A recyclable polyurea-polydimethylsiloxane elastomer material and preparation method thereof

Abstract

The invention discloses a recyclable polyurea-polydimethylsiloxane elastomer material and a preparation method thereof, 100 parts by weight of polydimethylsiloxane, 8-12 parts by weight of diisocyanate, 6-8 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane are mixed in an ice-water bath, and polyurea-polydimethylsiloxane uncured raw materials are obtained, and then 5-7 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine are added to mix with the raw materials, and cured by oven heating to obtain an elastomer with excellent mechanical properties. The present invention uses dynamic silyl ether bonds as cross-linking bonds of an elastomer curing network, so that the material has recycling performance, and the high bond energy of the silyl ether bonds also enables the polydimethylsiloxane elastomer material to retain excellent heat resistance.

Description

Technical Field

[0001] The invention belongs to the field of elastomeric materials, and more specifically, relates to a recyclable polyurea-polydimethylsiloxane elastomeric material and a preparation method thereof. Background Art

[0002] As an important member of high-performance synthetic elastomers, polydimethylsiloxane (PDMS) elastomer materials have an irreplaceable position in modern high-tech, aerospace and other high-tech fields. The main chain of polydimethylsiloxane elastomer is a repeated Si-O bond, and the side chain is an organic substituent group connected by Si-C bonds, so it has both organic and inorganic properties. Silicone rubber has excellent comprehensive properties, especially its excellent heat resistance, chemical inertness and aging resistance (ozone aging resistance, heat oxygen aging resistance, light aging resistance and weather aging resistance, etc.), and has irreplaceable application value in many extreme environments such as aerospace and national defense. However, the cross-linking bonds formed by the common silicone rubber vulcanization method (platinum-catalyzed addition crosslinking, peroxide crosslinking, condensation crosslinking, radiation crosslinking, etc.) are typical irreversible covalent bonds, so that once the silicone rubber is vulcanized and formed, it no longer has plasticity and reprocessing performance, so it is very difficult to recycle. In order to solve the recycling problem of silicone rubber, dynamic covalent bonds (covalent bonds that can be reversibly broken / bonded under external stimulation) cross-linking can be used to replace the traditional vulcanization method to obtain polysiloxane elastomers with thermoplastic / reprocessing properties. However, the stability of common dynamic covalent bonds is often difficult to compare with that of silicone rubber matrix, and it is easy to decompose or deteriorate under ultraviolet light or high temperature. Therefore, the heat resistance and aging resistance of the prepared dynamic silicone elastomer may be affected. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a recyclable polyurea-polydimethylsiloxane elastomer material and a preparation method thereof. In order to prepare a recyclable polysiloxane elastomer and at the same time reduce the effect of the introduction of dynamic bonds on the heat resistance of the silicone elastomer, the present invention first prepares a linear polyurea-polydimethylsiloxane long chain with a methoxy functional group, and then uses a dynamic silyl ether bond as a cross-linking bond of the elastomer curing network, so that the material has recycling performance. At the same time, the high bond energy of the silyl ether bond also enables the polydimethylsiloxane elastomer material to maintain excellent heat resistance. The thermal stability of the polyurea-polydimethylsiloxane elastomer is mainly measured by examining the change in its weight after heating for a certain period of time at a certain heating rate in a nitrogen atmosphere.

[0004] The technical purpose of the present invention is achieved through the following technical solutions:

[0005] A recyclable polyurea-polydimethylsiloxane elastomer material and a preparation method thereof, characterized in that the steps are as follows:

[0006] Step 1, reacting 100 parts by weight of silicone oil and 8-12 parts by weight of diisocyanate under an inert gas atmosphere and an ice-water bath, wherein the silicone oil is amino-terminated polydimethylsiloxane or hydroxy-terminated polydimethylsiloxane;

[0007] In step 1, stirring is selected for reaction, the stirring speed is 100-300 revolutions per minute, and the stirring time is 1-3 hours.

[0008] In step 1, the silicone oil is amino-terminated polydimethylsiloxane.

[0009] In step 1, the diisocyanate is one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate, preferably isophorone diisocyanate.

[0010] In step 1, the diisocyanate is used in an amount of 10-12 parts by weight.

[0011] Step 2, adding 6-8 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane to the substance obtained by the reaction in step 1, and reacting under heating at 40-80° C. to obtain an uncured raw material;

[0012] In step 2, 3-(2-aminoethylamino)propyldimethoxymethylsilane was added dropwise.

[0013] In step 2, the temperature is 60-80°C.

[0014] In step 2, stirring is selected to carry out the reaction, the stirring speed is 100-300 revolutions per minute, and the stirring time is 8-14 hours.

[0015] Step 3, adding 5-7 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine to the material prepared in step 2 and mixing well, and curing at 120-160° C. for 18-24 hours;

[0016] In step 3, stirring is selected for mixing, the stirring speed is 100-300 revolutions per minute, and the stirring time is 2-4 hours.

[0017] In step 3, curing is performed by heating in an oven at 140-160° C. for 20-24 hours.

[0018] Step 4, loading the rubber obtained in step 3 into a mold, hot pressing at a temperature of 160-180° C. and a pressure of 10-12 MPa for further crosslinking, and obtaining an elastomer film (i.e., the polyurea-polydimethylsiloxane elastomer material of the present invention) after natural cooling.

[0019] In step 4, the mold size is 100×100×2mm 3 .

[0020] In step 4, the hot pressing time is 10-15 minutes.

[0021] The technical solution of the present invention can be used to produce an elastomer with excellent mechanical properties. Dynamic silyl bonds are used as cross-linking bonds of the elastomer curing network, so that the material has recycling properties. At the same time, the high bond energy of the silyl bonds also enables the polydimethylsiloxane elastomer material to maintain excellent heat resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The infrared spectra of the raw materials isophorone diisocyanate, 3-(2-aminoethylamino)propyl dimethoxymethylsilane, aminopropyl-terminated polydimethylsiloxane and comparative example 1.

[0023] Figure 2 The infrared spectra of Example 1, Example 2, Example 3 and Comparative Example 1 are shown.

[0024] Figure 3 It is a swelling experiment diagram of Example 1, Example 2, Example 3 and Comparative Example 1 in tetrahydrofuran.

[0025] Figure 4 It is the stress-strain curve diagram of Example 1, Example 2, Example 3 and Comparative Example 1.

[0026] Figure 5 This is the stress-strain curve diagram of the original sample and the three-time recycled sample after three consecutive recyclings in Example 2.

[0027] Figure 6 It is the thermogravimetric curve diagram of Example 1, Example 2, Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0028] In order to better understand the present invention, the present invention is further described below in conjunction with the accompanying drawings and examples, but the embodiments of the present invention are not limited thereto. The main raw materials used are shown in the following table:

[0029]

[0030] The main equipment and instruments used are shown in the following table:

[0031]

[0032]

[0033] Example 1

[0034] Step 1, under an inert gas atmosphere, 100 parts by weight of aminopropyl-terminated polydimethylsiloxane is added to a three-necked flask, and then 10 parts by weight of isophorone diisocyanate is added under an ice-water bath, and stirred for 2 hours to allow the mixture to react fully;

[0035] Step 2, adding 7.5 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane, heating at 60° C. and stirring for 12 hours to prepare an uncured raw material;

[0036] Step 3, add 5 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and mix with the raw materials for 3 hours, pass through an electric vacuum drying oven at room temperature for 24 hours to remove tetrahydrofuran and heat. Pass through an electric blast drying oven at 140°C to cure for 20 hours;

[0037] Step 4, the rubber obtained in step 3 is loaded into a mold, and hot-pressed for 12 minutes at a temperature of 170° C. and a pressure of 11 MPa for further cross-linking, and an elastomeric film is obtained after cooling, which is recorded as PDMS-1.

[0038] Example 2

[0039] Step 1, under an inert gas atmosphere, 100 parts by weight of aminopropyl-terminated polydimethylsiloxane is added to a three-necked flask, and then 10 parts by weight of isophorone diisocyanate is added under an ice-water bath, and stirred for 2 hours to allow the mixture to react fully;

[0040] Step 2, adding 7.5 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane, heating at 60° C. and stirring for 12 hours to prepare an uncured raw material;

[0041] Step 3, add 6 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and mix with the raw materials for 3 hours, pass through an electric vacuum drying oven at room temperature for 24 hours to remove tetrahydrofuran and heat. Pass through an electric blast drying oven to cure at 140°C for 20 hours;

[0042] Step 4, the rubber obtained in step 3 is loaded into a mold, and hot-pressed for 12 minutes at a temperature of 170° C. and a pressure of 11 MPa for further cross-linking, and an elastomer film is obtained after cooling, which is recorded as PDMS-2.

[0043] Example 3

[0044] Step 1, under an inert gas atmosphere, 100 parts by weight of aminopropyl-terminated polydimethylsiloxane is added to a three-necked flask, and then 10 parts by weight of isophorone diisocyanate is added under an ice-water bath, and stirred for 2 hours to allow the mixture to react fully;

[0045] Step 2, adding 7.5 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane, heating at 60° C. and stirring for 12 hours to prepare an uncured raw material;

[0046] Step 3, add 7 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and mix with the raw materials for 3 hours, pass through an electric vacuum drying oven at room temperature for 24 hours to remove tetrahydrofuran and heat. Pass through an electric blast drying oven to cure at 140°C for 20 hours;

[0047] Step 4, the rubber obtained in step 3 is loaded into a mold, and hot-pressed for 12 minutes at a temperature of 170° C. and a pressure of 11 MPa for further cross-linking, and an elastomer film is obtained after cooling, which is recorded as PDMS-3.

[0048] According to the steps of Example 1, aminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate were selected without adding N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine crosslinking agent to prepare a control group 1 of polyurea-polydimethylsiloxane elastomer material, which was recorded as PDMSPU.

[0049] In the infrared spectrum of Comparative Example 1 (PDMSPU) ( Figure 1 ), 2240cm -1 The stretching vibration peak of the isocyanate group at 3344 cm -1 and 1564cm -1 New NH stretching and bending vibration absorption peaks appeared at 1629 cm -1 The absorption peak of the stretching vibration of amide C=O also appeared at . These changes indicate the polycondensation reaction of the amino group and the isocyanate group, thus verifying the successful preparation of Comparative Example 1. In the infrared spectra of Example 1, Example 2, Example 3 and Comparative Example 1 ( Figure 2 ), 1258cm -1 and 1006cm -1 The absorption peaks are due to the stretching vibrations of Si-CH3 and Si-O-Si, and the characteristic absorption peak of the silyl ether bond (Si-OC) should appear at 1074 cm -1 However, due to the overlap of the wide range vibration absorption peaks of Si-O in the PDMS skeleton, the characteristic absorption peaks of the silyl ether bond are not easy to be found. Therefore, the swelling experiments of Example 1, Example 2, Example 3 and Comparative Example 1 in tetrahydrofuran (THF) ( Figure 3 ) to further explore the cross-linking process. Comparative Example 1 completely dissolved in THF, while Example 1, Example 2, and Example 3 only slightly swelled and remained intact. This indicates that the linear PDMSPU forms a cross-linked structure, confirming the formation of silyl ether bonds in Example 1, Example 2, and Example 3.

[0050] The uniaxial stretching was carried out on a CMT4203 universal tensile testing machine produced by MTS of the United States, with a stretching rate of 20 mm / min. Figure 4The uniaxial tensile stress-strain curves of PDMSPU, PDMS-1, PDMS-2 and PDMS-3 prepared by the present invention show that the fracture strength of the prepared material gradually increases with the increase of the crosslinking agent content. Among them, PDMS-3 has a large amount of excessive crosslinking added, which hinders the formation of crosslinking points. Figure 5 The PDMS-2 prepared by the present invention and the stress-strain curve after recycling three times. The PDMS-2 prepared by the present invention was subjected to a mechanical property test, after which the sample was cut into pieces and then hot-pressed (160 degrees Celsius, hot pressing for 2 hours) to obtain a recycled sample, which was then subjected to a mechanical property test, and finally the same method was used to obtain a recycled secondary sample and a recycled thrice sample. The curve shows that after three consecutive recyclings, the prepared material has a breaking strength and elongation at break that are almost the same as those of the original material. The above data show that the formation of an appropriate amount of silyl ether bonds can improve the mechanical properties of the elastomer, and the silyl ether bonds with dynamic characteristics also give the elastomer good recycling performance.

[0051] The thermal stability of the samples was tested using a Netzsch STA449F3 thermogravimetric analyzer, mainly at 10 °C min -1 The thermal stability is measured by the change in weight after heating from 30°C to 800°C at a certain rate. The main indicators are the heating temperature when the mass loss is 5% (T5), the heating temperature when the mass loss is 10% (T 10 ).

[0052] Thermal stability (T5, T 10 ) are shown in the following table.

[0053] <![CDATA[T5(℃)]]> <![CDATA[T 10 (℃) <!-- 4 -->]]> Control group 1 291 316 Example 1 321 347 Example 2 324 351 Example 3 313 346

[0054] As can be seen from the above table, the PDMS-1, PDMS-2, and PDMS-3 with silyl ether bonds intersected with the PDMSPU without silyl ether bonds all had T5 that was 30°C, 33°C, and 22°C higher than the PDMSPU, and T10 that was 31°C, 35°C, and 30°C higher than the PDMSPU, indicating that the prepared material had good thermal stability. This shows that the PDMS-1, PDMS-2, and PDMS-3 with silyl ether bonds intersected with the PDMSPU without silyl ether bonds all had initial degradation temperatures that were about 30°C higher than the PDMSPU, indicating that the prepared material had good thermal stability. The effect of the present invention is quite significant. The addition of silyl ether bonds can significantly improve the thermal stability of the recyclable polydimethylsiloxane elastomer.

[0055] According to the content of the present invention, the process parameters can be adjusted to achieve the preparation of the material of the present invention, and the performance shown by the test is basically consistent with that of the embodiment. The above is an exemplary description of the present invention. It should be noted that any simple deformation, modification or equivalent replacement that can be made by other technicians in this field without spending creative labor falls within the protection scope of the present invention without departing from the core of the present invention.

Claims

1. A recyclable polyurea-polydimethylsiloxane elastomer material, characterized in that: To use dynamic silyl bonds as crosslinks in the cured elastomer network, follow these steps: Step 1, reacting 100 parts by weight of silicone oil and 8-12 parts by weight of diisocyanate under an inert gas atmosphere and an ice-water bath, wherein the silicone oil is amino-terminated polydimethylsiloxane or hydroxy-terminated polydimethylsiloxane; Step 2, adding 6-8 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane to the substance obtained by the reaction in step 1, and reacting under heating at 40-80° C. to obtain an uncured raw material; Step 3, adding 5-7 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine to the material prepared in step 2 and mixing well, and curing at 120-160° C. for 18-24 hours; Step 4, the rubber obtained in step 3 is loaded into a mold, hot-pressed at a temperature of 160-180° C. and a pressure of 10-12 MPa for further cross-linking, and then naturally cooled to obtain an elastomer film.

2. The recyclable polyurea-polydimethylsiloxane elastomer material according to claim 1, characterized in that: In step 1, stirring is selected for reaction, the stirring speed is 100-300 revolutions per minute, and the stirring time is 1-3 hours; the silicone oil is amino-terminated polydimethylsiloxane; the diisocyanate is one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate, and the amount of diisocyanate is 10-12 parts by weight.

3. The recyclable polyurea-polydimethylsiloxane elastomer material according to claim 1, characterized in that: In step 2, 3-(2-aminoethylamino)propyldimethoxymethylsilane is added dropwise; the temperature is 60-80° C.; stirring is selected to react, the stirring speed is 100-300 revolutions per minute, and the stirring time is 8-14 hours.

4. The recyclable polyurea-polydimethylsiloxane elastomer material according to claim 1, characterized in that: In step 3, stirring is selected for mixing, the stirring speed is 100-300 revolutions per minute, and the stirring time is 2-4 hours; curing is performed by heating in an oven at 140-160° C. for 20-24 hours.

5. The recyclable polyurea-polydimethylsiloxane elastomer material according to claim 1, characterized in that: In step 4, the mold size is 100×100×2mm 3 , hot pressing time is 10-15min.

6. A method for preparing a recyclable polyurea-polydimethylsiloxane elastomer material, characterized in that: Follow the steps below: Step 1, reacting 100 parts by weight of silicone oil and 8-12 parts by weight of diisocyanate under an inert gas atmosphere and an ice-water bath, wherein the silicone oil is amino-terminated polydimethylsiloxane or hydroxy-terminated polydimethylsiloxane; Step 2, adding 6-8 parts by weight of 3-(2-aminoethylamino)propyldimethoxymethylsilane to the substance obtained by the reaction in step 1, and reacting under heating at 40-80° C. to obtain an uncured raw material; Step 3, adding 5-7 parts by weight of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine to the material prepared in step 2 and mixing well, and curing at 120-160° C. for 18-24 hours; Step 4, the rubber obtained in step 3 is loaded into a mold, hot-pressed at a temperature of 160-180° C. and a pressure of 10-12 MPa for further cross-linking, and then naturally cooled to obtain an elastomer film.

7. The method for preparing a recyclable polyurea-polydimethylsiloxane elastomer material according to claim 6, characterized in that: In step 1, stirring is selected for reaction, the stirring speed is 100-300 revolutions per minute, and the stirring time is 1-3 hours; the silicone oil is amino-terminated polydimethylsiloxane; the diisocyanate is one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate, and the amount of diisocyanate is 10-12 parts by weight.

8. The method for preparing a recyclable polyurea-polydimethylsiloxane elastomer material according to claim 6, characterized in that: In step 2, 3-(2-aminoethylamino)propyldimethoxymethylsilane is added dropwise; the temperature is 60-80° C.; stirring is selected to react, the stirring speed is 100-300 revolutions per minute, and the stirring time is 8-14 hours.

9. The method for preparing a recyclable polyurea-polydimethylsiloxane elastomer material according to claim 6, characterized in that: In step 3, stirring is selected for mixing, the stirring speed is 100-300 revolutions per minute, and the stirring time is 2-4 hours; curing is performed by heating in an oven at 140-160° C. for 20-24 hours.

10. The method for preparing a recyclable polyurea-polydimethylsiloxane elastomer material according to claim 6, characterized in that: In step 4, the mold size is 100×100×2mm 3 , hot pressing time is 10-15min.

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