CN114989622A - A kind of isocyanate/silk fibroin composite film and preparation method thereof - Google Patents

Abstract

The invention discloses an isocyanate/silk fibroin composite film and a preparation method thereof, which comprises the steps of boiling mulberry silkworm cocoons by alkaline deionized water for degumming, dissolving by a calcium chloride/ethanol/deionized water system, dialyzing and concentrating to prepare silk fibroin aqueous solution; uniformly mixing hexamethylene diisocyanate trimer with the silk fibroin aqueous solution to obtain isocyanate/silk fibroin mixed aqueous solution; and then the mixed aqueous solution is transferred to a silica gel mold by adopting a solution casting method to prepare the isocyanate/silk fibroin composite film, so that the isocyanate/silk fibroin composite film has the characteristics of high light transmittance, good thermal stability, excellent tensile strength, good toughness after being dried in water, excellent repeated bending performance and the like, the technical problem of poor mechanical property of the existing silk fibroin film is solved, the defects that the silk fibroin film is fragile and fragile after being dried in water are overcome, and the isocyanate/silk fibroin composite film is expected to be used as a flexible substrate material to meet the application requirements of high mechanical property, humidity and other complex environments.

Description

A kind of isocyanate/silk fibroin composite film and preparation method thereof

technical field

The invention belongs to the field of preparation of composite films, in particular to an isocyanate/silk fibroin composite film and a preparation method thereof.

Background technique

As an environmentally friendly biomass material, mulberry silk is a structural protein continuous long fiber formed by silkworms during silk spinning. It has the characteristics of wide source, low cost, excellent processability and sustainable development and utilization. In recent years, by selecting an appropriate salt solution system, a single form of mulberry silk can be prepared into a silk fibroin aqueous solution, and then processed to form silk fibroin nanofibers, composite membranes, hydrogels and aerogels. A variety of morphological structures meet the application needs of different fields. Among them, silk fibroin film has the characteristics of simple and efficient preparation process and large-scale production, and has shown huge market application prospects in the field of flexible substrate materials. Compared with traditional polymer composite materials as substrates, there are disadvantages such as non-renewable resources, difficult biodegradation, and easy accumulation of waste. Silk fibroin films have a series of unique advantages such as sustainable development and green environmental protection. However, in the current process of reprocessing mulberry silk, the original structure of mulberry silk is often destroyed, resulting in the deterioration of the mechanical properties of the prepared silk fibroin film, and it is difficult to meet its practical application requirements in multiple fields and high performance. In addition, the silk fibroin film has the disadvantage of being brittle after drying in contact with water in complex environments such as humidity, which further limits its practical application. Therefore, how to further improve the mechanical properties of silk fibroin thin film materials and improve the disadvantages of drying and brittleness after encountering water are technical problems that need to be overcome urgently.

To sum up, silk fibroin film has the characteristics of simple and efficient preparation process, large-scale production, sustainable development and green environmental protection, showing huge market development and application prospects. However, the silk fibroin film prepared by the silk fibroin aqueous solution currently has disadvantages such as deterioration of mechanical properties and brittleness after drying in contact with water, which greatly hinders its practical application and is a technical problem that is difficult to overcome at present.

SUMMARY OF THE INVENTION

In view of the shortcomings of the above-mentioned prior art, the first object of the present invention is to provide a kind of isocyanate/silk fibroin composite film;

The second object of the present invention is to provide a preparation method of an isocyanate/silk fibroin composite film.

To achieve the above object, the present invention provides a method for synthesizing pantolactone, comprising the steps:

An isocyanate/silk fibroin composite film, in parts by weight, the raw material composition of the composite film includes: 0.3-0.9 parts of isocyanate and 9.1-9.7 parts of silk fibroin.

Further, the raw material composition of the composite film includes: 0.7 parts of isocyanate and 9.3 parts of silk fibroin, the thickness of the composite film is 13.8 μm, and the maximum tensile strength is 38.2 MPa.

Further, the isocyanate is hexamethylene diisocyanate trimer, and its molecular weight is 168.19.

Further, the specific steps are as follows:

1) the silkworm cocoons are boiled and degummed in alkaline deionized water, dissolved in a calcium chloride/ethanol/deionized water system, dialyzed and concentrated to obtain a silk fibroin aqueous solution;

2) adding hexamethylene diisocyanate trimer dropwise to the silk fibroin aqueous solution in step 1), and uniformly stirring in a water bath to obtain an isocyanate/silk fibroin mixed aqueous solution;

3) After ultrasonically dispersing the isocyanate/silk fibroin mixed aqueous solution in step 2), transfer it to a silica gel mold by a "solution casting" method, and prepare an isocyanate/silk fibroin composite film in a constant temperature drying oven.

Further, the specific steps of obtaining the silk fibroin aqueous solution described in step 1) are as follows:

Alkaline deionized water boiling and degumming: take 15-20 parts of silkworm cocoons and add them to an aqueous sodium carbonate solution with a concentration of 2-4wt% and a liquor ratio of 1:50; 30min and replace the sodium carbonate aqueous solution 3-4 times, further wash with deionized water at room temperature and place it in a constant temperature drying oven at 50°C for 12-24h to obtain degummed silkworm cocoons;

Dissolution in calcium chloride/ethanol/deionized water system: put the degummed silkworm cocoons in a calcium chloride/ethanol/deionized water system with a molar ratio of 1:2:8, in a constant temperature water bath at 50-70°C Stir for 1.5-3h to obtain silk fibroin/calcium chloride/ethanol/deionized water solution, then transfer it to a centrifuge tube, centrifuge for 10-20min in a centrifuge with a rotating speed of 6000-12000r/min, and collect the supernatant to beaker;

Dialysis and concentration: transfer the supernatant to a dialysis bag with a molecular weight cut-off of 8000-14000Da, dialyze it in deionized water for 4-6 days, and then transfer it to a polyethylene glycol aqueous solution with a concentration of 10-20wt% for reaction. Dialyzed for 1-3h to obtain silk fibroin aqueous solution.

Further, boiling and degumming with alkaline deionized water: 15 parts of silkworm cocoons, the concentration of sodium carbonate aqueous solution is 2wt%, the boiling and degumming time is 4 times, the boiling and degumming time is 20min, the temperature of the constant temperature drying box is 50°C, and the drying time is 18h;

The calcium chloride/ethanol/deionized water system is dissolved: the temperature of the constant temperature water bath is 60℃, the stirring time is 2h, the speed of the centrifuge is 8000r/min, and the centrifugation time is 15min;

Dialysis and concentration: the dialysis time was 6 days, the polyethylene glycol aqueous solution concentration was 15wt%, and the reverse dialysis time was 2h.

Further, the specific steps of obtaining the isocyanate/silk fibroin mixed aqueous solution described in step 2) are as follows:

0.3-0.9 parts of hexamethylene diisocyanate trimer was added dropwise to 9.7-9.1 parts of silk fibroin aqueous solution with a concentration of 2.5-5.5 wt% using a glue tip dropper, hexamethylene diisocyanate tri- The mass ratio of the polymer to the silk fibroin is 3-9 wt % respectively, and then the mixture is stirred for 0.5-2 h in a constant temperature water bath at 30-50° C.

Further, the hexamethylene diisocyanate trimer is 0.7 parts, the silk fibroin is 9.3 parts, the concentration of the silk fibroin aqueous solution is 4.5 wt %, and the hexamethylene diisocyanate trimer and the silk fibroin are 0.7 parts. The mass ratio is 7wt%, the temperature of the constant temperature water bath is 30°C, and the stirring time is 1h.

Further, the specific steps of preparing the isocyanate/silk fibroin composite film described in step 3) are as follows:

After ultrasonically dispersing the mixed aqueous solution of isocyanate/silk fibroin for 0.5-1 h at a power of 100W, transfer 1.10-2.30 parts of the mixed aqueous solution to a 3cm×5cm silica gel mold, and then place it at 50-80°C Drying in a constant temperature drying oven for 12-24 hours can form a transparent film at the bottom of the mold, that is, an isocyanate/silk fibroin composite film.

Further, the ultrasonic power is 100W, the ultrasonic dispersion time is 0.5h, the isocyanate/silk fibroin mixed aqueous solution is 1.70 parts, the temperature of the constant temperature drying oven is 70°C, and the drying time is 12h.

Adopt above scheme, the present invention has following beneficial effect:

1. The present invention discloses a preparation method of an isocyanate/silk fibroin composite film, which solves the technical problem of insufficient mechanical properties of traditional silk fibroin film materials. The calcium chloride/ethanol/deionized water system is dissolved, dialyzed and concentrated to prepare a silk fibroin aqueous solution; the isocyanate (hexamethylene diisocyanate trimer) is uniformly mixed with the silk fibroin aqueous solution to obtain an isocyanate/silk fibroin mixture Aqueous solution; then the isocyanate/silk fibroin mixed aqueous solution was transferred to a silica gel mold by the "solution casting" method to prepare an isocyanate/silk fibroin composite film with a thickness of 13.8 μm, a light transmittance of 95.8%, and a thermal decomposition temperature of 282.4 ℃, the maximum tensile strength is 38.2Mpa, and the invention has the advantages of simple steps, easy operation, simplicity, low cost and large-scale production.

2. Compared with the pure silk fibroin film, the tensile strength of the isocyanate/silk fibroin composite film prepared by the present invention is increased by about 205.6%, which effectively improves the existing technology of deteriorating the mechanical properties of silk fibroin film materials. Therefore, the preparation of silk fibroin high-strength composite film material was realized, which can meet the practical application requirements of high mechanical properties as a flexible substrate material.

3. The present invention solves the technical problem that the traditional silk fibroin film material is brittle after drying in contact with water. The present invention adopts the technical scheme of compounding isocyanate (hexamethylene diisocyanate trimer) and silk fibroin, and combines isocyanate (hexamethylene diisocyanate trimer) with silk fibroin. Methylene diisocyanate trimer) and silk fibroin aqueous solution were uniformly mixed and prepared into isocyanate/silk fibroin composite film by "solution casting" method. The isocyanate/silk fibroin composite film showed toughness after drying in water. It is expected to be used as a flexible base material to meet application requirements in complex environments such as humidity. The present invention solves the technical problem that the existing silk fibroin film is brittle after drying in water, and further expands its use and field of application.

Other advantages, objects, and features of the present invention will be set forth in the description that follows, and will be apparent to those skilled in the art based on a study of the following, to the extent that is taught in the practice of the present invention.

Description of drawings

Fig. 1 is the preparation process of the isocyanate/silk fibroin composite film of the present invention.

Figure 2 is the surface morphology of the isocyanate/silk fibroin composite film of the present invention.

Figure 3 is the cross-sectional morphology and thickness of the isocyanate/silk fibroin composite film of the present invention.

Figure 4 shows the light transmittance and thermal stability of the isocyanate/silk fibroin composite film and silk fibroin film of the present invention.

Figure 5 shows the mechanical properties of the isocyanate/silk fibroin composite film and the silk fibroin film of the present invention.

FIG. 6 is a comparison diagram of the isocyanate/silk fibroin composite film of the present invention and the silk fibroin film immersed in deionized water.

FIG. 7 is a comparison diagram of the bending test after the isocyanate/silk fibroin composite film of the present invention and the silk fibroin film are immersed in deionized water and dried.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment involved in the present invention are conventional reagents and methods in the technical field. and equipment.

Example 1: Preparation of isocyanate/silk fibroin composite film

The preparation process is shown in Figure 1;

Product 1: The specific steps are as follows:

1) the silkworm cocoons are boiled and degummed in alkaline deionized water, dissolved in a calcium chloride/ethanol/deionized water system, dialyzed and concentrated to prepare a silk fibroin aqueous solution;

Alkaline deionized water boiling and degumming: take 15 parts of silkworm cocoons and add them to an aqueous sodium carbonate solution with a concentration of 2wt% and a liquor ratio of 1:50; Replace the sodium carbonate aqueous solution and boil and degumming for 20min); further wash with deionized water at room temperature and place it in a constant temperature drying oven at 50 ° C and dry for 18h to obtain degummed silkworm cocoons;

Dissolving in calcium chloride/ethanol/deionized water system: put the above degummed silkworm cocoons in a calcium chloride/ethanol/deionized water system (molar ratio of 1:2:8), in a constant temperature water bath at 60°C Stir for 2h to obtain silk fibroin/calcium chloride/ethanol/deionized water solution; then, transfer it to a centrifuge test tube, centrifuge it in a centrifuge with a rotational speed of 8000r/min for 15min, and collect the supernatant into a beaker;

Dialysis and concentration: the above supernatant was transferred to a dialysis bag with a molecular weight cut-off of 8000-14000 Da, and dialyzed in deionized water for 6 days; then, it was transferred to a polyethylene glycol aqueous solution with a concentration of 15wt% for reverse dialysis for 2h , to obtain a silk fibroin aqueous solution;

2) After preparing the silk fibroin aqueous solution in step 1) to a concentration of 4.5 wt %, uniformly stirring for 1 hour in a constant temperature water bath at 30° C. to further obtain a silk fibroin aqueous solution;

3) After ultrasonically dispersing the silk fibroin aqueous solution in step 2), transfer it to a silica gel mold by a "solution casting" method, and prepare a silk fibroin film in a constant temperature drying oven;

After ultrasonically dispersing the silk fibroin aqueous solution for 0.5 h at a power of 100 W, 1.6 parts of the silk fibroin aqueous solution were transferred to a 3cm×5cm silica gel mold; then, placed in a constant temperature drying box at 70°C After drying for 12 hours, a transparent film, namely silk fibroin film, can be formed at the bottom of the mold.

Product 2: The specific steps are as follows:

1) the silkworm cocoons are boiled and degummed in alkaline deionized water, dissolved in a calcium chloride/ethanol/deionized water system, dialyzed and concentrated to prepare a silk fibroin aqueous solution;

Alkaline deionized water boiling and degumming: take 15 parts of silkworm cocoons and add them to an aqueous sodium carbonate solution with a concentration of 2wt% and a liquor ratio of 1:50; Replace the sodium carbonate aqueous solution and boil and degumming for 20min); further wash with deionized water at room temperature and place it in a constant temperature drying oven at 50 ° C and dry for 18h to obtain degummed silkworm cocoons;

Dissolving in calcium chloride/ethanol/deionized water system: put the above degummed silkworm cocoons in a calcium chloride/ethanol/deionized water system (molar ratio of 1:2:8), in a constant temperature water bath at 60°C Stir for 2h to obtain silk fibroin/calcium chloride/ethanol/deionized water solution; then, transfer it to a centrifuge test tube, centrifuge it in a centrifuge with a rotational speed of 8000r/min for 15min, and collect the supernatant into a beaker;

Dialysis and concentration: the above supernatant was transferred to a dialysis bag with a molecular weight cut-off of 8000-14000 Da, and dialyzed in deionized water for 6 days; then, it was transferred to a polyethylene glycol aqueous solution with a concentration of 15wt% for reverse dialysis for 2h , to obtain a silk fibroin aqueous solution;

2) adding isocyanate (hexamethylene diisocyanate trimer) dropwise to the silk fibroin aqueous solution in step 1), and uniformly stirring in a water bath to obtain an isocyanate/silk fibroin mixed aqueous solution;

0.7 parts of isocyanate (hexamethylene diisocyanate trimer) was added dropwise to the aqueous solution containing 9.3 parts of silk fibroin using a glue tip dropper, and the concentration of the silk fibroin aqueous solution was 4.5 wt %, isocyanate ( The mass ratio of hexamethylene diisocyanate trimer) to silk fibroin is 7wt%; then, uniformly stir for 1h in a constant temperature water bath at 30°C;

3) after ultrasonically dispersing the isocyanate/silk fibroin mixed aqueous solution in step 2), transfer it to a silica gel mold by a "solution casting" method, and prepare an isocyanate/silk fibroin composite film in a constant temperature drying oven;

After ultrasonically dispersing the mixed aqueous solution of isocyanate/silk fibroin for 0.5 h under the condition of 100W power, 1.6 parts of the mixed aqueous solution of isocyanate/silk fibroin was transferred to a 3cm×5cm silica gel mold; then, it was placed at 70°C After drying for 12h in a constant temperature drying oven, a transparent film, ie isocyanate/silk fibroin composite film, can be formed on the bottom of the mold.

Product 3: The specific steps are as follows:

1) the silkworm cocoons are boiled and degummed in alkaline deionized water, dissolved in a calcium chloride/ethanol/deionized water system, dialyzed and concentrated to prepare a silk fibroin aqueous solution;

Alkaline deionized water boiling and degumming: take 20 parts of silkworm cocoons and add them to a sodium carbonate aqueous solution with a concentration of 4wt% and a liquor ratio of 1:50; Replace the sodium carbonate aqueous solution and boil and degumming for 30min); further fully wash with deionized water at room temperature and place it in a constant temperature drying oven at 50 ° C and dry for 12h to obtain degummed silkworm cocoons;

Dissolving in calcium chloride/ethanol/deionized water system: put the above degummed silkworm cocoons in a calcium chloride/ethanol/deionized water system (molar ratio of 1:2:8), in a constant temperature water bath at 50°C Stir for 3h to obtain silk fibroin/calcium chloride/ethanol/deionized water solution; then, transfer it to a centrifuge test tube, centrifuge it in a centrifuge with a rotating speed of 6000r/min for 20min, and collect the supernatant into a beaker;

Dialysis and concentration: the above supernatant was transferred to a dialysis bag with a molecular weight cut-off of 8000-14000 Da, and dialyzed in deionized water for 4 days; then, transferred to a polyethylene glycol aqueous solution with a concentration of 10wt% for reverse dialysis for 3h , to obtain a silk fibroin aqueous solution;

2) adding isocyanate (hexamethylene diisocyanate trimer) dropwise to the silk fibroin aqueous solution in step 1), and uniformly stirring in a water bath to obtain an isocyanate/silk fibroin mixed aqueous solution;

0.9 parts of isocyanate (hexamethylene diisocyanate trimer) was added dropwise to the aqueous solution containing 9.1 parts of silk fibroin using a glue tip dropper, and the concentrations of the aqueous solution of silk fibroin were 4.5 wt%, isocyanate The mass ratio of (hexamethylene diisocyanate trimer) to silk fibroin is 9wt%; then, uniformly stir in a constant temperature water bath at 50°C for 2h;

3) after ultrasonically dispersing the isocyanate/silk fibroin mixed aqueous solution in step 2), transfer it to a silica gel mold by a "solution casting" method, and prepare an isocyanate/silk fibroin composite film in a constant temperature drying oven;

After ultrasonically dispersing the mixed aqueous solution of isocyanate/silk fibroin for 1 hour under the condition of power of 100W, 2.3 parts of the mixed aqueous solution of isocyanate/silk fibroin were transferred to a 3cm×5cm silica gel mold; then, placed at 80°C After drying for 18h in a constant temperature drying oven, a transparent film, that is, an isocyanate/silk fibroin composite film, can be formed on the bottom of the mold.

Example 2: Surface morphology, cross-sectional morphology, size and mechanical properties of isocyanate/silk fibroin composite film

1. Experimental materials

The silk fibroin film, the isocyanate/silk fibroin composite film, and the pure silk fibroin film prepared under the conditions of product 2 in Example 1 were used.

2. Experimental method

2.1 Surface morphology, cross-sectional morphology and size

It was carried out at 25 °C, and the surface morphology, cross-sectional morphology observation and cross-sectional size measurement of the isocyanate/silk fibroin composite film were carried out using a Feiner China scanning electron microscope.

2.2 Mechanical property test

It was carried out under the conditions of 25 °C, an initial clamping distance of 1 cm, a stretching rate of 10 mm/min, and the sample size of the isocyanate/silk fibroin composite film and the pure silk fibroin film were both 3 cm × 1 cm. AGS-XShimadzu universal material tensile testing machine;

The elongation at break (ε _τ , %) is calculated according to the following formula:

ε _τ - elongation at break (%);

L ₀ —Initial clamping distance (mm);

L—clamping distance when the sample breaks (mm);

The tensile strength (δ _τ , MPa) is calculated according to the following formula:

δ _τ —tensile strength (MPa);

F—fracture stress (N);

b—sample width (mm);

d—sample thickness (mm).

3. Experimental results

It can be seen from Figure 2 and Figure 3 that the isocyanate/silk fibroin composite film is colorless and transparent, its surface morphology is smooth and dense, the cross-sectional structure is slightly rough, and the thickness is 13.8 μm;

It can be seen from Figure 4a that in the wavelength range of 300-800 nm, the light transmittance of the isocyanate/silk fibroin composite film is as high as 95.8%; The thermal decomposition temperature of the /silk fibroin composite film is about 282.4°C, a significant increase of 38°C;

It can be seen from Figure 5 that the maximum tensile strength of pure silk fibroin film is about 12.5Mpa, while the maximum tensile strength of isocyanate/silk fibroin composite film is about 38.2MPa, which is greatly increased by 205.6%, showing excellent tensile strength. tensile strength.

Example 3: Comparative experiment of isocyanate/silk fibroin composite film and silk fibroin film immersed in deionized water and the bending performance test after drying

1. Experimental materials

The silk fibroin film, the isocyanate/silk fibroin composite film, and the pure silk fibroin film prepared under the conditions of product 2 in Example 1 were used.

2. Experimental method

2.1 Immersion in deionized water

At 25°C, both the pure silk fibroin film and the isocyanate/silk fibroin composite film cut into appropriate sizes were immersed in 25 mL of deionized water, and the macroscopic differences between the two were observed and recorded.

2.2 Bending performance test

Both the pure silk fibroin film and the isocyanate/silk fibroin composite film immersed in the deionized water test in 2.1 above were immersed in 25 mL of deionized water for 0.5 h, and then dried in a constant temperature drying oven at 70 °C for 12 h; then , The pure silk fibroin film after drying and the isocyanate/silk fibroin composite film were respectively tested for repeated bending performance with white plastic tweezers.

3. Experimental results

It can be seen from Figure 6 that the pure silk fibroin film will curl when immersed in deionized water, but the isocyanate/silk fibroin composite film will not curl when immersed in deionized water;

It can be seen from Figure 7 that after being immersed in deionized water and dried, the pure silk fibroin film is brittle, brittle, and has no bending properties. However, the isocyanate/silk fibroin composite film still maintains high strength and good toughness. Features, with repeated bending performance;

To sum up, the isocyanate/silk fibroin composite film prepared by the present invention effectively solves the technical problem of poor mechanical properties of the existing silk fibroin film, and improves the brittleness and brittleness of the existing silk fibroin film after drying in contact with water. Due to the lack of properties, it is expected to be used as a flexible substrate material to meet the application requirements in complex environments such as high mechanical properties and humidity.

Finally, it should be noted that the above is only the preferred embodiments of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the The technical solutions described in the foregoing embodiments may be modified, or some of the technical features thereof may be equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. An isocyanate/silk fibroin composite film, characterized in that, in parts by weight, the composite film raw material is composed of: 0.3-0.9 part of isocyanate and 9.1-9.7 part of silk fibroin. 2. a kind of isocyanate/silk fibroin composite film according to claim 1, is characterized in that, described composite film raw material composition comprises: 0.7 parts of isocyanate, 9.3 parts of silk fibroin, the thickness of described composite film is 13.8 parts μm, the maximum tensile strength is 38.2MPa. 3 . The isocyanate/silk fibroin composite film according to claim 2 , wherein the isocyanate is a hexamethylene diisocyanate trimer with a molecular weight of 168.19. 4 . 4. the preparation method of a kind of isocyanate/silk fibroin composite film according to claim 3, is characterized in that, concrete steps are as follows: 1) the silkworm cocoons are boiled and degummed in alkaline deionized water, dissolved in a calcium chloride/ethanol/deionized water system, dialyzed and concentrated to obtain a silk fibroin aqueous solution; 2) adding hexamethylene diisocyanate trimer dropwise to the silk fibroin aqueous solution in step 1), and uniformly stirring in a water bath to obtain an isocyanate/silk fibroin mixed aqueous solution; 3) After ultrasonically dispersing the isocyanate/silk fibroin mixed aqueous solution in step 2), transfer it to a silica gel mold by a "solution casting" method, and prepare an isocyanate/silk fibroin composite film in a constant temperature drying oven. 5. the preparation method of a kind of isocyanate/silk fibroin composite film according to claim 4, is characterized in that, the concrete steps that obtain silk fibroin aqueous solution described in step 1) are as follows: Alkaline deionized water boiling and degumming: take 15-20 parts of silkworm cocoons and add them to an aqueous sodium carbonate solution with a concentration of 2-4wt% and a liquor ratio of 1:50; 30min and replace the sodium carbonate aqueous solution 3-4 times, further wash with deionized water at room temperature and place it in a constant temperature drying oven at 50°C for 12-24h to obtain degummed silkworm cocoons; Dissolution in calcium chloride/ethanol/deionized water system: put the degummed silkworm cocoons in a calcium chloride/ethanol/deionized water system with a molar ratio of 1:2:8, in a constant temperature water bath at 50-70°C Stir for 1.5-3h to obtain silk fibroin/calcium chloride/ethanol/deionized water solution, then transfer it to a centrifuge tube, centrifuge for 10-20min in a centrifuge with a rotating speed of 6000-12000r/min, and collect the supernatant to beaker; Dialysis and concentration: transfer the supernatant to a dialysis bag with a molecular weight cut-off of 8000-14000Da, dialyze it in deionized water for 4-6 days, and then transfer it to a polyethylene glycol aqueous solution with a concentration of 10-20wt% for reaction. Dialyzed for 1-3h to obtain silk fibroin aqueous solution. 6. the preparation method of a kind of isocyanate/silk fibroin composite film according to claim 5, it is characterised in that alkaline deionized water boiling degumming: 15 parts of silkworm cocoons, sodium carbonate aqueous solution concentration is 2wt%, boiling degumming 4 parts Second, the boiling degumming time is 20min, the temperature of the constant temperature drying oven is 50℃, and the drying time is 18h; The calcium chloride/ethanol/deionized water system is dissolved: the temperature of the constant temperature water bath is 60℃, the stirring time is 2h, the speed of the centrifuge is 8000r/min, and the centrifugation time is 15min; Dialysis and concentration: the dialysis time was 6 days, the polyethylene glycol aqueous solution concentration was 15wt%, and the reverse dialysis time was 2h. 7. the preparation method of a kind of isocyanate/silk fibroin composite film according to claim 4, is characterized in that, the concrete steps that obtain isocyanate/silk fibroin mixed aqueous solution described in step 2) are as follows: 0.3-0.9 parts of hexamethylene diisocyanate trimer was added dropwise to 9.7-9.1 parts of silk fibroin aqueous solution with a concentration of 2.5-5.5 wt% using a glue tip dropper, hexamethylene diisocyanate tri- The mass ratio of the polymer to the silk fibroin is 3-9 wt % respectively, and then the mixture is stirred for 0.5-2 h in a constant temperature water bath at 30-50° C. 8. the preparation method of a kind of isocyanate/silk fibroin composite film according to claim 7, is characterized in that, described hexamethylene diisocyanate trimer is 0.7 part, silk fibroin is 9.3 parts, silk fibroin The concentration of the protein aqueous solution was 4.5wt%, the mass ratio of hexamethylene diisocyanate trimer to silk fibroin was 7wt%, the temperature of the constant temperature water bath was 30°C, and the stirring time was 1h. 9. the preparation method of a kind of isocyanate/silk fibroin composite film according to claim 4, is characterized in that, the concrete steps of preparing isocyanate/silk fibroin composite film described in step 3) are as follows: After ultrasonically dispersing the mixed aqueous solution of isocyanate/silk fibroin for 0.5-1 h at a power of 100W, transfer 1.10-2.30 parts of the mixed aqueous solution to a 3cm×5cm silica gel mold, and then place it at 50-80°C Drying in a constant temperature drying oven for 12-24 hours can form a transparent film at the bottom of the mold, that is, an isocyanate/silk fibroin composite film. 10. The preparation method of a kind of isocyanate/silk fibroin composite film according to claim 9, wherein the ultrasonic power is 100W, the ultrasonic dispersion time is 0.5h, and the isocyanate/silk fibroin mixed aqueous solution is 1.70 parts , The temperature of the constant temperature drying oven is 70℃, and the drying time is 12h.

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