阅读说明：本技术 一种褶皱聚合物发泡材料及其制备方法 (Folded polymer foam material and preparation method thereof ) 是由 米皓阳 董斌斌 王亚蒙 刘春太 于 2021-07-08 设计创作，主要内容包括：本发明涉及聚合物发泡材料技术领域,具体涉及一种褶皱聚合物发泡材料及其制备方法。本发明制备方法,提出创新褶皱泡沫结构的形成机理,利用动态超临界流体发泡技术,基于聚合物在流场中的“流致取向”效应和内应力的生成与释放机理,实现一步法成型具备褶皱泡孔结构的聚合物泡沫材料。该方法工艺简单、成本低、环保且制品尺寸可依据需求调整,灵活性高；本发明制备的发泡材料,表面和泡孔内部富集褶皱结构,具有优异力学性能,在缓冲、吸能等方面具有很好的应用前景,在防伪、自清洁、催化、结构色等众多领域有着巨大的应用潜力。(The invention relates to the technical field of polymer foam materials, in particular to a folded polymer foam material and a preparation method thereof. The preparation method of the invention provides an innovative forming mechanism of the wrinkle foam structure, and utilizes a dynamic supercritical fluid foaming technology to realize one-step forming of the polymer foam material with the wrinkle cell structure based on the 'flow-induced orientation' effect of the polymer in a flow field and the generation and release mechanism of internal stress. The method has the advantages of simple process, low cost, environmental protection, adjustable product size according to requirements and high flexibility; the foam material prepared by the invention has the advantages that the surface and the inside of the foam hole are enriched with the fold structure, the foam material has excellent mechanical property, has good application prospect in the aspects of buffering, energy absorption and the like, and has great application potential in a plurality of fields such as anti-counterfeiting, self-cleaning, catalysis, structural color and the like.)

1. A preparation method of a folded polymer foaming material is characterized by comprising the steps of carrying out flow field treatment and rapid pressure relief foaming on the polymer material by adopting a supercritical fluid; the method specifically comprises the steps of sequentially filling supercritical fluid to set pressure, soaking the polymer material by the supercritical fluid, dynamically filling and discharging the supercritical fluid, and rapidly releasing pressure and discharging the supercritical fluid; wherein dynamically charging and discharging the supercritical fluid comprises discharging the supercritical fluid at a set rate while maintaining the charging of the supercritical fluid and maintaining a set pressure within the foaming reactor.

2. A method of producing a pleated polymer foam material according to claim 1, wherein the polymer material is a polymer sheet material; the method also comprises heating the polymer sheet material to a foaming temperature in a foaming reaction kettle before carrying out the flow field treatment on the polymer sheet material.

3. A method for preparing a pleated polymer foam material according to claim 2, wherein the soaking pressure of the supercritical fluid soaking the polymer sheet material is 12 to 25 MPa.

4. A method of producing a pleated polymer foam according to claim 3, wherein the pressure in the foaming reaction vessel is maintained to maintain the soaking pressure during the dynamic charging and discharging of the supercritical fluid.

5. A method for preparing a pleated polymer foam according to claim 4, wherein the discharge rate of the supercritical fluid during the dynamic charging and discharging of the supercritical fluid is 5 to 50 ml/s.

6. A method for preparing a pleated polymer foam according to claim 5, wherein the duration of the dynamic charging and discharging of the supercritical fluid is 10 to 30 min.

7. A method for preparing a pleated polymer foam material according to claims 1 to 6, wherein the supercritical fluid soaks the polymer material to fully dissolve the supercritical fluid in the polymer material to a saturated state; the soaking time is 1-4 h.

8. A process for the preparation of a pleated polymer foam according to any of claims 1 to 6, wherein the supercritical fluid is supercritical CO₂。

9. A method for preparing a pleated polymer foam material according to any one of claims 1 to 6, wherein the polymer material is prepared by vacuum hot-pressing polymer pellets; the polymer material is selected from polyurethane material, polycaprolactone material or polyvinylidene fluoride material.

10. A pleated polymer foam material prepared by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of polymer foam materials, in particular to a folded polymer foam material and a preparation method thereof.

Background

In recent years, the light weight of the polymer has become an important task for the development of national ' energy conservation and emission reduction ' and ' plastic limitationThe urgent need to be met. The polymer foam is an important polymer material with light weight and good barrier and buffer properties, is widely applied to daily production, life, military industry and aviation fields, and plays an irreplaceable role in human production and life. The preparation of novel multifunctional and high-performance polymer foam materials has become a current research focus and attracts the attention of numerous researchers. Generally, the cells inside the foamed article are formed by the generation or addition of some gas from the plastic raw material during the forming process. Supercritical fluids (e.g., supercritical CO)₂(scCO₂) The foaming technology has become the first choice technology for producing thermoplastic polymers and composite foaming materials thereof due to the advantages of high efficiency, environmental protection, low cost, wide applicability and the like. However, the mechanical properties of foamed articles are largely influenced by cell size, density, distribution and morphology, structural parameters, supercritical fluids (e.g., scCO)₂) The cells obtained by foaming are mostly spherical or polygonal structures of several microns to tens of microns, and the further regulation and control of the microscopic cell morphology and even the polymer aggregation state structure of the foaming material are very difficult, which limits the performance limit and the application range of the foaming material to a great extent.

It is well known that how to precisely regulate and control the microstructure morphology in the polymer forming and processing process is the key to prepare multifunctional and high-performance polymers. In recent years, in the process of polymer forming, through the coupling regulation of different processing fields and the introduction of unconventional processing external fields (strong flow, strong pressure, dynamic field and the like), high performance and functionalization of materials can be successfully realized by optimizing and regulating the aggregation state structure of the polymer without changing the chemical structure of the polymer, and the research and development of the unconventional processing forming technology become research hotspots in the fields of polymer science and polymer processing engineering. Therefore, the innovative preparation technology of the polymer foaming material based on the dynamic forming technology is expected to realize the jump and functionalization of the performance of the polymer foaming material. The development of a dynamic supercritical fluid microcellular foaming technology which is suitable for various polymer materials, is easy to control and is suitable for industrial production, the microcellular structure of the foaming material is accurately regulated, the mechanical property of the foaming material is improved, and the polymer foaming material with standardized comprehensive properties is produced, so that the technical problem which needs to be solved at present is formed.

Disclosure of Invention

In order to overcome the defects of the prior art, one of the objectives of the present invention is to provide a method for preparing a pleated polymer foam material, wherein a supercritical fluid is controlled to be in a flowing state during a foaming gas soaking process, so as to generate a shearing effect, and promote polymer molecular chain orientation to form internal stress. Further, through rapid pressure relief foaming, the polymer expands due to the difference between internal pressure and external pressure, the internal stress of the polymer is released to induce the molecular chain to change to a random coil state, so that uniform wrinkle structures are formed on the surface of the polymer foaming material and in the foam cells, and the polymer wrinkle foam with a unique micron-sized uniform wrinkle structure is prepared.

Meanwhile, the invention also provides a folded polymer foam material which is prepared by the preparation method provided by the invention, has a unique micron-sized uniform folded structure, is remarkably improved in compression performance and recovery performance, and is expected to be applied to various fields such as energy absorption, buffering, blocking, self-cleaning, heat insulation, electromagnetic shielding, anti-counterfeiting and the like.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a folded polymer foaming material comprises the steps of carrying out flow field treatment and rapid pressure relief foaming on the polymer material by adopting a supercritical fluid; specifically, the method sequentially comprises the following steps: filling supercritical fluid to set pressure, soaking the polymer sheet material with the supercritical fluid, dynamically filling and discharging the supercritical fluid, and rapidly releasing pressure and discharging the supercritical fluid; wherein dynamically charging and discharging the supercritical fluid comprises discharging the supercritical fluid at a set rate while maintaining the charging of the supercritical fluid and maintaining a set pressure within the foaming reactor. In the specific embodiment of the invention, supercritical fluid is adopted in a foaming reaction kettle to carry out flow field treatment and rapid pressure relief foaming on the polymer material; further preferably, after the supercritical fluid is rapidly discharged by pressure relief, the polymer material is rapidly taken out of the foaming reactor and naturally cooled.

Further, the polymer material is a polymer sheet material; the method also comprises heating the polymer sheet material to a foaming temperature in a foaming reaction kettle before foaming the polymer sheet material.

Preferably, the soaking pressure of the supercritical fluid for soaking the polymer sheet material is 12-25 MPa.

Further, the immersion pressure is maintained by maintaining the pressure during the dynamic charging and discharging of the supercritical fluid.

Optionally, the supercritical fluid discharge rate in the dynamic charging and discharging process of the supercritical fluid is 5-50 ml/s.

Optionally, the duration of the dynamic supercritical fluid charging and discharging process is 10-30 min.

Optionally, the supercritical fluid soaks the polymer sheet material until the polymer sheet material is fully dissolved in the supercritical fluid to a saturated state; further, the soaking time is 1-4 h.

Optionally, the supercritical fluid is supercritical CO₂。

Optionally, the polymer sheet material is prepared by vacuum hot pressing of polymer granules; the polymer sheet material is selected from a polyurethane material, a polycaprolactone material or a polyvinylidene fluoride material.

A folded polymer foam material is prepared by the preparation method.

Different from the traditional foaming forming processing technology, the preparation method provided by the invention adopts the foaming treatment to the polymer sheet in the dynamic supercritical fluid environment, the flow of the supercritical fluid generates the shearing effect to the polymer sheet, and the equilibrium state of the saturated blending system formed by the polymer/supercritical fluid is broken. When the supercritical fluid flows through the polymer chain in a high elastic state or viscous state, the molecular chain generates a flow induced orientation effect under the action of the flow field, namely the supercritical fluid flow field enables the polymer chain in a random linear block shape to generate S-shaped affine deformation along the flow field direction, and the supercritical fluid flow field applies work to the molecular chain to reduce the system entropy so as to form internal stress. Then, during rapid pressure relief foaming, the polymer chains are subjected to a more complex action: comprises the stretching action of the polymer on a molecular chain under the condition of rapid expansion under the condition of internal and external pressure difference and the retraction action of the polymer when the internal stress of the molecular chain is released. Therefore, when the flow field of the dynamic supercritical fluid is removed and the rapid pressure relief foaming process is carried out simultaneously, the internal stress release in the polymer material and the expansion of the cells in the rapid pressure relief foaming process are cooperated, so that a folded microstructure is generated on the basis of the cell structure, and the preparation of the folded foam material is realized.

The invention has the beneficial effects that:

1. the surface wrinkle structure is generally obtained by treating a composite material having a double-layer structure by a chemical solvent swelling method, an external force method, a thermal induction method, and the like, and the wrinkle structure is limited to the surface of the material. There is currently no effective way to produce a pleated structure inside the cells. The invention provides a novel wrinkle foam preparation method, which utilizes a dynamic supercritical fluid foaming technology, and based on the 'flow-induced orientation' effect and the internal stress generation/release mechanism of a polymer in a flow field, realizes one-step preparation of a foaming material with a micron-sized wrinkle structure, and has the advantages of simple preparation process, low cost, environmental protection, adjustable product size according to requirements and high flexibility;

2. the wrinkled polymer foam material provided by the invention has the advantages that the surface and the inside of the foam hole are enriched with wrinkled structures, the mechanical property is excellent, the application prospect is good in the aspects of buffering, energy absorption and the like, and the wrinkled polymer foam material has great application potential in various fields such as anti-counterfeiting, self-cleaning, catalysis, structural color and the like.

Drawings

FIG. 1 is a surface SEM image of a Thermoplastic Polyurethane (TPU) pleated foam prepared in example 1;

FIG. 2 is a partial SEM magnified view of the surface of a Thermoplastic Polyurethane (TPU) pleated foam prepared in example 1;

FIG. 3 is a partial SEM magnified view of cells of a Thermoplastic Polyurethane (TPU) pleated foam prepared in example 1;

FIG. 4 is a partial SEM magnified view of cells of a Polycaprolactone (PCL) creased foaming material prepared in example 2;

FIG. 5 is a partial SEM magnified view of cells of a polyvinylidene fluoride (PVDF) pleated foam prepared in example 3;

FIG. 6 is a partial SEM enlarged view of cells of a Thermoplastic Polyurethane (TPU) foam prepared in comparative example 1

FIG. 7 is a partial SEM enlarged view of cells of a polyvinylidene fluoride (PVDF) foam prepared in comparative example 2.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The equipment and reagents used in the examples and the experimental examples were commercially available except as specifically indicated.

Example 1

The embodiment provides a Thermoplastic Polyurethane (TPU) fold foaming material, and the preparation method thereof comprises the following specific operation steps:

s1, preparing a thermoplastic polyurethane sheet material

Placing the fully dried polyurethane granules in a template of a vacuum hot press, carrying out vacuum hot pressing for 5min at 160 ℃, and demolding to obtain a thermoplastic polyurethane sheet material;

s2. dynamic scCO₂Foaming method for preparing fold foam material

Placing the Thermoplastic Polyurethane (TPU) sheet material prepared in step S1 into a dynamic scCO₂In the foaming reaction kettle, the temperature inside the foaming reaction kettle is accurately regulated and controlled to 110 ℃ by using a temperature control system, and supercritical CO is supplied by a supercritical fluid supply system₂(scCO₂) Injecting the mixture into a foaming reaction kettle to achieve the soaking pressure of 20MPa, and fully dissolving the ScCO in the thermoplastic polyurethane sheet material after soaking for 2 hours₂To reach a saturated state; after stabilization, the release needle valve switch is regulated and controlled to drive the scCO in the foaming reaction kettle₂Flow at 38ml/s (CO at atmospheric pressure)₂Gas volume calibration); maintenance of scCO₂Continuously flowing for 20min, and simultaneously keeping the pressure of the gas supply system at 20MPa, namely continuously supplying gas in the kettle by the gas supply system to maintain a high-pressure environment; finally, the admission valve is closed and the scCO is stopped₂The pressure relief valve is quickly and completely opened, so that the air pressure in the foaming reaction kettle is quickly relieved to the atmospheric pressure within a very short time, and the material is foamed; then opening the foaming reaction kettle, and taking a sampleAnd naturally cooling to room temperature to prepare the thermoplastic polyurethane wrinkle foam material with the wrinkle cell microstructure.

And (3) characterizing a fold structure: an SEM image of the thermoplastic polyurethane pleated foam prepared in this example as shown in fig. 1; FIG. 2 is an enlarged view of a partial surface of FIG. 1, showing the surface corrugation structure of the thermoplastic polyurethane corrugated foam material prepared in this example; FIG. 3 is a partially enlarged view of FIG. 1 showing that the thermoplastic polyurethane pleated foam material prepared in this example forms a cell pleat structure.

Example 2

The embodiment provides a Polycaprolactone (PCL) folded foaming material, and the preparation method comprises the following specific operation steps:

s1, preparing Polycaprolactone (PCL) sheet material

Placing the fully dried PCL granules in a template of a vacuum hot press, carrying out vacuum hot pressing for 8min at 100 ℃, and demolding to obtain a PCL sheet material;

s2. dynamic scCO₂Foaming method for preparing fold foam material

Placing PCL sheet material into dynamic scCO₂In the foaming reaction kettle, the temperature control system is utilized to accurately regulate and control the internal temperature of the foaming reaction kettle to reach 50 ℃ in advance, and the SCCO is supplied by the supercritical fluid supply system₂Injecting into a foaming reaction kettle to reach a soaking pressure of 12MPa, and soaking for 2.5 hours to fully dissolve the SCL₂To reach a saturated state; after stabilization, the release needle valve switch is regulated and controlled to drive the scCO in the foaming reaction kettle₂Flowing at 25ml/s (CO at atmospheric pressure)₂Gas volume calibration); maintenance of scCO₂Continuously flowing for 15min, and keeping the pressure of the gas supply system at 12MPa, namely continuously supplying gas in the kettle by the gas supply system to maintain a high-pressure environment; finally, the admission valve is closed and the scCO is stopped₂The pressure relief valve is quickly and completely opened, so that the air pressure in the foaming reaction kettle is quickly relieved to the atmospheric pressure within a very short time, and the material is foamed; and opening the foaming reaction kettle, taking out the sample, and naturally cooling to room temperature to prepare the PCL fold foaming material with the fold cellular microstructure.

And (3) characterizing a fold structure: fig. 4 is a partial SEM image of PCL pleated foaming material prepared in this example, showing that it has a cell pleated structure.

Example 3.

The embodiment provides a polyvinylidene fluoride (PVDF) pleated foam material, and the preparation method comprises the following specific operation steps:

s1, preparing polyvinylidene fluoride (PVDF) sheet material

Putting the fully dried PVDF granules into a template of a vacuum hot press, then putting the template into a die cavity, carrying out vacuum hot pressing for 5min at 180 ℃, and demoulding to obtain a PVDF sheet material;

s2. dynamic scCO₂Foaming method for preparing fold foam material

Placing PVDF sheet material into dynamic scCO₂In the foaming reaction kettle, the temperature control system is utilized to accurately regulate and control the internal temperature of the foaming reaction kettle to 166 ℃, and the SCCO is supplied to the foaming reaction kettle through the supercritical fluid supply system₂Injecting the mixture into a foaming reaction kettle to achieve the soaking pressure of 16MPa, and fully dissolving the scCO by the PVDF after soaking for 3 hours₂To reach a saturated state; after stabilization, the release needle valve switch is regulated and controlled to drive the scCO in the foaming reaction kettle₂Flow at 10ml/s (CO at atmospheric pressure)₂Gas volume calibration); maintenance of scCO₂Continuously flowing for 15min, and keeping the pressure of the gas supply system at 16MPa, namely continuously supplying gas in the kettle by the gas supply system to maintain a high-pressure environment; finally, the admission valve is closed and the scCO is stopped₂The pressure relief valve is quickly and completely opened, so that the air pressure in the foaming reaction kettle is quickly relieved to the atmospheric pressure within a very short time, and the material is foamed; and opening the foaming reaction kettle, taking out the sample, and naturally cooling to room temperature to prepare the PVDF folded foaming material with the folded cellular microstructure.

And (3) characterizing a fold structure: FIG. 5 is a partial SEM image of a PVDF pleated foam prepared in this example, showing that the PVDF foam has a pleated structure of cells.

Comparative example 1.

The comparative example provides a thermoplastic polyurethane foam material, and the preparation method comprises the following specific operation steps:

s1, preparing a Thermoplastic Polyurethane (TPU) sheet material

Putting the fully dried TPU granules into a template of a vacuum hot press, then putting the template into a die cavity, carrying out vacuum hot pressing for 5min at 160 ℃, and demoulding to obtain a TPU sheet material;

s2. dynamic scCO₂Foaming method for preparing fold foam material

Placing the TPU prepared in step S1 into a dynamic scCO₂In the foaming reaction kettle, the temperature inside the foaming reaction kettle is accurately regulated and controlled to 110 ℃ by using a temperature control system, and supercritical fluid CO is supplied by a supercritical fluid supply system₂(scCO₂) Injecting the mixture into a foaming reaction kettle to achieve the soaking pressure of 20MPa, and fully dissolving the ScCO in the thermoplastic polyurethane sheet material after soaking for 2 hours₂To reach a saturated state; close the inlet valve, stop scCO₂The pressure relief valve is quickly and completely opened, so that the air pressure in the foaming reaction kettle is quickly relieved to the atmospheric pressure within a very short time, and the material is foamed; and then opening the foaming reaction kettle, taking out the sample, and naturally cooling to room temperature to obtain the thermoplastic polyurethane foaming material.

Structural characterization: FIG. 6 is a partial SEM image of the thermoplastic polyurethane foam prepared in the present comparative example, which shows that the prepared foam has smooth cell walls and no wrinkle structure.

Comparative example 2

The comparative example provides a polyvinylidene fluoride (PVDF) foam material, and the preparation method comprises the following specific operation steps:

s1, preparing polyvinylidene fluoride (PVDF) sheet material

Putting the fully dried PVDF granules into a template of a vacuum hot press, then putting the template into a die cavity, carrying out vacuum hot pressing for 5min at 180 ℃, and demoulding to obtain a PVDF sheet material;

s2. dynamic scCO₂Foaming method for preparing fold foam material

Placing PVDF sheet material into dynamic scCO₂In the foaming reaction kettle, the temperature control system is utilized to accurately regulate and control the internal temperature of the foaming reaction kettle to reach pre-166 ℃, and the SCCO is supplied by the supercritical fluid supply system₂Injecting the mixture into a foaming reaction kettle to achieve the soaking pressure of 16MPa, and fully dissolving the scCO by the PVDF after soaking for 3 hours₂To reach saturationA state; close the inlet valve, stop scCO₂The pressure relief valve is quickly and completely opened, so that the air pressure in the foaming reaction kettle is quickly relieved to the atmospheric pressure within a very short time, and the material is foamed; and then opening the foaming reaction kettle, taking out the sample, and naturally cooling to room temperature to obtain the PVDF foam material.

The structural characterization is shown in fig. 7, which is a partial SEM image of the PVDF foam prepared in the present comparative example, and shows that the cell walls of the cells of the foam prepared in the present comparative example are smooth and have no wrinkle structure.

Performance comparison test:

1. and (3) microstructure comparison:

comparing the difference of the cell structures of the TPU foamed materials prepared in the example 1 and the comparative example 1 and the difference of the cell structures of the PVDF foamed materials prepared in the comparative example 3 and the comparative example 2 respectively, the invention shows that compared with the traditional supercritical fluid static soaking foaming process method, the invention adopts the dynamic supercritical fluid foaming process method to prepare the polymer foamed material with the fold structure;

meanwhile, the structure characterization results of the embodiments 1 to 3 prove that the preparation method is suitable for preparing various common polymer material wrinkle foams, and the wrinkle structures of the surfaces and the foam cells of the wrinkle foams prepared from the thermoplastic polyurethane with high elasticity are most obvious.

2. Mechanical property comparison test:

the test method comprises the following steps: the cyclic compression performance of the TPU creased foam made in example 1 and the TPU conventional non-creased foam made in comparative example 1 were compared. The cyclic compression performance adopts that the compression rate and the recovery rate are both 1mm/min, and the compression strain is 50 percent. The material was tested for compression modulus, deformation recovery and energy absorption.

TABLE 1

The mechanical property results are shown in table 1, and compared with the conventional TPU foam, the TPU creased foam prepared by the dynamic supercritical fluid foaming process method of the present invention has a reduced tensile modulus due to the elongation of the creased structure during the stretching process. The compression modulus, the recovery rate and the energy absorption of the foam are obviously improved, and the wrinkle structure prepared by the method plays a huge role in buffering and storing energy when the foam is compressed. The application potential of the pleated foam prepared by the process method is shown in the aspects of buffering, energy absorption and the like.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.