CN115873256A - Crosslinked polydimethylsiloxane elastomer material and preparation method thereof - Google Patents

Abstract

The invention discloses a cross-linked polydimethylsiloxane elastomer material and a preparation method thereof. The cross-linked polydimethylsiloxane elastomer material prepared by the invention has excellent mechanical properties, multiple hydrogen bonds can be formed in hard sections of the material, the mechanical properties of the material are enhanced, the self-repairing performance is good, larger load can be borne, the application range of the material is greatly widened, and the cross-linked polydimethylsiloxane elastomer material has huge application potential in the emerging intelligent field. The raw materials are simple, can be produced and developed in large batch, can be recycled, and are expected to become products with high economic added values.

Description

A kind of cross-linked polydimethylsiloxane elastomer material and preparation method thereof

technical field

The invention belongs to the field of polymer material preparation, and in particular relates to a cross-linked polydimethylsiloxane elastomer material and a preparation method thereof.

Background technique

In recent years, with the development of the field of smart electronics, flexible electronic devices have gradually become a research hotspot in the world today. Flexible electronics technology is mainly based on flexible materials, and is a disruptive science and technology formed by the highly interdisciplinary integration of physics, chemistry, materials science and engineering, mechanics, optical engineering, biology, biomedical engineering, and basic medicine. As one of the main raw materials for making flexible electronic devices, elastomer materials play a key role in their development. As one of the main matrix materials of elastomeric materials, polydimethylsiloxane (PDMS) is widely used due to its excellent elasticity, excellent hydrophobicity, good weather resistance and excellent biocompatibility. Electronic skin, flexible wearable electronic devices, soft robots, optical devices and other fields. However, due to the low chemical bond strength of PDMS, its mechanical properties are poor, generally lower than 7MPa. The low mechanical strength makes it easy to break when subjected to external stress, making it lose its original performance and use. In response to the above problems, dynamic bonds are usually introduced into PDMS to endow the material with self-healing properties so that it can recover under specific conditions when damaged. However, the unique exchange mechanism of dynamic polymers further limits the mechanical properties of the material.

Patent CN114195972A provides a PDMS material containing benzimidazole-based dynamic covalent bonds and its preparation method and application. The strength is about 3.25MPa; the patent CN114133570A is a kind of self-reaction made from aminopropyl double-blocked polydimethylsiloxane (NH2-PDMS-NH2), diisocyanate and citric acid chloride converted from citric acid as raw materials. The repairing polysiloxane elastomer has a tensile strength of 408.2kPa; a self-repairing polysiloxane elastomer prepared by patent CN111393651A has a tensile strength of 2.8MPa.

It can be seen that the mechanical strength of self-healing PDMS materials in the prior art is generally lower than 7 MPa, so it is necessary to start from the perspective of molecular structure design to maintain its self-healing performance and improve the mechanical strength. Patent CN109265636A discloses a novel high-performance reversible covalently cross-linked polymer based on amidourea bonds and its preparation method. High mechanical strength is achieved by introducing amidourea groups into the polymer matrix. However, due to the large difference in polarity between the amidourea group and PDMS, it is difficult to find a common good solvent for hydrazide and PDMS to allow them to fully react, so as to obtain PDMS with ideal mechanical properties and self-healing function. Therefore, by rationally designing the end group structure of amidourea, it can fully react with PDMS in a certain solvent, and prepare self-healing PDMS materials with ultra-high strength. important.

Contents of the invention

In view of the above-mentioned technical problem that it is difficult to find a common good solvent for hydrazide and PDMS, the present invention explores a specific combination of hydrazide and PDMS by rationally designing the structure of the reactant, which can be dissolved in a specific solvent and fully react;

Further, aiming at the technical problem that there is no ultra-high strength self-healing PDMS material in the above-mentioned prior art, the present invention rationally designs and proposes a preparation method of a cross-linked polydimethylsiloxane elastomer material. While maintaining good self-healing performance, the mechanical properties of self-healing PDMS have been greatly improved, and its tensile strength can reach 17.2MPa, and its elastic modulus can reach 20.4MPa. Among them, the tensile strength of the material has increased by about two times compared with various self-healing PDMS materials in published articles and patents in the world, which is an unexpected increase. In addition, the material is 80% self-healing efficient. This invention greatly expands the scope of use of PDMS.

A preparation method of a cross-linked polydimethylsiloxane elastomer material, comprising:

dissolving the isocyanate group-containing compound and the siloxane matrix compound in a reaction solvent, and reacting for a period of time under heating conditions to obtain a precursor;

Add an amino chain extender to the precursor, stir and react at room temperature for a period of time, and place it in an oven to volatilize and remove the solvent after the solid reaction is complete, to obtain a colorless and transparent cross-linked polydimethylsiloxane elastomer material.

The cross-linked polydimethylsiloxane elastomer material prepared by the present invention can be made into fine PDMS particles by mechanical crushing or manual cutting, and then processed by hot pressing, extruding, injection molding or 3D printing to make a material with specific shape and performance. Material.

Further, the compound containing isocyanate group is tetramethyl m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, hexa One or more of methylene diisocyanate trimers.

Further, the siloxane base compound is hydroxyl-terminated siloxane materials or one or more of hydroxyl-terminated siloxane materials with different molecular weights.

Further, the different molecular weights are 1000-5000.

Further, the chain extender is one or more of amino-containing compounds, aldehyde-containing compounds, disulfide-containing compounds, and hydrazide-containing compounds.

Further, the amino-containing compound is isophorone diamine, diacetylm-phenylenediamine, N,N-dialkylmethyldiamine, diethyltoluenediamine, diacetylethylenediamine, dioxane One or more of methyl toluene diphenylamine

Further, the compound containing aldehyde group is 5-bromoisophthalaldehyde, pyridine-2,6-dicarbaldehyde, glutaraldehyde, succinaldehyde, phthalaldehyde, trialdehyde phloroglucinol, m- One or more of phthalaldehyde and terephthalaldehyde.

Further, the disulfide-containing compound is 4,4'-diaminodiphenyl disulfide, 2,2'-diaminodiphenyl disulfide and 3,3'-dithiodipropionic acid diacyl One or more of hydrazine.

Further, the hydrazide-containing compound is one or more of oxalic hydrazide, adipic hydrazide and terephthalic hydrazide.

Further, the reaction solvent is one or more of hexane, dioxane, tetrahydrofuran, N,N-dimethylformamide, and dimethyl sulfoxide.

Further, the heating condition is heating at 60-100° C. for 6-12 hours.

Further, the evaporation temperature of the solvent is 80°C.

The invention also discloses a cross-linked polydimethylsiloxane elastomer material prepared by any one of the above preparation methods.

Further, the tensile strength of the cross-linked polydimethylsiloxane elastomer material is 12.8-18.6 MPa, and the elongation at break is 160-330%.

Further, in terms of tensile strength, the cross-linked polydimethylsiloxane elastomer material has a reprocessing efficiency of 98.2% at 130° C. for 10 minutes.

Further, in terms of toughness, the repair efficiency of the cross-linked polydimethylsiloxane elastomer material reaches 80.2% after self-repair at 140° C. for 3 hours.

The beneficial effects of the present invention are:

1) The present invention reacts with several different diisocyanates and polydimethylsiloxanes with different molecular weight terminal hydroxypropyl di-blocks under heating conditions to generate a prepolymer, and then adds a stoichiometric chain extender for further reaction, The produced groups can not only endow the material with self-healing properties, but also form multiple hydrogen bonds between molecules to increase the mechanical properties of the material.

2) The cross-linked polydimethylsiloxane elastomer material prepared by the present invention overcomes the problem that the polarity gap between the siloxane as the soft segment and the hard segment amidurea is too large and cannot fully react. The compatibility between the hard segment and the soft segment is good, so that the siloxane soft segment can be well interspersed in the hard segment.

3) The present invention does not need to use a catalyst, and the materials used can be purchased conveniently. The synthesis process is simple, and industrial production is expected to be realized.

4) The cross-linked polydimethylsiloxane elastomer material prepared by the present invention has excellent mechanical properties, and its hard segment can form multiple hydrogen bonds to enhance the mechanical properties of the material. The tensile strength is 12.8-18.6 MPa, and the fracture The elongation is 160-330%, and the elastic modulus is 20.4-64.5MPa.

5) The cross-linked polydimethylsiloxane elastomer material prepared by the present invention not only has high mechanical properties, but also has good self-repair performance. After self-repair at 140°C for 3 hours, the repair efficiency reaches 80.2%. .

6) The cross-linked polydimethylsiloxane elastomer material prepared by the present invention realizes the combination of excellent mechanical properties and self-repairing ability, can bear larger loads, and greatly expands the use range of materials. It has great application potential in the field of intelligence.

Description of drawings

Fig. 1 is embodiment 1 (abbreviated TM-A-C15) and comparative example 1 (abbreviated IP-A-C15), the reaction schematic diagram of comparative example 2 (abbreviated HM-A-C15);

Fig. 2 is the self-repair principle diagram of embodiment 1 (TM-A-C15 for short);

Fig. 3 is the infrared spectrogram of embodiment 1 (abbreviation TM-A-C15);

Fig. 4 is the stress-strain curve of embodiment 1 (abbreviation TM-A-C15) spline;

Fig. 5 is the stress-strain curve of embodiment 1 (TM-A-C15 for short) after self-repairing at different temperatures;

Fig. 6 is the photos before and after self-repairing of Example 1 (abbreviated as TM-A-C15) at 130°C;

Fig. 7 is the stress-strain-curve of the reworked spline and the self-repaired spline of Comparative Example 1 (IP-A-C15 for short);

Fig. 8 is the stress-strain-curve of the reworked spline and the self-repaired spline of Comparative Example 2 (referred to as HM-A-C15).

Detailed ways

The specific technical solutions of the present invention are described in conjunction with the examples.

Example 1

A preparation method of cross-linked polydimethylsiloxane elastomer material, comprising the following preparation steps:

The preparation of precursor: precursor is tetramethyl m-xylylene diisocyanate (TMXDI, 2.125g, 8.7mmol) and cross-linking agent hexamethylene diisocyanate trimer (tri-HDI) (0.436g , 0.87mmol) was dissolved in 20ml dimethylacetamide and stirred to make it fully dissolved and dispersed, and then the corresponding hydroxypropyl-terminated polysiloxane was added according to the molar ratio of isocyanate and hydroxyl group of 2:1, and placed In an oil bath at 80°C, stir for 8 hours to form a precursor.

Preparation of polydimethylsiloxane elastomer (TM-A-C15 for short): Add stoichiometric amount of adipic acid dihydrazide (0.871g, 5mmol) to the above-mentioned reacted precursor, and stir at room temperature for 30min , when the adipic acid dihydrazide solid disappears, the product is placed in an oven at 80°C to evaporate the solvent, and after 12-24 hours, a transparent film is obtained.

The self-healing polysiloxane elastomer (TM-A-C15) with excellent mechanical properties obtained in this example has a tensile strength of 17.2MPa, an elongation at break of 264.64%, and a modulus of elasticity of 20.3MPa. Toughness meter, the self-healing efficiency of self-healing for 3 hours at 140°C is 80%.

Comparative example 1

The preparation of precursor: precursor is that isophorone diisocyanate (IPDI, 1.934g, 8.7mmol) and cross-linking agent hexamethylene diisocyanate trimer (tri-HDI) (0.436g, 0.87mmol) dissolve Stir in 20ml of dimethylacetamide to fully dissolve and disperse, then add the corresponding hydroxypropyl-terminated polysiloxane according to the molar ratio of isocyanate and hydroxyl group of 2:1, and place it in an 80°C oil bath In the pot, stir the reaction for 8h to form the precursor.

Preparation of polydimethylsiloxane elastomer (abbreviated as IP-A-C15): Add stoichiometric amount of adipate dihydrazide (0.871g, 5mmol) to the above-mentioned reacted precursor, and stir at room temperature for 30min , when the adipic acid dihydrazide solid disappears, the product is placed in an oven at 80°C to evaporate the solvent, and after 12-24 hours, a transparent film is obtained.

The polysiloxane elastomer (abbreviated IP-A-C15) that this comparative example makes has higher mechanical strength, and its tensile strength is 16.27MPa, and elongation at break is 139.66%, and elastic modulus is 79.88MPa, However, its self-healing ability is sacrificed. Under the action of mechanical force, 140°C, 15MPa, 1 hour processing, the repair efficiency can reach 96% in terms of tensile strength.

Comparative example 2

Preparation of precursor: the precursor is 4,4'-dicyclohexylmethane diisocyanate (HMDI, 2.282g, 8.7mmol) and crosslinking agent hexamethylene diisocyanate trimer (tri-HDI) (0.436g , 0.87mmol) was dissolved in 20ml dimethylacetamide and stirred to make it fully dissolved and dispersed, and then the corresponding hydroxypropyl-terminated polysiloxane was added according to the molar ratio of isocyanate and hydroxyl group of 2:1, and placed In an oil bath at 80°C, stir for 8 hours to form a precursor.

Preparation of polydimethylsiloxane elastomer (referred to as HM-A-C15): Add stoichiometric amount of adipic acid dihydrazide (0.871g, 5mmol) to the precursor after the above reaction, and stir at room temperature for 30min , when the adipic acid dihydrazide solid disappears, the product is placed in an oven at 80°C to evaporate the solvent, and after 12-24 hours, a transparent film is obtained.

The polysiloxane elastomer (being called for short HM-A-C15) that this comparative example makes has best mechanical performance, and its tensile strength is 18.21MPa, and elongation at break is 87.9%, and elastic modulus is 32.59MPa, But hard to fix.

Fig. 1 is the schematic diagram of the reaction principle of embodiment 1 and comparative example 1 and comparative example 2. The method includes first reacting a reactant containing an isocyanate group with a hydroxypropyl-terminated polysiloxane to form a precursor, and then adding a chain extender ADH to form a polydimethylsiloxane elastomer material with high mechanical strength.

Figure 2 is the self-healing mechanism diagram of Example 1. At high temperature, the amidourea group in the material will undergo dynamic dissociation and recombination to form isocyanate and hydrazide, and the amidourea group will be re-formed after cooling.

Fig. 3 is the infrared spectrogram of Example 1, there is no peak at 2250cm ^-1 in the figure, indicating that the NCO group has reacted completely.

Fig. 4 is the stress-strain curve of embodiment 1, can understand the mechanical property of embodiment 1 from the figure: tensile strength is 17.2MPa, elongation at break is 264.64%, and elastic modulus is 20.3MPa.

Figure 5 is the stress-strain curves of Example 1 after self-healing at different temperatures. It can be seen that the self-healing efficiency of TM-A-C15 at 140° C. for 3 hours is 80%.

Figure 6 is the photos before and after the self-repair of Example 1, it can be seen that the gap is completely repaired.

Fig. 7 is the stress-strain-curve of the spline after the heavy processing of comparative example 1 (being called for short IP-A-C15) and the spline after self-repairing, it can be seen that the material synthesized by IPDI has higher modulus of elasticity amount, but the self-repair efficiency is low, and only reprocessing experiments can be carried out.

Fig. 8 is the stress-strain-curve of the spline after the heavy processing of comparative example 2 (being called for short HM-A-C15) and the spline after self-repairing, it can be seen that the material synthesized by HPDI has higher tensile strength Strength, but low self-repair efficiency and low reprocessing efficiency.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. A preparation method of cross-linked polydimethylsiloxane elastomer material, comprising: dissolving the isocyanate group-containing compound and the siloxane matrix compound in a reaction solvent, and reacting for a period of time under heating conditions to obtain a precursor solution; Add an amino chain extender to the precursor solution, stir at room temperature until the solid reacts completely, and then put it in an oven to volatilize the solvent to obtain a crosslinked polydimethylsiloxane elastomer material. 2. The preparation method according to claim 1, wherein: The isocyanate group-containing compound is tetramethyl m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, hexamethylene One or more of diisocyanate trimers. 3. The preparation method according to claim 1, wherein: The siloxane base compound is hydroxyl-terminated siloxane materials or one or more of hydroxyl-terminated siloxane materials with different molecular weights. 4. The preparation method according to claim 3, wherein: The different molecular weights are 1000-5000. 5. The preparation method according to claim 1, wherein: The heating condition is: heating at 60-100° C. for 6-12 hours. 6. The preparation method according to claim 1, wherein: The amino chain extender is one or more of amino-containing compounds, aldehyde-containing compounds, disulfide-containing compounds, and hydrazide-containing compounds. 7. The preparation method according to claim 6, wherein: The amino-containing compound is isophorone diamine, diacetyl m-phenylenediamine, N,N-dialkylmethyldiamine, diethyltoluenediamine, diacetylethylenediamine, dialkyltoluene diamine One or several kinds of aniline; The aldehyde group-containing compound is 5-bromoisophthalaldehyde, pyridine-2,6-dicarbaldehyde, glutaraldehyde, succinic dialdehyde, phthalaldehyde, trialdehyde phloroglucinol, resorcinol One or more of formaldehyde and terephthalaldehyde; The disulfide-containing compound is 4,4'-diaminodiphenyl disulfide, 2,2'-diaminodiphenyl disulfide and 3,3'-dithiodipropionic acid dihydrazide one or several; The hydrazide-containing compound is one or more of oxalic hydrazide, adipic hydrazide and terephthalic hydrazide. 8. The preparation method according to claim 1, wherein: The reaction solvent is one or more of hexane, dioxane, tetrahydrofuran, N, N-dimethylformamide, and dimethyl sulfoxide. 9. The preparation method according to claim 1, wherein: The evaporation temperature of the solvent is 80°C. 10. A cross-linked polydimethylsiloxane elastomer material prepared according to any one of the preparation methods of claims 1-9.

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