropy change of many thermal materials under 0.1 GPa. To account for the hysteresis-induced irreversible entropy change, a reversible isothermal entropy change curve is calculated, as shown in fig. 7. It was found that the reversible entropy change of PEG6000/PET was about 32 J.Kg at a pressure of 0.1GPa -1 ·K -1 The reversible entropy change of PEG10000/PET is about 34 J.Kg -1 ·K -1 The reversible entropy change of PEG20000/PET is about 14 J.Kg -1 ·K -1 The reversible entropy change of (2/3 PEG4000+1/3PEG 20000)/PET is about 31 J.Kg-1.K-1, and the reversible entropy change of (1/2 PEG4000+1/2PEG 20000)/PET is about 41 J.Kg -1 ·K -1 . Giant autoclave materials which have been reported heretoforeNPG, AMP, TRIS and the like make the reversible entropy change of these materials almost zero at small pressures of 0.1GPa due to their wide thermal hysteresis and weak pressure-to-phase transition driving capability. The material in the invention has certain reversible entropy change under the small pressure of 0.1 GPa.
From the above results, it can be determined that: (1) PEG/PET (PEG molecular weight 600, 2000, 4000, 6000, 8000, 10000, 12000, 20000, PET molecular weight 15000) material has huge pressure thermal entropy change and phase change high sensitivity to pressure field, and can reach huge isothermal entropy change value and pressure thermal entropy change under small pressure. (2) For PEG/PET materials corresponding to PEG with different molecular weights, the material has a huge autoclave effect under the pressure of 0.1 GPa. Considering PEG with different molecular weights and PEG with different proportions, the thermal properties such as phase transition temperature and the like can be regulated and controlled, the PEG with proper molecular weight is selected to regulate the phase transition temperature to be near the room temperature, and the application of the piezocaloric material as a room temperature refrigerating working medium is promoted.
Claims (13)
1. The press-clamping effect material is a PEG/PET solid-solid phase change copolymer material, which comprises PET as a carrier framework material and PEG as a phase change material, wherein the mass ratio of the PET to the PEG is 1:15-25,
the preparation method of the clamp effect material comprises the following steps:
1) Respectively dissolving PEG and PET in an organic solvent to obtain a PEG solution and a PET solution;
2) Mixing the PEG solution and the PET solution according to the mass ratio of the PEG to the PET, carrying out copolymerization reaction at 180-200 ℃, and cooling to obtain the clamp effect material.
2. The pinch-effect material of claim 1, wherein hydroxyl groups in the PEG molecules form hydrogen bonding with hydroxyl groups at the ends of the PET molecules to preserve the crystalline properties of the PEG.
3. The pinch-effect material of claim 1, wherein the mass ratio of PET to PEG is 1:18-20.
4. A card pressing effect material according to any one of claims 1 to 3, wherein the molecular weight of PEG is 500-25000 and the relative molecular weight of pet is 10000-20000.
5. A pinch-effect material according to any of claims 1 to 3, wherein the entropy change of its phase change process is higher than 300 j.kg -1 ·K -1 。
6. A press-fit effect material according to any one of claims 1 to 3, wherein its 0.1GPa pressure-induced maximum isothermal entropy change is higher than 300 j.kg -1 ·K -1 。
7. A press-fit effect material according to any one of claims 1 to 3, wherein its pressure-driven phase transition rate is 76-105K-GPa -1 。
8. A method of preparing the press-fit effect material of any one of claims 1 to 7, the method comprising the steps of:
1) Respectively dissolving PEG and PET in an organic solvent to obtain a PEG solution and a PET solution;
2) Mixing the PEG solution and the PET solution according to the mass ratio of the PEG to the PET, carrying out copolymerization reaction at 180-200 ℃, and cooling to obtain the clamp effect material.
9. The preparation method according to claim 8, wherein the organic solvent in the step 1) is dimethyl sulfoxide.
10. The method of preparing according to claim 8, wherein the step 1) comprises: at 40-60 ℃, PEG and dimethyl sulfoxide are prepared into PEG solution according to the mass ratio of 1:2-5; at 180-200 ℃, PET and dimethyl sulfoxide are prepared into PET solution according to the mass ratio of 1:15-25.
11. The method of preparing according to claim 8, wherein the step 1) further comprises: drying the raw material PEG with a silica gel desiccant until the weight is constant before preparing the solution; and placing the PET in an oven, and drying at 100-120 ℃ for more than 4 hours until the weight is constant.
12. The method of preparing according to claim 8, wherein the step 2) further comprises: washing and filtering the products of the polymerization reaction, and then placing the products in a vacuum drying oven for vacuum drying for 1 to 48 hours at the temperature of 80 to 120 ℃.
13. Use of the press-fit effect material of any one of claims 1 to 7 or the press-fit effect material produced according to the production method of any one of claims 8 to 12 in a press-fit refrigeration technique.
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